SEP 4 t95t . o- 1^ '■ ,Uol^ BOTAt'l N ew Y ork State Museum Bulletin Published by The University of the State of New York No. 297 ALBANY, N. Y. December 1934 NEW YORK STATE MUSEUM Charles C. Adams, Director GEOLOGY OF THE POTSDAM QUADRANGLE By John Calvin Reed Temporary Geologist, New York State Museum Conducted in cooperation with the Department of Geology, Princeton University CONTENTS PAGE Introduction 5 Geographic location 5 Topography 5 Culture 7 General geologic statement 8 Scope and purpose of the report . 8 Previous work 8 Acknowledgments 8 The Precambrian 9 General considerations 9 Quartzite 10 Grenville limestone 12 Mixed rocks 14 Gabbro 21 Granite 22 The Paleozoic 28 Potsdam sandstone 29 Theresa mixed beds 33 Heuvelton sandstone 35 Buck’s Bridge mixed beds 35 Ogdensburg dolomite 36 The Quaternary 36 Historical background 37 PAGE The Quaternary — {concluded) Glaciation of the Potsdam quadrangle 38 Structural geology 48 The Precambrian 48 The Paleozoic 55 The Post-Pleistocene 56 Resume of geologic history 56 The Precambrian 56 The Paleozoic 58 The Pleistocene 59 Economic geology 60 Water power 60 Talc 61 Limestone and dolomite 61 Granite 61 Iron ores. 62 Pyrite 62 Sandstones 63 Gravels 63 Bibliography 64 Index 97 ALBANY THE UNIVERSITY OF THE STATE OF NEW YORK 1934 M 207r-Je 32-3000 THE UNIVERSITY OF THE STATE OF NEW YORK Regents of the University With years when terms expire 1944 James Byrne B.A., LL.B., LL.D., Chancellor - New York 1943 Thomas J. Mangan M.A., LL.D., Nice Chancellor Binghamton 1945 William J. Wallin M.A., LL.D. ----- Yonkers 1935 William Bondy M.A., LL.B., Ph.D., D.C.L. - New York 1941 Robert W. Higbie M.A., LL.D. ----- Jamaica 1938 Roland B. Woodward M.A., LL.D. - - - - Rochester 1937 Mrs Herbert Lee Pratt L.H.D. ----- New York 1939 Wm Leland Thompson B.A., LL.D.- - - - Troy 1936 John Lord O’Brian B.A., LL.B., LL.D. - - Buffalo 1940 Grant C. Madill M.D., LL.D. ----- Ogdensburg 1942 George Hopkins Bond Ph.M., LL.B., LL.D. - Syracuse 1946 Owen D. Young B.A., LL.B., D.C.S., LL.D. - New York President of the University and Commissioner of Education Frank P. Graves Ph.D., Litt.D., L.H.D. , LL.D. Deputy Commissioner and Counsel Ernest E. Cole LL.B., Pd.D., LL.D. Assistant Commissioner for Higher Education PIarlan H. LIorner M.A., Pd.D., LL.D. Assistant Commissioner for Secondary Education George M. Wiley M.A., Pd.D., L.H.D., LL.D. Assistant Commissioner for Elementary Education J. Cayce Morrison M.A., Ph.D., LL.D. Assistant Commissioner for Vocational and Extension Education Lewis A. Wilson D.Sc. Assistant Commissioner for Finance Alfred D. Simpson M.A., Ph.D. Assistant Commissioner for Administration Lloyd L. Cheney B.A., Pd.D. Assistant Commissioner for Teacher Education and Certification Hermann Cooper M.A., Ph.D. Director of State Library James I. Wyer M.L.S., Pd.D. Director of Science and State Museum Charles C. Adams M.S., Ph.D., D.Sc. Directors of Divisions Archives and History, Alexander C. Flick M.A., Litt.D., Ph.D., LL.D. Attendance and Child Accounting, Charles L. Mosher Ph.M. Educational Research, Warren W. Coxe B.S., Ph.D. Examinations and Inspections, Avery W. Skinner B.A., Pd.D. Health and Physical Education, Law, Charles A. Brind jr B.A., LL.B. Idbrary Extension, Erank L. Tolman Ph.B., Pd.D. Motion Picture, Irwin Esmond Ph.B., LL.B. Professional Licensure, Charles B. Heisler B.A. Rehabilitation, Riley M. Little B.S., B.D. Rural Education, Ray P. Snyder School Buildings and Grounds, Joseph H. Hixson M.A. Visual Instruction, N ew Y ork State Museum Bulletin Published by The University of the State of New York No. 297 ALBANY, N. Y. December 1934 NEW YORK STATE MUSEUM Charles C. Adams, Director GEOLOGY OP THE POTSDAM QUADRANGLE By John Calvin Reed Temporary Geologist, New York State Museum Conducted in cooperation with the Department of Geology, Princeton University CONTENTS PAGE Introduction 5 Geographic location 5 Topography 5 Culture 7 General geologic statement 8 Scope and purpose of the report . 8 Previous work 8 Acknowledgments 8 The Precambrian 9 General considerations 9 Quartzite 10 Grenville limestone 12 Mixed rocks 14 Gabbro 21 Granite 22 The Paleozoic 28 Potsdam sandstone 29 Theresa mixed beds 33 Heuvelton sandstone 35 Buck’s Bridge mixed beds 35 Ogdensburg dolomite 36 The Quaternary 36 Historical background 37 PAGE The Quaternary^ — {concluded) Glaciation of the Potsdam quadrangle 38 Structural geology 48 The Precambrian 48 The Paleozoic 55 The Post-Pleistocene 56 Resume of geologic history 56 The Precambrian 56 The Paleozoic 58 The Pleistocene 59 Economic geology 60 Water power 60 Talc 61 Limestone and dolomite 61 Granite 61 Iron ores 62 Pyrite 62 Sandstones 63 Gravels 63 Bibliography 64 Index 97 ALBANY THE UNIVERSITY OF THE STATE OF NEW YORK 1934 Digitized by the Internet Archive in 2017 with funding from IMLS LG-70-15-0138-15 https://archive.org/details/newyorkstatemuse2971newy ILLUSTRATIONS PAGE Figure i Key map showing location of Potsdam quadrangle 6 Figure 2 Profile through the highest and lowest points in the Potsdam quadrangle (A-A' on map i) 9 Figure 3 Profile from point where the Raquette river leaves the quad- rangle, through Potsdam village, to southern boundary of quadrangle (B-B' on map i) 9 Figure 4 Sketch of p5rroxenite-amphibolite in garnet gneiss, on western edge of quadrangle 19 Figure 5 Sketch of pegmatite in granite gneiss 51 Figure 6 Sketch of pyroxenite-amphibolite and pegmatite in garnet gneiss. 54 Figure 7 Structure section along C-C' on map i 57 Figure 8 Structure section along D-D' on map i 57 Figure 9 View across St Lawrence valley from White’s hill, showing level skyline of the Tertiary peneplain 67 Figure 10 View of Tertiary peneplain, from north end of the West Parish- ville syncline 67 Figure ii View southwest toward Allen’s falls 69 Figure 12 Outcrop of white quartzite a mile east of High Flats 69 Figure 13 Photomicrograph of quartzite from near Allen’s falls 70 Figure 14 Outcrop of quartzite above Allen’s falls 70 Figure 15 Exposure of quartz schist near Claflin School 71 Figure 16 Outcrop of crumpled quartz schist a mile and a half east of Colton 71 Figtne 17 Crumpled quartz schist a mile south of Brown’s School 72 Figure 18 Gren'^e limestone a mile and a quarter northeast of Brown’s School 73 Figure 19 Photomicrograph of limestone from locality shown in figure 18 . . 73 Figure 20 Photomicrograph of pyroxenite along Raquette river, a mile be- low Rainbow falls 74 Figure 21 Outcrop of pyroxene gneiss a mile and a quarter northwest of Colton 74 Figure 22 Typical outcrop of pyroxene-bearing mixed gneiss, north of &uth Colton 75 Figure 23 Photomicrograph of amphibolite 75 Figure 24 Photomicrograph of garnet gneiss from near West Parishville. . 76 Figure 25 Photomicrograph of typical pyroxenite-amphibolite from West Parishville 76 Figure 26 Exposure showing amphibolite-pyroxenite, cut by pegmatite; halfway between Parishville Center and Stafford Comers .... 77 Figure 27 Inclusion of pyroxenite-amphibolite in garnet gneiss, near Brown’s Bridge 77 Figure 28 Garnet gneiss outcrop southwest of Brown’s Bridge 78 Figure 29 Exposure of garnet gneiss near Pierrepont, on western border of the quadrangle 78 Figure 30 Photomicrograph of granite from southeast of High Flats 79 Figure 31 Photomicrograph of granite from halfway between Colton and Brown’s School 79 Figure 32 Photomicrograph of tourmaline-bearing granite from a mile north of South Colton 80 Figure 33 Photomicrograph of granite from north of Gain Twist falls. ... 80 Figure 34 Contorted amphibolite in granite near South Colton 81 Figure 35 Granite outcrop a half mile northwest of South Colton 81 Figure 36 View up the Raquette river from bridge at Gain Twist falls. ... 82 Figure 37 View along the Raquette river near southeast comer of quad- rangle, showing coarse-grained granite 82 Figure 38 Exposure below Whitaker dam on the St Regis river, showing unconformities 83 Figure 39 Photomicrograph of Potsdam sandstone from the quarries below Hannawa Falls 83 [3] 4 NEW YORK STATE MUSEUM PAGE Figure 40 Quarry face in Potsdam sandstone below the power house at Hanna wa Falls •■••••• 84 Figure 41 A boulder of Potsdam conglomerate near West Panshville 84 Figure 42 A partially flooded old quarry in white Potsdam sandstone, above Whitaker dam 85 Figure 43 Cross-bedding in typical outcrop of red Potsdam sandstone a mile below Fort Jackson (Nicholville quadrangle) along the East branch of St Regis river 85 Figure 44 Apparent unconformity in white Potsdam sandstone in the bed ( of a small stream halfway between Hopkinton and Fort Jack- son 86 Figure 45 Another view in same locality as figure 44, showing apparent unconformity of the beds 86 Figure 46 Looking southwest at exposure of the Theresa formation in a small quarry between Sanford ville and Potsdam 87 Figure 47 View northeast along outcrop of Heuvelton sandstone in the bed of Plum brook three miles southeast of Norwood 87 Figure 48 Looking northeast along valley strewn with boulders of Heuvelton sandstone 88 Figure 49 View north at outcrop of pink granite gneiss projecting through sand terrace a quarter mile west of John’s pond 88 Figure 50 View southeast from a point one mile and a half south of Parish- ville Center, showing the sandy shore of Lake Iroquois 89 Figure 51 Wind-blown sand on surface of the delta built by the East branch of St Regis river in the Gilbert gulf 89 Figure 52 View northwest from near High Flats at Lake Iroquois beach terrace 90 Figure 53 Drifted sand in same locality as shown in figure 52 90 Figure 54 View southeast from a point one mile southeast of Buckton, showing front of the Gilbert gulf delta 91 Figure 55 Looking north from a point one mile west of Parishville at level top of the sandy hook built by St Regis river in Lake Iroquois. 91 Figure 56 Minor fold in garnet gneiss three miles east of Hanna wa Falls . . 93 Figure 57 An inclusion of pyroxenite-amphibolite in garnet gneiss 93 Figure 58 Front view of Potsdam State Normal School, constructed of buff Potsdam sandstone 94 Figure 59 A mausoleum near Potsdam, constructed of red Potsdam sand- stone 95 Figure 60 Potsdam Catholic Church, built of red Potsdam sandstone 95 Map I Geologic map of the Potsdam quadrangle In pocket Map 2 Glacial map of the Potsdam quadrangle In pocket GEOLOGY OF THE POTSDAM QUADRANGLE By John Calvin Reex> Temporary Geologist, New York State Museum INTRODUCTION GEOGRAPHIC LOCATION The Potsdam quadrangle lies in northern New York between f 44° 30' and 44° 45' north latitude, and 74° 45' and 75° west longi- , tude. The quadrangle is somewhat northeast of the geographic ' center of St Lawrence county. Its area is approximately 216 square i miles (see map i and figure i). Physiographically the quadrangle may be divided into two distinct parts of nearly equal area. The dividing line is meandering but distinct. It runs roughly from the western border of the quad- rangle at latitude 44° 35' to the eastern border at latitude 44° 40'. The northern half belongs in the St Lawrence valley province as defined by Fenneman (’17), whereas the southern half is part of the Adirondack highland, lying on the northwestern flank of that province. TOPOGRAPHY Elevations within the quadrangle range from 315 feet above sea level where Trout brook flows across the northern border into the Massena quadrangle to 1560 feet at the hilltop three-quarters of a mile south of Lily Pad pond, near the southeast corner of the area. Three important rivers of the northwest Adirondacks traverse the quadrangle on their way to the St Lawrence a few miles to the north. The largest of these is the Raquette, which flows within the quadrangle for more than 25 miles. The next largest is the West branch of the St Regis. This flows for nearly 20 miles through the area. The West branch of the St Regis is roughly paralleled by the East branch, which crosses the northeast part for a little more than four miles. The two streams last mentioned join a short distance to the north in the Massena quadrangle. All three rivers leave the area at about the same elevation, 330 feet. A distinct topographic break occurs at the contact between the two physiographic provinces. [5] 6 NEW YORK STATE MUSEUM The surface of the northern half of the region is irregular but the differences in elevation are seldom over too feet. There are a few fiat areas, such as the plain northeast of Potsdam village. Much of this division is poorly drained, and swampy areas are common. Few rock exposures occur. The surface of the southern half is much more rugged, swamps are fewer although by no means absent, streams are swifter and good exposures are common. Figure i Key map showing location of Potsdam quadrangle The presence of three possible peneplains is indicated in the region. The oldest is a somewhat distorted pre-Potsdam surface, which passes beneath the present surface north of the main physio- graphic boundary. This surface is now marked only by a few monadnocks, which project above the general surface of the country. A sloping Cretaceous peneplain is also present and is represented chiefly in the southern half of the quadrangle. Merging with the Cretaceous surface a still younger Tertiary peneplain floors the GEOLOGY OF THE POTSDAM QUADRANGLE 7 St Lawrence valley. These surfaces have been diagrammatically shown in section in .figures 2 and 3. Striking views of the valley province to the north may be obtained from the hills in the southern part of the quadrangle. Two such views are reproduced in figures 9 and 10. More detailed descriptions of certain topographic features are given at various places throughout the report in the discussion of various geologic phenomena. CULTURE Potsdam is the principal town of the area, with a population approximately of 4000. It lies about five and a half miles south of the northwest corner of the quadrangle on the Raquette river. Other towns are Norwood, Hannawa Falls, Colton, South Colton, West Stockholm and Parishville. The last two are on the west branch of the St Regis river. All the rest are on the Raquette river. The quadrangle is traversed by a network of roads, several of them trunk highways. The main highways all go through the village of Potsdam. Forty miles to the northeast lies Malone. Sixty miles due north is Ottawa. To the west and southwest are Canton, Ogdensburg, Gouverneur and Watertown. Two routes may be fol- lowed from Potsdam to the interior of the mountains. During the summer months most of the side roads are in good condition. The bridge at Gain Twist falls is impassable. The road down the river from there on the north side is abandoned as far as the mouth of Dead creek. The road north from the bridge past what was once Perkins School to the fork, the right- hand fork as far as Clear pond, and the left-hand fork as far as Dead creek are all abandoned. Therefore the southeastern part of the quadrangle, except the narrow strip along the road running east from South Colton, is relatively inaccessible. The principal industry is dairying. General farming is somewhat less important. Lumbering formerly was of great importance, especially in the southern more rugged half of the quadrangle, but this industry has now dwindled practically to nothing. Water power resources are developed to a high degree; they will be mentioned later under economic geology. 