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CEe add, | ae gis 2S a nd one si Bi ml eens ai Hie ae "ai, Rowe ts “New York State Museum Bulletin Entered as second-class matter November 27, 1915, at the Post Office at Albany, New York, under the act of August 24, 1912 Published monthly by The University of the State of New York No. 192 | ALBANY, N. Y. DECEMBER I, I916 / The University of the State of New York New York State Museum Joun M. CLARKE, DIRECTOR GEOLOGY OF THE BLUE MOUNTAIN, NEW YORK, QUADRANGLE By WILLIAM J. MILLER PAGE - PAGE General geography and geology.. 7 | Origin of relief features.......... 57 Ptecanivrian TOCKS .<2... 2.2%. 1G2*| *eoucmic' products... 2, Jones 64 le Sig lens, se re SoM sec Sk: SP Ses Paar: < 67 Glacial and postglacial geology.. 48 | / . ALBANY THE UNIVERSITY OF THE STATE OF NEW YORK 1917 M83r-Ag16-1500 ‘THE UNIVERSITY OF THE STATE OF NEW YORK Regents of the University With years when terms expire — 1926 Puy T. Sexton LL.B. LL.D. Chancellor. - ~ Palmyra 1927 ALBERT VANDER VEER M.D. M.A. Ph.D. LL.D. Vice Chancellor -.- - - —- — — = —- Albany 1922 CHESTER S. Lorp M.A: LL.D. = - — ---- Brooklyn 1918 WiLiiaM NottTincHaM M.A. Ph.D.LL.D. - —- Syracuse i921 Francis M. CaRPENTER — -—- - -— -— — -— Mount Kisco 1923. ABRAM I. Erxus LL.B. D.C.L. —..—.—*: = ‘= ‘New York - 1924 ADELBERT Moot LL.D. - - - - - —- -— Buffalo 1925 CHARLES B. ALEXANDER M.A. LL.B. BoM BS Litt.D. - -— - = - = - — -— - — Tuxedo 1919 JOHN MoorE - - —~- -—- = —- - —- —- -— Elmira 1928 WALTER Guest Kettocc B.A. - - - -— -— Ogdensburg 1917 WILLIAM BERRI- — — —. -— — — — — - Brooklyn 1920 JAMES Byrne B. A. LL.B - - - - —- —- = — New York ' President of the University “Be Commissioner of ‘Education Joun H. FINLEY M.A. i Oe 0 Oe sb Deputy Commissioner and Atactant Commissioner for Elementary Education Tuomas E. Finzcan M.A. Pd.D. LL.D. Assistant Commissioner for Higher Education Aucustus S. Downine M.A. L.H.D. LL.D. Assistant Commissioner for Secondary Education CHARLES F. WHEELOcK B.S. LL.D. Director of State Library - James I. Wer, Jr, M.L.S. Director of Science and State Mascam Joun M. Crarke Ph.D. D.Sc. LL.D. Chiefs and Directors of Divisions Administration, Gzeorce M. WiLEy M.A. . Agricultural and Industrial Education, ARTHUR D. DEAN D.Sc., . Director Archives and History, James SuLLIVAN M.A. Ph.D., Dzrector. Attendance, JAMEs D. SULLIVAN Educational Extension, W1iLL1AM R. Watson B. = Examinations and Inspections, HarLan H. Horner M.A., Director _ Law, FRANK B. Gi_Bert B.A., Counsel for the University Library School, Frank K. WaLter M.A. M.L.S. School Buildings and Grounds, Frank H. Woop M.A. School Libraries, SHERMAN WILLIAMS Pd.D. Statistics, Hiram C. Casz Visual Instruction, ALFRED W. ABRams Ph.B. The University of the State of New York Department of Science, July 10, 1916 Dr John H. Finley President of the University SIR: I am transmitting to you herewith a manuscript entitled “ The Geology of the Blue Mountain Quadrangle” with the necessary - maps and illustrations. This is a report of special investigations carried on for this Department by Dr William J. Miller and I recommend that it be published as a bulletin of the State Museum. Very respectfully JoHnN M. CLARKE Director UNIVERSITY OF THE STATE OF NEW YORK OFFICE OF THE PRESIDENT Approved for publication this r1th day of July 1916 e 4 —_—s————lTlCoEm President of the Universitw New York State Museum Bulletin Entered as second-class matter November 27, 1915, at the Post Office at Albany, N. Y., under the act of August 24, 1912 Published monthly by The University of the State of New York No. 192 ALBANY, N. Y. DECEMBER I, 1916 The University of the State of New York New York State Museum cs % APR 19 1917 a TAIN, “tona| Wyse sonian In aan Stity Joun M. Crarke, Director % GEOLOGY OF THE BLUE MOU NEW YORK, QUADRANGLE BY WILLIAM J. MILLER GENERAL GEOGRAPHY AND GEOLOGY The territory covered by the Blue Mountain quadrangle? lies in the heart of the Adirondack mountain region and all in northern Hamilton county excepting less than 2 square miles of its northeast- ern corner which extends into Essex county. It comprises an area of nearly 215 square miles. The geographic center of the 10,000 square miles of Precambrian rock in northern New York lies within, or close to, the northern portion of the quadrangle. The region is very typical of the great Adirondack wilderness, being rough, well watered, densely wooded, sparsely settled, and with few traveled roads or trails. The difficulties of making a systematic geological survey of.such a region, especially those portions where forest fires have wrought havoc, are not easily exaggerated. It is a pleas- ure to record that several of the writer's former students of geology —Messrs J. P. Hull, H. Insley, and L. W. Bissell—at different times accompanied him into some of the roughest country and rendered valuable assistance. The only villages in the area are Indian Lake, Blue Mountain Lake, and Long Lake, no one of which has more than a few hun- dred residents. Most of the comparatively little farming of the region is confined to the vicinities of these villages and along Cedar river. Lumbering is still an important industry, though much of the first-growth timber has been cut. During the summer 1See map in pocket of back cover of this bulletin. 