ieee ths : gate ras oene : t ers tilts ete erbocin amish aye : : seats st enneshenettleseaangeney fi omy iy sete trast ENN eget oSeedtinieeess rae ANNUAL REPORT ie OF THE UNITED STATES (ROLOGICAL AND GEOGRAPHICAL SURVEY Ee SEES en OUR MESS COLORADO AND PARTS OF ADJACENT TERRITORIES ; BEING A REPORT OF PROGRESS OF THE DXPLORATION POR TWH YEAR 1874. A BY F. V. HAYDEN, UNITED STATES GEOLOGIST. CONDUCTED UNDER THE AUTHORITY OF THE SECRETARY OF THE INTERIOR. er ON NS -7 CY riehtois a ere ¥ S2tec To Te PE HD pe pera IG wee ea EL wie Bde awClitORIChs BWilotul, WASHINGTON: GOVERNMENT PRINTING OFFICE. 1376. CONTENTS. PEP TER LOE EC OE CRE DAR Yi cate ie oe tarare lara te eieioi neta tololslaieimatais ovata ators aie a ftte ala en mtu unui GEOLOGY, MINERALOGY, AND MINING INDUSTRY. REporT OF F. V. HAYDEN, United States geologist ....-. ......2..--.---------- Chapter I. Brief history of the Lignitic group, first studied on the Upper Missouri—early views entertained by Meek, Newberry, and other paleon- tologists on the age of this group—the Lignitic group of the North- west believed to be continuous southward with the Colorado and Lara- TWN NE 265 dodo cena dena césode Hoos bdGouE does obadeu HoBdo6baHS soddeq Chapter II. The Lignitic group as examined at Cation City—Colorado Springs—northward to Cache 4 la Poudre Creek—Monument Creek group—probable age of these groups. .----. ---- ws .-c2 cane cee ces weno ne Appendibxato Chapter, by Hote WeSUsese tna ese celnnmeisasela ees Chapter III. Résumé of the geology along the eastern base of the Front or Colorado range: Silurian, Carboniferous, Triassic, Jurassic, and Creta- CEOUS CLOUDS So 4 esle= lee eeienie = BiObad poco OsoESO dogo goKeHe boeboadoas he Carboniferous veToOUpyseei ae eels neil ite ae erate ola eee aeinete ie are ee Khe Red bedsionUriassic SvOuUp eee acess eto seleeieeel een coe ANI URES co5654 S555 dees Dod Ces EaTe Ban BOO Sedans 5 ace SoUHOH oS bobeaE INDG CHOCO TE ces6 ass456 cose boosocds cobode dese Sood Hes Gad Sod ded bods Chapter IY. Ancient lake-basins—Glacial lakes—Morainal deposits in the valley of the Upper Arkansas River and along both flanks of the Sa- WiRbCRUMOUNAING)-ciyecrccisojepeecloramicnlaisine letela amine aye ale wel enya geiar pan at Saami Chapter VY. General view of the geography and geology of the Elk Mount- ains—eruptive granites—rhyolites and dikes—erosion ona grand scale— Tocaltdaritt=d@pOsits ies) ie cols ces iaya leis aerials reat ata as ert eee Sie Chapter VI. Report on the Geology of the Northwestern portion of the Elk EAN COMM yap le ELOUM CS ise car epscle ciceiicisminyacnmice nase erie ene sale aa ae ole LEECH Were apd DS oysl a Kyo Key ay ae eee a ee PNA et a A EO al i hepRoaringhOrkisyNChnal sins epicice eases canescens eeicee ee ies Geology of Sopris ealsandavicinityy sass scietssiesielsne sesacreeereeie eee Geology of the district drained by Rock Creek............------.----- The-great fault-fold of the Blk range. ...20-5.2-cccecesencls-- ses snee Report oF A. C. PEALE, M. D., geologist of middle division --..........-..---- ESLLCERLOPD Eaten V ope AY GeNpeaalate cist, oceieivie siaparoeleaieeiaae ee EN a PTILTOAUC ELON fae ae sone lafe aa cts Soa e Se a) dale sisets Satelnie a Seals sie euisreataenlaeeene Chapter I. Surface geology—valley of Eagle River ...-.-......----..----- Chapter II. Surface geology—Grand River and its tributaries.............. Chapter Iil. Surface geology—Gunnison River and its tributaries.-........ Chapter [V. Archean areas of Hagle, Grand, and Gunnison Rivers...-.-.. Chapter V. Stratigraphy—Paleozoic formations. ...........-----.---0- enc Silurian Cee eemnec ne Melsicisajac a acin rec aie feleinieial stew ciaeenieeia Maria cere nqnete Primordial PeLiod— PLopsdamycroup es. sea eee ae aeeeeee eee ene ees Canadian period—Calciferous and Quebec groups..-...-.--..---.--- ReMaAinider Of olUrianisc cc veren meats clase noe cles siswisceresaeicieeee BD reso y oa eke yeas ie a a ae Poe I Carboniferous BOC cere o nyo yneetersisiepe fates sea ecw Eee ae aie c Permianvorberinio-Canboniterous-cseyee once sein ae wacice eee onelece 4 ESET ESS 1S eit moe etree at er ea ee eo Be SINT Nhe RY Ge Ee EU nt Lower Cretaceous—Dakota group (No. 1)...-...--.------------- ---- Middle Cretaceous) (No:32 and. NOoS)22-ssece nee elec oeene sen oeceeens Middig, Cretaceous (NO; 4) psc nsc secon ccce cect ae see oss Seceaeoees WP PEIOrehACeOUs es Fase ee ai ele Se epee al alee eat a ea ate a rae 19 IV TABLE OF CONTENTS. Report or A. C. Peatx, M. D.—Continued. RE RE Chapter VII. Stratigraphy—Cenozoic formations... ..---2---. eeeeweeeneee Merhialyy 2.22 - be sec wee cece snes ee ace anism = sie ctelesie= PepSod caceee Fort Union ‘or Great Lignite| group. -- ee oe oos cca ie ao lela cinta ee Bear RiVeL STOMP! cj cinlecieeeclee mms e='= ein le) sini wlnin/elatalalntelaloieiotaleniaetetseetata Bitter Creel (Series cee wales iol slew sie | ereiele) siatnel ela eiate since ieee eerie Wasatch group..-- -2-- ---- -----+ w--- wenn Sono Koen cone nobbhe so6s00 Green River Qroup ...--- 02-2 onan ee cone comm ee coc ene ce Bodo ds66 coon Wind River group... -- eee. ---- ~~~ oe wees weenie wee wne cone = cence BLA CL/OTOUP 2 << einen eine =s)=\=elsinin|i iain emleinln elelelal wininle/slsa\=sia(=lee miataeyeieiete WihiteyRiver/oroup)e ssjces clwiceelsjairieenlenielecieioe sie acinititne elon setae Ibe no ea Ko) BS Geas So eee Secon EOS Good suooobeade Hboeea cach eoocas Tertiary between Grand and Gunnison Rivers ...--....--..-----.---- Green River and Bridger groups --...---22 we-ece eee n ee oe none eens Post Mertiary and recent. 522 secctiiec otee secise sc seibicseee oes aeee Chapter VIII. Eruptive rocks—trachytes—trachorheites—basalt......-.--.- Rorphyritie trachy test coos cpsisce eccscecoo sess cise coca c= cmcieenc eee PrAChOrhenbesiee center aaelemmslasises aieaam ese seinaeeisiscciocineite cette S BASIC NALCRS seo cinje = cjeeicienie merece esiencne ssa alecieeiaaicis oan ee ete ae eee Chapter IX. Economical geology ..--2.- 2220. c2- 222 eee ne cee ene Reece Catalornesof mineralg: 20 lee ee eee Catalogue Of TOCKS)< << coon casemeiiae scelctoeisee sas cs cece) seeeee ce eee PORT OF SE aM. ENDEICH, (S.No ace cece soeecclenis apace areneme cee os meee Letter to Dr. F. V. Hayden ...-...--...---..-. Seas See Ses cu pan UnMtroduchon se 552 cicc o cleceiwe cman enwlelocct scellswcieielenc tn lamlctata netomat sere ; Chapter I. Metamorphic area ..--...----- .----+ 2-222 cece e cone ee ee eee eee Chapter Ll.) Volcaniclarea tc cos ee cies clotie sic clase eel ales famvajaer eee Chapter TIL. Sedimentary, area. ooo. oe ose cc citae cowie me isemep ccies lose Silurian cceseccee secs sceose sewclecbislescincs nemo soe ancien Seen MDE VONIAN ES Cele ceeccle eeclsleineeies celiac siesicinieveteele a mea ye oe aseta = aoe Garboniferouss2 25. vocis ecco ce cscs jonas cetacwies ce aselscmise ee astaaee : Cretaceous 6 - coon cccrensiee cis cores eee nine eee tena taeretinre ee arch eee Cretaceous (NO. i) as eset eiccseinnlels = elec eine sents et asic moriniae slap uees Cretaceous: (No. 2) ce ccna ce Meee erela resale ieee cater aye re cee Chapter TW.) Mines) o.oo ceieeee aye seenscmisics suse Nala leery are eiieetelsateeee Occurrence of lodesye Fes se es ee are Ct iain ie Aad aul Spee Honan eMaryic ss ewisc seinem els scinie sacle msictoncaiasiae ateiee teenies cetera ihe Robert Bruce cr. -/ppccjsiec easement loca eeeewnicecte Sasi eerie ses ‘The iComstock lodes ise ee cy eee eae a cha eae aU aa Phe, Yreteva) <4 eseiesaecee Satisie Oleremiete tie nimtespteie le cithneiayees 2a repeat epuee Green, Mountainlode o.oo. Soc ete ae eciateiciinne Selceieeic eiee nara aes The-Rrospector. 220.222 ona SEEPS eRPA Pak Bey E Er eiapene gn aU ayy nae eS rear NaN FS. ThetPelican- lode x52 oo ees es SS as ae Spee a ee BioiCasing. . o's. ook oe Wie ceice ie ate te eae ee ee ete ns SIS eee erate CL ae sire ea se a Pe A omacd Conclusion oo) oe cc ie al SIE) SUN eee Oa a ct PORTION SAMUEL AUGHEY,, Ph. Disco os oe eae ae a See eee Theisuperficial deposits of Nebraskas ooo: 2222 Se sisccciee oaes ones eee ABO VD TE Mes eee eee ey ale See ae ROSE eer BEE a SRR a nerscic (Phe TZoess: deposits .o.occeic Leis tay he a UE ee ea eee ae Mrmit.on the ioess deposits 2205 joo Nu ee eae Se eet Scenery, of the Loess deposits)... 42. s sees ee eee eae eee Onisin of the: Wacustrine) deposits-.25-c2e/casseee eee ae eee Heneth. of)ithe Loessiage. 22. 2225602 a Sa a i Patera ae Ale ae ee Lifeof the Loessjage yee a. ois esc oe ocean eee ene see cele neiaos PERU TOE Sita 40 ey oe PEN i I Rn aie rs ey ee a npr IE ee he sand hillece ss Se ele ls ey ah NRT Ost pe ee Alailamde iss eu Sls ala NVR A eA Euel from, the surface-deposits..-. 0.020052 20 oe ee Water=resources of) Nebraska) 222. 25) 2 ee eee een ae Limber in modern geological times... .2. J Joa eee Pi Mollusks in the Lacustrine deposits..)_..0.-.2.-sgnc5seeeeeeeeeeneees TABLE OF CONTENTS. PALEONTOLOGY. SECON LO MESGUEREUX. soe a ee eM Lg ETL AELARELE UTD 18 IG nga RSet gs AE eC ee ea a On the Tertiary flora of the North American Lignitic, considered as evi- dencelor the ace of the formation aoc. ce yn a In sialon ee Table of subdivisions of the Tertiary of Europe, according to the floras Table exposing the relation of the fossil plants of Point of Rocks.--. Description of species of fossil plants from Point of Rocks....-....--- New species of Tertiary fossil plants briefly described.........-....- A review of the Cretaceous flora of North America............-..----- Nps General remanken sees ei ee ey Nes USS Gnas Meee MON OU § 2. Description and enumeration of generic and specific divisions... ARCHAOLOGY. REPORRION DRNEST INGERSO LEY ciscsee cee aisi os lee ee aye oes wlcdeiole ai cae pau alas Watural@histony,e1Svacs yaaa Noise Nei Satisfy UU UH ta i Ui Te APD an Better 0; Dr.-B V5 Haydenss-sesac veces seclesee Fe ee oe SN ei Hist Ofsocalities Of SPECIMENS Saale — saa sre eee c \Seee oa oe retels Aarne sea te Generavaccount ofthe werk. oo ajo -biay-1 sce jee e oe Seneca ee Ee SOO Reve Specialsreport on the Molluscas sas. 25 cos eke cise ccs those ey ae oe omens : HM ISHOR AMUN OLIbeESy scot oa soso see ae fein a cee Sore ares Sete ae ee ais TOPOGRAPHY AND GEOGRAPHY. Reports of Henry Gannett, S. B. Ladd, and A. D. Wilson. BEPOR TON EEN RY, GANNETT, Mil Bic a ssce soscecticccee sede cons casein nea Intro dneLOLVleiteren 2 a. sc cise sas sec ass ec se eee ae eee ema meee Be OIE J ees Specs pase COU Bocas SOOO EA AOO CAG Hem PAC Nee Ser ii mI OR Gs Previous explorabions im the districts saan sessed sosccie nee cemecceccemeoes Geosrap ly, Of phe disthichieeae-s pace se eee ease ee een noe cee ete Height of the walls of the Grand Canon of the Gunnison.---...----.-. Disiributionyof veretatione sss across cee vals stienc ase ease oe ne eet Hettlements, trails) Toads Webesaocias secs sae ee eee ee acne eeiee Shaper, Blevatlons! sis. 07 5 soos oes oe eaten sie Nema ee Revision of the heights of summits in the Sawatch and Elk systems... - PikoMounsainss 225. ssssc se coe as Bes eee ie ae, Ongthrenp lates seer Sa reine lar niails iain) weet aerial q neta neta a7 etal OY REPORT OFS. B. LADD, M. E:, northern division... 2... -..-2.,2222 23-20 cs25e- CHEE RUODDED Bey Vi day (OM: sco oeiniciec cnc anciays nsec mye aeeieisersele tee ere VE POLUF ose ood oa essai ae oe cites oiciols x ea sccicels) sme an a a ee ee ee Se aS fRoadsand: trails. sao 5-22 ono os heeeiecteies oes Scene ne ye Ce ty WN maaan WistOt ClovaulOnS> 222 -)5 Sse e See sce cemoe cic indmise cline c hae neice apieitae eons EPO E OKLA DI NVTLSON -poclssecsec wate see ee hee sees ee a a ani Means of communication between Denver and the San Juan mines...-- cee Comparisons of anercids with the mercurial barometer..--..---.-----.---- EE ORT ORED RANICELN| DWHOD Acct e see sty ie scale ie aye cremate ap ers maker a camel cuits Roportapuyor the San sm@an cOumimyys ee oe ce ool cee See Ae teas ane PERCeT DL. OL MOUNT LSTELEIS) = tay ee tee cere sees iii cele ae Me aS Ge ON RE Ms as Methods used in determining the elevation of points in the district..---.-- Notes useful for the location of miners’ monuments in Baker’s Park...----. SOLS TLSEA 159 11.9 9 Daca i elec a Me el ee i Secchi nee peeetts SES TTG AG COS Ie 9 20). a te ee ee tele el a se Re ea BOER CRORE OBES oo dase LIST OF NEW SPECIES DESCRIBED. FOSSIL PLANTS. UPMCMRB ELSIE DUE tes 12 232 i= cara di cin!'a Sais woe cme once oe eS uae Paha eaeala Lk Lt SCMMAGERSL CU BL CAML AA ea oats Cal CLEC eraser oclaleisieine elatala\yaine el oeiaias ae simatoieisieinisisiieie ciate = Fig. 1. Table Butte, capped with trachyte ....-....-....-..... Se Eater nig. Deposit of lignite in an irregular cavity in sandstone .. ; a Arla teellepMionumentiearks © oloradoans inc ceeeee ence soles sae eicereceee 36 5. Geological map of Colorado Springs and vicinity....-...-- PO ae Ney ANE AG 6. Sections accompanying map of Colorado Springs and vicinity -----.-.------ 40 7. Preliminary map of eastern base of Rocky Mountains ..---..-.--.---..-.. AL a Sy Fig. 1. Needle Rock in Glen Eyrie, Triassic sandstone -....-.---. S EUR Iv.} Fig. 2. Concretions of sandstones, Cretaceous Periodweeee cae a : cs + § His. 1. Showing changes in sediments_----. 22.52 222: 22220222 g= Elsie V. ; Fig. 2. Thickening of sedimentary beds near Manitou.-....--. el Fig. 1. Cross-bedding, Lignitic sandstones, near Colorado Springs 10. Plate VI.< Fig. 2. Silurian limestones resting unconformably on stratified 44 : eranibe,swWilliamis: Canoe ese seein ceeicceimeicicere il. Plate VII. Surface-section near Glen Eyrie, Colorado .-..----.----.--.----- 42 12. Plate VIII. Gateway to the Garden of the Gods ...--...----..------------- 42 i3- late Exe Cathedralinock, Gardenof the Gods’. 2.3.22. 2 2558 822 soe 43 eel easariigearicn trom GE SOU Se pee ee eee) eras Buyin nara iN vba ili ra I UE ena 44 15. Plate X. Foliation of granite in Estes Park, Colorado .-..-.-.-....-------- 46 16. Plate XI. Long’s Peak and Estes Park, Colorado .s---.-...--..---..------- 46 17 Sketch and sections showing the moraines of the Upper Arkansas Valley 48 Tit: COORD + coe ee5 toda calc boas poosoGusaaou dadebensoeesrodsce GS6uK5 foeworainesiof phe Upper Arkamsases rem estacce ni aeletohe ee lmnteto ata al etal yet ate ale 49 19> Plate Xt) Boulder ‘Canon; Colorado; sranite)-. oso eee ce. 50 etl aroex aa OC hicacoraake:iColoradomee ietecwiciceciion cine setoe seas cele eects ate 52 21. Plate XVI. A portion of the east face of Gothic Mountain --..--..---.---.- 54 22. Plate XV. Mountain of the Holy Cross, Colorado ..-...........---..----- 54 REPORT OF W. H. HOLMES. 23. Fig. 1. Sections across the synclinal valley of Roaring Fork -.--.---...--.. 60 4 ice aC hartio li soprishhea kannst ece eee eric celimacie natant oes 62 53 iso uNechion across ithe: SOPLIsSUpliit wees =e seem eee See ae eeeee 2a igs sketch looking, down Rock Creek nic secant elon selcie cicisie eal Sate 63 POO GEOlOC sO RSUALLON Doe erecrer ae eine el teste rianciaet mines eeiale eiciclelonerateeile see 64 21. Fig. 6. View in-the Snow Mass group --....-..--------2-- -- tsholer wae Wen 65 Bem N/ jo PECASULYS MOUNtAIDS seine aia\ sae ne) os teehee es cowie uiccines aaltstnas 66 Pe GO. C asCaAges, Ol HOC: Crela. sea he me -nise et ceise sence sciclaniace as cane 67 30. Fig. 9. Relations of the coal-beds to No. 1 Cretaceous. -.....---.---..------ 69 dl, Fig. 10. Sections across fault-fold of Elk Mountains..-.--..-..- 32. Fig. 11. Part of the great fault-fold of Elk Mountains..--.. } Between aD easel 3. Map of the Elk Mountains, Colorado .----/--..--..--.------ nee 34, Sections accompanying map of Elk Mountains --...-..----.. } Between U2 Gi Oe RepvortT oF A. C. PEALE. BU MOHCC MOH COMVEN ONAL SIGNS) en eee ae asia ae oe em ea ae 76 § Fig. 1. Section A. South from Eagle River....-... ---- booade 36. Piate I. Fig. 2. Section B. Across Eagle River to Holy Cross Mount- | 80 CI 7 RS shes i SLR en LUAU A Se SPE ALCrUL, EO] MgOn EE ACI pRUV ELI ao tetas ere eho enclose clave a ren LUELLA 82 Fig. 1. Section C. Across Eagle River to station 9.......-.- 38. Plate ll. » his, 2, Section D. Eagle River to station 9 ...-.-..-..0-.-- ; es 39. Map A. Showing lines of section on Eagle River..--....---..------------- 84 ioe sectioned, -Across/GrandWRiver= sess. escenels sees Ae ais IA. Fig. 2. Section F. From station 13 to station 14-.......---. : ee APPEAL ep biision bE lateau Creek soe iie ee er Oa ae 91 A2. Plate VI. Bluff on Grand River near the mouth of the Gunnison.-.......-.. 92 2 Fig. 1. Section G. From station 38 to Gunnison River -.----- és, Plate VII. Fig. 2. Section H. From station 77 to Cedar Creek -.-.--.--. ; oe 44. Map B. “ Showing lines of section across Gunnison River -.--...---.------ 100 Fig. 1. Section I. From Gunnison River westward ...-...---- . Plate Vitt.2 Fis: 2: Section K. Across the Gunnison below North Fork -- . 102 J \ Fig. 3. Section L. Across angle of Gunnison below the Grand L CATO m pais ene ee ee ae eee ee eae ele Moneaieieat J Vill TABLE OF CONTENTS. Facing page— Fig. 1. Section across monoclinal fold south of Grand River. 46. Plate IX. < Fig. 2. Section across monoclinal fold west of Gunnison River Fig. 3. Section M. From Gunnison River east to mesa ...... 47. Plate X. Bluff at head of Oh-be- joyful Creeks os). cc etc 2 nee 48.\Plate XT, Bluit on Coal Creek... ene ce new oe eel eee eee 49, Plate XII. Dikes in sandstone on Anthracite Creek...........-...----.---6 50. Plate XIII. Dikes in bluff at head of Ob-be-joyful Creek............- ee 51. Map C. Showing areas of porphyritic trachyte........---...---. Pe i ae f ae i } 52. Plate XIV. ae ig 3 2, Sections across Gunnison River above Grand Cafion.. rie ri . Map D. Showing areas of trachorheites and lines of sections across the Gun- nison River Ee Saas ainy ae Aled) eat NIM UME ICIS I OG . Map E. Showing basaltic areas between Grand and Gunnison Rivers and line of section NBS BRB oa os GOES Us Ou Sebs Seer scBe ees so6 cocoons se0c Reeone oF EF. M. ENDLICH. 55. Fig. 1. Monuments near camp 23, east of station 10.......-........-. ..---- 56. Fig. OY Taizard’s ead iene ue oe oS haere re rave a) oa een 57. Section I. From station 48 through stationj49 os fe ee eee 58. Section II. From station 31 toward Sultan Mountain........---..----...... 59)) Section IM. Through statiomas.2 - 22 oe ey asin een sale nicinine sin seinj aeiceerseeie GON Section WVWie a ees FERRE TOS AB HOIN a bobo GOES GOCE ME BEON Base BEON OSS oo GHVSection VeeAt station 40 ino ie sie slam al eye navelelnlainininnieisislefeinicloreisieieietaiceinienciseie 62/Section VE Through station 47s cio. s oa) alcatel) nlaic winicl aie ena et Go Section VA oo ee ese erage lara ia) nia tararsteiota) svaialaitaiajarae ye etVaesel eve ors tot essai cba Arete te GAS SechiomsyValU wee eee elses tnalaereie eters (Pistetctt alm aie ace a/al vere iota lata ed aaa 65. Fig. 3. Metalliferous veins near Howardville, Colo i REPORT OF SAMUEL AUGHEY. 66. Arrows found in the Loess (wood-cut in text) .....-..---c-...--.-. Ps Rerort or LEO LESQUEREUX. : S Fig. 1) Aralia: tripartiba 22 tances; also southward to| § 1,23 very large leaves of true fan palms. Also, | 6 Fort Clarke; seen under the | 8 | 5s Helix, Melania, Vivipara, Corbicula, Unio, Os-| & White River group,ou North | gas trea, Potamomya, and scales of Lepidotus, with | = Platte River, “above Fort Lar- | ER bones of Tiionyx, Emys, Compsemys, Crocodi- | S& amie; also on west side of = lus, ete. a Wind River Mountains. ‘‘The Fort Union, or Great Lignite group, occupies extensive areas of country in Nebraska, and has been seen beneath the White River group at several distant localities. It was evidently deposited in large bodies of water, which were at first brackish, and then gradually became fresh. “The great number of fossil leaves, and numerous beds of lignite con- tained in it, clearly show that the shores of these ancient estuaries, lakes, etc.,in which this formation was deposited, supported dense forests of large trees, and a growth of other vegetation, far exceeding in luxuriance anything now met with in these latitudes. ‘Indeed, the presence of true fan palms, of large size, and the remains of the genus Crocodilus, as well as the affinities of the Mollusca found in these beds to southern forms, all point rather to the existence here of a tropical than a temperate climate during their deposition. In regard to the relations of this formation to known horizons in the Tertiary of _the Old World, we scarcely feel prepared to express a very decided opinion. “The difficulty in the way of drawing inferences bearing on this point from the remains of Mollusca found in these beds is that they, being fresh and brackish water types, bear little or no analogy to those of the 24 GEOLOGICAL SURVEY OF THE TERRITORIES. Tertiary of the States bordering on the Atlantic, nor are any of them, so far as known, specifically identical with foreign forms. ‘¢ When we bear in mind, however, the fact, that wherever this forma- tion has been seen in contact with the latest Cretaceous beds, the two have been found to be conformable, however great the upheavals and distortions may be, while at the junction there seems to be a complete mingling of sediments, one is strongly impressed with the probability that no important member of either system is wanting between them. This view is also rendered more probable by the fact that the formation under consideration is known to hold a position beneath the White River group, which is characterized by the remains of an entirely different fauna, clearly of Miocene age. ‘s Again, the occurrence in this lower group of remains of the genus Lepidotus, which is, we believe, in Europe unknown above the Eocene, while the other vertebrate remains found associated with it have been compared by the distinguished comparative anatomist, Professor Leidy, with types. even older than the Tertiary, are facts strengthening the impression that this Fort Union Lignite group probably repre- sents the Eocene of Europe. “Tt should not be forgotten, however, that an extensive and beautiful ' series of fossil plants from this formation, although not yet thoroughly investigated, have been thought by Dr. Newberry to be most analogous to Miocene types. ; ‘““Yet even if this formation should prove to be of Eocene age, this would only be in accordance with what is now known in regard to the earlier introduction of particular types of plants in the Cretaceous sys- tem of this country than in that of the Old World. ‘¢ As the Wind River deposits have not yet been seen in contact with any well-marked beds of the other Tertiary formations of this region,. and few fossils have yet been found in them, their position in the series remains doubtful. It is, therefore, only provisionally that we bave placed this formation between the Fort Union and White River groups in the foregoing section. It may possibly belong to the horizons of one of these rocks, or even represent them both in part, or, what is more probable, it may oceupy an intermediate chronological position. ‘The only fossils yet foundin this formation are fragments of Trionyx and Vestudo, together with the shells of two species of Helix and a cast of a Vivipara. One of these Helices is more like H. Leidyi from the White River group than any of the other species yet known from any of these rocks, while the other is a very large depressed species of southern type, quite unlike any of those hitherto found in any of the other Nebraska rocks. The Vivipara seems to be indistinguishable from our V. trochiformis from the Fort Benton group, though, as it is a mere cast, it cannot be identified with certainty with that Shell. No marine or brackish-water fossils have been found in these beds. The White River group is the formation that has furnished the extensive and interesting collections of Vertebrate remains which have been so ably investigated by Professor Leidy. It occupies a consider- able area in’ the region of White River, and is seen beneath the succeed- ing formation on the Niobrara and Platte Rivers. Its position above — the Fort Union or Great Lignite group has also been clearly and satis- factorily determined. | “This formation is mainly composed of a series of whitish, indurated clays, which have been worn and cut, by the streams, rains, and other atmospheric agencies, into numerous deep valleys and ravines, so as to leave various peaks, isolated columns, towers, etc., presenting, as seen HAYDEN.) GEOLOGY—WHITE RIVER GROUP. 25 from a Gistance, exactly the appearance of the ruins of an ancient city. The difficulty the traveler meets with in finding his way through this interminable Jabyrinth caused the Indians to eall it, in their own language, the Bad Grounds; hence the French name, Mauvaises terres, applied by the Canadian voyageurs in the employ of the fur-companies. “The vertebrate remains found in these beds belong to the genera Oreodon, Agriocharus, Pebrotherium, Leptomeryx, Leptanchenia, Pro- tomeryx, Merycodos, Titanotherium, Leptocherus, Hyracodon, Entelo- don, Paleocherus, Rhinoceros, Steneofiber, Machairodos, Anchitherium, Hyopotamus, Hycenodon, Ischyromys, Palewolagus, Ewmys, Testudo, ete., etc. The affinities of these fossils, as has been shown by Professor Leidy, clearly establish the Miocene age of this formation. F Comparatively few invertebrate remains have yet been found in the White River group. They consist of ene species of Helix, one or two of Timnea, a small Physa, two or three small species of Planorbis, ete. No fossil leaves nor beds of lignite have been met with in it, and all the animal remains, as may be seen from the foregoing list, are terrestrial and fresh-water types. The Loup River beds consist mainly of incoher- ent materials, and were evidently deposited after the upper surface of the White River group had been worn into ravines and other depressions. It occupies much of the surface of the country in the region of the Loup Fork and Platte River, and extends far south of the latter stream. ‘*The vertebrate remains from it described by Professor Leidy belong to the genera Megalomeryx, Procamelus, Cervus, Rhinoceros, Mastodon, Llephas, Hipparion, Merychippus, Equus, Castor, Felis, Canis, Testudo, eic., many of which are very closely allied to recent species. A fewshells of the genera Helix, Physa, etc., apparently identical with living spe- cies, have also been found in these beds. All the species of vertebrate and other remains yet found in them are distinct from those eceurring in the White River group and beds below, and they have not yet atiorded any brackish or marine types of any kind. ‘* When we take into consideration the position of this formation above the well-marked Miocene White River group, and the relation of its organic remains to Pliocene and recent species, there is little room for doubting the correctness of its reference to the horizon of the Pliocene of Europe. ‘* The extracts which I have given are sufficient to show the opinions of a most excellent paleontologist in regard to the age of this group as interpreted from the invertebrate fossils.” Let us for a moment glance at the testimony of American vegetable paleontolozists. Without quoting again, I will simply refer the reader to the interesting report of Dr. J. S. Newberry on the Cretaceous and Tertiary plants collected by me during the expedition to the Yellowstone and Missouri Rivers, during the years 1859 and 1860, a portion of which was reprinted in the Annual Report of Wyoming, 1870, commencing at page 94. It will be seen that Dr. Newberry regarded these fossil plants as uot only of Tertiary age, but Middle Tertiary, or Miocene. In an in- teresting memoir published in the Annals of the Lyceum of Natural History, in 1867, Dr. Newberry remarks: ** By far the largest representation of our Tertiary flora is, however, contained in collections made by Dr. Hayden on the Upper Missouri, ot which the greater number of species are described in the present mem- oir. These plants are from the lignites proved by the associated fossils to be of the Miocene age. They were collected at various points on the Missouri River, at Fort Clarke, at Red Spring, thirteen miles above, at Fort Berthold, at Crow Hills, one hundred miles below Fort Union, at 26 GEOLOGICAL SURVEY OF THE TERRITORIES. the mouth of the Yellowstone, on O’Fallon’s Creek, one hundred miles above the mouth of the Yellowstone, and in the valley of that stream. ‘““The explorations of Dr. Hayden prove that this Miocene Lignite for- mation occupies the beds of extensive lakes, which formed basins on the surface of the continent when it had but recently emerged from the’ Cretaceous sea. As has been remarked elsewhere, the lower members of the series contain a few estuary shells, showing the access of salt- water at that period; but during the deposition of by far the greater portion of these beds, the water of the ocean was entirely excluded from the basins in which they accumulated. There is, therefore, every reason to believe that the débris of ligneous plants which compose this collec- tion were derived from trees which grew along the shores of the lakes and streams of the Tertiary continent; that then, as now, alternations of seasons prevailed, by which th foliage of these trees were detached by an autumnal frost, and that falling into the water beneath or near them, and sinking to the bottom, they were enveloped in mud, precisely as leaves of our sycamores, willows, oaks, etc., accumulate at the bottoms of our streams and lakes of the present day.” I need.not extend these remarks tarther to illustrate the views of both paleontologists in regard to the age of the Lignitie group, as observed in the Northwest, up to within a comparatively recent period. 1 need not refer to the views of Mr. Lesquereux, inasmuch as they have been consistent in the belief of their Tertiary age, from the commence- ment of his examination up to the present time, and his arguments in favor of this belief have been set forth in nearly all the annual reports of the Survey. If the Lignitic group, as developed on the Upper Missouri, is admit- ted to be either entirely or in part of Tertiary age, the question will arise, what bearing has this admission on the age of the coal-beds of Wyo- ming and Colorado ? I beg just here to call the attention of geologists to the geological maps prepared by me, and published in the Final Report of Nebraska, 1869, and in the Geological Report of the Exploration of the Yellowstone and Missouri Rivers, 1859~60, especially the latter map. It will be seen by the last-named map that the Lignitic group oceupies a very large area along the Upper Missouri and the Yellowstone Rivers, that it extends far north into the British possessions. We may then trace it south- ward in a broad continuous belt across the Yellowstone River, between the Black Hills and the Big Horn Mountains, until it is overlapped by the White River group, about sixty miles north of Fort Laramie. If we continue southward along the east base of the Laramie range, we find that the Lignitic group re-appears about ten miles south of the Union Pacitic Railroad. We find that where the White River group and the Lignitic group come in contact, the former is superimposed on the latter, and that really the White River group formed a vast basin Subsequent to the existence of the great lake in which the lignitic sediments were deposited.. We find also, by examining the White River group along the base of .the mountains, that the Laramie range formed a barrier that prevented it from extending into the Laramie Plains; but the evidence is clear that, at the time of the existence of the great Lignitic lake or sea, this barrier did not prevent the water- communication with the Laramie Plains. Indeed, the evidence seems quite clear that, with the exception perhaps of some isolated peaks ris- ing above the waters, there was no mountain-barrier where we. now have the Laramie range. Therefore, with the exception of the Bear River and Coalville group, we may connect the coal-bearing beds of the HAYDEN.) GEOLOGY—COAL STRATA. Tee Laramie Plains and Colorado with the vast group in the Northwest. I have traced this geographical connection step by step over this great area, have studied the tormation with some care, and collected both vegetable and animal fossils in the greatest abundance from point to point. I would say, however, that comparatively few of the fresh-water species of Mollusea, so abundant in the Northwest, are found either in Colorado or the Laramie Plains; but it possesses the same character, and many of the same species of plants are scattered all over this im- mense area. CHAPTER IL. THE LIGNITIC GROUP AS EXAMINED AT CANON CITY—COLORADO SPRINGS—NORTHWARD TO CACHE LA PUUDRE CREEK—MONUMENT CREEK GROUP—-PROBABLE AGE OF THESE GROUPS. Our examinations along the eastern base of the mountains in Colorado were directed mainly to the tr&ting-out of the connection between the Lignitic group and the older beds. We traced the boundary of this group, with great care, from Caton City, on the Arkansas River, north- ward nearly to Cheyenne. It is hardly possible that any links in the chain of evidence escaped us, and the principal differences of opinion now will consist in the degree of importance to be attached to that evi- dence. The question is whether the coal-bearing strata known as the Lignitic group of the Eastern Rocky Mountain region is of Cretaceous or Tertiary age. In this chapter, we shall simply record our field-cbser- vations, referring the reader to a subsequent chapter for a brief discus- sion of the question of age. South of Caiion City, on the south side of the Arkansas River, there is an isolated coal-basin occupying an area of about fifty square miles. The strata lie for the most part in a nearly horizontal position, indicating no great disturbance, except along the north and west sides. On the north- west side of the basin, along the immediate base of the mountains, the beds have been lifted up, so that a great thickness of the Lignitic sandstones is exposed, at least 1,000 to 1,600 feet. The Cretaceous beds are also seen lying close to the flanks of the mountains. As we proceed southward along the junction of sedimentary beds and the granites, the Cretaceous beds disappear, and one by one the lower Lignitic, until the whole mass juts against the granitic rocks, with no perceptible evidence of disturbance, except in a general way. There seems to be a rapid slope from the base of the mountains to the Arkansas River, a dis- tance of about five miles, thus giving to the strata a general dip of about 5°. So far as we could ascertain, there are no coal-beds ip the northern portion of the basin. The rocks consist mostly of rath- er thick beds of gray, brown, and yellow sandstone, with loose clays and sands between, but no coal-beds. We find that the coal-bear- ing portion does not oveupy the entire area, and that a large part is classed as barren coal-measures. The most important coal-mine has been opened on the east side of the basin, about midway, on Oak Creek. This is one of the most important coal-mines in the Territory. It was described briefly, but quite clearly, in the Annual Report of the Survey for 1869, and since that time in the more elaborate reports of Mr. Les- quereux. In the summer of 1872, Mr. Lesquereux made a careful examination of the coal-formations ail along the east base of the Rocky Mountains from Cheyenne to Santa Fé. His report in the Annual Re- port for 1872 is quite exhaustive. The section of the coal-strata on page 323, nade by Mr. Neilson Clark, the superintendent of the mines, is more accurate than any other that has been made of the group, and need not be repeated here. Itremains now to consider the beds below this sec- 28 HAYDEN. ] GEOLOGY—LIGNITIC GROUP IN COLORADO. 29 ion, which are supposed to be of Cretaceous age, but which might very properly be called beds of passage from well-marked Cretaceous strata to those containing coal and vegetable remains. We have heretofore de- scribed the Upper Cretaceous beds as of strictly marine origin; that tie sediments were deposited in a broad and, at least, moderately deep sea. As long as we find that these physical conditions prevailed, we observea greater or less abundance of fossils of strictly marine forms, as Ammon- dies, Baculites, Lnoceramus, etc.; but even when no break can be found in the sequence of the beds, indicating a lapse of time in the deposition of the sediments, we discover that the physical conditions gradually change until there is a complete extinction of all marine forms of life. We find here on the Arkansas River a full development of the Upper Cretaceous formations Nos. 4and 5, with their peculiar fossils. We also observe that the materials of the upper portion of No. 5 pass gradually from a dark- yellow clay to a rusty-yellow sand, and above this, 200 to 300 feet, of a sort of irregular thin layers of mud-like material, with curious concre- tions of sandstone. In this group of strata, which may be called transi- tional, not a fossil has yet been found to prove the age beyond a doubt. Resting on this irregular group of mud-strata is a bed of sandstone of very variable thickness as well as structure. Sometimes it is not more than 50 feet thick, and then again it is 300 to 400 feet thick. It is full of rounded concretionary masses, and shows very clearly that its sedi- ments were deposited in shallow and very turbulent waters. This sand- stone passes up into clay, and on this clay rests a bed of coal. In the bed of sandstone below the coal, the peculiar vegetation of the Lignitic group is found in considerable abundance, and, therefore, this may mark the lowest horizon of this group. Now, whenever, in any part of the country, invertebrate remains of any kind are found above this bed of sandstone, they are invariably brackish or fresh water in their charac- ter; and whenever any of these fossil shells are observed below this sand- stone, they are always strictly marine. We have in the vicinity of these coal-mines the details of structure, which we have briefly described above, most clearly shown. Now the question arises, what stress shall be laid on these remarkable physical changes? Would not this form an excellent line of separation between two great periods in geological time? Are not these changes sufficient to indicate clearly that these are probably the beds of passage or transition between the Cretaceous ° and the Tertiary epochs? We find also a complete change in the vege- table as well as animal life. We are not aware that any of the verte- brate remains, which have been regarded by Cope and Marsh as proving the Lignitic group to be of Cretaceous age, have ever been found mingled with any other forms of life of strictly marine origin. So far, all the vertebrate fossils have been discovered iu the Lignitic group. It seems therefore that not a single species of vegetable or animal life survived the physical changes which were introduced during the time of the depo- sition of the transition group. Now, if we have shown this state of affairs in regard to the Cafion group, we may connect this group easily with the Raton Hills group to the southward, and the Monument Creek group far to the northward near Colorado Springs. In passing northward, we see no more of the Lignitic group, so far as we have examined, until we reach Colorado Springs, a distance of thirty miles in a straight line. Here it is exposed in the torm of an irregular bloff ridge, ranning down from the base of the mountains a little south- east, beyond the limit of our explorations up to this time. In section 2, we see in the foreground, at either end, the form of the sandstone bluffs, Which appear to be remuants of a far more extended group of strata. 30 GEOLOGICAL SURVEY OF THE TERRITORIES. | The inclination is slight, 5° to 10°, about; northeast. The bluff-wall undoubtedly extended at one time over the entire interval south and southwest and was joined to the Caton City group; the intervening por- tions having been removed by erosion, with the exception of a narrow belt just at the base of the mountains. This interval is entirely occu- pied with Cretaceous rocks at the present time. The valley of the Fountain, as well as that of Monument Creek, for some distance above its junction with the Fountain, is underlaid with Upper Cretaceous groups Nos. 4 and 5; but the surface is everywhere so denuded and grassed over that the junction of the Cretaceous with the Lignitic group is nowhere well marked. The lower bed of sandstone, which is usually regarded as the com- mencement of the Lignitic, iscomposed sometimes of yielding arenaceous sediments, and therefore cannot always be relied upon as forming a fixed horizon of demarkation. But, in the majority of instances, this floor of sandstone is present with a greater or less thickness. About ten miles east of Colorado Springs, some very important coal-beds have been opened by Mr. Matt France and others. This locality is a very import- ant one for the study of this great coal-group. Between ColoradoSprings and the coal-mines, the intervening country is very rolling or undulating, and so grassed over that no sections of the underlying beds are exposed ; but, before reaching the mines, the rounded grassy hills are covered with fragments of calcareous concretions, from which have been taken a great variety of the fossils characteristic of the Upper Cretaceous. The three forms which are usually so abundant, Ammonites lobatus, Baculites ova- tus, and Inoceramus, are here found in great numbers. This point is about 600 feet higher than Colorado Springs; and inasmuch as the strata are horizontal, we may estimate the thickness of the Cretaceous beds above the valley of Monument Creek at 600 to 800 feet. As we continue to the west we soon come to dark, rusty-brown sandstones, with great numbers of a peculiar kind of sea-weed, called by Mr. Lesquereux Haly- menites. There is a series of alternate layers of arenaceous Clay and sandstones, 200 feet or more in thickness, the upper portion containing vast globular concretions, as illustrated in Plate 4, Fig. 2, which corre- spond to the mud-beds seen in the vicinity of the coal-basin of the Arkansas. LURES ERR Gecko cbianes CSbSHd ORIACEeS GAC ORCS HE CEO HE Het Be SeROrScer HS pra Her SOB SSGE Qi OER, soso seece anand cee b Loca ra le Shed Otro Base BEES Rosa aseadmaae SIBTE | GUSSH ECS SCA See CESS ree Se See ee nes er ame SES SBGEOB bees dboe Sasser PAT OAC OUSICIUYA cia tate elas eae ea erator tala oieieersisclete cise Aele Salyerataied fs cL Eau as SOLS BHO See Hares ins ecisivoc els mictis eins ce biciss Sele nis alealeicet te eee . Coal - Bata SIefey sie aTale eis eran Simla vale atayatetts tysic ya emia Meee iene . Sandstone with Plants. HEAR do Saoo pol qaOreoOnd PERS Oboe amore . Bituminous shales-. See Setar ar an ofa c ne wie aielalot eats nie crete raiat ety 47S , EeTARTGIEG! (ghlliy Ete op Ae oe a eA ME Tah Mile TPE eee Ney CAD Bet . Clay -- 5 OS Be BS CRS OOS MACH GOO IS eo Oa Corner ee mee ceginye . Hard black slate... AA OS PE SOD SHAS SS Se eae a Ao eee He Serr earn aie . Coal - BSA ae he a reteiagai ala alain ei nsicyaie rele Severe evatnle ole aiatieeie iets jac eo latn wie) sateen eel ats — SoS as ap ist) | a nD a 3 ) ® fet et CO 0 k= CO ‘ Oe OWE CHAN POOH WO? ee Ore c = In section b, which is the record of a shaft sunk at a distant local- ity in the same basin, we have only the upper bed of coal at the base. The two sections give a pretty clear idea of the strata which include the two lower beds of coal. Above the coal-bearing portion, there is an interval which we estimated at about 200 feet, in which the beds were obscure, but thin seams of impure coal cropped out. The mate- rials were clays, arenaceous clays, and thin layers of sandstone, yield- ing so readily to atmospheric forces that no sharp bluffs are formed, so that the character of the strata could not be clearly seen. We then have a range of high bluffs 200 to 400 feet high, which begin at the base of the mountains, about two miles north of Manitou, and extend across Monument Creek, and reach off to the southeast far beyond the limit of vision, down the entire valley of the Fountain to its entrance into the Arkansas River near Pueblo. The rocks all around Pueblo are Creta- ceous, yet it is quite possible that far to the eastward the Lignitic group overlaps them, having originally been connected with the coal-basin to the south near Cation City. We may thus obtain a dim conception of 32 GEOLOGICAL SURVEY OF THE TERRITORIES. the vast erosion that must have taken place here, to have removed so great a thickness of strata from so vast an area. The bluffs east of Colorado Springs, above that portion shown in Sec- tions a and b, may be regarded as-barren of workable beds of coal. A detailed section of the beds was taken, but it seems hardly necessary to present it here. So variable are these beds that the sections within a fourth of a mile would only bear a general resemblance to each other. The beds are made up of alternate layers of clay and sand, with irregu- lar beds of coneretionary sandstone throughout. These beds of sand- stone change constantly, sometimes 30 feet in thickness, and quite mas- sive at one point, and within a fourth of a mile either thinning out or changed into soft or indurated sand. Toward the summit of the blufis is a thick bed of rusty-brown sandstone, which has been worn by the atmosphere into remarkably ragged forms. As we proceed northward from Colorado Springs to the source of Monument Creek, on the divide between the South Platte and the Arkansas drainage, the upper beds of the Lignitic group appear entirely destitute of coal, with a vast thick- ness, estimated at 1,500 to 2,000 feet, with unusually coarse sediments. The materials composing these Upper Lignitie strata of the Monument Creek present the appearance of having been deposited with unusual rapidity in moving or disturbed waters. Figures show with great clearness this peculiar character of the sediments. The peculiar group of strata which, in 1869, I called the Monument Creek group, extends to a point within about twenty miles of Denver, where the Lignitiec sedi- ments return to their usual character, and then continue northward nearly to Cheyenne. For a distance of about thirty miles north of west of Monument Creek, the coarse variegated sandstones of the Monument Creek group lap on to the granites, have been slightly elevated so as to incline 5° to 159, but not detached from the granites, so that for a considerable distance these granite foot-hills formed the western shore-line for the great lake. This group is more fully treated in a subsequent portion of this chap- ter. Up to the present time, but few invertebrate remains have been found in the Lignitic group from the Arkansas to Denver; but in the lower strata in the vicinity of the coal-beds a number of plants have been observed, belonging in most instances to well-known species occurring elsewhere. These plants were observed by the Survey in several locali- ties along the southern border of the group, generally in the bed of sand- stone immediately below the lowest coal, and ranging up 100 to 150 feet. The species, as identified by Lesquereux, are Sabal Campbelli, Platanus Haydeni, Ficus tillefolia, Dombeyopsis obtusa. The Sabal has been found at Raton Hills, Golden City, Black Buttes, and on the Upper Missouri River near Fort Union. The Platanus occurs at Raton Hills, Golden City, Black Buttes, and was originally described from the Upper Missouri River, where it is found in great numbers. The Ficus has been obtained from Evanston on the Union Pacific Railroad, Raton Hills, and in Montana on the Yellowstone, so that the evidence, so far as it can be derived from the few vegetable remains, connects this group with the Raton Hills group to the southward, and far to the north on the Upper Missouri. Other species have been ‘identified. From Colorado Springs, we may follow the Lignitic group northward very nearly to Cheyenne without any break. For a short distance, as we have previously remarked, the Monument Creek group laps on to the granites, entirely concealing ‘all older formations; but very soon after crossing the “divide” to the drainage of Plum Creek, the older beds re- Wo zvaie NN } Nes rr Vatley of Rabston Cr. bb Votceztte Cape. 7 Merphy Mere LOOKING NORTH from VAN BIBBER ER. <= BN A a, Bear Station b, Morrison ad, Line of Coal outcrop-vertical c, Green Mt. Ligritie - horizontal. Section at Bear Cr HAYDEN. } GEOLOGY—LIGNITIC GROUP—SECTIONS. 33 appear in the form of uplifted ridges. This belt, though varying much in width, is not again interrupted until we reach a point within a few miles of ‘the Union Pacific Railroad, west of Cheyenne. Sometimes this belt extends out from the mountain foot-hills four or five miles, and again it closes up so that the Lignitic bed, as at Golden City, extends up to within one-fourth or one-half a mile of the granites. I need not describe again the geological features of the district about Go len City, so much has already been written, nor need I repeat the fifty or sixty species of fossil plants which have already been detected in this far-famed locality. On the map which accompanies this report, the boundary-line between the Lignitic group and the well-marked Cre- taceous strata is shown very clearly. We may say that very soon after leaving the granite foot-hills, the Lignitic beds, at whatever angle they may be found to incline, return to a nearly or quite horizontal position. We may say that they incline at all angles from 5° to 70°, depending upon their distance from the base of the mountains. From Colorado Springs to Golden City, the outcrops of the coal are very rare; but, from Golden City to the Big Boulder, they are quite com- mon, and the most productive coal-mines in Colorado are found there. That beds of lignite or coal underlie the plain country far to the east, there is hardly room to doubt. About ten miles east of Denver, on the Kansas Pacific Railroad, at a locality called Tousland, several shafts have been sunk in the level prairie, and a thick bed of coal or lignite was found at moderate depths. ° A section of the strata is as follows :— 1. Clay, gravel, ete. ENOL SAMO TOC Keg je iola cies ajalesinlciaieieise aie ews vaciaeice cemiaeicind atiersiem ie Hoa site & 10 to 12 feet. 3. Sandstone, with seams of coal varying from 1 to 18 inches in thickness, with 6 to 8 inches of sandstone between...--....-.---...----.----- 30 feet. PAC ODOT ONTO eae ses oe eee joe maieia/oaeieeicl ciclo weasel Gels oui wy ie 1 ) Talore West Monument Cr Monument Cr Upper Lignitic Strata Section along the North Boundary Line of Map Bonument Creck - Lignitic Strata, Monument Greek Group, no Coal exposed B Granile “Si Covered Monument Creek _ Orel, Shales Austins Blif¥s,_ Ingritec Sandstoncs with rasmerous Beds of Ltqnite Bonument Cr: SSI ae Beds Local Drift bLI Garhit \ Colo rude Springs [eercerr Cr Monument Cr Mesozoic Strata obscured. Oraacous Shales and wife SECTIONS accompanying MAP of COLORADO SPRINGS and VICINITY. . ~ rear ee a ee TC eat ee! eee ae eta a =< =-=-~ ——— seuy Mary og dg poyooupea 92 ho19720 770) 24D SSATTAaS ae ea a BUY U9YOLg 947 Ag weyompin IL SY DOL ALDPUULEDIS TY YP CPIUDLY Op JO PIVYUOD 24, if "STLONUIUOD JOU ALD SATO) U0) DIS QY7 IAOGD Jaf UT. ua aso pup ditjouo.ing Apodzoujdd 242 S2PTUTT -parwoo7) Kjarourco.ddy <;u0 QLD MAALNS PUY) BY} WOL, UaYD) JOU UaYyM SPVOY % ADAINS PUP) 27) ulody uoyv7 Aposoush sv surojd my wa ebourzap AY], Slop SuoIgTIBD Cy 2p. 2207 uspusyiyy qioe4 Aq AydeasSodoy, sawmpopyp pM Uopsry] Aw Aq Asopoar) “HL8[ UL podoaing sdouojng [eo9 dy] osye pue syooyy Arej}USUITpes oY} JO S}TUITYT oy} BUTIMOYS ANIT ONINOAM HHL OL MADE SVSNVYHV OAL WOU OdVHOTO) HHL 0 dVW AUYVNINITAUd a81eyQ Ul ysTBoposy Ss ) UepART A SoMOyey, ey} Jo Kaains jwoiydeisoeg pue [eo1sojooey ‘gs ‘q HOIMHLNI FL 10 UNANLYVd ad U. J) nies | eens) SELIOW IW aon gO RAT ee b o96'%| ATA9}) 8d Mmoazv07 A ALP, ons O 2g a 2 ee SESOL es = Te] ee es ee (xo. | oun y — y : é ao oe eee 0 eam oo es co cmeeen ooo Co cme siamnee See 50.07 oo meee oe ee oe mee we a) N I { Plate IV. SANDSTONE.. Leip A YG j att y “UD bez CMLL PRE Moses F1G. 2.—CONCRETIONS AND SANDSTONES, CRETACEOUS PERIOD. Ne >) ! ; as} b ‘€ 7 F yi , a3 od" ne Plate VIII. GaTEWAY TO THE ‘GARDEN OF THE ” Cororapo, Rep and WuirE Triassic SANDSTONE trp vd Meee aE y i , Dalen fre as Plate IX, CATHEDRAL Rock, ‘GARDEN OF THE GoDs,” COLORADO, RED TRIASSIC SANDSTONES, HAYDEN] CURIOUSLY—ERODED SANDSTONES. 43 it, since my first examination of it, nearly twenty years ago, yet more direct proof must be brought to bear before long in some portion of our continent. These red sandstones have always attracted much attention wherever noticed, on account of their peculiar color, but nowhere have I ever observed them performing such a conspicuous part in giving form to the scenery of the country, as along the eastern base of the Rocky Mountains in Colorado. This feature is more marked from a point about fifty miles north of Denver to Colorado Springs, than in any other por- tion of the continent. Along this belt the sandstones are more compact, with every variety of red, from a pale dull tint to a deep purple color. There is also every variety of texture, from a rather coarse conglomerate to a fine sandstone. It varies much in thickness, ranging from 400 to 2,000 feet. Its greatest thickness south of Platte Cafion is in Pleasant Park and in the “Garden of the Gods,” at Manitou. At Pleasant Park, according to Dr. Peale, the aggregate thickness of the Red Beds is about 2,000 feet. This series of beds is well shown in the pictorial section. These sandstones have been elevated at various angles varying from 20° to a vertical position. In the vicinity of the Manitou Springs, in what is usually called the ‘‘ Garden of the Gods,” the same variation is seen, but in many instances the beds are very massive, thick, and stand in a nearly vertical position. In Plates VIII and IX we can see the massive sandstones, which have been weathered into the most fantastic shapes, standing up in immense walls or columns 50 to 250 feet in height. Plate VIII represents what is called the gate or entrance to the “Garden of the Gods.” In the foreground is seen the massive wall of red sand- stone rising on either side 6f the opening to the height of 100 to 150 feet. The wall was originally continuous, but has been worn through by erosion. Whatever may have been the agents which in times past have wrought out all these remarkable forms, it is piain that they have acted in former times with far more intensity than at present. In the background, through the opening, may be seen the snow-capped sum- mits of Pike’s Peak, rising to a height of 14,147 feet above sea-level. Plate IX gives an example of what might be called a magnificent mono- lith. It is animmense column of bright-red Triassic (?) sandstone rising to a height of 250 feet above the general level, a portion of a massive stratum elevated to a vertical position, and the contiguous portions eroded away. Figure 1, plate IX, illustrates the singular columns which stand at the entrance of the ‘“ Little Garden of the Gods,” or, as it is now called, ‘‘ Glen Eyerie.” On account of the peculiar forms which these red sandstones havereceived from the eroding agents of nature, this locality will always remain one of the most celebrated in Colorado. The more careful study of the relations of these sandstones to the underlying rocks, has thrown much light on the physical history of this region. My own observations, farther to the northward, led me to the belief that the great uplift of the mountain-ranges, though imper- ceptibly slow, was an unit in its action; or, in other words, that the changes in the position of all the groups were brought about by the same cause and at thesame time. There could not be a strict conform- ity in the sedimentary gronps, inasmuch as entire groups are wanting, and in some cases only fragments of others are remaining. But I have hitherto supposed that the elevation of all the sedimentary strata along the base of the mountains was a comparatively modern event. We now have the evidence, from the texture of these red beds and their position on the anderlying granitic rocks, that the Front Range, during the supposed Triassic period, formed a vast shore-line, and that the sedi- ments of the Red Beds were deposited on the base against the sides of 44 GEOLOGICAL SURVEY OF THE TERRITORIES. the granitic range. In the annual report for 1875 the fact was stated that the Red Beds, in the form of coarse conglomerates, filled. up the uneven surface of the granitic rocks below. South of Manitou we find an enormous thickness of very coarse conglomerates, cemented with rather fine sands, jutting up against the mountain-sides, showing clearly that, although elevated and disturbed to a certain extent since their deposition, they were laid down along the base of the Front Range as a shore-line, and that there must have been a period of comparative re- pose. When these sandstones, near the base of the mountains, are found to be made up of conglomerates, they are observed to be very coarse in the immediate vicinity of the granites, but becoming finer and finer sandstones as they extend eastward into the plains. There should there- fore be some nonconformity between the Triassic and the Carboniferous and Silurian groups below, for both of the latter extend high up on the flanks of the mountains on either side, sometimes occurring on the sum- mits of the lower ranges. The section in Plate VIL would indicate some- thing of this sort, for we find the Silurian and Carboniferous inclining 20° and 45°, while the Triassic dips 90°, or is very near a vertical. The diagram also shows how the Silurian beds lie high up on the granite flanks of the mountains. The elevatory force seems to have acted ver- tically, bending the overlying sedimentary strata like metallic sheets, so that within a few yards of the nearly vertical beds the same are hori- zontal or nearly so. This will explain very clearly the abruptness with which the mountains seem to rise out of the plains to the traveler ap- proaching them from the east. The beautiful pictorial section of Pleasant Park may need a word of explanation here. The dotted line a a shows that all the élevated por- tion in the rear or west of it is composed of granitic rocks. The dotted line in the foreground, h h, shows the junction of the Lignitie group to the true Cretaceous beds which here rise up in a very narrow belt from beneath the Monument Creek group. It is exposed by the wear- ing away of the Monument Creek beds. The letter 7 indicates the usual form and isolated character of the numerous buttes that are scat- tered over the plains here for a considerable distance east of the mount- ains. The strata are nearly horizontal, the summits are flat, table- shaped, and are not unfrequently capped with trachyte. Between the dotted lines the Carboniferous, Red Beds (Triassic), Jurassic, and Cre- taceous groups are exposed. The manner of inclination and the rela- tion of these groups to the granitic range, as well as to each other, is made clear by the section. THE JURASSIC. This formation has already been described in so much detail in pre- vious reports, that I shall mention it very briefly in this connection. Far to the north this group holds a prominent position, not only on ac- count of its aggregate thickness, but also from the abundance and variety of its organic remains. South of the Union Pacific Railroad, in Colorado, it is confined to a very narrow belt, with very few if any fos- sils to establish its age. That it extends most persistently far south- ward into New Mexico, there cannot bea doubt. The narrow belt which it occupies is well shown in the small map of Colorado Springs and vi- cinity. North of the Pacific Railroad, along the base of the front range of mountains, it increases in thickness and is full of characteristic fos sils. In the annual report for 1873 and previous reports, the lithologi- cal characters of all of these eroune have been so fully discussed that it Trachyte. J, Standing Imately ey rocks Test upon gr WHY The dotted line a-a separates the Gramtestrom b, Exposure of Silurian Rocks. 