8 New YORK STATE MUSEUM GENERAL GEOLOGIC STATEMENT Nearly coincident with the physiographic boundary between the mountain and valley provinces is the geologic boundary between the Cambrian and Precambrian rocks. Thus roughly one half of the quadrangle, — the northern half — ^probably is underlain by Paleozoic rocks, and the other half by Precambrian rocks. Over both divisions the Pleistocene deposits form a more or less continuous concealing blanket. This cover is much more continuous in the northern half. SCOPE AND PURPOSE OF THE REPORT The field work of the writer was done during the summer of 1929 with one week’s work in the summer of 1928. The major thesis was the study, the mapping, and the interpretation of the Precambrian rocks, but an attempt was also made to cover, in as complete a manner as possible in the limited time available, the Paleozoic areas, and also to study the Pleistocene phenomena. PREVIOUS WORK For a comprehensive summary of the work done on the Adiron- dack Precambrian formations up to about 1916 the reader is referred to the introduction to New York State Museum Bulletin 185 by Martin (’16). Since then work has been done on the Precambrian of the northwest region by Agar, Ailing, Buddington, Cushing, Dale, Miller and others. The work of Chadwick, Cushing and Winchell was found to be of special aid in the study of the Paleozoic geology of the Pots- dam quadrangle. Of great assistance in the study of the Pleistocene phenomena were the writings of Fairchild and Taylor. Specific papers will be referred to in the body of the report and in addition a bibliography will be found at the end. ACKNOWLEDGMENTS The writer wishes gratefully to acknowledge the constant help of Professor A. F. Buddington both in the field and in the laboratory. Acknowledgment is also made of the assistance of Professor B. F. Howell, who spent several days in the field with the writer while work was being done on the Paleozoic rocks and who helped with that part of the report. The criticisms and suggestions of Professor LEGEND Figure 3 Profile through the highest and lowest points in the Potsdam quadrangle (A-A' on Map i). The profile is extended north through the Massena cjuadrangle to the Canadian border and south through a corner of the SUrk quadrangle and the Oiild- vvold quadrangle to the southern boundary of the latter. Some of the more prominent elevations within a zone five miles wide on cither side of the line of the section have been projected to the plane of the profile. The presence of three possible peneplains is indicated Figure 3 Profile from the point where the Raquette river leaves the quadrangle, through Potsdam village, to the southern boundary of the quadrangle (B-B' on Map i), The positions of the three peneplains are indicated J V 1^) J •jl siflotS ■- !>iitT?i»l yiiji (fjiit'.j’ijf! i^tvrn iJ jr '(i.x'JKibfMip Mi>// v;i" v> T'triJi'i botf.jitwu t>' t^v' \ ■ !, 'V j''-' ■ • ' III, •;:.' v’,‘ i, ■* ' ' '■> " ■’■ lice «u*i » 1 '■ '.i-x : ;.* of tfv'.' :’. rtVm'.'W,:* . fikt ■-,» :- hatno^ n Vup l). :x $!Xrk iJ*; witlssft "t Mn *c ll jm!« iiiisiy»i)>w{ ■{ nil-inT. . , . . , .inif Mtnift lilt 90l.'lltI4 -Hfj fltlAI bnifOiS '■ Riatt{3(llMI 3UU9'JI4Hi') - • - wit Bini j-jntu m*li*(o'f-»i’f , . j«ii itikb'KiU S'j/irn £ rf-MJt J ;ilsw Ittlutniiwiu^ I'JS.! DOtK. irfflifpa d'iii* ; ' ; siftVr iiai mY "' *' ( -'irrJUl. i , :v IfTwhtKP. "Vfit GEOLOGY OF THE POTSDAM QUADRANGLE 9 Paul MacClintock on the Pleistocene part of the report were invaluable. Financial aid was obtained from the department of geology of Princeton University by the use of a fund under the supervision of Professor A. H. Phillips. THE PRECAMBRIAN GENERAL CONSIDERATIONS The area of Precambrian rocks in the Potsdam quadrangle, as previously stated, can in general be considered as the area lying south of the distinct topographic and physiographic boundary that crosses the quadrangle in a northeast-southwest direction. Thus, a difference is immediately- noticed between the Potsdam and the Canton quadrangles for, in the latter, a part of the Precambrian terrane descends and becomes part of the St Lawrence valley floor. The boundary farther east is probably even more distinct than in the Potsdam quadrangle. The Nicholville quadrangle, the next one to the east, has never been studied geologically in detail, but the work of Cushing (’99) suggests a very pronounced topographic break at the northern boundary of the Precambrian gneisses. Farther to the west and southwest the Precambrian rocks extend still farther out across the valley floor. As pointed out by Cushing and reiterated by Chadwick (’19), a folded series of weaker Precambrian metasediments appears inter- calated with the massive granite gneisses at nearly the same place where the Precambrian begins to encroach upon the valley province. A few inkers of Precambrian rock were found out in the valley. More such inkers are no doubt present but are concealed by the cover of glacial deposits. The belt predominantly of metasediments that flanks the Adiron- dacks on the west gives way rather abruptly to the east to areas in which massive granite gneisses predominate. This change is well displayed in the Potsdam quadrangle and a basis is thereby provided for a broad twofold division of the Precambrian rocks. The line of division between the area of metasediments on the northwest and the granite gneisses on the southeast may be defined as beginning about a half mile north of the southwest corner of the quadrangle ; thence describing a crude arc concave to the west so that it touches the western boundary west of Claflin School ; thence in an easterly direction through the vicinity of Claflin School and Mud pond to the southwestern end of Hawk ledge; thence describing a sharp lO NEW YORK STATE MUSEUM promontory pointing west ; and finally turning to the north near Close pond and disappearing under the morainic blanket two and a half miles southwest of Parishville between that village and Parish- ville Center. In a very general statement six Precambrian lithologic units can be recognized — quartzite, limestone, mixed rock originally calcareous, mixed rock originally noncalcareous, gabbro and granite. The sedi- ments are generally accepted as being of Grenville age and the igneous material is post-Grenville. The above units and their varia- tions will be discussed in the following pages in more detail. QUARTZITE A narrow band of quartzite occurs in the valley of the west branch of the St Regis river in the vicinity of Allen’s falls. Out- crops are numerous in the constricted valley but are entirely lacking on either side. Quartzite forms the face of Allen’s falls. A view of the face of Allen’s falls is shown in figure ii. The rock extends for nearly a mile upstream from the falls. Just above the bridge the strike is nearly parallel to the flow of the river as is shown in figure 14. The dip is steep to the northwest. The strike swings around near the southern end of the area to approximately N. 60° E. The only other considerable area of quartzite is in the valley of Alder Meadow brook beginning about two miles upstream from the mouth of the brook and extending upstream for at least a mile and a half. As in the last described locality, the dips are con- sistently steep to the northwest while the strike is quite uniform averaging about N. 35° E. At some places in this area thin inter- bedded bands of pyritous and of calcareous strata appear. The quartzites of the Allen’s Falls and Alder Meadow Brook localities are very similar and they may be part of the same forma- tion. Field observations, however, were unable to make their con- tinuous mapping possible. A thin curving strip of white quartzite circles the southwestern part of the hill a mile east of High Flats. It actually outcrops for only a few hundred yards. About 60 feet is exposed. Immediately above it stratigraphically (if the beds are not overturned) and in contrast with it is about 40 feet of quartz schist. Figure 12 is a view of the white quartzite. Near the southwest corner of the quadrangle a long narrow band of quartz schist borders the eastern nose of the sigmoidal flexure described by Martin (’16). GEOLOGY OF THE POTSDAM QUADRANGLE II Two other minor occurrences of quartz schist may be mentioned: an east-west trending area beginning a mile east of Colton, and a small patch three-quarters of a mile east of Brown’s School on the south side of the road. Thus it is seen that only a few widely separated occurrences of quartzite were found in the area. It is not possible with the meager data at hand to correlate them as one formation. In general it may be stated that the quartzite appears to occur at or near the base of the Grenville limestone. Study of the map shows that the quartzites and quartz schists are typically found near the previously mentioned line of division of the Precambrian rocks. The term “quartzite” has been used loosely to include, along with typical Precambrian quartzite, rocks between that and crystalline limestone or its alteration products. The two extremes will be described. The typical quartzite is a fine-grained gray or brownish rock with a vitreous luster on its fracture surface. It breaks with difficulty into sharp angular fragments. The fracturing is often controlled by several sets of intersecting planes, probably the result of weaknesses induced by structural stresses. The quartzite occurs in strata which range in thickness between the limits of two inches and two feet. Many of the outcrops show the beds curved and bent, but the occurrence of the quartzite in scattered outcrops may indicate that it yields to great stresses by breaking apart. The incipient joints combined with the bedding cause much of the rock to weather into flat parallel- faced polyhedra from one to several feet across and usually a few inches thick. In thin section the rock appears to be pulverized and is so fine grained that microscopic study is difficult. The crushed material, essentially quartz, contains crystals of microcline and albite which do not show strain shadows. Very small amounts of apatite and magnetite are present. A photomicrograph of a thin section of the quartzite from just above the bridge at Allen’s falls is shown in figure 13. The other extreme has been described by Martin (’16, p. 22-23) as “quartz mesh limestone.” He says: “The quartz mesh limestone is a rock made up, in its typical development, of quartz and calcite in nearly equal proportions. The two minerals are distributed in such a manner that the quartz forms a complex system of irregulary forking and anastomosing lines, and the calcite occupies the inter- vening detached areas,” The quartz mesh limestone, he says, grades into quartz schist as follows : “the quartz becomes increasingly abundant, the meshes flatter and more elongated, while at the same 12 NEW YORK STATE MUSEUM time the limestone filling gradually disappears, till a thin-bedded.- often highly crumpled, quartz schist is developed.” In figures 15, 16 and 17 are shown typical outcrops of quartz schist. The change from quartz schist to quartzite is abrupt, at least in the locality where the two were observed in actual contact. At the occurrence a mile east of Colton the quartz schist is made up, not of quartz and calcite, but of quartz and tremolite. The writer interprets the quartz schist and the quartz in the limestone in the same manner as Martin, as “recrystallized clastic material originally present in the limestone.” GRENVILLE LIMESTONE The largest and most continuous mass of limestone in the quad- rangle can be traced from the vicinity of High Flats southwestward to the valley of O’Malley brook, down which it swings to some- what beyond the mouth of that brook in the Raquette river. It is likely that the western limb extends continuously northward down the Raquette toward Hanna wa Falls and Stafford Corners, but tracing is interrupted by the mask of glacial deposits. In fact, the writer observed a small area of limestone a mile and a half east and a little south of Hannawa Falls and another a mile west of Brown’s Bridge. These areas are probably parts of the main mass. Similarly, the eastern limb probably continues northward toward Parishville Center. It is reasonable to suppose that the limestone belt completes the circle, in which case the two ends must meet somewhere in the upper reaches of Garfield brook. Unfortunately this critical area lies in the concealed zone. The eastern limb of the limestone area is broad and is interrupted by a complicated system of granite sills so that the limestone is found as an irregular network of narrow strips lying to the east of the main band. The limestone that extends southeastward from High Flats up the upper course of Parkhurst brook seems to terminate abruptly against granite. On the evidence of one outcrop of Grenville limestone a little southeast of the place where Leonard brook leaves the quadrangle the writer believes the valley of the brook in that vicinity to be of limestone. The topography lends credence to that interpretation. Probably it extends farther up the brook’s valley than is shown on the map. GEOLOGY OF THE POTSDAM QUADRANGLE I3 A ribbon of limestone occurs between the gabbro of the eastern end of the Pierrepont sigmoid and the quartzite band already men- tioned as bordering that sigmoid. A small infold of crystalline limestone highly impregnated with mica and feldspar lies to the east of the main road between Colton and South Colton and about two miles from the latter village. Finally, limestone occurs on the east side of the road two miles south of Pickettville. This area may be of considerable size. Its boundaries could not be well traced. It may extend farther to the east and south. The last two limestone areas are the only two which were found within the Precambrian division of predominately granite gneiss. It is difficult to decide just what limits to observe in terming a rock Grenville limestone. Pure crystalline marble grades on the one hand through quartz mesh limestone into quartz schist, as already indicated, and on the other into a variety of mixed gneisses by the action of igneous injection and metamorphism. “Limestone” will be used to include only those rocks in which calcite is conspicuous. The purest phase of the limestone is a coarsely crystalline white marble containing only a very small percentage of other minerals. Impurities, however, are seldom lacking and are commonly phlogopite, tremolite, graphite, serpentine, chondrodite, diopside, biotite, feld- spar and quartz. Figure i8 is a view of a typical outcrop of the limestone. Figure 19 is a photomicrograph of a thin section from a serpentinous concentration from the same locality. The impurities are due partly to a recrystallization of original material within the limestone and partly to the introduction of material from external sources. Thus patches of silicious, biotitic or rusty gneisses are found in the limestone areas and mark, no doubt, originally impure layers. Occasionally a band of garnet gneiss occurs intercalated in the limestone. In some places the introduction of material by hot waters has converted the marble to diopsidic or tremolitic varieties. Again serpentinous limestone (ophicalcite) is developed. Siliceous phases of the limestone occur in which calcite is less prominent than coarsely crystalline feldspar and quartz. The thorough recrystallization of the limestone usually renders! strike and dip observations impossible, except where structure is emphasized by the segregation of impurities into bands, or where strata of other rocks are included. Moreover, such observations even when they are obtainable may not be significant because the plastic nature of the limestone has induced profound contortions. 