8 NEW YORK STATE MUSEUM seasons hundreds of people go to the hotels or occupy cottages on Long lake and Blue Mountain lake. No railroad enters the quadrangle, the nearest one being the Raquette Lake Railroad branch of the New York Central (Adiron- dack division) with terminus at Raquette Lake village about 8 miles from the western edge of the quadrangle. The traveled roads are clearly shown on the accompanying map. It is of interest to note that fully one-third of the area of the quadrangle (or about 75 square miles), including the northern-central and eastern-central portions, is wholly without a used or well-defined road, or even trail. The maximum range of altitudes within the map limits is from a little less than 1560 feet, where Cedar river leaves the map on the east, to 3759 feet at the summit of Blue mountain. Ranking next in altitude are the two summits of Dun Brook mountain, 3580 and 3565 feet respectively, and Fishing Brook mountain, 3550 feet. The largest, high, rugged mountain group occupies some 35 or 40 square miles bounded by Mount Sabattis on the west and Fishing Brook and Dun Brook mountains on the east. At least 15 points within this group reach altitudes of 3000 feet or more. In the southeast, Blue Ridge and the prominent ridge just south of it show altitudes of over 3000 feet, the maximum figures being respec- tively 3481 and 3350 feet. Along the central-southern border, two points attain altitudes of about 3150 feet, these really being only on spurs of. the Panther mountain mass of the northern part of the Indian Lake quadrangle. As compared with the eastern and south- eastern Adirondacks, there is no very prevalent trend of mountain masses, though there are some suggestions of the usual northeast— southwest strike. An important division of drainage — that between the Raquette and the Hudson rivers — passes across the quadrangle. Beginning at the middle of the northern boundary of the quadrangle, this watershed passes over Burnt mountain, Fishing Brook mountain, the northern summit of Dun Brook mountain, Buck mountain, Blue mountain, less than a mile south of Blue Mountain and Eagle lakes, and along the crest of Blue Ridge to the western border of the area. This watershed marks essentially the crest of the central portion of what has been called the main axis of elevation of the Adirondack region. Two valleys (below described), with greatest altitudes of only about 1800 feet, cut completely across this axis within the quadrangle and constitute two of the three or four lowest valleys Oye, UleJUNOPY olfq JO We Ustojsvoyjnos OY} SSO1oe JSIMYINOS 9} WwOtf UdIS Se (Jo04 6SZe apnyyye) ureyunouw ont qd “A UN “94R'] uleyunosy snp “sso[oy- “a “Y Aq 0J0Y4g I 9}°Id ‘punOLSYy IVY I[ppiuu oY} JO JYSI1 oy} 0} Ysnf puod sva{ZQ pu yyoq oY} 0} jsf Sol] UlBJUNOU PKIFY SIMO “9SRI]IA oye] SuUOT Fo JsvayJsoU ou e node jUIOd B WOT} OAL] SuOT sso.19e pavaAjsaMy Nos Aor ‘A CN ‘wepsjog ‘usl[y WiMeq sq oVOYg Z eld t * ate Lomi. 3 : rad Ee ea Plates Photo by G. B. Wells, Blue Mountain Lake, N. Y. View southwestward across Blue Mountain lake from Merwin’s Hotel. Eagle and Utowana lakes are just visible in the distance. 4 ; ’ a Ae! ® : i o ae ae i ol Ur eae Tee ee 7 ae Pee eee es GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE 9 of this sort in the Adirondacks. One of these extends across the quadrangle from the vicinity of Pine lake westward to Blue Mount- ain and Utowana lakes, and the other across the northern side of the quadrangle. Raquette river, a tributary of the St Lawrence, is the largest north-flowing stream out of the Adirondack region. Blue Mount- ain lake drains westward through Raquette lake into Raquette river and into Long lake which latter is merely an enlargement of the river itself. Two prominent northeast-flowing tributaries of the upper Hudson river (Cedar river and Indian river) cross the south- eastern portion of the quadrangle, Cedar river having some 15 or 16 miles of its course, and Indian river only 2 or 3 miles of its course, within the map limits. Rock river, the largest feeder of Cedar river within the area, has its source in the hills south of Blue Mountain lake and flows eastward nearly across the quadrangle, © Rock lake being only an enlargement of the river. The Chain lakes, which are partly within the map limits, drain southward into Rock river about a mile above its mouth. In all, more than fifty ponds and lakes, or parts of lakes, lie within the quadrangle. Excepting the glacial and postglacial deposits, all the rock forma- tions of the quadrangle are of Precambrian age. Given in the regu- lar geologic order they are as follows: Glacial and postglacial deposits: Till, moraines, erratics, kames, lake deposits, etc. 7 Diabase: Two or three small dikes ; nonmetamorphosed. Pegmatite: Frequently found cutting nearly all types of the older rocks, including the gabbro ; nonmetamorphosed. Gabbro: Occasionally occurring as dikes or small stocks; more or less gneissoid ; intrusive into the older rocks. Syenite and granite: These are the most widespread rocks of the region with many facies from a basic or gabbroic phase of the syenite to typical granite and granite porphyry; distinctly gneis- soid ; intrusive into the Grenville and anorthosite. Anorthosite: ‘Two small masses only which are separated from the great area lying mostly in Essex county; more or less gneissoid ; intrusive into the Grenville. Grenville series: Prominently developed only in the southern half of the quadrangle; thoroughly crystalline stratified rocks, includ- ing various gneisses, limestones, and quartzite. Some normal faults are present but they are far less prominent than in the eastern and southeastern Adirondack region. IO NEW YORK STATE MUSEUM Published statements dealing directly with the geologic features -of the quadrangle are very scant, consisting of only a few para- graphs altogether. The following list includes the principal papers containing references to the quadrangie itself or the Adirondack region in general: 1839-41. Emmons, E. Geological Reports on the Second Dis- trict of New York. 1839, p. 224-30; 1841, p. 113-33. These are the earliest published statements on the geology of Hamilton county. 1842. Emmons, E. Geology of New York, pt 2, on the Geology of the Second District, p. 414-17. 1897. Kemp, J. F. & Newland, D. H. Preliminary Report on the Geology of Washington, Warren, and Parts of Essex and Hamil- ton Counties. 17th Annual Rep’t N. Y. State Geologist, p. 551-53. 1898. Kemp, J. F., Newland, D. H., & Hill, B. F. Preliminary Report on the Geology of Hamilton, Warren, and Washington Counties. 18th Annual Rep’t N. Y. State Geologist, p. 156-57. 1905. Cushing, H. P. Geology of the Northern Adirondack Region. N. Y. State Mus. Bul. 95. A valuable treatise on Adiron- dack geology in general. 1907. Cushing, H. P. Geology of the Long Lake Quadrangle. N. Y. State Mus. Bul. 115. A detailed account of the geology of the region immediately north of the Blue Mountain quadrangle. 