0,6 Carboniftrous Strata. d,d, Triassic Redbeds. ¢,¢, Jurassic Beds. f N®1 Cretaceous. gg N°3 Cretaceous h,h, Lignitic Sandstone. v, Tertiary Butte capped with Trachyte. j, Standing Rock. Pleasant Fark. k, Platte Mountaiy. The Coal Outcrop follows, approximately the sedimentary Strata. the dotted ine hh. 4U, Points where the red and varteagated beds disappear; between these two points the outcrop is semicircular in form. North and south the cretaccous and tertiary rocks rest upon granite. Pleasant Park from the South. HAYDEN.) THE CRETACEOUS GROUP. A5 would be mere repetition to refer to them in this report. The Jurassic group in Colorado has little or no influence economically or in giving form to the peculiar scenery. THE CRETACEOUS. The Dakota group js composed of massive beds of sandstones inter- sected with layers of clay, and forms some of the most conspicuous ridges or ‘“* hogbacks” along the eastern base of the Front or Colorado range. Its importance, however, varies in different localities as much as its texture; sometimes it is scarcely seen and then again it forms one or more of the most important ridges. Its aggregate thickness is never great, varying from 200 to 400 feet, and may be represented by avery narrow belt on the map. West of the 100th meridian it has ‘yielded very few organic remains, although it has a very extended geo- graphical range. It is hardly ever wanting along the margins of the mountain ranges east of the Wasatch Mountains, in Utah. From its structure in the far West, [ regard it as a sort of transitional group be- tween the well-defined Cretaceous group and the Jurassic below. Numbers 2, 3 and 4, or the Fort Benton, Niobrara, and Fort Pierre divisions, may be regarded as one group, under the name of the Colora- do group, as adopted on Clarence King’s beautiful geological map of the Green River basin. ‘To one who has never studied these divisions in the Northwest, along the Upper Missouri River, there would seem to be no occasion for their separation. Having studied these divisions with much care in their typical localities, along the Missouri River and in Eastern Kansas and Nebraska, I found very little difficulty in tracing them across the country westward and southward, so far as my explor- ations have extended. It is very doubtful, however, if any geologist would have ever separated the Cretaceous beds between the Dakota and Fox Hills groups into divisions, had they been first studied in the interior of the continent. The Fox Hills group has a very impor- tant influence on the physical history of a most important geological period. It was at the close of this period that one of the most impor- tant biological changes occurred in geological history. So far as we know at the present time, no animal-remains, and very few, if any, vegetable forms, passed above it. A few species of plants probably began their existence in the Upper Cretaceous in the Fox Hills group and continued on up into the Lignitic group, where they reached their highest point of development. The gradual approach of shallow seas is finely shown in the character of the sedi- ments in the upper portion of the Fox Hills group. Not only the shal- low seas but the gradual change of salt to brackish and then to purely fresh waters was amply sufficient to destroy all traces of marine life, which occur soabundantly in the Fox Hills group. Fig.2, Plate LV, pre- sents a fine illustration of the remarkable concretionary masses which characterize in many localities the upper portion of the Fox Hills group as it passes into the brackish-water strata of the Lignitie or Laramie group above. This cut, though intended to illustrate a portion of the Dakota group in Hastern Kansas, serves perfectly to explain to the eye the immense rusty-brown concretions which abound in the mud- beds just beneath the lower sandstones of the Lignitic group at Canon City and at Colorado Springs, and at other localities in Eastern Colo- . rado. ‘These concretions are peculiar rounded, regularly stratified masses, often merely resting upon the pedestals of the softer and more regularly bedded sandstones below. So far as Colorado is con- 46 GEOLOGICAL SURVEY OF THE TERRITORIES. cerned, I have observed no locality where there appeared to be any striking nonconformity between the Fox Hills group and the Lignitic group above. That there may have been intervals of time, during which the Cretaceous sediments were not deposited; that there may have been dry ljand over large areas, is not impossible, but there could have been no great degree of erosion of the surface of the upper Cre- taceous beds. This apparent conformity, while in certain localities the upper Cretaceous beds received a very much increased thickness, may be due to afar more rapid deposition. In almost all cases, the transition from the Fox Hills group to the brackish-water deposits of the Lignitic seems to have been gradual, with no visible physical break of importance. The great break seems to be illustrated only in the entire change in the animal and vegetable life. But the time at my disposal will not permit me to discuss here many important questions in this connection. For the details of the geology of the Eastern base of the mountains in Colorado, the reader is referred. to the previous annual reports of the survey, especially the one for 1873. FOLIATION OF GRANITE IN ESTES PakK, COLORADO. Plate XI. li Wf Wy) Ly =A: Se i oc 7 BES gee ; ie oa pie , h if y % m (ty ; t oy Db ; | nae ev is ae x i PEAK AND EsTES Park, COLORADO. Cakiv Ade Elva ANCIENT LAKE BASINS.—GLACIAL LAKES.—MORAINAL DEPOSITS IN THE VALLEY OF THE Upper ARKANSAS RIVER AND ALONG BOTH FLANKS OF THE SAWATCH MOUNTAINS. For nearly twenty years I have written more or less in regard to the ancient lake-basins of the West, but it was only within a few years, since the facilities for traveling have so greatly increased that geologists have found that these lake-basins once oocupied the entire country from the Arctic Circle to the Isthmus of Darien. In very many in- stances they were merely expansions of river valleys, like the greater number of our lake-basins of the present day. During the early portion of the Tertiary period, the western portion of our continent was covered with immense lakes, some of which occupied a much larger area than any we are acquainted with at the present time. During the Pliocene period, and during the interval to the present time, thousands of small lakes, with a few of large size, were distributed over the great area west of the Mississippi, and the basins with their peculiar deposits are found in the parks, among the mountains, and along every important river-valley. The gathering together of the vast amount of information which is now accumulating on this subject is a task which will, at no distant Gay, be productive of most interesting results. I have made these few remarks to introduce what I may have to say in regard to the valley of the Upper Arkansas River. The Arkansas River rises in the Tennessee Pass, nearly west of Mount Lincoln, in latitude 39° 21’ and longitude 106° 19’, and flows a little east of south for a distance of about 80 miles in a straight line, when it flexes to the east, and flows through a deep caion in the granite, and emerges into the plains near Cation City. Near the sources of the river are several expansions of the valley from one to two miles in width, oval-shaped, and covered with a deposit of drift-material. Near the junction of the east branch of the Arkansas the valley, with the terraces on either side, continues pretty reguiarly about five to eight miles in width, but gradually closes up again below Lake Creek, though on either side are vast deposits of the coarse drift-material extending high up on the mountain-sides, especially on the west side of the valley. The valley then gradually expands out and enlarges about five to ten miles in width for a distance of nearly 40 miles. In the annual report for 1873 I have expressed my belief that this valley began in a monoclinal inter- val, with the great Sawatch range on the west side forming the erest of the continental water-shed, and the Park range on the east, which, with its sedimentary rocks and granite basis, formed the east side of a grand anticlinal, the aggregate mass of rocks inclining to the eastward. Our observations over a very extended area only confirmed the opinion #xpressed in our last report, that the great Sawatch range formed the central portion of a gigantic anticlinal. The west side of the Park range is, for the most part, very abrupt, and for long distances the gneissic rocks show very clearly the direction of the dip. On the east side the sedimentary rocks dip down under the surface of the South AT 48 GEOLOGICAL SURVEY OF THE TERRITORIES. Park. On the west side of the Sawatch range we have the valley of the Gunnison, and west of that the sedimentary rocks incline to the westward, unless disturbed by some center force, for the Elk Mountains. On either side of the valley small streams flow into the main channel of the Arkansas from the source to Cation City. These streams usually have their origin at the very crest or water-divide of the two ranges, and in most instances have cut their way through the solid mass to the main river. Many of these streams have numerous side-branches which have also carved out wonderful gorges near the crest of the mountains, giving to these mountain ranges a ruggedness that is almost inconceiv- able to one who has not actually explored them. It is in the study of these gorges that the geologist learns to appreciate the immense results of erosion in giving form to the rocky range’of the West. Even yet the power of this force has not been adequately understood, but the wider our range of observation, the greater is our conception of its power. We may safely assert that at some period comparatively modern, 10,000 or 15,000 feet of sedimentary beds extended uninterruptedly from the South Park across the intervdl now occupied by the Sawatch range, all of which, but insignificant remnants, have been swept away, while a mass of the granite nucleus, of inconceivable dimensions, has also been removed. The general elevation of the Sawatch range for 60 to 80 miles is 13,000 to 14,000 feet above the sea at this time, and it is highly probable that hundreds and perhaps thousands of feet have been removed from the summit. I find it difficult to estimate the extent of the erosion in this region, and can only speak of it in general terms as almost inconceivable to a finite mind. From the nature of the interval or valley, the greater number of streams flow into the Arkansas from the main Sawatch range. They are quite numerous from the Tennessee Pass to Canon City; a few come in from the east side, but the drainage tends toward the east or south- east, so that the streams that rise in 1 the Park ran ge and flow into the Arkansas are comparatively few and of little importance. The charae- ter of this drainage is well shown on the map accompanying this report. In the last annual report I dwelt with considerable detail on the effects of glacial action in this valley, and, in this report, I can only describe them in general terms, hoping that the beautiful maps and illustrated sketches by Mr. Holmes will render the story plain to the reader. As an illustration of the effects of glacial action in this valley, Lake Creek might be taken as an example. This stream rises in several branches at the very crest of the divide, forming vast amphitheaters. The signs of past glacial action are not very evident about the sources of their side- branches, and they do not reach higher than 12,000 or 12,500 feet. The summits of the high mountains are often covered with debris of broken rocks, apparently not much worn. Insomeplaces the tops ofthe mountains, like Mount Lincoln for example, are, with the exception of the extreme summit, covered with a thick covering of earth, filled with rocks more or less worn. The most conspicuous signs of glacial action are seen along the sides of the gorges lower down the streams. In the valley of Lake Creek, the sides of the gorge are worn smoothly for an elevation of at least 12,000 feet or above timber-line, and from 1,000 to 1,500 feet above the bed of the creek. ‘In many places the sides of the gorge or cahon are worn so smooth that the surface has the appearance of enamel, and a thin crust usually peels off, which I have hitherto denom- inated a “ glacial crust.” About four miles above the Upper Twin Lake on the north side of the cafion there is a round mass of granite projecting from the side 309 feet or more, and 1,000 feet high, with e ‘ te : a Nae 2 Eps AS VALLEY DEPARTMENT OF THE INTERIOR. U.S. GEOLOGICAL AND GEOGRAPHICAL SURVEY OF THE TERRITORIES, F.V, HAYDEN U.S, GHOLOWIST IN CHARGE. Section A B. rg Section CD. SKETCH and SECTIONS showing the MORAINES of the UPPER ARKANSAS VALLEY Sounsiargetritel a ; — Petit an ae ie ri WG apt } a . vey ; 5 ye f E Le r 1 we ¥ ‘ is fi 5 -_ : ‘ + 54 ae f re oo j yi iepeoe aie se Ae: etree vier - ri = = a, a, a, Arkansas River, 20 Miles. 7, rym, Inferior moraines. 7, Mt. Harvard & 6b, Greek with lateral moraines. s, La Plata:Mt. cc, c, c, Clear Creek, with lateral moraines- Iz miles long, Joo ft. high at highest point. 2muiles long, 5vo feet high at da. e,¢,e, Outcrop of grane. Moraines of the Upper Arkansas. tt Drift covered slopes. Ig Lake Creek, lateral moraines. h, h,; Twir Lakes. t, Elbert Creek. t, Mt. Elbert. 1, Terminal moraine. uw Massive Mt. Na \ RD NG \\y ZA} Ti WL ab x ENN WY, HAYDEN. ] GLACIAL ACTION—-MORAINES. 49 somewhat the appearance of a bastion which has been worn quite smooth. In the sides of it are depressions like pot-holes, evidently worn out by the attrition of loose rocks against the sides as the water flowed underneath the glacier. There are also points where vast masses of granite have been removed from the sides of the mountain at a great height, giving to the mountain-side the appearance of an ancient quarry. For a distance of about eight miles the bottom of the valley will av- erage one-fourth of a mile in width, with here and there huge masses of granite projecting above the general level, showing very clearly that the eatire valley has been carved out of the solid granitic mass. The loose - morainal deposits are not conspicuous until we reach a point about two miles above the Upper Twin Lake, where the valley expands out to about _amileto one and a half milesin width. Here a low swampy bottom eommences, which was once, undoubtedly, a portion of the Jake. On either side are ridges of the glacial deposits; these increase in size and importance as we descend to the junction of the creek with the Arkan- sas. On the south side of the lower lake a ridge extends from the mountains down to the Arkansas River, perhaps 1,000 feet high, just “south ef the upper end of the lake, and gradually sloping down 100 or 150 feet in height above the bed of the river. This is a true morainal ridge, and was doubtless formed by the crowding out on either side of the loose materials as the great glacial mass moved down the valley of Lake Creek. This morainal deposit undoubtedly laps on to the mountain-side so that the nucleus of the upper portion of the ridges is granitic. The drift deposits are not generally more than 500 to 800 feet in thickness, and usually much less. The granite crops out in numerous places on the sides of the ridge, showing most clearly that the greater portion of its nucleus is granitic; it also shows that the valley, with the surround- ing terraced hills, has been worn down by erosion from an elevation as great perhaps as the loftiest portion of the main range. The north side of Lake Creek is a very irregular ridge, full of depressions, while on the west side of these ridges are extensive accumulations of rocks more or less worn, showing the direction of the moving force. Besides the vast lateral moraines in the valleys of the streams, there are a great number of what may be called terminal moraines, or detached ridges that tend in various directions. Sometimes they extend a portion of the distance across the valley at right angles to the lateral moraines, or they may diverge at any angle; the great quantities of loose material attached to the glacier seems to have been dropped in quite irregular forms as it moved down the valley. In one instance the granite crops out at the east end of the Lower Twin Lake, about the middle of the valley, and under such circumstances that the inference is plain that the entire valley has been worn out of the solid mass of granite. One of the main objects of our description of the morainal deposits is to show the extent of the erosion which has taken place in this region, and these outcroppings of granite are the remnants that are left as proofs of the magnitude of this work. From Mr. Derry’s house, on the northwest corner of Lower Twin Lake, we have perhaps as good a general view of this valley and its surroundings as we can find. As we look to the south of west we see two tront peaks, which are shaped like eones, rising up to the height of 12,500 to 15,000 feet. A little to the southeast is an unnamed cone, with a broader sum- Init, rising above timber-line. Although these points or peaks ap- pear to be independent, yet they are really portions of spurs or Tidges extending down from the main peak, which extends further to the west and forms a part of the crest of the range, to which we 4H Se ey Bt re LLLLTTS 50 GEOLOGICAL SURVEY OF THE TERRITORIES. have given the name of La Plata, 14,302 feet above the sea. As we look in this direction, bare, brown, granite masses, rising above timber- line, meet our eyes, with here and there a few patches of snow to break the monotony or contrast with the desolate somber hue of the granite debris. Deep furrows extend down the sides of the mountains, the chan- nels for untold ages of ice, snow, and water, the agents which have bro- ken down these rocky masses and sculptured the forms which now so much excite our admiration. We see also the smoothly-worn sides of the mountain covered with a sort of enamel-like crust, as a mark of the glacial power. On the sides of the peaks, at different elevations, are nu- merous small green lakes, sometimes with a visible outlet and some- times without, reservoirs of the melting snows. The pines are often dead from the autumnal fires that have run through, adding to the deso- lation of the scene; these falling down in every direction render travel- ing almost impossible. Sometimes no vegetation takes the place of the pines after the fires have passed through them, but not unfrequently the quaking-asp poplar, with its bright green leaves in summer and yel- low in autumn, grow very densely, contrasting most charmingly with the somber green of the living pines, and the somber brown or gray of the dead. Down in the valley, and closed in on either side by mount- ains and the morainal ridges or hills, are the two beautiful lakes, which are laid down on maps as Twin Lakes, the basins of which were no doubt formed by glacial action. If the reader will examine the map accompanying the report he will see more clearly than we can describe in words the location of the beautiful lakes, the morainal ridges and mount- ains that hem them in; the contour lines are not intended to indicate elevation, but are used to show the surface forms. As there are really but two forms, granite and morainal drift, but one color is needed, and with this we have endeavored to separate the surface covered with the morainal deposit from the granite. The map will also show the eleva- tion of the lakes above the sea, 9,182 feet; also the elevation at the junction of the Lake Fork and the Arkansas, 9,096 feet. The depths of the lakes are shown by actual soundings. The greatest depth of the upper lake is 79 feet, and that of the lower 75 feet. It will be seen that the greatest depth of the lower lake is near the upper end. We may thus see by the depth of these lake-basins, as well as their shape and morainal deposits around them, that the force that produced them all moved slowly down from the mountain-range, and that the lake-basins are scooped out of the solid granite rocks. From the lower lake to the Arkansas River the morainal deposits are very thick; the surface is covered with bowlders more or less, and of greater or less size, some small, others from 20 to 50 feet in diameter. Hundreds of mounds, | ridges, and curious depressions, of all shapes and sizes, impede the traveler. The placer-mining has been very extensive here, and by this means we arrive at the true character of this glacial drift. It is com- posed mostly of rounded bowlders, but mingled with it is a kind of light- colored clay and sand. Thedecomposition of the feldspar has produced a kind of clay, which sometimes gathers into localities forming a consid- erable thickness. ; The description of the glacial action in the valley of this branch of the Arkansas will apply to the others, and presents a general view of the — detailed action in the entire valley. The history of this valley from the _ beginning may be in some points obscure, but, as I have stated in a former report, I regard it as largely due to erosion. In the process of elevation a fissure or fissures must have been formed, and in these the process of erosion commenced, continuing through a vast period of time, A " Wy Plate XII. GRANITE. HAYDEN.} MORAINAL DEPOSITS. 51 and operating with greater or less effect at different portions of that period. So far as the drift-deposits are concerned, which at the present time seem to be the only material resting on the granite in the valley, they are undoubtedly of comparatively modern origin, not extending back farther than the Pliocene, but the beginning of the erosion may reach into the past as far as the Jurassic. We have now the evidence that indicates that portions of these mountain-ranges were elevated above the Jurassic seas, and we may suppose that the general outline of the surface continues on the same plan up to the present time. if this was true—and we have no reason to believe the contrary—the erosion may have, and probably did commence far back in the past, and that during the Cretaceous and Tertiary periods the area occupied by the Sawatch range was elevated above the waters; it is more probable, © however, that these formations were deposited to a greater or less ex- tent over this area, and that they have been entirely removed or ground up with the present drift. From the source of the Arkansas at the Tennessee Pass to the caiion above Cafion City, the distance is about 60 miles, supposing this to be mainly a valley of erosion, area worn away would average about eight miles in width, the depth could not have been less than one mile, so that an approximate estimate can be made of the enormous amount of rock-material has been ground up in the excava- tion of this valley. Up to the time of the great glacial period this eroded material may have been swept out on to the plains to assist in forming the vast Cretaceous and Tertiary beds which we find there at the present day. Geologists generally admit that about the close of the Tertiary period, there was an era of intense cold, which they have agreed to call the glacial epoch, and our remarks are based on that supposition. We believe that at one period this entire valley, with all the side-valleys er cahons, was occupied witb one vast glacier, diminishing and in- creasing as the temperature was higher or lower, but gradually moving down; that is, the main mass moving southward, and the side-branches moving toward the central mass. As the sides of the mountains are worn smoothly and exhibit signs of glacial action to the height of at least 1,500 feet above the valley, we may arrive at an approximate estimate of the thickness of the glacier. The fissures of the Arkansas - and its branches may not have been nearly as large at the commence- ment of the glacial period as at the present time, and the great glacier may have performed the work of erosion for ages, and gradually melt- ing by a change of temperature to the mild climate of the present time, left the numerous mounds, ridges, and other morainal deposits which we find so extensive in this valley, and in many other portions of the Rocky Mountain region. I have spoken of this great ice-mass as a Single glacier; there may have been a single one increasing and dimin- ishing through ages with the changes of temperature at different seasons or epochs, or there may have been an unlimited number of glaciers, but the glacial phenomena as indicated by the present surface of that country shows a long and continuous period of action. I have before stated that I regarded the valley as one great lake-basin, commencing near the Tennessee Pass. The valley expands out somewhat for the first ten miles, and gradually closes up below the town of Granite for about four miles, when it opens out again into a broad, level, basin-like form. The bottoms of the main river, as well as the little branches, expose the granite rocks in such’a way that we cannot well avoid the conclusion that they have been worn down to their present position from an elevation not much inferior to the Sawatch or Park ranges. Above the Lake Creek on both sides of the Arkansas are well de- 52 GEOLOGICAL SURVEY OF THE TERRITORIES. fined terraces, which on the east side rise 600 feet above the river. The coarser materials were evidently deposited in water, and are arranged in strata and appear not to have been disturbed to any great extent by changes of level. On the west side the terraces slope down more gradually, and are cut from west to east by deep gorges, by streams from the main range. The valley itself extending to an eleva- tion of 400 to 600 feet on either side, is filled up with more or less coarse drift-deposits. These vary much at different points, sometimes made up of huge bowlders, inclosed in loose gravel, sand, or clay, and again a rather fine deposit of sand, gravel, or clay, to all appearances having been deposited in comparatively quiet waters. At any rate there were at all times portions of the lake that were not subject to great currents -or any violent agitation. On the whole, however, the drift-materials are very loose, showing that the movements of the water and ice were from north to the southward. All over the surface are scattered in vast quantities immense bowlders of granite, varying from a few feet to 50 feet in diameter. Below Granite, for four or five miles, the masses of granite are remarkable for their number and size, which appear to have been moved down Clear and Pine Creeks. Along the sides of Clear and Pine Creeks are high ridges, or lateral moraines, which may properly be compared to huge railway embankments, rising to a height of 400 to 800 feet above the valleys of the streams. Below the mouth of Pine Creek the valley soon expands, and the surface is covered with loose bowlders, while the ridges and depressions are quite remarkable, and give it almost an artificial appearance. These basin-like depressions inclosed by the moraines are not unfrequently filled with water, form- ing small lakes, often with no visible outlet. These little basins of water occupy different elevations, from the bottom terrace near the river to the point of junction of the drift on the mountain-sides, 800 to 1,200 feet above the river-bed. As we descend the river the bowlders dimin- ish in size, are more rounded, and the deposits of fine materials increase - in thickness. Below the mouth of Chalk Creek the valley is covered with a series of yellow-white marly beds, which are cut up into a variety of singular forms, resembling the ‘Bad Lands” and reaching an aggregate thickness of 800 to 1,200 feet. * These were observed by mein 1869 and named the “Arkansas marls.” Overlying these marls there is considerable thickness of coarse drift which forms to a great extent the terraces which are very marked for a distance of 30 miles. We can see, therefore, that the greater part of the finer sediments were transported to the lower or south end of the river-lake, and deposited in comparatively quiet waters. While we ascend the Arkansas Valley toward the Tennessee Pass, the proofs of great force from the combined action of water and ice are shown on a grand scale. It seems, too, that while there is a variety of deposits in this valley resting upon the granites, their history is consecutive and attributable to one general cause, local glacial action, so far as I have yet observed. I repeat the same statement which I made years ago, that I have observed no proof of any wide ex- tended drift-action like that of the New England States, but in the Rocky Mountains the superficial deposits are all of local origin ; and the source is usually limited to the drainage of the streams in which it is found. For example, although, as I have stated, I believe that all the marls and coarser deposits in the valley of the Upper Arkansas have the same origin, however different in composition, the forces that produced them | are limited geographically to the drainage of the Upper Arkansas. I could find no indications that any fragment of rock had been transported even from so short a distance as beyond the drainage west of the Sa- —* a Sarat ee. cating, ba ia ——— Plate XIII. = C4 | : ay = f iT L s " gi ca an Hine) Qe Mra Na Plate XIII. Cnrcaco Lake, Cororavo. HAYDEN. ] MORAINAL DEPOSITS. 53 watch or east of the Park ranges. It is possible that a more detailed study of the superficial deposits of this valley would afford reason. for a separation into different periods so that they might be classified, but my observations lead me to place them in one great period extend- ing from the close of the Pliocene up to the present time. As is shown by the map, the drift-deposits rest upon the granite directly, and no sedimentary beds of any other age are found in the immediate valley, and these deposits in the aggregate do not afford proof of any break in time. Still much new matter could be added to the history of their deposition if an entire season could be devoted to their study. CHAPTER V. GENERALVIEW OF THE GEOGRAPHY AND GEOLOGY OF THE ELK MOUNYAINS.—HRUPTIVE GRANITES.—RHYOLITES AND DYKES.—EROSION ON A GRAND SCALE.—LOCAL DRIFT- DEPOSITS. The Elk-Mountain group is one of the most remarkable ranges in our western Territories, and, so far as my own explorations have extended, is unique in form and structure. For this reason a small party was organized in the summer of 1874 under my immediate direction, with Mr. Holmes as assistant geologist, and Mr. Chittenden as topographer, for the special study of this curious and most interesting group. The numerous sections and maps which are given in this report form a por- tion of the results of this specific study. Much attention was given to this region the previous year, and the results printed in the annual report for 1873. As our explorations are extended to the westward of this range, we hope to be able to present a more complete geological as well as topographical view of this region. The Elk-Mountain group lies immediately west of the great Sawatch range, which ‘forms the water-divide of the continent. It occupies an area of about 800 square miles, between meridians 106° 45’ and 107° 15’, and parallels 39° 30’ and 399. The Sawatch group 1s one of the loftiest and most symmetrical ranges inthe West. It extends from the Mountain of the Holy Cross tothe north, latitude 39° 28’, longitude 106° 28’, southward to the San Luis Valley, a distance of over 80 miles. For this entire distance the range literally bristles with lofty points, about ten of which rise above 14,000 feet, and many more are 13,000 feet above sea-level. The uniformity of this great mountain-mass is a remarkable feature. Standing on some high peak and glancing along its pointed summits from north to south there seems to be comparatively little variation either in form or height. On either side of the Sawatch range there are several somewhat lower parallel ranges which are undoubtedly portions of an immense anticlinal, of which the main granitic massis the central nucleus. Between each of the parallel portions of the anticlinal are valleys at intervals of greater or less width. Immediately west of the granitic nucleus is the valley of the Gunnison, and on the east, the valley of the Upper Arkansas, and east and west of them are comparatively low granitic ranges capped with sedimentary rocks. Both the metamorphic and sedimentary rocks incline at various angles from the great. central mass. There are here represented two quite distinct types of mountain ele- vation, though the forces have influenced each other’s results to a greater or less degree. The Sawatch or main range presents an example of a long-continued, uniform movement upward, which, but for the inter- vention of side-forces, would have produced a remarkably symmetrical mountain-group with the main granitic core or central mass, and on either side parallel valleys and ranges, each becoming lower and lower until the ridges faded out in the plains. The sedimentary rocks would have inclined at various angles east and west from either side, until they became horizontal in the plains. On the east side of the main 54 Plate XIV. ! Se SS! |. ESEE=— es Se Cret. Shale | = ape AO Rhy olite ay LEN Li yyy EN Ze ‘STE UE S200 ft. Shal Yi une 200 ft. ale LZ Leg (ih © 7 iv —— ee “80 ft. Rhyolite —— A portion of the East face of Gothic Mt. showing the relations of the Eruptive Rocks to the Cretaceous Shales. « Kt Wi ihc Ut Plate XV. Mountain or tur Hoty Cross, CoLoraDo, HAYDEN. ] GEOLOGY OF THE ELK MOUNTAINS. 55 range, in the South Park range, the eruptive | groups have thrown the sedimentary beds into the utmost confusion, prod ucing those remarkable faults and irregularities which were shown in the “annual report for 1873. On the west side, in the Elk Mountains, the confusion is still greater, producing not only the most remarkable faults in all the western eountry, but literally overturning thousands of feet of strata. By exam- ining the preliminary map of Colorado i in this report, if will be seen that the trend of the Sawatch range is very nearly north ‘and south, and that the principal peaks from the Mountain of the Holy Cross at the north to Mount Ouray to the south lie along that line. The trend of the Elk group, * though less regular, will be seen to be about northwest and south- east. This is a grand illustration of an eruptive range, and appears also to be an example of a sudden violent or catastrophic action. The im- mense faults, complete overturning of thousands of feet of strata, and the great number of peaks, all composed of eruptive rocks, indicate, per haps, periodical and violent action in contradistinction tolong-continued uniform movements of the elevatory forces. The sections and 1 maps which accom- pany this report will doubtless enable the geologist to determine the cor- rectness of our statements. The map will show by the colors the erup- tive points, where the granite appears to have been thrust up, as it were, through the vast overlying crust; sometimes a great thickness of strata of various ages is carried up to the summits of the peaks, 13,000 or 14,000 feet in elevation above the sea. Again we find, but a few yards away, the same group of strata in the bottom of the lowest val- leys, indicating remarkable convulsive movements. Although the Elk group may be regarded as an eruptive range, it will be seen by the map and section that the elevatory forces, whether convulsive or uniform and slow, acted along a well-defined axis, thus, as a range, forming a true anticlinal. We see, therefore, that the eruptive agents acted along a great fissure in the earth’s crust as a line of greatest weakness, and that this line possessed a trend about northwestand southeast. But the peculiar nature of the forces produced the wonderful chaos in the position of the sedi- mentary beds, while the tendency ofthese strata is toincline from either side of the axis. It is not uncommon to find thousands of feet of strata which have been carried up to the loftiest points of the axial ridge in nearly or quite a horizontal position. We may suppose that at one period the vast sedimentary mass rested on a floor of pasty or semi-pasty granite; that the forces in the interior were struggling to find vent, carried upward the entire overlying mass of sedimentary strata, and that bere and there many thousands of feet in thickness along the axial line or ridge was thrust up through the melted or semi-melted granite in such masses as are shown on the map, at Italia, White Rock, Snow Mass, Capi- toland Sopris Peaks. The map will show that this i igneous gra nite does not reveal itself except along this quite regular axial line. The areas of granite are greatly enlarged by subsequent erosive action, while from the axis numerous streams cut deep gorges, 1,500 to 3,000 feet in depth, sometimes far into the underlying floor of igneous granite. During this period of revolution, and probably subsequently, there were great numbers of dykes or orifices from which issued the rhyolites and ‘basalts. Gothic and Crested peaks are illustrations of the upthrust of vast masses of rhyolite, and numerous other quite long dykes will be noticed on the map. Plate XIV represents a portion of the east face of Gothic Mountain, the central mass of which is rhyolite, with only the Cretaceous beds litted up around the baseandsides. This is an excellent example of these 56 GECLOGICAL SURVEY OF TIIE TERRITORIES. remarkable upthrusts of ignecus material, vertically through the over- lying sedimentary beds. ‘The Cretaceous strata of Nos. 3 and 4 extend up onthe sides of the peak about 1,000 feet above the bed of Hast River, with very little inclination, and between the strata of shale were pressed out portions of the igneous material. The illustration, Plate XIV, is so clear that but little space need be used in explanations. The shale all belongs to Cretaceous formation No. 4. An examination of the map and plate of sections would indicate that the aggregate force which elevated the Elk range acted vertically with atangential movement or shove, as it were, from the northeast toward the southwest. There are many faults of remarkable character on the northeast side of the axis, but no very marked examples of the inversion of strata, but on the southwest side of the axis this feature is shown in a marked degree. Time will not permit us to work out in detail in this report the wonderful complications in the strata, which have been pro- duced by the various elevating forces in this range. Much of it was brought out in the various reports in the annual report of the survey for 1873. Mr. Holmes wiil also introduce important details into his report. I shall, therefore, at this time, confine myself to a general view of the geology of this range, which, with the beautiful and remarkably clear illustrations, will be sufficient for the information of the geologist. The axis of the Elk range can be easily traced on the map, and the axial section will show. the immense masses of strata that were carried high up to the very summits of the range. At the southeast corner of the map it will be observed there is a con- siderable area designated as metamorphic granite. This forms a part of the Sawatch Mountains, and may serve to show the relations of that range. To the west of it there are narrow belts, marked as Silurian and Carboniferous. These represent masses of strata that were origi- nally lifted up by the Sawatch range and incline toward the west. On the completed geological map of Colorado, the connection of these fragmentary masses of sedimentary strata about the summits of the high granite mountains will be made clear. We shall hereafter attempt to show by a series of sections, not only that the Triassic, Jurassic, and Cretaceous groups originally existed here in full force, but that they probably extended across the area now occupied by the Sawatch range and were united with the sedimentary beds of the South Park range. The northeastern slope of the Elk group slopes down into the valley of the Roaring Fork, an important branch of Grand River. Here we find a large area of the various divisious of the Cretacéous group. The Dakota group rests upon the Jurassic, but is not exposed to any great extent, except in the cations or gorges of the streams. So far, therefore, as a map is concerned, it cannot be represented except by a very nar- row band, but above it there is from 1,000 to 1,500 feet of the remaining portions of the group, Nos. 2, 3, 4, and 5, but not as well defined even as on the eastern side of the Colorado or Front range. The greater portion is composed of black shaly clays with thick beds of sandstones appearing in different positions. A few Cretaceous fossils occur, of well- known and common genera, as Ammonites, Baculites, and Inoceramus. Very few of the smaller forms were observed. This singular Creta- ceous area seems now to form a sort of basin with the Jurassic and Triassic, or Red Beds all around it. Its peculiar form will be noticed on the map. The*Cretaceous beds occupy very varied positions, sometimes high up on the mountain-sides nearly to the summits, and then filling up the lower valleys. The faults are without num- ber, for in the process of elevation the strata seem to have been Perea HAYDEN.) GEOLOGY OF THE ELK MOUNTAINS. 5T broken in every direction. The aggregate inclination, however, is always to the northeast. This great mass of Cretaceous beds were influenced by the operations of two quite distinct elevatory forces which probably acted synchronously, so far as forces so different could act. To the eastward the long ridges of the Triassic and Carboniferous Red Beds extend down to the west from the axis of the Sawatch range, cut into deep cafons, the waters of which flow into the Grand River. These Red Beds were elevated by the Sawatch range, while the Roaring Fork flows through a sort of anticlinal valley between the axis of the Elk and the Sawatch Mountains. These Cretaceous beds form a sort of an island or basin between these great axes, and therefore Hein the syn- elinal. It is by means of the more modern beds, as the Cretaceous group, that the anticlinal character of the mountain range is more clearly seen.e The Triassic and the Carboniferous beds extend over the axis of the range, while the granite nucleus makes its appearance only in limited areas, as at Sopris, Capitol, Snow Mass, and White Rock peaks. Be- tween Capitol and Sopris peaks there is a long distance where the Red Beds form the axial ridge entirely, and seem to hold for the most part a horizontal position. On the map the Red Beds or Triassic and the Carboniferous groups are thrown together, from the fact that we found very great difficulty in separating them. Not only is there no apparent break in the sequence of the strata, but they are so mingled together in the uplifts and overturnings that it would have required more de- tailed study of the range to separate them entirely than we were able to give at that time. Co-extensive with the narrow belt of the Dakota group, 1s a light band which represents the Jurassic group. Neither of these formations is ever exposed over large areas, usually only in out- cropping edges along the margins of the mountain, or in the sides of the eahons. The Silurian group, so far as it is known in this region, always rests directly on the granites, whether igneous or metamorphic, and is, therefore, confined mostly to an outcropping belt around the granite areas. On the west and southwest sides of the axis the Cretaceous group appears again, extending far beyond the limits of the map. Its relations to the axis are such as to show plainly that, like the older formations, it formerly extended in an unbroken mass across the area of the Elk range. There can be no doubt of the original continuity of the entire mass of the sedimentary strata. North and west of Sopris _ Peak the country slopes off toward the Colorado River, and the sur- face is gashed deeply with the gorges of the streams which cut through the Cretaceous beds, oftentimes into the older groups. The Cretaceous strata, however, predominate. In the annual report for 1873, the tremendous effects of erosion, as shown on the west side of the Elk Mountains, were described in detail. These effects are displayed even on a still grander scale on the east side of the range. The gorges or cafions cut by Castle and Maroon Creeks and their branches, are probably without a parallel for ruggedness, depth, and picturesque beauty in any portion of the West. The great variety of colors of the rocks, the remarkable and unique forms of the peaks, and the extreme ruggedness, all conspire to impress the beholder With wonder. The illustration, given in the northeast corner of the mInap, of Castle group isa type of the scenery at the heads of these Streams. We here see from 3,000 to 5,000 feet of stratified rocks lifted up vertically so that the beds are horizontal, or nearly so, presenting to the eye, by the eroded forms, a wilderness "of pyramidal cones whose summits rise to a height of 13,000 and 14,000 feet. The sides of the callons are vertical or nearly so, displaying a continuous section of the 58 GEOLOGICAL SURVEY OF THE TERRITORIES. strata 2,500 to 3,000 feet, composed of alternate beds of sandstones and . conglomerates with thin layers of clay or shale. These sandstones vary very much in structure in the same layer, from a fine-grained sandstone or quartzite to a rather coarse conglomerate. These changes may occur in different portions of the same layer or at different positions in the same group of strata. The lower portion of the cafion is composed of rather compact.sandstones, but toward the summit the rocks become a brick-red and are formed of rather loose sandy material. All the rocks vary in color from a dark dull purple to a brick-red, depending much on the influence of heat. There is a considerable degree of change in these rocks from heat, but only in a few cases amounting to complete metamorphism. These massive walls and pyramids are often inter- sected with dikes which have filled either vertical fissures or not un- frequently have been thrust between strata, forming local beds of rhyolite, sometimes of great thickness. The dividing ridge forms a curious zigzag line, often so narrow as to be almost impassable to one on foot. Enormous amphitheaters have been slowly carved out of the fading ridge at the head of each little branch. Without speculating upon the character of the forces which were at work here in the far past, whether they were far more intense in their action than at present, we may infer that at this time they operate exceedingly slow. Portions of the divid- ing wall are falling all the time, from the influence of frost or water, and in many instances the amphitheaters extending back over the true di- vide, sometimes even breaking through the axialridge. Usually a vast accumulation of débris may be found damming up the gorge at various distances from the immediate head of the amphitheater, thus giv- ing origin to a small lake, the waters of which gradually soak. through the débris, and, coming out on the lower side, gather into a small stream. It seems "hardly possible that at the present time there are any agents in existence that could have transported this débris down the gorge. It must have required a considerable quantity of water, with large masses of snow or ice, for the debris is often composed of large masses of rock that could only have been moved by floating ice. In the valley of Roaring Fork, the morainal deposits are remarkable for their thickness. The surface is covered with huge bowlders, some angular and others partially rounded. The terraces are very conspicu- ous, rising, in some instances, to 1,000 feet or more above the bed of the stream and strewed over with huge bowlders. None of the stray ma- terials in any of these valleys or gorges seem to have been transported a very great distance, and never, under any circumstances, is there any drift or glacial deposits from a neighboring drainage; in other words, the loose material does not pass from one independent valley to another. So it is all over the Rocky Mountain region so far as I have observed. All the drift or Post-pliocene deposits are local. @ regret that, for want of time, this meager account of so important a range of mountains must be closed. In the final report, in quarto, which will accompany the atlas of maps, we hope to present a more careful review of each range of mountains, with their relations to each other. In this report I have attempted to number the plates in consecutive order, but the sheets of sections and maps could not be so numbered, but will probably be clearly understood. CHAPTER V1. REPORT ON THE GEOLOGY OF THE NORTHWESTERN POR- TION OF THE ELK RANGE. By W. H. HoLmzs. DEAR Sim: In accordance with instructions received from you, I con- tinued the geologic examination of the northwest portion of the Elk Mountains, and beg leave to present the following report: When it was found that, on account of the sickness of Mr. Shanks, assistant topographer, the main party could not advance beyond Capi- tol Creek, a small party, consisting of Mr. George B. Chittenden, topographer, myself, and one packer, was detailed to continue thesurvey around to the northwest. It was arranged that we should carry with us provisions for fifteen days, and that a supply-party should meet us on the western side of the range, near the sources of East River, if the main party should not be able to reach that point in time. On the 29th day of August, we left the main camp and moved down the valley of Roaring Fork. 66 GEOLOGICAL SURVEY OF -THE TERRITORIES. below, so that there was a gradation from solid sandstones at the top to homogeneous shales at the base. The section includes the group of strata sometimes called the “ transition group” by Dr. Hayden. The horizon is’ probably that of the upper part of No.5, Cretaceous. The dip of the beds in this place is toward the northwest 10° to 15°. They seem put slightly affected by the elevation of the main range on the east, or of Treasury Mountain on the south. Farther up the stream, which we shall call Aspen Creek, the dip increases to 45°, and the upturned edges are lodged against the granite, which, by means of a rather complicated fault, has been thrust up past the broken edges of the entire series of ' earlier sedimentary rocks, bending the edges of the older strata back and driving them into the softer strata above. In the bottom of the creek a small portion of the yellow quartzites are exposed, situated as shown in Section D of the large sheet. This fault would seem to be on the northern continuation of the line of upheaval to which belongs the inverted series observed last year about the southern sources ef Rock Creek. Our investigations at that time were extended to within six miles of this point. Late in the evening we encamped near timber-line, and on the follow- ing morning climbed the high granite ridge to our left. We soon found ourselves in the very midst of the mountains. Snow Mass and Capitol and Mount Daly rose up magnificently in the east, Sopris stood alone at the north, and many groups of lofty mountains appeared in the southwest. All around us were only bare rock and snow. The whole area is above timber-line, and the sculpture of the mountains is won- derfully striking and picturesque. The long crooked lines of crests are connected by subordinate crests, and these all send out sharp, narrow branching ridges which separate the amphitheater-like heads of the numerous radiating streams. As a rule, these high valleys are wide and the ridges narrow, so that the country presents the appearance, in arude way, of a giant honeycomb. Sopris is connected with Capitol by the flat ridge of Carboniferous red beds, Capitol with Snow Mass by a deeply-indented saddle, while south from Snow Mass, the axis erest continues to Maroon Mountain, thence to the White Rock and Castle peaks. From the saddle, midway between Capitol and Snow Mass, a pinnacled ridge extends to the westward between the head-waters of Bast Fork or Avalanche Creek and Rock Creek proper. Branches are thrown out from this between all the small streams, while the chief crest of the spur continues out to station 22. Stations 24 and 25 were made about midway on this ridge. Station 24 is the most northerly summit of the Snow Mass granite, and is eight miles from station 22. The sedimentary outcrops, which pass just north of Capitol and Daly peaks, sweep around to the north of this station and turn to the south- ward, crossing Aspen Creek, as described on the preceding page. Here the entire series is exposed, there only the Upper Cretaceous and bits of the Paleozoic rocks in the bed of the creek. The lines of outcrop can be traced between the two points. The older rocks gradually disappear as the granite begins to fault up past the broken edges. (See colored map). This may be regarded as the farthest northern extension of the great fault-fold previously mentioned. This fold being a most compli-_ cated and interesting piece of dynamics, calls for a separate analysis, which I give farther on. On the 3d we descended Aspen Creek to the main creek and continued the examination of the Cretaceous section. The black shales, the upper part of which are exposed in the bluff on the north side of Aspen Creek, | occupy the valley from the base of the bluff to the base of Treasury SS, PES Treasury Mountain “.u, Treasury Mt ~ yuagquaversal ,— b cast branch. of Rock. Creek 0, suuth Branch, ._d d.Jurictton eee, outcrops of Shales oP NX cret, circling the north end of Treasuny Me, GULGE, outerops of Lonel. ~ g Hulls, hh h, Bluff of middle cretaceotts Shales andl. Sandstones facing Aspe Creek , . t,t,t, Trachyte intruded among the Shades | — w, Clifton CreeX near the Mouth of which is the seam. of anthracite Coal —— The Creek vut into Theaaury Me atc and. ib anal paas ont ut the tills g. : cee — i i i if hy t yy ZS ee L0bbel ME BEELY Fig. 8.—CascaDE ON ROCK CREEK, COLORADO. HULMES.] TREASURY MOUNTAIN. 67 Mountain. The dip is at first slight, but before we reach the Lower Cre- taceous, it rises to 30°. The strike is at right angles to the stream- course, but turnsto the south on both sides of the mountain. It appears, from such examinations as I was able to make, that Treasury Mountain is a short anticlinal, or oval shaped quaquaversal, that seems to have been produced by some agent. associated with great heat, since the high degree of metamorphism of the entire series up to the Middle Cretaceous is quite remarkable. I doubt if the sedimentary measures are entirely penetrated in any part of the mountain. The Jurassic and Lower Creta- ceous rocks reach high up the sides of the arch, while the lines of shale- outcrop are ranged around and support the base. The dip is toward Rock Creek on the east and north, and toward two of its tributaries on the south and west. The only place where the Paleozoic rocks have been penetrated and exposed ison the east side, where the two branches of Rock Creek, leaving the Cretaceous synclinal, cut directly into the side of the anticlinal, passing through the Cretaceous, Jurassic, and Upper Carboniferous rocks, into the Lower Carboniferous, (see Figure 7;) here, in a deep, narrow cation, they unite, and turning to the right the resultant stream follows for some distance along the strike until it reaches the north end of the ovai, where it cuts its way out again into the broad depression eroded from the Cretaceous shales. In passing out over the highly met- amorphosed beds of the Dakota group, a splendid cascade is formed with a fall of 500 or 600 feet. The sandstones of this group are so greatly changed here that it would be impossible to recognize them out- side of their relations to fhe overlying strata. They are reduced toa very hard flinty quartzite, greenish in color and nearly uniform through- out. The shales above are much hardened, and the Jurassic and other substrata are so consolidated as to be but a series of flinty quartzites. For the sake of comparison I present in this connection, Fig. 9, two sec- tions of the Cretaceous rocks, one made in this locality and the other on the border of the plains. The Dakota group is everwhere the same. The series of shales are almost identical, and the transitions from shales to the sandstones aboye areas like as possible. Palm-leaves and fucoids are found in the lower part of these sandstones and in corresponding horizons. In the east the lignitic coal is found near the base cf the sandstones, while the anthracite coal of the West occurs 2,000feet higher. An an- alysis of this coal, made by Professor Mallett, demonstrates the fact that it is of fine quality. (See chapter IX, Dr. Peale’s Report.) The seam is about four feet thick, but the locality is one most difficult of access as well as remote from any probable market. It certainly cannot be utilized for many years yet unless the immediate region shou!d prove rich in mines, in which case it would be invaluable for smelting purposes. Between Treasury Mountain and the Snow Mass group there isa long, narrow Cretaceous valley, produced by an abrupt synclinal fold, in which the strata are doubled back upon each other. The forces have so pre- dominated on the east side that the beds on that side are pushed beyond _ the vertical and lie atop of the gently inclined strata of the west side. The Upper Cretaceous sandstones do not occur in this depression south of Aspen Creek; we have, therefore, a double thickness of the black Shales in the middle of the valley, giving in all a thickness of nearly 4,000 feet. The shales are followed or supported on either side by the older strata, in the usual order. The depression produced by this fold may be followed the whole length of the Elk range, and separates it from _ the West Elk group, producing northern and southern systems of drain- age. 68 ‘ GEOLOGICAL SURVEY OF THE TERRITORIES. THE GREAT FAULT FOLD OF THE ELK RANGE. On September 5th we reached the northern limit of our last year’s work, and little remained to be done but to examine a few complicated spots along the main fold of the Elk range. Most of the difficult prob-° lems occur along this fold, between station 24 on the north and Cascade Creek on the south, and as the axis of the fold is west of the crest of the range, the complicated parts are cut by the deep transverse valleys of the western slope and many good sections are exposed. Six of these, D, E, F, G, H, and I, are given in the main sheet of sections accompany- ing the map. It will be observed by reference to the map that the granite, which is represented by heavy horizontal lines and marked A A, occurs in two great masses, and that in these masses are the culminating sum- mits of the range. The northern, which is cut by sections D and B, is the Snow Mass group, and the southern,-cut by sections G, H, and I, is the White Rock group. At first glance it might seem that these were separate centers of elevation or upheaval, or at least that they were not intimately related, but closer examination develops the fact that there is a line of disturbance of a very marked and extraordinary character connecting them. Section F cuts this fold at ee, and gives one of its peculiar phases. But I found that a very large number of sections, even, could not be made to give a connected idea of so complex a fold. I have, therefore, prepared the accompanying illustration (Fig. 11), in which the entire fold is given in relief and so placed upon an outline map that the location of the various parts may be easily recognized. I have carefully kept in view the idea of showing simply the peculiar foldings of the broken edges of the strata. The granite areas have been shaded down and the effects of erosion partially ignored in order to develop the one idea, and a single convenient horizon, the base of the Cretaceous, is taken, entirely disincumbered, for the sake of greater simplicity. It should be remembered that this representation is highly artificial ; that in reality the fold is very obscure, and has but little apparent effect upon the topography; that it is cut into fragments by ten immense valleys ; and that its anatomy can only be studied on the steep faces of the ridges between these valleys. It will be seen by reference to the figure and the sections opposite, that the conditions all along the east side are simple, there being a — eradual and gentle dip from the crest of the range toward the valley of Roaring Fork, while on the west side there has been a general depres- sion or downthrow, so to speak, amounting in many places to 7,000 or 8,000 feet; at the same time a combination of movements, principally lateral, have produced along the axis an immense wrinkle, a fold so abrupt that the beds are crushed and shattered and the severed edges shoved past each other, as shown in the drawing and sections be- tween e and n. It will not be difficult to imagine that while this was going on, the plastic mass beneath was assisting the movements and shaping the results, and that during the process it forced itself, or was forced, through the fractured line in the two great masses of the Snow Mass and White Rock groups. Beginning at the north, I shall give a detailed description. All along the north face of the Snow Mass group the sedimentary rocks lie in the usual order upon the granites, with a slight dip toward the north. (See axis-section, large sheet.) Between Station 24 and Aspen Creek the . granite begins to fault up past the broken edges of the sedimentary 1 : a tA Bias | Wenn | ay ILL LI Sandstones Sandstone 2000 Ft. Jov0 to 2000 ft. Sandstone and Shales Nol Cretaceous 300TTE. Fig.9 Sandstones = Lignitte Coal Measures. Sandstone 100 to 200 ft. 500 to 600 feet Sandstones and Shales. 