14 NEW YORK STATE iftUSEUM MIXED ROCKS The various types of rocks that have resulted from the action of post-Grenville intrusives on rocks of the thick Grenville series will be considered here. It must be borne in mind that the resultant mixed rocks, in some cases, grade into the granite gneiss so imper- ceptibly that it is impossible to draw a definite dividing line between granite and mixed rock. This is particularly true of the rocks that the writer interprets as having been formed by the action of the intrusives on originally calcareous beds. In other cases the contact between mixed and intrusive rock is quite definite and can be placed with considerable assurance. It is also difficult in many cases to draw accurately a dividing line between the mixed Grenville and the simple recrystallized Grenville rocks. These difficulties are consistent with the gradational nature of the changes. Two outstanding subdivisions of the mixed rocks become apparent after consideration of some of the field phenomena. These are : (i) the rocks which the writer interprets as having been formed by the action of an intrusive on, and its interaction with, Grenville sediments originally calcareous in nature and (2) the rocks which the writer interprets as having been formed from originally aluminous Grenville strata, namely, garnet gneiss. To the two divisions might be added a third — those rocks formed by the addition of material to very silicious Grenville beds (quartzites, quartz schists, etc.) ; but the additive changes in these cases are so minor, relatively speak- ing, that no third division has been made and the rocks have been described with the Grenville formations. The mixed rocks interpreted as derived from calcareous beds will be discussed first. The various gneisses and schists of this division are practically confined to the main group of Precambrian rocks that lies to the northwest of the main granite area. A few inkers, some of considerable size, are found infolded well within the granite masses whose surfaces occupy the southeastern part of the quad- rangle. A superficial cover of glacial debris and alluvium conceals some of the areas that are probably underlain by mixed rock. Thus some of the apparently detached patches of mixed rock probably are continuous beneath the cover. The writer has mapped a narrow strip of mixed gneiss around Claflin School near the southwest corner of the quadrangle and has continued it in a westerly direction from that vicinity. This was GEOLOGY OF THE POTSDAM QUADRANGLE 15 done on the evidence of a few outcrops of rusty gneiss along the brow of the hill forming the south wall of the valley of Leonard brook. It probably flanks the northern edge of the granite mass just to the south. The valley of Leonard brook for the most part is concealed. The village of Colton lies in an area of mixed gneiss, which may be traced nearly continuously (except for the valley of Leonard brook) around the ovate granite area occupying the region west and a little south of the village. Northward from Colton there is a series of good exposures down the river for a little more than a mile. Next comes another concealed area, with exposures beyond in limestone. The boundary between the ovate Colton granite area and the mixed rock on its north and northwest sides is arbitrary. The change is gradational. The map shows the mixed rock area swinging northward toward the cross roads a mile southwest of Brown’s Bridge. What is presumed to be a part of the same area is picked up again on the east side of the Raquette river southeast of Colton. Its southern boundary is first found on the east side of the river near the power house at the narrow chute just northeast of Mud pond. From there it runs slightly north of east toward Hawk ledge. The writer believes that the mixed gneisses may occupy the low land at the foot of the southern end of Hawk ledge and thus pass into the valley of Dead creek. This distribution could not be proven because of the absence of outcrops in the critical region, but the swampy valley of Dead creek may be occupied by either limestone or mixed gneiss. The northern boundary of the area of mixed gneiss runs a little north of east from Colton, passes just south of Brown’s School and then, curving a little more to the north, becomes lost in the maze of small granite sills a mile and a half north of Close pond. It is thus seen that on the south and east the mixed gneiss is bounded by granite; on the north and northwest it is bounded by concealed areas, quartzite, limestone and smaller granite areas. A smaller rather indefinite area of mixed gneiss extends north- ward from High Flats between two patches of granite gneiss about a half mile apart. The small patch of mixed rock along the road a mile and a half east of Parishville Center is probably on the northward extension of the last-named belt. i6 NEW YORK STATE MUSEUM The Other areas of mixed gneiss that are found in the main granite region are all comparatively small. Notable are those at the following localities: (i) two miles approximately north of Parish- ville, (2) just to the east of the inlier south of Pickettville, (3) at the top of White’s hill, (4) just north of Clear pond, and (5) north of South Colton. Throughout the mixed rock areas pegmatite dikes are common, some cutting and some paralleling the foliation. In width they range from paper thinness to more than 40 feet. The feldspar is usually white. The mixed gneisses are so varied and so complex as practically to defy detailed description in any reasonable space. Therefore a few of the main types will be briefly discussed. Complete grada- tions occur between the various outstanding types. Pyroxenite. Two kinds of pyroxenite, one light, and one dark, occur in the quadrangle. The rocks are apparently similar to those described by Smyth and Buddington (’26, p. 14), in the Lake Bona- parte quadrangle. The light-colored pyroxenite consists in its best development of an interlocking mass of white or light greenish gray prismatic diop- side crystals. Narrow bands of glassy quartz frequently occur. The rock is medium to coarse grained; many diopside crystals attain a length of half an inch. Pyrite is usually present as disseminated crystals from very small size up to more than an inch across. The appearance of this rock under the microscope is shown in figure 20. Good outcrops of this gneiss were found a mile downstream from Colton in the bed of the river, on the south side of the valley of O’Malley brook a little more than a mile west of Brown’s School, and still farther up O’Malley brook about three-quarters of a mile north of Close pond. The darker pyroxenite is a crumbly granular mass of green pyroxene crystals in association usually with biotite and pyrite. It is also medium to coarse grained and typically weathers to rusty color, because of the pyrite. Exposures of this type occur along the Paquette river in the gorge about half-way between Colton and Brown’s Bridge and in the region southwest of Brown’s School. In the latter section it is often closely associated with quartz mesh limestone. A good outcrop of the green pyroxenite occurs in the south bank of the Paquette river about two miles above the mouth of Hargus brook. This is far within the main granite mass. The writer believes that such rocks may be formed by the trans- fusion of ferromagnesian material from a magmatic source into limestone, as has been pointed out by Adams and Barlow (’10). GEOLOGY OF THE POTSDAM QUADRANGLE 17 Pyroxene-bearing gneisses. Rather dark-colored, medium to coarse-grained, pyroxene-bearing gneisses form a common type which come under this general class of mixed rocks. Rather typical out- crops are shown in figures 21 and 22. The writer interprets these gneisses as mixed rocks with an unusually large percentage of granitic material in the mix. In constitution they are very different at different localities, but they may be characterized by their granitic tendencies and the presence of considerable pyroxene. The typical pyroxene-bearing gneiss is medium grained, distinctly gneissic and often highly contorted. Many of the weathered out- crops are dark brown or black. Under the microscope the major minerals are seen to be quartz, microcline, albite and pyroxene. Rarely orthoclase is conspicuous. The pyroxene is usually bright green and is probably related to hedenbergite. The common accessories are titanite, apatite, garnet, pyrite and magnetite. Green hornblende is often present and at least some of it is the alteration product of pyroxene. Rarely a few patches of calcite are present, very rarely a little scapolite. Pyroxene-bearing gneisses are especially well developed in the region northwest of Colton. Pyritous gneisses. All of the mixed rocks carry more or less pyrite. Certain strata, however, are relatively so rich in the sulphide that they are termed pyritous gneisses. The very pyritous layers are usually quite thin. The writer observed none more than 20 feet thick. They occur at various horizons throughout the Grenville rocks, but the relations are so obscure that no definite positions could be assigned to them. They weather easily to a buff, brown or black gossan and this, together with their crumbly rotten appearance, makes them readily recognizable. The bands are often highly and complexly folded. The writer believes that the pyritous gneisses are “primarily of sedimentary origin.” This is the view held by Martin (T6, p. 46). All of the occurrences of this rock were too small to be mapped on the scale used. They occur near the eastern boundary of the garnet gneiss area southwest of Brown’s Bridge, near the western border of the quadrangle west of Colton, in the gorge between Colton and Brown’s Bridge, and in the valley of the Raquette river a little over a mile below Rainbow falls. Biotite gneiss. The occurrence of biotite in the Grenville mixed gneisses of calcareous origin is not particularly common. Locally, however, biotite is developed in places to such an extent that it becomes one of the major constituents, thus forming a biotite gneiss i8 NEW YORK STATE MUSEUM or schist. In the outcrop the rock usually weathers to a rusty color, but the fresh specimen is black with bright biotite flakes. The occurrence of biotite gneiss is patchy, and attempts to map it met with no success. Apparently it grades inconspicuously into other mixed gneisses, often into those rich in amphibole. A thin section of this rock is made up of quartz, orthoclase, albite, microcline and biotite. Apatite is the chief accessory. The rock is strained and some of the boundaries of the quartz areas have a lacelike appearance. No crushing was observed. Amphibole-bearing gneiss. A few outcrops of black splintery amphibolite occur. Mixed rocks carrying hornblende are quite common. These sometimes grade, as stated above, through amphi- bole-biotite gneisses into biotite rich varieties. In several typical thin sections of amphibole-biotite gneiss pyroxene was entirely wanting. In many of the pyroxene-bearing gneisses much horn- blende of clearly secondary nature may be observed, but the writer believes that most of the amphibole of the amphibolites is not an alteration product of pyroxene. Microscopically, the rock is seen to be uncrushed but sometimes strained. Its chief constituents are quartz, feldspar and hornblende. Common accessories are apatite and magnetite. The biotite content is extremely variable. A photomicrograph of the amphibolite is shown in figure 23. The amphibole-bearing gneisses typically occur near or at the contact of granite masses and rocks of Grenville affiliation. The impression that they are contact rocks is unavoidable even though they could not be traced as contact bands for any great distance. Mixed rocks derived from aluminous strata. The formational term “garnet gneiss’’ is used in this paper in a rather loose sense, simply because the presence of conspicuous numbers of garnets in many outcrops of the rock make the term applicable for field pur- poses. In reality it includes much rock that is not particularly rich in garnets, but always, when so used, the association with the garnet- bearing gneiss is unquestionable. The type rock of the formation is a distinctly banded gneiss. The average thickness of the bands is between two inches and one foot. The weathered surface shows contrasting bands of gray with those that are nearly white. Against this light background the red or pink garnets show up conspicuously. Individual garnet crystals more than an inch in diameter are seldom seen. Quarter-inch ones are numerous. In some favored localities crystals with good faces may be found, but as a rule the crystals are rounded. When freshly GEOLOGY OF THE POTSDAM QUADRANGLE 19 fractured the rock has a much darker appearance and the garnets are not so conspicuous. The white bands are due to numerous injections of pegmatitic material that is medium to coarse in grain. The garnets are some- what more common in the pegmatite layers than in the intervening gray weathering layers. The rock is probably a true injection gneiss. The layers between the pegmatite bands consist of quartz and feldspar (usually acid plagioclase and orthoclase) with pyroxene, biotite laths and irregular patches of garnet. The common minor accessories are pyrite, magnetite, apatite and titanite. A typical thin section is reproduced in figure 24. In some places the pegmatite injections are few or wanting. Here the rock may have fewer garnets and become in reality a feldspar- biotite gneiss. Contrarily the percentage of garnets may increase so that the principal mineral is red garnet with minor amounts of feldspar and the usual accessories. , The banding in the highly garnetiferous gneiss is often emphasized by alternating layers rela-' tively richer and poorer in garnets. One of the features of the garnet gneiss is its constant associa- tion with bands, blunt lenses and fragments of dark pyroxenic amphibolite (see figure 4). This rock stands out in striking contrast to the lighter garnet gneiss. Thin sections show the rock to be essentially composed of pyrox- ene, hornblende and feldspar. The feldspars often have a com- Figure 4 Sketch of pyroxenite-amphibolite in garnet gneiss. Exposure is in circular area of garnet gneiss on western edge of the quadrangle, ne^r Brown’s Bridge 20 NEW YORK STATE MUSEUM position near that of andesine, but albite also occurs. The acces- sories magnetite and apatite, are common. Occasionally biotite is present. Some of the amphibole appears to be replacing the pyroxene. Rarely garnet occurs. Figure 25 shows the appearance of the pyroxenic amphibolite in thin section. In some areas the volumetric percentage of the pyroxenic amphi- bolite is so great that the associated garnet gneiss forms only narrow dividing bands around the darker masses. In fact, considering the total area of garnet gneiss exposed in the quadrangle, the writer does not believe it an exaggeration to estimate that a third of it is pyroxenic amphibolite. The pyroxenic amphibolite is usually cut by pegmatite dikes and stringers and by quartz veins. Frequently these are parallel to the foliation (figure 26). The dark rock may be found in masses only a few inches across, in bands an inch or two thick ; or the masses may be several hundred feet or more in diameter, and bluntly lenticular (figures 27 and 28). All gradations between the two extremes are found. Small sills of granite have been found in the garnet gneiss areas. Only two important areas of garnet gneiss occur in the quad- rangle. The larger of these is roughly a north-south trending elliptical area with a long dimension of about five miles and a short one of about a mile and a half. Its northern boundary is along the road between Stafford Corners and Parishville Center. It extends southward to the valley of O’Malley brook. The southern end is encircled by the limestone valley area already described. The other large area of garnet gneiss lies partly in the Potsdam and partly in the Canton quadrangles. It bounds on the northwest the mixed rock area lying northwest of the Colton phacolith and is bounded on the east by the valley of Tracy brook. The area is nearly round with a diameter of approximately two and a half miles. A typical exposure in this area is shown in figure 29. A small outcrop of garnet gneiss occurs south of the southeastern part of the large elliptical area and separated from the main mass by a belt of limestone. Another occurs a mile south of High Flats on the east side of the road. It is possible that these two outcrops are parts of a continuous band, but it is impossible to prove such an hypothesis. They occur at about the same horizon in the lime- stone. The associated rocks of the garnet gneiss areas have reacted very differently to distortive force. The garnet gneiss itself has responded in a plastic manner, perhaps owing to its intimate injection by hot GEOLOGY OF THE POTSDAM QUADRANGLE 21 pegmatitic material, and is commonly found with the bands highly contorted. On the other hand, the pyroxenic amphibolite lenses and bands are often cracked, broken and disrupted, and the inter- vening spaces are filled with pegmatite. The capacity of even the pyroxenic amphibolite to yield