1912. Miller, W. J. Early Paleozoic Physiography of the South- ern Adirondacks. N. Y. State Mus. Bul. 164, p. 80-94. Presents evidence to show that the central Adirondack area was not sub- merged during the Paleozoic era. 1913. Miller, W. J. The Geological History of New York State. N. Y. State Mus. Bul. 168. A book on the geology of the State with many references to the Adirondack region, particularly in chapter 3. 1914. Miller, W. J. Magmatic Differentiation and Assimilation in the Adirondack Region. Geol. Soc. Amer. Bul., 25 :243-64. Discusses the origin and age relations of the various facies of Adirondack syenite and granite. 1916. Miller, W. J. Origin of Foliation in the Precambrian Rocks of Northern New York. Jour. Geology, -24:587—620. PRECAMBRIAN ROCKS Grenville Series General character. The Grenville rocks of the Adirondack region, so far as our present knowledge is concerned, are to be GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE TI classed with the oldest known formation in the crust of the earth. They are very largely, at least, stratified rocks, the original sedi- ments such as limestones, sandstones and shales having been thoroughly metamorphosed into crystalline limestones, quartzites, and various schists and gneisses. Since the foliation and stratifica- tion planes are always coincident, it seems quite certain that the Grenville strata have never been subjected to very severe lateral compression, at least not sufficiently great ever to have obliterated the bedding surfaces. As judged by the character, great thickness and areal extent not only throughout the Adirondack region but also through much of eastern Canada, we may safely conclude that the Grenville beds were deposited under marine waters much as were the sediments of later geologic periods. Concerning the character and location of the lands from which the sediments were derived and the sea floor upon which they were deposited, we are at present ignorant. It is certain that the Grenville rocks are many millions of years old. Areal distribution. Approximately 26 square miles of Grenville rocks are separately represented on the accompanying geologic map of the Blue Mountain quadrangle. There must also be added some IO or 12 square miles more represented in the mixed gneiss areas and also inclusions mapped and unmapped in the igneous rocks. Thus about one-sixth of the area of the quadrangle 1s occupied by Grenville strata. On the Newcomb sheet the writer has seen large areas of Grenville; Cushing has mapped considerable areas on the Long Lake sheet; and the writer has seen many Grenville outcrops on the Tupper Lake sheet along the road from Long Lake to Long Lake West. Our knowledge is therefore sufficient to make it positive that the Grenville is prominently represented in the midst of the Adirondack region. Accordingly, certain older views implying very slight development of the Grenville there must be abandoned. Within the quadrangle no attempt has been made to map the different facies of the Grenville separately because the heavy drift accumulations and consequent scarcity of exposures in certain por- tions of the Grenville valleys render any satisfactory areal sub- divisions impossible. To a very considerable extent the crystalline limestone with its closely associated hornblende and pyroxene gneisses might be separately mapped, but it has seemed best to allow the known extent of the limestone areas to be brought out by indicating the actually observed outcrops of that rock upon the geologic map. IZ NEW YORK STATE MUSEUM An important Grenville area, nearly 4 miles wide from north to south across the valley at Indian Lake village, extends without an interruption up the Cedar river valley for 11 miles with a width usually from one-quarter to 1 mile. The most abundant rock of this area appears to be coarse, crystalline, graphitic limestone with closely associated hornblende and pyroxene gneisses. Exceptions are I to 1% miles north and northwest of Indian Lake village where the rock is largely a white feldspar-quartz gneiss. Another prominent Grenville belt extends from Pine lake with- out a break through the valley of Rock river to Thirty-four marsh and thence into the basin of Blue Mountain lake. Its widest places are in the vicinity of Rock lake (nearly 2 miles) and in the Blue Mountain lake basin (nearly 1% miles). The basin of Blue Moun- tain lake is largely occupied by Grenville limestone, many ledges being visible both above and below the water level. Within this belt the only other limestone exposures were observed on Rock tiver about a mile below the outlet of Rock lake. In the vicinity of Thirty-four marsh, gray Grenville gneisses only were seen. Quartzite and gray gneisses are prominent in the ridge just north of Pine lake, while on Cedar river, between one-half and 1 mile above the mouth of Rock river, white feldspar-quartz gneiss together with quartzite, hornblende gneiss and gray banded gneisses are prominently developed. Northwest of Rock lake heavy drift rather effectually conceals the Grenville. As shown on the geologic map, the two belts of Grenville just described — one along Cedar river and the other along Rock river — are certainly connected through the valley south of Rock lake, but only a few exposures of hornblende and hornblende-garnet gneisses and white gneisses could be found on account of the heavy drift in this valley. The small area extending northeastward from Unknown pond contains several exposures of Grenville limestone and it apparently consists mostly of this rock and associated hornblende gneiss. The prominent depression crossing the line from the Blue Moun- tain to the Newcomb. sheet and containing the Chain lakes (except the first and second), Mud, Deer, and Jackson ponds, is certainly almost entirely occupied by Grenville limestone and its associated hornblende gneiss. Where the road to Newcomb crosses the Essex county line, a small area of Grenville shows various quartzitic and pyroxenic gneisses in comparatively thin layers. This is really only the west- Pts GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE I3 ward extension of the large Grenville area in the vicinity of Newcomb. In the extreme northeastern corner of the map an area of less than a square mile shows few outcrops, these being chiefly of hornblende gneiss. The inclusions large enough to be separately mapped north of Sprague pond, 2 miles south-southwest of Sprague pond, west of Grassy pond, west of Minnow pond, and west of Buck mountain consist of hornblende gneiss. The small mass on the side of Stephens pond consists of white feldspar and pyroxene gneiss with some limestone. The small area on the road 1 mile west of Fishing brook crossing in contact with, and more or less shot through by, pink granite consists of hornblende gneiss and nearly white feldspar- quartz gneiss containing some pyrite and pink garnets. Three small areas of Grenville within the mixed gneisses are respectively on the eastern shore of Long lake one-third of a mile. south of the northern map limit; on the western shore of the lake directly opposite the last named area; and on the western shore of Long lake a little south of west of Long Lake village. The first two areas named show large exposures of white sillimanite gneiss and gray gneisses containing red garnets and pyrite, while the second named area shows large outcrops of a greenish gray almost syenitic looking gneiss with specks of pyrite. Description of Grenville types. For purposes of comparison with other areas with the idea of possibly working out certain of the broader structural and stratigraphic relations of the Grenville series in the Adirondack region, the more important types of Gren- ville of the quadrangle are here described somewhat in detail. Crystalline limestone. The southern half of the quadrangle, in common with the Newcomb, the southern half of the Schroon Lake, the North Creek, and the Thirteenth Lake quadrangles, shows rather extensive development of Grenville limestone, decidedly more so in fact than the southeastern, southern, and southwestern border portions of the Adirondacks. Throughout all the area just men- tioned much of the limestone is very similar, being thoroughly crystalline, very calcitic, usually graphitic, mostly closely associated with hornblende, hornblende-garnet or pyroxene gneisses, and of great thickness — several thousand feet at least. Sometimes the limestone ledges scarcely show stratification, but usually the original bedding surfaces are marked by layers in which the dark minerals are more abundant (see plate 4). Because of T4 NEW YORK STATE MUSEUM its plasticity under pressure, the limestone is generally much folded or twisted so that dips and strikes are very variable. As already stated, the actually observed limestone outcrops are indicated upon the accompanying geologic map. Perhaps the most abundant variety of limestone is medium to moderately coarse grained, nearly white, with irregular quartz _ grains in varying amount up to 20 per cent, scattering flakes of graphite (often with perfect hexagonal outlines) up to 4 or 5 mm across, and sometimes tiny specks of pyrrhotite. Many big exposures of such rock occur along Cedar river within 2 miles vf where it enters the quadrangle; in the vicinity of Indian Lake village, and in and around Blue Mountain lake. Another variety is much like the above except for numerous grains or small crystals of pale to dark green pyroxene (coccolite) scattered through the rock. The pyroxene is often more ‘or less serpentinized. Still other variations are due to absence of quartz or graphite from either of these varieties. Irregular shaped masses of pyroxene or hornblende gneiss have sometimes been forced into the relatively plastic limestone under pressure (see plate 4). Hornblende-garnet gneisses. Rocks of this kind are frequently found in contact (or interbedded) with the limestone. The most common facies is a fine to medium-grained, dark-gray gneiss con- sisting of about equal parts of hornblende and feldspar and in which are embedded scattering red garnets (almandite) up to three- quarters of an inch across. Among the readily accessible exposures are: one-half of a mile east of Indian Lake village; 114 miles south- east of Forest House; and on the island one-quarter of a mile northwest of Blue Mountain Lake village (no. 21, table 1). A less common facies is somewhat similar to the above but has some biotite and the scattering, rounded, red garnets (almandite) up to 5 or 6 inches in diameter which are completely inclosed within envelops of black hornblende crystals. This type of garnet gneiss is exactly like that recently described by the writer as occurring at the garnet mine on Gore mountain near North Creek. Good outcrops may be seen 214 miles south-southeast of Forest House in a small mine prospect. Better exposures occur in the old garnet 1Econ. Geol. Magazine, 7:'5, 1912, p. 403-56 wilsow Nery. State Mus. Bul. 164, 1913, p. 95-103. Photo by W. J. Miller, 1914 A ledge of Grenville limestone on Cedar river, one-half mile northeast of the main road bridge across the river. Stratification of the limestone is well shown as well as the rounded masses (dark colored) of Grenville pyroxene gneiss which have been kneaded into the relatively plastic limestone under pressure. Plate 5 Photo by W. J. Miller, 1914 Falls at the head of the gorge on Cedar river due east of Waterbarrell mountain. The rock is Grenville limestone. GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE 15 mine one-half of a mile east of Bullhead pond on the adjoining Newcomb sheet. Hornblende-feldspar gneiss. These gneisses are also very com- monly found in contact (or interbedded) with the limestone. They are to be distinguished from the hornblende-feldspar-garnet gneisses above described chiefly by the absence of garnet. One facies 1s medium grained and nearly black with only 10 to 20 per cent of feldspar. Sometimes this gneiss, within an inch of a limestone contact, is full of tiny red garnets, the lime for their development apparently having been furnished by the adjacent limestone during the process of metamorphism. _ Another variety is fine to medium grained and contains