2000ft. Shales & Clay Relations of the Coal Beds to No.1 Cretaceous. Section 1, West of the Range, Elk Mts. Section 2, East of the Range,- Cache la Foudre, or Carton City. HOLMES.] FAULT FOLD OF THE ELK RANGE. 69 strata, and at Aspen Creek,as previously mentioned, only the Upper Cretaceous remains in view, with a fragment of primordial rock at a in the deepest part of the valley. South of Aspen Creek for a few miles the whole series seems to be depressed beneath the sur- face, while the granite peaks on the east side of the fault-line rise to the height of 3,000 feet, making a total displacement of at least 11,000 feet. South of b there is a high, sharp ridge formed of a series of almost vertical Carboniferous rocks, which seem to have been carried up by the granite, or at least to have been left in the present position by the dragging of the fault. In the south end of this ridge the dip increases from 90 to 133 degrees, that is, 45 degrees beyond the vertical, and nearly the whole series of sedimentary rocks appear in this position in the side of the canon at ¢. In the triangular spur between ¢ and d, a large mass has been carried back 90 degrees past the vertical, so that the Silurian quartzites oc- cupy the top of the ridge, and the Cretaceous rocks the bottom of the valley. The foid has been so sharp at e that the beds have been broken off, and the continued upward movement of the granite has bent the broken edges up, producing a synclinal in the inverted strata. In this place the belt of granite is quite narrow, so that the relative positions of the strata on opposite sides can be studied with ease. The Silurian rocks of the east side outcrop on the summit. of the water-shed of the range at f 2,000 feet above the creek, and since the Middle Cretaceous rocks of the west side are depressed to an unknown depth beneath the creek-bed, we can safely say that there is a vertical displacement of at least 8,000 feet. The amount of lateral movement (at right angles to the axis of the fault) may be expressed by the difference between the width of the gran- ite belt e f and that of the inverted fragment d e, and will hardly fall short of 6,000 feet. South of e the beds gradually rise again from the inverted position, and a high, narrow ridge is formed of the almost vertical Carboniferous rocks. This ridge is not above four miles in length, and is connected with the main range by an irregular cross-ridge that separates the head- waters of the north and south branches of Rock Creek. The tongue of granite that extends southward from Snow Mass along the fault-line is obscured before reaching this cross-ridge by the overlapping sedimen- tary rocks (ath). Here the greatest confusion occurs, and large masses of the rocks, of all ages, are found in the most unheard-of relations to each other. The strata of the west side have been depressed and caught beneath the encroaching strata of the east side, and are folded back upon themselves, as seen in the drawing, Figure 11. This peculiar and somewhat irregular fold may be traced for a distance of six or seven miles, and in this distance is cut at right angles by three immense val- leys. The sections exposed in the faces of these are not always distinct, but at the same time make it possible to study the peculiar anatomy of the fold. I observe that in every place where there is an exposure the Carboniferous rocks of the east side rest upon the upper surfaces of the hard sandstones of the Dakota group, and with such a degree of regu- larity that I was for a long time in doubtas to the identity of the latter. In studying the section exposed on the north side of the valley which crosses the fault at 7, I began near the crest of the main range west ot Maroon Mountain, and passed down through nearly 3,000 feet of Carbon- iferous sandstones, limestones, and conglomerates (which have a gen- tle dip to the east and undoubtedly belong to the eastern side of the 70 GEOLOGICAL SURVEY OF THE TERRITORIES. range), but on the slope between h and 7, I came suddenly upon the well-known sandstone of No. 1 Cretaceous, lying beneath the Paleozoic rocks and to all appearances conformable with them. Keeping on at right angles to the dip, I passed first over the outcropping edges of Jurassic and Triassic (?) rocks; then over a ridge of Carboniferous conglom- erates and limestones, much crushed and metamorphosed ; and finally, beneath these still, over a full but much distorted series of Triassic, Juras- sic, and Cretaceousrocks. The dip rises in places to 70 and 80 degrees, and the strikes are not quite uniform. I was at first entirely unable to account for this extraordinary succession of strata, and did not succeed in solving the problem until I had followed the outcrops across the valley to the south and discovered in the higher ridge at 7 the arch of the fold, which, on the opposite side of the valley, had been carried away. It seems that in the first place a great fault occurred, in which there was a throw sufficient to place the Lower Cretaceous of the west side opposite the Lower Carboniferous of the east side, and that a powerful lateral movement had then driven the opposing strata together, the harder Carboniferous rocks sliding forward upon the upper surface of the quartzites of the Dakota group, and at the same time bending them and portions of the firmer substrata back in a sharp fold, which, from the continued pressure, has been carried en masse beyond the vertical and almost severed below by the immense pressure. (See section F, large sheet.) In the next ridge south, at j, the fold is not so abrupt, and the ridge m, facing White Rock Creek, there is only a gentle arch of the strata (see section G, large sheet), while a considerable gap occurs between the faulted strata in which the granite appears. At » the infolding ceases, and in the valley at o the strata dip some forty degrees to the west (section H, large sheet). Toward p they rise again to the vertical, and at qg have been pushed back to forty-five de- grees past the vertical by a mass of granite, which now lies superim- posed upon the ridges like so much trachyte. Before reaching the bed of Teocalli Creek at 7, the strata fall back again almost to the normal horizontal position. Here the fault forks; one branch extends southward through s, and the other turns eastward along the north face of Teocalli Mountain and continues in a pretty direct course to station 3. The elevation on the north side of this branch of the fault has been very great, and has extended over a large area. White Rock and Am- phitheater Mountains have probably been the highest granitic points, but the whole mass of the Castle group has been carried up so uniformly that the Paleozoic rocks lie in an almost horizontal position upon a plateau-like mass of granite. (See section H, large sheet.) A few miles south of station 3, which is the most southeasterly gran- ite outcrop of the Castle group, a small pyramidal mass of granite has forced its way up through the primordial rocks bordering the granites of the Sawatch range, producing the summit of Italian peak. Although this bit of granite seems quite isolated from the previously-described centers of disturbance, a very marked line of fracture and faulting may be traced between it and the Castle group, but as the details of this region have already been given by Drs. Hayden and Peale, I shall con- tent myself by giving, in conclusion, a brief recapitulation of the more striking features of the Elk range. Topographically speaking, it is a spur of the great continental divide, but geologically it is quite inde- pendent in origin. It trends nearly northwest and southeast, so that . one extremity lies high upon-the slopes of the Sawatch range, while the other extends far out into the low country bordering the Grand River. : 5 os i w ery Reba ew ene bY aan et Pm a, ws ie Nd ee ik pune ARIES a erosera nor A at's sSatabaye ‘4 ee ee ee en p 7 Het ls Rea, nee oe . SE 4 Gested Butte WHH. I&75. FIG.V. PART of THE GREAT FAULT FOLD oF tHe ELK MOUNTAINS. ip. YG (Cot conc Ltectd,) Gievicar’ Ditolirdibhiogbaptite/ Gjeviee tog tip lite HOLMES.] SUMMARY. (al It seems to owe its present conformation to the occurrence of three nearly parallel lines or belts of displacement, two of depression and one of elevation. The depression along the valley of Roaring Fork, which has already been presented in Fig. 1, is included between the diverging axes of the two ranges, and exhibits some very curious examples of faulting and folding. The elevated belt, which constitutes the ran ge, is about forty miles in length. Itslopes oently toward the depression on the east, but drops off very abruptly on the west in a great fault-fold. Four considerable areas of eruptive granite occur along the axis of this belt or zone, and the de- pressions between these contain synclinal folds of the sedimentary beds, as seen in the longitudinal section given on the large sheet. Té will be ‘noticed, by reference to the transverse sections, that the axis section, which follows approximately the crests of the range, is generally to the east of the axis of displacement. The reason of this © _will be plain, when it is observed that the entire series of strata rise gradually from the valley of the Roaring Fork synelinal, until the axis of displacement is reached, and that the highest points, which would at first stand along the line of this axis, are now carried back by erosion from one to five miles to the east. The amount of vertical displacement along the fault-fold, between Aspen Creek on the northwest, and station 3 on the southeast, does not fall short of 5,000 feet at any point, and will probably measure 10,000 feet in one or two places along the west side of the Snow Mass group. The depressed belt west of the range, occupied by the valleys of Rock Creek and East River, is very intimately associated with the fault-fold, and has been produced by the downthrow on that side rather than by any independent folding, as the strata do not rise at all to the west, except for a few miles along the east face of Treasury Mountain, as seen in sections EK and F. On the 1ith day of September we fell in with the main party just south of Italien Mountain, and after spending a few days in the review of the geology about the headwaters of Kast River, began our return march to the East. cae bg eros timbered. High Rugged) \ Y Blurrs of shnaston’ 0, Ro. DEPARTMENT OF THE INTERIOR US. Geological and Geographical Survey of the Territories FY. Hayden, U,S.Grologist in Charge = iwi, i AS Ga iS ij OF THE =S q “| pf = ELK MOUNTAINS é Z : = B: i FRON SURVEY BY Vee enc 0, ne ; GB Chittenden in 1674. OS Ge hare ie WITH cE 7 = SNS ul en...| Eas ~ uth ~” + yyre(| fi Seale 2Miles to Winch — Batis oi “s I +. +! Scale of Miles a +p bes ) i ——_——— re es +" 5 tl si ’ ong 7 >, wt Bes = ay aa tet me St y ‘ SS Fs “SOTES Seta tty Contoure are te hundred feet «part Sa fe Abitudre are tn feet above the Sea and have been Pia Rr pe Miri daurmined by combination of « baremerric and trigone- Slite Rast ~) fi} meric method is ‘Prosle are shown Chis —— + e+ of: oe ’ Sate 2595 35 Br Sy AG oS Sov oe he ee Hn | Benen Ge Gobeeancen tscay a0 aetna. faut Aan pale EEE ey Ses o CSAIHHII ED WA asl Game Group fram the West Typical Sedimentary Weathering Garbontferscis Sun itstorie Sow Maen Mc from the Went Typical Granite Mearhering Iryeritd Beat of Carbunil Rocks ot a. LEGEND. i i} Rugged Spurs of the SAWATCH RANGE oe Ne ore elie I AR ESL 8 NTE ES IY I nteaeperr gee arene: Snow Mass | i7 W973 1. | ee nn ene 3 A S 5 H 2 Vasungton Gulch - Cretaceous Shales-1800 10 3000 1% chick -Foustts, canmcmmm V0.1. Cretaceous -Quartrite-200 to 300 /t.~Foeatls [N, _Surussio- Shales, Maris Sand and Lime- 500 to nea t.-No Fossila Red Beda ~Sandstenes Gglemeratcs-1000 (2 2400 ft.-No Possile | CarBoraiferous ~SanditoneLimestens, Conglomerate and Shale, 400 ts bers A. ~Foorila Silurian(?)- Qtrartiite,~ 400 w 600 ft.-No Fossils areas es of the EUk Range- Erigave Ms [eat S| oranite of he Sanatch Range Metamorphic. SECTIONS accompanying MAP of ELK MOUNTAINS. Vertical and Horizontal Scales the Same. 1874 0,0, Contact of Eruptive x Mctamerphic Granites. 12,0 Beds of Kayotite intruded Between Sedimentary Strata. Base Line of Sections soo fect shore the Sea. Level The dotted Lines shew the probable Cures of No} ee aeae EN faeaert riers f | | Se eae Ne eene REPORT OF A. C. PEALE, M. D., GEOLOGIST OF MIDDLE DIVISION. 1874. REPORT OF A. C. PEALE, M. D., GEOLOGIST OF THE MIDDLE DIVISION. WASHINGTON, D. C., May 15, 1875. Str: I have the honor herewith to submit my report as geologist of the middle division of the United States Geological and Geographical Survey of the Territories for the season of 1874. The report of Mr. Henry Gannett, who was in charge of the division, will supplement this report, and to it I refer for more “detailed informa- tion in regard to the routes followed, elevation, and topographical fea- tures of the district assigned us. We left Denver on the 21st of July, and by the 5th of August had commenced work near the head of the Eagle River. On the 1st of November work was suspended and we started for Den- ver, reaching that city about the middle of the month. During the three montis we were in the field at work 5,300 square miles were sur- veyed. My plan of working was in general the same as during the season of 1873. Accompanying the topographer in charge to almost all the high sta- tions, I made sketches of the surrounding country, on which I definéd in colors the boundaries of the various formations. Whenever time permitted I made detailed sections of the strata. This report is divided into nine chapters, the first three of which are devoted to the general geological and topographical features respect- ively of the valleys of Eagle, Grand, and Gunnison Rivers. The suc- ceeding chapters give the special and detailed features of the various formations, and the economical geology of the district. Catalogues of the minerals and rocks are appended. The report is accompanied by maps and sections, for which I am largely indebted to Mr. William H. Holmes and Mr. Henry Gannett. I have colored the geological formations on a provisional map, reduced by photography from the original drawing of Mr. Gannett’s map of the district. The rapidity of preparation and necessary absence during publication of the report must be my excuse for any errors that may appear. In conclusion I wish to express my thanks for the cordial co-opera- tion of all the members of the party. With great respect, [remain your obedient servant, A. C. PEALE. Dr. F. V. HAYDEN, United States Gologist. 75 eek Winey CONVENTIONAL SICNS USED IN PLATES T TH IV VIL VIET LX XIV Ouarizcles Light colored gsandslores LBL C8 C2 C4 GB UBABCURELY SA2RZAALAU Mh hts COLO BAUADBLOUN GA Ped sand slores Grpsferous Cites eal Light shales Dark Geile » Limestones Alblluviusrn Po rphyrilie trachyle Rhyolcte, lufa.@ obsidian Breccta Basalt Archaean INTRODUCTION. The territory assigned to the middle division for the season of 1873 was thus outlined in the letter of instruction given to Mr. Gannett, who - was in charge, on taking the field: ‘*The boundaries of the area to be mapped by your division (or as much of it as the season will allow) are as follows: Commencing at the intersection of meridian 109° 30/ and the Grand River, the line runs northeastward up the Grand River to the junction of the Eagle River; thence up the Eagle River to the mouth of Roche Moutonnée Creek ; thence westward along the northern boundary of last summev’s (1873) work to its intersection with meridian 107°; thence southward along the western side of last summer’s work, approximately on the 107th meridian, to parallel 38° 30’; thence westward on this parallel to the intersection of meridian 109° 30’; and thence northward on this merid- ian to the intersection of 109° 30’ with Grand River.” This area has an irregular boundary, Grand River, on the north, and includes between 7,000 and 8,000 square miles, of which about 5,300 Square miles were actually worked during the season. The area is bounded on the west by the Uncompahgre and Gunnison Rivers, leav- ing the area west of these streams for another season. ‘This gave us a well-defined naturat boundary as our western limit. The greater por- tion of the area is plateau country, the elevation of which ranges from 9,000 feet to 11,000 feet above sealevel. The mountainous portion is limited to the southeastern part, along the western edge of the Elk Mountains. The drainage is comprehended in two systems, viz, that of the Grand River and that of the Gunnison River. The entire district is within the limits of the reservation for the Ute indians, and a large portion of it had never been visited by white men. In 1853 Captain Gunnison, exploring for a route for a Pacific Railroad, surveyed a belt of country along the river that now bears his name. In the winter of 1853~54, Col. John C. Frémont passed over nearly the same route that Gunnison did. In 1845 Frémont followed the Arkansas to its head, crossed Tennessee Pass (called Utah Pass by him), to the Piney (Eagle), and followed it for some distance, finally crossing to the Blue (Grand River), and continuing westward. In 1873 Lieutenant Ruffner followed Ohio Creek to its head, crossed to the head of Anthra- _ cite Creek, and thence to Slate River, going eastward to the Arkansas. All these were merely reconnaissance surveys, and added but little to _ our knowledge of the country outside of their routes. The great mass ( bi of country lying between was unexplored. The general geological features of the district will be given in subse- quent chapters. The greater portion of the district is covered with rocks of Tertiary and Cretaceous age, covered in places with lava- flows. Mr. Gannett’s report will give all details in regard to the elevations of peaks and passes, and topography of the country. 17 j ‘ . ; Ni (3 CHAE ine i. SURFACE GEOLOGY—VALLEY OF EAGLE RIVER. Eagle River is a branch of Grand River, one of the forks uniting to form the Colorado. It rises immediately opposite the head of the Arkansas, and is about sixty-four miles in length. At its head it is formed by two main branches, one having its source in the Park range, and the other rising in the Sawatch range, which terminates in the Mountain of the Holy Cross. The Sawatch range, on the western side of the valley of the Arkansas River, forms the continental divide. North of the Holy Cross the range falls off, the water-shed or divide crossing to the eastward at Tennessee Pass, between the heads of Hagle River and the Arkansas. Eagle River flows around the northern end of the Sawatch range. Its general course, at first, is a little west of north. Ten miles north of the Holy Cross it bends more to the westward, and the general course for nearly fourteen miles is north 64° west. Itthen turns abruptly and. flows south 78° west, which course it holds quite uniformly for about twenty miles, to its mouth. The greater part of its drainage is from the south. The entire area drained by the southern branches is a little over five hundred square miles. The opposite side of the river was in Mr. Marvine’s district, and will no doubt be fully treated of in his report. The river is @ very rapid stream throughout its entire length. The average fall is 67.2 feet per mile. From Tennessee Pass to the mouth of Roche-Moutonnée Creek, the rate is 150 feet, and from here to the head of the second caiion 49.4 feet, while from the latter place to the mouth it is 32.4 feet. f The upper part of Eaglé River was partially described in the last annual report (1873), our division having followed it as far as Roche- Moutonnée Creek, for the purpose of ascending the Mountain of the Holy Cross. In order that this report may be complete I will have to repeat a portion of the notes on my work of the previous year. For a distance of about three miles from Tennessee Pass the river is in a canon-like valley, the hills on either side being comparatively low and rounded. The rocks are granitic, with occasional dikes of volcanic ma- terial. From this canon the stream emerges into a broad meadow-like valley of about four miles in length, in which it is joined by the branch ‘rising in the Park range near Quandary peak. The valley is three miles in width, the hills on either side of granitic rock being capped with sedimentary formations, which will be referred to in more detail in another part of the report. Leaving this valley, the river flows immediately into a cation with steep sides, the trail leav- ‘ing and crossing to the western branch. A line of outcrop of quartz- “ites crosses the river and follows the summit of the ridge between the two branches. These beds are, in all probability, primordial. Car- _ boniferous beds outcrop on the eastern side of the eastern branch, but I defer their description for the present. 79 SO GEOLOGICAL SURVEY OF THE TERRITORIES. The western branch is in reality the continuation of the main river, being twelve miles long. It rises in the Sawatch range, and drains the country for six miles south of the Mountain of the Holy Cross. Its course at first is north 40° east, but in the lower two miles it flows almost at right angles to this, being parallel to the eastern branch. On the western side of the stream the hills are gneissic, the sedimentary cap- ping have been removed by erosion. All the streams joining the river above the mouth of the Piney on the south and west present abundant evidence of intense glacial action. They are parallel to each other, the general course being north 40° east. The glaciation was described in the report for 1873, and I, therefore, simply refer to it here. Before uniting with the western branch, the eastern fork is joined by a branch of considerable size having its source in the Park range, opposite Ten-Mile Creek, one of the tributaries of Blue River. The geology about the head of this stream has never as yet been fully inves- tigated, but I am inclined to think that all the formations, from the Carboniferous to the Red Beds, inclusive, will be found along its course. The Cretaceous beds would scarcely appear until we reach a point farther north, near Mount Powell. As I mentioned in last year’s re- port,* I think it probable that a fault extends along the western edge of the Park range, west of Blue River. After the union of the two forks, Eagle River enters a deep and inac- cessible cafion of about four miles in length, cut in dark-colored gneissic rocks, from which it emerges just above the mouth of Roche-Moutonnée Creek. The trail keeps high (800 to 1,000 feet) above the level of the river, on the hills on the eastern side, near the edge of the sedimentary formations, which are exposed on both sides of the cafion. On the western side there are only patches of quartzite, remnants of the Pots- dam group. Onthe eastern side there are other beds, probably of Silurian age, upon which rest Carboniferous layers, and possibly the Devonian, although it seems to be altogether wanting, there being no positive evi- dence of its existence here. These beds all dip about 10° to 20° to the northeast, the inclination gradually changing more to the north as we follow the river. In the bluffs on the right-hand side of the river, oppo- site the mouth of Roche-Moutonnée Creek, formations from those of Pri- mordial age to the Permian, or Permo-Carboniferous, are exposed. This, of course, includes the Devonian doubtfully, for that formation has not, as yet, been positively identified in Colorado. Just above the mouth of the creek gneiss is seen on the edge of the river, but as we go down, higher and higher sedimentary beds gradually form the base of the bluffs, and below the Piney the line of outcrop of the Carboniferous crosses, and still farther down even the Cretaceous shows on both sides, the strike curving around the end of the range and continuing along the western side to the Elk Mountains, in our last year’s district. On the west side of the river, as far as the Piney, there are long spurs, or ridges, sloping gently at an angle of about 10°, toward the river. These ridges are capped with quartzite, which I have considered to be the equivalent of the Potsdam group. These quartzites terminate within a short distance of the center of the range. Hrosion has re- moved the beds formerly resting upon them, their hardness preserving them. They are shown in Section B, Plate I. The creeks, separating these ridges, have their origin in beautiful meadow-like parks, nestling immediately below the peaks in the range, from whose snow banks they derive their supply of water; thence they flow with a comparatively uniform descent to within a short distance of *Seventh Annual Report, 1873, page 242. * CL OMEGS : cs . Se bay ‘ ca eA Mas . PSS SE ZLOB Mg Mig __. LALLA CLG sae poe ZE Nilo? a D IEE 2 . SS \ = Wy : ; h < 7 } us iE Bs - = : —— ~s = % Hh oe she - Z ae = zee = ‘I o1eTd = GEOLOGY—EAGLE RIVER. | 81 Eagle, when they descend rapidly to its level. The erosion along the main stream has been much greater for several reasons. In the first place the beds have a dip from the main range, leaving, perhaps, a sort of trough between the Sawatch range and the Park range. This de- termined the course of the river, which we accordingly find curving around the range as the sedimentary formations do. These beds are also in a great measure made up of sandstones that are comparatively soft, and yielded readily to the action of water. The river, therefore, is in a monoclinal rift for a considerable portion of its course. In thecanon, above the mouth of Roche-Moutonnée Creek, the streams reach the river by falis and cascades. The slopes are heavily timbered with dense pine forests, and along the streams are groves of cottonwood, (Populus tremuloides.) In the canon are huge bowlders, which, mingled with the dead and fallen timber where the forest has been swept by fires, cause great difficulty in traveling. At the mouth of the Piney, a stream coming in from the east, the river again enters a canon. It is something over a mile in length. At the head of the canon is a high bluif on the right side, while the op- posite bank is broken down, allowing the passage of the trail over the hill, not very far above the level of the water. On the south side, on the top of the quartzite, (Potsdam ?) are lime- stones, and, a short distance below, the Carboniferous sandstones cross the river, the angle of inclination being about 25°, a little more to the northward than in the bluffs opposite Roche-Moutonnée Creek. Below the cafion the Eagle enters a broad valley, extending for ten mniles, to the head of another canon. This valley will probably average a mile in width, and is filled with the debris washed from the hills on either side. It is terraced and covered with a growth of sage-brush, (Artemisia.) Bordering the river is a narrow belt of alluvium which widens in the lower part of the valley around two small lake-expan- sions of the stream. There are beautiful meadows around the lakes. The lower lake is about a mile long and an eighth of a mile wide, while eo upper one is much smaller, being only a little over a half a mile in ength. P Here we found a party of men camped. They were prospecting and fishing. Eagle River abounds in delicious trout of a large size, some that we measured being sixteen inches in length. Their plan was to _ take the fish every week to Oro City, on the Arkansas River, and sell them. They also claimed to have found gold in some of the streams coming from the Sawatch range. The gold, if present, is probably de- rived from the granitic and gneissic rocks that prevail near the heads of the creeks. The course of the Eagle through the valley we have just described is north 75° west. On the southwest side, the long sloping spurs that we Loticed above the Piney still continue. Near the river they are lower, and, for the most part, grassed over, only an occasional outcrop of lime- Stone or sandstone appearing. On the opposite side are outcrops of ted sandstone (Triassic?). I have referred to the cation which bounds the lower end of the valley. Itissomewhat curious. On entering it the Tiver changes its course and flows north 45° west, which direction it keeps for four miles. It then turns abruptly and flows south 72° west. This portion of its course in the cafion is three miles in length. On the south ide is a semicircular ridge, extending from the head of the caiion to its oot. It reminds one of a bow, while the river, with its bend, is the rd ready drawn to discharge the arrow. We made two stations cn 6H 82 GEOLOGICAL SURVEY OF THE TERRITORIES. this ridge, which is 1,500 to 2,000 feet above the river. Its rim is made of the sandstone of No. 1 Cretaceous (Dakota group), which crosses the river at the head of the canon, almost at right angles to its course, the dip being in the direction of the stream. On the north side there is a curious spoon-like curve in the strata, shown in Plate II, which will be fully explained in Mr. Marvine’s report, as it is in his district. Be- neath the Cretaceous sandstone, in place, are the Jurassic shales and limestones, followed by the Red Beds, (Triassic?) underneath which is a series of gypsiferous beds, exposed on both sides of the river. These will all be referred to again when I come to speak of the various for- mations separately. The river, on leaving the cafion, keeps the course it has there until it reaches the Grand. The valley is about twelve miles long, extending to within five or six miles of the Grand. It is wide and bordered with ~ low hills of gypsiferous shales, covered with a growth of cedar ( Juniperus occidentalis). Beyond these hills are higher ones, not reaching above timber-line, the basis being red sandstones. The gypsum hills are con- spicuous from their white color and their softness, which causes them to yield readily to eroding influences. They are therefore much cut up by gullies which forthe greater portion of the year are dry, but during storms are the beds of torrents washing down the soft clay. Each creek extending into them, fans out into a great number of small gullies. The shales and sandstones of which they are formed belong to the same hori- zon, viz, Carboniferous or Permo-Carboniferous, as do those mentioned as occurring below the Red Beds above the cation. It seemsas though the Eagle, instead of entering the cation and cutting its way across the hard: sandstone of the Dakota group, should have worn its channel through these softer beds that lie to the southward of its present course. It might perhaps have done this, but that an island of eruptive rock (basalt), of great hardness, caps the hills south of the canon (see map A), forming a barrier that in all probability determined its deflection to the northward. Fig. 1, Plate Il, represents a section across this area from the Eagle to creek g. There are two large creeks flowing into the Eagle from the south in this lower valley. The first or eastern one I will designate as creek g, and the other ascreek h. They both have their origin in a broad-topped ridge of red sandstone (Triassic ?) which forms the divide or water-shed between Frying-Pan Creek, a tributary of Roaring Fork, and the waters of the Eagle. In 1873 we made a, station (No. 82), on this ridge, and from it | made asection,* showing the structure of the country as it ap- peared to be looking northward. I said, in the report,t that there seemed to be a series of faults and that the section might have to be modified when the region should have been more closely studied. I found this year that the beds I then thought to be Cretaceous, judg- ing from the color as seen from the station on looking north, are really the gypsiferous beds that lie beneath the red, sandstones. Instead of a number of faults, therefore, as shown in the illustration (Fig. 3, plate 19, Report for 1873), there is simply an exposure of the gypsum-beds in both the places marked “ Cretaceous,” at the head of creek and in the valley of Hagle River. As I mentioned in my notes of last year, the red sandstones on station 82 dip a few degrees west of north, inclining at a comparatively small angle, which increases as we go northward. On station 8, the dip is in the same direction, as also on station 9. AS * Plate 19, Fig. 3, 7th Annual Report, 1873. t Page 266, 7th Annual Report, 1873. Plate II. aaa Cret. Nos 4) Limestones of Nos2 cad 5 © Voleunc Ridge ad Pass to Grand R. e Martegeted Juras. Shales Fold on Hagle River ‘dy M4 sag Uu0N22S ZIT LAr Wybog ae | \\ ate sqyiMg Quowesy ory Z , 2 fe eu LLL Be TLE ev" Id PEALE.) GEOLOGY—EAGLE RIVER. Oo the creeks g and h flow towards the Eagle they cut deeper and deeper, “until the gypsiferous beds are exposed. The course of the streams is, in general, north 32° west, being entirely different from that of Roche- Moutonnée Creek and its parallel streams. The latter flow north 40° east. The branches between the mouth of the Piney and the head of the canton above creek f havea direction almost due north. What the exact rela- tion is between the beds on both sides of the Hagle I cannot say. Tn the shales forming the central masses there is a great variety in the dips, owing probably to a number of minor folds, to elucidate which would have required more time than I had at my disposal. On the north side of the river in, Mr. Marvine’s district, the red sand- stones overlying the Gypsiferous series dip a little east of north at an angle of from 6° to 8°. On the south side, as we have already seen, the dip is west of north. Between the two, therefore, there is either a line of faulting or fold- ing; I incline to believe the latter. I could find nothing that indicated the existence of a fault. There may have been more than one fold, all, however, very gentle in character. The axis of a synclinal fold, I think, runs along the edge of the hills on the south side, having a direction about north 70° west. The southern half of the fold is all that is left, the other side having been removed by erosion. ‘There was probably another fold between this and the river. Between creek g and the canon there is a patch of Cretaceous rocks forming a semi-quaquaversal. This was, I think, the head of the synclinal fold referred to above. The cause of the basin may have been the crossing of the first fold by a sec- ond. ; In the hill south of Eagle River, and between it and creek h, there is a gentle synclinal fold, the axis of which is parallel to the one first de- seribed. In the valley above, with the exception of some irregular dips in the gypsiferous beds, it is obliterated. Just beyond this fold is the anticlinal fold, the axis of which is occupied by the river. This may be a prolongation of the fold between Hagle River and creek g, where we have the volcanic rock capping the hills. The folds seem to radiate from a point near here and to become broader and shallower as we go down stream. I could not determine whether the ends of the strata were broken or not beneath the volcanic material. I will refer to this again in a subsequent portion of the report. Below the mouth of creek h, the Eagle is in a ecafion-like valley which continues to the Grand. As I have already said, this valley is the axis of an anticlinal fold, the rocks on both sides dipping away from the river, the red sandstones (Triassic) being on top, and pink gypsiferous sandstones below. In the gypsiferous hills or the north side of the river, Mr. Marvine noticed indications. of an anticlinal fold that he thinks may be the prolongation of the one in the cafion. I am inclined to think, however, that it was merely a local fold in those beds, and that the river above the cafion still keeps in the same axis, although erosion has removed so much material that it is difficult to decide. As I have already mentioned, there is a gentle synclinal fold occupying the hill on south side of the river. It is on the Summit, and its axis is parallel to the course of the river. This fold is represented at E in section C, Plate III, which is made on the line G, O, EK, F, of map A. Section D is a section across the valley of the Kagle from station No. 9, the Red Beds capping the station resting on the gyp- siferous beds. _ Bordering theriver on the north side, a short distance above its mouth, 1s an irregular layer of eruptive rock, probably basalt, which forms a 84 GEOLOGICAL SURVEY OF THE TERRITORIES. low bluff-like wali, ten to twenty feet above the level of the water. It seems to have come down the ravines in the hills bordering the valley, and to have spread out like the slag from a furnace. The river seems to have stopped its progress, for no trace of the rock could be found on the south side. It seems to have forced the river to the southern side of the valley, and the force of the water has scooped out the hills, leav- -ing bluffs on that side in which the strata forming the hills are beauti- fully shown. Shewing lines of Sections . AB = line f Section A S ND py bab / an [Min] Silurian |fff||| Cab kZermian ZA; F if { Crta Jurassic NSS rite |: ¥°."| Volcanic ea f f NASIR SCC SOIR DERE rN cme iatined AF RO rae ke eS es geen acre Ll ree La Son CHAPTER IL « SURFACE GEOLOGY—GRAND RIVER AND ITS TRIBUTARIES. Grand River rises in Grand Lake, in the northeast corner of Middle Park, west of Long’s Peak, and derives its supply ot water near its head from the Colorado or Front Range, the divide between Middle and North Parks and the Park range. It unites with the Green River to form the Colorado, and has a total length of about three hundred and fifty miles, of which one hundred and fifteen miles is in our district. It rises farther eastward than any other water in Colorado which flows into the Pacific. On some maps the name Blue River is given to it, while the name Grand is applied to the Gunnison and to the Grand proper below the mouth of the Gunnison. Gunnison* calls it Nah-un-kah-reaor Blue River, and the Gunnison he namesthe Grand. Blue River, in reality, isin Mid- dle Park and a branch of the Grand. The reasons for using the name Grand in preference to Blue are briefly as follows: It is really the main stream, being, at the junction of the Gunnison, twice the size of the latter, andif the name is given to the lower portion it should also be given to the largest stream above. Again, it is so known all through Colorado and at its head in Middle Park, and will probably, therefore, always hold good, whiie the name Blue is restricted to the branch rising in the divide between the Middle Park and the South Park, and flowing northward along the eastern side of the Park range. In Middle Park Grand River is from forty to fifty miles in length, and has been fully described by Mr. Marvine in his report for 1873, and from the Park range to the mouth of Hagle River, a distance of about forty-five miles in a straight line, it lies within his district for 1874, and will no gloubt be fully reported on by him. From the mouth of the Eagle to the mouth of the Gunnison, it formed the boundary between the northern and middle districts, and we have therefore to treat bere only of the general features and geology of its southern drainage in this part of its course. There are three large branches which I will take up in their order, commencing at the mouth of the Eagle. On glancing at the map we notice that there are two general courses for the streams, the Grand flowing south of west and turning more and more to the southward as we go west, until at one point it flows almost due south, afterward turning to the west before reaching the mouth of the Gunnison. The courses of the main branches, especially of the first two, are west of north. The third holds the same general course at meee are afterward modified by circumstances that will be explained arther on. *Pacific Railroad Report, vol. ii. 85 % 86 GEOLOGICAL SURVEY OF THE TERRITORIES. The area drained by these branches includes about 1,300 square mniles. ; The country included is generally plateau-like in charagter. This is more apparent to the westward, and in the divide between the Grand River and the North Fork of the Gunnison. The general elevation of the plateau is from 9,000 feet to 11,000 feet. In the eastern portion, from the Hagie River to a short distance west of Roaring Fork, are rolling hills covered with scrub-oak (Quercus alba), cotton-woods (Populus tremuloides), and stunted cedars (Juniperus occi- dentalis). The latter was most abundant on the lower slopes, and seemed to thrive best on soil derived from the breaking down of the shales in the upper part of the Cretaceous and Tertiary formations. The rocks throughout this region were mostly of Tertiary age, capped in places by basalt. The general geology, however, will be dwelt on as we proceed. The course of the Grand, from the mouth of the Eagle to the mouth of Roaring Fork,is south 60° west. Most of this distance, sixteen miles in an air-line, the river is in caiion, the head of which is a little over three miles below the Eagle. It is probably impassable to travel, the sides being very steep. There is no Indian trail following the course of the river. Mr. Marvine’s party kept on the hills some distance back from the edge on the northern side, and we followed an Indian trail across the hills to a stream which joins the Grand at the head of the canon. This trail seemed to be much used and leads across to Roaring Fork, which it strikes above the mouth of Rock Creek, a branch rising in the Elk Mountains. : The valley above the cafion is about three and a half miles in length, and although wider than the valley of the Eagle just above its mouth, is still comparatively narrow. On the north side are limestone slopes, and on the south low, rounded hills of the gypsiferous beds. At the head of the canon and forming the gateway, as it were, are beds of mas- sive limestone, probably of Carboniterous age. They dip to the north- east, inclining about 20°. Farther along in the caion there may be out- crops of older beds, which can be determined only by following the bluffs close to the river. The hills on the south side of the canon are capped with a black vesicular basalt, which rests immediately on the Triassic red sandstones. The dip of these beds I was unable to deter- mine, but they are probably conformable to the layers beneath. The creek up which the trail led, after leaving the Grand, joins the river by cutting a small cafion through limestones similar to"those at the head of the cafion of the Grand. These beds are somewhat mas- sive, and above them are blue limestones with interlaminated sand- stones passing into gray and white sandstones, with yellow and black shaly beds above. These are beneath the pink gypsiferous beds‘out- cropping farther up and corresponding with those on Eagle River. Still farther up stream the Red Beds appear, the line of outcrop crossing the creek near its head. Leaving this creek, we crossed to the waters of Roaring Fork, the first | stream reached being a branch joining it about two miles below the mouth of Rock Creek. The country between the Grand and Roaring Fork here is a rolling plateau covered mostly with a growth of serub- oak. The plateau is capped with a black vesicular basalt, which in places is worn away, exposing the red sandstone beneath. The head of the creek is in cafion in which the Cretaceous beds are shown, dipping to the southwest. Station No. 11 was almost on the line be- tween the top of the Red Beds and the overlying stata. Farther down ® : at ial 7 4, PEALE.] GEOLOGY—ROARING FORK. 87 the creek there are exposures of Cretaceous beds in patches, whose re- lations I was unable to determine definitely. Between the head of the creek and Frying-Pan Creek is a broad- topped hill or mesa, capped with black vesicular basalt. I referred to this mesa last year,* and then supposed the capping to be trachytic. The beds beneath it, outcropping on the south and southeast sides, are almost horizontal, the sandstone of the Dakota group (Cretaceous No. 1) - appearing on top, the Jurassic beds and Triassic sandstones lying be- neath in their order. A short distance farther north, on Frying-Pan Creek, the dip of the red sandstones, which outcrop in massive beds, is a little east of north at avery slight angle, 5° to 10°. As.we have already seen, the Cretaceous formations*on station 11 dip southwest. The head of the creek that we are describing, probably has its origin in a syuclinal depression, which deepens to the northwest in going down the creek, and gradually dies out beyond its head on the broad-topped hiils north of Frying-Pan. The folds in this region are generally very gentle, but their axes run in almost every direction. There is so much eruptive material on top of the sedimentary beds that it is difficult to trace the connections between the different ontcrops. Mr. Marvine thinks there is a fault running beneath the plateau, between the Grand and Roaring Fork. Seattered along the course of the creek, and its brancbes rising in the plateau, are numerous little meadows. The Jower seven miles of its course the creek is in cafion, which deepens rapidly as we go down. Therocks at the head are basaltic, capping the bluffs oneither side. They are present on the hills, or rather plateau, throughout the length of the caion. Atone point [ think Cretaceous shows, although I cannot be certain, as I did not have time to visit the outcrop. Farther down, the Red Beds show, and beneath them, at the mouth of the creek, there is a considerable thickness of the gypsiferous series. I will take up next the valley of Roaring Fork. The upper portion of the valley was described in last year’s report, so that this year we have to do only with the lower part of its course, that below the mouth of Frying-Pan Creek. There is one point, however, that I wish to refer tohere. When speakingt of the small butte between Maroon Creek and Roaring Fork, | was at a loss to account for the inversion of the beds exposed in the butte of which I gave a section. This year the Elk Mountain region was studied in more detail and a great many obscure points were explained. In the case mentioned above, Mr. Holmes found a line of faulting extending along the upper side of Roaring Fork which explained the inversion of the strata. Below the mouth of Frying-Pan Creek on the right-hand side are low, Tolling hills, the basis of which seems to be the Upper Cretaceous forma- sion. On the opposite side, however, there are outcrops of red sand- Stones beneath in the bluffs. The Cretaceous strata extend to the gran- ite of Sopris peak, seeming to rest immediately upon it, there being nothing showing between until we get on tbe other faces of the moun- tain. The geology about the southern part of the peak was referred to last year. Jurassic, Triassic, and Carboniferous layers outcrop on Rock Creek, but this region will be fully described in other parts of the re- port, so I merely mention it here and to return Roaring Fork. The course of the latter stream from the mouth of Frying-Pan to the mouth of Rock Creek, a distance of eleven or twelve miles, is north 70° west, the rate of fall being about fifty feet to the mile. The valley above *Page 265, report of 1873. tPage 263, Report 1873. 88 GEOLOGICAL SURVEY OF THE TERRITORIES. the mouth of Rock Creek is about two miles in width, and beautifully terraced. The river splits into numerous branches, inclosing islets on‘ which are groves of cottonwoods. The terrace bluffs on the north side are about one hundred feet in height. Rock Creek enters the valley, emerging from the Elk Mountains, about three miles above its mouth. After the junction of the two streams, Rock Creek turns and flows north 25° west. Just before it turns, it flows by bluffs of red sandstone, out- cropping on the north side. They dip 10° to 20° a few degrees east of north. A short distance back of the river they are capped with basalt, and covered with a growth of low cedars. The hills continue on the north or northeast side of the river until we reach the Grand. There is some slight folding at right angles to the river, allowing the gypsiferous beds to outcrop as we go down. It is only a minor fold, tor Roaring Fork occupies the axis of the main fold, whichis an anticlinal. On the opposite side of the river there are well-marked hog-backs, in which the strike is parallel to the course of the river, as is shown also in the parallel course of the streams draining them. A section through these hog-backs and across Roaring Fork is shown in section F, Plate IV. In the hills, farther back, there is basalt on the summits. The hog-backs extend to within about four miles of the Grand, when the basaltic capping comes so near the river as to preserve the cdge of the hills and prevent the underlying beds from being eroded. The line of outcrop also curves slightly to the westward, under the capping, so that the Cretaceous No. 1, which forms the best defined hog back, is considerably farther from Roaring Fork, near the Grand, than it is near Rock Creek. At this point, then, the Red Beds are seen on top, and beneath a considerable thickness of the gypsiferous strata outcrops on both sides of the river. Those on the south side have weathered into curious pinnacle and tower like forms of pink, yel- low, gray, and creamy colors. The valley of Roaring Fork is here comparatively narrow. The river and local drift is terraced, the terraces in the lower part of the valley being covered with bow!d- ers of black basalt, from the hills back of the hog-backs. About three miles and a half above the mouth, Roaring Fork is joined by the creek draining the hog-backs, which here cuts across them and flows along the upper edge of a terrace that is 200 feet above the level of the river. The course of the river here is almost due north untilit joins the Grand, just as the latter emerges from the canon that commences below the mouth of the Eagle. The exit is through a narrow gorge in the lime- stones. These limestones continue along the upper side of the river, dipping generally toward the south, at an angle of 20° to 30°. The inclination is more abrupt near theriver, decreasing as we go back, un- til, on the summit of the hills, the beds are almost horizontal. On the south side the Red Beds outcrop, forming bluffs that at some points are five hundred feet in height, rising in sheer precipices. There are proba- bly gypsiferous beds beneath, but they are concealed by the local débris. A short distance back the edge of the basaltic mass capping the hills appears. Its outlines are somewhat difficult to trace in places, as it is covered with a growth of scrub-oak, and scattered groves of cotton- woods. The line of outcrop of the Dakota group appears from beneath the basaltic area, and keeps along the lower side of the river, the strike being north 75° west. The beds form a series of hog-backs, the contin- uation of those on Roaring Fork. They extend along the Grand on the lower side for eight miles, when they cross and stretch away to the north- west, in anisolated range which gradually dies out in a plateau. A sec- tion across these hog-backs west of station 17 is shown in Fig. 2, Plate Plate lV. Grand River Ze Mm eae ma lhe a Oe eo . PEALE.] GEOLOGY——GRAND RIVER. 89 IV. The valley of the Grand below the mouth of Roaring Fork is only about two miles long, the river again entering a cation. At the head of this canon the Red Beds cross, and are shown on both sides. The river gradually bends and follows the strike, in a monoclinal, rift for six miles, when it turns again and cuts abruptly across almost at right angles to the strike, flowing through a valley cut in the soft shaly beds that le just above the Dakota group. This valley is only a few wiles in length, and in it the river is joined by quite a large stream from the north, which flows along the eastern base of the Cretaceous range, which I have described as ending in the plateau to the northwest. From this valley the river cuts through the strata at right angles to the strike, and comes out into a broad valley, - through which it flows for fifteen or twenty miles, and enters another canon, or rather canon-like valley, cut in a plateau in which the beds are almost, if not quite, horizontal. This canon is more or less persist- ent until the river enters the valley in which it is joined by the Gun- nison. The general course of the river ior about nineteen or twenty miles is south 76°-75° west. At the head of the valley the bluffs are almost vertical, and, indeed, in some places, the cliffs, as seen in certain lights, appear to overhang. At the point where the course changes to the southward, the valley is wider, and the Grand splits, forming islands in the midst of the river. This is northwest of station 50. The plateau here, between the Grand and Plateau Creeks, is narrow, and has in reality degenerated into a ridge from which the basaltie capping has been removed. Returning to the valley above the cafion, we see that itis from fifteen to twenty miles in length, and that the drainage on the south is princi- pally through two streams, one in the eastern portion and the other (North Mam Creek, see map E) on the western side. They rise in the plateau forming the divide between them and the head of the North Fork of the Gunnison. The eastern branch is formed by two streams, whose courses are almost parallel. Between the East Fork and Roaring Fork there is a smaller creek (c creek, Grand River), which rises in a mass of rounded hills, which I referred to when speaking of the hog- backs on the west side of Roaring Fork. Between this creek and the plateau south of the canon theie are several folds, the axes of which are parallel, each being northwest and southeast. The rocks underlying the valley are all of Cretaceous age, capped irregularly in places with basalt, especially on the divide. Here the strata are almost horizontal, inclining, if at all, only a few degrees toward the west in the eastern portion. The line of hog-backs before referred to, extending along the lower side of the Grand from station No. 16, through station 18, and cross- ing the river, forms the side of a synclinal fold, the axis of which is, partially at-least, occupied by a creek (c, Grand River). The dip of the strata is southwest, inclining at an angle ofabout 15°; this increases as we go toward the Grand, being about 60° there. Station 20 is on the opposite side of the fold, the dip of the sandstones there being northeast at an angle of 15° to 20°. From station No. 19 to 22 there is a mesa covered with basaltic bowlders. _I am inclined to think also that there is a capping of the same material. The bowlders are derived from the hills near the divide. The mesa is about a mile wide and slopes gently toward the Grand. It is about 400 feet above the valley of the creek at the forks below station No. 19. At station tion No. 22 it is 800 feet high. Between the forks of the large creek east of North Mam Creek, the ! : . 