plastically under certain conditions is well demonstrated by the intricate folds in many outcrops. Never- theless, the contrast between the relative plasticities of the two rocks is impressive. The garnet gneiss is believed to be the representative of an aluminous Grenville formation which has been subjected to intense regional metamorphism and has been injected with and soaked in pegmatitic juices. The small outcrops of garnet gneiss mentioned as occuring in the limestone are interpreted by the writer as being formed from originally argillaceous beds in the limestone. The evidence concerning the origin of the associated pyroxenic amphibolite is confusing. Two possibilities are considered here. It may be gabbro that was intruded into the garnet gneiss as con- cordant lenses before the folding of the region. It may be the result of metamorphism of calcareous beds within the garnet gneiss formation. The writer believes that there is more evidence in favor of the latter origin. It is difficult to understand why gabbro intrusions should be practically confined to the garnet gneiss formation. The size of many of the patches of dark rock is small. It does not appear likely that a gabbro intrusion into a slate or shale would split up into so many bodies of various sizes, the smaller ones to be measured in inches. The long narrow dark bands appear more like intercalated beds. Disruption of many of the bands by subsequent forces and the healing of the breaks by pegmatite and the more plastic garnet rock is postulated to explain the small broken layers and lenses. This action must have occurred no matter what the origin of the pyroxenic amphibolite may have been. GABBRO The occurrence of intrusive masses of gabbro is well known in the belt of Grenville metasediments along the northwestern and western flank of the Adirondacks. Its age has been definitely fixed as the earliest of the Precambrian intrusives. It is therefore surprising that this rock has only a very minor development in the Potsdam quadrangle. The difficulty of distinguishing between the intrusive gabbro and some of the mixed rocks is always present and the writer well realizes that further investigations may show 22 NEW YORK STATE MUSEUM that some of the types assigned to the latter group in reality may be gabbro. The difficulty is that converging lines of metamorphism have rendered rocks of widely different origin nearly identical. By far the greatest amount of this rock of doubtful origin is found in the garnet gneiss masses, and the writer has already men- tioned in the paragraphs dealing with that formation that he believes the pyroxenic amphibolite to be of sedimentary derivation. Martin (T6) writing on the Canton quadrangle devotes much space to the description of a large body of gabbro-amphibolite form- ing part of the great sigmoidal flexure near the southeast corner of his quadrangle. The eastern end of the sigmoid cuts into the Potsdam quadrangle and the nose is formed of gabbro. This is the only occurrence that the writer has mapped as such in the Potsdam quadrangle. If the Canton quadrangle had not been mapped and described so well by Martin it is probable that this area of basic rock would have been mapped as the pyroxenic amphibolite so commonly associated with garnet gneiss in the Potsdam quadrangle. In thin section the rock appears to be slightly crushed with mosaics of smaller grains around the larger ones. Pyroxene, feld- spar, hornblende, and sometimes quartz are the major constituents. Biotite is common as an accessory as are magnetite in small grains, apatite, and sometimes titanite. Irregular and forking pegmatite dikes of various sizes are common. GRANITE The granite of the Potsdam quadrangle occupies a far larger area than all the rest of the Precambrian rocks combined. In fact, it forms the bed rock of at least a third of the entire quadrangle. Its limits have been delineated previously while describing the areas occupied by the other Precambrian rocks. The occurrences of granite gneiss as inkers in the valley province has also been men- tioned. The small sills and irregular areas of granite are too many and too complex to locate in detail. In fact, the scale of the map prohibits the individual mapping of a great many of the smaller masses. Conspicuous as is the granite design on the map, it repre- sents but an insignificant fraction of an infinitely larger mass occupy- ing great areas in the quadrangles to the southwest, the south, the southeast and the east of the Potsdam quadrangle. The large granite areas form the rougher, wooded, more thinly settled parts of the quadrangle and these are therefore much more inaccessible. For this reason and because of the difficulty of locating GEOLOGY OF THE POTSDAM QUADRANGLE 23 oneself accurately these areas could not be covered in so much detail as the rest of the region. The observations are confined to traverses along roads, trails and streams with some isolated ones in the intervening areas. The granites have been tentatively subdivided into three groups. These will be discussed in what the writer believes to be the correct chronological order of their intrusion. It was not possible with the data collected to plot definite contacts between the three sub- divisions, but clearly there are at least three and possibly four distinct types. Medium-grained granite gneiss. The medium-grained granite gneiss composes at least nine-tenths of the total granite. It makes up the main granite area except for a small part in the south, which is cut off on the south and east by the borders of the quadrangle and is bordered on the north by a contact which the writer found difficult to locate exactly and which may be gradational but which probably enters the quadrangle southwest of South Colton, runs through that village to the vicinity of Rainbow falls, and leaves the quadrangle about a mile north of the southeast corner. The northern boundary of the medium-grained granite is the same as the boundary, already mentioned, between the main granite areas and the areas of metasedirnents (see pages 9 and 10). Most of the smaller masses of granite in the Grenville formations probably also belong in this class except the Colton mass. For reasons that will be taken up later in the part of this report dealing with structure, the medium-grained granite gneiss is believed by the writer to be the oldest in the quadrangle. It is also the most variable, but field relations indicate that rocks of widely diver- gent aspect should be included in this class. Brief descriptions of a few of the more typical types from widely separated localities will be given below. I In the region a mile and a half south of Converse, where the granite first appears through the glacial drift of the valley province, the rock is a pink to gray, medium-grained, distinctly banded, granite gneiss. The color is of course caused by the pink or salmon-colored feldspar. The banding is not much distorted but is often fairly straight for several hundred feet. Magnetite is a common accessory and helps to emphasize the banding as it is sometimes more con- centrated in certain layers. A few distinct veins of magnetite, several inches in width and continuing for several feet along the strike, were noticed. 24 NEW YORK STATE MUSEUM Microscopically, the rock is composed principally of quartz, micro- cline and albite. Magnetite is conspicuous. Titanite is very common as is leucoxene. Apatite and chlorite are both present. The texture is that of normal crystallization. Practically no crushing of the com- ponent grains has occurred, but strain shadows especially in the major minerals are very common. 2 At Parishville the granite is a pink, very gneissic, highly con- torted rock. The banding is emphasized by layers and stringers of dark mineral of variable thickness. The dark strips are probably amphibolite. Pegmatitic material is common and occurs as flattened lenses parallel to the foliation and a few inches to a few feet in thickness which normally pinch out longitudinally within a short distance. Laterally they appear to grade rather sharply into the finer grained granite. The granite itself appears to be made up of quartz, pink feldspar and amphibole. 3 The typical Catherineville Hill granite is white or light pink, is medium grained, and contains considerable hornblende as its ferromagnesian constituent. The rock is usually somewhat con- torted so that dip and strike observations are difficult. The gneissic character is shown by layers relatively rich in hornblende. In thin sections the rock is observed to be totally uncrushed and to be made up of quartz, albite, microcline and orthoclase. The common accessories are hornblende, titanite and apatite. 4 An average granite of a locality a mile and a half east of High Flats may be described as follows. It is rather fine-grained, pink granite gneiss, which has the appearance of a crushed rock. It con- tains very little dark mineral. The rock is not contorted, but the narrow bands have a comparatively uniform strike. The microscope reveals a rock with a texture that approaches protoclastic-cataclastic. Most of the mass of the rock is pulverized while some quartz areas and some feldspar is granulated. Very little dark mineral is present and the constituents are quartz, albite and microcline. 5 The mass of White’s hill is made up for the most part of a pink to gray, fine to medium-grained granite. It is usually distinctly gneissic, but some outcrops appear massive. A conspicuous feature is the occurrence of contorted stringers, lenses and irregular patches of pegmatitic material which define the banding. The color is due to pink feldspar. 6 The rock in the region about a mile and a half north of the southeast corner of the quadrangle is a greenish gray, medium- GEOLOGY OF THE POTSDAM QUADRANGLE 25 grained gneiss. The dark minerals are segregated in irregular strips surrounding small masses of quartz and feldspar. The feldspar has a waxy appearance. Magnetite is observable in the hand specimen. Under the microscope the quartz is seen to be squeezed out into long narrow leaves. The ground mass is slightly granulated. This is a weak development of protoclastic texture. The chief minerals are quartz, microperthite, albite and hornblende. Pyroxene is present in conspicuous amounts and apatite is a common accessory. The percentage of dark minerals is unusually high, probably due to some contamination with Grenville material. 7 Another common type is that seen in Hawk ledge. This rock is a distinctly banded pink to salmon-colored granite gneiss of medium grain. It is not so contorted as is the White’s Hill type; in fact, the strike is nearly straight for long distances. The banding appears to be due to layers relatively rich in dark minerals alternating with layers made up of an interlocking mass of quartz and pink feldspar. The above rock is entirely uncrushed and is composed of quartz, microperthite and albite, with a minor amount of orthoclase. The principal dark mineral is biotite. Some magnetite is also usually present. 8 The rock of the granite mass southeast of High Flats is rather distinctive. It is dark greenish gray in color and is distinctly por- phyritic. The ground mass is made up of quartz and a waxy greenish feldspar along with considerable ferromagnesian material. The phenocrysts are of the waxy feldspar. The rock has a distinct protoclastic texture. Quartz appears in the granulated ground mass and in flattened leaves. Albite also occurs in the ground mass and in larger crystals. The largest crystals are of microperthite. The common dark minerals are hornblende, biotite and pyroxene, along with a little apatite and magnetite. 9 The granite of the sill-like southwestern end of Hawk ledge that juts into the mixed rock area towards Colton is medium to fine grained. It carries very little dark mineral and is relatively high in quartz. The microscope shows it to have a texture that may be termed advanced protoclastic. Quartz, albite and microcline are the major minerals. The quartz occurs typically in leaves which are some- times granulated around the edges. Pyrite, zircon, apatite, titanite and biotite are present as accessories. 10 The region northwest of South Colton is typified by a medium to coarse-grained, banded granite gneiss with a pink or gray color. 26 NEW YORK STATE MUSEUM Layers composed of quartz and feldspar and speckled with small crystals of dark minerals are separated by thin irregular amphibole rich strips. Figure 35 shows a typical exposure of this rock. Quartz, orthoclase, microcline and albite are the major constituents. Some microperthite is present. The chief accessory is hornblende, but apatite, biotite, magnetite and pyrite are all present. Strain shadows are very common in the quartz and feldspar of this rock, but it is not crushed. II The rock in the vicinity of John’s pond is a pink granite gneiss with an extremely variable foliation. It is usually rather fine grained. Pegmatite dikes and segregations are common in it. Some are parallel to the foliation, some cut it, and some are very irregular. The pegmatite carries numerous nests of black tourma- line, biotite, and sometimes muscovite. Tourmaline is also seen in quartz segregations in the granite. The microscope shows the rock to be uncrushed. The main mass is composed of quartz and microperthite. Biotite, tourmaline and muscovite are all present. The above descriptions will serve to show the general character ; and the wide variations in the medium-grained granite gneiss type. ^ In figures 30 to 33, inclusive, are photomicrographs of some of the types. Much of its variation is believed to be the result of different tectonic conditions that existed in various parts of the mass during and following its consolidation; and to the variable amounts of Grenville material of different character that were included, recrystallized, assimilated and digested. The main mass is batholithic in character, but as far as is known its boundaries are nearly always concordant with neighboring Gren- ville formations. The region surrounding the West Parishville syn- cline and between that structure and the main granite mass is full of granite sills of all sizes. These are found even north of the syncline where most of the bed rock is concealed. The structural features will be taken up more fully in the paragraphs on structure. In many places over the granite areas occur strips and patches of gneiss of suspected Grenville affiliation. In some places the granite may be seen in the act of breaking up, twisting, kneading, splitting and assimilating such gneiss. Figure 34 shows one such occurrence. The larger inkers of mapable size have already been mentioned under mixed rocks. Coarse-grained granite gneiss. The typical coarse-grained granite is found only in the southern part of the quadrangle. No actual contact between it and the medium-grained granite to the GEOLOGV OF THE POTSDAM QUADRANGLE 27 north was seen and, therefore, it is not known whether the contact is gradational or sharp. In age it is believed to be later than the medium-grained rock because it is never crushed and is extremely coarse grained. Individual crystals an inch or two across are com- mon. In many respects it is similar to the medium-grained granite but it forms a lithologic unit that is very easily recognized. It is quite uniform in nature and only rarely displays medium-grained facies. Grenville gneiss inclusions are notably lacking in this rock and only one of mapable size was found, that just south of Gain Twist falls. Typically the rock is distinctly gneissic and is formed dominantly of salmon-pink or white feldspar crystals showing bright cleavage surfaces. Glassy quartz occurs irregularly between and through the feldspar areas and in flattened lenses an inch or two long and a quarter of an inch across. The dark minerals are not conspicuous and are confined more or less to the quartz areas or to borders between quartz and feldspar. The rock is often cut into massive blocks by several intersecting sets of joints. Microscopically, quartz, albite, microperthite and orthoclase are seen to be the chief constituents. The dark mineral is principally ' hornblende although sometimes magnetite is present. The rock is I totally uncrushed. f Around the mixed rock mass south of pain Twist falls the granite is somewhat finer grained and green pyroxene becomes the principal dark mineral. Figures 36 and 37 show the typical appearance of outcrops of the coarse granite. Younger granite. The main representative of this group is the rock of the Colton phacolith. How many of the granite sills in ; the mixed rock areas belong under this heading is not known, but [I it is believed that some of them probably do. The rock of the phacolith is fine to coarse in grain but never so 1 coarse as the real coarse granite. It is usually pink in color. Peg- I matite dikes are common both parallel to and across the distinct foliation and these often carry black tourmaline, biotite and j magnetite. Thin sections show the rock to be principally composed of quartz, microcline and albite. Rarely microperthite is a major constituent. The common accessories are hornblende, spinel and chlorite. Several crystals of a feldspar more calcic than albite were seen. Strain I shadows are very common, but practically no crushing is seen. The quartz areas often show peculiar lacelike borders. 