perhaps 30 to 40 per cent of feldspar together with a few per cent of biotite These hornblende-feldspar gneisses are nearly. always found where there are extensive exposures of limestone. Pyroxene gneisses. So far as could be determined, these gneisses also mostly appear to be closely associated with the limestone either clearly interbedded with them or distributed in irregular shaped masses in them, having been broken up and forced into the relatively plastic limestone under pressure (see plate 4). A common variety of the pyroxene gneisses is fine to medium grained and greenish gray, consisting largely of bright green pyroxene (coccolite), quartz and feldspar with numerous tiny red garnets and some titanite through the mass. Sometimes a crude banded appearance is due to a concentration of the pyroxene in layers parallel to the foliation. Excellent exposures occur I mile south-southwest of Indian Lake village in the mixed gneiss area (nos. 6 and 11, table 1). 7 A rock very similar to this, but with numerous graphite flakes instead of garnet, outcrops along the river just east of Waterbarrel mountain. Another variety consisting mostly of green pyroxene (coccolite) with some quartz and a little feldspar is very frequently closely involved with the limestone. Excellent outcrops occur along the road near the county line g miles east of Long Lake village, and near the eastern end of the largest island in Blue Mountain lake (no. 22, table 1). Quartzites. As compared with the mapped areas of the southern and southeastern Adirondacks, quartzites are not so prominently developed in the Grenville of the Blue Mountain quadrangle. Also they vary greatly in composition, scarcely any two localities showing MUSEUM YORK STATE NEW 16 ‘OBRT[IA Oye] BUO'T JO JSAM sop g pvor oy} UO ‘ES ‘ou faut] AJUNOD xXoOSsaT Jo SB O[IU B JO PAIY}-9UO peor UTE “TS “OU FadeTIA oye] SUOT JO JSOMYJNOS oI 1 ‘Lh ‘OU faye] Ule}UNOPL oN] UL PUR]st soda] Jo JSBIYINOS OU BV JO Y}J-ouo purvyst [[eus “Qe ‘OU Saye] UleJUMOP, ON] _ UL pULIST Jsosavy OY} OF JXOU JO Jsvoy NOS Jsnf puryst [Jeus ‘fe ‘OU Foye] UreJUNOY ON] UL pUL[ST Jsosivy JO pus Uto}svo ‘eZ “OU SISTA oye] UIeJUNOP oN[_ JO JsoMuUjsOU oyIt ev JO F;eY-aUO purRyst UO ‘Te ‘OU Foye] OU JO JSAMYINOS ojtut B FO JyeYy-9UO JOATI ABpd>) UO ‘oz ‘ou :puod UMOUYUL, JO JsaMYINOS ou T Ure}UNOUL yo do} ‘61 ‘ou ! (Bore sslous pox V WIOA]) 98RT[IA oye] URIpUT JO JSOMYINOS-YJNOS opIU 1 ‘TT ‘OU S UTeJUNOUT Jo1I1eqGI1971v AA JO ISvO “YOU soplut YI AVAL aAepay uo *Z ‘ou !(vdIV SSIOUS poXIU V WOJJ) advI[IA oye] ULIPUT FO JsvoyjNOs-YINOS sop YI ‘O ‘oN Fe eT ae ha a ade ae a el gh eee Ba ea STAT t Pee seeleesereleseseelsneee slot se eereen er lee 62 es aoe +909 seeeeely teveea fees cealeceeeeletatesleseens [eens eleceees cunt rlersenelpg CRC CBO ov ER Ee OR Re ROLE in hy Mando) seers ba e.6 eh Oy) 6 See a We Pay eS aN] oT} aT LE Ee TLR SEL iby pea ER a kao (IN Ca eR URE SY scx or '1O ¢ gl eee OD pat ty z ou oat a58-8, 30 6) |\e>s..8 B83 Pa or petadeen | tata eRe eaelSe EA eee eee lew eens ET Pa Oo hr Of z‘uy—IO EF ay 7 LI (q)61 9g Qe See May Maks a a Nai? aa eveuse iran) E1490 a AP ae pels Silat or BEB A of teneesloeeeenloy I ‘uy—[O L228 “** "lor pg aD oF ac SC es) Ce oc (ICAP CD es ee oraatr Pek eeeler se eelon Viti ol Me eta Ns aM iL SEA AI 2 | A St z ‘10 BPS ES ay 8 RA ‘tee Se OW aia I a Hae) opty teeter lesecnn @ SRNR on Oe os or Cras 2 LE CB ey Beane ae 8, ‘erg mig 8m | BRR RES] has aa is os ML nae a enone lever er leas acig seeeeely sae eee sees nalon St ‘1O-“"IV S zs oee eS ute "02g e*seeeeeteeeees oy . PE ley fala wR ee TE I CE 4G aman PO Opis 4 Se ‘uy—10 PASEO AD CLO eee, 4S LTH oy Wy eoebes ene eT Sa a os slew eee oleeeseslovcen be seeele peewee le revert ecnees Og Se a aT. oz rea Te seorr be ed seee see T . ele. sae */a]9 911 ee ee ee PIO she FLED FOIE LIN IA MUS OT A rere A Lg LIA DAT «8, os fone Ls z pasity eeees sees . ttle sees AKeaie EE ab Sy reveerlor ceeeslesnesacl|e ef ep or WV ¢ ISt sto tate Te kT | y N : hy y bo ts hy ele hj ” Po ldet eles de ee ee lee ioe oe | eo] ef ale Bee em melee Re es E(B ee ot : toe bee . Qu oOo a a es on eae hall age) wea Re salar ghar: ell tL Se: oy 5 | @ i ct be i = 1 f). ¢ : § é z j B | ea Bp oT Rl als =] ct ta) a) SYIOI I[[IAUsINH JO SUOT}IOS-UI,, — I 9TqQey ‘QOURISIP OY} UL SMOYS FNVF Jsnsy} [[eUIs YW ‘“sslous spus[quaoy dI][IAUaIT) st yOos AvIS BUIATIIAO OY} PUB 9UOJSOUMT d][LAUIS) SI YOOI YM dy, “ULeJUNOUT [Jatseq1aJeA\ JO JSva oNp AaAIA ABpad Jo 98108 ayy uw Fi6r “a9 “£ “MA Aq OF04g 9 938Td Sc Fade GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE 17 the same kind of rock. Most of the quartzites are fine to medium grained and thin bedded. In general there are two important varieties — one with feldspar and the other without. The feldspathic quartzites carry from 10 to 25 per cent of feld- spar together with 5 to 15 per cent of either biotite, muscovite or green pyroxene, or slight amounts of tiny red garnets or graphite flakes. The nonfeldspathic varieties contain 90 or more per cent of quartz together with either biotite or muscovite. Among the better quartzite exposures are the following: on several islands in the northern part of Blue Mountain lake; in the ridge just north of Pine lake; and along the road at the county line 9 miles east of Long Lake village. Feldspar-quartz-biotite-garnet gneisses. ‘These gneisses are not very abundant and vary greatly. Perhaps the most common variety is a fine to medium-grained, crudely banded, light-gray rock made up mostly of feldspar and quartz in addition to 10 or I5 per cent of biotite and varying amounts of pale pink garnets. Good exposures may be seen respectively three-quarters of a mile and 114 miles east of Blue Mountain Lake village on the road; on the small island just southeast of next to the largest island in Blue Mountain lake (no. 23, table 1) ; and on the ridge just north of Pine lake. Feldspar-quartz gneisses. These light-gray to white gneisses are represented in considerable amount. The most common variety is medium grained and made up very largely of feldspar and quartz with scattering red or pink garnets and almost no dark minerals. In exceptional cases grains of pyrrhotite or pyrite, or flakes of graphite, occur. Rocks of this sort are extensively exposed from 1 to 1% miles northwest and north of Indian Lake village. Other good outcrops occur on Cedar river one-half to three-quarters of a mile southwest of Pine lake (no. 20, table 1) ; on Cedar river 1% miles northeast of Waterbarrel mountain ; and on the road respectively 6 miles (no. 53, table 1) and 9g miles (at the map edge) east of Long Lake village. Apparently these gneisses are the same as certain white gneisses recently described by the writer as occurring within the Lake Pleasant! and the North Creek? quadrangles. That these are not eruptive rocks is quite certainly proved by their interstratification with definitely known Grenville strata and by their content of ’ Nov eewate: Mus, Bul. 182; peti. “rors. 2N. Y. State Mus. Bul. 170, p. 13. 