90 GEOLOGICAL SURVEY OF THE TERRITORIES. hills are capped with basalt. The elevation of station 24 is 10,642 feet, and station 25, 9,031 feet. There is but little timber here, the summits being grassy and park-like. In some few places there are pines, but cottonwoods are more abundant. In the hills east of station 24, and on the lower slope, there is scrub-oak (Quercus alba) in abundance. The small creeks rising in the Cretaceous shales we generally found strongly impregnated with alkali. The western branch of the creek perorred to above, heads in beautiful meadows. Its course here is nearly due west. After flowing in this direction for five miles it turns and flows to the northwest, gradually crossing to the western side of a low, broad anticlinal. The strata on the east incline 5° to the northeast, and on the opposite side from 5° to 10° in the opposite direction. Beyond, the beds probably become horizontal, as seen in the high white cliffs east of station No. 48, on the edge of the plateau. In looking down upon this valley from the hills bordering it, it ap- pears more open than it really is, for we find that it has numerous hills or buttes in which the sandstones outcrop. They are gray, chocolate- colored, and greenish. We were not able to visit them, but noted them from the stations on the east side and from the plateau. We were not on the Grand River in this valley nor on North Mam Creek, which joins it above the cation. North Mam Creek flows along the eastern edge of the plateau from which some of its branches are de- rived. Its general course is north 15° east. The branches of the Grand from the south in the cation valley north of the plateau are all small and unimportant, simply draining the pla- teau. The next branch of importance is Plateau Creek flowing into the Grand 50 or 60 miles below the head of the canon. It is a stream of con- siderable size, deriving its water principally from the mesa divide on the south, the branches heading in the plateau of station 48, carrying water only in the spring and early summer. There are two principal streams uniting to form the creek, one (f creek, map E), having its sources opposite those of the northern branches ~ of the North Fork of the Gunnison, and the other (g creek, map 5), rising more to the north and eastward, opposite the head of North Mam Creek. The branch first mentioned is the largest. Its course is generally north. A few miles above its mouth, however, it turns abruptly and flows west- ward, parallel to the other branch, leaving a flat-topped terrace between. It rises on the divide, in beautiful park-like meadows, among low hills whoserounded outlines are covered with groves of quaking aspens whose foliage in the fall of the year is of a rich golden hue, contrasting boldly with the dark green of the pines found on the higher points. These groves abound in game, and are favorite hunting-grounds of the Indians. We found their trails leading in almost ‘every direction. Near the head of the creek are outcrops of soft shaly beds covered in some places with basalt which forms rough points reaching above the general level. In the valleys the soil is made of the débris from the shales mingled with pebbles from the erosion of the basaltic layer which once formed a capping to the plateau. Scattered over it are chips of chalcedony and agate. The sedimentary beds are nearly horizontal. As we go down the valley we find the creek cutting deeper and deeper into the soft strata, leaving high terraces between the branches. Between camp 44 and camp 45 the river falls 2,583 feet, which is about 200 feet per mile. In the lower part of the valley there are outcrops of soft gray sand- stones. The terraces are partially covered with scrub-oak, which make traveling somewhat difficult. The other branch has a much more open ee ies s2= ; Sy: ‘r 4 ; . ue fF - 2 = A= = = ——--. Ses SS 7S Sea aS oD. o1e[ I PEALE.] GEOLOGY—GRAND RIVER—PLATEAU CREEK. on valley. It rises among low hills, and has a much more gradual fall to its mouth. It is about 24 miles in length, and forms a portion of the boundary-line of the plateau of station 48. Between the parallel por- tions of the two streams just described there is a terrace, the height of which is about 80 feet, at the bend of the first branch. It is about a mile wide here and slopes to the forks, where it terminates in a point, the entire length of the bench being about seven miles. It is covered with good bunch-grass, and has evidently been used by the Indians as a erazing-ground for cattle. The plateau between this creek and the Grand River is approximately triangular in shape, the base being on the eastern side. Here it is 15 miles in width. To the west it gradually terminates in a*ridge, which extends between the two streams. Its length is 15 miles, and its mean elevation, where the general level is best preserved, is about 10,200 feet. It was once, doubtless, continuous with the mesa or plateau which still exists to the southward. Erosion has isolated it. The covering of basalt which once covered it has been partially removed. The remnants left reach from 200 to 250 feet above the general level, forming monument-like points that are visible from a great distance. Station 48 was located on one of these points, a conical mass 248 feet high. The eastern edge of the plateau, as I have already men- tioned, has steep bluffs, overlooking a broad valley. On the north side, also. are bluffs, which as we go down the Grand become less steep, a num- ber of small streams cutting them into small hills. Toward the eastern side the beds are nearly horizontal, but as we go west we find that there is‘a slight dip to the east, or perhaps a little north of east. The south- ern side of ghe plateau, near station 48, has a number of creeks draining it, the courses of which are nearly parallel, flowing south. Between them are Sharp ridges, at the base of which gray and pinkish sandstones outcrop. On top are light clayey beds and interlaminated hardened shales, weathering a white color, thus giving the bluffs a unique appear- ance, aS seen from a distance. Underneath the basalt, the beds are concealed even on the edges of the plateau. As we go down the creek the valley widens on both sides. On the south are drift-covered ter- races sloping from the divide. On the north side are low bluffs, close to the river,in which pink and yellowish strata outcrop. These beds are cut into terraces, beyond which are bluffs of variegated sandstones, passing above into light-colored shales. On the latter, station 50 is located. From station 50 to the Grand the descent is at first rather abrupt. Then there is a gradual slope broken up by the drainage into low buttes. The Grand has a broad bottom, through which it flows sluggishly. South of the station the country is very nearly the same. There are magnificenteexposures of the strata, which are inclined but slightly. On the north side of Plateau Creek are bluffs of sandstone, through which the stream cuts rapidly to soft shales, which weather in the most pecu- liar manner,as shown in one of the illustrations, Plate V. Above the black argillaceous columns are yellow sandstones, and the débris from them has fallen down, capping the summits of the pillars. Below, still lower beds are shown, until a belt of red sandstone is seen opposite Mesa(a)Creek. Ithere enters a caiion, in which it keeps until it joins the Grand. Almost all the creeksin this region cut profound cafions ; even the smallest rivulets cut gullies from eight to twenty feet deep. _ The terraces are covered with basaltic bowlders, and are almost des- titute of vegetation. Good grass, however, is found in the alluvial bot- toms bordering the creek. Scrub-oak and stunted cedars are found on the hills. The cafion on Plateau Creek is eight miles long. Below its mouth, 92 GEOLOGICAL SURVEY OF THE TERRITORIES. the Grand and its branches cut fearful-looking chasms in the soft rocks. Looking down upon them it is hard to trace the courses of the streams, as it appears to be an inextricable maze of gorges. - There is great variety in the colors; reds, greens, grays, ‘yellows, mingle with chocolate-browns, and white, in parallel lines, which repeat themselves in the different layers. At the head of the cafion of Plateau Creek the Indian trail we had been following leaves the creek, goes up Mesa Creek, and skirting iS edge of the mesa, leads down into the valley of the Gunnison. The course of Grand River below the mouth of Plateau Gree is oan erally southwest, and sometimes due south. It flows in this direction until it comes out into the broad valle in which it is joined by the Gunnison. It emerges from the cafion by cut- ting its way across a line of hog-backs, almost at right angles to the strike of the strata, the beds dipping about northeast at an angle of 10° to 15°. Plate VI represents the bluff on the north side of the river, as it comes from the cafion into the broad valley. The numbers in the following section correspond with those in the illustration. BASE. . Black and yellow shaly beds. . Yellow sandstone. . Yellow shaly beds. : . Sandstones, . Shales. . Sandstone with pinkish hue. This section was made from the opposite side of the Grand, and could not, therefore, be made in greater detail. The beds were measured by augles taken with the gradienter. The height of the bluff as thus deter- mined is 1,890 feet. On the south side of the river the inclination of the beds causes them to disappear, while higher ones show beneath the basalt of the mesa. The slopes, reaching from the edge of the mesa in’ terraces, are covered with basaltic bowlders, among which we found numbers of moss-agates (none of good quality, however) and pieces of chalcedony. West of the lineof hog-backs, which extend toward the northwest from the Grand, the valley is about eighteen miles in width, reaching to the northwest as far as could be seen. Near the Grand, before the Gunnison comes in, it is very flat and covered with spots of alkali. On the south side of the Grand, in the angle between it and the Gunnison, are terraces, the first of which is one hundred feet high, and the second nearly two hundred feet. The contrast between the two rivers is quite marked. The Grand has nearly twice the volume of the Gunnison, and and carries a vast quantity of mud with it. Wherever we reached the Grand throughout the entire season it was muddy. The reason is, that along the river there are many exposures of soft shales and clays. The Gunnison, on the other hand, isa clear stream, and remains so except | when there are heavy rains, when it becomes very turbid in the lower portion of its course. The divide between the Grand and Gunnison Rivers has been so often referred to in this chapter that only a few more words:are necessary to complete its description. In the Elk Mountains the line of the water- shed is very irregular, the mountains rising in sharp peaks, at the bases of which the streams head in amphitheaters, sharp ridges connecting OS Oe Coho LE i, TAN wy Yee RNS HS WN NS WING / oC ij i ‘ at - dy , . Naat my oie Blu? ov Grand River near the Mouth of the Gunnison. Pwo ue i , ie PEALE.] GEOLOGY—DIVIDE WEST OF ELK MOUNTAINS. 93 the peaks and separating the various streams. This portion of the divide, however, was in the district of 1873, and we have to do here with the portion west of the Elk Mountains, where it presents characters en- tirely different, being mostly a plateau, from the fact that the beds un- derlying it are almost horizontal and covered with a flow of basalt. The plateau character is best shown toward the west, where the basaltic capping is for the most part intact. West of Rock Creek, at the head of the North Fork of the Gunnison, the plateau is broken into low rolling hills, of which the general level is very nearly the same. The basaltic capping here is very irregular and difficult to define, as a great portion of it has been removed by ero- sion. The hills and also the beds of the streams are covered with round masses of the rock. At station 45 there is more basalt in place. The streams rising near have their origin in small lakes. All over the plateau these lakelets may be found, and along the creeks are beautiful meadows. The timber on the plateau is pine and quaking aspens (Popu- lus tremuloides). There is good grass in most of the valleys. The western edge of the plateau is somewhat irregular but sharply defined, forming a bluff edge of from two hundred tofour hundred feet in height. Tt is underlaid with sandstones, as will be shown in the sections given in a Subsequent portion of the report. CHAPTER III. SURFACE GEOLOGY—GUNNISON RIVER AND ITS TRIBUTARIES. Gunnison River is the principal branch of the Grand, on the south side. It rises on the western side of the Sawatch range, opposite the Arkansas River, and on the southern side of the Elk Mountains, oppo- © site Roaring Fork. Its total course has a length of about two hundred miles, the average rate of fall per mile being about thirty feet. In Gunnison’s and in Frémont’s reports it is called the Grand. In the West, however, it is now known as the Gunnison River, the name Grand being given to the principal stream, as already mentioned in a previous chapter. The principal branches of the Gunnison on the south are Cochetopa Creek, Lake Creek, Cebolla Créek, and Uncom- pahgre River. Those on the north, in our district of this year, are Ohio Creek, Smith’s Fork, and the North Fork. The entire area drained by all the branches on the north is about twenty-six hundred square miles. From the mouth of Cochetopa Creek, the Gunnison flows a few degrees south of west, to Lake Fork; here it changes and flows west, gradually turning to the northwest until it is opposite Station 80, a distance of nearly thirty miles; when it again turns and flows nearly due north to the mouth of the North Fork; where it turns abruptly and flows west to the head of what the Indians call Unaweep Canton. * Its course thence to its mouth is generally northwest. There are three large caflons and several small ones in the course of the river, which will be described as we reach them in going down the stream. The upper one is in granitic rocks, and was described last year. The drainage of the streams uniting to form the Gunnison near its head flows in two directions, viz, southeast or south-southeast, and southwest. In this part of its course it is within last year’s district, and will be found described in the report for 1873. Our work last year extended as far west as Slate River, and. we com- mence this year, therefore, with Ohio Creek, the next stream coming into the Gunnison on the north side. In an air-line, from the head of Ohio Creek to its mouth the distance is twenty-two miles. The actual length, however, is nearer thirty miles. It has its origin in a group of isolated peaks that mark the termination of the Elk Mountains to the westward. Its sources are opposite those of Slate River on the north and east,-and those of Anthracite Creek, a tributary of the North Fork of the Gunnison, on the northwest. It has two forks which unite below a high sugar-loaf peak of porphyritic trachyte, station 30. The western branches have their origin in a group of mountains made up almost entirely of breccia, which in all probability rests on sandstones of Cretaceous age. The most northern of these streams flows along the southern edge of a short range of sharp peaks, whose slopes are destitute of timber, and which form a serrated edge along the summit. This mass is composed of porphyritic trachyte and forms a portion of the divide between * Pacific Railroad Report, vol. ii. 94 PEALE] GEOLOGY—OHIO CREEK—GUNNISON RIVER. 95 Ohio Creek and Anthracite Creek. A trail crosses through alow pass from the head of the latter creek and keeps down Ohio Creek and then follows up Cochetopa Creek to the Los Pinos agency. This is one of the main Indian lodge-pole trails, connecting Los Pinos wtth the White River agency. Between Kast River and Ohio Creek are two mesas, isolated one from the other and underlaid by Cretaceous shales and sandstones. These mesas are composed of trachyte, judging from the débris covering the slopes west of Ohio Creek.« The trachyte is probably of the same char- acter as that on the opposite side of East River noted in last year’s re- port,* a light purplish rock. As I have already mentioned, the hills on the west side of Ohio Creek are made up almost entirely of breccia. I will refer to it particularly in a subsequent portion of the report. I think, judging from several outcrops seen on some of the western branches of the creek, that it rests throughout the greater part of its extent upon sandstones. The western branches rise in these hills and cut deeply into the brec- cia, which seems to yield readily to the action of water. It appears to be in layers, and erosion has worn it intofantastic forms. In places, there are castellated masses from which towers and minarets rise; while in others, huge buttresses stand out prominently against the sky. Station No. 31 is situated in the midst of this mass of breccia. (See map D). The valley of Ohio Creek is from a mile to two miles in width and has a beautiful grassy bottom, with groves of cottonwoods. The hills on the west are heavily timbered with pines, extending down the ridges between the branches. On the lower slopes near the creek there is sage- brush (Artemisia). The valley of the Gunnison above the mouth of Ohio Creek is very wide, extending from a short distance below the mouth of Slate River to Cochetopa Creek, a distance of ten or twelve miles. It is from four to seven miles in width. The river-bottom in places seems to be quite fertile, and at one place we found a garden in which potatoes, beans, turnips, cabbage, and lettuce had been successfully raised during the season. The southeast side of the valley, reaching toward Cochetopa Creek, is rather sterile-looking, there being but little soil. It is very level and covered with pebbies derived from the Elk Mountains. There is a sparse growth of grass and low sage-brush. ‘The Gunnison here is a rapid and very clear stream of a hundred or a hundred and fitty feet width. It keeps close to the bluffs of breccia below the mouth of Ohio Creek. This valley is the site of a new town called Gunnison City. There were half a dozen log-cabins, most of them in an unfinished state and _ without inhabitants. The only persons we found living in the valley were the two men who have charge of the cattle for the Indians of Los Pinos agency. They were at the cattle-camp, a short distance above Cochetopa Creek. Below Cochetopa Creek the valley again expands into a grassy meadow, from which the river enters a caiion. Men from the agency were busy cutting grass in this meadow while we were there. The hay made is for the use of the agency and the cattle-camp. The cattle are allowed to run wild among the hills throughout the year and seem to do well. The country is much better adapted to stock-rais- ing than for agricultural purposes. The elevation of the cattle-camp is 7,743 feet. The lower valley is about four miles long and two miles wide in its greatest width. On the‘northern side the breccia forms the boundary, * Page 249, Report 1873. 96 GEOLOGICAL SURVEY OF THE TERRITORIES. trachyte capping it as we go toward the hills. On the south side the rocks are gneissic, as they also are in the cation. At the upper end of . the'valley, on the north side, is an outcrop of soft yellowish gray sand- stone. Farther down the breccia, instead of resting on this sandstone, appears to be directly upon the schists. Atstation 71, however, between the schists and the breccia there is a belt of sandstone that seems to have been metamorphosed» Above the breccia there is a capping of trachyte. The cation is only about a mile and a half*in length, and in it the river has rather a tortuous course, flowing at first south of west and afterwards north of west. The walls are not very high, never exceeding 300 feet. Below, the river is in another valley similar to the one above. This, however, is not as large, being only two miles long and a mile wide in the widest portion. It is not so well grassed as the valley above. The schists still compose the hills on the lower side, while on the north there are sandstones, breccia, and trachyte in long mesa-like ridges that extend from the margin of the valley toward the hills in which station 31 is situated. Leaving this valley the river again goes into cafion and keeps so almost all the way to the mouth of the Lake Fork, broken only by small and unimportant valleys. The rocks in which the river-channel lies are schists, and the walls never exceed about one hundred and fifty feet in height. This granitic rock forms.a narrow strip, leaving a bench or shelf on both sides of the river, reaching back to the edge of the bluffs, On top of the schists, forming the base of the bluff, are the sand- stones that probably belong to the Dakota group. As we proceed down the river we find on top of these, black and yellow shales, above which is the breccia to which I have so frequently referred in this chapter. This, in a great many places, has weathered into sharp pinnacles and towers. It is capped with obsidian and trachyte. A section of thebluffs will be given in another place, when the differ- ent layers will be particularly described. These bluffs are on both sides of the river, and form the edge of the mesas that are so characteristic of this part of the valley of the Gun- nison, extending back from the river on both sides. Below station 71 the top of the mesa is about 500 feet above the river-level, and at station 73 it has increased to 1,230 feet, the general surface really remaining at the same level on both sides, while the river in its progress has cut deeper and deeper, making the bluffs nearly twice as high. This height is still greater farther below, as we will find when we speak of the canon. The streams joining the Gunnison cut deeply into the surface, divid- ing the original mesa into many others. The cations thus formed have almost perpendicular walls. There appeared to be more than one layer of the trachyte, for, from the edge of the mesa a higher outcrop can beseen. I was notable this year to determine definitely therelations between the trachytic flows and the breccia on the mountainous mass around station 31. Another year I hope to explain it. Above the mouth of the Lake Fork, the Gunnison flows through a small open valley covered with grass and sage-brush, in which it is joined by a branch of some size from the north. From this valley the river plunges into the largest caiion in its entire course. Lake Fork is itself in a deep cafion, cut through dark, micaceous schists, and until one comes to the edge of the gorge, he has no idea of its size or extent. Gunnison’s wagon-trail is obliged to cross it a long way back from the river, and come down the stream on the opposite side. Plate Vil fig 1. Section’ G SAG 2 ae = > LIAPY UOSTULMIM) UIGUD) PUBL) . GL UOMMIG KE <= Station 38. PEALE.] GEOLOGY—GUNNISON CANON—SMITH’S FORK. we The country between Lake Fork and the Uncompahgre River is rough and rugged. The streams cut deep cafions to join the Gunnison. Mountain Creek, Blue Creek, and Cebolia Creek are the principal streams draining this region. Blue Creek, to which Lhave just referred, is placed on Gunnison’s map, as a branch of Cebolla, whereas it is a tributary of the Gunnison. The mesas are found on Mountain Creek, and until we reach Cebolla creek. Here we meet with cretaceous shales, seeming to be horizontal, and resting on granite. The granite in places has trachyte resting on it. I noticed it on the hills east of Cebolla Creek. The great cation of the Gunnison is about fifty miles long. In it the course of the river at first is west; it gradually changes toward the north, and at station 80 flows northwest, gradually becoming due north, which course it keeps rather uniformly to the mouth of the North Fork. From the head of the canon to the mouth of Smith’s Fork the main portion is cut in dark micaceous schists. It has its great- est depth, perhaps, opposite station 77; the height from the water to the top of the mesa on which the station was located being about 3,000 feet. The granitic portion is about 2,000 feet deep. It was, oi course, impossible to reach the edge of the river while in the cafion, so that these figures are not perfectly accurate. They are obtained by comparing the heights of stations 77 and 78 with that of camp No. 55, on Cebolla Creek, about one mile above its mouth, and ailow- ing for the fall of the river between the two points. The error, if any, would, therefore, be very small and in favor of greater depth. The section across the river, through stations 77 and 78, is shown in Figure 2, Plate VII. On the west side of the river is a plateau about four miles in width and thirteen miles long. Its elevation above the river is 2,500 to 3,000 feet. It is composed of schists, and the top seems to have a gentle slope to the eastward. It seems to have had in places a capping of trachyte. Kast of Cebolla Creek, on the granite hills, a portion of this trachyte stillremains. Tothe northward the plateau runs to apoint, the termina- tion being marked by ahigh conical point of granite. Beyond this, are red sandstones (Triassic), with superimposed Jurassic and Cretaceous strata, as seen from station No. 80, on the opposite sideof the river. Fig.1, Plate VII, shows a section through station 80. It will beseen that the granite forms a sort of shelf along the river, on which the sedimentary forma- tions rest, having bluff-like edges a short distance farther back. These beds incline at a small angle (about 5°), causing the country to slope gently toward Smith’s Fork, which here flows.almost parailel to the Gunnison. The illustration, Fig. 1, carries the section across Smith’s Fork. Beneath station 80 is an outcrop of the Red Beds. Where the section crosses Smith’s Fork, the latter stream does not cut below the Dakota group (No.1). Near the mouth, however, it cuts through the Red Beds reaching the granite. Smith’s Fork joins the Gunnison as the latter emerges from the gran- itic portion of its cafion, and cuts across the strata into the Cretaceous Sandstones. It rises in the group of trachytic peaks that I have already referred to as terminating the Elk Mountains to the westward. Before it leaves these peaks there are outcrops of Cretaceous shales seen pear the water’s edge, on the main creek at first, but afterward spreading out and covering wider areas. After it is fairly out of the mountains it flows across the Upper Cretaceous formation, and gradually cuts through the sandstone of No. 1, which forms blufts extending along its course from the mouth of the Southern Fork to the mouth. (See map B). 7H 98 GEOLOGICAL SURVEY OF THE TERRITORIES. The Southern branch of Smith’s Fork rises in a comparatively open country, opposite the creek which forms the boundary of the last mesa on the upper side of the Gunnison. It lies almost entirely in the Upper Cretaceous formations, which are exposed in low hills covered with cedars and sage-brush. At one place it cuts a cation through No. 1, from which it comes into the upper beds, not touching the Dakota group again until it joins the North Fork. This cafion is only two miles long, and must have been determined by a fracture caused by folding. On the west side the inclination of the sandstone is only 5°, while on the east it is 15° to 20°. In the latter there is only a small triangular area of No. 1 exposed, the base of the triangle resting on the stream. Opposite the mouth of this fork is a hill of trachyte, which may have had something to do with the fold we have noticed. About three miles above this hill, on the north side.of the North Fork, there is a finger-like rock (trachyte) projecting from the Cretaceous shales. From the june- tion of the forks to the mouth is a distance of thirteen miles, in which the river is in canonor acannon like valley, the height of the cliffs on either side ranging from about two or three hundred feet at the head to nearly fifteen hundred near the mouth. The walls are very nearly vertical, but they do not rise immediately from the edge of the river, there being a valley between the bluffs, about a quarter of a mile wide, which continues al- most to the mouth of the river as a fertile bottom, groves of cottonwoods fringing the banks of the stream. Near its mouth the river cuts a narrow gorge in the granitic rocks, the level of the river being some distance below the general level of the ‘bottom of the cation. Map B shows the geology of the region about the mouth of Smith’s Fork, and the lines of the sections H, G, K, L, and I. The North Fork joins the Gunnison three and a half miles below the mouth of Smith’s Fork.. The course of the Gunnison between the two streams is nearly due north. On station 81 the strata have a dip east of north, while on the opposite side of the Gunnison the inclina- tion is west of north, showing, what is plainly seen from the station, that there is a. curving of the strata. Smith’s Fork flows almost in the direc- tion of the strike of the beds on its,right side, while the Gunnison, after the union of the two, cuts across the strata almost at right angles to the strike. Where the North Fork comes in the course is again changed, the river then taking the course of North Fork, which is nearly due west. The North Fork is the principal tributary of the Gunnison, its general course, aS I have already indicated, being about west. It drains a large area, and is formed by two branches, one heading opposite Rock Creek and other tributaries of the Grand, and the other having its sources opposite Ohio Creek and Slate River, in the group of trachytie peaks to which I have already alluded several times. The latter branch, on the map accompanying a report of Lieutenant Ruffner,* at its head is called Anthracite Creek, and a short distance below Bah River. Thename “ Anthracite” was given trom the discovery here by prospectors of a bed of coal, of excellent quality. I will refer to this coal again in another part of the report. We have retained the name, but instead of applying the name to only a portion of the creek, have given it to its entire length. In regard to the Bah, Mr. H. G. Prout} says, “‘The Bah is said to empty into Grand (Gunnison) River below the Lake Fork.” He therefore evidently refers to the North Fork, * Report of a Reconnaissance in the Ute Country, in 1873, by Lieut. E. H. Ruffner, Corps of Engineers. t Ibid, page 40. PEALE.) GEOLOGY—ANTHRACITE CREEK—COAL CREEK. 39 for which he says the Indian nameis Bah. Bah, or more properly Pah, is the Ute word for water. Gunnison’s map* gives itthe name of North Fork, which is the name in common use, and therefore we retain it. The group of mountains about the sources of Anthracite Creek were named by Lieutenant Ruffnert the Philosophers’ Monuments, and the names of Owen, Spencer, Huxley, Mill, and Carpenter given to some of the most prominent peaks. His Mount Richard Owen probably corre- sponds to our station No. 32. Geologically this whole region about the sources of Slate River, Rock Creek, Ohio Creek, and the North Fork of the Gunnison is exceedingly complicated. The Cretaceous formations which prevail here seem to have been disturbed by igneous eruptions, and they are found at places in great confusion, dipping in almost every direction and pene- trated by numerous dikes. Cretaceous shales, mingled with trachyte, are found on the summits of some of the highest peaks. It is therefore difficuit to get at the exact thickness of the strata or to tell the exact horizon to which beds ought to be referred, as they are vroken apart -and very much metamorphosed. The country is very rough and rugged, the peaks being high and often very difficult of ascent. It will require some time to work this region up in detail, and close and careful study will be required to reduce it toa system. Station No. 32 is composed principally of metamorphosed Cretaceous shales, intersected by dikes. A large dike crosses Anthracite Creek, having a course from station 32, South 22° West. Southeast of the station is a ridge of Cretaceous strata which heads a branch of Anthracite Creek on one side close by one of the sources of Ohio Creek, and on the other overlooks the sources of several branches of Slate River. All these streams rise in amphitheaters, the edges of the strata forming steps, rising one above the other. The™ streams rise in beautiful emerald lakelets. The course of this branch of Anthracite Creek at first is nearly due south. It then curves around station 32 aud flows northwest for ten miles, when it turns abruptly around a sugar-loaf-shaped mountain and flows west, through a canon cut principally in gray sandstone. In this canton itis joined by the west- ern fork, Coal Creek, when it again changes its course and flows north for three miles to the North Fork. The isolated peak around which Anthracite Creek flows was named Marcellina by a party of prospectors that we met on North Fork. It is composed of a light-gray porphyritic trachyte. It answers the description of Mount Huxley in Lieutenant Ruftner’s report,i but on the accompany- ing map Mount Huxley is located on the opposite side of the creek. The western branch of Anthracite Creek, Coal Creek, rises generally on the rim of a basin of Cretacecus shales and sandstones (see map C), which is bordered by hills of trachyte and breccia, the latter beiag on the eastern side, and an extension from station 31. For some distance above its junction with the eastern fork it flows through a cafion, of which the walls are about a thousand feet in vertical height. The sand- Stones and shales composing them are perhaps slightly inclined toward . the northeast, not more than 3° to 5°. There are outcrops of coal at various points along the western fork, but the coal is of poorer quality than that on the eastern fork. The other stream, which unites with Anthracite Creek to form the main North Fork, rises opposite Rock Creek and the branches of the * Pacific Railroad Report, vol. xi. pepo of a Reconnaissance, &c., by Lieut. E. H. Ruffner, Corps of Engineers, page 40, t Ibid., Page 41. 100 GEOLOGICAL SURVEY OF THE TERRITORIES. Grand, immediately opposite the plateau in which station 48 was lo- cated. Its course is nearly south, on a line with Coal Creek. The valley is comparatively narrow, there being but few open bottoms along its course. The slopes of the hills on either side are well timbered with pines and cottonwoods. Near the head of the main creek there are large bowlders of a black basalt, derived, in all probability, from the layer which once covered the entire divide. While on this creek we met a party of prospectors, who said they had found indications of gold along the stream, but not in any very great quantity. The divide between Rock Creek and this branch of the North Fork is a sharp ridge of Cretaceous sandstones, reaching above the timber-line. The strata dip about 15° to the west, the angle decreasing on crossing the North Fork, until they becomealmost horizontal in the plateau divide between North Fork of the Gunnison and Grand River. Station 26 was located on this ridge. The lines of outcrop between the station and Sopris peak are the prolongation of the hog-backs on the west side of Roaring Fork. The rock on the summit of station 26 is a compact greenish-gray sandstone, somewhat laminated, and containing in the lower part frag- ments of stems and leaves, and particles of carbonaceous material. The most careful search revealed nothing perfect enough foridentification. Be- low this sandstone is a narrow band of dark-colored, very compact lime- stone, of a reddish-brown color on the weathered surfaces. Next below is a coarse textured, soft, gray sandstone, which seemed to continue to the - base of the amphitheater which the station overlooked. Near the base ofthe slope we ascended, I noticed an outcrop of con- glomerate in which the pebbles were of a rock very much like that form- ing the nucleas of the Elk Mountains. The matrix was siliceous. What the relations of this bed were to the sandstones I could not de- termine, as the slopes were covered with a heavy growth of timber, and the underlying beds were for the most part covered with débris. The pebbles were rounded and evidently water-worn. South of station 26 the strike curves to the eastward, the dip changing more and more toward the southwest. The line of outcrop of the Creta- ceous beds crosses Rock Creek into the Elk Mountains, wherethey become very much faulted and upturned. In this portion of the Elk Mountains Dr. Hayden made a more detailed survey, and to his report and the re- port of Mr. Holmes, the reader is referred for the geology of Rock Creek and the adjacent peaks. Station 33 was located south of station 26 on one of a group of high peaks, rising from a mass of trachyte resembling that composing the mountains between Anthracite Creek and the head of Ohio Creek near station 32. The western slope of this mass .is extremely steep, the sandstone reaching to the base , almost horizontal in position. At the northern end, however, as seen irom a distance, the strataappear to dip to the northeast at an angle of about 40°, so that there would seem to bea synclinal fold between this point and the ridge, extending from station 26. A branch of North Fork rises hereand flows nearly due west. Near its mouth the beds are also inclined towards the northwest, although the angle is only about 5°. At the southern end of the mass in which station 33 is situated, on Anthracite Creek, the sandstones are tipped up, dipping north 54° west atanangleof15°. Dikesoftrachyte penetrate thesandstones. The branch ot North Fork that we have just been considering, after the union of the Nt Rees. Fe | aeaeys | Ls Yy Y UY Y lf Yj hy if 1 et 4 in : ; } : PEALE] GEOLOGY—NORTH FORK OF THE GUNNISON. 101 streams heading in the plateau, flows for a short distance through a beautiful grassy valley, from which the country on the west rises in a plateau which is timbered on the slopes. At the lower end of the valley the stream gradually cuts deeper and deeper into the sandstones, until, at the point where it meets Anthracite Creek, it is about a thousand feet below the general level. All the branches here, even the smallest, cut these canons, leaving mesas or tabies.- between, in which the strata are nearly horizontal, thus giving them about the same general level. After the union of the two main creeks, the North Fork flows a little south of west, almost at right angles to the former courses, in a cation which is from 1,500 to 2,000 feet deep. This canon is about fifteen miles long. In the lower part the river gradually turns to the southward, finally emerging into a rather broad, open valley extending on the lower side to the foot of the hills on which stations 38 and 39 are located. The valley becomes wider as we go toward Smith’s Fork. It is compara- tively open, being broken only by low hills or buttes of yellowish and gray shales, all belonging to the Cretaceous formation. These buttes have a scattered growth of stunted cedars and sage-brush. The soil is impregnated with alkali, and generally sterile. The small streams cut deep gulleys in the soft beds. As the river emerges from the cafion the mesas on the south side end abruptly in steep bluffs, just north of station 39. Stations 38 and 39 belong to the tracbytic group, to which I have already so often referred. They are beautiful examples of moun- tain forms, rising in sharp conical points. Station 38 rises 4,000 feet above the general level of the valley which it overlooks. As already described, there is a gradual slope from the Gunnison to Smith’s Fork, the sandstone of the Dakota group forming the floor. Crossing Smith’s Fork, the softer beds, which we have already described, form lines of buttes. Along the North Fork there are outcrops of black shales, in which the general dip is to the northeast. On the north side of the river is a series of terraces sloping from the basaltic-capped mesa which here forms the divide between the Grand and Gunnison Rivers. Leaving the mesa cafion the North Fork turns still more toward the ‘south, and flows southwest to within about four miles of its mouth, when its course becomes due west. In this valley the river winds in graceful curves, outlined in the most distinct manner, as seen from the moun- tains and plateau, by the fringes of cottonwoods on its banks. Just before it turns to the westward it enters a cation. The walls, at first, are mere bluffs, cut in the black shales that lie immediately above the Dakota sandstone. By the time it joins the Gunnison it has cut pretty deeply into the Dakota group. The river in this part of its course is parallel with Smith’s Fork, and joins the Gunnison in the canon at right angles to the former course of that stream. The Gunnison, peeves; turns and flows to the westward in the direct line of the North ork. This part of the cafion of the Gunnison is ten miles in length and with walls from 400 to 500 feet high. Although in many places the bluffs rise in sheer precipices from the liver’s edge, in others there are alluvial bottoms, sometimes on one side and sometimes on the other. The general course Is about due west. Fig. 3, Plate VIII, represents a section across the Gunnison through the line E F, on map By At a it cuts the river just above the mouth of Smith’s Fork, before it leaves the granitic caion, and at d it cuts the Tiver below the mouth of the North Fork. It will be seen that there is 102 GEOLOGICAL SURVEY OF THE TERRITORIES. a slight synclinal fold between ¢ and d, which is more marked farther west, aS Shown in Fig. 2, which is a section across the Gunnison just before it leaves the canon, on the line GH. The following is the sec- tion represented in Fig. 3, the figures corresponding with section L. SECTION. . Granite reaching to edge of the river. . Red sandstone (Triassic ?). . Greenish and gray shales and sandstones (Jurassic ? ). . Shaly sandstones. . Massive sandstones. Laminated sandstones and black shales. | . Black shales. > Cretaceous. | | } Dakota group. . Dark yellow shales. . Light yellow and gray beds. 10. Terrace with light-colored shales. At ain Fig. 2, Plate VIII, the strata are seen to be curved abruptly, the river occupying the axis of an anticlinal fold. This is at the point where it leaves the canon. The fold, however, is not simply a north and south fold, for, as we see in Fig. 1, Plate VII, there is folding east and west. This is the main fold, or rather the termination of the anticlinal fold, the axis of which the Gunnison follows in the cafion above Smith’s Fork. Fig. 1 represents a section on the line I K, almost at right angles to the sections in Figs. 2 and 3. The following are the beds represented in Fig. 2 (Seetion K): OMA CP Ob 1. Shaly sandstones. : 2. Massive sandstones. } Dakota SRS IOS 1). | 3. Shales and sandstones. > Cretaceous. 4, Black shales. 5. Yellow and gray shales. 5 In Fig. 1, the following is the section (Section I): _ Sandstones of No. 1, Cretaceous. Yellowish and black shales. Fine hard brownish shales. Sef) [SM } Shales forming terraces. As we go south along the west side of the cafion of the Gunnison, we see that the dip, at first, is to the northwest, gradually coming around to the west. The connection between the Dakota group and the overlying shales seems to be broken. Opposite station 80, the Red Beds (Triassic) are seen resting on the schists. A little farther south the Dakota group is washed off, and there are simply remnants of the red sandstones left. I did not have time to visit this from the west side, and until this is done, all opinions must, to a certain extent, be conjectural. As we go farther south we find the granite plateau, before referred to, shown in Fig. 2, Plate VII, f to g, standing between the Gunnison and the valley of the Uncompahgre. Abutting against this plateau, at the head of Cedar Creek, and on the branches of Cebolla Creek, as we have already seen, the ‘Cretaceous shales are horizontal. Whether the fold noticed at the northern end of the cation becomes a Plate VII. LS 8 SS 5 : aS s a ee EEE LZ EE LEE La th Vala CBU: Zs i LM LTE oe as Fey ot hp Ue oD 7 ; oF Ta NY v J ' 7 ae So SS = a * ~ e . 1 1 Nel PF 7A A Bo -s ee Sr Ne eA ce le ea 5 = ’ (Shore “aes y pie. Vee; Figl. Section /. x ecttore & . Curnriison Brver Ins nttaln lle, pa iit ppl oad PRALE.] GEOLOGY—UNCOMPAHGRE RIVER. ee LOS fault at the southern, I am unable to say. The western side of the canon will have to be studied before the question can be decided. Leaving the canon the Gunnison keeps its westerly course for about six miles, when it makes some southing to the mouth of the Uncom- pahgre, which joins the river eight miles below the foot of the canon. The Uncompahgre is the largest tributary of the Gunnison from the south. Itrises inthe Uncompahgre Mountains (Sierra de la Plata of Gunniscn*), and has a general course a few degrees west of north. The range in which it rises is one of the finest in the Kocky Mountains. The geology will be fully treated of in Dr. Endlich’s report, the range being in the southern district. While we were in the valley of the Uncompahgre, we had a magnificent view of its snowy peaks, which stand out promimently against the sky. To the west we had a sight of the Sierra la Sal or Salt Mountains, the peaks being just visible. Near the head of the Uncompahgre there seem to be some beautiful open parks. We did not visit them, as our trail led us up Cedar Creek, one of the eastern branches of the river. We were but a few miles above the mouth of Cedar Creek, at the point where the wagon-irail crosses. “ Cedar Creek is probably dry during the greater part of the year. It rises in a plateau-like divide, opposite a small branch of Cebolla Creek, a few miles west of the mouth of the main stream. Its general course is about northwest. The upper portion of the valley is narrow and ravine- like, the slopes of the hills being covered with scrub-oak, sage, and cactus, with here and there patches of grass. This valley continues tor about ten miles, when the creek comes out into the broad valley of the Uncompahgre, which at this point has lines of buttes of light-colored clayey-beds, the debris of which forms a soft soil, in which the mules sink to their fetlocks at every step. All the small creeks, dry for the greater part of the year, cut deep gullies in this soft soil, which is almost desti- tute of vegetation. In places there is considerable effloresence of alkali, and gypsum is found abundantly throughout the valley. The buttes are found on the eastern side of the valley. (They are from two hundred to four hundred feet high, and form two lines, those nearest the cafion of the Gunnison being the highest. The buttes are not so numerous in the lower part of the valley, where the general level is bnt a few feet above the river-bed. It is more plain-like, without grass, having only a sparse growth of low sage, interspersed with spots of alkali, giving the country a most desolate aspect. Along the river is an alluvial bettom, with good grass, the river being bordered with cottonwoods, willows, and low bushes.of various kinds. This bottom becomes much wider as we descend, and is a favorite wintering place for the Ute In- dians. We found traces of their camps, while their trails run in every direction. In one place we found a field where corn had been raised, the stalks of which weve still standing. On the opposite side of the Uncompahgre the country preserves a very uniform level for ten or fifteen miles to the west and southwest, where it seems to rise in a plateau. This level country is terraced, cut by the branches of the Gunnison and Uncompahgre, which contain water only in the spring. The terraces are for the greater part desti- tute of vegetation, being coverd with pebbles, among which are scattered fragments of chalcedony and agate. They are underlaid with Creta- ceous strata, shales in the eastern part, and the sandstones of the Da- kota group toward the west, as the country rises into the plateau. The * Pacific Railroad Report, vol. ii, page 55. 104 GEOLOGICAL SURVEY OF THE TERRITORIES. latter was seen only from a distance, but it is probably similar to the - country to the west of the Gunnison, near its mouth, the streams prob- ably cutting through to the Triassic? red sandstones. On the Un- compahegre the terrace is about one hundred feet high. On the south side of the Gunnison below the mouth of the Uncom- pahegre, are three terraces. The first is 100 feet above the level of the river, the second 150 feet, and the third 200 feet. Below the junction of the Uncompahgre, the Gunnison keeps a course a few degrees south of west, until it reaches the mouth of Roubideauw’s Creek, nearly five miles below. Here it enters the lower caflon. Above Roubideau’s Creek the valley is very wide, averaging about two miles. The immediate river-bottom is also broad and overgrown with cotton- woods and low brush. There are numerous sloughs along the course of the river, and the fall per mile is very small. The river winds slug- gishly in curves that sometimes seem to approach circles. On the north side are terraces which soon form low hills or buttes reaching almost to the mesa. Theedge of the mesa stands boldly out, like the edge of a fortification-wall. Its slopes are well timbered. The buttes below, extending toward the river, are composed of yellow, gray, and whitish strata, the weathering of which gives a most curious appear- ance to the landscape. On the south side, as I have already said, there are terraces extending southward toward the Uncompahgre Moun- tains. The canon which commences at the mouth of Roubideau’s Creek, ex- tends almost to the mouth of the Gunnison. It is, therefore, about 32 miles in length, in an airline. By the Ute Indians it is called Unaweep or Red Canon,* from the deep-red sandstones that are exposed at va- rious points along its course. In the cafion the river winds considerably, and has in places neadows and even groves of cottonwood fringing it. It is not very rapid, the fall per mile being about eight feet. Although in an air-line the cation is 32 miles long, the length of the river is about forty-five miles, or perhaps a little more, if we allow for all the smaller curves. The course of the river at first for ten milesis north 60° west. It then flows due north for about three miles, when it turns, taking a course to the northwest, which it keeps generally for nearly fifteen miles, when it again bends to the west and gradually curves back again toits mouth in the Grand. The walls of the cation often rise abruptly from the water’s edge in sheer precipices, while in others there is a narrow strip between the river and the edge of the bluffs. The latter are better preserved on the eastern side, as the course of the river is nearly at right angles to the dip, which is approximately to the eastward, really a few degrees north of east. At the mouth of Roubideau’s Creek the walls are only 200 feet high, while at station 60 they are 663 feet high on the eastern side, and much higher opposite. This probably increases slightly as we go down-stream, ' but it can scarcely reach a thousand feet at any point. At first the river merely cuts through the sandstones and shales of the Dakota group (Cretaceous No. 1), as shown in a section of the bluifs given in another portion of the report. As we go down, the river gradually cuts through the base of No. 1 into the Jurassic shales and limestones; and finally, below station 62, the red sandstones (Triassic ?) appear beneath the shales. Fig. 3, Plate IX, represents a section across the Guunison through Station 60 eastward to the mesa terminating the plateau divide. It will * Vide Pacific Railroad Report, vol. II, page 57. Pofthe ian Bat aie i SRY TTS BE PRR is dee bie Beer te Girt Gian V4. esta GF Elite Be Ed, ee Pa lislige | tdi Meh aetaelie is ha aOR eng deh Hs OP the ( ieee " Wier ar} Ae) Mellon S)Ubnt ht cece Mies reir i pi ak ta AL eat } , IAI UISTUUH: [TD “XT 9@ld 22) ait: Br uomng: G by V TITLED 1 eng WLLL SAAT Pumdg) PEALE.] GEOLOGY—LOWER CANON OF GUNNISON RIVER. 105 be seen that there is a gentle slope from the edge of the cafion, and that from the edge of the mesa there is another slope, thus forming a valley between the two points. This valley is filled with Cretaceous sand- stones, shales, and marls, which, on the east side, form mesa-like buttes. There are five streams joining the Gunnison from the east in the cajion. The largest is Kahnah Creek. Most of the creeks cut deep cafions as they join the river. It will be seen, on referring to the illustration (Fig. 2, Plate IX), that there is a dip at right angles to the stream, and that thisis the greatest at the river, and decreases as we goawayin either direction. Atthe point where the section was made, the dip isonly about 5°, Farther north, on the south side of the Grand, the angle is from 15° to 20°, decreasing as we go westward or southwestward to about 5°, and also decreasing as we go toward the east. There is therefore here a monoclinal fold, the axis of which has a direction about northwest, the dip being to northeast. At station 60, the told is very gentle; but, as we have seen, to the north it is much steeper, and probably still far- ther it may become a fault. Fig. 1, Plate 1X, represents a profile of this fold as far north as we could see it from the mouth of the Gunnison. It will be in one of the districts during the next season, when it will be thoroughly investi- gated. This cation of the Gunnison seems, therefore, to have been outlined by a fissure-in the rocks caused by their folding; otherwise it would seem most natural for the river to have cut its way through the soft strata that lie between the edge of the cafion and the basaltic-capped mesa. The country to the southwest rises into a broad plateau, beyond which we could see the peaks of the Sierra la Sal. Red sandstones seem ‘to form the basis of this plateau, which is cut into profound eanons by the branches joining the Gunnison on the southwest side. This will be in the field of explorations next season, and I therefore only refer to it uere. The bluffs of the Gunnison as we approach the Grand again fall off, and do not exceed 150 feet in height. A section at this point will be found elsewhere, with a description of the beds forming it. CHAPTER LV. STRATIGRAPHY—ARCHAHAN AREAS OF EAGLE, GRAND, AND GUNNISON RIVERS. As will, perhaps, be evident from the preceding chapters, the greater portion of the country comprised in our district is underlaid with rocks of Tertiary and Cretaceous age, the older formations showing only where there are abrupt folds, and where the streams have ¢ut through the more modern beds to them. The other formations represented are the Jurassic, Triassic (?), Carbo- niferous, and Silurian. These will be referred to in subsequent chap- ters. The present chapter will be devoted to the consideration of the Archean rocks, while separate chapters will be given to the sediment- ary formations, and to the eruptive rocks of the district. The Archean areasare limited, and will be considered in the geographi- | cal order followed in the chapters on the general topographical and ge- ological features of the district. On account of the rapid and extended character of our explorations, and also the difficulty of getting at these rocks from their being cut into deep gorges by the streams, I am unable to present but few lithologi- cal details. As far as we were able to determine, tbe rocks are all meta- morphic, dark micaceous schists prevailing. Untilthey are studied in more detail, their exact age must remain undetermined, although the occurrence of the Potsdam sandstone resting on them near the head of Eagle River, and at various localities in the district of 1873, proves them to be at least of Pre-Potsdam age. No facts were obtained in regard to their relations to the metamorphic series exposed in the Front range. -Hagle River.—The metamorphie rocks through which the upper tribu- taries of Eagle River cut their courses form the northern extension of the Archean area of the Sawatch range. This area was described in last year’s (1873) report, and therefore I will do little more than refer to it here. The group of peaks of which the Holy Cross Mountain forms one of the most prominent, marks the northern end of the great Sa- watch anticlinal. The sedimentary beds curve gradually around the end of the range, the line of outcrop across which Eagle River cuts, on its way to the Grand being the direct prolongation of the line of out- crop crossing ‘Frying: Pan Creek (noticed in the report for mea page 266). a The upper portion of the Eagle is for the most part in cafion cut in these rocks. The cafion is one mainly of erosion. As far as the sedi- mentary beds are concerned it is monoclinal. They, however, are not well shown until we reach the lower part of the caton, which ends a short distance above the mouth of Roche-Moutonnée Creek. This cation, which has been partially described in a preceding portion of the report, is about two thousand feet deep, and presents all the pe- culiarities of gorges cut in gneissic or granitic rocks. The walls are steep and rugged, the river occupying the entire width of the caiion at the bottom. “The ‘trail keeps high up on the hills on the eastern side of the river. 106 PEAIE.] GEOLOGY—ARCHZAN ROCKS OF GUNNISON AND GRAND. 107 I have already said that the cafion of Eagle River is due mainly to erosion. The course was probably determined by a line of fracture of which all evidence has been removed. There is no evidence of glacial action on Eagle River, although all the branches coming from the Sawatch range show it abundantly, especially Roche-Moutonnée Creek. The valley of this creek is filled with masses of gneissic rock, beauti- fully rounded and smoothed by the glacier which once filled its valley. Grand River.—A little more than three miles below the mouth of the Eagle, the Grand enters a cafion in which it is more than probable there are outcrops of metamorphic rocks, probable gneiss and schists. To verify this opinion the bottom of the caion ought to be followed. The rocks at the entrance of the cafion are limestones, which from their position were supposed to be of Carboniferous age. The course of the river at this point is a few degrees south of west, while the limestones have a dip which in general is east. On the north side of the river it probably changes to south of east, and as we go up the creek that joins the Grand just above the cafion it changes more to the north. As we go down the cation, therefore, the sedimentary beds rise and the Archzan rocks ought to be seen beneath. This opinion is confirmed by Mr. Marvine, in whose report this caiion will be fully described. He was on the northern side and bad a much better opportunity to study its features. He says that on comparing the thickness of the sedimentary rocks with the depth of the canon it is evident that the gneiss must show be- neath. The area, he thinks, is limited, for some five miles down the cafion there is either a fault or an abrupt fold which brings the sedi- mentary beds once more to the bottom of the canon. With the excep- tion of this exceedingly limited area, I believe there are no Archean rocks shown along the course of the Grand, from the mouth of the Eagie to the mouth of the Gunnison. Gunnison River.