28 NEW YORK STATE MUSEUM THE PALEOZOIC The Paleozoic areas were not studied in the field in any great detail because of the scarcity of outcrops and because the major thesis of the work was the study and interpretation of the Precambrian. It was found to be impossible to draw definite contacts delimiting the areas occupied by the various formations. G. H. Chadwick’s report (’20) on The Paleozoic Rocks of the Canton Quadrangle was found to be invaluable as a guide and was used constantly. Only that portion of the quadrangle lying north of a line drawn between Potsdam and the northeast corner of the area is known to be underlain by rocks of Paleozoic age. It is probable that a strip approximately five miles wide lying south of the mentioned line is also underlain nearly continuously by Paleozoic rocks, but the con- cealing drift cover makes it impossible with the data at hand to be certain of this. The other possibilities for this strip will be discussed later. Five Paleozoic formations are recognized in the quadrangle ranging in age from Middle Cambrian (?) to Lower Ordovician (Upper Beekmantown). These are: the Potsdam sandstone, the Theresa mixed beds, the Heuvelton white sandstone, the Buck’s Bridge mixed beds and the Ogdensburg dolomite. Of the above the Potsdam and the Theresa formations and prob- ably the Heuvelton are Cambrian, while the Buck’s Bridge and Ogdensburg formations belong in the Ordovician. The beds in general are very little disturbed. The dips are usually around 2 or 3 degrees, but in places much greater dips are noted up to 10 degrees. The beds of at least the lower part of the Pots- dam seem disturbed to a far greater degree than the above state- ment would indicate. This is mostly due to cross-bedding. Although the presence of long, nearly parallel axes of gentle folding is practically certain, there appears to be superimposed on that type of structure numerous small, gentle domes and basins. The general dip of the beds is to the north at an angle slightly greater than the slope of the surface, for a traverse from south to north encounters successively higher and higher beds. It is to be emphasized that the outcrops are so few and the transi- tional formations between the Potsdam sandstone and the Ogdens- burg dolomite are so similar that it is impossible within the limits of the quadrangle to draft a map that is accurate even in a very general way. GEOLOGY OF THE POTSDAM QUADRANGLE 29 POTSDAM SANDSTONE At two places the actual contact of the Potsdam sandstone with the Precambrian rocks was found and at a third the contact could not have been more than a few feet away. Most of the observable unconformities on the northwestern flank of the Adirondacks between the Precambrian rocks and the Pots- dam sandstone are between Grenville limestone and the sandstone. The two unconformities actually seen and about to be described were unusual in that the first was between quartzite and Potsdam con- glomerate and the second between granite gneiss and Potsdam con- glomerate. I At Allen’s falls the river plunges down a steep chute about 40 feet high (figure ii). Nearly the whole flow of the river is, at times, carried by a penstock around this point so that the bed and banks of the stream are readily accessible. The scarp over which the river normally falls and the walls of the gorge above are composed of a steeply dipping (strike N. 30° E., dip 45° N. W.) Precambrian quartzite. The walls of the small amphitheater just below the falls and the walls of the gorge from there downstream together with the bed of the river below the falls are composed of rocks of Potsdam age. At the base of the falls and for a hundred yards downstream the river bed is composed of a very interesting boulder conglomerate. Some of the boulders are two or three feet in diameter and are set in a red sandy matrix. The boulders are irregular and somewhat rounded in shape. It was found possible in many cases to pry a boulder from its setting. Many of them showed striations. These had no system of orientation, but definite striations were found only on the upper surfaces, thus making it impossible to be certain that they had not been striated recently, although the writer believes this to be unlikely. The boulders and pebbles are made up of three kinds of rock: quartz, weathered granite and banded red sandstone. The weathered granite boulders appear to be identical with the weathered granite later described. The quartz pebbles are rounded and coated with hematite. The quartz itself is glassy or milky. The sandstone boulders and pebbles are banded in various shades of red, purple, and white, sometimes with white blotches. They are to all appear- ances composed of the same material as the matrix, which is essen- tially a dark red arkosic sand. There can be no doubt that these are actually boulders and pebbles, for they may be easily pried from 30 NEW YORK STATE MUSEUM their matrix and, as stated, are coated with a film of hematite. The bedding planes within the boulders also are discordant with the nearly horizontal attitude of the planes in the matrix. The presence of the boulders and pebbles proves that the rock is not the earliest Cambrian rock of this region. The fact that the conglomerate is found at the base of the scarp of Precambrian quartzite shows that the sea either laved the base of a steep cliff or lay in a long narrow trough of Precambrian rocks. In the latter case, which the writer believes more likely, the present gorge below the falls is a reexcavated Precambrian gorge with only a smear of Potsdam on the walls and floor, and the scarp itself is a reexposed Precambrian scarp. The actual unconformity may be found along the walls just below the falls and close to the river’s edge. It is not knifelike in sharp- ness but slightly gradational and ill defined. In all, about 40 feet of the Potsdam is exposed. The upper part of the section is the typical red Potsdam. 2 A mile upstream from the road crossing at Allen’s falls and a few hundred yards below Whitaker dam (marked “Whitaker Falls” on the topographic map) the second observation of the Precambrian- Potsdam unconformity was made. Here the Precambrian rock is pink granite gneiss. The change in character of the river bed is striking. Upstream through a shallow gorge where the river riffles over ledges of granite gneiss, and the bed is strewn with boulders of the granite, a low scarp made by a ledge of granite crossing the stream is mounted and immediately above, the stream bed flattens and is floored by a smooth stratum of grayish sandstone. The walls of the valley are formed by low vertical cliffs of red sandstone 15 or 20 feet high. Qoser inspection reveals that even below the granite scarp part of the side walls of the valley are composed of the sand- stone. The individual beds range from three or four inches to several feet in thickness. From the first layer of sandstone in the river bed up nearly to the dam the valley is floored by sandstone intermittently covered with gravel and boulders. The beds cross the stream in successively higher and higher steps so that close inspection of clean sections is made possible. At one place a layer three feet thick is made up of gray sandstone with numerous little white quartz pebbles averaging a half inch in diameter. The sandstone has been folded slightly, several anticlines and synclines being visible over the exposure with their axes striking approximately N. 25° W. GEOLOGY OF THE POTSDAM QUADRANGLE 31 Just below the dam another ledge of granite crosses the river and cuts off the sandstone beds, in fact, the dam itself is built across the top of the ledge. It was on the west bank of the river half-way up the granite ledge that the best observation of the unconformity was made. The top four inches of the granite is weathered. The sandstone lies imme- diately on the sloping weathered granite and the contact is knifelike in its definiteness. Boulders of the weathered granite are found several feet up in the sandstone together with quartz boulders both rounded and angular. An interesting exposure occurs just below the dam on the east bank (figure 38). Here the sandstone is seen lying on the granite. The stratum is but three or four feet thick and is overlain by a sec- tion of Pleistocene gravels several feet thick. , 3 A few hundred yards southeast of High Flats on the north side of the road is an outcrop, several thousand square feet in area, of Potsdam sandstone, which, although not seen in actual contact with the Grenville limestone of the vicinity, must be very close to it. The rock is a white vitreous quartzite and all edges are rounded and gleam with a saccharoidal luster. Red blotches and stains are noticeable through the white sandstone. A quarter of a mile south of the outcrop of hard white sandstone is another patch of typical red sandstone somewhat larger than the first. This too must lie very near to the Precambrian floor. The outcrops of Potsdam sandstone were so few and scattered that the writer did not think it advisable to map a band of Potsdam continuously across the quadrangle. The other outcrops that are not known to be so close to the Pre- cambrian basement will now be described. A short distance below the village of Hannawa Falls on the Raquette river is the site of the famous old Potsdam sandstone quarries. They are flooded now because of the dam at Potsdam, five miles downstream, but much of interest is still to be observed. The only rock in the vicinity is the typical red banded sandstone. A photomicrograph of a slide cut from this rock is shown in figure 39. Across the western face of the main quarry the sloping trace of an apparent plane of unconformity within the sandstone is plainly visible, as shown in figure 40. Further search shows another plane to the south nearly at the water’s edge and still a third is seen on the north side of the quarry. The dips of the beds above and below the planes are in some places nearly at right angles to each other. The planes are themselves 32 NEW YORK STATE MUSEUM widely divergent in strike and dip. In spite of the gigantic scale the writer believes that the phenomena displayed are all due to cross- bedding. Within the sections included between the above mentioned major planes cross-bedding on a more usual scale is conspicuous. A few fossil worm trails were collected from this quarry. Chadwick (’20, p. 43) believes these quarries to be in fossil sand dunes and this conception is very tenable. The old quarry a mile above Hannawa Falls on the west bank is now flooded and no outcrop can be found there. A few slabs of sandstone very similar to the rock last described were found on the banks of the river. Boulders of Potsdam conglomerate were found a quarter of a mile north of West Parishville on the east side of the road. They are probably close to their parent ledge. The rock is extremely conglomeratic and is composed essentially of white quartz pebbles cemented with a very red matrix (figure 41). A half mile south of Whitaker dam on the west side of the river just where the small run west of the mouth of Alder Meadow brook flows into the river is a small quarry in Potsdam sandstone, from which material has been taken for road construction. The quarry face exposes about a 15-foot section, as seen in figure 42. The rock is a white sugary sandstone which crumbles easily. Cross-bedding is present but is not at all conspicuous. Careful search revealed no fossils. The attitude of the beds is nearly hori- zontal. A hummocky glacial till blanket overlies the sandstone in this vicinity and conceals any other exposures, but local concentra- tions of sandstone at neighboring localities bear witness to the under- lying rock. Just above the dam several piles of red sandstone project above the water. These must have been removed from outcrop during the excavating for the dam foundation. The phenomena displayed below the dam have already been described. No other exposure of Potsdam sandstone was seen by the writer, but just east of the eastern border in the Nicholville quadrangle excellent outcrops were observed in the neighborhood of Fort Jack- son. A fine section is exposed along the stream that crosses the road half-way between Hopkinton and Fort Jackson. A few hun- dred feet below the bridge is an apparent unconformity, which was photographed and is reproduced as figures 44 and 45. In addition to the plane of apparent unconformity shown in the photographs several other similar planes with widely divergent strikes and dips are present both upstream and downstream from the locality. Again, the writer GEOLOGY OF THE POTSDAM QUADRANGLE 33 believes that the phenomena displayed are due to cross-bedding, on a : gigantic scale. The rock at this locality is a white or yellowish sac- charoidal sandstone. Downstream from the bridge at Fort Jackson, on both sides of the river for a distance of more than a mile, occur almost continuous outcrops of banded red sandstone cross-bedded to an extreme degree but not on the gigantic scale of the Hannawa Falls and Fort Jackson occurrences (figure 43). The attitude appears to be nearly hori- zontal. THERESA MIXED BEDS Northwest of the series of Potsdam sandstone areas just dis- cussed comes the concealed zone, already mentioned, in which there are no outcrops at all. North of this zone, that is, north of Pots- dam, West Stockholm and Buckton are a few outcrops. All of the outcrops in the quadrangle north of the concealed zone are of rocks of more recent date than the Potsdam with one excep- tion, that is a granite outcrop in Potsdam village. Thus the contact between the Potsdam sandstone and the overlying formation, the Theresa, is not exposed within the quadrangle. The total thickness of the Potsdam plus the Theresa can be approximated, but with the available data it is impossible to make even a guess as to how thick either of the components may be. Just ofif the western border of the map and a mile below Potsdam at Sissonville along the Raquette river, Chadwick describes out- crops of Heuvelton white sandstone and in the small road metal quarry at nearly the same locality he recognizes the contact between the Theresa and the Heuvelton. The author found difficulty in placing the contact with knife-edge accuracy at this locality, but he believes it to be essentially correct. ■ Large boulders of what the writer regards as Theresa were found at the northern corner of the Potsdam village line. The small quarry on the northwest side of the road between Pots- dam and Sanfordville and a quarter of a mile toward Sanford- ville from the point where the road crosses the Potsdam-Stockholm township line is in the Theresa formation (figure 46). Lithology was used in placing the rock of this quarry in the Theresa. The fossils were of no value, although several poorly