1914. 18 NEW YORK STATE MUSEUM graphite at some localities, for example, on Cedar river from one- half to three-quarters of a mile southwest of Pine lake. This matter is of considerable importance because these rocks so closely resemble certain white gneisses recently described from the Sara- toga quadrangle by Cushing and by him rather thought to be ancient granites belonging with the so-called ‘‘ Laurentian granite.” 1 Another variety of the feldspar-quartz gneisses is light gray, medium grained, very homogeneous and rather syenitic looking. This rock contains specks of pyrite and weathers brown. When first encountered it was thought to be a special facies of the syenite, but later the same sort of rock was found interbedded with true Grenville gneiss. Good outcrops may be seen in the small Grenville area I mile southwest of Long Lake village (no. 43, table 1); in the small Grenville area 2 miles northeast of Long Lake village ; and on Cedar river respectively 1% (no. 7, table 1) and 3% miles north- east of Waterbarrel mountain. Sillimanite gneisses. These are also Page gray to white gneisses but are rare, having been found at only two places. A big ledge, 100 feet across within the small Grenville area 2 miles northeast of Long Lake village, consists of fine to medium-grained, banded, feldspar-quartz gneiss with some layers very rich in glistening needles of sillimanite. The top of the mountain ridge (mixed gneiss) just southwest of Unknown pond shows sillimanite and garnet gneisses all shot through by granite. The sillimanite gneiss is a mass of fine-grained feldspar through which are scattered delicate, glistening needles of sillimanite in great abundance. Tremolite gneiss. At the map edge on the Long Lake-Newcomb road, tremolite gneiss is interstratified with thin-bedded quartz- feldspar gneiss and dark pyroxene gneiss. The pone oe of this rock is shown by no. 51, table I. Feldspar-graphite gneiss. On the largest of the three small islands just southeast of the largest (Long) island in Blue Moun- tain lake, there are good exposures of gray to brown, medium- grained, thin-bedded, feldspar-graphite gneiss, the graphite being disseminated through the rock as numerous tinv flakes (no. 26, fable 1). Anorthosite-gabbro Two small areas of anorthosite-gabbro are shown on the geologic map respectively 114 miles northeast and 1%4 miles north of the = TaN, Vo State Mus. Bul; 160, (p) 21-26. 4 om GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE I9 Long Lake bridge. In spite of considerable variations in the char- acter of these rocks, they are distinctly different from any other rocks observed within the quadrangle. In every essential respect they appear to be like the anorthosite-gabbro border facies and small outlying masses of the great anorthosite body within the Long Lake quadrangle as described by Cushing. Also they are precisely like the border facies of the anorthosite area along the Hudson river (Newcomb sheet) as seen by the writer during the summer of 1914. Therefore it is with some confidence that the two small masses of anorthosite-gabbro within the Blue Mountain quadrangle are regarded as of the same age as the great anorthosite body, being simply outlying masses or off-shoots of the large body similar to those within the Long Lake quadrangle described by Cushing. Identity of age has of course not been established since the two small areas are separated from the main anorthosite body by an interval of nearly 10 miles. According to Cushing the anorthosit (and associated anorthosite-gabbro) is distinctly older than the syenite. In the area on the eastern shore of the lake the best and most typical exposures are in the immediate vicinity of the southern end of the diabase dike (see map) on the point which there extends into the lake.2 This whole point is practically a solid exposure. Within 30 or 40 feet of the dike the anorthosite-gabbro best shows its variable character. It is mostly light gray to nearly white, medium to very coarse grained and largely devoid of gneissic struc- _ ture. One patch of the rock is almost pure labradorite feldspar with fresh, bluish gray, rounded cores up to 1 or 2 inches across clearly showing the twining bands and embedded in a finer grained granular matrix’ of white plagioclase. These cores clearly represent the portions of the original large labradorite crystals which were uncrushed during the process of metamorphism. Most of the rock, however, is medium to only moderately coarse grained with fewer and smaller uncrushed labradorite cores, some andesine, a consider- able percentage of dark minerals (chiefly hornblende, pyrite and magnetite), and some red garnets. Very locally the dark minerals may reach 30 to 40 per cent, when the rock is dark gray and dis- tinctly gneissoid. The gneissoid structure becomes fainter with diminution of dark minerals, much of the rock not showing it at all. Some of the rock close to the contact with the diabase dike tN. Y. State Mus. Bul. 115, p. 473-76. 10907. 2 This anorthosite-gabbro, at the water’s edge, contains a small inclusion of typical Grenville limestone. 