—The head of the Gunnison River is entirely in meta- morphic rocks, which were described in the reports of last year. Below the mouth of Hast River, it flows through a belt of Cretaceous rocks, from which it again enters gneiss and schists, in which it keeps almost -entirely from the mouth of Ohio Creek to the mouth of the North Fork. The only exceptions are where the river flows through broad, meadow- like valleys, and even here there are schists underlying the river-drift and alluvium. There are but few of these meadows, and all are above the Lake Fork of the Gunnison. This belt of gneiss and schists is narrow for the most part, extending but a short distance from the edge of the river, except on the lateral branches where the metamorphic rocks are exposed some distance from the Gunnison, forming long, tongue-like areas. These lateral branches are generally in caiions, and the Gunnison itself cuts a cafion in the gneiss. Below the cattle-camp near the mouth of Cochetopa Creek, the pre- vailing rocks on the south side of the Gunnison, for a distance of more than six miles, are schists and gneiss. Receding from the river, vol- canic rocks will probably appear on top. On the north side, resting on the gneissic rocks, is a heavy layer of volcanic breccia, underlaid in places by sandstones, as evidenced by an outcrop not far below the eat- tle-camp. At station 71,the Archean belt narrows, forming the walls of @ canon, through which the Gunnison winds with rather a tortuous course. A section from station 71 to the river is shown in Fig. 3, Plate XIV. On the opposite side of the river the rocks are identical. Imme- diately on the gneiss the sandstones rest, as shownin theillustration. They 108 GEOLOGICAL SURVEY OF THE TERRITORIES. } are probably of Cretaceous age, belonging to No. 1 or Dakota group. The reason for this opinion will be given, at length,in a subsequent chap- ter. Farther down the river these sandstones increase in thickness, as shown in Fig. 1, Plate XIV, while the gneissic area is very narrow. The presence of the Dakota group, resting immediately on the Ar- chean rocks, would seem to prove that in Pre-Cretaceous timesthis Ar- _cheean area was above sea-level. What its limits were I am unable to ‘say. It was probably connected with the Sawatch range, a portion of which, as I mentioned in last year’s report, was probably above the sea- level during Pre-Cretaceous times. There wasa period of gradual sub- sidence. This commenced at least in Pre-Triassic ages; for, as shown in map B, as we approach Smith’s Fork there appear, resting on the gneiss and underlying the Dakota group, first, beds of Jurassic age, and then the Red Beds (Triassic ?). When the subsequent elevation began it is difficult to say, althouel it is altogether likely that it was Post-Cretaceous. It was probably gradual. Erosion subsequently modified the original surface. Then followed the period when the breccia and lava was poured out, concealing the underlying formations. Between Lake Creek and Cebolla Creek, there are places where the schists and gneiss seem to be capped with trachytic rock, without any intervening layers; while at lower levels, on some of the small branches of Cebolla Creek, there are shales probably of Upper Cretaceous age, abutting immediately against the gneiss and horizontal in position. Near the mouth of Cebolla Creek the schists seem to dip to southeast. Here they are very coarse, with large masses of quartz and pink feldspar. The mica is silvery (probably Muscovite). The Grand canon of the Gunnison in reality commences at the mouth of Lake Fork, although for nearly a mile it is not very deep. Below the mouth of Cebolla Creek, however, it is between 2,000 and 3,000 feet deep. The gneissic portion, opposite station 78, shown in Fig. 2, Plate VII, is 2,000 feet deep. The canon extends to the mouth of the North Fork. The Archfean area in which this cafion is cut is defined in map B, Fig. 2. Plate VII represents a section across it through stations 77 and 78, to Cedar Creek, on the line marked A B, on the map B. Fig. 1 in - the same plate is a section on the line C D on the same map. It will be noticed that the metamorphic rocks form a plateau like mass between the Gunnison River and Cedar Creek. This plateau narrows to the northwestward and ends in sharp, isolated peaks. South of station 80 there is, however, as shown on the map, a narrow Archean belt bordering the river, in which it cuts the deepest portion of its canon. This belt extends to a point below the mouth of Smith’s Fork and forms a bench on each side of the river, as seen in Fig. 1, Plate VII, ata. It will be seen in map B that the Gunnison River keeps on the eastern side of the plateau, and that on the west (Fig. 2, Plate VII, h to 2), between it and Cedar Creek the strata are horizontal, abutting against the granitic rock. The age of these beds is probably Upper Cretaceous, while the sandstones under station 77, at d and e in Fig. 1, Plate VII, represent the Dakota group (No. 1) or a portion of it. From the uniformity of level of the plateau it would appear that the sedimentary beds once extended over it and have been removed by erosion. In the section Fig. 2, Plate VII, they are shown or both sides of the river. If they once covered the plateau there must be a line of faulting along its western edge, for the level of the Upper Cretaceous beds shown there is below that of the Dakota group under station, PEALE.] GEOLOGY—GUNNISON RIVER. 109 77. Therefore the western side of the anticlinal fold must change to- a fault. If there is no fault, the force of upheaval must have been greater on the eastern side of the Archean area. If this be so it would ac- count for the fact that the Gunnison River keeps on the eastern side, as seen on the map. We would have to suppose, also, that a portion of the plateau formed an island in the Cretaceous sea. The western side of the plateau will have to be followed carefully before the exact relations can be determined. This I hope to do during next season. When we were in the Uncompahgre Valley it was late in the season; there was but little water, and, our supplies being reduced, we had to make forced marches, so that we were unable to finish the work on the western side of the canon. As already mentioned, the rest of the Archean area on the Gunnison is very narrow. It is inaccessible in most places, and I am therefore obliged to pass by it with merely this reference. The remainder of the course of the Gunnison is in sedimentary formations, which will be referred to in their appropriate places. It will be noticed from the foregoing pages that our district for 1874, unlike that of the preceding year, is entirely destitute of any metamor- phic ranges. It is true that the metamorphic rocks on the Eagle River are a continuation of those in the Sawatch range; but this portion of the district forms the boundary, as it were, between the work of the two years, It was really within the limits of one of the districts for 1873, ‘but was left unfinished. On the Gunnison and on the Grand, as we have seen, the metamorphic rocks are shown in canons where the overlying formations have been cut through. In no other parts of the district are there any rocks of Archean age. CHAPTER V. STRATIGRAPHY—PALEOZOIC FORMATIONS. This chapter will be devoted to the Paleozoic areas of the district. They are aS arule few in number and of smaii extent. As in the case of the metamorphic rocks, the Paleozoic formations are found mainly along the courses of the great arteries of the district, never extending any great distance from them. They appear there outcropping beneath the rocks of Mesozoic age which cover a large part of the region. They have been identified principally by their position and lithological char- acters. Although frequent and careful search was made for fossils, it was generally without success. In Mr. Marvine’s district organic remains were found in more abundance, especially in Carboniferous layers. I shall take them up consecutively, commencing with the Silurian, and considering them in the geographical order adopted in the preceding chapters. On the Gunnison River no sedimentary formations older than the Red Beds (Triassic?) are seen. At no point in the district was I able to get the entire thickness of the Paleozoic strata. It is, however, proba- bly about 4,800 feet. SILURIAN AGE. Although no fossils were found by me this year in the strata I shall refer to this age, still I think their position and lithological characters warrant such a reference. They rest immediately on the metamorphic rocks mentioned in the last chapter. We can say definitely that they are of a Pre-Carboniferous age. The upper portion of the series may at some future day, when more data are obtained, have to be con- sidered as Devonian. Fossils of Carboniferous age were found in the lay- ers resting immediately upon them. There was a much greater de- velopment in Mr. Marvine’s district, and further details will be found in his report. In my district, the formation is limited to Eagle River with possibly a small area on the Grand. Iam unable to make any further division of the formation than to separate the Potsdam sandstone from the layers above, the base of the latter being referable to the Calciferous epoch or Quebec group. The entire thickness of the Silurian layers is about 820 feet. PRIMORDIAL PERIOD—POTSDAM? GROUP. The Potsdam sandstone is widely distributed in the Rocky Mountains, and preserves its characteristics in widely separated localities. Dr. Hayden noticed the strata in 1856 or 1857, in the Black Hilis of Wyom- ing, and he and Professor Meek, in a paperread before the Academy of Natural Sciences, of Philadelphia,* announced the discovery of fossils, * Proceedings Academy Natural Sciences, Philadelphia, March, 1858. © 110 PEALE.] GEOLOGY—POTSDAM GROUP—CANADIAN PERIOD. 111 identifying them as belonging to the Potsdam group. Afterward Dr. Ha: den found fossils in the same formation in the Big Horn range in Dakota. In 1869* he also found, near Colorado City, fossils in layers just above, that prove the layer in which they were found to belong to the Calciferous or to the Quebec group. In the report for 1870, he also mentions the group. In 1872 Dr. Hayden and myself recognized the same group in Mon- tana, near Gailatin City.t The same year Professor Bradley recog- nized it in Utah, Idaho, and Wyoming.. Newberry § speaks of the Potsdam sandstone occurring on the Colo- rado River in Utah. Comstock|| refers to it as occurring in the Wind River Mountains. In all these localities, the general characters are very similar. In Colorado, in 1873, I discovered Potsdam sandstone in various localities, but was unable to discover any organi¢e remains in it, although just above, I found fossils referred by Professor Meek to the Quebec group. Dr. Endlich, in 1873, had outcrops of the group in his district, while the northern district was without any trace of it. During the past season I found on Hagle River a series of beds rest- ing on the gneiss and schists. From their position and lithological rela- tions to corresponding beds found by me in 1873, I referred the lower layer to the Potsdam group. The characters of these beds will be given in the sections a little farther on. Their extent in my district was limited. Eagle River.—The Potsdam group here is represented by a bed of white quartzite. Near the head of the river it is shown on both sides, dipping to the northeast at an angle of 5° to 10°. It is between 300 and 400 feet in thickness. As we go down the river it caps the ridge separating the two forks, while the gneissic rocks on the west side of the western fork are bare, the quartzite which once extended over them having been eroded away. Siill farther along, opposite the cafion, they re-appear in patches, and soon extend from the edge of the cafion in long strips between the branches of the EHagle, toward the Sawatch range, aS shown in Fig. 2, Plate I, representing the Potsdam sandstone on the gneiss. The inclination is toward the northeast, the angle being very small. At the point where the section in the illustration is made, it is shown on both sides, but as we go down the river it gradually dis- appears on the north, and appears only on the south side, where it con- tinues to the southward, curving around the end of the Sawatch range. The inclination increases, and consequently the area occupied by the Potsdam becomes much narrower, connecting with the belt that extends across Frying-Pan Oreek into the Elk Mountains. Grand River.—The only place on the Grand where the Potsdam group is likely to be seen is in the cafion between the mouth of the Eagle and the mouti of Roaring Fork. Mr. Marvine’s report will treat of this. Gunnison River.—TLhere is no exposure of this age on the Gunnison in our district for 1874. CANADIAN PERIOD—CALCIFEROUS AND QUEBEC GROUPS. Although I cannot define the limits of the groups, in ascending from the top of the Potsdam sandstone, I have thought it best to give them * Report United States Geological Survey, 1870, page 259. + Report United States Geological Survey, 1872, pages 72, 174. t Report United States Geological Survey, 1872. Report cf I’. H. Bradley. || [ves’s report of Colorado River ; page 47 of Geological Report. § Report on Northwestern Wyoming, by William A. Jones, page 106. 112 GEOLOGICAL SURVEY OF THE TERRITORIES. a separate position here. Calciferous rocks were first recognized in the Rocky Mountains in 1869 and 1870. In 1869 Professor Hayden obtained fossils from near Colorado City, of which Professor Meek says, in the Report of 1870, page 287: “‘So far as these few fossils warrant the ex- pression of an opinion respecting the age of the rock from which they were obtained, [ should be inclined to place it nearly on a parallel with the Calciferous division of the Lower Silurian.” Prof. F. H. Bradley, in 1872, recognized the Quebec group in Utah and Idaho. Theseries consisted of limestones underlaid by glauconitic sandstones. The limestones were mostly thin and contained interlaminated shales. The same year Dr. Hayden discovered beds of the same age in Montana, near Gallatin City. There we had layers of limestone also underlaid with glauconitic sand- stones. In 1873 I found near Trout Creek, in Bergen Park, Colo., pink laminated limestones underlaid with glauconitic sandstones. In them I found fossils referred by Professor Meek to the Quebec group. Anal- ogous beds had been seen in Glen Kyrie, where Professor Hayden, in 1869, found a few forms that were referred to the same group. I obtained a few indistinct fossils there in 1873. On Hagle River, above the white quartzite, that has been already treated of as belonging to the Potsdam group, we have glauconitic sandstones and quartzites that lie below a bluish limestone. No fossils were found here, and I refer the beds simply on the lithological evidence as in the following table: Quartzites with shales, glau- Quartzite. Green sandstone. bee conitic near the base. TROUT CREEK, 1873. FOUR, MILE\CREEK, 1873, | OG ee a Gneiss. Gneiss. Gueiss. Zale a | Yellow sandstone. White quartzite. S ; White quartzite. & | Pinkish sandstone. Reddish quartzite. tL: (| Dark purplish sandstone. Glauconitic sandstone. These beds are glauconitic. Quartzitic conglomerate. + Blood-red caleareous sandstone with Lingulepis and Obolus. Calciferous. a Blueish limestones with layer of quartzites near base, con- Pink limestones, containing | taining fragments of Zuom- | Light bluish limestone. Orthis « desmopleura, Conoco- phalus and Orthis desma- ryphe, Asephus, Huomphalus, pleura. Lingula, Bathyurus, and Para- doxides or Olenis. Jt will be observed that the order of the section on Trout Creek is ob- served in the other sections. Instead of sandstone, resting on the gneiss, we have quartzite, which in all of the sections is followed by beds which are glauconitic. The limestones in the section on Four-mile Creek were considerably metamorphosed, and the fossils found, very indistinct. Still, those rec- ognized identify the bed as belonging to the same horizon as the lime- stones in the section made on Trout Creek, which is of Calciferous age. It may be that in the future the glauconitie beds will have to be de- PEALE.) GEOLOGY—SILURIAN STRATA, 113 tached from the Calciferous group, and considered a part of the Pots- dam. Not being able to define the boundary between the top of the series and the next succeeding group, I cannot give the thickness. The entire thickness of the Silurian will be given in another place. Eagle River —The Calciferous group is mainly shown on the east side ~ of Eagle River, until a point below the canon is reached, when it crosses to the other side. It does not extend up the slopes as the Potsdam group does, although patches of it may be found scattered overit. It is entirely conformable to the’Potsdam group, and of course follows it across the country to the southward. Grand River.—The only locality on Grand River, within our district, for 1874, where there is any probability of the group occurring, is in the cafion between Eagle River and Roaring Fork. The cafion was not fol- lowed by us, and therefore I cannot positively assert that it is shown there. The reasons for the opinion are given in the preceding chaptcr when speaking of the probability of metamorphic rocks appearing there. Gunnison River.—The group occurs nowhere on the Gunnison River from the mouth of Ohio Creek to Grand River. REMAINDER OF THE SILURIAN. The remainder of the beds that I have included in the Silurian con- sist of limestones, which are for the most part magnesian. In one place on the eastern side of the canon of Eagle River, there is just above these limestones a bed of trachytic-looking rock, 50 or 60 feet in thickness. I was unable to trace its extent, but farther north, between some higher layers, found a bed of similar rock, which was probably derived from the same source. The following is the section of the Silurian strata, as exposed on Kagle ‘River: No. 1.—Section of Silurian strata on Eagle River. Top. Thickness. (2) Ft. In. 7. Light-bluish limestones on weathered surfaces, white and yellow. Itis- in bands of from three to eight inches thickness, with a cross frac- ture and non-fossiliferous. A great portion of these limestones are probably magnesian. At the top they are crystalline......-....---. 219 6 CALCIFEROUS GROUP: 6. Space, in the upper portion of which there is an out-crop of metamor- phosed conglomerate, seemingly composed of pieces of white quartzite and brown sandstone. The masses are irregularly shaped. The out- crop is only a few feet in thickness, and the remainder of the space is probably filled with sandstones and quartzites with perhaps a few shales. The space was so covered that the beds were all concealed. Phe-entire thickness) iss a2 ssa sssee ees et ee ae Ae 68 4 5. Milk-white quartzite, similar to that of No. 1-.---2. 0-2-2. ..22...0----- 4 9 4. Space probably filled with sandstones. .-2....----2-- .--0--)s42- 2225 =e 22 8 3. Grayish-brown laminated sandstones with a greenish coating and mud- marks on the surfaces of the lamine........2-.-...---.-----------e 98 6 2. Fine-grained, rather compact, glauconitic sandstone, somewhat lami- nated, dark brown and greenish-gray...- 2. .----- 222 ese ee ecice ee eno 10 0 PNIMORDIAL GROUP: Pe Milk-white Quartzite p< |. j-sccin, s pjonod ng so deecec poHebb epigsadas suaaae 200 TOTEM Sted fa eh a eee es OS CEC TC OEIC ee Fy Cia dy tram ea aD 1,500 The gypsiferous series is probably tipped up with the overlying beds, as represented in Fig. 1, Plate I, ate, although they are hidden by the volcanic overflow. Below the cafion they occupy the greater part of the valley. This area is indicated on the map A. It is difficult here to re- duce the strata to any order. Their softness has caused them to yield readily to eroding influences, and they have weathered into low hills, in which they are for the most part concealed. There are one or two folds in them of some extent. These I referred to in the chapter on Ragle River Valley. Besides, however, there are numerous minor foldings, which it would require more time than we could give to reduce them to * any system. Mr. Marvine will probably have some additional notes, as they extended into his district. 120 GEOLOGICAL SURVEY O# THE TERRITORIES. The sections in Plate III show the gypsiferous series below the Red Beds at the points markeda. They are probably the same beds I noticed last year* on Frying-Pan Creek, above shales and sandstones that I then referred to Carboniferous. I did not know exactly where to put the gypsiferous beds, whether to include them with the Red Beds which were exposed in the hills above or to place them with the Carboniferous. In the lower cafion of the Eagle, which extends to the mouth, the gypsiferous beds are well exposed, dipping from the river on both sides, leaving the channel in the axis of the anticlinal. Near the mouth of the river a flow of lava from the hills on the eastern side has forced the river to the opposite siele, and it has scooped out a large portion of these soft beds. The Red Beds here cap the bluffs on either side. Grand River.—The gypsiferous beds continue from Eagle River to the Grand, and follow it to within a short distance of the caflon, when the line crosses to the southwest and appears again on @ creek, at first only capping the bluffs on the east side, but eradually showing in the bed of the creek as we ascend. They do not appear again until we cross to Roaring Fork, where they show beneath the Red Beds of the hog-backs that extend along the western Sule ot the creek, below Rock Creek. They are represented atd in Fig. 2, Plate 1V. At first the series is seen only on the western side of Roaring Fork, but as we go down they grad- ually appear on the eastern side, also extending up a small braneh that comes in from the east. On the western side, at first they have a ter- race-like surface. Further down they form bluffs, on the sides of which they weather into pinnacles and spires of yellow and pink colors. They continue to the Grand, where the Red Beds appear above them on the south side, and on both sides of Roaring Fork. Below the mouth of Roaring Fork the gypsiferous beds cross the river into Mr. Marvine’s dis- trict. In Fig. 1, Plate IV, they are shown at the point e to f in the sec- tion on the north side of the Grand. Gunnison River.—The gypsiferous series does not show anywhere on the course of the Gunnison or its tributaries in our district. * Report of United States Survey for 1873, page 2066. CATE Hic Vis STRATIGRAPHY—MESOZOIC FORMATIONS. o . € The Mesozoic formations in our district are divided about as follows: Thickness in feet. Tenge Deo Ue ie Seem tI c 8S WE tec) EO ER Eee ROEM Re 1,000 to 1,500 PASI CHS. 422 eee ih Se SS is oe Si saa ye eels Se aeaied ses Se Sea DL Nu cieg walneal 400 to 900 PRED RACCOUB tere wield Sais 5s octal Sais mia ie niale taser Cie cininia wp helaaie eile a diseiensmne 4,000 to 4,700 5,490 to 7,100 In the Triassic beds the arenaceous element seems to predominate, a few bands of limestone appearing in the Jurassic. Sandstones and marls prevail in the Dakota group. In the rest of the Cretaceous, shales form the largest portion of the strata, alternating with sandstones and thin bands of bluish limestone. The red sandstones of the Trias (?), in the eastern part of the district have a more laminated structure than was noticed either in the Front range in 1873, or in the Gunnison this year. Cretaceous strata cover larger areas than any of the underlying strata, as: will be noticed as we proceed. TRIASSIC, Although the red sandstones which are referred to the Triassic form a well-defined lithological series, and are prominently exposed over the Rocky Mountains and at widely-separated localities, with very little change, less is, perhaps, definitely known in regard to their age than of any of the sedimentary formations of the West. The correctness of the assumption of Triassic age for them depends entirely upon their position. Up to the present time no fossils have been found in them.. The character of the sandstones is not favorable to the preservation of organic remains. They have been réferred to the Triassic by Marcou, Newberry, Hay- den, and others who have studied them in the West. In the Black Hills and at Red Buttes, on the North Platte, in Wy- oming Territory, they underlie well-defined Jurassic layers, as deter- mined by Dr. Hayden. In Colorado, also, they are beneath Jurassic layers, along the eastern edge of the Front range. Near Pleasant Park, in 1873, I found Carboniferous fossils* in a series of red limestones and calcareous sandstones. These beds were beneath the red sandstones. Again, as already mentioned in the preceding chapter, I tound fossils of Permian age below the Red Beds, so that they must be referred éither to the Permian or to the Jurassic, leaving an unoccupied gap between. Therefore, until fossils are found by which their age can be definitely Settled, I think it best to refer them to the Triassic. The line between the Triassic and the Jurassic is indefinite, and I * Report United States Geological Survey, 1873, page 198. 121 122 GEOLOGICAL SURVEY OF THE TERRITORIES. have taken the upper or more massive part of the sandstones as the limit of the Triassic formation, referring all above to the Jurassic. This arbitrary division was also used by Mr. Marvine last year. As already mentioned, these red sandstones vary but little over broad areas. On the Colorado River they were observed by Newberry.* In Colorado, last year, we had them in the Front range, in South Park, and in the Elk Mountains, and they were readily recognized by their litho- logical characters. Their general massiveness was a prominent charac- teristic. Hagle River.—Near the head of Eagle River the Red Beds do not ap- pear close to the river,,although they are doubtless exposed between the Blue River range and Eagle River. Below the Piney they outerop in the hills bordering the valley on the east. The strike here is parallel, or nearly so, with the course of tle river. At the head of the second canon, however, the line of outcrop crosses the river almost at right angles to its course, first making a spoon-like curve shown in the illus- tration in Plate il. On the south side of the river it curves to the west- ward, and then gradually to the north, crossing the river again at the foot of the caion, as shown on the map, (A,) and extending up into Mr. Marvine’s district. Opposite the canon, that is, south of it, this curve forms the northern side of an anticlinal fold or break, which is shown in Fig. 1, Plate I, caused by the protrusion of the trachytic mass shown in the illustration. A section of the Red Beds, as exposed near the Eagle River, on the south side, is given below. No. 6.—Section of Triassic on Eagle River at second canon. Base. Thickness. Feet. 1. Red sandstones, somewhat laminated... -..---..-.-- ..--+2+----+ +--+ eee 70 2. Punplish ‘sandstones aces Ser eh eel Ua ae as ed eh 1 15 3. Red and brown laminated sandstones, some of the layers being seemingly CAlCATCOUS ose ao eyes ici bayein cies ata aie wire Sh a thc cane et ate eR a ae Re 193 4. ‘Coarse white: sandstones “20 Gos fF See Ce) hoa aren cs crease CO ae a 5 5. Red sandstones, more massive than the lower layers, although there is some laminations 2 c2k2 he ese Red eyes ee ena Te el se ya ees 375 6. Pink quartzitic sandstone.....--- veep cieucnaferae ore pl eee Es a aaa 300 7. Red sandstones somewhat laminated ........-.-.ese+ccee cece cee cece eee 8. Massive light-colored quartzitic sandstone...) 2 Oe A eet on Total thickwess 282 845 yo jerastig Sas Sc eyaicy eee erat 978 It will be noticed in this section that there is considerable lamination in the red sandstones. Farther westward this lamination is not so decided. Below the canon, in the hills that rise back of the low gypsiferous hills, the Red Beds form the surface, covering a large area, extending across to Frying Pan Creek. They form broad-topped ridges, in which the general dip is toward the north, the inclination being slight. As we approach the valley of the Eagle, however, it increases and we have several folds, as pointed out in the chapter on Hagle River Valley. On station No. 8, the red sandstones dip a few degrees east of north. On station No. 9, they dip North 35° West, angle 309-359. I have already spoken of the probability “of there being here a synclinal fold, of which the eastern half has been removed. This fold is indicated in the illustration Fig. 1, Plate III, by the dotted lines. Below the valley, the river flows through a canon- like valley in the axis of an * Ives’s Colorado Exploring Expedition, Geological Report. reas] | GEOLOGY—TRIASSIC STRATA—-GRAND RIVER, &C. 123 anticlinal, which isshown at @ ain Fig. 1, Plate III, the Red Beds forming the top of the bluffs on either side of the river, as shown in the figure. Grand River.—From the mouth of Eagle River the Red Beds cap the bluif for some distance, when the line of outcrop crosses to the south- ward and afterward to the east, joining the line continuing westward from h creek (map A), thus forming an isolated area of red sandstones. Between the Grand and Roaring Fork, there is another patch of Ked Beds, which is partially concealed by an overflow of lava. On the west side of Roaring Fork we have the Red Beds showing in the hog backs. Their thickness here is about 1,500 feet. They dip south 75° west, at an angie of 30°, below station 14. The upper part of the series here has layers of pink conglomerate sandstone. As we go dowu Roaring Fork the strike curves to the westward,.and the Red Beds disappear beneath a layer of volcanic rock which.covers the hills here. They re-appear on Grand River on the south side, a short distance below the mouth of Roaring Fork, forming high bluffs, that rise 500 or 600 feet above the level of theriver. The Grand then gradually cuts into thered sandstones, following the sirike, whichis about north 669 west ior nearly four miles in an air-line, forming the base of the hog- backs that here extend along the southern side of the Grand. The river then cuts across the strata, flowing out into higherand softer beds, while the Red Beds cross into Mr. Marvine’s district. From this point to the mouth of the Gunnison there are no exposures of the Triassic sandstones. Gunnison River.—The Triassic sandstones do not appear on the Gun- nison River until the lower half of the Grand Caiion is reached. They Seem to increase gradually in thickness, although the total thickness attained in the cafion is not very great. They rest immediately on the granite shelf forming the edge of the cafion below station No. 80. The area occupied by them along this- caion is indicated on map B.. At station 80, the anticlinal axis occupied by the river is very evident. It is shown in Fig. 1, Plate VII, at a. Leaving the cafion the river euts across the northern end of the anticlinal, and, turning to west, flows out into the soft shaiesof Cretaceous age. In the second or lower canon the river cuts down through the Dakota group and the Jurassic layers, and partially into the Red Beds. ~ The top of the series here is a pink sandstone, from 30 to 40 feet in thickness. The thickness of the red sandstones varies. Below station 60, where the pink sandstones were measured, the thickness exposed is about 150 feet. They are massive and present all the characteristics that the Red Beds east of the mountains do. They dip approximately to the eastward, the angle decreasing as we leave the river and increasing to the west. The river winds through the cation in Jarge curves that almost meet each other. Whenever the curve is to the westward the 1ed sandstones are cut into most deeply, and when the curve is in the Opposite direction the Red Beds, if exposed at all, are only cut into slightly. This causes the areas of Triassic age to appear in patches along the course of the river. All the streams joining the Gunnison from the west cut profoundly into the strata, and near their sources, may have outcrops of Pre-Triassic layers along their courses. I have already referred to the fact that the Gunnison River at this point fol- lows a rift or break, which was probably caused by a monoclinal fold. Two sections across this are shown in Figs. 1 and 2, in Plate IX. At first the fold as shown in Fig. 1 is not very marked. It gradually lucreases, however, and below the mouth of the Gunnison is as repre- 124 ' GEOLOGICAL SURVEY OF THE TERRITORIES. sented in Fig. 2. Farther on this fold probably becomes a fault. In the two figures just referred to, the red sandstones are represented at a. To the west and southwest of the Gunnison the red sandstones seem to prevail extensively, and probably from the top of the plateau which, as seen from the Gunnison, extends in this direction. The Indians give the lower canon of the Gunnison the name of Unaweep or Red Harth, evidently on account of the exposures of Red Beds along the edge of the river. JURASSIC. Immediately above the Red Beds, between them and the Dakota group, is a series of sandstones, marls, and limestones which I have referred to the Jurassic, although I was unable to find any fossils at any point where they were exposed in our district of 1874. They correspond lithologically and stratigraphiecally to the strata that in 1873 I referred, to that horizon. The reasons for so doing were stated in the report for 1873, and I will not take up the space here with the repetition of them. They are generally in thin beds, the shaly element predominating. Their softness has rendered them readily amenable to eroding influences, so that they are generally covered with débris, and it is difficult to. make complete sections of the formation. The Jurassic formation is widely spread in the Rocky Mountains, its distribution being identical with that of the Dakota group and the un- derlying Red Beds. Hayden, Newbery, Comstock, and others have recognized it in various portions of the West. Marcou* also claims to have discovered it in New Mexico and otber parts of the West, but, as I shall subsequently point out, the layers referred by him to this horizon are probably of Cretaceous age, while those that are Jurassic he refers to the upper part of the Triassic. Dr. Haydent, speaking of the formation, says: ‘At both of these localities (near ‘the Wind River Valley and Big Horn Mountains), at the Black Hills and at the Red Butte on the North Platte, as well as at the other localities already mentioned in Utah (near Uintah and Weber ftivers), the rocks containing these Jurassic fossils consist of a series of grayish, ash-colored and red argillo-caleareous, more or less gritty strata, with beds of soft dark- brown and reddish sandstones. These beds preserve a remarkable uniformity of character taken as a group, wherever they have been seen, and need never be confounded with the Cretaceous or Tertiary rocks so widely distributed over the Northwest- ern Territories, even where no fossils are to be found.” In Colorado, Dr. Hayden, Mr. Marvine, Dr. Endlich, and myself found the Jurassic layers presenting the same general characters that they do north of the Union Pacific Railroad. Along the eastern edge of the mountains in Colorado, the greatest thickness measured was 870 feet. Eagle River.—On the south side of the river no strata of Jurassic age appear until we reach the head of the second canon, when it crosses from Mr. Marvine’s district conformable with the overlying Cretaceous, and underlying Triassic. The following is a section made on the south side of the river at the point where the section previously given of the Triassic sandstones was made. *Geology of North America, by Jules Marcou. t Geological Report of Exploration of the Yellowstone and Missouri Rivers. F. Y. Hayden, under Capt. W. F. Raynolds, 1859-60. i) PEate.] GEOLOGY—SECTIONS OF JURASSIC—EAGLE RIVER, «Cc. 125 No. 7.—Section of Jurassic, head of second cation, Eagle River, south side. Top. Thickness in feet. 1. Space probably filled with sandstones and marls, about........----.---.+----- 500 Oelaminated sandstones and blue limestone.... ..--....-2-.. o: ssceern sce ee , 190 Semohinvellowish brown sandstone... cs... sos. Senos se ceee bec cease sarin PRE MeRCMLERMES FONG Sosa f tae se sie Sale mee me eee SEs cana UA Ree eek aro cetainie 50 5. Gray shaly sandstones with interlaminated marls and thin bands of blue lime- 5 BRENT Coa SIS oie oo = fa ayno ymin de SE eres ie ai create wid Selene teins ly Mie Se PANGAN ag a Base. es FRU) LG) Ya he ae eet ah 8 5 eh a eS la St yl 940 A portion of these bids may be Cretaceous. Nowhere along the course of the Eagle, nor at any point in the dis- trict, does the Jurassic formation occupy any extensive area. It occurs only as a narrow belt outcropping beneath the Dakota group. It is, therefore, shown principally along the courses of the streams. The line of outcrop on which the section given above was made con- tinues conformable with the Cretaceous and Triassic strata, following the eurve indicated on the map, and crosses to the north side of the Eagle at the lower end of the cation. Around the almost circular area of Cretaceous rocks south of the Eagle, represented on the map, there is, in all probability, a narrow belt of Jurassic, although I cannot be positive, as I have not followed it around, and judge so only from my observations from stations 6 and 8. With this exception, I believe there are no Jurassic strata exposed be- tween the Eagle and Frying-Pan Creek. In the low, rounded hills which occupy the greater portion of this space, all the beds above the Triassic sandstones have been removed. Grand River—From the mouth of the Eagle to the mouth of Roaring Fork there are no exposures of Jurassic age close to the Grand. The Red Beds here form the top of the stratified rocks and are covered with a volcanic layer. There may be an occasional outcrop between the head of a creek of Grand River and Roaring Fork. If so, they must be very limited in extent. At the head of Mesa Creek, a branch of Roar- ing Fork, there is probably a narrow belt dipping to the south or south- east. ~ In the hog-backs, on the west side of Roaring Fork, the Jurassic strata are seen following the line of the overlying and underlying strata, disappearing beneath the volcanic rock capping the hills, and re-appear- ing on the Grand below the mouth of Roaring Fork, finally crossing the Grand, aid extending to the northwest, forming a portion of the hog-back range, that dies away in the plateau. Between this point and the mouth of the Gunnison there are no other exposures of Jurassic age along the course of the Grand. - No. 8.—Section of Jurassic, west side of Roaring Fork, below station No. 14. Base. Thickness in feet. SPE MACE OL ANN ANESLOUG IS ci-< yl se hie estos misinls cio cao ate elee seen See ete Blo 20 to 30 &. Space probably filled with sandstones and shales ......--.-. es Aenea 20 3. Fine-textured light-yellowish sandstones.---.- 2.2.2. 2202-6 ---eee eo eee ee 15 4. Space probably filled with sandstones, marls, and shales, and perhaps some RPC SLOMES Semis ere Sec eles eect ceweele acs wu tep hs hued 2 hee of Eas aa 165 . 5. Light-colored fine-grained siliceous sandstone.-....-..------ .-----+ ------ 30 6. Soft shaly sandstone, probably slightly argillaceous .-.--...---.--------- 12 MEIC ITM CSLONG Josie wsice cance so celsoeeee she Pt ofNySaSail aoe DR Tr ee 8 8. Gray sandstones, becoming greenish near the upper part......---...-.--- 125 9. Dark-brownish gray sandstone, becoming lighter as we ascend.-....---.. 15 10 Brownish sandstone with interlaminated black shales..............--.-- 20 Top. Dasa CVs ATi a Se eae Sian SNES Wy MES AY RP tata PRY dua Wor ot deen le DI 440 126 GEOLOGICAL SURVEY OF THE TERRITORIES. Just above the bed marked No. 10 in the section is a massive sand- stone, from 60 to 70 feet thick, which forms the summit of a prominent hog-back, beyond which the beds are concealed. I have taken this bed as the lower portion of the Dakota group. It is possible that on further investigation the layers marked 8, 9, and 10 may have to be ineluded in the Dakota group. This would give a total thickness for the Juras- sic at this point 280 feet instead of 440 feet. Below the first layer in the section is a coarse pink sandstone, which at some points is a conglomerate. It rests immediately on the red sandstones, and I have taken it as the top of the Triassic. Of course, without the evidence of fossils, the lines separating the Jurassic from the Cretaceous and the Triassic must be necessarily, somewhat indefi- nite. The lines I have taken are therefore arbitrary and liable to be changed when more complete data are obtained. In the section given above, and in that made on Hagle River, it will be noticed that the arenaceous element seems to predominate. The beds were so much concealed that it was impossible to make a more detailed section. The extension of the hog-backs up Rock Creek into the E!tk Mountains will be treated of in the reports of Dr. Hayden and Mr. W. H. Holmes. Gunnison River.—The Jurassic appears on the Gunnison first in the Grand Caiion, resting immediately on the schists, and gradually becom- ing thicker as we go down the river, until the Red Beds appear between it and the schists. The Jurassic is also exposed on Smith’s Fork, extending some distance from the mouth up the stream. The area occupied by the formation, in connection with the Red Beds, is Shown on map B. , I was unable to make any section in the course of the cafion, but, as seen from station No. 80, it appears to consist of variegated yellow, white, pink, and gray beds, probably sandstones, shales, and marls. On the eastern side of the canton these beds have a much greater extension than on the west. The entire thickness is probably about the same as in the lower cafion, as shown in the section to be given farther on. On Smith’s Fork, the variegated appearance of. the Jurassic strata is also seen. In the sections made on Hagle River and Roaring Fork, this is wanting. I shall refer to this fact again. In the lower cailon the Gunnison very soon cuts through the Dakota group, which, at the head of the cafon, forms the bluffs on either side, and reaches the soft Jurassic layers beneath. At first they are exposed in isolated patches similar to the outcrops of the Red Beds lower down, varying according to the curves of the river. When the Red Beds are reached, however, the Jurassic is shown on both sides of the stream. No. 9.—Section of Jurassic in the lower canon of Gunnison River near - Station 60. Base. Thickness. Ft. In. 1. Soft greenish and purplish argillaceous sandstones about.......----.---- 20 0 2. Space filled with gray laminated limestones and interlaminated soft gyp- siferous shales isscu es CUS Bee ua SNL OSE) aa eee eon en Pa 80to90 0 3. Compact white siliceous sandstone ........-- : A MAR Gar 8.9. 4. Soft argillaceous and arenaceous shales, with “hands of hard sandstone from 6 inches to a foot in thickness. The shales are covered with an efflorescence of aikali, in which thereis salt, as revealed in tasting it... 30 (0 5. Compact white siliceous sandstone, like that markedeNow aioe eee 6 10 6. Dull bluish-gray limestone, in layers of about a foot thickness, having shaly arenaceous and argillaceous beds between. Near the top are soft greenish and os shales. All the beds are more or less gypsiferous.. 35 0 PEALE.] GEOLOGY—JURASSIC STRATA IN ARIZONA. 127 Thickness. Ft. In. Mapwollave stlicCOUSSANGSLONG. - 220 Sac se cee jess es clla ce ciew seine ciccimce ss 20 8. Soft green sandstones and argillaceous shales...-.....-....----.------- 9. Space covered where the section was made, but as seen from a distance lower down the river filled with beds similar to those of No. 8........ 40to50 0 Top. LGHUMDNEL SIGH ONO ES SBo6 bocGSS obSbEU addo aden Osos basse GoceoN Gace 242 7 Above layer No. 9 is a massive siliceous sandstone, which I have taken as the base of the Dakota group, for reasons that will be given when I describe the Dakota group at this locality. Below the section are pink sandstones, resting on the red sandstones, referred to the Triassic. The colors of these layers gives a unique and’striking appearance to the cafion-walls. Farther south and west this variegated appearance seems to be more marked. In the Painted Desert in Arizona, Newberry* gives the following sec- tion of the beds: Variegated marls. Thickness. Ft. In. wo LOTR REG Te URE BREE RES E Ge scde céccnueeScen beEae aSba oN She sbas TONS) 2. Green and purple magnesian limestone, containing worm-like concretions OlgcalcareousiSpalle s-e erases ere ea cee Sade nsdobogbaa basseHseS 5 0 3, IAN Nin Ole al Cee ee aoe ceddacshooce non oboceSneo DoE eSS ose eEooeae 22 0 AEDEOW DY SUGIIT SAaNQStONG -i=)\- 27. jer te reso setae ees cele ssc esl a eee 0 8 yw eLorple marlewaith silicified wood sca sc. cena else eines Societe ee 16 0 6. Purplish green cherty magnesian limestone, in several layers, alternat- mppwithi bands of marley. on ae eyes geese ieee Sie Dy a 8 0 “Zpeurple and cream-colored marls! (2 sis setos scene atcin come Les NS 30 0 8. Greenish magnesian limestone in thin layers, with bands of marl ...... 12 0 Sepvellowared.and purple mars) =. <<: sosseqre cscs eicies ee cene eee en vA0 0 Min Green limestone, Similar tovNO:.8. 4-2) sce sree tte slays ole eiejucre ere iano 3 0 11. Red, purple, pink, green, lilac, brown, and blue marls with silicified VSO Site rey fete rm ser ees saat rele ee rmienaie a sta Mem ehn ste at eratigaiwecg seus NOOO 0 Marcout refers these beds to the Trias, regarding them the equivalent of the Marnes Irisées of France and of the Keuper of Germany. He says, “‘The third division or upper group of the Trias is subdivided again into two parts. The lower is formed of thick beds of whitish- gray sandstone, often rose-colored and even red; and the upper con- sists of beds of sandy calcareous clay. of very brilliant colors, violet, red, yellow, and white—in a word of variegated marls. This upper por- tion presents a striking resemblance, as to the rocks, with the Marnes Trisées of France, or the variegated marls of Europe.” Above the section (No. 9) I made on the Gunnison is a bed of massive sandstone succeeded by shaly and marly beds, in the upper portion of which is a lignitic layer. Above the variegated marls of the section given above, Newberry ft found a bed of lignite which he considered to be of Jurassic age. Whether this is identical with the lignite in sections Nos. 12, 13, and 14, I cannot positively determine, but I think it improbable, as the beds below do not seem to be identical. If they are identical, I place the lower limit of the Dakota group lower than he did. The reasons for so doing will be stated hereafter. Newberry, in his sections of what he considers the base of the Lower Cretaceous, also finds a lignitic bed, which is probably the one I have included. Newberry§, in speaking of the lignite, says: “‘The sandstone shales and limestones lying above also include many beds of lignite closely *Ives’s Colorado Exploring Expedition, Geological Report, page 79. +t Geology of North America, page 13. ¢ Ives’s Colorado Exploring Expedition, Geological Report, page 81. § Ives’s Colorado Exploring Expedition, Geological Report, page 83. 128 GEOLOGICAL SURVEY OF THE TERRITORIES. resembling this, and on lithological grounds would be appropriately grouped with it. In fact they have been considered Jurassie, and the only Jurassic rocks in this region, by the geologist who claims to have discovered the representatives of this formation in New Mexico. Unfor- tunately, however, for that classification, immediately over the thin stratum of yellow sandstone which overlies the coal are beds of clay- shale with bands of limestoné in which are unmistakable Cretaceous fossils. Itis, therefore, evident that the Jurassic formation cannot be extended in this direction, and there is no alternative left but to con- sider the coal-seam, if Jurassic, the sole representative of the Jurassic series, or to combine with it some portion of the underlying variegated marls, which, for this purpose, must be abstracted from the Trias of Mr. Marcou.” CRETACEOUS. It is, perhaps, impossible at present to subdivide the Cretaceous formation, as seen west of the continental divide, in the same manner as has been done east of the mountains. For the sake of convenience in description, it may be best to consider it as divided into three groups, Lower, Middle, and Upper Cretaceous, as follows: Thickness in feet. Lower Cretaceous— Dakota group (No. 1)..--.... 22222. cence -- een nnen 500-700 Fort Benton group (No. 2), Middle cretaccons—} Nioorara- division’ ;(No.33) yi o-cceeleene contacts 2, 000 Fort Pierre group (No. 4), ( Fox Hill beds (No. 5). ) } A series of shaly sandstones, which in the lower | Upper Cretaccous— part are lignitic. On Anthracite Creek this eects Shy \ lignite is changed into anthracite coal..--.. J POtal eek se MAPS s esa Besse SM, See ea Ss 4, 000-4, 700 This table represents the estimated thicknesses as developed in our district. LOWER CRETACEOUS. Dakota group—Formation No. 1. ' Immediately above the group of shales last described, under the head of Jurassic and conformable to it, is a series of beds in which rather mas- sive siliceous sandstones predominate. It is persistent throughout the Rocky Mountains, preserving its lithological characters very constantly over widely-separated areas. The group forms a convenient horizon for reference, being more strongly marked, perhaps, than any other in the sedimentary series. Its age is well established, and I will therefore not take the space here to repeat the evidence. The discussion in full will be found in Professor Lesquereux’s ‘‘ Cretaceous Flora of the West.” * The evidence as to its identity in Colorado is as follows: During the explorations of 1873, near the exit of the South Platte River from the mountains, I found fragments of a Proteoides,t of which Professor Lesquereux, writing me, said: ‘It is very near Proteoides acuta (Heer.), if not a small form of the same.” As yet no leaf of this genus has been found higher than the * Report of United States Geological Survey, vol. vi; Cretaceous Flora, by Leo Lesquerenx. t See Report of United States Geological Survey for 1873, page 196. PEALE.] GEOLOGY—DAKOTA GROUP—EAGLE RIVER. 129 Dakota group. In the same series I also found, near Glen Eyrie, a few miles trom Colorado City, specimens of a lingula too indistinet for spe- cific identification. In the Elk Mountains numerous impressions of dicotyledonous leaves were noticed, most of them fragmentary and in- distinct. On the Gunnison River during the past season (1874) I found a frag- ment of a sassafras-leaf like S. mirabile, near station 60, and in the bluffs near the mouth of the Gunnison I obtained a Cretaceous Scaphite. In various parts of the Elk Mountains Mr. Holmes found impressions of a Saliz. Professor Newberry* recognized the group in New Mexico. I shall hereafter refer to. the identity of his sections with those made by me on the Gunnison. Speaking of the rocks as exposed in New Mexico, he says: ‘ The paleontological evidence of the age of these rocks is quite conclusive and of unusual value, as it fixes the place in the geological scale, of a well-marked formation in New Mexico, and one which has been the sub- ject of considerable discussion. In the second member of the Cretace- ous portion of the section, counting from the base upward, are con- tained fossils which are characteristic of the Cretaceous formation in Texas and Nebraska. These are Jnoceramus crispti and Gryphea pitcheri, well known Cretaceous fossils, common in Texas and the Indian Terri- tory, and, in greater numbers, specimens of an ammonite (A. pericarina- tus), highly characteristic of Nos. 1 and 2 of Meek and Hayden’s section of the Cretaceous rocks on the Upper Missouri. There is no doubt of the parallelism of the group of sandstones with those of the base of Meek and Hayden’s Cretaceous section.” The lithological characters will be shown in the various sections given, as I consider the formation according to its geographical distri- bution in our district. Hagle River.—Until we reach the head of the second canon there are no outcrops of Cretaceous age on the south side of Hagle River. Here, however, the sandstones of the Dakota group cross from the north and . form a semicircular ridge, crossing to the north side again at the lower end of the canon. In Plate II the group on the north side at the head of the cafion is shown at a a. The semicircular line of outcrop is Shown on map A. Stations 6 and 7 were located on its edge. The dip ot the strata on station 6 was North 5° East, and on station 7 North 85° East, the angle of inclination about 20°. In this basin, included between the ridgeand the river, the overlying Strata have almost entirely been removed, the upper part of the group forming the greater part of the floor of the depression or semiquaqua- versal. A section through the center of this basin is shown in Fig. 1, Plate I, from the point a to the Eagle River. I was unable to get a section here, so that I cannot say how thick it is. On station 6 the rock is a coarse white siliceous sandstone. Where it is in contact with the volcanic rock, as seén in the section and on the map, it is meta- morphosed. Below station No. 7 there is the following section, from below up: Gray sandstone, greenish coating on the surfaces of the lamine. Hard greenish mottled limestone. Greenish gray sandstone. , Blue limestone. Sandstones forming the station. Sr She * Ives’s Colorado Exploring Expedition, Geological Report, page 85. 9H 130- GEOLOGICAL SURVEY OF THE TERRITORIES. The lower portion of this section is probably Jurassic. The area of Cretaceous represented on the map lying between the semicircular ridge and g creek is probably almost entirely of the sand- stones of the Dakota group. There may be some of the layers of No. 2 and No. 3 in places, as shown in Fig. 1, Plate I. There are no other outcrops of No. 1 on Eagle River or its tributaries within the limits of our district. Grand kiver.—Between the Grand and Roaring Fork, at the head of Mesa Creek, there are, judging from the view we had from station No. 11, outerops of ‘the Dakota group dipping to the southwest. It also out. crops beneath the mesa between this creek and Frying-Pan Creek, near the base, on the south side. Between the Grand and Roaring Fork there may be a few patches of Cretaceous, but, if so, I think they are of higher beds than the Dakota group. On the west side of Roaring Fork it forms the summit of the prominent hog-back ridge. On station 14 it is a massive light grayish siliceous sandstone, the outcrop of which measures 63 feet If the beds marked 8, 9, and 10, in the section of the Jurassic (section No. 8) made here, are included, the following would be the section of the Dakota group at this point. No. 10.—WSection on Station No. 14. Top. Thickness in feet. 1. Massive grayish white siliceous sandstone.-.-.--. --2. 22-2 en ecen ween es eee eens 63 2. Brown sandstone, with fine black shales ...-..-....2--..---- -2-- -----q---- - 22° 20 3. Dark brownish-gray sandstone, becoming light-colored near the top.- Re aia o/s ae 15 4s Light greenish Sandstone) \.-s-aoaceee oe ee see eeel eee eee sae eee eter 125 Base = Total about cece pert apeltcin acalek oA) oe Se ene Se ee are ta 263 The character of these beds, I think, warrants their being considered Cretaceous rather than Jurassic. The black shales in No. 2 probably occupy the same horizon that in the other places is filled with the lignitie beds. If they are not considered Cretaceous we have only a thickness ot 63 feet for the Dakota group. Above the laver marked No. 1 the beds have been eroded and covered with the débris, leaving a valley between the hog-back and the hills to the west. On the Grand, below the mouth of Roaring Fork, the Dakota group comes out from beneath the volcanic rock of station 16. At station 14 the strike of the hog- backs is north 15° west, and the angle of dip 30°. Station 17 was on the sandstones of the Dakota group. The inclination here is 35°. This seems to increase to 50° or 60° to the westward. The strike is north 75° to 80° west. The hog-backs extend about seven miles beyond station 17, when they cross the river into Mr. Marvine’s district, and the Grand, from that point to the mouth of the Gunnison, flows through beds of higher horizons, not reaching the No. 1 until the river is joined by the Gunnison. Here it outcrops i in the bluffs. I will reserve the description to the section devoted to the Gunnison. Gunnison River.—At several points bordering the meadow-like expan- sions of the valley of the Gunnison below the mouth of Cochetopa Creek, there are indistinct outcrops of sandstones that probably represent a portion of the Dakota group. As we proceed down the river these out- crops become more distinct, and below station 73, besides the No. 1, shales of No. 2 arerepresented, showiat cin Fig. 1, PlateXIV. The Cretaceous rocks seem to have been subjected to considerable erosion, preceding the lava flow that has covered them. This is shown by the change in the Strata shown in the figures in Plate XIV, which are sections on the north PEALE.] GEOLOGY—DAKOTA GROUP—GUNNISON RIVER. 131 side of the Gunnison at various points between the mouth of Cochetopa Creek and the mouth of Lake Fork. The drainage had probably then the same general direction it has at present. In Fig. 2, Plate VI, beneath station 77, at the point d, we have on top of the Dakota group a few shales. Farther north, at station 79, there is greater thickness, reaching in all probability as high as No. 4. The wearing down was probably trom north toward the south, which is the general direction of the streams at present. The following section was made from the point a@ to 6, in Fig. 1, Plate IGE. : No. 11.—Section of No. 1 Cretaceous, beneath station 73 north side of Gun- nison River. ~ Base. + Thickness in feet. PeDark MiCaCeOUS-ONEISS—s~ 21sec aelo At oeine oe eas eis ee RR eee a-2. Siliceous sandstone, general color yellowish, becoming pink and white in places. The lower portion issomewhat concealed in beds that are massive. 43 3. Siliceous sandstones like those of No. 2, general color pink. These sandstones are not so massive as those of No. 2. They are somewhat laminated... -.--. 58 4. Yellow sandstones in bands of two and three feet thickness. ...-........---- 32 5. Sandstones and interlaminated shales. The general color of the sandstones is yellowish; some of the layers have greenish pebbles. Tbe shales near the top AEG MLEODISH yo. sc 5s aciic hse eevee ae Seaiele ss eeisusne sre SEE peer abe noa soee 79 6. Lamiuated brownish-gray sandstones in bands from a foot to eighteen inches in thickness. There are greenish-gray interlaminated shales. Some of the sandstones are probably urgillaceous and weather into rounded bowlder-like DIESE Skate de Boma OBUIG Bild SO ABBO BAM HMM Ral easel {eles de i ace ial alles 6 7. Space filled with bands of sandstone and soft argiilaceous shales and limestones. In the lower part there is a nodular limestone with pebbles of red jasper. The upper parts of the sandstones are faintly tinged with purple..---.. Ouse sikey 8. Greenish and yellowish indurated argillaceous sandstones and shales, resem- LIN [CHE DEAS OTINGs (hase eae ee teins ere era NEEL) SADE Ad AN ee 9. Soft yellow and white laminated sandstones..-... 22-2222. 2222 elle. eee 16 nO Soi pinkish laminatedsandstomes eo. on easyer Se OR ON ea Ut 14 11. White argillaceous sandstones and shales; some of the beds are indurated and break with a conchoidal fracture. The sandstones weather with rounded corners, forming bowlder-like masses as in the case of No. 6...--.-----.-- 54 #2; Masstve yellow siliceous sandstones, about .2 2.522202 02.2 2222 oko) 22h. 100 Top. Total, about .-.--.-:.