preserved gastro- pods were collected along with one doubtful cephalapod. Just below the bridge at West Stockholm and also a quarter of a mile downstream on the west side 'are good outcrops of sandy Theresa. From the first-mentioned locality, just below the bridge, was collected the largest gastropod found in the quadrangle. Ulrich 34 NEW YORK STATE MUSEUM believes that it may possibly be a representative of some species of ? Ophileta and that the beds from which it came belong above the Ozarkian. Field relations indicate that the beds are part of the Theresa and the writer has mapped them as such, but concealed structures could easily account for exposures of higher beds at this locality. It is to be noted that the three last mentioned outcrops all have anomalous southerly dips as follows : along the road between Pots- dam and Sanfordville, strike N. 70° E., dip low to S. ; below the bridge at West Stockholm, strike N. 85° E., dip 7° S.; and a quarter of a mile downstream from the last locality, strike N. 45° E., dip 12° S. A half mile up the river from the road crossing at West Stock- holm a small dam is built across the stream and here just below the dam is a poor weathered outcrop of a porous sandy dolomite which may be Theresa. The attitude, as nearly as the writer could determine, is about horizontal. The above are the only actual outcrops of the Theresa formation that the writer saw within the quadrangle. It is true that at several other localities groups of large flat boulders were found concentrated in localized areas, which strongl)”^ suggested that the bed rock of the area was Theresa. Two such localizations were as follows : at the road crossing over Trout brook a quarter of a mile south of Old Forge School, and on the west bank of the east branch of the St Regis river near the end of the bridge a half mile northeast of Buckton. The Theresa beds are usually bluish gray or buff in color, often weathering ashen or dark. They are very sandy with calcareous cement, which in many cases displays sand crystal cleavages. The bedding is thin to medium, averaging about a foot. The weathered surfaces are frequently pitted and are sometimes rotten because of the solution of the calcite cement. Chadwick (’20, p. 25) mentions that in the Canton quadrangle the Theresa formation is unfossiliferous except for tubular chocolate- colored stains whose organic origin is doubtful. At the West Stock- holm locality and at the the locality between Sanfordville and Potsdam, which have been mapped as Theresa, fossil remains were found. It does not seem possible to place the rocks of these localities in any bed higher than the Theresa because Heuvelton sandstone, whose identity is considered more certain, has been found north of the mentioned localities. It is therefore probable that the fossils are actually in the Theresa. GEOLOGY OF THE POTSDAM QUADRANGLE 35 HEUVELTON SANDSTONE The Theresa beds, according to Chadwick, pass upward into the Heuvelton beds without any stratagraphic break. No evidence of this change was found in the Potsdam quadrangle, nor was any found of the supposed disconformity between the Heuvelton and the overlying more calcareous Buck’s Bridge beds. Only two outcrops of the Heuvelton were found in the quad- rangle, and these in the same vicinity. The first is at the end of the road that runs northeast from the northern corner of the Pots- dam village line and the second is a quarter of a mile northwest of there in the bed of Plum brook (figure 47). The rock is a white vitreous sandstone with a silicious cement and is more resistant to weathering than the rocks of the forma- tions either above or below. It displays, at the localities mentioned, conspicuous ripple marks and has taken in places a fine glacial polish. The rock, in fact, resembles a quartzite. According to Chadwick, it is somewhat fossiliferous, revealing sparingly specimens of what may be, as suggested by Doctor Ulrich, Helicotoma uniangulata. The fucoidal structure mentioned by Chad- wick was not noticed and no fossils were found. In addition to the evidence of the outcrops in the Potsdam quad- I rangle and the ones just west of its borders at Sissonville and around ! Norwood, the distribution of the formation could be traced in places [ by means of the easily distinguished white blocks and boulders j' occuring in the drift presumably not far from the parent ledges. The formation is supposed to be about 20 feet thick and rather I uniform over large areas, but the meager data afforded no evidence as to thickness or distribution on a large scale. Cushing supposes I the formation to be a lentil in the Theresa, but Chadwick believes it to cap the Theresa, at least in the Canton quadrangle. BUCK’S BRIDGE MIXED BEDS I The Buck’s Bridge formation is very similar to the Theresa but is distinctly more calcareous than the Heuvelton. One of the principal differences between the Buck’s Bridge and the Theresa, according to Chadwick, is the lack of fossils in the latter, but if the fossils at the localities previously mentioned under the Theresa are actually in that formation this criterion is not reliable. Undoubt- edly, however, fossils are much more abundant in the Buck’s Bridge. The formation is essentially a brownish, sandy dolomite display- ing the characteristic sand crystal cleavage so prevalent in the beds 36 NEW YORK STATE MUSEUM between the Potsdam and the Beekmantown. Rounded masses of white calcite are frequently noticed. A collection of fossils (gastro- pods) was made at Chadwick’s locality, just above the Hewittville bridge. With the exception of the localities mentioned by Chadwick along the eastern border of the Canton quadrangle, just above the Hewitt- ville bridge, just below the Hewittville lower dam and at Norwood, only three outcrops have been mapped as being in the Buck’s Bridge. The first of these is on the east side of the Raquette river two miles south of Norwood and just south of the end of the first road (dotted on map) leading west from the main highway between Norwood and Union School. The second is a very poor outcrop beneath the mill just below the dam at Sanfordville. The third is just south of the house at the bend in the road a mile and a half northwest of West Stockholm. An outcrop of possible Buck’s Bridge occurs three-quarters of a mile nearly due west of the last- mentioned outcrop, at the southwestern end of the swamp. The attitude of the beds at the locality south of Norwood is nearly horizontal, as it is at the locality in the southwestern edge of the swamp just mentioned. The thickness exposed at the first locality is about two feet. At the locality northwest of West Stock- holm the strike is approximately N. 50° E. and the dip 7° N. At least ten feet is exposed here. OGDENSBURG DOLOMITE A three-foot section of undoubted Ogdensburg dolomite is exposed in a small old quarry on the southwestern side of the road about two miles northwest of Sanfordville. The rock is a fine-grained, drab-colored, velvety appearing dolomite similar to the outcrops at Yaleville north of Norwood in the Waddington quadrangle. These outcrops have been mentioned by Chadwick (’20, p. 37-8). Speci- mens of brachiopods and gastropods were collected. The beds appear to dip very slightly to the north. A thin stratum from Chadwick’s locality a mile west of Norwood along the Rutland railway tracks furnished gastropods identified by Doctor Ulrich as representing three species of Lecanospira and one Ophileta. THE QUATERNARY Only a small part of the time spent working on the Potsdam quadrangle could be devoted to the glacial phenomena. Some obser- vations were made, however, and these, with additional data from GEOLOGY OF THE POTSDAM QUADRANGLE 37 earHef reports, are the basis for the glacial map accompanying this' report. It is not to be understood that a searching study of the glaciation of the quadrangle has been made ; therefore further work would no doubt change considerably the aspect of the map. ’ ' HISTORICAL BACKGROUND It is highly probable that the northeastern United States has , undergone severe continental glaciation more than once during the Quaternary. Since no evidence of a previous glaciation was recog- nized by the writer, nor any reference to such evidence found relating to the Potsdam quadrangle or immediately adjacent district, this report is concerned only with the last great stage of the Pleistocene epoch — ^the Wisconsin. Early in Wisconsin time a continental ice sheet advanced from the Labrador center southward toward what is now the northeastern United States. The major physiographic features were probably similar at that time to those of the present. The advancing sheet, upon encountering the Adirondack highland, split and sent one lobe southwestwardly up the lowland now occupied by the St Lawrence valley and another along the depression of the Champlain and Hud- son valleys. Subsequently the encroaching ice overrode even the highest Adirondack peaks and the ice front proceeded southward until at its maximum extent it stood across northern New Jersey and Pennsylvania. The region occupied by all New York State was under the continental ice cap. With changing conditions the ice advance was halted and the melting away of the ice began from the region under consideration. It is possible that east and south of the Adirondacks a large part of the ice sheet became stagnant so that there was no oscillatory retreat of a definite ice front (Flint ’29, Cook ’24, p. 158). North of the Adirondacks (also, perhaps, in the area just mentioned) and westward it is probable that the dissipation of the ice took place by the melting back of the ice front faster than it could be moved* forward by pressure from the north. It is likely that the high Adirondacks were uncovered early in the history of the withdrawal of the ice Sheet and existed as a huge nunatak or a group of nunataks. In this area surrounded, or nearly surrounded, by ice, alpine glaciers may have existed. At certain times during, the retreat of the ice huge glacial lakes existed, ponded between, the ice front and outlying divides. Chief of these large glacial lakes in New York State was Lake Iroquois. 38 NEW YORK STATE MUSEUM While the ice covered northern New York the lake had its outlet through the Mohawk valley into the Hudson valley at the site of Albany. Later a lower point was uncovered at Covey hill in Quebec, north of the Adirondacks, and the waters drained into the northern Hudson valley. Still later the ice dam melted out of the mouth of the St Lawrence trough and this trough, which was lower than it is at the present time, was flooded by marine water, the Champlain- ian sea. The arm of the Champlainian sea that lay along the north- west flank of the Adirondacks is called the Gilbert gulf. Subsequently the land rose, was tilted up at the north, the sea retreated and conditions became as we now find them. GLACIATION OF THE POTSDAM QUADRANGLE The quadrangle falls easily and naturally into two main divisions of approximately equal area. The northern half is a district in which the topography is almost entirely controlled by glacial drift. The southern half is one in which bed rock is the principal control- ing factor with only a minor amount of modification by drift. The division between the two parts is irregular and, in places, indefinite. In general the dividing line is nearly coincident with the line between the two physiographic provinces of the quadrangle. The following discussion will be carried on as nearly as possible in chronological order from older to younger. Some of the features are essentially contemporaneous and in other cases the writer could not determine the relative ages with certainty. Division in which the topography is controlled by drift. Striae. The bed rock is exposed in only a few places in this division and consequently striae are very difficult to find. Three observations were made : 1 Along the east bank of the Raquette river at Hewittville (Can- ton quadrangle) a half mile west of the western boundary of the Potsdam quadrangle striae occur. They are just below the Hewitt- ville dam which is about a quarter of a mile upstream from the Hewittville public highway bridge. They are gouged out on a nearly horizontal bedding plane of a soft sandy dolomite. The exposed striated area is roughly a hundred feet square and some of the scratches extend all the way across. Their bearing is about S. 5° E. 2 Striae were found two and a half miles east and a mile and three-quarters south of Norwood on the east bank of Plum brook, the Heuvelton sandstone locality already mentioned (see page GEOLOGY OF THE POTSDAM QUADRANGLE 39 35). The rock here is a white vitreous sandstone dipping between seven and ten degrees to the north. The beveled edge of one of the layers about two feet thick has been given a beautiful glacial polish and is striated in the direction S. 7° E. In the immediate proximity of the striae were also found very good chatter marks and crescentic gouges. 3 This observation was in the small Theresa quarry on the north- west side of the concrete highway running from Potsdam through Sanfordville (see page 33). The rock is a sandy dolomite striated on a nearly horizontal bedding plane. The striae occur in an area about 20 feet by 3 feet and although not particularly well developed are quite distinct. Their direction is, as at the last men- tioned locality, S. 7° E. Ground moraine. Nearly all of the division of the quadrangle in which the topography is controlled by drift is covered by a continuous blanket of ground moraine. Its thickness in most places is not known. The relief of the till sheet is, in general, low. Some parts are hummocky and slightly rough while others are very flat as is well illustrated by a till plain lying immediately northeast of Potsdam village. As stated in the preceding paragraphs on striae, the outcrops are few. This is, of course, due to the concealing blanket of till. The outcrops that are found are either along the major stream courses where erosion has cut through to the bed rock, or where the cover has been stripped off to expose the rock for quarrying. Much, no doubt, could be learned about this till blanket, its vari- able thicknesses, the nature of its constituents and their distribution, the terrane on which it is deposited and other features by a collection and study of the well data in the area. This could not be attempted by the writer in the limited time available nor could boulder counts be made over the district. Incomplete sections of the till may be seen in some localities where streams have dissected the cover or in road cuts. The material has an unusually small amount of clay in it, owing no doubt, to the scarcity of shale in the rocks which were destroyed to form the till. The boulders and pebbles are chiefly of the underlying sandstones and dolomites with a minor amount of igneous or metamorphic rocks, which may have been transported considerable distances from the north or which may have had their origin in unseen Precambrian inkers below the till. The above statement is true in a general way, but there are locali- ties, as, for example, the hill top centering near the road intersection 40 NEW YORK STATE MUSEUM at elevation 451 feet and just one and three-quarter miles nearly due west of Sanfordville, where relatively greater numbers of Pre- cambrian boulders occur. It seems likely that the source of these .boulders is not far from where they are now found. The nature of the till is also somewhat variable; boulders more than two feet in diameter are rare in some localities but in others such boulders constitute a sizeable percentage of the till. The boulders of the underlying Paleozoic rocks are frequently flat and tabular parallel to the bedding planes, whereas the Precambrian ones are usually rounded. Near some of the outcrops that the writer observed, and notably in the immediate vicinity of the locality previously described as the place where the second observation of striae was made, also north- east, east and south of that locality, in the valley and lowland was found a great