20 NEW YORK STATE MUSEUM is very light gray and more compact looking, the feldspar having a dull instead of the usual shiny luster. In thin section (no. 66, table 2) the feldspar and hornblende appear to be badly decomposed. Possibly this facies 1s an effect of the heat of intrusion of the dia- base dike. About 50 feet east of the dike the anorthosite-gabbro has the same mineral composition (no. 64, table 2) but is con- siderably weathered to brownish gray, shows very few, small, uncrushed feldspar cores, and is moderately gneissoid. From 75 to 90 feet east of the dike the rock is weathered to a deep brown, is clearly gneissoid and looks so much like a basic phase of the syenite that, seen alone, it would scarcely be regarded as belonging with anorthosite (no. 65, table 2). All the facies just described grade perfectly from one into the other, but farther eastward, that is beyond 100 feet from the dike, there are no exposures at the base of the mountain so that the relation of the anorthosite to the syenite of the mountain could not be determined. Along the lake shore for one-quarter of a mile northward from the rocky point just described there are ledges of gray anorthosite-gabbro. Then, after a short interval, there is a ledge of what is taken to be a basic (gabbroic) phase of the syenite (no. 55, table 4). A few rods directly south of the rocky point there is a ledge of either gabbroic anorthosite or a basis phase of syenite, probably the latter (no. 56, table 4). Still farther south along the lake shore, there are out- crops of basic facies of the syenite. Thus, although the evidence is not conclusive, the anorthosite-gabbro appears to grade into a basic phase of the syenite of the region. Similar gradations have been quite definitely proved within the Long Lake quadrangle by Cushing who suggests that “the observed relations seem to point to the conclusion that the change is due to actual digestion, by the molten syenite, of material from the adjacent (anorthosite) gabbro.” ? ake In the small anorthosite-gabbro area west of the lake, big out- crops cover fully one-half of an acre. The rock is much like the main bulk of the anorthosite-gabbro just described as occurring on the eastern shore of the lake. Toward the interior the mass is entirely devoid of foliation, is light gray, shows occasional uncrushed, bluish-gray labradorite crystal cores up to one-half or three-quarters of an inch across, and contains a considerable per- centage of dark-colored minerals and some garnet. Otherwise much of the rock is darker gray and moderately gneissoid to almost black 1N. Y. State Mus. Bul. 115, p. 479. 1907. GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE 21 and highly gneissoid. Within this anorthosite-gabbro there are several inclusions of light gray Grenville gneiss up to 2 or 3 feet wide, some bands of amphibolite and a few masses (one 25 feet across) of granitic syenite, all of these being arranged approximately parallel to the foliation of the inclosing rock where that structure is present. Whether the granitic syenite occurs as inclusions or as dikelike intrusions could not be positively determined, though they are most likely the latter. Table 2— Thin-sections of anorthosite — gabbro j | oO ) lo SLIDE 2 3 3 & 2 3 isto 2 ie N |= NUMBER ES g Seas 3 2 Sf % o 3 2 3 g 2 8 3 S (o/8/¢}/ s1/S/si el. & 3 & 5 Sir ite & Se eC TE les nore et kneel BS lo me |b. LO ee r7e 5(c)|an.-Lab. 63] 35|...|... Pais te I .| little} little] little].....].. Sato Pita. . os) £76 S(d)lan-lab.) SS) tT] Ole. . | ocr. I fitéle|-tittle|!..).- oleae. little!... ile hee aes E7e.5(e) |an.-Lab. 7OloTL) ES |i 0s). 0.0% Se nie hes st ie thee lee ep ae y lem ay (mga ; RSA? ato T7e 5@)ian--Labe 77) TS}. eles. Be eS ee te ewe little} little] little)..... ists GS a2, 17e 5(g)|an.-Lab. 80} 16]...|... little|etey ede 4 Bless Ser egaece | ZA ne JS Sea PER (i) Ana. SOLS 's.bs eal ehane lore errs Tene eeal alis te ekcvaltee seh eiiclelc-< . . Gea | IO i 17e glol.-Lab. 66} 6]...| 2 ASPET lralis, (ok, 3 little} little]..... leckeit 8s lerane Nos. 61 to 66 inclusive are from the area on the eastern shore of Long lake; no. 58 is from the area west of Long lake andis more acidic than the usual rock there. ; A number of small pegmatite dikes cut through the whole mass of rock. There are no exposures of any kind immediately surround- ing the anorthosite-gabbro area so that nothing could be learned regarding its relation to the other rocks of the vicinity. Syenite and Its Facies The syenite and its basic and acidic facies are the most wide- spread of all the rocks. As here considered they vary greatly, ranging from what may be termed a normal quartz syenite to a basic (dioritic to gabbroic) facies on one hand to granitic syenite and granite on the other. Since these facies grade back and forth into one another, sharp boundary lines between them do not exist and their separation on the geologic map depends to a considerable extent upon personal judgment based upon some years of experience with the rock types and checked up by the study of numerous thin sections. As is now well known, the syenite is younger than the Grenville series and distinctly intruded into it, there often being dikelike 22 NEW YORK STATE MUSEUM tongues of syenite cutting the Grenville and clearly defined inclu- sions of Grenville in the syenite. According to the work of Cush- ing on the Long Lake quadrangle, the syenite is also younger than, and intrusive into, the anorthosite.1. For most part at least, the granites of the Blue Mountain quadrangle are only differentiation phases of the great syenite body and of practically the same age as the syenite, though the possible presence of some unproved granite either distinctly older or younger than the syenite must be admitted. This matter is more fully discussed in connection with the granite. Both the gabbro stocks or dikes and the diabase dikes are certainly younger than the syenite. Normal quartz syenite. More than one-third of the area of the quadrangle is occupied by the normal syenite, it being widely distributed in exceedingly irregular bodies. As usual throughout the Adirondacks, the normal or most typical syenite is dark greenish gray when fresh and weathers to a light brown, though apparently fresh pinkish or