-- LIS APS a Ae yey ern RE ES ee MY em a Ln epee 536 These sandstones and shales are exposed on both sides of the river beneath the breccia, and also for some distance up the lateral branches. North of the Grand Cafion the gently-sloping surface between the Gunnison and Smith’s Fork is underlaid by the Dakota group, which forms a bluff-like edge above the granitic shelf bordering the cation. The slope is about four degrees in a direction a little east of north. Smith’s Fork cuts through the No. 1 almost parallel to its strike. The beds here have the same general character that was noticed in the sec- tion given above. In some places on Smith’s Fork I noticed black coaly- looking shales, and in some of the laminated sandstones were ripple and mud marks. Near the head of the south branch of Smith’s Fork the gentle slope of the Dakota group is broken and the stream flows through a small caiion caused by the breaking. Tuis cafion is marked a aon map B. It is only about two miles long. On the west side the dip of the Strata is 5°, while on the east it is 15*o0r 20°. In the latter place it forms a small, almost triangular area, of which the base is toward the west. The fracture determining this cafion was probably the result of a fold which may have been caused by igneous action, contemporane- ous with the elevation of the trachytic hill opposite the mouth of the 132 GEOLOGICAL SURVEY OF THE TERRITORIES. creek. Between the cafion and station No. 38 there are two areas of trachytic rock,which may also have had something to do withit. On the south side of the Grand Canon the Dakota group does not appear at the upper end, shales of higher positions abutting against, the schists, as shown in Fig. 2, Plate VII. Bik: In the angle included in the great bend of the Gunnison, opposite the mouth of Smith’s Fork, the sandstones of No. 1 form the surface. See- tions across this area are shown on Plate VIII, the letters giving the lines on which they are made, as represented on map B. On the west side of this area the beds dip steeply, and in the valléy of the Uncom- pahgre the Dakota group is covered with the overlying beds of later origin. A short distance above the mouth of Roubideau’s Creek it appears again, forming bluffs that gradually rise as we go down until the river is again in canon (Unaweep Cajon.) The following is a section of the bluff on the Gunnison opposite the mouth of Roubideau’s Creek : No. 12.—Section of Uretaceous No. 1.—Bluff on Gunnison River. Thickness Top. : Hts eine 1. Space reaching from the top of the bluff,which is covered with bowlders of sandstone and voleanic rock, underlaid, in all probability, with sand- stonesand: shales pai.) 2 hee ple et ee Ur aan ye ee eae 50to60 0 2. Massive yellow sandstones 525502 sons. eee eae eee eee see ee 10 0 3. Space in which the upper part is occupied with gray and rust-colored sandstone shales, with carbonaceous material. The lower portion of the space is probably filled with layers similar to those above. The slope is covered with the debris of sandstones in which there are fragmental im- pressions of stems, but no leaves, although careful search was made.. 31 (0 4. Gray laminated ‘sandstones ai siie2 fees aE en Ue ase ea cee seo ainoieicet lars 33° «(0 5. Black carbonaceous or lignitic shales with effloresence of alkali-..-.... 1 6 6. Yellow and gray shaly sandstones..-....--.-..--..---------02 0------- 4 0 @7,bune black jcanbonaceousishalese. oss. cece sce: sameness cis se ee eee 6 0 Sa Massive joraysSand GbOne nee aa) b ates tats elses et eee eel oral tole ae te eererate 10 0 9. Shaly sandstones alternating with shales like those of No. 5......--.-.-- 22 0 10. Coarse, white, granular siliceous sandstone... .....----. .----0 2-2-0 -- 2to 4 0 11. Sandstone shales reaching to the base of the bluff.......-....---.---.- 16 to18 0 Base. =>: Total; abouts tes fools 8 sae Gees ao Se a ee ee aeons 199 6 This represents only a portion of the No. 1. The river, however, soon cuts through to its base. The area occupied along the eastern side of the Gunnison by the Dakota group is limited to a narrow belt, the higher beds outcropping in low bluffs from three to five miles from the river. A section at station 60 is given below: No. 13.—Section of No. 1 Cretaceous.—Bluff on east side of Gunnison fiver, Station 60. Thickness. Top. Ft. In. 1. Massive yellow siliceous sandstones, with indistinct impressions of leaves and stems. The sandstones are so coarse that nothing recognizable could@be seen sie. cots eee ee eect Cdaaoes 54 0 2. Blue argillaceous shales, gypsiferous..---...-. Baan SOR eS oHe Saat 6 3. Fine black lignitic shales with interlaminated sandstones and clays..... 18 6 4. Blackish-gray laminated sandstones and shales.....-...--------------- 31 8 5. Soft gray sandstones with greenish shales in the upper part......-..--.. 25 4 6. Soft argillaceous sandstone shales in bands of red and green colors alter- OCT Nee nen es See Bae AMORA AREA ASAE S80) 6 oo Soh een 3a OS OUES 25 4 7. Yellow siliceous sandstones in rather massive layers, very much like those in-No...1, given ADOVE.. <6 )s-2 can hae a eee eer ae ee 63 0 8. Blue and yellow mottled argillaceous sandstone shales..--.....---.---- 6 4 9. Fine red and green shales, argillaceous and probably calcareous ...-...- By 0) PEALE.) GEOLOGY—SECTIONS OF DAKOTA GROUP. ie Base. Thickness. A n, 10. Compact, fine-grained, brownish-red sandstones, with interlaminated shaly beds Mortlien GLOSS TTACHUNO ee tet es ea ee eee ee 47 6 11. White, dendtitic, argillaceous sandstones, indurated near the top, and ; having a sharp, Canchoidal/tractune 020). 6) 2 NO MSE ee 8 0 12, Greenish and purplish argillaceous shales...-...........-...-----.---- 19 0 13. Yellow siliceous sandstone, Yather massive in the lower part, laminated DIDOUE HSS Sy See rete Ss A IE 8 2m ee ee eR ACH tS 6 4 14. Reddish and whitish-green mottled sandstones, grading up into soft SBAlGRe seeks scic S Sane t a aAsite aetoeia aeeees SIGHS NG Bea Se See We artrec Ob SiO 15. Reddish, purplish, and greenish sandy shales, mottled..............--- 24 0 16. Greenish-white, argillaceous sandstone, weathering into rounded ) BrAssespike DOWILERS cease sate San reatelniac lot neste npaa eis ecient ate | wperick-red shales mottled with greem 2 s- 5.05.60. -555 2555 eee eee oe . 68 6 een SanGscone of L00bs a> = sec otsace cisco he ned Cec, sas cela cine he 19. Greenish shaly sandstones, with hard bands of sandstone at intervals, and fine red shales in lamin: 2, G inches in thickness ---22..2222.-2-- J 20. Soft greenish conglomeritic sandstone. The upper bed is a green sand- stone, below which is an irregular mottled limestone, argillaceous, brown, reddish, and greenish, with jasper in centerof nodules. In the center there are also quartz and calcite. Some of the beds in this space BLOCONCE ALE Mey) Se SL ee ie raerety eet ate atten si aic Hae noche (ae ever cretefnns 43 0 21. Massive yellow siliceous sandstone, coarse in places, with siliceous peb- [HECSEESE CER OSS OIC Hele OR ie Ces Gest settee CN Da ic ett la ea 10 0 22. Soft white sandstones, conglomeritic at the base, containing black, red, anduyellowapebbles': vieryitine peas te eiop sae ooo c ii esieaeioe eee ace 1 6 23. Soft shaly beds, partially concealed by argillaceous débris. These beds are composed of greenish-gray, argillaceous sandstones, brownish nod- ular limestone, and greenish clays. Nearly all the beds are gy psifer- ous. The sandstones break into rounded pieces. ‘The débris is coated Withvaisalty, alkaline eflorescencemen: so-siscices iciamcni seen cae see 30 0 24. Space in which the slope is partially ‘covered with débris of hard red sandstone and dark gray sandstone, and indurated argillaceous beds of a purplish sandstone; near the top was an outcrop of dark brown- ish-gray sandstone. In the débris below I founda specimen Sassafras, like S, mirabile, in a rock similar, but was unable to find any fossils in WACO eR Eee Be Se HAS GES AHA Sa eM eree Gah Meas ae ancey Reet en Niece IR MNS eat 0 25. Yellowieh siliceous sandstones, gener ally i in massive beds, but toward the , base somewhat laminated's 2-525 2-\ 150 tu 160 nite is of poor quality, decomposing rapidly on exposure to the at- TIGL CHELSEA 2) Sem eh fr Nee tN oa Re EET ic Oe 5. Yellow siligeons sandstones with massive structure below and becom- ' ing shaly above. The lower portion is gypsiferous. ..-............J 134 GEOLOGICAL SURVEY OF TIIE TERRITORIES. The lignitic beds No. 2 in this section correspond with No. 2 in the sec- tions made near Roubideau’s Creek and station No. 60 (sections Nos. 12 and 13). In the section made near station 73 (No. 11) this layer seems to be absent, as it also is in the section made at station 14 on Roaring Fork. It is probably this bed that Dr. Schiel refers to in the Geological Re- port of Captain Gunnison’s exploration when he says: ‘In the Valley of the Blue River, a coal-measure, supported by sandstone, crops out at several places, but the coal does not seem to be of good quality.” Professor Newberry gives the following detailed section made in Arizona: Feet. 1. Coarse yellowish sandstone, with concretions of oxide of iron, and obscure im- pressions of dicotyledonous leaves ...--...--.---------s00-2eeee eee ee 16 2. Impure coal, alternating with bands of bituminous shale and fire-clay, con- taining tossil- -plants—Clathropteri is, Cyclopieris, Sphenopteris, Pecopteris, &c.—-alllimew Species ze sie Sa ELE SUS, ARNE Ni Dan A Se a ae PCR StL 12 3. (Mine-clayjand shal enence. saseine ee ace oes eas Sa ee TEDL TENE a8 A aoa ie es o 4, Coarse, compact, white concretionary sandstone.-..-...---..----.---------- 6 (Green Maran cso oS Sek aN 20 a) I 25 6, Brichtired! amarl ees. pee eae ene GUNN Ae OT Sie ae RUN ge po a ge 22 Ue White, soft, saccharoidal Calenreons sandstone to base ..5_ 0.04 2 ses eetees cine eee Layers 3 to 7, inclusive, are probable Jurassic. At another point, not far distant from where the cgi above was made, Professor Newberry made another section, of which the following is a portion: 11. Coarse light-yellow or whitish massive sandstone .........--..-----..----- 120 12. Green shales, with bands of ferruginous sandy limestone and beds of lignite. In this group at Oraylee and Camp 96 are Pinna? lingula (n. sp.) and Gryphea pitcheri ; and over the lignite beds are. impressions of leaves of Plotanus, Alnus quercus, &c., and fossil ferns of the genus Sphenopteris .--. 90 13. Green, blue, and gray argillaceous shales, with bands of brown or yellow sili- ceous limestone, containing Ammonites pericarinatus, Inoceramus crispti, and Grypheapiichert, Var navia) eines = eh cde 22ers neee Sesion eeiee 160 14. Coarse yellowish sandstone, precisely like Nos. 9 and 11 (base of Cretaceous formation 2). 2 32a e bo uee seh eet SOS Se eC ns Fem eae A ee a 20 15. Lignitic, (Jurassic?) better than that above, to base. The bed of lignite, which he marks Jurassic? is the layer marked No. 2 in the first section given above, while No. 14 corresponds with No. 1. Comparing these sections with those I made on the Gunnison River, the lithological similarity is evident. I think it probable that his beds of lignite, marked No. 12 in the sec- tion given above, are identical with the layers included under No.3 in my sections on the Gunnison (Nos. 12 and 13). If so, the bed of lig- | nite which he considers as Jurassic is wanting in my sections, while his layers, marked Nos. 13 and 14, correspond to those included in Nos. 23, 24, and 25 in section No. 13, made at station 60. It is a curious coinei- dence that the thickness given by him (185 feet) is the same as that given by me. This, however, is no positive proof of identity, as these beds vary in thickness in localities very close to each other. If the beds do not belong to the same horizon, I have placed the line of division between the Cretaceous and Jurassic layers lower than Pro- fessor Newberry has done. The specimen of Sassafras that I found in bed 24 of section No. 13, is the only evidence I have upon which to ground such a separation. Speaking of the specimen Pecopteris that he found in the lignite bed (No. 2 of his first section given above), Newberry says, “Associated with Clathropteris of Jurassic affinities, and with the first appearing species of the dycotyledonous plants of the Cretaceous epoch, this PEALE.] GEOLOGY—CRETACEOUS NO. 2 AND NO. 3. 135 Pecopteris confirms the inference derived from other sourees, that the lignite bed containing it lies just at the point of junction between the Cretaceous and older rocks, and showing a mingling of forms belonging to the two formations, proving the impossibility of drawing sharply the lines of division.” In the blufis, at the mouth of the Gunnison, below the lignitic beds, I found a specimen of Scaphite, which marks the layer of Cretaceous age. It probably represents the equivalent of layer No. 13 in the second section given above by Newberry. If so, the identity of the sections with mine would seem to be pretty clearly indicated. MIDDLE CRETACEOUS. As I have already indicated, it is impossible in our district to give the exact limits of the different formations comprehended under No. 2to No. 4, inclusive. As the shaly character prevails throughout the series, I have included them all under the same head. At the base in No. 2 thev are decidedly arenaceous, the beds just above the Dakota group being laminated sandstones. Gradually they become more and more argilla- ceous, and near the top thin bands of limestone appear. Cretaceous No. 2 and No. 3. Exposures of the Fort Benton group and the Niobrara division are seen in the valleys of the Grand and Gunnison Rivers, and on the North Fork of the Gunnison. Want of time precluded the possibility of mak- ing a complete section from the base of the series to the top, although I succeeded in gettting several sections which will give the general characters of the strata. The layers of No. 2 were not generally so well exposed as those of No 3. The higher we go in No. 2, as exposed in our district, the more shaly and argillaceous do the beds become, and in No. 5 they are also calcareous. Hagle River —On the north side of Eagle River, opposite the second canon, as viewed from the semicircular ridge of stations 6 and 7, the Fort Benton group and succeeding divisions of the Cretaceous are seen outcropping in the most beautiful manner, as shown in Plate II (be- tween b and c). On the south side all have been removed except a few remnants of No. 2, and perhaps also of No. 3 in places, leaving the sand- Stones of the Dakota group as the floor of the semiquaquaversal already described. Still farther south, in the circular area of Cretaceous near the Eagle (see map A), remnants of No. 2 and No. 3 are seen, as shown in the section in Fig. 1, Plate I. Grand River.—In the range of hog-backs, extending from the Elk Mountains along Roaring Fork and Grand River, and finally crossing the latter, there are exposures of all the Cretaceous strata above the Da- kota group. There was no opportunity here to make any sections. On the south side of Grand River, in low blutts above the mouth of the Gunnison beds of No. 2 and No. 3, outercp, black shales prevailing. Gunnison River—Under the rhyolitic and breccia-covered areas, bor- dering the Gunnison above the Grand Cafion, there are in all proba- bility fragments of formations No. 2 and No. 3. They are exposed be- neath the mesas that stand between Slate or Hast River and Ohio Creek. The exposures of the beds immediately above No. 1, between the North Fork of the Gunnison and Rock Creek, will be referred to by Mr. Holmes, in his report on the geology of the Elk Mountains. Between Smith’s Fork and the North Fork of the Gunnison there is: 136 GEOLOGICAL SURVEY OF THE TERRITORIES. wide area, in which the strata almost entirely belong to No. 2 and No. 3. There are two parallel lines of bluffs, the first composed of black Shales, which are also shown along the course of the North Fork. Some of the upper beds may belong to No. 4. The following is a partial section on a line between station 38 and sta- tion 80. Section No. 15. Thickness. Base. Ft. In. iy Trachyte, about! 75 feet, thick 2c. 32/5 see tee ae sae ao ee eee ar re 2. Gray and black argillaceous, with Inoceramus.......------.-----+----+----- 58 0 3d shales and: bluishislates! i020 022 2 oe en 2s I RI an Ta 100 0 4. Slope covered with débris of shales above .....----...--------2.---------s 32 6 5. Bluish slates weathering rust-color, in laminae 4 of an inch thickness, con- taining Inoceramus and fish-scales, too indistinct for identification....... 160 0 6. Gray and grayish-blue limestone with interlaminated shales, containing Ino- ceramus and. fish-scales. 0 2225 ee Se Le. 160 0 7. Dark bluish-and black shales)..-\- 2. 50d. ja- eee ce oe ae SE Eee ee eee 243 0 Total aboutses ses voc tcc ey sedece seis see eitecie Ba See ee eee eae: 753 6 At the base of the mesa, which ends east of the Gunnison below its mouth, No. 2 and No.3 outcrop. The following section was made north of the Gunnison, opposite the mouth of Roubideau’s Creek. It will give the characters of the beds. They may all belong to the Fort Benton group, or the upper portion of the section may possibly represent a part of the Niobrara division. Section No. 16.—Gunnison River, opposite Roubideaws Creek. Thickness. : Base. ® Ft. In. 1. Shaly sandstones, with interlaminated argillaceous beds extending from )} the top of the bluff on the river to the base of the first bluff north of the | river. The beds are for the most part concealed..-.........---.----- rp 175 0 . Coarse yellow sandstone, with calcite ..:...-----. 2-22. eee oe. wee ee oe 1 Gray laminated sandstones... .--22- 6 ss.+ 2 eee eee eee ea eee . Thin lamine of grayish sandstone shales, with fine black argillaceous shales, gypsiferous and calcareous, containing Inoceramus, Ostrea lugubris (Conrad), and other'Cretaceous fossils. 222 2222 aya ee oe ee eee: 125 6 5. Yellowish sandstone shales, with quantities of Inoceramus and Ostrea espe- cially abundant near the top, where there is a layer of black shales.... 40 0 6. Black argillaceous shales, partly concealed by débris...-...--..----.----- 38 0 7. Coarse yellow, gypsiferous, and calcareous sandstones, with layer at top, * breaking into pencil-like pieces one to two inches long and an eighth of Ce) an/inchlim thickness\s 2-6.) eos isco ieee site ees eee merererareys 50 3 85. Sandstone shales... 22) S2n 55 Sobel Lae Boe ee eater 120 0 9) Hine black’ /argillaceous shales! 22-2224. 52 02 oo suse eee 10. Coarse yellow calcareous sandstone, resembling that described under No. 7- 10 11. Fine black argillaceous shales, with bands of sandstone (fossiliferous), spe- cies of Inocenamus/andOstrea.. == ose sen ese eee eee 36 0 12 Hardroray, sandstones.) -+ = 2 s25-)aesse ieee ae One eee ene eer 10 13. Very tine, soft, black argillaceous shales, with a few lamine of gray sand- stone. In the lower part of the group the shales are coal-black, but as we ascend they become gray-black. Nearly all the layers are fossilifer- ous. Among the forms are Prioncyclus wyomingensis, Scaphites warren- ana, and Inoceramus problematicus. They are especially abundant near : the top eaeens ese ee Ren Se ee NRE EEN A Sk Sa enon aoe i 66 6 14, Fine gray and yellowish shales..-.-...:.-..----. .--- .--- +--+ +--+ :+----- 34 0 15. About 17 feet of gravel, composed largely of basaltic bowlders, forming the top of the: bluttt 5-63-2252 See See Oe a eee a eee Total, about .o55..$.ce 54. cssas ae lee segs Gok eee eee eee ie och Near station 73, on the Gunnison, shales belonging to formation No. 2, outcrop beneath the breccia that underlies the rhyolitic covered Inesa. (¢, Fig. 1, Plate XIV.) ee Plate X. Gre ete Myf ere exe aias kath PEAS is A An dec AE i \ ae ol oon aa D Co } ce Raines iad =< ee ea Tay Bae SNe, os reper | \\: WN \ ae fg = ( Wy .~ Wi. Vii, See) Wy ue we a) Ae pit) o Blut? at head of “Oh be poytil Grek, if 4 4 | ay rede fags VORR iy PA PEALE.] GEOLOGY—CRETACEOUS NO. 4—UPPER CRETACEOUS. 137 They are 25 to 30 feet in thickness, and represent but a portion of the rou ; aides station 79, on the south branch of Smith’s Fork of the Gunni- son, there is a oreater thickness exposed, some of No. 3 probably show- ing, although i cannot be certain, as I had no opportunity of making a section. These strata are the direct prolongation of those exposed in the open country between the North Fork and the north branch of Smith’s Fork of the Gunnison. CRETACEOUS NO. 4. Unfortunately opportunity did not offer to study in detail the strata referred to the Fort Pierre group and the Fox Hills beds. I was unable to tell where No. 3 ended or No. 4 began; the thickness, therefore, could not be given. I estimated the thickness of the series from No. 2 to No. 4,inclusive, at from 1,500 to 2,000 feet. The only fossils obtained were specimens of Avicula linguaformis and Inoceramus barabina, from an outcrop of bluish indurated clay in the valley of the Gunnison, near Kahnah Creek, beneath station 58. This layer, I think, belongs to forma- tion No. 4. No.4 and No. 5 outerop in all the localities where Nos. 2 and 3 are seen, with the exception of station 73, where No. 2 alone is seen beneath the breccia, the other beds having been eroded previous to the deposition of the breccia. The best exposures are seen in the valley of the Gunnison, but even here the softness of the beds renders them readily eroded, so that they are concealed by the débris of the strata, and it is difficult to make a connected detail-section. The strata of No. 4 are largely light-gray and bluish argillaceous beds, with sandstones near the top that give a yellowish débris. They pass gradually into the sand- stones and shales of No. 5. In No. 5 the arenaceous character prevails. The group next to be described may belong in part to No. 5, or may, perhaps, be an extension of it. Until fossils are found in it, its position is somewhat indefinite, and I have therefore considered it separately. UPPER CRETACEOUS. I had no opportunity of estimating the entire thickness of the beds included under this group. In the Elk Mountains, where they are seen most extensively, there has been so much disturbance of the strata that it is difficult to obtain connected sections. On Coal Creek there is a bluff in the face of which are exposed 1,500 feet of light-gray and yellowish sandstones and shales. On the North Fork of the Gunnison, the exposures must be of greater thickness. The upper part of the series, however, is not shown here. The coal occurs in the lower part of the series, as shown on Coal Creek. The sections will best illustrate the character of the beds. In the broad valley east of station 48, and south of Grand River, are chocolate-colored shales, and greenish and gray sandstones that should probably be referred to the upper part of the series. The following is a partial section made on a small branch of the Grand, below station 19. No 17.—Section south of Grand River. Base. Thickness. Feet. maedsrse soit whitish sandstone...-.. .c-s-s---2-sscces cee ses Bias ei seeeetents 3 Paetcomish sandstone, coarse and soft .......---2- seecce cnee coee tens coccse cs 4 4. Space covered with a reddish-brown débris, probably underlaid by al- ternating sandstones and limestones..-....---0¢ cece eeccce snee nee PUTER WILISIN ITIHESEON Greys eo ee ne tel Mee ABUL SY : 15 138 GEOLOGICAL SURVEY OF THE TERRITORIES. Base. Thickness. Feet. 5), ID i@lnin eh ;Se INTO oS Ah0 s56eus soubos bo5560 peaGcd oSq0 056455 bade 9550 bobs 6. Space covered with a brownish débris in which are nodular masses of brown limestone; near the center of the space is a band of white sandy débris-. 45 7. Black argillaceous shale ? 5 SrVVsILS SANASTONEMe ase MONO a nat ann in eh naa 9. Space covered with débris, in which are occasional outcrops of black and reddish’ shalest [2222/5 152193 LAE SEP pe ye SSS Serer ogee enero ote 26 10. Rather massive light greenish-gray sandstone ..-.-..-.--.------.-------- 8 iihiGreenish-and) purplish shales 22 6o22 =.) veces 2) e eee eee erent 6 12. Bluff of yellowish sandstone, massive below, eee shaly above, con- taining fragments of stems and leaves...-....---. ..---..------+------- 104 Total aboubtieee i sei ees ei es tee eae oe ee a antes ee 2. LEAT In layer No. 12 I found an indistinct Aralia, which Professor Lesquereux considers Cretaceous. The section on station 26, still farther south, was given in chapter ILI. On the ridge dividing “‘ Oh be Joyful” Creek from Anthracite Creek, near station 32, | made the following section, the letters corresponding with those in the illustration in Plate X: Section No. 18.—Head of “O be joyful” Creek. Thickness. Base. Feet. In. ( 1. Massive white sandstone, reaching from the base of the cliff for sev- ) | eral hundred feetie 245 2 Seis seers tose eee ce See eee eee anes | KE. { 2. Gray shales, succeeded by massive sandstone.....----.---.----.--- + 500 0 3. Black shales.and rusty sandstone ..- ~~. --2- 22 2 = S220c2 sess se eae } [ 4. White sandstone succeeded by hard bluish sandstone. -.-.....---. J ( 5. Bluish-gray laminated sandstones.......-.-..---2-2---. +--+ --+----- ho) 3) 6. Conglomeritic sandstone, gray below, becoming yellowish toward the top. There are pebbles of red jasper..--.-..-.---.------------ T50a9 7. Purplish and yellowish argillaceous shales........---.---.---------- 1 5) 8 Metamorphosed ‘conglomerate 222) 222) 32h ee ea ayes 390) | 9. Metamorphosed sandstone, white and greenish below, purplish above ; IDS someot thejlayersare,conglomeritic =, 2 2) 2S. e eee eee 77 = 9 | 10. Fine-grained, very compact, purplish sandstone, breaking into small ; | cubical Wlocks ies weet Ge oes Saisie 3 ay Seeie, Sa area arena ete AS | 11. Greenish and purplish argillaceous shales, in thin laminge..-.-...----- 11 10 | 12. Purple sandstone resembling that of No. 10, more laminated at the | 10). ee En RES Seay Ie Cheon UREN MME ENERO Aural ot Gira creui le MeO) (18. Purple ‘and yellow argillaceous shales 20! 5 TS3. Aula ena ie 10 0 @) 14) Greenish ‘trachyte iniimassive) layer. 22-2252: ee ee eee 18 (O ( 15. Greenish and gray shales, partly argillaceous......----..--...------ Te B. J 16.-Dull-ereenishcoarseysandstones) <2 2655) hasan ee ece ee eee eee eee eee en) * \ 17. Greenish and purplish mottled sandstones, generally compact, break- L ing into irregular pieces ; some layers are conglomeratic..-..---..- 30 =O 18. Compact purple sandstones, in bands of eight inches to a foot thick- ness, breaking at right angles to the plane of deposition. On the sur- faces quartz crystals are numerous. This bed forms the top of the © DOME ee cee epee teeta emis ae oe Gah ok Sica eee ea aa pe 88, 0 Total) abouts 222432 Josh pes aes SE ee ae eater le 883 8 Most all these sandstones have a metamorphosed appearance, and the ridge in which they are exposed is intersected with dikes, which will be “described in a subsequent portion of the report. Below the, strata of the section just given there are probably 1,000 feet of shales and sandstones to a series of coal-bearing strata on “Oh be Joyful” . Creek. The latter, according to Mr. Holmes’s estimates, is about 2,000 feet above the Dakota group. The upper portion of these beds may possibly have to bg referred to the Lignitic group, but for the present J reter them to the Upper Cretaceous. On one of the small southern branches of Anthracite Creek, near its head, is an outcrop of anthracite coal. We found the float in the creek- PEALE. ] GEOLOGY—UPPER CRETACEOUS—COAL. 139 bed, and followed it up until the bed was reached, near the head of the stream. The original discovery was made, I believe, by prospectors. The existence of coal of a good quality in the Elk Mountains has been known for several years. In the report for 1873 (page 259) I referred to it. The coal was exposed on both sides of the creek, the dip being nearly in the direction of the course of the stream, inclining about 25°. The beds are tipped up against the Trachytie range that forms part of the divide between Anthracite Creek and Ohio Creek. The coal is ina bed from 4 to 5 feet thick. The following is the section from the coal down: 1. Coal, 4 to 5 feet thick. 2. Black slates and shales, with interlaminated dark sandstones, reaching to the creek-bed, about 150 to 200 feet thickness in all. Above the coal is’a bed of sandstone, brownish near the coal, becom- ing lighter colored as we ascend. The sandstone is succeeded by light- gray sandstones and interlaminated dark shales. About 100 feet above the coal is a layer of porphyritic trachyte, which inclines with the sedi- mentary beds. It is probably an intrusion, as it resembles closely the trachyte from the various eruptive masses in the surrounding country. It contains iron, which gives it a rusty appearance on weathered sur- faces. The coal will be referred to in a subsequent part of the report, when analyses will be given. Coal is also found on Coal Creek, and at the head of Slate River, and en Rock Creek. It is all probably of the same age. In sandstone shales, near Mount Marcellina, I found a specimen of Ferrea sternbergii. Although I searched carefully, this was the only fossil I could find that was distinct enough for identification. This and the Aralia I found in layer 12 of section No. 17,0n Grand River, are the only fossils found in the series and do not warrant any definite con- clusion as to their age. The beds in section No. 17 have probably their equivalents in section No. 18, but in the latter they have been so changed that we cannot say so with any certainty. I have already referred to the possibility of a portion of this group being a part of the Fox Hills beds (No. 5). A part, also, may belong to the Lignitic group, (so named east of the mountains.) Since writing the above I learn from Mr. Marvine that he found a coal-bearing series of shales above typical specimens of No. 4 Cretace- ous, and that above the coal he obtained fossils referred to No. 5 by Prof. F. B. Meek. Dr. Endlich also found coal above No. 4 in the Cretaceous. It is therefore probable that the beds I LENG, for convenience, de- seribed as Upper Cretaceous belong to No. 5 From the lowest to the highest beds S exposed in my district I could find no unconformability. . OAR ih Von _STRATIGRAPHY—CENOZOIC FORMATIONS. 5 In the present chapter I shall take up the remaining members of the sedimentary series as exposed in our district. These consist mainly of beds referable to the Green River and Bridger groups of the Tertiary, and I shall consider them without entering into any extended discussion as to the exact names that should be given them, whether Eocene or Miocene. Professors Cope, Leidy, and Marsh consider them Hocene, basing this conclusion on the discovery of vertebrate organic remains ; while Lesquereux refers there to the Miocene from his investigations of their fossil flora, calling the “ Lignitic” group Eocene. I shall simply describe the beds, giving the local names of the groups to which they are referred. In regard to the “ Lignitic” group, I am unable to present any details. Farher discussion as to the exact age of the group will be found in the other reports. As to the Post-Tertiary formations, I am able to speak only in the most general way, and am unable to separate them into groups. TERTIARY. Above the beds characterized as Cretaceous by their lithological pe- culiarities and the occurrence of typical fossils, is a series of beds from 7,000 to 8,000 feet in thickness, covering a large area extending from the Grand River to the Gunnison beneath the basaltic plateaus west of Roaring Fork. This area is marked on map E. The best exposures are seen on Platean Creek. I had time only to male a partial detailed section. The strata are conformable to the un- derlying Cretaceous, and it is difficult to determine where one forma- tion endsand thenextbegins. I have arbitrarily chosen as the base of the Bridger series a bed of red sandstone that is tolerably persistent beneath’ the variegated beds above which the fossils were found. Another year I hope to define the limits of the formation. The lower portion of the series is referred to the Tertiary with some hesitation, as the fossils, a which were few in number, were found too far above to predicate any- thing very definitely. Before entering into any description of the groups as they occur in our district, I will give in tabular form the various views held by different authorities in regard to the beds that have been referred to the Tewgiary formations with the exception of those referred to the Pliocene. 140 PEALE. } GEOLOGY—-FORT UNION OR GREAT LIGNITIC GROUP. 141 Fort Union or Great Lignite group. Locality. At Fort Union, Fort Clark, and under the White River beds, on the North Fork of the Platte River, above Fort Description of strata. Age. Authority. Reference. Beds of clay and sand, with round terruginous con- eretions and nu- merous beds and seams and local Laramie, and west deposits of lignite. @ Wind River Mountains: 4 Pipes OMEISSOUTL T6-"|-22.5225.5 04sec uesue Merbialycs---.5- gion. | Miocene Tertiary. Lower Tertiary. ..|. Lower ‘Tertiary. .. Miocene .-.-.-..----- Merbiarysssse 5-2 Crétaceous.....- s Miocene s22e.c2=- MentiaLygesea.- +" IMioceneikere teaser Cretaceous No. 6.. | Lower Eocene .... EXTENSION DLO! blites |eese sso ae sce es eae HMOCENC ze eieseeene: ish Aimerica. Cretaceous. .....- Eeercupine *Oregk,«)..0.5sceseet Js 52 2 HOCEMC) eee ase ee Missouri Coteau, West Souris River, and other parts of British America. d , Lower Eocene ..-. WEN eeivby Ol coe toca 2o| et cceeeetae caches. ce Lignitic Tertiary - LUT LLCS SEA Gr ps a a rhe | ale (BX0) ead es a a eeeiracens Bastern baséof Black |.....-.-222¢222.222-2:|s22- COE eee Da SH. Hills. PeuRLVers, JING: |... 222 eels eth Cretaceous......-. braska, (now Da- Kota) LTS Cp ee 0 WC 2 en jOOe Reach pocser Lak e, Nebraska, (now Dakota.) inmenite of Big Horm. |02.22- 22226-00286.) 8 Orsi eee asthe Mountains, “and at Taouth of Big Horn River. Beds beneath White River beds, south of Fort Fetterman. North Platte River and La Préle Creek. Eocene Tertiary -- Lignite (Tertiary) WOCene te: 22/- sais eNO) Exploration of Yel- lowstone and Mis- souri Rivers, under Capt. W. FE. Ray- | nolds, 1859-’60; Hayden....--. Geol. Report of F. V. Hayden, p. 29. Meek and Hay- den. Proceedings Acad. Nat. -Sci., Philadel- phia, 1856, p. 63. Do., p. 225. .| Do., p. 113. Transactions Amer. Philosophical Soc., 1860. -do. Hayden. ve niees Ineidiy eae ees Do. Explor ation of Smoky Hill Railroad route, 1868, p. 65. American Journal of Sciences and Arts, 1868, p. 204. Transactions Ameri- ‘ can Philosophical Soc., 1869. Annals Lyceum Nat. History of city of New York, vol. ix, 1868. Report U.S. Geol. Sur- vey of Ter., 1867- 168-69, p. 57. pe Report U. 8. Geol. Sur- vey of .Ter., 1270, pp. 95, 96. peey United States Geol. Survey, 1873, p. 433. Report U. 8. Geol. Survey, 1872, pp. 410-417. Canadian Naturalist, vol. vii, April, 1874, 252. Lesquereux. .. G. M. Dawson. “The Geological Rela- tions ofthe Lignitic Groups,” read be- fore the American Philosop. Soc , June J.J.Stevenson 18, 1875. G.M.Dawson.| Report of British American Boundary Survey of Forty- ninth Parallel, BE. 6, 8, 18, 19, 86, 93, ; ey 152. WEL ON eet ecke Do., Hayden....... ROS eee? 8 Geol. Sur- } vey of Ter., 1867- "68-69, p 72 NETO eee Do., p. 73. eeCO ee LAs Do., p. 73 Copeest2222).) Report U.S. Geol. Sur- vey of Ter., 1873, p. 446. Hee GQ teas salietas Do., pp. 453-4, sh2ido 22234h 82 Do., pp. 453-4. Hayden. -..... Report U.S. Geol. Sur- vey of Ter., 1870, p. 16. een Oe scene Do., p. 22. 142 GEOLOGICAL SURVEY OF * THE TERRITORIES. Fort Union or Great Lignite group—Continued. Description of strata. Locality. Age. Authority. Reference. Coal biedisvunder |25-.055-e2se scence: Lignite (Tertiary) | Hayden..--.---. Report U.S.Geol] Sur- White River beds, vey of Ter., 1867- near Fort Laramic 68-69, p. 79. and east of Rock Creck. earamienplain saonen|soseeseseeceee see cece Lignite (Tertiary) SOW Seca Report U.S.Geol.Sur- hundred miles west vey of Ter., 1870, of Fort Laramie. p. 121. * Coal-bedsvot (Carbon)|ii22 22-2. et acee cae -||- cent i gubsasscsoddal)- Ad Over Report U.S. Geol. Sur- and Separation, vey, 1867, 68, ’69, p. Wyoming Terri- 190. tory. At Separation and | Yellow, rusty yel-|.--.do ..........--. o1eQO) da setts se Report U.S. Geol. Sur- surrounding coun- low, rusty brown, Lower Eocene. vey, 1870, p. 139. try. Probably same and drab beds. at Carbon, Rock Creek, Cooper 2 Creek, and Creston. Carbon! Stationeesect «| [tence sase oe clei =e Lower Miocene -..| Lesquereux...| Report U.S. Geol. Sur- vey, 1871, p. 206. Upper Eocene >. ..|:---do..---22-- Report U.S. Geol. Srr- vey, 1871, pp. 410- 417. Middle Miocene. .-|..--do ...-:---- Report U.S.Geol. Sur- vey, 1873, p. 366. ’ Middle Miocene..-|.-..do ......--- American Journal of Sciences: and Arts, vol. vii, June, 1874, Isicnitevbedsseast offset mccccecsse sees see Lower Tertiary. -..| Hayden. .-...-- Report U.S.Geol.Sur- Washakie Station. vey, 1870, p. 74. Eocene BapeopASoss Lesquereux.-.-| Report U.S. Geol. Sur- vey, 1871, p. 306. NWestiof Washakie,)|..-...---.5---<.------ Lignite Mortlany Ai Easy dent eeneys Report U.S. Geol. Sur- and in Bridger vey, 1370, p. 74. Pass. Coal-pedsieastiotiSalt 2. cccos erence coc eet Eocene ...:..-..--- Se Onsaceahiates Report U. 8S. Geol. Wells. Survey, 1870, p. 71. @oal-beds\ lo fapRock [Poss eececeeseaniastecer| Lignite Tertiary..|..-. does sae e |e: Do. Springs, and east of Rock Springs and Salt Wells. Henry’s Fork of |Animmensethickness| Eocene ...--...--. 33 COS ee ee Report U. S. Geol. Green River. of sandstones and Survey, 1870, p. 58. clays, extending from Green River beds to Cretaceous clays. OnjStaVirainis\Creek, -|=- 295 se4-csee- cease Lignite Tertiary -|....do ..--.---- Report U. 8. Geol. east of mountains Survey, 1867-’68 in Colorado. ‘ -’69, p. 127. ereball MINVENCOLO-| [s. oi eee om eeee Mertiaryssoee ee se Aeee Oieaseanete eee Do., p. 129 rado. HocenePersece aes LeConte ..---- Exploration ofSmoky Hill Railroad route, ; 1868, p HOCENC Fase nee sees Lesquereux il enone Ga 'S. Geol. ° Survey, 1871, p. 306. Halston (Creekssnear, |i: Seale ee Mertianyeee-e es Hayden. ...--- Report U. 8. Geol. Golden City, and Survey, 1867-68 Golden City. -69, p. 134. Goldom@ ity tae. is| easca ce etseese nee WOCeDe Se aes ae ee Lesquereux Report U. S. Geol. Survey, 1871, p. 306. Lower Eocene....|... do ..-------| Report U. S. Geol. Survey, 1872, pp. 410-417. Bedsywunder Denver, |t22-s25-2-4-4- 25 5-e ae Mertiaryicses er Hayden. ...-.- Report U. S. Geol. Colorado. Survey, 1867-68 ~'69, p. 137. PAT Ox GeO te OMG Ds | So ey aeice ae oeee cells LEO is sees eee eee Bac) Seaqsaeesl base Do., p. 188 Platte River from i mountains. Near Colorado Springs]............---------- American Lower | Lesquereux...| Report U. S. Geol. Eocene. Survey, 1873, p. 366. Hardscrabble Creek, |).2.-..--2--.-22--02-2 enbiany eee eeee ee Hayden...---. Report U. S. Geol. near Caton City : Survey, 1867-68 (Caiion City group). ~'69, Pre 149 to 190. NeanCanon)Wityeecas |sasoeocceeee sees cose American Lower | Lesquereux. -. Report U.S. Geol. Eocene. Survey, 1873, p. 366. Coaltbedssote Raton) eee pe seers sees Great Lignite! Hayden....--- Report U. 8. Geol. Hills (called Raton Hills group). group. Survey, 167-68 ~'69, pp. 150 to 190.” South Park.northeast ot Fair Play. Grand River, in Mid- die Park. Mount Bross, in Mid- dle Park. Troublesome Creek and Willow Creek, in Middle Park. Troublesome Creek and Monnt Bross (Middle Park). Middle Park, Mount Bross. Placer Mountains, south of Santa Fé, New Mexico(Plac er Mountain Group). Lignitic bedsof New Mexico (at least as far south as Placer Mountain). An- thracite coal. Lignite bedsof New Mexico and San Juan. Sandstones and clays overiying Creta- ceous layers. Yellow and gray sandstones and Jaminated arena- ceous clays. Upper Cretaceous Lignitic Tertiary. - Lignitic Tertiary Older Tertiary .* ..|.-.. Lower Tertiary ---|- American Upper Eocene or Lower Miocene. Upper Miocene...}. Lower Tertiary - -- American Lower Eocene. 4 Cretaceous.....--. J.J. Stevenson Lesquereux... Newberry --- reate.} GEOLOGY—FORT UNION OR GREAT LIGNITIC GROUP. 143 Fort Union or Great Lignite group—Continued. . Locality. Description of strata. Age. Authority. Reference. IRARLOMENCOS Tso ers 2528 sacccucs see Sets omese Cretaceous.....--.| LeConte...... Report Exploration Smoky Hill Rail- road route, 1868, p. 66. Apishpa Creek, Span- |........-....----.---. Tertiary .-.---.-.. avd eneeee sea ee Do., p. 153 ish Peaks,and Trini- dad, Colorado. Raton Pass, IHRE | Gonaonesoseaoecgscesas HOCENGpyaseniee cee Lesquereux...| Report U. 5. Geol. tory Caiion. Survey, 1871, p.306. PArOneNTOUNtAINS .<. |--.<~-2.cvessecnsece Lower Eocene ....|..-. dojseaense ys Report U. S. Geol. Survey, 1872, pp. 410-417. @Geal-heds Of (Ow sib || 2-- coco ee ce: Lower Tertiary...) Hayden......- Report U. S. Geol. edge of mountains Survey, 1867-68 in Colorado. -’69, p. 189. iisher’s Peak, Raton |...........2.2scbecce- IH OCen eyes oeeecee- Lesquereux Supplement to Fifth Mountains. Annual Report U.S. : Geol. Survey, ae ratonMonntains:))5 <0 2225-5 .> --.-:.- Se edOySeecmceee Do., p. 42 er and the Uintah Mountains. Bridger’s Butte, near | Somber-brown indu- | Bridger group..... moni) sakingeode Do., pp. 55, 56. Fort Bridger, and| rated arenaceous divide between| clays, gray and Smith’s Fork and} rusty- -brown sand- Henry’s Fork otf| stones; leaden- Green River. brown clays. Between Smith’s and | Indurated clays ; in- | Above Lower Mio- |....do ......--. Do., pp. 58, 59 Henry’s Forks of| tercalated with| cene beds. Green Riverandin| the clays are beds Green River Valley.| of rusty-brown and gray sandstones, all tending to a con- eretionary struc- tnre. Church Bnttes ..-..-- Brown indurated | Middle Tertiary, |....do.......-. Do., pp. 144, 145. sands and clays. probably synchro- nous with White River beds. Fossils, Miocene ..| Meek ......--. Do., pp. 298, 299. Echo and Weber | Conglomerates.....- Probably parallel Hayden.) Do., p. 168. Valleys. with Bridger group (Upper Miocene). Wear South Bitter |2.2:--<-7. cess oenies Upper Miocene ...|....do..-.-.-.-. Do., p. 75. Creek at La Cléde. ‘ | Mocen@neoesesee si Coperecaneceas Report U. S. Geol. Survey, 1873, p. 437. LEG ia Ye! JOC AE ee ee eee ee Upper Miocene ...| Lesquereux.-.| Report U. 8. Geol. Muddy Creek. Survey, 1871, p. 306. Dull-colored indu-| Upper Eocene -...| Comstock ..--. Report of Reconnais- rated clays and brownish, dull-yel- low, or gray arena- ceous layers, with more or less concre- tionary structure. sance of Yellow- stone River and Northwestern Wyoming, under Captain Jones, 1875, p. 127. 150 GEOLOGICAL SURVEY OF THE TERRITORIES. White River group. Locality. Description of strata. Age. Authority. Reference. On White River, un- | White and light-drab | Miocene..-........ Hayden ....--.. Geol. Report of Ex- der Loupe River| clays with some ploration of Yellow- beds, and on the] beds of sandstone, stone and Missouri Niobrara River,]| and local layers of Rivers, by Dr. F. V. and across to the} limestone, and Hay yden, under Platte River. whitish indurated Cant W. F. Ray- clays. nolds, 1859-"60, p. 29; also Report U.S. Geol. Survey, 1867- 62-69, p. 57. On White Earth| Variegated beds, |.-..do............-].--. doyesce eee Exploration of Yel- Creek and White | creaim-colored, rea- lowstone and Mis- River. dish-brown, and souri Rivers, p. 134. light-gray sands and marls. , In the valley of the | Light-colored marls | White River Ter-|....do ........- Report. U. S. Geol. Chug-Water, on] and sands. tiary. Survey, 1867-’68-69, Horse Creek, and p. 80. onthe North Platte. ‘Beds beneath) Cheyne e 2 ciejss ace sicicice cases Sb oath) a oodbsoeacedd Base) Seasneaee Do., p. 110. enne. On the Chug-Water |.-......--.---..-----. WEKOveie dace e sees eau Ole mranicia'siae Report of U. S. Geol. and Crow Creek. Sao 1870, pp. 13, Along the North, and |.-.....---.-.-----.--- HAO) sens eweiee ss SOHO Oy chee De. , pp. 19, 20, 23. on La Bonte and Horseshve Creeks. Movi Hettorm anys ses Weta msisieiee seis eiectae Se aSO Ole te ctoaieje meals AO aectias Do., pp. 23, 24. 400 miles northwest |..........-..-..------ Eee OW acne isc Rtas Bele Oveiiaisle save « Do., p. 121. of Fort Laramie. Miocene..-..-..-.-. Leidy ....----. Report U. S. Geol. Survey, 1871, p. 353. Plains west of Chey-| Drab, yellow, and | Miocene (?).-...--. Hayden .....--. Report U. S. Geol. enne. light-gray sand- Survey, 1873, p. 17. stones, marls, and clays. Miocene.........-- Cope ees Do., p. 461. The “Monument Creek” and the “Gallisteo Sand” groups deserve mention here. The latter ers been referred to the Miocene by Dr. Hayden (Report U.S. Geol. Survey, 18676869, pp. 139, 167, 190.) — It consists of ‘‘ variegated sands and sandstones, and light. reddish brick- red, purplish, yellow-white, brown, and drab, with irregular layers of dull rusty-brown concretionary arenaceous limestones.” It will be noticed that this description resembles those already given for the Green River and Wabsatch groups. In the report of U. 8S. Geol. Survey, 18676869, p. 139, 140, Dr. Hay- den points out the resemblance of the Monument Creek group to the Gallisteo Sand group, and to the beds between Fort Bridger to Weber Canon (Wahsatch group), and refers it to Late Miocene or Pliocene. He makes the same reference in the report for 1870, p. 161. In the report tor 1875, page 33, he refers it to Miocene. In Bulletin No. 3, Second ‘series, he refers it to the Lignitic group, butin Bulletin No. 4, p. 19, he corrects this statement. Prof. E. D. Cope (Report U.S. Geol. Survey 1873, p. 430) says: “The age of the Monument Creek formation in relation to the other Tertiaries not having been definitely determined, I sought for vertebrate fossils. The most characteristic one which I procured was the hind leg and foot of an Artiodactyle of the Oredore type, which indicated conclusively that the formation is newer than the Eocene. From the same neighborhood and stratum, as I have every reason for believing, the fragment of the AMegaceratops coloradoensis was obtained. This fossil is equaliy conclusive against the Pliocene age of the formation, so that it may be referred to the Miocene, until further discoveries enable us to be more exact.” The columns on the opposite page are summarized from the tables that have already been given: 151 CRETACEOUS AND TERTIARY STRATA. GEOLOGY PEALE. | “SIITH XOY—'S "ON ious i ; ; LOATYT % : = ‘dno STL ° dnoas [vod LOA WoeIy) dnois S| [tel XO qvog pur ‘nog “IT Spoq S[TLH XO XOT ' LOAN wvog puv oT[LATvoO = ‘ood 109}1q—'9 ‘ON i ae ‘d 3 . Se ‘spoq Aoatyy 09TH NOIS LOAN WOOL) SOLIDS YOoID 10991 a ‘dnoas 9310 B 5 “BVT Way Lo UOT) yeaa Ss ‘QoL JO OLOM 10 4uvg SS = : ty “SOIUST] 5 st OOIXOW MON IOAN Avog puv oy[raTeoD | 2 q eon Yoo yy y = : ‘moLyeardos £]voo 10g | =n P | ‘SOLIOS YOOID LOJIIET JO Jav ‘OUMATIVET | & E | avo Ssuiseq-[voo CorxoTT AON pur s dnoad sod py3g, By ‘dnois 1ospug ‘oyu Povtd | FA] opesojog ‘uorsoa tmossryy soddq & ‘spoq er) OPLAOLOH WAOTYIAON pu [vagwoy iS) 3 UIseq YeyUTy—) 5S jo ursvg ‘AgIg uouvg fsUurLjUNOy_ uopEyy 4 P 1S on el . b> E oe Toad 5 . ‘ Sen e§$ “duod BS Oe ODO e COTS Oe @ 8 IOAN woo !dnowsd yoousyR AL 4 aS; 7 us) oO 5 ica eam ‘oy ‘dnoad wary ont A\| ‘dnoad aoary o9IT AA ‘yoorQ YOO 2 ‘SOLIOS YLIOID LOPE JO WUT eae j-dnoad AAT PUTA St “dnoad oryuyseay {woo woqarg o Stel YAVT OTPPUAL og fTPOUVA 8,OT[OISVH puN GUVSSMIO[P «wou ‘yarug ‘dows csp !dnois LoaAyy oPAL | 3s yyuog f aon ‘oxpor FO peoo Sdnoas aoayp woewy 8 g add Q “Snod0vJOID | | 92000 “gUe001L “‘Burnok MA WOO A, | “VOMMOULy YON 89 AA ieee as ‘odor *xnoadonDsory uo pAUTY *y[00)9UL0(—) 152 GEOLOGICAL SURVEY OF THE TERRITORIES. It will be seen, on referring to the column headed Lesquereux, that beds of the Bitter Creek series are in part under Miocene, and in part under EKocene. The reason of this may be that the specimens are from different horizons, or, if from the same horizon, it would seem to prove that there is a mingling of forms in the flora of Eocene and Miocene formations. It is probable that when more complete collections are “made, this will be found to be the case. That the coal-beds of these localities, however, belong to the same horizon is evidently the opinion of Dr. Hayden and Prof. F. B. Meek, who have studied the localities stratigraphically. (See references in tables). LIGNITIC GROUP. West of the continental divide the coal-bearing strata are not con- fined to the Lignitic group (as named east of the mountains). As noted in the preceding chapter, I found lignite in the sandstones of the Dakota group. In 1873 Mr. Marvine* found a “thin seam of coal” “a few hundred feet above the quartzitic sandstones of No. 1,” at the *“* Hot Springs” in Middle Park. During the season of 1874 Mr. Marvine found coal in a horizon above fossils of No. 4 and below those referable to No. 5. Dr. Endlich, in his district, recognized three distinct lignitic layers in different horizons of the Cretaceous formation. ‘The coal of ‘the Elk Mountains is probably of the age of the Fox Hills group. IL have already referred to the possibility of the upper part of the series there, in which the coal is found, being apart of the Lignitic group, but, until fossils are found, I refer it to Upper Cretaceous. Professor Newberry t found lignite in Lower Cretaceous and in Jurassi¢ strata in Northeastern Arizona. In Minnesota, also, coal has been found in Lower Cretaceous rocks. The reason of the differences of opinion as to the age of the disputed beds called lignitic seems to be that there are two sets of lignite-bearing beds close together, one belonging to the horizon of the Fox Hills beds of the Cretaceous or possibly a little above it, and the other belonging to the horizon of the Fort Union group (Lower Hocene). As Prof. G. M. Dawsont says, “* An observer beginning his study of the beds on their eastern margin, and proceeding westward, as Dr. Hayden has done, would be completely justified in placing the whole series, at least down to the top of Cretaceous No. 5, in the Tertiary; while a geologist familiar in the first instance with the fossils of the underlying Cretaceous formations, and following the lignite strata eastward from their appear- ance in the Rocky Mountains, would in all probability include the whole series in the upward extension of the Cretaceous, though doubts might begin to assail him before he reached the upper or most eastern beds.” In many places the coal of the upper part of the Cretaceous appears to be absent. When present the sandstones have a transitional char- acter, but this is also noticed where coal is found in the lower part of the Cretaceous formation, and in the Jurassic, just beneath. Professor Cope refers the lignite-beds to the Cretaceous formation from the dis- covery of the reptilian fauna in them. He has described a Dinosaurian reptile from the Bitter Creek series,§ and also from the Fort Union group in Colorado.|| Professor Meek says, ‘‘ Aside from the Dino- * Report of U.S. Geol. Survey, 1873, page 156. t Colorado Exploring Expedition, Geological Report, pp. 83, 85. | ¢ Geological Report on the Region in the Vicinity of the Forty-ninth Parallel, p. 202. § Proceedings of the American Philosophical Society, 1872, p. 482. || Report United States Geological Survey of the Territories, 1873, p. 444. {] Report United States Geological Survey, 1872, p. 461. ~ PEALE, ] GEOLOGY—LIGNITIC GROUP. 153 saurian, the organic remains favor the conclusion that it (Bitter Creek series) is, Tertiary.” Professor Lesquereux, from the study of the flora as we have already seen, refers the beds to the Eocene period. Cope, in his conclusion, (Report United States Geological Survey, 1873, p. 447), says there is, then, no alternative but to accept the result that a Tertiary flora was contemporaneous with a Cretaceous fauna, establishing an uninterrupted: succession of life across what is generally regarded as one of the greatest breaks of geologic time. : linsert here a letter from Prof. Theodore Gill, on the value of the Dinosaurian remains, as proof of the Cretaceous age of the strata in which they are found: SMITHSONIAN INSTITUTION, Washington, January 9, 1876. DeEaR Sir: Your letter, requesting a copy of my communication to:the meeting of the National Academy of Sciences respecting the values of fossils as indices of forma- tions, has duly come to hand. My remarks were not published otherwise than in brief newspaper reports. They were elicited by the controversy then prevailing respecting the,age of the lignite-beds in which the Dinosaurian remains, to which you allude, were found. The substance of my criticisms was that we should not be too much influenced in our views as to the age of any group by one or two including fossils; and I brought up a number of cases to show how mistaken we should be if we allowed ourselves to be too much influenced by what was known of the paleontology of any limited country. Among other in- stances, I especially alluded to the fact that for a long time the fish, genus Ceratodus, was regarded an indication of a not later than Triassic age of any including forma- tion; and showed that while such is the case for the northern hemisphere, so far as yet has been observed, we still have living Ceratodi in the southern hemisphere, not long ago discovered. I proceeded then to show the close relation between the species of this group, which lived in Triassic Europe, and the species which live in modern Australia. JI further indicated that the remains of Agathauwmas, found in the lignite- beds, were not sufficiently characteristic to enable us to determine the exact relation- ship of the genus, and that it was apparently not, at least nearly, allied to any of the previously recognized forms of the order. The conclusion was drawn that inasmuch as the same typical structure could persist and had persisted, with shifting geographi- cal relations, through such long ages as had Ceratodus, that in the case of the Dinosauri- ans, where the affinities were less intimate, there could be no a priori reason why they might not have had asimilar history. It was in fact assuming the premises in dispute to assert that because the remains of the Dinosaurian were found in a given horizon they must necessarily indicate Mesozoic age, notwithstanding the other associated fos- sils. I finally urged that in this case, where the evidence was conflicting, we would have to wait for further proof from other quarters, and especially for the tracing of peuuite horizons toward, and co-ordination with, those above and below the beds in ispute. I adduced a number of other facts bearing on the subject; but this will be sufficient to show the drift of my argument and the evidenee of the facts set forth. Hoping that this epitome will answer your purpose, I remain, yours truly, THEO. GILL. Dr. A. C. PEALE. Cope also says,* ‘The appearance of mammalia and sudden disap- pearance of the large Mesozoic types of reptiles may be regarded as evidence of migration, and not of creation. Itis to be remembered that the smaller types of lizards and tortoises continue, like the crocodiles, from Mesozoic to Tertiary time without extraordinary modification of structure. Itis the Dinosauria which disappeared from the land, driven out and killed by the more active and intelligent mammal; herbivorous reptiles like Agathaumus and Cionodon would have little chance of suc- cessful competition with beasts like the well-armed Bathmodon and Metalophodon.”” Tf the smaller types persisted, why not the larger? The only reason he gives is that they would have little chance of suc- cessful competition with the well-armed mammals. Why should this not * Report United States Geological Survey, 1873, p. 442. 154 GEOLOGICAL SURVEY OF THE TERRITORIES. apply also to the smaller? He says also that paleontology confirms Hayden’s conclusion that there is no evidence of any catastrophe suffi- cient to account for any sudden and complete destruction of life. The change from marine waters to fresh water accounts for the destruction of the marine invertebrate life, but, as Hayden* says, ‘the vertebrates of the Lignitic period having great powers of locomotion, and being able to live on rand as well as in the lakes and marshes of that time, and as we have shown that there was at no time any important catastrophe or phys- ical changes sufficient to affect them, could well have prolonged their exist- ence farup into the Lignitic eroup, carrying with themas aninheritance their Cretaceous characters.” Noone form ot life should be taken asa basis of classification. Cope’s comparative list of vertebrate species;t under Colorado and Dakota, includes two species of Plastomenus, a Tertiary genus, although in a foot-note he says he so refers them provisionally. The fauna, therefore, even according to his own list, is not exclusively Cretaceous. Writing to Prof. G. M. Dawson on some remains found in the lower portion of ‘the Lignitic formation on the forty-ninth parallel, he says:t ‘¢Thisis a characteristic collection of the reptiles of the Fort Union Cretaceous, but with increased admixture of Eocene forms. Plas- tomenus is an Eocene genus, but the reference of the new species to it is not final. But you send two Eocene gar scales which have every ap- pearance of belonging to the same formation. Will you re-examine your notes to inform me whether they really belong to the same horizon as the others ?” Dawson says:§ ‘ The gar scales referred by Professor Cope to the genus Clastes, were obtained at the very base of the Lignitic formation and below the lowest lignite-bed.” ‘ Dinosaurian bones oc- eurred within a few feet of them.” We have already seen that the coal-bearing strata at Coalville and Bear River are undoubtedly Cretaceous. The only reason to be given for in- cluding the different groups in one formation is the fact of the presence of coal; and we might, then, include all coal-bearing strata, whether Carboniferous, Triassic, Jurassic, Cretaceous, or Tertiary, inthesame. In this case the -lignitic strata are very close together ; and in fact one im- mediately succeeds the other. This is also the case at the base of the Cretaceous in some places. Professor Newberry,|| referring to a bed of lignite of Jurassic age in Northeastern Arizona, says: “‘The sandstone, shales, and limestone lying above, also include many beds of lignite closely resembling this, and on lithological grounds would appropriately be grouped with it. In fact they have been considered Jurassic, and the only Jurassic rocks in this region, by the geologist Marcou, who claims to have discovered the representative of this formation in New Mexico. Unfortunately, however, for that classification, immediately over the hin stratum of yellow sandstone which overlies the coal, are beds of clay shale, with bands of limestone in which are unmistakable Cretaceous fossils.” Plants of the lignite above were dicotyledonous, while those found below “are closely allied to some of those most characteristic of the Jura and Upper Trias of Europe.” 4] The base of the Cretaceous formation is therefore seen to resemble the base of the Tertiary. In Eastern Colorado the upper part of the Cretaceous is destitute of coal. In fact the Upper Fox Hills group is wanting in many localities, and *Notes on the Lignitie group of Eastern Colorado and portions of Wyoming, Bulle- tin No. 5, second series, United States Geological Survey of Territories, p. 411. t Report U.S. Geol. Survey of Terr., 1873, ] p. 433. t Geol. Report Forty-ninth Parallel, p. 200. § Ibid. || Ives’s Colorado Expedition, Geological Report, p. 83. {| Ives’s Colorado Expedition, Geological Report, pp. 83, 85. PEALE. ] GEOLOGY—LIGNITIC GROUP. 