collection of large, rough, irregular blocks of the vitreous white sandstone which outcrops where the striae were found (figure 48). Obviously these boulders have not been transported more than a few score feet at the most from their parent ledge. The writer believes that such a collection of boulders indicates a thin drift blanket at that place and that the boulders themselves are the same as the underlying rock. Around the small quarry where the third observation of striae was made, just such a concentration of sandy gray dolomite was found, yet the rock would never have been seen in place had it not been for the quarry. Drumlins and drumloidal hills. In the northwestern part of the quadrangle is found a considerable group of drumlins and drum- loidal hills. These are easily distinguished on the topographic map and range in size from a few hundred feet in length and 10 or 20 feet in height to a mile or two in length and nearly 100 feet in height. Some are simple drumlins quite symmetrical in shape, others are compound, and still others are very irregular in form so that there may be some doubt as to their true drumloidal character. In many cases it is difficult to decide whether or not a hill should be mapped as a drumlin or simply as ground moraine. The direction of elongation of ovate hills varies, in general, from about S. 45° W. to S. 10° E. There are few whose axes do not lie within these limits. The more southerly trending ones lie in the area around and southwest of West Stockholm, this area being the eastern part of the drumlin belt. The hill lying along the road running northeast from the north corner of the Potsdam village line is elongated in the direction nearly S. 45° W. except at its southwestern extremity, where a small GEOLOGY OF THE POTSDAM QUADRANGLE 41 protuberance trends S. a few degrees E. This is interesting as it suggests the possibility of two generations of drumlins or a change of direction of ice movement during drumlin formation. Another noteworthy fact in this connection is the discordance in trends between the striae and the drumlins in the same localities. The few drumlins in the Potsdam quadrangle are only a small I part of a much larger system occupying neighboring quadrangles on I the west, north and northwest. I It is this great curving drumlin system that determines for the ' most part the direction of the major rivers in this district such as f the Grass, the Raquette and the St Regis, from the places where they debouch from the highlands onto the till sheet to their mouths I in the St Lawrence. This fact has been remarked by Chadwick (’20, p. 7). Small temporary lake bottoms. Scattered over the till sheet are more than a dozen irregularly shaped swamp areas. Some are very small; some are several square miles in extent. Some are totally undrained, while others are traversed by sluggish and intermittent, streams. The writer interprets these as being beds of temporary lakes, left in depressions in the till after the final dissipation of the ice. In some of the swamps deposits of a gray sticky clay were found. The partial desiccation of the lakes subsequent to the disappear- ance of the ice i^ assigned partly to land elevation, partly to the lack of water from glacier melting, and partly to a more arid climate. " Possible post-Paleozoic-pre-Pleistocene circumferential valley. A strip of country, in places more than five miles wide, in which no outcrops at all are found, traverses the quadrangle parallel to the I southern boundary of this division (region in which the topography |- is controlled by drift) and immediately north of the boundary, in j which are found no outcrops at all. This totally concealed zone, j since it extends westward into the Canton quadrangle, is mentioned by both Martin and Chadwick in their respective reports on the Canton quadrangle. The streams have a slightly steeper gradient through the concealed zone and one would expect outcrops in their beds. None are found; the natural inference is, therefore, that the till covering is thicker. A very feasible explanation is suggested by Fairchild, and Chad- wick indicates his support of it in his report on the Canton quad- rangle. It postulates that before the ice sheet covered the area a major river flowed here circumferential to the Adirondack high- 42 NEW YORK STATE MUSEUM lands and that the concealed zone is merely the drift-filled valley of that great river. Such circumferential drainage is quite common, as is witnessed by the Black Hills (South Dakota) drainage pattern, and indeed as is witnessed by the present drainage along the south- west border of the Adirondacks. Perhaps this postulated river cut clear through the Paleozoic series in places and exposed Precambrian rocks. This would pro- vide a source for the concentration of Precambrian boulders in the till that have been mentioned previously. Division in which the topography is controlled by bed rock. At the time of the ice advance this division of the quadrangle was higher and rougher than the division whose features have just been described. Its underlying rock is also much harder and more resistant. For these reasons a much thinner veneer of till is found in this half of the quadrangle, except in localities especially favor- able for collecting material and where the ice deposited unusual amounts of material. Much of the glacial debris from the higher, steeper areas also has been removed by erosion. The special features of this division will now be discussed. Striae. More observations of striae were possible here because much more bed rock is exposed. Only six were recorded. These are, however, at widely separated points. Search would, no doubt, reveal many more. A glance at the map will show that they are quite consistent among themselves and with the one^in the northern division of the quadrangle. Their moderate divergence is readily explained by the rough topography. The best striae were found on a slightly tilted, beautifully polished, light-colored gneiss surface in the ditch on the west side of the road in the angle at elevation ten hundred and seventy-eight, about two and a half miles west of South Colton. Patches of till. Over the Precambrian surface were found many small to moderately large patches of gravelly till which were too small to map individually and which were unclassified except as above. Eskers. In the valley of Leonard brook and crossing the road running between Colton and Claflin School is a sharply defined elongate ridge that the writer interprets as being an esker. The ridge extends, with interruptions, for about a mile. If it was once a continuous ridge, erosion has dissected it considerably ; perhaps it never was continuous. The component parts can be picked out on the topographic map. Its average height is not far from 30 GEOLOGY OF THE POTSDAM QUADRANGLE 43 feet; its constituent material is gravelly with many boulders six or eight inches through. No fresh section was seen. Another similar ridge occurs a half mile east of Colton on the east side of the river and crossing the highway running toward South Colton. This is presumably part of the Colton esker men- tioned by Chadwick (’20). Terminal moraine areas. Several terminal moraines have been mapped across this quadrangle in a very generalized manner by Taylor (’24). The moraines are continuous farther west, but it is apparent from a consideration of Taylor’s paper that considerable interpolation was necessary in order to map the moraines as con- tinuous across the area now under discussion. The writer thought this not advisable on the more detailed map and thus terminal moraine has been mapped only when seen and recognized as such. Patches of till were interpreted as terminal moraine when they displayed rough, rolling, irregular, pitted topography, characterized often by good kame moraine. The material making up the moraine is sandier than is usual in terminal moraine material. Consequently the relief is often somewhat subdued. In general, the relief of the terminal moraine areas is far less than the relief etched in the bed rock, so that moraine topography is subordinated. Northeast, north, west and southwest of West Parishville is a patch of moraine that extends for a linear distance of three miles; in some places it is a mile across. Its northeastern end, which is hummocky, is protected by the concave curve of the rock highland lying just to the east. The small northern protuberence west of Stafford brook is of greater relief, and some kames were seen. Farther south in the area where the road running northeast from Brown’s bridge crosses the moraine it has become very sandy with numerous pits, some large enough to be shown as depressions on the map, which may be either kettle holes or depressions caused by removal of material by the wind, or both. This patch is terminated on the south by a group of kames of which two large and distinct ones may be picked out on the topographic map just a half mile southeast of the con- fluence of Raquette river and O’Malley brook. The elevation of this morainic area ranges from 580 feet to 680 feet above sea level, except at the extreme south, where the kames go up to 760 feet. Immediately across the river from Colton is an elongate gravel hill 60 feet in height that has kamelike characteristics. It reaches an elevation of 960 feet. A mile southeast of the hill just mentioned 44 NEW YORK STATE MUSEUM begins another morainic area with well-developed kames. It is also bounded on the east by a high rock upland. This area broadens a mile farther south, where it crosses the road and becomes more sandy. In its southern part it reaches to looo feet. On the south and west sides of the river and paralleling it from South Colton for three and a half miles downstream extends a belt of very sandy moraine. Many of the hills in this patch, especially at the northern end, are elongated parallel to the probable ice direc- tion which is also indicated by the striae a short distance to the west. The part south and southwest of Sputh Colton that is not as sandy displays several fine kames. Elevations range from 900 ; to 1000 feet. Paralleling the lane running northeast from South Colton on the south side of the Raquette occurs a long, narrow, low morainic ridge. It dies out on the western end about three quarters of a mile east of South Colton and was last seen by the writer in the forest a mile and a quarter farther east. Its average elevation is about 1050 feet. Around Horton ponds, two and a half miles east of South Colton, ' is a small patch of moraine that is also very sandy. Horton ponds are depressions in this moraine. Elevations range from 1200 to 1300 feet. In the vicinity of Whitaker falls, a mile downstream from Parish- ville on the west side of the river, is a small area of weakly developed 1 moraine. Its elevations range between 700 and 780 feet. Just below the fourth road crossing of Alder Meadow brook above 1 the brook’s confluence with the St Regis is found the end of an elongate section of moraine that runs north along the west side of the brook for a mile and then runs slightly northwest for another three-quarters of a mile. This is a well developed moraine; the relief is high, good kames and kettle holes are numerous. The typical morainic topography may be easily seen on the topographic map. Its material is chiefly gravelly and bouldery rather than sandy, as in several of the previously described areas. Elevations are between 800 and 960 feet. Northwest and southeast from Pickpttville, which is about two miles south of Parishville, extends a two-mile stretch of moraine tha.t is perhaps the best developed one in the quadrangle. The moraine is quite sandy, especially in the northern part, but farther south it becomes more gravelly. A mile south of Pickettville between the two converging streanjs forming the headwaters of GEOLOGY OF THE POTSDAM QUADRANGLE 45 Barton brook is an excellent kame. Elevations range from 900 to 1100 feet. Another area in the quadrangle that the writer believes to be terminal moraine, lies immediately north and northeast of Catherine- ville School. The peculiar elongate hills trending a few degrees south of west are strikingly conspicuous on the topographic map. Their material is gravelly and in places sandy. Their trend is nearly at right angles to the direction of elongation that drumlins should have at that locality, still they resemble drumlins. The writer believes them to be morainic features not drumloidal in origin. Abandoned glacial drainage channel. The abandoned glacial drainage channel, which begins at the east edge of the quadrangle at latitude 44° 35', extends down the valley of Alder Meadow brook nearly to where the brook makes its sharp turn to the north, thence across the flat to the valley of Dead creek and down that to the Raquette river about two miles above South Colton, was copied entirely from the previous map by Fairchild (T9, plate 7). Much of the course of the channel is through country extremely difficult of access; the cliannel is conspicuous, however, in several places. Large areas of water-laid gravel occur along it in the flat areas between the above mentioned right-angle bend of Alder Meadow brook and Dead creek. Glacial lakes, an arm of the sea, and their shore and near shore features. The shore lines of Lake Iroquois, the Gilbert gulf and lower marine stages, mentioned previously, are very well developed in the Potsdam quadrangle and have already been mapped by Fair- child (op. cit). The present map is slightly more detailed and any changes are additive only. The shore line of Lake Iroquois enters the quadrangle from the west near the southwest corner of the area. It may be traced across the quadrangle in a general northeast direction. In detail, of course, the shore line is very meandering as the country against which the lake lay was quite rough. The shore makes deep indentations up the principal valleys, the Raquette and the St Regis. It leaves the area about six and a half miles south of the northeast corner. The total tilting across the region is 40 feet, as it enters from the west at an elevation of 880 feet and leaves at 920 feet. Several gravel bars are well shown near Claflin School, the upper one being taken as marking the highest stand of the lake. From Claflin School the shore line makes an indentation up Leonard brook and then up the Raquette to the vicinity of South Colton. 