reddish syenites do occur rather locally. The depth of weathering usually varies from a fraction of an inch to several inches or, more locally, to a foot or more. In general the amount of weathered rock here seems to be greater than in the border regions of the Adirondacks, doubt- less due to the fact that the central region was neither so long nor | so vigorously glaciated. Immediate surfaces of syenite ledges are sometimes light gray to almost white, probably due to the leaching out of iron compounds by water rich in decomposing organic matter. A case in point is the big, bare ledge which looks like a snow bank in midsummer well up on the side of Blue mountain and clearly visible from the south for some miles. A hand speci- men from this ledge shows a thin, white surface layer under which is a brown zone an inch thick and which in turn merges downward into the greenish gray fresh rock. As regards granularity, the normal syenite is. mostly medium grained; that is, the crystals range in length from I to 5 mm. Sometimes, however, it is finer grained while again it becomes moderately coarse to even slightly porphyritic. More or less granu- lation of the rock is a very common feature, the feldspars showing the greatest effect of the crushing of the mineral grains. All the rock is foliated, most of it moderately so. At times the foliation is very faint, while at other times it is excessively devel- oped, especially along shear zones where the rock may have an almost schistose appearance. 1N, Y. State Mus. Bul. 115, p. 479-82. 1907. GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE 23 The normal syenite always contains quartz, the average amount being 12 to 20 per cent in the slides examined, and when it is greater than 20 per cent the rock is no longer regarded as normal, but rather granitic syenite to granite. Microperthite almost invariably makes up from one-third to two-thirds of the rock. Orthoclase is much less constantly present in variable amounts. Plagioclase (albite ' to andesine) never fails in amounts up to 35 per cent. When the rock is relatively rich in plagioclase it is a monzonite, though here, for convenience, classed with the normal syenite. Common horn- blende with yellowish green to dark green pleochroism usually occurs in variable quantities up to 25 per cent, while green mono- clinic pyroxene (usually diallage) frequently makes up 2 to 20 per cent of the rock. Enstatite was observed in only one slide. Both hornblende and pyroxene sometimes occur in the same rock. Magnetite (ilmenite), apatite and zircon in small quantities rarely fail. Biotite, garnet, zoisite and titanite are more sporadically present in small amounts. The following table will serve to show the mineralogical varia- tions of thin sections from carefully selected specimens of the normal syenite. 24 NEW YORK STATE MUSEUM “ISPlIq aye] SuoT JO JsvoyyOU oI ev FO JyTey-9uo0 ‘OV ‘ISpliq IYVYT Ssuoy Jo 4svoyynos ow ev jo JozIenb-suo “Sh ‘ou ‘quioodmMaN 0} peor oy} FO YMos soyim {1 aspa dem “ge SISpliq oY} FO Jsvoy}sJoU ow e FO JOJIeNb-ouo oye] Suoy Jo IJOYS Utojseo ‘Oh “OU faseI[IA Ie] SUOT FO JSaMYMOs soqyiut peor ‘Iv ‘ou ‘puod MOUUITT JO pUsa JsaA FO JsoM Sof YI VE “OU ‘yoofF OOVE apnyyye ye [ret] uleyuUNOU oN{_ 0} VsoOJD ‘IE ° ‘ou ‘Ou ZAI ou -oopo dew je ospii onjg jo ywuwns “VI ‘ou ‘puod susydoiS Fo YNOsS sopwu Z JAI Jepsd ‘EI ‘ou SUuTeJUNOW JotIeqio}zeE AA JO 4svo -Y}JIOU Soft S{I JOATI Jepoy ‘6 ‘ou foye] UeIpUy JO JsoM oSpod dew Iv9U peor ule ‘VY ‘OU SUTeJUNOW JolIeqiajJeA\ JO JseoyjzI0U ‘ayTUDAS 9} YM posse] sdUaTUDAUOD JOF o1e ‘SojTUOZUOW AT[eOT}OeId Ysnoyy ‘ov pue SP ‘gf “son JOAII Jepay uo ‘€ ‘oN SNe Wi oa 21931 NE ees sae ae LL ae cae eee ee & eoreevee z “ee eee oT hive POA core! oan co N ee ete 5 B 2. = ot @ @ ct oO —IIIlESESSS]S]S]SSSSS]lES>S>S]——SSS— Se —————————e TT a13411 z t Tt 1941 aTq4i aaa] oT oe eee Z4IeENGO HAN MHH Oris Origin Sel ve) » has! _ | oqIpoUse IN] | ¢ eoeeeeeote eee e g ¢ eee ereetloeevw eee ele eee Raabe eae tara en cea omets terete ¢ 3 Sle ears lhees i Atel ec Palomaillg. cB eecare 2 Sete cl Guake stats c seals years AU ae ca |, Dee sells Bee Sot onleehodulloate Eom = [toners coir foeor ies) to Sn aaa = a Wey ct © i) ae ae 09 ae © @ @ ct o epusquioyy Se Ohi SEO |, S110 81 ‘TO “102 “lO b a¥~IO Or "uvy-"1O ZI ‘1O-dV L 10 oI ‘IO“4V oI ‘IO 0d “UY-"JO OSE[OOISET SUT[OOIOIJAY a}y1usAS z}1Ienb [ewWIIOU JO suOoT}.9S-UINT, —E s[qe apy ed oly BSEIOYUO ‘ou PpeTy eoeeereee EI) 7/ Sb tee eS CCRC COCR 50) OECHORCR CCH TC 72 eae CeCe CCT ORC O31 Cs CBOsCrTOLOS hal O COOK ie Osa 5 eee ese eee eres eee eoceoee ere eee YaagWnAN AAVIS GEOLOGY OF THE BLUE MOUNTAIN QUADRANGLE 25 Basic (dioritic to gabbroic) facies of the syenite. The rocks included under this caption really have the composition of diorite or gabbro though they have been quite certainly produced either by pure differentiation of the syenite magma or by the assimilation of country rock through which the syenite magma was intruded. They are quite different in aspect from the typical later gabbros which are separately represented on the geologic map in that they show neither the diabasic texture nor the peculiar mottled appear- ance of these later gabbros. In fact the color, texture and structural features are essentially the same as those of the normal quartz syenite already described. Mineralogically, the basic facies of the syenite differ from the normal syenite chiefly by absence of microperthite, reduced amount or absence of orthoclase and quartz, and predominance of plagio- clase (oligoclase to andesine). The following tabular summary illustrates the mineralogical com- position of typical thin sections from several areas of the so-called basic syenite. Table 4— Thin-sections of basic (dioritic to gabbroic) phases of the syenite o © = | eg () Ww oe ae eet 8) ae | a | : : = oO ie rey ear) Sel ey eel eet ai) es eee S Omi aes a Sei Sees S| Sip er) seo ele B cm fe) A, peters Pe es ee 1 Ory Ral os < N Sty th6 23 gi ee ternal tet I RES ie Eat oF TS < _ 4 ee cea 30. as rpjel ata eal a Ola Galec ie) emetic ies G7 Siew ss Si eet ie little|, 3] little AA ae. I5b 3 8} OL.-An. 26] 35) 20 Re a Av|.