155 sometimes the Lignitic group rests on No. 4 or No. 3 Cretaceous.* I _ have aiready (page 145) referred to the equivalence of the Judith River beds and some strata at the eastern base of the Rocky Mountains, west of Greeley and Evans, Colo. The fossils upon which Professor Meek predicated this equivalence “‘came from the very upper beds of well- defined marine Cretaceous, and beiow the horizon of all the coal-bearing strata of the Colorado region.” t ‘ In the report of United States Geological Survey for 1872, p. 459, Pro- fessor Meek speaks of the resemblance of some of the fossils from the Black Buse and Point of Rocks localities, to some species found in the brack- ish-water beds at the mouth of the Judith River. They would seem, therefore, to be equivalent to those seen east of the mountains west of Greeley. He says they are distinct from any found at Coalville or Bear River. In speaking of Black Butte it must be remembered that there is also a Black Butte station at which the beds are probably not of the same horizon. Point of Rocks, Hallvilie, and Rock Spring are not all of the same horizon. In going from Table Rock to Salt Wells (see re- » port ot H. M. Bannister, U.S. Geological Survey, 1872, p. 524), we go down through a fresh-water series to brackish-water beds and finally to ma- rine Cretaceous at Salt Wells, which is in an anticlinal. Speaking of the coal horizon of Point of Rocks, Bannister says:f ‘‘1t seems almost too low in geological position to be referred to the horizon of the Hall- ville beds, although it may occupy the same.” Meek, in the report for 1872, p. 408, refers them to the same horizon, although in the re- port for 1871 he refers Point of Rocks to the Cretaceous and Hallville to the Eocene, from the affinities of the fossils. Until the stratigraphy of the region is thoroughly investigated there must remain some little doubt. Professor Meek, in his table of fossils of the Bitter Creek series,§ evidently considers the Point of Rocks locality at the lower part of the series. Professor Meek|| has identified some fossils from two hundred miles east of Greeley, Colo., as the same that are found over one of the coal-beds at Hallville, Wyo., and at Black Butte Station, Utah. He says: “That the formation from which these fossils came, however, is the same as the Bitter Creek series of Wyoming, including the Black Butte beds, the Hallville coal-mines, Point of Rocks, and Rock Spring coal-mines, &e., I have scarcely a Shadow of doubt.” It remains now to state the following conclusions: 1. The lignite-bearing beds east of the mountains in Colorado are the equivalent of the Fort Union group of the Upper Missouri, and are Eocene-Tertiary ; also, that the lower part of the group, at least at the locality two hundred miles east of the mountains, is the equivalent of a part of the lignitic strata of Wyoming. 2. The Judith River beds have their equivalent along the eastern edge of the mountains below the Lignite or Fort Union group, and also in Wyoming, and are Cretaceous, although of a higher horizon than the coal-bearing strata of Coalville and Bear River, Utah. They form either the upper part of the Fox Hills group (No.5) or a group to be called No. 6. 3. That the upper part of the Fox Hills group is wanting in many parts of Hastern Colorado, and when present seems to be thin and des- titute of coal. * Hayden Bulletin No. 5, 2d series, U. S. Geological Survey of the Territories, p. 404. t Bulletin No. 1, 2d series, U. S. Geological Survey, p. 40. } Report U.S. Geological Survey, p. 532. § U.S. Geological Survey, p. 477. | Bulletin No. 1, 2d series, p. 42. 156 GEOLOGICAL SURVEY OF THE TERRITORIES. TERTIARY BETWEEN GRAND AND GUNNISON RIVERS. The only portion of the district in which Tertiary rocks are seen is in the region between its two main streams. I have no absolute proof that the Lignitic group is present. At all the localities I visited, the intermediate bed’&S from the upper part of the Fox Hills beds to the red sandstone bed that I took as the base of the Green River and Bridger series were covered. The Lignitic group may include a portion of the beds above and a part beneath. Itis impossible to define any line of separation. Although I could see no unconformability betWeen the Cretaceous and overlying Tertiaries, it is probable that in other places evidences will be found, especially on the edges of the Tertiary basin. In a conglomeritic sandstone on Plateau Creek I found an inner convolution of a Scaphite. It was a pebble, and proves that the layer in which it was found, is of Post-Cretaceous age, its materials com- ing from. the disintegration of Cretaceous rock which were above water- level when the stratum was deposited. GREEN RIVER AND BRIDGER GROUPS. I shall use the name Green River group to include also the Wahsatch group of Hayden. Cope restricts the name to the Green River shales. Whether we call them Eocene or Miocene depends upon the view we take of the beds below. The vertebrate palentologists consider them Eocene, while all who hold to the Tertiary age of the Lignitic group place them in the Miocene. As has already been stated, the greater portion of the Tertiary beds exposed in the district is referable to the Green River and Bridger groups. These strata are seen between the Grand and Gunnison rivers, west of Roaring Fork, and are almost horizontal, dipping slightly to the eastward beneath the basaltic-capped plateaus, which are fully described in other portions of the report. The area is shown on map HE. The characters of the included rocks will be given as we proceed. The best exposures are seen on Plateau Creek, a branch of the Grand River, which joins it some distance above the mouth of the Gunnison, after cutting deeply into the strata. The following section will give the best idea of the succession of the strata on Plateau Creek. No. 19.—Section of Tertiary Beds.—Plateau Creek. Thickness Base. Ft. In. RECT SANAStONE ssa 5-1 setoae wieteiealemniee les eeisel ce aie teens eee eatseeeal ) “Yellow-and, white sandstones.ssss-1-- oss es see c eee beeen m= aie .Redisandstone: 30 feet: 2. ace SORE hi, 2 SURO I Rear ees eres eae | Variegated red, yellow, and bluish marls, sandstones, and clays..-.-.... Blnish and black argillaceous beds.-..-..-.--2-. sc 2c 20 wceeme enw ee cans | 5B NEW PER HOCISRaWYs) 6 BG AS Gassce Seoeau oso Baar nnosboDeSaeS osbeoRDSonKe o= : . Black argillaceous beds ..---..-.- SEER BSBA DIA Se Gon ool oada colueas baoc IL: . Brownish red! sandstonewas ae sme soe sas) sale eeiee Selec eater lalla eee 72,000 0 . Soft greenish argillaceous shales .-.. 2: . 2.00.5 2-5 --ca esos ome mine = one | 10> Greenisandstoneishalesise: oes een soe ee tee eee asec aeaiseaer eee | (DID OP 09 0 i _ . Black argillaceous)shales 22 U0 00 1 to ee ease oe one . Massive sandstones in pinkish-white and yellowish-gray fayers, — [\) with interlaminated greenish shales. Some of the.layers are GOA MEIN Sony Boones Sonos o OobeERaooEusoood 460566 acon assaae . Dark greenish shaly sandstone...-.. 2... -.---. 220-2. .2----'------ ------ J . Series of soft variegated beds, yellow, reddish, and black, much like those given in lower part of this section. They are generally concealed, but where exposed the débris, from the softness of the strata, makes it almost impossible to get the section in detail. Thickness about -...... 740 O° 250 | ee 1m Oo PEALE. ] _ GEOLOGY—SECTION OF TERTIARY STRATA. 157 thick, in the center. The shaly layers are fossiliferous, containing frag- AMENTS OL) PONES tay | ais Sas Bis Le SOP Ce ee toe eae was Wah ee eth Sees. 100 34. Red and greenish sandstone, weathering into rounded masses ...-.--.-.-- 10 35. Green and red sandstone shales with intermediate bands of sandstone.... 46 36. Red and yellow mottled, rather massive, sandstone, weathering in rounded ATT ASSOS Pyne eee Soe ea ett ee pe ea, 23 Gah Pe DL Ai a Ohh hae 5 Eri ardelark-STeenish SANGSLONC)= = -\555--eijoee ota see niomia | Swic la able eee 30 Bene nTecular sandstones: 52225). 55 Fae xe Y, Vi AV EASE En CEs Ears) [7 ee eS 1 Geen Ge SE C= ee ee eee 2 BAN YG Uy C7) \N Wi; My,“ Ys ‘> SY = re SR Eee Nae a Wi f c D7 f AB ~ Section R. EF Section O. Shewing Areas of Rhyolite and Breccia . PEALE. ] GEOLOGY—BASALT—EAGLE RIVER. Thal I have already stated that the origin of this trachyte and breccia is in Dr. Endlich’s district, south of the Gunnison. Since it was poured out, the mass of mountains described under the head of Porphyritice Trachytes have been thrown up, which fact accounts for the abrupt bending of the trachyte northeast of station 79, and the general slope toward the Gunnison. The subsequent erosion has been sufficient to remove the trachyte around station 51, and on the ridges running southward from this mass of mountains. The amount of the denuda- tion on the Gunnison is measured by the distance between the top of the mesas and the level of the River. BASALTIC AREAS. The basaltic rocks of the district all closely resemble each other. They are generally dark-colored, gray to black, and are fine-textured. They contain olivine, sometimes free quartz, the latter not abundantly, and on being pulverized magnetic iron can be extracted from them. The latter always caused a great deflection in the needle at all stations made on these areas. Vesicular varieties occur in many places. The different varieties, however, will be described as we proceed. The short- ness of the time at our disposal in the preparation of this report pre- cludes the possibility of giving definite analyses of the rocks. As already stated, the basaltic rocks are confined to the northern part of the district, where they generally form the capping of plateaus or mesas, showing that they are lava-flows. Their source was probably to the northward, as, with the exception of one locality, I could find no evidence of their having originated within the limits of our region. As the general features of the country have been already given ip considerable detail I will confine myself mainly to the description of the rocks and their mode of occurrence. Eagle River —On the summit of the ridge southwest of the Hagle¢ River, opposite the second cation, there is an isolated area of volcanic rock which I call basalt, although I could discover no olivine. Its ap- pearance, however, closely resembles that of the rocks in the same re- gion that are undoubtedly basaltic. It is dark bluish-gray, rather com- pact, with a slight tendency in places to lamination. There are a few points of free quartz and numerous yellow spots of some decomposing mineral, which may be olivine. The area occnpied by this rock is lim- ited, comprehending only about nine square miles.. It is shown on map A. A section across it is shown in Fig. 1, Plate I (f tog). It will be seen that it rests on the upturned edges of the Red Beds, and in places tonches the Jurrassic or Cretaceous layers. The section in the figure is partly ideal, but I think it presents the true relations of the rocks. It seems that there must have been a fissure through which the mate- rial was pushed, and afterward spreading out, it covered the edges of the Strata tipped up by the same force that caused the flow. If it is simply a flow that has spread over the upturned edges of the strata it must have come from the north. The hills north of Hagle River shown at ee, in Plate II, are capped with volcanic rock. It isnot probable, however, that this rock is the same flow, although it may be of nearly the same age. Wecannot be exact as to the age, although it is probably com- paratively modern. All we can say positively is that it is Post Creta- ceous atthis point. I think this flow and the one near the mouth of Eagle Ktiver were contemporaneous. The latter, as I shall show, is of recent date. It is near the mouth of the river on the north side, and, although outside of the limits of our district, I wish to refer to it. A more de- tailed description will be given by Mr. Marvine. The flow had its Source in the hills on the north side. It came down the ravines and 172 GEOLOGICAL SURVEY OF TIIE TERRITORIES. spread out in the valley, covering a space of three or four miles. It forms a bluff edge 10 to 20 feet above the level of the river. A speci- men of the rock that I obtained is a black vesicular basalt containing free quartz and olivine. Cn pulverizing it I obtained a dark, almost black, powder from which magnetite could be separated. This rock is of comparatively recent date, which is evident from the following reasons: First. Tie flow has taken place since the carving out of the valley. It occupies the bottom of the valley, which is nearly two thousand feet in depth, bordering the river like the slag poured out from a furnace. The river seems to be the limit of the flow, none of the rock being found on the south side. It was probably pusbed by it to the lower side of tle canon-like valley. Second. The subsequent erosion bas been very slight. The basalt is exposed in a bluff-like wall which reaches to the level of the water, nothing being exposed beneath it. Third. The basaltic rock is destitute of vegetation and comparatively free from any soil. It has the appearance of having just been poured out. The period during which it was poured out is probably to be meas- ured by hundreds of years, and per aee less, rather than by longer periods. Grand River.—Below the mouth of Bagle River on the south side of Grand River there is an area of voleanic rock that has been subjected to considerable erosion. This area was probably once continuous with that west of Roaring Fork. Between a creek, Grand River and Roar- ing Fork it rests mainly on beds of Triassic age, forming a plateau-like surface. Near the mouth of Frying-Pan Creek is a mesa capped with basalt which is probably a portion of the same flow. This latter, how- ever, rests on beds of Cretaceous age, as does the volcanic rock west of the Hog-backs on Roaring Fork. They are all probably remnants of the same flow. The amonnt of erosion previous to the spreading out of this material was very great. The Cretaceous rocks near the Grand, between Roaring Fork and a creek, seem to have been entirely removed. The subsequent erosion also has been of great extent. The present valleys and canons have probably been outlined since, and the amount of de- nudation is to be measured by their depth below the level of the vol- canic rock. The capping of the hills west of Roaring Fork is very irregular. There remain only the remnants of what was once a connected mass. Station 16 was located on the western edge of one of the patches of basalt. In almost all of the valleys drained by the southern branches of the Grand, between Roaring Fork and the plateau of station No. 48, there are ereat numbers of voleanic bowlders, derived from the hills that are capped irregularly with basalt. The hills themselves are so covered with débris that it is difficult to define the” boundaries of the basalt. The plateau on which station 48 is located is also capped irregularly with basalt. Since the flow it has been subjected to a great deal of erosion, and now the basalt is found only in isolated masses, like that on which we made station 48. The latter is a mammallary process rising 248 feet above the general level, and about 200 feet in diameter. The fellowing is the section of this curious horn-like point, which can be seen from a great distance in every direction: * 1. Dark-gray basalt, containing a large quantity of olivine, also free quartz sparingly. It is a very hard and compact rock. 2. Purplish basalt. This layer is slightly vesicular. It contains the same minerals that are seen in No. 1. PEALE. | GEOLOGY—BASALTS—PLATEAU CREEK. 173 3. Vesicular basalt. Mostly red in color on weathered surfaces. Some of the pieces found at the base are black, and have cavities lined with carbonate of lime. 4, Tufaceous layer, of which only the upper portion could be seen. The color is white, and in some places the layer has masses of basalt. In layer No. 1 I found the following minerals, besides those mentioned above: Hyalite and quartz in segregations and pyrites coating the weathered surface in a few instances. All these basaltic rocks have magnetite. The local attraction on the station was considerable. The cone on which station 48 was located is situated in an isolated patch of basalt of the same character (see map 3). There are several other areas from which pointed and coffin-like masses rise, none, how- ever, reaching the altitude of station 48. The basalt, as has been men- tioned in a previous chapter, rests on dark-gray shales which weather to a chaiky whiteness. This is beautifully shown on the north side of the Grand. It was impossible to tell from the station how extensive the area covered by the basalt is to the north. On this plateau the area does not exceed eighteen or twenty miles. To the westward it reaches its limits at least five miles east of station 50. West of the basaltic line the plateau becomes broken; the capping having been re- moved, the soft beds beneath yielded readily to the eroding influences, and, therefore, instead of a plateau there is a sharp ridge, gradually de- creasing in elevation to the westward. The course of the range, for it forms a very well-defined range, is generally west. Itis very irregular, however, and the streams on either side cut profoundly into the strata. Station 48 has an elevation of 11,063 feet above sea-level. Two and a half miles west the top of the basalt is 150 lower, and two miles farther, that is, four and a half miles west of station 48, it is 350 feet below it. So we see there is a slope to the westward at present. We cannot tell whether this is the original surface, or whether it has been modified by subsequent erosion. It is probable, however, that the original slope was to the westward. We see the same decrease in elevation from east to west on the plateau between the North Fork of the Gunnison and Plateau Creek. On station 43, which is one of the most eastern of the basaltie points on this plateau, the elevation is 11,134 feet. At station 44, one mile farther west, it is 11,128, while on station 45, eight and a half miles west of station 43, it is only 10,954, a decrease of 180 feet. Five miles west of station 45 the elevation is 10,904, which is practically the same as that of station 45. Sixteen miles west of this point, at the north ond of the mesa, the elevation is only 9,800 feet, and at the south end, which is three and a half miles farther east and sixteen miles south of the north end, it is 9,733 feet. This is a fall of a little over 1,400 feet from station 43, in a distance of about twenty-seven miles. The greater part of the decrease in elevation is in the western portion; that is, in the last twelve miles. As is evident, on glancing at the figures given above, the eastern portion varies but little on comparing the higher points with each other. About stations 43, 44, and 45 the basalt forms points that rise considerably above the general level, while the sur- rounding country is very much broken up. To the westward, however, the basalt forms a mesa-like capping to the country. This mesa is Somewhat irregular in outline, forming at first a narrow strip which divides into two arms, one extending to the southwest and the other to the northwest. They are separated by a small creek that drains into the Gunnison. Ithas cut gradually deeper and deeper until the basaltic capping has been removed, leaving a tongue-like process of Tertiary rocks between the arms. In the eastern part of the divide the areas covered with basalt are 174 GEOLOGICAL SURVEY OF THE TERRITORIES. ; ¢ irregular. The highest points in these areas hardly mark the original surface of the flow. The subsequent denudation has been enormous, as will be readily conceived when we compare the elevations of these points with those of the deepest valleys near them. Stations 45 and 48 are almost on a line with each other running north and south. This line also passes through our camp No. 45 which was on Plateau Creek. Comparing the elevations of these three points we find that the creek at camp 45 is 3,891 feet below station 48, and 3,870 feet below station 45. Farther down, the distance from the north end of the mesa to the level of the creek is over 4,000 feet. The south end of the mesa is 4,677 feet above the level of the Gunnison at a point due south of it. These figures will give some idea of the immense amount of material that has been removed since the flow of lava took place, and show also how improbable it is that the original surface still remains. The two plateaus that we have just described are evidently the remains of what was once one continuous mass. The elevation of station 48 is practically the same as that of station 45. On comparing the rocks from the two localities, we find that they are identical in appearance and in structure. We have also seen that there is the same slope to the west on both. If they had not been connected we would find traces ot the flow in some of the valleys, but we search in vain for any such evidence. No basalt is seen in the valleys save the bowlders that have been carried down from the plateaus. What the original limits were it is impossible to tell. It is difficult to get at the exact thickness of the basaltic flow as originally spread out. At present it is probably considerably less. At station 48 the total thickness is 248 feet. This is the highest point on that plateau but it hardly represents the original thickness. The thickness at the north end of the mesa is 100 feet. The latter may not be absolutely correct. It was determined from station 57 by angles to the top and base of the abrupt wall of the mesa. The actual base may be covered with the talus so that it is concealed. As to the age and the source of the basalt we cannot say anything very definite. It is, however, in all probability comparatively recent, although older than the flow mentioned as occurring near the mouth of Eagle River. It rests on sandstones and shales of Tertiary age, which were but little affected by erosion previous to its pouring out. I was unable to fix on any point as its source; I think, however, that it lies farther to the north. The surface of the plateaus is covered with good grass, and groves of cottonwoods and pines, among which there are numerous beautiful little lakes. Both of them are very well watered. Near station 45 are three beautiful lakes, two of which head streams flow- ing to Plateau Creek, and one heading a branch of the North Fork of the Gunnison. Near station 45 there is a beantiful illustration of the effects of cooling, in the hexagonal columns into which the mass has separated. They are very regular, and are five or six feet in diameter, The surface of the mass inclines to the northward. The edge of the mesa portion of the plateau is very abrupt, eapecmile. on the western side, and at the extreme northern and southern ends. It stands out like the wall of a fortress. The outlineis irregular. The accompanying map will give a good idea of it as also the areas covered by the basalt. Fig. 3, Plate LX, shows a section made from the edge of the mesa to the Gunnison. On the line A B of map H, a represents the capping of basalt. In all the valleys of the streams heading in the mesa there is an abundance of bowlders of basalt. They are SO numerous in some places, even on the long sloping spurs running from it, that it is difficult to determize the underlying rock. 5 g Sees J = p ee Vy) e Q x< e >) y Lil cos = : o LZ] . i} ~ WD = | ~< oN Fo 2 S4le gS = = a Ss ; @ wm e +S e- 3 nw . 4] © J, x7 3 4 Bd My ete iS Ly < = § , “yyy ] V7 Gouve" CHAPTER IX. ECONOMICAL GEOLOGY. The greater portion of our district, with the exception of the area along Eagle River, lying within the limits of the Ute reservation, of course no mining operations can lawfully be carried on. Indeed, the areas in which mineral-deposits are found are limited to the group of mountains in the southeastern part of the district, and to the gneissic rocks about the head of the Eagle. The remainder of the country is covered with sedimentary rocks, mostly of Cretaceous and Tertiary age, in which mineral-deposits are rare. Lignite is found, but, with the ex- ception of that near station 34, it is of poor quality. GOLD. On Eagle River we met a party of prospectors who claimed to have found gold in placer diggings in paying quantities on some of the streams flowing into the Eagle from the south, below the mouth of the Piney, and above the second cation. On the North Fork of the Gunnison, southwest of station 26, we met another party, who said they tried the dirt, aud that the colors were good. SILVER AND LEAD. The Elk Mountain mining district was described in the report for 1873. The ores are mainly silver-bearing galena. There are doubtless numerous lodes similar to them at various points around the heads of Slate River and Rock Creek. We did not have time to make a detailed survey here. The rocks are penetrated in all directions by dikes. At the head of “ Ob be Joyful” Creek, east of station 32, Mr. Holmes got a specimen of galena associated with pyrites. On the other branches ledges would probably be found on searching for them, as the rocks are similar. COAL. Lignite is found at several points in our district. At the mouthof the Gunnison, and in the bluffs on the river from the mouth to the mouth of Roubideau’s Creek, it is seen, but of poor quality. This lignite is of Cretaceous age, being found in the sandstones of the Dakota group. On Coal Creek, a branch of Anthracite Creek, a bituminous lignite is found in sandstones, which I have referred to the Upper Cretaceous. Two specimens from this creek were examined, with the following results: Analysis. Specimen Specimen No. 1. No. 2. 5 FE. ead ie ee aan ial abel tar tah eg oi Seah i Ne pape aOR 5.04 2 : TS BITS, SBT AE Scie ae dee Aaa aes he le | ico a nN A 31.46 Hoe 4 Lit acd cleelaia ee fect = SL, eat leah lll lle lt ae ae 59.50 59.68 See cee ome ea) aS ie nlite ce Ulta a a Bn ie De a 5.00 4.30 100.00 100.00 This coal is black (brownish-black in powder), has a dull luster, and an irregular fracture. The ash is of a light-reddish color. The analyses 175 176 GEOLOGICAL SURVEY OF THE TERRITORIES. show that the coal compares favorably with the lignites found in other parts of the West. Anthracite Oreek.—In the report for 1873 I spoke (page 259) of the oc- currence of anthracite coal in the Elk Mountains. It is found at the heads of Rock Creek, Slate River, Anthracite Creek, and Ohio Creek. It is probably all of Cretaceous age, and was doubtless originally a bituminous hgnite. The coal at the head of a small branch of Anthra- cite Creek was found in a bed from 4 to 5 feet thickness in sandstones. The section has been given ina preceding chapter. These sandstones were tipped up against a range of trachytic peaks, and between the Jayers of sandstone, some distance above the coal, is a layer of trachyte. The strata dip at an angle of 20° to 25°. This coal is probably a portion of the same bed from which the coal on Coal Creek was ob- tained, although in the latter case it is lignitic. The eruption of the trachyte found near the coal first mentioned probably so heated it as to deprive it of the bituminous matter. This coal from the head of Anthracite Creek has a submetallic luster, is black even in powder, and has a conchoidal fracture. Analysis No. 1. MYVGNGE Sed sa5 ob Sdc0 noob Ab poddou Hono muoode HootED GaooUd bRoo bon doose5 2. 00 4.50 Molatilepmatters\ce =scecinsrssteae ea ciioe ee sees Seinise nae 2. 50 : (ORWAOM ses OSs esos 6oou d666 oben 6sobe4 Hobhb5 de56 S666 BoD SSH EER an eC UNE 91. 90 Ash (of a dark reddish-brown).....--.---.- ses eats 3. 60 i 100. 00 Analysis No. 2. Wicuber) ese ha heen eae clean gee li oN ee ae 1. 60 5.00 Wolatileimattersey-(2y--ete crossed the day previous. We found the whole country flooded. Natu- rally very boggy, the ground was now so full of water that it almost floated. The next morning the rain still continued. As the supplies were get- ting short so fast, we concluded to strike the nearest way for Howard- ville. Moreover, we were getting disgusted with this part of the coun- try, and wanted to find a better camping-ground. Accordingly, we moved up the main branch of the Vallecito. It was running considera- ble risk, as without a trail to guide us we felt doubtful about being able to cross the divide. The rain fell fast, and we were soon soaked to the skin. The grade being very steep, we rose in elevation very fast, and soon found snow and raix falling together, and we nearly froze. Westopped at one place and made a fire by which to warm our feet, but the wood was so soaked with water that we found it a difficult task. Tbe train was behind — and did not catehup ; so Wilson and I heaped all the logs that were lying handy upon the fire, and, as we found later, the rest of the party made good use of the fire. Near the head of the creek the slope became very steep and rose up to the divide, which, at the point at which we- RHODA.] GEOGRAPHY—QUARTZITE PEAKS, ~ 478 crossed it, was nearly 13,000 feet in elevation. A keen, strong breeze did not serve to add to cur comfort in our present saturated condition. While waiting here for the train, Mr. Wilson made station 24 on a point east of that where we crossed the ridge. The elevation of this place is about 12,700 feet—a little higher than the point where we crossed the same divide a few days ago. We traveled down that branch of the Rio Grande which heads between stations 24 and 25, and camped in a Splendid grove of pines. In the afternoon the sky had begun to lighten up. Isolated clouds passed swiftly over us from the west, ever and anon cutting off the sunlight, and producing the sudden chilling effect always noticeable in the shadow of a cloud at high altitudes. The great difference of temperature in the sun and in the shade at these alti- tudes is very remarkable. At this particular time I thought I noticed that whirls and gusts of wind always accompanied the fast-moving shadow. Whenever a long space between clouds aliowed the sun to shine unobstructed, for some time the air would be quite still, but the next cloud-shadow seemed to bring with it little whirlwinds and chang- ing gusts of chilly air. By the time we had unsaddled our animals the sun was shining brightly, and now, after four days and three nights of incessant rain, we had a good opportunity to dry our clothes and blan- kets, and every one made good use of the short time before sunset. In the evening, instead of sitting down to a hearty meal, we had to make our supper on bacon and dried apples alone, and very short rations at that. We had afew beans left, but all the bacon and apples were used up for supper; but as we expected to reach Howardville the next day, we did not mind it very much. Our bill of fare next morning pre- sented only two articles—beans, which on account of our elevation could not be well cooked, and sugar. We could take either or both as we chose. Beans with other food are very strengthening, but alone we could scarcely eat them at all. The pack-train started direct to Howardville, while Wilson and I climbed the most northern of the quartzite peaks, a point having an elevation of 13,576 feet above the sea. The day was clear, still, and beautiful. After riding as far as we could, we still had about a thousand feet to climb on foot over the steep débris slides before reaching the top. We soon discovered that our breakfast of beans and sugar formed a poor foundation for such hard work. Once on top, a row of ten distinct peaks stretched in a nearly east and west line before our eyes. Their ruggedness may be understood from the illustration of “the Quartzite Peaks from station 38,” the three or four on the left of the picture being just in front of us from station 25. Being much nearer, they appeared much more rugged than from station 38. The peaks in this row range from 13,560 to 13,831 feet in elevation. Between them we could see the higher peaks to the south. The great and essential differences in the topography resulting from the change in the geological formation is here so very marked and is so interesting that I cannot pass it by without notice. The general differ- ence in the appearance of the country in trachyte and quartzite forma- tious is intended to be shown by the two large topographical sketches presented in this report. The view of Mount Sneffels from station 29 shows nothing but trachyte rock, while the sketch from station 38 shows quartzite only. Buta mere sketch cannot show well the characteristics of the two. I have tried to work out some of the features peculiar to the topography of each of these two formations. These being derived almost wholly from observations in Southern Colorado and for the great part in this particular region, they may pot Hea a very general appli- cation. A474 GEOLOGICAL SURVEY OF THE TERRITORIES. First, then, in trachyte or voleanic rocks, the lava-flows being for the - most part horizontal, the rock fractures vertically, and the falling away of pieces produces bluffs which are generally very nearly vertical. More- over, from the uature of the flow, horizontal lines or bands are left run- ning across the faces of all the bluffs. This latter is very characteristic of the formation. Second. At the bases of the bluffs débris slopes commence, and sweep down generally in graceful curves to a greater or less distance. Third. These slopes are seldom very steep for any great distance, the great fall from the mountain-summits to the valleys being by way of high bluffs and comparatively gentle débris slopes. In other words, the total fall is very irregularly distributed over the distance from the top to the base of the mountain. Fourth. The junction-line of the bluffs and débris slopes is almost always distinctly marked. On the other hand, in quartzite formations— First. Bluffs vertical, or nearly so, are very common; except in very rare cases there are no marked horizontal lines. Second. The junction between the bluffs and débris slopes is never so distinctly marked as in trachyte. Third. On account of the fact that this rock breaks off in large angu- lar fragments, and also on account of its great hardness, it will lie at a much steeper slope than the other rock. From the same causes the loose rock does not take on those beautiful sweeping curves so common in volcanic rocks, but have a certain stiffness of line. Fourth. The solid rock, from its great hardness and the manner of its crystallization, is often found in very steep, yet quite irregular slopes, without taking on the form of bluff. A noticeable instance ef this is the most easterly of the ten peaks mentioned above. The fall from its summit to Vallecito Creek on the east is 3,000 feet in less than a mile horizontal, or a mean slope of nearly 32°; yet itis a plain slope of solid rock, more or less irregular, of course, but having no bluff in all that distance. On the north side of the same peak there is a slope at an angle of 60° to 80° for not less than 2,000 feet, yet there is no part of it bluff. Still another point is the fact that in the metamorphism of the origi- nal sedimentary rocks into quartzite, the great natural convulsions at- tending that process have distorted the strata terribly, so that, as in this particular region, a number of peaks in a small area may each have its strata dipping at a different angle from all the rest. The effect of this on topography may be seen in thé sketch from station 38. The high peak next to the last one on the left shows in a marked manner that the strata incline to the right, or southward. The high peak near the middle of the sketch, being in the center of upheaval, has vertical strata, while those farther to the right incline to the north. This lat- ter fact is not so well shown in this sketch, but from some other points of view it appears very plainly. These facts show how the form of the peaks may differ in the same kind of rocks; but as there is little or none of this upsetting of the lava-flows, there must result a distinet type of mountain-form for each, The peculiar crystallization of the quartzite has also a marked effect on the forms. In accordance with these facts, we find that quartzite mountains are generally much more rugged, but lacking the relief given to those in voleanic regions by the ‘contrast of the. bluffs with the débris-slopes.- The boundary of the quartzite on the north follows closely the national ivide = RHODA.] GEOGRAPHY——HEAD OF UNCOMPAHGRE RIVER. AT5 On our return to Howardville we rode across the rolling ground which extends southward from Cunningham Pass. Arriving at the town, we found Mr. Jackson, the photographer of the expedition, with his party. He had just arrived from the Los Pinos agency. We made the ascent of Sultan Mountain with him, and he succeeded.in getting a number of good photographs of the surrounding country. From this point is ob- tained by far the best view of Baker’s Park that is obtainable from any peak in the vicinity. ~ After getting our supplies we marched up Mineral Creek, while Mr. Jackson struck south over the trail which passed around the west side of Saltan Mountain, and made a very interesting investigation of the old ruins in Southwestern Colorado. In the afternoon rain fell, and continued into the night, but the next morning was cold and the sky clear and beautiful. This date (Septem- ber 3) is remarkable as being the time of the abrupt change between summer and fall. After this, till the snow-storms commenced, the weather was cold and clear. Having camped overnight at the junction of Bear and Mineral Creeks, the next morning we moved up the latter, and made stations 27 and 28 ona high ridge between Mineral and Cement Creeks. Camping near the head of the creek, ‘the following day we crossed the pass at its head and passed over to the head of the Uncompahgre River. The elevation of this pass is 11,100 feet above the sea. It is entirely covered with timber. The slope to the south is quite gradual, but to the north, down the Uncompahgre, the fall is 800 feet in two miles. Then for several miles the stream flows comparatively smoothly, till it finally enters a deep box-canon, where the fall is, very great. ‘Traveling for some distance is both difficult and dangerous. At the bottom of the first steep slope a great area of fallen timber commences. The logs so cover the ground that traveling is very nearly impossible. Leaving a notice for the pack- train to camp near the beginning of this dead timber, Mr. Wilson, Dr. Endlich, and I rode on, and finally got through the timber, when we had open grassy ground to travel over, but the slope was so\steep that we could ride only a small part of the way. Leaving our mutes loose, as usual, to find what grass they might at this elevation, which was a little less than 13,000 feet, we made station 29, on a round-topped peak, which, being surrounded by peaks higher than itself, is of no great importance. It was taken as a station, because its position. between two of the main branches of the Uncompahgre made it a key-point for the drainage system which forms the head of that stream. Its elevation is 13,206 feet. From this poifit we got by far the best view of Mount Snef- fels, and the curious pinnacle-forms in its vicinity, which have already been mentioned as seen from station 10. The accompanying illustration, taken from a hasty topographical sketch, will give a faint idea of the great peak and its vicinity. Of course the elevation and ruggedness of the mountains shown in the sketch can only be appreciated by a per- son who has climbed many mountains. Even then the air is so clear at these high altitudes that one is deceived in spite of himself with regard to distances. From here we could see no feasible route by which to climb the great Mount Sneffels, so we laid the question aside till a view from some peak farther to the west should solve it shtisfactorily. Next day we retraced our steps over the pass and down Mineral Creek, camp- ing again atits junction with Bear Creek. Moving up the latter stream, . we camped on a considerable branch which comes in from the north. This is probably the finest camping-ground on the whole stream, with fine timber, good water, and a sufficient quantity of grass. Above this e 476 GEOLOGICAL SURVEY OF THE TERRITORIES. there is a dense grove of timber, through which you pass up a pretty steep slope; in a short distance the pines end, and you come out into an open space, extending severai miles up the stream, and coy- ered with a remarkably rich growth of weeds and shrubs. This circumstance is probably explained by the fact that here a great part of the lower slopes of the cation is composed of red sandstone, which seems to produce a much better soil than the voleanic rock. The next day (September 6) we made the ascent of the highest peak in this vicinity. It is marked station 30 on the map, and has an eleva- tion of 13,897 feet. The climb was difficult, on account of the long slopes of loose débris up which we had to climb. The top of the peak was remarkable for its smallness. It is formed cf two knobs, about 20 feet apart, the northern one being a little the higher, and connected with the other by a very sharp ridge. To the west was a slope of .60° or 70° for 30 to 40 feet, then a precipice of about a thousand feet nearly, if not quite, vertical. When the tripod was set up, we could not pass around it, but had to crawl under it. We three monopolized all the sitting and standing room on the peak. Mr. Wilson with the instrument completely covered the true summit. Dr. Endlich took his geologi- cal notes from the lower knob, while I sketched, sitting at the edge of and almost under the instrument. The slopes, on ail sides but the narrow path we had followed, were very steep, and in a few feet terminated in great precipices. From here we got a splendid view of Meunt Wilson, which we had seen from many stations before this, but always across the group of mountains of which station 30 formed a part. Now it rose up grandly, forming the most massive of any peaks in our district, and, judging from its appearance and rough estimates from the angles of elevation, we felt that it must be very high. In line with the peak, but several miles nearer, appeared Lizard’s Head, a peculiar pinnacle, which from this view appears quite . broad. It will be more particularly noticed farther on. After finishing our observations, we built a small monument of loose stones, which, when finished, covered the top so completely, that a person could not pass around it. We descended more easily than we had ascended, aud found camp at the lower end of a long patch of timber, near the junction of the main stream with the last tributary which comes in from the south as you travel up. This marks the upper end of the open, weedy area already mentioned. The total climb from our last night’s camp to the station was 4,000 feet, and the descent to our present camp 3,200 feet. On the day following we let camp remain where it was, and rode up the creek to the south of us, and over the divide, to Engineer Mountain. On the way we had to pass around a peculiar amphitheater, which had been eroded out of the red sandstone. The stratification of the sandstone had produced benches, which extended all the way around the head of a little stream which flows into Cascade Creek. We found the ascent of the peak not very tiresome, but rather dangerous. We climbed up the ridge from the east. On our right was the great bluff, which is nearly a thousand feet in height and almost vertical. On the southeast side the rock weathered off in small plate- like fragments, producing innumerable cracks and little shelves, but none large enough’to give a secure foot-hold. The slope on this side is very steep, so that if a person should slip he could not possibly save himself from destruction. Mr. Prout in 1873 ascended this same peak from the south side, which I should judge is much the safer, but at . the same time the longer and more tiresome way. From this point we had a splendid view down the Animas. Animas Park was visible, and ee RHODA.] GEOGRAPHY—HEAD OF SAN MIGUEL RIVER. ATT the low country in its vicinity showed us that the high mountains were nearly at anend. A group of pretty high peaks were to be seen to the southwest, called the La Plata Mountains. They are completely isolated from the main mass of the range by many miles of comparatively low land. On our return to camp a sudden and heavy shower of rain came up, but cleared off soon after. The next day found us on our way through the patch of timber already mentioned. The trail passes through the center of the group, which is very swampy, and our animals mired many times before we got through. We found relief only at the timber- line, after which we rode on, over grass and fine rock-slopes, up to the pass, which has an elevation, according to our aneroid barometers, of 12,600 feet. It is certainly the highest of all the passes leading out of Baker’s Park. A pass which I think will be found much better, crosses the range about six miles to the northeast of this. To go this way you must travel up the lergest tributary of Mineral Creek, which comes in from the west, and cross over on to a tributary of the San Miguel. This pass is not less than a thousand feet lower, and, at least to the west, has a much better grade. Passing over from Bear Creek to the head of the San Miguel, after a sudden descent of several hundred feet, we came toa small lake. Further down, the slope was more gradual for some distance, till we came to a steep débris-slide, down which the trail led to the valley below. The fall from the pass to the valley, by way of the trail, is 2,800 feet in two miles. On the east side of the pass the rise from the stream-junction, where we camped, to the pass is 2,000 feet in two miles. Station 30 rose up boldly just to the north of us as we rode down the trail. Its side was worn out into beautiful forms, and the delicate blending of the dull red and yellow colors of the rocks, taken together with the long sweeps of the débris-slides, gave this peak a finer ap- pearance than any we had yet seen. Once down in the little valley be- low, we found trees and grass growing very luxuriantly. The trail crosses several boggy places, over which our mules passed with difficulty. A few miles down stream from the head of the little valley is San Miguel Lake, a very beautiful sheet of water, filled with fine trout. We stopped to make a compass station on the edge of the lake, and took a reading with the mercurial barometer, which makes the elevation 9,720 feet. Thence we traveled down the San Miguel river, along a very old, disused Indian trail; in some places, con- siderable trees lying across it showed that it had not been used for many years. For some distance below the lake, the San Miguel, which is here a pretty large creek, flows quite gently; but further down the slope suddenly increases, and the stream is broken up into falls and cascades. In going down the trail, at this point, we found the slope so steep that we had to dismount and lead our mules, till we reached the bed of a large creek which comes into the San Miguel from the east. After crossing this the trail ascends tke north slope of the caiion, which is quite steep. The total fall, from the lake down to the junction of this creek with the main stream, is about 900 or 1,000 feet in a distance of two and a half miles. At least 600 feet of this fall takes place in the last mile. At the bottom is a fine fall, which from a distance we judged to be not less than a hundred feet in height. After crossing the cafion of the creek above mentioned we came out on a pretty smooth area, covered with scattering timber and fine grass. One thing very peculiar about this particular part of the country is the deathlike stillness thut almost oppresses one in passing through it. 478 GEOLOGICAL SURVEY OF THE TERRITORIES. There is the finest growth of grass I have ever seen in Colorado, with beautiful little groves of pine and quaking asp scattered about, which one would expect to be full of game. The old trail and ‘the very anti- quated appearance of the carvings on the trees, and the absence of all tracks, old or new, indicated that the Indians had abandoned this route long since. With all these conditions, so favorable to animal life, we did not hear a bird twitter in the thickets, and saw neither deer, elk, nor antelope, nor even a single track of one of those animals. In all other parts of the country little squirrels and chipmunks were seen in abun- dance; but here, if they existed at all, they kept themselves close. We made camp on the large east fork of the San Miguel, just across the stream from station 32 on the map. The next day, September 9, we made station 52, on a low hill on the north side of the creek, which from its width might more properly be called a river. Above this for several miles the stream-bed is very flat and covered with willows, while the stream itself winds like a great snake. A short distance below our sta- tion the stream plunges down very abruptly into the cafon of the San Miguel, which, above and below this junction, cuts down from 800 to 1,000 feet into the sandstone which here makes its appearance. Leaving station 32 on our way to Mount Snefiels, we followed the trail a short distance, and then, turning off to the right, with great diffi- culty succeeded in descending to the bed of a creek flowing from the northeast. In this vicinity we saw a band of six gray wolves, the first we had seen during the season. With great difficulty we followed up the eaiion, which gradually be- came narrower and more rocky. In some places we had to cross over short spaces of smooth, almost polished rock-surfaces, inclined toward the stream. In one such place a small rivulet of water flowed over the surface and terminated below in a fall of considerable height. The smooth stone, thus wet, rendered our passage with the mule-train very hazaidous, as the least slip would have resulted in the certain destruc- tion of an animal, and possibly serious injury to members of the party. As we traveled upward the trees became more and more scattering, and the huge rock-slides, which below we had only seen high up against the mountain-sides, began to extend their fingers, like glaciers, far below the timber-line, and in many places reached the bed of the creek. These slides, ever and anon crossing our path, rendered travel very difficult for animals; the more so as they were composed of large angular frag- ments, often many tons in weight, and containing in their interstices no vestige of soil or vegetation. Sometimes we were able, by filling in the Spaces with small stones, to form a rough trail over these. At others, we were able to go around them. The obstacles to our onward march continued to grow ereater and greater till we came to the upper verge of a clump of trees, and found our further progress completely barred by the great débris-slides on both sides of the creek, coming down to the water’s edge, making the passage for animals an utter impossibility. About half a mile farther on we could see the trees commence again; but this strait, if we may call it such, was too much for us. Besides, we could see no prospect of good grass for the animals ahead, while this last group of trees formed a beautiful camping ground, and was overgrown with a rich crop of grass. There, then, we made camp; and as it was early in the afternoon, and the sun shining brightly, we took this rare opportunity of spreading out our blankets to dry. Wilson turned out his mule with the rest to feed, and walked on over the rock-slides, up the cafion, to reconnoiter, and after a long and tiresome walk reached the summit of the pass at RHODA.] GEOGRAPHY—ASCENT OF MOUNT SNEFFELS. 479 the head of the gulch, and saw, far across, a curious sink-like amphithea- ter, the object of our journey, looming up in terrible blackness before him. He saw at a glance that from our present position the peak must be ascended in one day, from our present camp, all on foot. The mount- ain had to be climbed, and the only easier ascent was from the north. But to get to that side of the mountain necessitated a circuitous journey of several days around the portion of the mountains jutting out to the west. On his return to camp in the evening he reported the result of his deliberations to the rest of the party, and it was concluded to make the ascent from our present camp. We all knew well that the winter-storms would soon commence, and we could ill afford to lose the time necessary to go around to the north side of the mountain. The present camp is marked on the map as camp 40. ASCENT OF MOUNT SNEFFELS. The next morning we provided ourselves with lunches, as was our custom, and the three of us set out on foot at six o’clock, with our note-books and instruments. The first portion of the climb - to the pass above mentioned, was in a northeasterly direction from camp. After crossing the portion of débris already described we came again to timber, then to soil covered with very short grass but devoid of other vegetation. After leaving the timber we could see about us, and a dreary sight we saw. Near us was nothing but these great angular fragments of trachytic rock, which, in the distance, faded to a dull, dreary, gray tint. In some piaces these slides formed long, regular, slightly curved lines; in others the stone appeared in swells like sand-dunes. The head of the canon was amphitheatrical in form, like almost all in lava regions. On the east side we noticed particalarly a sub-amphitheater, which, being composed of nothing but the loose débris, variegated by neither shrub nor blade of grass nor even barren soil, nor by any change of color in the rock, presented one of the most desolate sights that meets the eye of the mountain-climber. The weird stillness of high altitudes, only served to heighten the appearance of desolation about us, and gave one the idea that all nature was dead. Passing from the small area of soil over which we traveled after leav- ing the timber, we came again to the loose debris. Take note of that little patch of soil, for we may not step on soil again tiJl we return at night from our tiresome climb. We now had to walk over the loose bowlders, stepping irom stone to stone. This was very tiresome, as we could not reiax our attention for a single moment for fear we should step on a balanced stone, and fall or slip on some smooth surface. Toward the last, the ascent became very steep, and we had to climb with great care. The last few hundred feet was just about as steep as loose rock would lie. We thought nothing of this, however, as we were fresh, and knew, besides, that this was the easiest part of our day’s journey. We reached the pass at Jast, and as we had been climbing till then in the shadow we were glad to see the sun rising clear and beautiful. Every- thing seemed to conspire to make a beautiful day, and we lacked only time to let our imaginations run on and make a sublimely-romantic pic- ture of sunrise at a high elevation. The claw-marks on the rocks, on either side of the summit of the pass, showed that the grizzly had been before us. We gave up all hope of ever beating the bear climbing mountains. Several times before, when, after terribly difficult and dangerous climbs, we had secretly chuckled over our having outwitted / 480 GEOLOGICAL SURVEY OF THE TERRITORIES. Bruin at last, some of the tribe had suddenly jumped up not far from us and taken to their heels over the loose rocks. Mountain sheep we had beaten in fair competition, but the bear was “‘ one too many for us.” After stopping a few moments to draw our breath, we had a little leisure to look around us. Looking back we could see the clump of trees, 3,000 feet below us, in which camp was situated; while in front of us, and behind us, and around us, appeared nothing but miles and miles of loose rock, with rocky peaks everywhere. Immediately in front of us was a curious depression, which, at its lowest point, was about 2,000 feet below us, although we were standing on the lowest point of the ridge surround- ing it. It covered several square miles in area; it seemed to be com- pletely closed up, as no outlet could be seen. It was apparently walled in on all sides. On our right a bluff ran clear around to the great mountain, and was very nearly vertical for full a thousand feet, at some points more. For three miles from this pass, along the ridge on the south side of the amphitheater, no point is less than 13,500 feet in elevation, while several . peaks rise above 13,700, and one above 13,800 feet. Just to the south of Mount Sneffels was another comparatively low gap, which we felt was passable for good foot-climbers. This and the pass on which we stood were the only visible outlets; excepting these two, which were only just passable to men on foot, we could see no break in the great Chinese wall around this little empire of desolation and death-like stillness. We knew, of course, that there must be an outlet, and we knew where that outlet must be, but we saw none; we knew that the wall around the south side from us to the great peak, was continuons, and we could see that there was no break in the north wall for a considerable distance. The only point we were not sure of was at the northeast corner of the basin, just west of the peak. We were certain the outlet must be there, merely because we knew it could be nowhere else; however interesting it might have been from a geological point of view, it made our hearts sink within us to look at it. Im making the ascent of a mountain, there is nothing more painful than to find a deep gorge or sink crossing your path; you know that all the distance you go down must be climbed up again before you reach once more your present level. We did not remain on the pass long enough to think half that I have written, for it has always been a maxim with us that every minute saved in the morning brings us back to camp so much earlier in the evening, and we can never tell how long a climb is going to take us. We find sufficient time while climbing to observe the scenery around us in a very general way, but the romance of our work is not fully appreciated by us till we reach civilization, where we can find leisure to think over what we have seen; at the time no romance is visible. Almost due east of us and across the sink, at a distance of three miles, was Mount Snefiels, the end and aim of our labors. We traveled over the sunken area a considerable time, as it is several miles across. As we went on, it became more and more evident that the “‘ fallen-in ” ap- pearance of this depressed area was not mere appearance. Evidence presented itself on all sides to prove that this great area had actually sunk in one mass severa] hnndred feet. After atime the descent became much steeper, and we were mucb surprised on looking back to see be- hind us a peak rising up to a considerable height. The truth was, that it was only a ridge the same height as the main part of the amphitheater, and only presented the appearance of a peak from below. Near this point we were joined by Ford, one of the packers, who had concluded that he wanted to climb a peak, too, and had chosen this one, the hardest climb of the season. The lowest point of the amphitheater was the head RHODA.] GEOGRAPHY—MOUNT SNEFFELS. A81 of a cation leading out to the north. In the bottom of this was a small loke with an elevation of nearly 12,000 feet. It was rather a pleasure than otherwise when we began to ascend again. Now we were sure that we had no more gorges or sinks to cross, but that, excepting the ups and downs common to all peaks, our way lay upward. A few hundred feet above the bottom of the sink we came upon a bench on which were two small lakes, while just beyond, the steep, rugged mountain roseup. ‘The first half of the height was very steep, but neither so tire- some nor so dangerous as the last half. The first was a plain slope ex- tending from the lakes to the ridge of which the peak formed the termi- nation. After reaching this we had to follow the sharp ridge of the mountain, which for a considerable distance was notched much like a comb. The crystallization was nearly vertical, and we could not follow along the highest line of the ridge, but had to go down the spaces be- tween the teeth of the comb, then climb hand over hand up the steep bluff beyond, and so on until, within a few hundred feet of the top, the rock suddenly changed and was worn into more or less rounded slopes, all con- siderably polished, but beveled out in a curious manner, by the weather. - These slight bevels were our only foot-holds, and, as the slope was quite steep in some places, we had to climb with care; but all our labor was soon rewarded by the glorious view which presented itself to us when we reached the top. On the west and north sides the peak was precipitous, while on the east it sloped much more gradually. It was situated on the extreme north edge of the range, and fell in very steep slopes to the low valley of the Uncompahgre, to the north. On all sides but this we were surrounded by rugged peaks and impassable canons. The great fact which was instantly impressed upon our minds was the great area of the surface above timber-line. In fact, toward the east, south, and west, with the exception of a clump here and there, at great intervals, no timber was visible. Leading from the southeast side of the peak was a cafion, which, for a considerable distance down, ran nearly due east, but continually veering more and more toward the north. For several miles down, the slopes to the bed were very gentle, and presented the appearance of a deep hollow rather than that of a gorge; but it became more and more rugged toward its mouth, till finally, within a few miles of that point, it was almost impassable, till at last it joined the truly great canon of the Uncompahgre River. This latter canon and its vicinity is one of the most curious places in the district. The ridges running down to it both from the east and west sides are curiously notched and cut into strange shapes. Numerous high, » sharp pinnacles, clustering together here and there, appear like church- steeples, while in other places the weathering of bluffs has produced the appearance of niches with statuary. We noticed several large quartz veins which seemed never to have been discovered by the miners. Across this space, and far above it, we saw Uncompabgre Peak, which showed us the familiar precipice on the north side, with the terraced slope on the south. Though presenting to our eyes the same profile as when we were approaching it from the east, we bad lost much of our awe of the mountain from the fact that we had found so many that were harder to climb. We could see distinctly every station we had been on, so far, this summer, besides many of the year previous. The group of quartzite peaks stood up as boldly as ever about thirty miles to the south- east. In fact, I may state here that we have never yet seen the group from any station (and we have viewed it from all sides) without feeling both deep respect and awe for their terrible ruggedness. | The fact al- ready stated, that the storm-clouds seem to hover about them before 31 H 482 GEOLOGICAL SURVEY OF THE TERRITORIES. starting on their meandering ways, only served to add to our other feel- ings one of uneasiness. It may be that the vivid recollection of along and dreary storm encountered in that region, made it appear to us in an exaggerated form. A little nearer, and slightly to the left of them, we could plainly see and distinguish all the peaks surrounding Baker’s Park and the great mining region. Still nearer, and seeming almost under us, was station 28, with its associates, in the little cluster of deep red-colored peaks along the water-shed, between Mineral Creek and the Uncompahgre. The view directly south of us presented the greatest mass of peaks to be seen in any direction. In that direction we look longitudinally along the range of peaks which forms the west line of the great mountain-mass, from which there is a very abrupt descent to the western plateau system. Chief among these stood station 30, which we had visited only a few days before, while about nine miles to the west of it was the high peak which we were soon to climb, but whose top was veiled in clouds, only the massive base and a few of the subordi- nate peaks being visible. West of it were several low, sharp peaks scattered here and there, but these soon sloped off into the plain, which extended to the horizon, broken only by the deep cations which have been cut in the red sandstone by the streams. Directly to the west, in the far distance, was the group of the Sierra La Sal Mountains, and scattered about the horizon, south of them, we could see several very distant mountains, which were so far away that their blue color could scarcely be distinguished from that. of the sky. Immediately to the north of us, and far below us, was the valley of the Uncompahgre, which, on both sides, seemed to have quite a gradual slope toward the stream. To us, viewing it from this great elevation, it presented the appearance of being covered with a rich growth of grass, though of this fact we could not be sure from so great a distance. The junction of the Uncom- pahgre with the Gunnison was distinctly marked by the vegetation along the banks of the two streams. We could see the course some distance below the junction, but it soon faded into the distance, and no one could say, from what he saw, what way the water had gone. Beyond the Gunnison, on the north, there appeared a very elevated plateau, which, com mencing near the mountain-peaks, presented a nearly horizontal profile for a considerable distance, and then, slowly increasing, its slope fell off almost insensibly to the west. Still farther around to the right, and about northeast of us, we could see most of the great peaks west of the Arkansas River. Many others appeared behind, but we did not trouble our minds about recognizing them, as all our time was neces- sary for the more immediate details of the topography around us. The great length of time required to ascend and descend again prevented us irom remaining long. We had reached the top about noon, and found that we could not possibly remain over two hours and expect to get to camp; and since there was not a stick of timber on the way we dared not sleep out, even though the work on the peak had to be cut short. Our time being up, we raised a monument of loose stones about five feet high and started for camp. The descent to the lakes was very easy and did not require se time, but, as we expected, the climb up to the pass again began to tell on us, and a weakness in our legs showed what a terrible strain on our systems the morning’s climb had been. We finallyreached the pass just in time to see the sun setting. Some may suppose that now we sat down and rested ourselves before making the last descent downtocamp. Butall frequenters of the high mountains are acquainted with the fact that there, darkness follows sunset very suddenly, with scarcely any twilight between. By calling to mind this fact and estimating the obstacles RHODA.] GEOGRAPHY—MOUNTAIN CLIMBING. 483 between us and camp, we found that with our utmost endeavors we could not hope to get into camp till long after dark. On the other hand, we knew that we could not travel any considerable distance over the débris after dark, so we struck for the timber with all our speed. When darkness came on we found ourselves in a mixture of vegetation and loose rock, aud had to pick our way with the utmost care. Our long- continued exertions were at last crowned with success, and we had the pleasure of sitting down to a supper which tasted to us far better than the most costly meals of civilization, served up in the most expen- sive hotels. We reached camp at eight o’clock in the evening, having been fourteen hours from camp, twelve of which had been occupied in steady climbing, and two in work on the summit of the peak. During those twelve hours we had climbed up 7,000 feet, and down an equal dis- tance, beside traveling a horizontal distance of six miles, the whole over loose rock. The next day, which was September 11, we retraced our steps down the creek, and turning to the right followed up the west branch of the same stream. We made station 34, whose elevation is 12,997 feet, on a peak at the head of this creek. Itis the most western of the great group of mountains of which Mount Sneffels is the highest point. From here Lizard’s Head, east of Mount Wilson, stood up like a high monument on the top of a mountain-peak. From this view the width of the base bears about the same relation to the height as in the great artificial monu- ments. The height of the column is 290 feet, and the elevation of the Summit above the sea 13,160 feet. From this point it is fourteen miles distant in a straight line, yet it loomed up finely. On our way to camp, which we found located at the junction of the two creeks, we saw a black bear, the first we had yet come across, but he disappeared so suddenly that it was impossible to get a shot. We were well satisfied with having finished this part of the mountain country. Only one peak of which we had any dread remained yet to be ascended, and that was Mount Wilson. From various cireum- stauces we had reason to believe that this was higher than any station we had yet made, and from its rugged appearance we dreaded its ascent not a little. We returned to Lake San Miguel by the same trail we had come. On our way we saw a few cranes, which, with their long Jegs and unearthly noises, only served. to add to the funereal aspect of the scenery. At the lake Dr. Endlich and I stopped to make a de- tailed sketch of station 50. From here the peak, with the lake in the: foreground, and the rich groups of pine and aspen, separated by spaces covered with a rank growth of grass for a middle distance, presented a beautiful appearance. Crossing over the divide between the San Mig- uel and Dolores, at an elevation of about 10,200 feet, we turned off to the right and camped on a stream which flows down from the southeast side of Mount Wilson. On the way Mr. Wilson succeeded in killing a fair-sized male grizzly with his Springfield needle-gun. September 13 was devoted to climbing the great mountain. Riding to the timber-line, we sent our mules back to camp by one of the pack- ers, and commenced the ascent. At first we had a low bluff of slate to get over. The plates of the stone were remarkable for their great size and freedom from cracks. Above this the climb was quite easy for a considerable distance, being nothing more than plain slopes of loose débris. When we had reached an elevation of about 13,000 feet, we uoticed three mountain-sheep on the top of a high ridge to the north of us, and about 1,000 feet above us. We could scarcely see how they got up there, such was the ruggedness of the ridge. They watched our 484. GEOLOGICAL SURVEY OF THE TERRITORIES. progress from this elevated stand-point with great interest, now and then jumping upon a rock to get a better view. They reminded us very much of some of the illustrations in the school geographies. A little farther on we came to a large steep snow-bank, up which we climbed with difficulty, cutting notches in the snow for foot-holds. At the upper end of this we came to what was much worse, very steep and dangerous rock-walls. From this point to the summit the stone is crystallized into vertical blocks, broken up so as to be very insecure. Near the beginning of this part we came to a notch in the narrow ridge which was filled in by a great stone, with its upper part wedge- shaped. On the east was a fall, very nearly vertical, of two or three hundred feet, terminating below in the steep snow-bank already mentioned. On the west was a precipice many hundreds of feet in height. Over this wedge we had to pass by straddling it and sliding ourselves carefully across. The whole distance was not more than ten or fifteen feet. It seemed very much like crawling along the comb of the roof of a very high house. Just beyond arose a steep rock-wall of loose shelving rock, up which we climbed with great difficulty, from the fact that all the rocks were loose; and even the largest could not be surely depended on. Reaching the summit of this we had to walk for forty or fifty yards along the sharp ridge over loose blocks of stone standing on their ends. The ridge was so sharp that we had to follow the center. On either side the slopes were so nearly vertical that if a person should once slip there would be nothing to stop his descent for many hundred feet, and in some places a thousand feet or more. All the stones were so loose that we could feel them move under our feet. For a part of the distanee we bad to walk straight, without anything to lay our hands on. At one point in particular, we had to leap across a break in the ridge where a stone had fallen out, trusting to Providence for the firmness of the new foot-hold. This was at an elevation of nearly 14,200 feet. We came very near giving up here; but we could just get a glimpse of the main peak a little farther on, and the tempta- tion was too strong for us. After getting over this very dangerous part, we came to a deep crevasse which cut across the ridge, and succeeded, with great difficulty, in getting down to the bottom of it. A thin coating of ice over many of the stones, remaining from a recent hail- storm, added greatly to the danger of the climb. Thence we had to climb around the edge of a bluff, which we found a very dangerous un- dertaking. Once over this we climbed out of the crevasse without difficulty and gained the longed-for summit. We found it composed ot the same rock as I have described, crystallized in vertical prisms, but crumbling away. Beyond a space probably eight or ten feet square, we could not pass without the very greatest danger of being precipitated over the terrible bluffs surrounding us on nearly all sides. We could searcely find space enough for a monument, with room enough to pass around it. We did, however, leave a small monument of loose stones to mark this station, (station 35.) The thermometer stood at 33° Fahren- heit, which, with a steady breeze from the west, did not add to our com- fort, especially as we had to confine our movements to such «a small area. While we were up here clouds began to come from the northeast directly toward us and against the wind, apparently moved by an under- current, as they were below us. We could trace distinctly the track of the slight snow which fell the last night, by its marks on the peaks of the great mass. This peak was a spleudid point for a station, giving the key to the drainage and topography for miles around. To the east and north the San Miguel and its tributaries appeared to us, from our RHODA.] GEOGRAPHY—EXPLORATION OF CANONS. A485 elevated stand-point, as if laid down on a map. -Lizard’s Head, a few miles east of us, formed a very prominent feature in the landscape, although, looking at it from our elevation, (14,280 feet,) its height did not show. From this direction it appears quite broad, from the fact that its greatest length is from north to south. To the west of us and quite hear was a pretty high mountain. Beyond it were scattered a number of sharp, isolated peaks, mostly under 13,000 feet in elevation, while still farther to the west extensive plateaus reached to the horizon. In the far southwest appeared several very dim, bluish mountains, probably con- siderably over a hundred miles distant. Somewhat nearer to us, and a little farther around toward the south, appeared Ute Peak, near the southwest corner of Colorado. .In the far northwest the Sierra La Sal Mountains were distinetly visible. Much was also seen that has been already described as having been seen from other stations. Mount Wil- son is the highest mountain in Southwestern Colorado, and by far the most massive. The descent was made with great care, and, luckily, without accident either to ourselves or the instruments. The descent over the snow-bank was much easier than the ascent, being accomplished by simply sitting down on the snow and letting gravity do the rest. Below it, we found several holes among the loose rocks, which bears had pawed out for beds, but we met none of the animals themselves. We reached camp quite early. The total height climbed on foot was 2,500 feet. It was not very tiresome, but by far the most dangerous of all the climbs of the summer. After this we marched a short distance down the Dolores and made stations 56 and 37. After that, returning by way of San Miguel Lake, we recrossed the Bear Creek Pass, and camped at the creek junction, where we had camped a week previous. The day after, we rode to Howardville. We had scarcely got our dinner, when Mr. Jackson and party came up from their trip to the ruins, of which they gave glowing accounts. On September 19 we started down the Animas, crossing, over the southeast slope of Sultan Mountain, by the trail. We found the trail very bad. At one point a tree-stump stood in it. Some miners passing over this route a few days before had one of their animals killed by its falling down the side of the mountain at this point. The divide is about 10,460 feet in elevation, but the highest point of the trail is several hundred feet higher. We camped near this latter point, and the next day left the train to follow the trail a few miles and camp, while we rode in a southeasterly direction and made station 38, on a rounded peak of quartzite, 13,046 feet in elevation. From here we obtained the most striking view of the quartzite mountains. The illus- tration is reproduced from a topographical sketch made at this station. The point is on the brink of the great Animas Canon, which here is over 4,000 feet in depth; a few miles farther down it is still deeper. The total length of the Grand Cafion, from the mouth of Minerai Creek down to that of Cascade, is about seventeen miles; below this, for about seven miles, it becomes very narrow and straight, with a depth of about 1,000 feet. In returning to the trail we found the country terribly cut up along the head branches of Lime Creek, and even after reaching the trail it was not the easiest we had yet had. Judging from what I have heard and seen of the pass to the west of Sultan Mountain, I think it a much better route. Some fallen timber and swamp are encountered, but not more than on this trail. We did not travel over it ourselves; but Mr. Jackson, who has been over both, gives the trail over the western pass the preference. If ever a wagon-road can be built over into A86 GEOLOGICAL SURVEY OF THE TERRITORIES. Baker’s Park, from the south, it will be only by that way. The ground is very rough along the trail to a mile or so south of the crossing of Cascade Creek, when it becomes more even, and the traveling from there on is very good. Wagons could be brought this far, from the south, without the least trouble. A long line of sandstone bluffs ex- tends parallel to the trail for several miles, and rise from 1,500 to 1,800 feet above it. The trail passes along a sort of table, with these bluffs rising above it on the west side, and the Animas Cafion bounding it on the east. Arriving at Animas City, we stabled our riding-mules in a deserted dwelling-house, and, hanging up our instruments in another, across the street from the first, made a thorough exploration of the city. We found it located on a beautiful level patch of ground, with scattering yellow pines growing all over it. It was composed of one street, with a row of log cabins on either side stretching a distance of several hundred yards. Some of the houses were nearly finished, some half done, and the sites of others were marked by two or three tiers of logs laid one above the other. All were deserted. We took possession oi the best-looking one, which had a kitchen attached, and made our- selves very comfortable; eating inside and sleeping out of doors. The night was so bright and clear that we could not endure sleeping under a roof. We found several persons living in the vicinity, and from them we learned that the settlers had been time and again ordered away by the Indians, and had finally considered it best to leave. The height of this place is 6,850 feet. From Baker’s Park to this point, a distance of about twenty-six miles, the Animas has a fall of 2,550 feet, or an average of 100 feet to the mile. Trout are found in the river here, but how abun- dantly Lcannot say. They have never been caught as far up as Baker’s Park—due, probably, to the falls between the two points. Traveling down stream, the stream-bed soon widens into a very pretty valley, bearing the name of Animas Park. It extends from a point pear Animas City, so called, down the river about fourteen miles, with a maximum width of two miles. The total area may be estimated at twenty square miles, but the part capable of cultivation does not amount to more than three or four thousand acres. The greater por- tion of this can be irrigated at little expense. In passing through it we saw corn, wheat, potatoes, turnips, and watermelons growing finely, but all abandoned on account of Indian troubles. This valley is very interesting in many respects. First it contains almost the only tillable land within a hundred miles of the mines. Its distance from Baker’s Park is only thirty-five miles by the trail. It is probably the richest © little valley in the Territory, and has an elevation of only 6,700 to 6,500 feet. 1t faces the south, and consequently is very warm, while at the same time it is near enough to the mountains to get the benefit of their great rain-fall. Near its lower end good coal is found in the greatest abundance, while a plentiful supply of good pine timber is near at hand. Farther down the river the country becomes a plain, almost perfectly barren of vegetation. After passing through the park, we made sev- eral stations, west of the river, on low hills. On station 45, which is not represented on the accompanying map, but situated just a little below the border, we found some old ruins, consisting of a couple of watch- - towers; one entirely disintegrated, leaving only a hole in the ground to indicate its presence, while the other still remained about four feet high, but was completely overgrown by oak-bushes. Some white and painted pottery lay about. This point is a wooded hill, east of the Rio La Plata. The day after, we found some pottery still farther north, on station 46, which is on the map. After this we followed a road which had been used by the former settlers, over to the Florida, and made RHODA] GEOGRAPHY—ANTELOPE PARK. A487 several stations near that stream. The road soon ended, and we fol- lowed its continuation, an Indian trail, to the Pinos River. This trail, by an oversight, is not represented on the map. Itleavesthe Animas about half a mile north of station 46, and thence crosses over to the Florida, which it follows up for several miles, then strikes across to the Pinos, and crosses that stream at the mouth of the Vallecito; crossing thence over the next ridge, it strikes the Ute trail from Los Pinos agency. It is not much used, and is cons: quently quite difficult to follow. There is some fine bottom-land on the Florida, capable of a high degree of cul- tivation, but of small extent. Near the junction of the Vallecito and Los Pinos is another small area of splendid land. These two streams running down from the quartzite peaks, carry atleast one-half more water than any other streams of the same drainage area in the district. The next day after passing this point, October 2, snow began to fall, and, camping near a peak on which we had to make a station, we qui- etly waited for the weather to clear off. By a remarkable accident we had halted in a splendid camping-place, there being none worthy the name for miles ahead of us, as we afterward found. Snow fell continu. - ously for four days, and we found sitting in camp very hard work. On account of our peculiarly protected position the snow that fell near our camp melted as it fell, but a mile up stream it lay two feet deep. Had it not been for the good grass and shelter here offered, our worn-out mules would have fared badly. A thing worthy of note is the fact that very slight thunder and lightning continued through the whole of this snow-storm. Lieutenant Wheeler narrates a similar experience in this part of the country. On the fourth day the weather cleared off, and we succeeded in making our station, though on the summit the snow was two or three feet deep, which, with our shoes nearly worn ovt, was very disagreeable. Returning early from the peak we moved up the ridge. The trail being entirely hidden by the snow, we had to give it up, and after a very difficult day’s march we succeeded in getting out of the snow only, and then had to camp in swampy ground, making our beds on pine boughs, which we cut from the trees. We knew now that winter had commenced, and we wanted to get out of the mount- ains as fast as our mules could carry us. The next day we crossed the divide at the head of Los Pinos River, by way of the Ute trail. The pass by this route was good, though covered with snow. In the summer it must be very easy and pleasant. We felt thankful when quite late in the afternoon we reached the Rio Grande and struck camp near the wagon- road. The next day we traveled down the road, which here is a very good one, to Antelope Park, which we found to be quite an extensive piece of plain country, forming here the valley of the Rio Grande, and continued below, by a narrow strip of Jow land, along the river. The elevation of the park is about 9,000 feet. There are several houses dotted about over it and farms laid out, although the elevation is too great to allow much grain to be produced. The next day, Oc- tober 9, we ascended Bristol Head and made station 54. This is < very curious bald mountain, a few miles east of Antelope Park, being the southern culminating point of a high platean. To the east it slopes down quite gently, but on the west side it falls abruptly nearly 4,000 feet to the bottom of a very curious sink. In some places the bluff is quite vertical for over a thousand feet. Being composed of trachyte, the rock breaks off along vertical planes and gives to the precipice the character peculiar to volcanic formations. The sink already mentioned is a little valley from a quarter to half a mile broad, bordered on the east by the high bluffs of Bristol Head; and, on the west, by a ridge 488 GEOLOGICAL SURVEY OF THE TERRITORIES. and bluffs reaching seven to eight hundred feet above the valley. At the lower end a narrow gate-way leads out to the Rio Grande; and, at the upper end, a beautiful lake occupies the highest part. Just above this, Clear Creek cuts through the ridge on the west side, and flows out through Antelope Park. The whole mass of this basin has, undoubt- edly, tallen in; and, at one time, Antelope Park must have jutted up against the side of the mountain. We made the ascent of the peak from the sink, riding our mules the whole distance, except the first part of the climb, from the sink up to the ridge. On the summit we found the snow about a foot and a half deep. A large bear had left his tracks all over it. We found the slope to the east quite gradual and made the descent on that side instead of going down the way we came up. After camping at a point on the road to the south of Bristol Head, we moved down the Rio Grande. The only place of special interest on the way was Wagon-Wheel Gap, where the river passes for a few hundred yards between two high bluffs, about 300 feet apart. This point has evidently been, in times past, a great battle-ground between the Utes and their enemies of the plains, the Cheyennes, Arapahoes, &c. Many little heaps of rocks on the south bluff seem to have done service as rifle-pits. The toll-gate for the San Juan road is situated near this place. We arrived at Del Norte on October 10. The town contains several hundred inhabitants, and at the present time does a considerable busi- ness with the San Juan mines. Leaving Del Norte we traveled across San Luis Valley; far behind us we could see a new but apparently greater storm than we had yet passed through gathering around the distant mountains. Crossing over Mosca Pass and down Huerfano Park we reached Pueblo October 18. The next morning we took the cars on the narrow-gauge railway, and in the evening arrived at Den- ver, our point of beginning. METHODS USED IN DETERMINING THE ELEVATION OF POINTS IN THE DISTRICT. All the elevations given in this report depend upon readings of a mercurial barometer. Where a standard barometer, whose elevation is well determined, is within a short distance, this instrument gives a very good determination of elevation. In the past summer, however, it was quite impossible to establish a base barometer in the vicinity of the region surveyed, witbout great expense. All the readings had to be referred to distant stations. Readings on high peaks were referred to the Signal-Service barometer on Pike’s Peak, at an elevation of 14,147 feet above the sea, while readings on all points under 12,000 feet were referred to the barometer of the United States Geological Survey at Fairplay, whose elevation is 9,964.5 feet. The first of these is one hun- dred and fifty miles distant in a straight line from the central part of the San Juan country, while the second is one hundred and twenty-five miles distant. These distances are too great to give accurate results with the barometer. At several points in the region we succeeded in getting two readings at the same point at intervals of several days, but finding that the resulting heights, as calculated by reference to those distant bases, did not agree well enough, it was resolved to collect together ali the data possivle from the field-notes, and see if a fair trigonometric connection between the mountain-peaks could not be established. The result was, under the circumstances, highly satisfactory. It must be remembered, RHODA] METHODS FOR DETERMINING ELEVATIONS. A489 however, that these observations were not taken with the object in view of making such a system of trigonometric levels. Moreover, the instru- ment used read only to minutes of are. Supposing an error of a min- ute in a reading, which is not at all uncommon, the resulting error in the difference of level of two peaks from a single observation will be 15.3 feet for a distance of ten miles and 23 feet for a distance of fifteen miles. If, as is sometimes the case, the error be more than one minute, the error in the elevation will be still greater. Another large and uncertain element in the problem is refraction, which in the high mount- ains is so changeable as to add much to the uncertainty of the results. In many cases the observations were taken during storms, and often the peaks were sighted through breaks in the clouds, making the refrac- tion still more uncertain. From each station angles of elevation or depression were taken to the Surrounding peaks and especially to previous stations. Had the fore sights and back sights between the several stations been simultaneous the error of the refraction correction would have been Very nearly neutralized, but these two sets of observations were never taken at the same time, and in only one case on the same day. From each of two stations I always succeeded in finding some. peaks which had been sighted from both. With this material on hand the distances were obtained from Mr. Wilson’s plot of his secondary triangulation, which will not probably involve, in any case used, a greater error than five-hundredths of a mile, which in- cludes the error due to shrinkage of paper, as these distances were all hastily taken off from the map with ascale. Having then the horizontal distance between the two stations and the angle of elevation or depres- sion from one to the other, of course the difference of Jevel can be deter- mined. Bat, on account of the errors which have crept into these angles from the causes above mentioned, one determination of the differ- ence of level is not sufficient. The back sight is then calculated, and brings a different result. For a still finer approximation, wherever ver- tical angles had been taken from the two stations to the same point, the height of that above and below each station was calculated. From this, another determination of the difference in the height of the two stations was determined. Then the height of another unvisited point was calculated, and so on for all the near points sighted from both sta- tions. Each point gives one determination of the difference of the two stations. In some cases it will be found that one result is far out from the rest. This may be due to the fact that sights to different points, which have received, by mistake, the same number in the notes, have been used. Such cases are thrown out, dud a mean of the rest assumed as the true difference of level. It was found that, on account of errors of refraction and imperfections of the instrument, sights over fifteen miles in length could not be depended on at all. In the following caleu- lations no sights of that length were used, and in tact very few over ten miles have been used. In making the calculation, the following formula was used, taken from Lee’s tables : dh = 0.00000485 K A + 0.000000667 K? In which dhis the difference of level of the two points, K the horizontal distance in yards, and A the number of seconds in the vertical angle used. In this formula are contained corrections for both curvature and refraction, the latter element being assumed equal to 0.078 of the curv- ature. Om examining the notes carefully it was found that there were sights to many hundreds of different peaks, and it became a difficult prob- lem to utilize allthis material, and at the same time do it according to a sys- 490 GEOLOGICAL SURVEY OF THE TERRITORIES. tem. After anumber of experiments on different methods it was found ‘that to bring order out of this chaos, it was necessary to take up each link in the chain separately, and use all the data that could be found | pertaining to it, and determine the difference of level of these two sta- tions finally. Next, the same process had to be gone through with the line from the second point to the next station beyond, and so on. In doing this it was found that some of these lines were much better deter- mined than the others. In finally reducing these differences of level to a common datum point, this fact might multiply the errors in the work. For instance, a number of well-determined differences of level might be transferred through a poorly-determined line, thus vitiating all with the error of the one. In order to obviate this the following scheme was adopted: A central chain of well-determined lines was car- ried through the heart of the mountain-mass from Mount Wilson, the most westerly of the high peaks, to station 8, five miles east of Uncompah- gre Peak, in the northeast corner of the mass. From this main line sev- eral secondary branches were carried wherever the short lines could be well determined. This system covered the whole mass of mountains. Other stations, which could not be well enongh determined independ- ently, were connected with different points in the main lines. In the central line we have the following parts: From Mount Wilson to sta- tion 30, a peak east of it and distant 9.3 miles, is a fall of 383 feet, which is the mean of five determinations having a range of 32 feet; thence east to Sultan Mountain, a distance of 6.88 miles, with a fall of 536 feet, the mean of six determinations, range 23 feet; thence northeast to sta- tion 16, distant 6.60 miles, a rise of 175 feet, the mean of nine determi- nations, range 35 feet; thence northeast to Handie’s Peak, 7.51 miles, a rise ot 456 feet, the mean of eight determinations, range 54 feet; thence north to Uncompahgre Peak, distant 11.14 miles, a rise of 238 feet, the mean of nine determinations, range 49 feet; thence east to station 8, distant 4.92 miles, a fall of 1,380 feet, the mean of ten determinations, range 67 feet. This campletes the central or trunk line, whose length is 46.35 miles. From Sultan Mountain a branch was extended eastward ; from this peak to station 25, distant 10.28 miles, a rise of 209 feet, the mean of twelve determinations, range 67; thence to Rio Grande Pyra- mid, distant 8.63 miles, a rise of 197 feet, the mean of nineteen determi- nations, range 95. From station 25, a branch extends to Mount Oso, distant 7.29 miles, a rise of 64 feet, the mean of seven determinations, range 37. From station 30 a secondary branch was extended south and west. Station 30 to Engineer Mountain, distant 6.98 miles, a fall of 926 feet, the mean of eight determinations, range 22; thence west to station 36, distant 6.76 miles, a fall of 417 feet, the mean of eleven determinations, range 51; thence to station 37, distant 3.65 miles, a rise of 94 feet, the mean of five determinations, range 35. Another important sub-line extends from Sultan Mountain to the northwest. The first link in the chain is the line from this point to station 28. The heights of stations 30 and 16, above Sultan Mountain, having been already well determined from the central chain, I made use of all the connections between station 28 and each of these points, re- ducing all of them to a common point. The result from this was the following: Sultan Mountain to station 28, distant 7.86 miles, a fall of 484 feet, the mean of eighteen determinations, range 76 feet; thence to Station 29, distant 3.77 miles, a rise of 324 feet, the mean of eight de- terminations, range 43 feet; thence to Mount Sneffels, distant 5.94 niles, a rise of 952 feet, the mean of six determinations, range 36 feet; RHODA.] METHODS FOR DETERMINING ELEVATIONS. 491 thence to station 34, distant 6.65 miles, a fall of 1,161 feet, the mean of five deter minations, range 23 feet. This completes all the en: determined chains. Other stations on which barometric readings had been taken, were connected with as many points in the main lines as possible, and these being reduced to a common point a mean was taken. Such points are the following: Sultan Mountain to station 10, a fall of 223 feet, the mean of eleven determinations, range 76 feet; Uncompahgre Peak to station 5, a fall of 1,498 feet, the mean of ten determinations, range 85 feet. Uncompah- gre Peak to station 11, a fall of 3,624 feet, the mean of eight deter- minations, range 111 feet; Sultan Mountain to station 51, a fall of 835 feet, the mean ‘of three deter minations, range 75 feet; Sultan Mountain to station 48, a fall of 1,061 feet, the mean of six determinations, range 59 feet; Handie’s Peak to station 13, a fall of 1,175 feet, mean of fore and back sights, range 6 feet. Besides these there are two which depend on single determinations: First, from Sultan Mountain to the point in Baker’s Park where the road crosses Cement Creek in Silverton, distant bee miles, a fall of 3,961 feet. Second, from Mount Sneffels to station 52, which is obtained from sights to a common point between them, distant from Mount Sneffeis 2.04 miles, and from station 32 3.75 miles, the fall is 5,650 feet. This difference of level is checked by sights to distant points to the south of station 32. These two cases are admitted, because the distances were so short as to preclude the possibility of any considerable error. From all these results a table was made out, showing the heights of each, station above or below a commen datum-point. Sultan Mountain was selected as the datum point, from its central location, and also from the fact that it was sitnated on the great central chat of levels at its janction with the two principal sub- lines. A second column was added, giving the height of each Sr ation as deter- mined by the single barometric reading taken thereon. 466 BIG AO MS Abs See e se MSO CA ASS oicobSonnseone obEnonaHod booaKo ooo se 429, 492, 494, 495, 496 of junctions of streams joo. 00... ons se se oe acl eee 433 TMOUMULAIMSE hese ccisincwisiceainas ceislelsiceteeeee eee ee eee eee 441 parks) valleys; de “cc cos cite Oat es Ste ee RG ae ea 442 passesyandi divides <2 occ sacs tee eee eee eee eee 443 on Whiter River plateau eeen sooo ae ee eee eee eee eee £42 Tevision, Of, ink Mountaineers a. )ise oe else oe eo ae eee 436 Sawatch range. sys eee ee ee 429 Hk Mountain Tansey oe esses So es oa PI 54, 64 CEO RY OF Bee ee eS a 54, 58 northwestern portion 2. ses-e nee eee 59 MO UIN Gants oo ee eee ee eee ee eee eee ee eee ely ain te a ae _.92, 100, 416 eleviatlonsiofes face ol See o as oy b le ek Sens ee 430 revision Of elevations ain s2 3) so ay eee ee ee eee eh aia ee 430 TB yay OUbie) oe HAIG sit yeiN\ fan DL Yond estoy cel iag Maes abe cas Ae gan AAT pe MNase we 103, 114, 1240 139152 letter to Dr. Haydenees sce: segs a 183 TOPOL OL ia, slelenaise ne ea eee ere eae nee 181 Mmgimeer Mo wma eyo) se aes eee A A ee LL ee ies eee 207, 217 EGLOSLOM teem sieialatsloin(aleioiciniie sinjeeiaictaiciot ote UNE OS RB CESS UL es Sy 44,124 shay TEAM Voqeb any b otter serene a ERE Sei aes ach ca eet pacts en reemn ne 57 SEGA AS) ys 0s AEE SAS AE Re RM NU Nk Le Ade PA EE geet) Ya WE oT TA 60, 70, 97, 105 BECULOTIS Oferees senate Aa ee ee choca ne eam al Sie ele Ons pats eae 61, 125, 226, 127 502 INDEX. K. . Page. ealnmalny Cree ee orci ae Ne af tale ery eee een 105 Kone @larence; Map TeLerBed: TOM = 42 .sece sea Batra aa ates siatai Slates icine Si sla loleroierat otatare ciegeteunisioeie mie eee 25 FAVeGHOPUCLIS iso. saccses sossee coisa Scop bebososace fo arene eh ere ate Breeton sisyaetenrs 280 AMlimGesp unl equilaterallis's ssc atenactessteisie: ei nse wlerelnwicielie Selene cieiaia sievelnite selelatnereis 307 PITTS UNE LOLSHCINI Assos a hors talc) enim se wisi ee cla swale dlalbineaiarns acetone tener 293 PANTO MUAGE LON S eae see Sepeersiol Sah ese ot siaicersmimteyaivcieiarsy eisraormarerel esis tate a/ eharalcie ay steerage 339 PAEMNIMIOUMUDES hate eista cet steio ats sey wislelciviedar sais ata eicisral nv avaraveveryeny ctoenaereieleiens ores ners eas 29, 35, 56 lO babu sense eee ss asst so ccs so se db cihis Sees sacle seeceee seme ceee 30 peRricarinatusyeraas aes xa cctecatl- ce hoe see seeleurlee eel aeeoates 129, 134 FATMTIT COMM 20: Fo amas ae tevae ais Sale Me ioie Smale e sine dele cine, a/ejeie ony sfeie s,cieia cleelalareieterne 390 THOM Cre eA aten eae ciate ral visa a tay © s(claicfar nic slotinys sim olay aia eicteiellolviaj= srove tiers Sialeieyenetateds 302 ASTRA GO Oa NN jos soob eb se boo be aoe SO CEO OO Ubeenned osteo Cone Sapear Geese 304 AULEUMA OUND ters cisteralafs) mice sisra.cicia aise sucicieis) © tnssais steers Sites ees 354 OVATE: eee SR oSrcreiet wise ieid jeu ereier Stare alee ma Sree rei ae i na 3500 AMCHIGHeLIUM temo see we sees asso Se PEAT el ee a Raat sc TR ose 23, 25 PANTY EC YIU IT CON Ae ere ys Set aie cc cic ters ot emcee paeleyele Msc ae SU SU aes 405 ANGVINS Paral Clusia. as sese sie oo artic ae he cas eelse eck osjeve vine Siceis le alae SN 405 AHOTONICH Ap AlN 1S a ora aelovers.c stale Saks atcha e Sreys eleions cretcinie Glstal sais eters ee yet Met eee 348 AE] AOL RS es a3 5 to) Sth e tabciaeleisicy Saree eloraityare Saree sine c.ciev aie cal iecters 348 Amisophiyllumsenn-alatum sacs. essoclsee esses ccc cemtece Sains etisecie acces 363 ATIMULALIA= Jos5 S256 BeBe Ser ayo aieis Seka hake Vee dS ieee clea a enone semi ewis elemesaiaeire 276 ANTONE) 2 SES SEES SOS SSS Se OSE eee ea een Eee en Sars Senden aM I Ea 34 NGUILOIMACE BYE a ena se cre Sea eee ye sae coe e wc iscsi cemieoe sie cece mae ese oueleaetes 309 ANTE IG ef E e ear eee eR eRe ee pn Ray Laat EAR AHLACLS Sis a oie eta Urey ee hie ug Neel eg 138 CONCES basa soos Haseena ere See tate ae iar ie Sittin: sreim ah eeleie tie ea Ieee oat 349 CENA OWE) OREN) Gabe Goo0 obda Boob oeaee> UbEBeOdeoacd soubioeHoSo EOS oGods 349 SApPOLbaneaine a sese ai ders seek eos, Aaereiels seis clears eeia ear e eis Stone te iar aree ee 350 MO WNOL oe oye ates aioe om cee apse eieicieis eiete le mie leisistutcen sie eroreiste nie ene aroha eters 349 LEIparhiiays spss set eae SS Sociale ser ek ce terete iceman le siemens ese ere ease 348 PAT CHEOPLETIGiaet se iae as osie oeicle aise Sais nie inci Saree reee a secicte eens oesiniered Eee PNES EI erates 278 Aristolochibesia@entatarsscs sa scr suis stein cries oie. ninjas sae cins saceels neeee moe eee 347 Arterophyllites gracilis ..---.--.. WEE reise oloieieelsig cas enemas meee noes aise 279 AT MOU ACHY Obes sel oases cieistey ciniays Sidhe satiate aS aerelain acioyeis wee eis Nmap esienine cane were 37, 15 ATM GOOD LUSAte saa seicicet a oan cae ceo Aa Sarg wie Gi Sey a cle ahah a/aretalte Semele ney CL 311 TOPOL Lares cso Sale sate alate) Se mnciaie: aren evere ne caiah a oi eea eter ae RUM ea eke TMA AH ae 311 ASEROOIE) Chess DOGO BOSE E SECO ES SOE EC ENE ge tes Blinn oO sla ayn a 112 JE (ETE IIVEES) “Ee ese eee Ease eR aeIET ee P en TE DUIS Unt eA Sea eRe SA HT ener yeeiey EOL ale 347 Mspidiophyllumr trilopatmi eset acta satalseatacicicletenicoliseioy ieee eee mete eects 361 LUIS ABS) ao 614 OCDE BASES SB eee enn N pia trance 6 SLR iey peat ne tino 213 Sub Lili Gayasseoies a ctetovas era ce sleyaianb alata isin tes Sratel asin oraen eae ste le re Grete ei ere eS 216 ASIGUILD) Sete BUS eS EC ep ROE E ROBO ORE Ee Ee aera e pear aie et tuabe mien Bes as 115 hin ou at OLMIS Sse ose jars aire cto ae wets ovsiemic see eicienta ooo atioeioaiereieetecerereeris 137 RSCTA ECC UCIIM Ose ata aN aot SN ciaPclate ssc} ote s Sara ee yee epee Pee mee re 115 IEC HUVEC Ree eo a be rere lala Wet eras ae i bie ca eto Ni Raat ye daa 2 cae 29, 35, 56 OVALUS Ossie e meses sale = ar 55 7s Sseta sielde cre msimielcle nat ances wmenneres 30 AR CVOllIa 2 SaaS SUR uae Ae ee the Sal gece nota cee eke nn ae 115 BSG ERY LEU Sis S722 Sen etaacle eel a lS) sta eyak erent Nase Oia ANG a ic loys nyayete ante le rel wae ee 112 NSC UET SHOTS pase oes tars oop ve ra wince coe onlay io hStar aia ciate isles mars me ne eee 213 ELL UCALLICI AN Aa sate sSeicccie feo So clncchae as eas eea ome MOIS eon cine Sane 339 Word esiitos 3525 2285 a0 ahs SR sable ters bac iascrcloaideo Sect sdonc eee eeee ae 312 EI CORMES ea Smee Sati i 5 Meas aU hh tan SAGA Ub old aye are ht ae een 348 CALA STTIGS 1 2 le eee ie an ee EE Eee ee IEE RE fem ee eR rs 42 GASSED ey ais creer Sis Rl A ea eS ere CI EAL, fae pe 118 DUCK OVI 2 sacar tseces te Mea ei rc facepa cla uute de heals ee 118 510 INDEX OF SYSTEMATIC NAMES. Page. WaMIS eee eta ewe ere eae sa i ea a re eee ae 23, 25 Cardiocarpon South wellit. 2. oo) eos je cce secre eee eee eee eee he) WaxrditMySPEClOSUM s/s eiecisiece siciss elalocies eee cece eee ee eee eee cicoieae 30 Canpinusorandise. Jos sina ce\cceace es scene sic esi nee see ee ee eee ee chee 313 Carpiteswa burns) 22 So soee ee ese) eee ee sible 6 Gio wisiaials Clais sain ate eae ee 308 CaxpolGhes| i ccceiwacicesissemes cove suc cinecs asa Gcec cate cence cee eee nnee 279, 289, 364 Castanea jantermedias o.oo. socio toe wie etine she Salsas mecelse ce en eee ae 313 WASLOT ee ceo Mate a dad Sea Mice a aic ahd ou albeit RAV ae Q3, 25 Mhioensissansscieeseicicscists MOB Ob BBSrG Ca vlisicn sass sisies mace aoe eee eae 263 @amlimites spinosa... 5). eis ic nce msec cce scan cen cc cecmceelumerk eee ees 364 elastrophyllum, ensifolium <.. 2)... 256 oc ee cese es cone nee Seen eee eae dad WOEVUSs see eciwrce eben yas Siaeeuse ee vescr Shee kine o eee s ea re ke Oe eee 25: M@eerOPOLAMUS | oe ee ee ey ee a cis Sut Na 23: Cinnamonmium)Mississipienses 2s cco eons hs Se Ue 291 CHSSTINES Ae er Aer e El Mn cim omelet an abn SoS eee asia rerareeyee lone eect ate eres ehises 352: ACUMINALUS 5 o\ 134 ING bras kam age yee eee isis eis ere nlenie reer etote ekcialeis aialeiniaiat seater atataeye 333 ecuimibranchiatarteee aces slecee ieceiiaioe cicwletoenivia ete mersfeinicicusicieisisienisiomeeats 390 Perse ILCCOMUERINE Gacboq adda nd sdien S4oGo0n Su bEds6u Gene oN p66 SodCoE eno Gaoulee 343 SUPTEA DEEN Saco ca ceoseiqcdas 66455445 o5c6 S555 Sede ee as cee hens aang dba 343 Phaseolites juglandinus SU tee SR a UO Rg OO HU Ng I 314 IBhitolithus-. . veoxeccms eens ccesaisecsi cee ases ee ee ar eat eS AI 281 brace mibes: CLELACCOUS ese erciame eye seiaie stele icteiniela ioe ioicleicis einem ieisinetevere weue 338 TPINEE cackde desdes bannga caecHodeuang SUsenHSeaobeeSHa bese GSuaeoseors cuneebad 25 LIS REO SIRT ONE) concen andd ce Saba ckdGes sHah Goondn So pbasadboossabouseoes 400 Ip Pnysidl cone cea so ce eeycin ere ere te alco ninie etiate salle slereinie nto islo nu leleveiarels ciore eijeisicjalsamloumies ei eeere 400 IP W Les GAO HONOUIS- Gaooaso aagsce 6400 dadcd0.ge- Sood bsooss coneea goons wiles Subst 364 betuleefoliug ---2-.ss5.-- rete ee a ferciefe cera is aya eine atnene re ciaveiels apo erciereioeras 363 FIC EV Ok © DUM S oer ete yeaa ee ae ree yaa ae RTS Nea ISH PR 361 Tel AYO) cal) 1X0) CO (SWS OG ROSE GARISH CIS Se yates Expl Meda ees GF 364 TH TYN INO TDD GUNS era ae oe are te ere ee a sate eave cere HACE ACOA TIE Us A A ea 364 WEED DED SEES SE ECCS ETE Tae 1 A ECC SL 364 Phyllocladussubintecritolius) 20 ssercc tems soe slemiGae emiaicelsia eis eteisie a celenie nuance 337 AEEWIAB tas cisia te ie aici nie alata) oie wis lae a Se ete a iaiasn rata ia ain eine Lectnicle ie eieie mise meraneelan aaa 134 EMIS EO TOD SLOC tls sem areca cat tere atop eels icine wie! acl nice ate aroeaeiie ce teams ra ia en 336 TET S ETT OTN SASS SE Oe SG SC CIR ERCP CRE IIE ee ers Une MUP eC BS Ad 22 ISA COLLUS Alas aoa a, os eo elalen capa eevee te ieieleta sein haeiseaaas meine heciemminteyteate heya 287, 289 Mapelii ey es RIES TOA ane penance fe yee SC Saat EG aD MeN RIE MPU eo 8 289 Famer AgNO Oreja sate iar ercia sie a cia SS ala cies a teen a Sialaialvic Selee alslale nna eee 313 Planorbine . Fa a RN ee UN aa Ug I ee EOE ONL CUI en 2 402 LVF OS GaSe Se See AS eae rea a re ale I Tar AEA RBG dg RRL SO 23; 25 J 24S SHOT TE CETTE Se a apn Li Ly OR ee EE Erol VU gel 154 VEL IETNERD BESS GOS a aos Ea ee area lel nN eT OE POR LeU AER LBL gE 341 [EPEAT Be GaG5 Sy Ee ESN MT OOeO SS be ATMEL Ere ure UNNI eA ASS TOUT 23,13 ACCLOTG CS epee ee eae are a ne ne epee eae my ahs kale AML sine al a ie 293 ERT TUVTTN TN Br Ves etive pars is eee ee er asta cca eae ely RAN ras er Set ree Da Lg 341 Gone lines es ee ee eer ie reat Ie Se peer ees aN 293 Elia Wenieocias 2 tsaia eyo Sere/Saoe etal Sera Seip ab aael kmaeiny Ses miej aeleke acolo AES 32 HOH bbl SSeee SABES SBE Oe Oe eee Hs ic sereecr ay aves Aeon ee he kaney engl UM 341 INS SWDE LETT 1 aiprope geet mice eesti RETO aS ERE Si SL IS ol LIN de 341 ON LUST Oy asap ae en rs cea Stale eared oy cee aay a acieys | Moga ee, aca NE 341 PDDLM CO 1B lose eens Shalom ies eae a as cees eres S ere ai eve ia ci biajaie ae eis toe case a 341 lenEOpNOnUs sq areas fateayocisveys merase are e/a one sles sleiaeas osu miaieie siepeislniier ser oeeatetnteae 115 AE CEE O HE OTUs arte rates a ae essay a ey ee eh es cea ate pears ee AC AU vl ai Cae 25 FG by CAL PIC rs sere e aii eae tsa ea io soe, oe ge ee ele sete a Ute ccleaner 355. OWA LTO PST EO ie asus ieee alate el ele ager ieee eee ei a ace SV MO aS 391 Bormrpholi gine aos). aeons ayia mispeioe sisi el aivin: sone Sins wie SUS Dele crea chap a Ie 405 Poprlitestelecansieen alee cece hears sere savas Re Leta Le iM oh ere aa 38 VAN CAS ETICNISIS eee eta alc reven ree fare see STe Ae RC EEEN ide lee hoe emiee aeue aes 339 OPUS m crt cohi Sak meson vec ete Srieeat ce see Rec Sa abr te aleve 23 EIKO (GF Sa SSE BOA ASO SS OOO Be CS IE ETE ae esses ete ee EP 293 iG) BEING) cong eoseds codSotcuer cdéoccoReo de pagoua cubee seu codouSbucs 302 MelAMATIOLM ES hee ose e Somers eam rae, ete aaa i Se SU a ee 291, 302 TUG DUS ee eee eee eee eee oe re tibieile) erence 291 ELEM ML OLA ES ee Races oa aera a sya ee a ety e isto wise elope aT 81, 86, 93 SE RGB ITEO IE Micra cie = cay ere atid Cy eea sie rT ee A i aN aU 22 Prionocyclus “Wyomingensis Bette celts) Sie loregerayalebe aia re ets cate Geisinte eines nie mie te pahenete te teens 136 LESS SEIT GIS ea ee aaa el Re eS mm TNS DCE 25 EEUU oe oreo cots ta ee ae Ne eee rey es aime 8 ILE eS, ee ob 114, 119 BEMIS AGUS (sate sala oy sisiseiclei se piniseininve eine cicie cle cic eee eee eos oaieel Gyan Subacwleatusme cs tates tee ee ee eye a ae ees ape ae ae 213 DESI CEGE SERS 1 RT ae ERT eee eet a UE ang Se ee a ey Seo a Ne MENTO RUDI TEAS 346 EASE OTOL SECA GOV fas sae sata esa ee OL Nee ee el ede ae Ee a ec 128, 347 MA PHNOPENOIMES ici calecanian eee aise ea cncveciainy cists Seep 347 Grevillesformis... 28 ........--2-.-. Sig rete e pee aia ee Sr a 347 EEO) DOLLS IG V pce a aia can se Sia ree heh a OI ne SINS A pada oe paver alls 25 Piste piyllanieLvednc4riOldes. so ssc sec, 5 soa tee eeina,e aoa o caieisaicjomen aceon eee 363 PAV GOD 211 Bmadlichigeseseee eens syjdisidiarbinleioneyavai anaheim Since loraveneke/ Sy ekcNane Lea Slappa 213 ARISSOUG C20 eeteres cinicin teri meres ste fe loiiwyn ia wr ntmlnl el aiaievnjelsvaivraileialalel laste lara laret Wetctetatetatewee reper aretate 390 Sabaljamdecavensisis. cic inves ssismiataieicielas vierciescla)= slain) setersteinn ala ole datetet tare ese Reet 290 Camp Welly we se ise cote rreva Se eysiapeterwatbiateregelslcie neice Melee ome c eae 32 COMMIS 35a ions oS o jee Sie leew ye ea ae Perera ge RE LU Oe RR oli (Crib osaoeo eoeeos Soe Soo coeos cone pase Hesod Subtano subedeooesce 289, 290, 301 RAGES) VEN Boon sesso pono o Geos boSORS Koda Gado bsad ones ousedaa cece Goad 290 Shiu Bey Ole) oueiI e ood Sopeooose BeReeo Fobra oboe boa) Gases ScoKoussotoces 249 Sallax Riheamay? sci cence ccc) eetice © hielo re Kioto peietave natehsieoiet ele tee eee am 288 PLOVC DION A econ wiles ee onsale misiniwimm ciate sara iala cietateieente fajita ete aie ate eee 339 Salivinia attenuata -ieerenjnoonwiavalcters wie iocinletwwinieroilafelajn inte heiniete tele ialeeimiovote aioe remote 296 SapUn Gs) AAAS =o tate nem nine mim ferein la winnie oe ee lal= etoile eet eee et eee 289 POMBO corn paroi ke imccrcve SiSlayaim vere core hota ra ee tk le a eae ea 315 Sassatrastecescscseeeoeee Sielalaieisierisiciafelcie'tic wists et wiLic Siaiallele c/eiate eee ere re ee See ee 344 acutilobUM \c2.2o- ecccies deme sieccmcs See oee ese See ee Eee ee eee 344 (Azvaliopsis) cretaceum, .2js 2 s-nso2--2 wc eee cecesel eee ee eee ee eee eee 344 Var. dentatum2 occ pees eee ee eee 344 obtusum 22 2e-ee-see SDE Ge Se Or eee 344 MITADIUC.. a dwine da cwerqecas Sect eee eRe See ae 129, 345 TOCUPVaAbA i ~ccees ec ower See een eR ee eee isa 345 WY IOTS ee) ES SE SA sacnQgecao ctodicd osc adhH dddeed cosa osee 344 SEA Hs] pa a eos Goose seoceo on saso Gossou Gaodso sco aso esd couse Gd obdece seose- 135 WiaErenananccccd.ceconce nese webccc cee eee eee ee eee eee 136 Selacinellay? faleataeeocceeescee ee eet scar iacisinee bite heaters eee teeter 297 1aciniata ss. b.seesecece se heeetececes Dee mp eee eee ee eee 297 Sequbia acuminatac. 2.222206 2 cctise snc sicce etaelesee erect eee eerie ee = eee 310 DERMIS occ oiscic cnis wee woe oe Tea tee te eieie He RE See Tole Ce et ee eee eee 310 Ibiformiss.é dec encesckacaccese ee deomee eee eee eceeee sees 289, 290, 298 DrOVILOLIA cane cacccdeccsce-ctcsmeiowee ee Secession MERI se eee eerie 289, 298 CON UT: Ree ee ee Ae ee Ee toe ooh s aaa dad 335 fasti@iata oc. -cssceeecceceeeconc Pees etree eens See e Eee ee ner eae eee 335 LOLMOSA ne cuee cet eee SEC ECE CREE ESS Ee Saws leche eee eee eee 335 Tam es@ Ori .. sent ae eee ee eek hee ee eee Se Eee eee ee 201 longifolia. 5s. 52. 5.5 5ebeeSeeels eee eee ee ee eee eee Eee aae 289, 290 Reichenbachi.c.< ci scccescces ce cesseseesse eee eee eee ree eee 289, 335 TIGICS ewe w iced cena menaeeeece eee eee eee ee eee eee menee 2869 Smithiana ic. ccsscoc ccd ccce eee eal ee ee ee eee Ee eee eae 289 INDEX OF SYSTEMATIC NAMES. 515 : Page Shepherdia, canadensis .csegee se ewtiocs ceeaiencee wa ditercters snteintaseeineiceate 249 Sigillaria ..... See ore Siete ep ame See aside malice etiea apts copa kl aS ait 280 Somatogyrus esogonus. ..-.. eesia eee Rates als tere ees Sale Le oer eee ee mate 390 HPHeHOPbeLiseaacisas cio ce Scope mcete matte em caiomusicuisie mal sleleinoe me aaarateeras ee 134, 278, 280 CLASS D wicyetoeeteisvere es sass cletele ciniale alvin ciwiaintn e cloe taste miaeicielec wetaramestoe 280 Hoeninghausieescosscecselecceceeccoce Sa0dd6 CoSHhe SbobHS SaConE 280 SP iif eReerslococtain cs cioctelscmimaclocciosttesicecne es SUS ek nes ey 114, 115, 119, 211, 216 WPLEHERIM a. aiais Seles teselesicisclclewieiceioe< SAS EERO sey ru I Aine Ae Zan a ea es te ea 115 NS UCEY AY YOY TT) G16 2 aes ye A Rt eT Cy ae 25 SURE es IN YEER ENO See 5 5G GOB ESE BIS EE Ceara tie eae ie Ayia CE ee 398 OLS MAE Bera sain lo wie sloelsle cic lclsiniecnie eels cidiste slajeisioiae's suite sd Slacje oe claicive woes aiclers 279 TRUK CPOY UO CTS} aes eos SSS RET ae a ra NR Se Cer eee ee tg’ D1 el) Koy SHUN TEN STE) (RR So a ea Sore N Say ek SLUNG erp gL ad a ec 399 ancredi a aAMerican Ayseaces ke enleees ee scmicoeeeies a Gileaaeive we eae wan aos 35 Raxqdimm dubium: sas secees cece EAP tania ar SURE TEN, See ce apa fli 293 EROLEM GAC Ocoee erate eee Seat Cee elec la tally este fiat stave ei ete era tater cmos mranaln mts a aayemvete 360 BINS Tied CL Op cree epee eI STE TS oe ere rates en tan ie wis ese Sue ememnacioere sees 23, 24, 25 Pall Op by tES'se chee ain ceeicro a ceie eis a aloe wid GlolewnwioSnereciejowsleticideiniesiem cnleeuie melee 333 TET Y@S1 BR 2 a a ee Pa EE SM RMN ee ha 359 PRIEANOTHETIUMY sae 6 cme seek oe cease al Save ave erapera eae arete alata ate even are 23, 25 FROGEAD BSA POLLAN CA acl aici cre cael re aes oeiclnfels wicieieinie seine Se eins SN a noe Iouoeme ees 322, 346 Praag DOLrealis\tamanioe aercls is cheiticle siete Sette laaic cis iele biorwmuinteee eisiewisictlauiomeeianenise 289 MICrOpPh yaw apse Sale Sakae ees elise c)Siore rd Wictate ce walicnaincie ercte amie eterelats 304 TMETOINSX: 66a hes SSS HSE BBSO BHOO COE CASE SO SOE TSE CST ran ences ct Ge 23, 24, 158 ULTTEETE —o, Saeco He eee NE L VUTUE te aN CON nia aL A 23 Dia Gna Ry aT C= eee ee a eed at Rr eae Ds yA DS a sen eR 280 WSR so SCD SOE a I a OI AISI RRESHE ai a A a ae OER ee coe 22, 23 (ITT HAOTAT YO ESS coy SS eS eet ca eg ga se Ct Ce A 407 UGH ask Se a ES fate esd i a ey an oe area Hee RRP ea Dane Ren yet D 341 WEEN STEWART (SHEESH ea hE gO Ce rl er am Re eT eI at 390 WM HIDES) SCRE ear Le Sd ON NG aS 390 MEEDI CUNT Poe siero ee aise sine cis eisein eu Setawicre Weleee Se aie Seis Se ie iO eee A ee cieemetus 392 ARENSON BLOWN GUD