46 NEW YORK STATE MUSEUM Just southwest of Colton a granite knob formed an island in the lake with a good gravel bar on its northeast side. Another smaller island, or at least near island, existed south of the one just mentioned and between it and the mainland. The indentation up the Raquette inclosed much of the morainic belt already described. The Raquette, it may be seen, thus built its delta in a long, narrow, constricted, bay of the lake. In places it has covered the moraine, but some of the features are still observable in the depressions now occupied by several ponds. Perhaps the ice blocks whose melting brought into existence these kettle holes had not melted completely at the time of the formation of the delta. The eastern side of the i smaller island spoken of above was overlapped by the sand delta that was built clear to, and partially around, the larger island. A higher stand of static water, probably a small body, is indicated by the level sand terrace three-quarters of a mile west and slightly north of South Colton. A still higher stand can be picked out on the topographic map a few miles to the south in the Stark quadrangle. Successive lower stages are indicated farther north, across the river and north of Colton, a mile and a half northwest of Colton, and a half mile west and slightly south of Brown’s Bridge. From the South Colton indentation the shore line runs in a general northerly direction to the vicinity of High Flats. Between Colton and High Flats another large island lay close to the shore. From the northern end of this island eastward the shore line may be almost continuously followed in the field by the sandy beach terraces. A broad sandy section will be noted north of the north end of the last mentioned island. A westward curving hook occurs west of the north end of the island and another northwest of Parishville. Westward moving littoral currents are thus indicated in Lake Iroquois. This is strange as the lake’s outlet lay to the north- east at Covey Hill ; however, the very presence of so much sand along the shore west from Parishville indicates the same thing, for a glance at the map will show that it would be impossible for the sand to have been supplied by the Raquette. It must have come from the St Regis. Just west of a line connecting High Flats and Parishville Center the beach terrace is interrupted by the valley of Parkhurst brook and the southern extension of the eastern part of the terrace is also cut off by the eastern headwater of the brook. Just west of High Flats is a small kamelike hill whose top is lower than the top of the sand plain. It seems probable that the brook GEOLOGY OF THE POTSDAM QUADRANGLE 47 i valley and the kame just mentioned were once filled and covered with f sand and have subsequently been eroded and reexposed. The shore line from High Flats runs on northeast for a little over a mile and then turns east about a mile and a half south of Parish- ville Center. At this point three good gravel bars at successively lower stages are found. The shore makes a small indentation up Alder Meadow brook, another up Barton brook, and a deeper one - up the West Branch of the St Regis river. West of the valley of Alder Meadow brook in the mouth of the j. indentation mentioned above a small part of the terminal moraine, before described, protruded as an island above the waters of the lake. From the point where the shore line crosses the St Regis, two . and a half miles above Parishville, it swings down again close behind ^ the village and then turns northeast around Catherineville hill and proceeds beyond the limits of the map. Special attention has been called by Fairchild to three gravel bars a mile east of Parishville. The writer believes it doubtful that the St Regis delta ever filled j the whole area between the long hook east of Whitaker falls and the I conspicuous sandy promontory southeast of Crane School and the * shore line; the shapes of the lakeward facing delta fronts are too " typical to have been produced by erosion entirely. It is difficult to tell how much etching has gone on in this area since Lake Iroquois time. The source of all the sand for the wide and continuous sand beach terrace from Parishville east is somewhat of a problem. The most plausible source seems to be the East Branch of the St Regis river farther east in the Nicholville quadrangle. A higher stand of static water is again indicated, as at South i Colton, by a broad sand flat on either side of Barton brook above the Iroquois lake level; and a lower one at Allen’s falls. ! Just 300 feet below the shore of Lake Iroquois and roughly ji paralleling it is another distinct shore line which is nearly as distinct , as that of Iroquois. It has been called the shore line of Lake Emmons, I but on evidence produced by Professor Fairchild it is now believed to mark the highest stand of the Gilbert Gulf. The writer found no evidence in the Potsdam quadrangle to tell whether the waters of I this body were fresh, brackish or salt. The lower shore is not as irregular as the upper because the ter- rane is more regular at the lower level. Gravel bars are found west of Hannawa falls, northwest and I northeast of Southville, and in the vicinity of Converse. 48: NEW YORK STATE MUSEUM The shore line is not marked by a sandy beach terrace as in the case of Iroquois, but three large and distinct deltas were built where the waters of the Raquette, and the West and East branches of the St Regis poured into the Gulf. All three deltas are built almost directly away from the shore. There appears to have been little long shore action, as in the case of Iroquois. The remnant of a small delta is found along Trout brook. As the sea retreated from the area bars were built at successively lower stages and many of these may now be found along the sides of the drumloidal hills. Sometimes these are associated with sand flats such as the sand plain around and between Old Forge School and Buckton, and farther east across the river. It is probable that in preglacial time the Raquette river flowed northwest from South Colton down what is now the valley of Leonard brook. As Chadwick says, it is kept from that course now only by a portion of its Lake Iroquois delta. It would appear, from the presence of the esker in Leonard Brook valley, that its course was changed before the time the lake existed. Otherwise it hardl}' seems possible that the esker could have escaped removal. From Colton northward to Brown’s Bridge the Raquette now flows in a i postglacial rock gorge. At Parishville also the St Regis flows through a postglacial rock gorge for a short distance. Its old channel was westward from the oxbow a half mile above Parishville and into the present valley of Barton brook. A portion of the delta forms the dam in this locality also. In figures 49 to 55 are shown some of the glacial shore and near shore features. STRUCTURAL GEOLOGY THE PRECAMBRIAN The general problem. Most of the structural movements that have affected the rocks of the Potsdam quadrangle took place during Precambrian time. It is to the Precambrian rocks therefore that we turn in an attempt to work out the structural history of the region. All of these ancient rocks are gneissic to some degree and the various attitudes of the planes of foliation furnish the first key to their structural history. Superimposed upon the broader structural features are found minor structures such as crumpled quartz veins and pegmatite dikes, disrupted inclusions of one kind of rock in another, and smaller folds within the larger ones. There GEOLOGY OF THE POTSDAM QUADRANGLE 49 is in addition the crushing phenomena as shown by microscopic examination of thin sections. As has been stated, nothing is known of the ancient sea floor upon which the Grenville sediments were deposited. They must, however, have been laid down in an essentially horizontal attitude. As seen now they are complexly folded, squeezed, disrupted in part, recrystal- lized and intruded by a large volume of igneous material. The granites are found within the Grenville rocks in bodies of all sizes from those that are to be measured in inches to those which are to be measured in miles. Most of the intrusions, however, are of the concordant type. One of the features of the Adirondack region is the general parallelism of the bedding of the Grenville rocks, when it is clear enough to be recognized, and the foliation of the igneous rocks. This and other field observations lead to the conclu- sion that many of the intrusive bodies in the Grenville areas are sill- like, but the rather sharp change from an area essentially of Gren- ville metasediments to an area essentially of granites lends credence to the conception that the main granite masses are batholithic. Nothing is known about the attitude of the Grenville sediments at the time of the igneous intrusions. From the usual coincidence of mountain building and intense folding with igneous activity it is probable that the compression of the Grenville beds took place at the same general time as the intrusion of the igneous material. This hypothesis is strengthened by the fact that all the granites are gneissic, even those that do not show crushing. Thus it is deduced that the banding in the uncrushed granites is primary. The crushing that does occur has without doubt been superimposed upon the already gneissic rock. It is the logical conclusion that the same tectonic forces which folded the ancient sediments so intensely also caused (or allowed) the great batholithic intrusions, and gave to the igneous rocks a distinct primary banding. With the above outline of the general problem and the kinds of evidence that are to be found, a more detailed discussion of the structural phenomena will be given. The prevailing strikes within the quadrangle are to the northeast and the dips to the northwest. This is in general accord with most areas in the northwestern Adi- rondacks. It is to be noted, however, that a gradual change of the average strike of the foliation takes place within the quadrangle. A consideration of the southern and eastern parts of the map shows that the foliation trend in the regions represented is considerably more easterly than in the rest of the quadrangle. 50 NEW YORK STATE MUSEUM Gabbro. The only gabbro mass recognized by the writer as such within the quadrangle has already been mentioned as belonging to the great sigmoidal flexure described by Martin in the Canton quad- rangle. Its features have been discussed in admirable fashion in Martin’s report (’i6) and will not be touched on further here. Suffice it to say that ample evidence from other localities definitely places the gabbro as the earliest of the intrusions. Its intrusion appears to have been in the form of bosses and of sills which have subsequently been folded and somewhat crushed. Gabbro masses appear to have been frequently protected from crushing by the more plastic host rocks, the Grenville sediments. Granites. Most of the observations within the granite areas indicate that the foliation is isoclinal so that the dips are either to the northwest or to the north. The strikes, however, indicate that the foliation defines large structures within the granite masses. These are vague and difficult to study in detail or to limit accurately. Their very presence, however, suggests the possibility that other large structures may be present but are rendered unrecognizable by the complex isoclinal folding. The occurrence of comparatively large inkers of Grenville sediments and mixed rock strengthens the above possibility in that their plan views are often arcuate. These inkers may be interpreted as roof pendents or isolated inclusions caught up in the intruding granites. The mass of White’s hill is taken as an example of such a major structure within the granite. The arcuate shaped mixed rock area is to be noted. Many quartz veins and pegmatite dikes occur in the granites. In general these are of two kinds : those which are parallel to the folia- tion and those which cut the foliation. The ones which cut the foliation are probably for the most part of later date and may have been intruded into the shrinkage cracks of the cooling mass. They usually show definite dikekke contacts against the granite. The ones parallel to the foliation are not all of this type, however. They are frequently highly folded and complexly contorted and have the appearance of squeezed and flattened segregations in the granite. Perhaps the tectonic movements during the consolidation of the granite aided the segregation of pegmatite material, which, as the movements continued, was squeezed out into lenses and folded (figure 5). Smaller inclusions of amphibolite, presumably of Gren- ville origin, also outlined such minor structures, as is shown in the photograph reproduced as figure 34. It does not seem impossible that a doughy cooling granite mass could, under conditions of great stress, yield by flowage to form GEOLOGY OF THE POTSDAM QUADRANGLE 51 just such structures as have beeen described. The crumpling of the inclusions in the granite was often found to be such as would indi- cate that a minor northeast-southwest compressive force had acted in addition to the major northwest-southeast force. Figure 5 Sketch of pegmatite in granite gneiss. Exposure is on the north slope of White’s hill The distinct difference between the coarse-grained and the medium- grained granites was mentioned in the descriptions of those rocks. It was also stated that the nature of the contact between the two was not known, but if it is a gradational one the zone of gradation is not greater than a quarter of a mile. The evidence is concealed as to whether two distinct intrusions are to be dealt with or whether the coarser granite is merely a more slowly cooled facies. In any event the coarse granite solidified at least a little later and is there- fore younger than the medium-grained granite. The medium-grained granite in the latter case can be considered as a more quickly cooled border facies of the coarse granite. The wide zone of medium- grained material could be interpreted as being due to the fact that the Grenville contact was close above the present surface. The pres- ent surface therefore cuts the gradational zone at a low angle. Ample evidence for this could be advanced by citing the Grenville inclusions in the granites. The author favors the above interpretation. It was hoped that the study of thin sections might prove the presence of zones of crushed rocks running across the quadrangle roughly parallel to the general strike analogous to those described 52 - ■ NEW YORK STATE MUSEUM by Smyth and Buddington (’26) in the Lake Bonaparte quadrangle. This was, however, found to be only partially true. None of the thin sections of the coarse-grained granite gave evidence of crush- ing. The medium-grained granite sections frequently did, especially in regions contiguous to the contact between that rock and the Gren- ville both in the main granite mass and in the larger sills within the Grenville and also in the more brittle Grenville rocks them- selves. The crushed rock did not extend in a definite band, how- ever. The Allen’s Falls quartzite shows cataclastic texture (figure 13). Thin sections from the sills between Colton and High Flats frequently display protoclastic-cataclastic texture (figures 30 and 31). Some of the smaller bodies are apparently uncrushed, prob- ably because of the protection of the more plastic Grenville lime- stone. The crushing indicates that intense distortive forces were active during and after the consolidation of at least part of the medium- grained granite. The fact that the coarse-grained and much of the medium-grained granite shows no crushing indicates that the main mass was strong enough to withstand the forces without crushing, or that the forces were dissipated before reaching the interior areas, or that the rocks solidified after the period of activity of the forces. The younger granite. Smyth and Buddington (’26) have shown that the concordant granite masses within the Grenville probably belong to two different times of intrusion. The writer considers the crushed masses between High Flats and Colton as belonging to the early intrusion, the same as the medium-grained granite; the ovate area west of Colton with its associated aplitic sills as belong- ing to the later intrusions. Perhaps the later intrusions can be correlated with the coarse-grained granite. The Colton granite mass is believed to be a structure similar to a phacolith. This type of body, which is common in the northwest Adirondacks, has been discussed by Buddington (’29, p. 51). The strikes in both the granite and the mixed rock roughly parallel the contact around the mass. Some of the few apparent anomalies may be explained by calling attention again to the fact that this particular contact is quite arbitrary as to its accurate location, although it is believed to be essentially correct. Grenville rocks. The most conspicuous structural feature of the quadrangle is the large West Parishville garnet gneiss mass. Its general attitude is that of an irregularly asymmetrical syncline. The strikes around the periphery do not quite completely box the com- pass, thus completing the structure. On the northwest extension GEOLOGY, OF THE POTSDAM QUADRANGLE 53 that juts out toward Stafford Corners the strikes on both the north- east and the southwest .dipping limbs are nearly parallel, that is northwest. No northeast strike is found. Thus the conclusion is inevitable that the garnet gneiss extends somewhat farther toward Stafford Corners beneath the glacial drift cover. It would be interesting to know if its manner of completion is similar to the complete curving structure found at the southern end of the area. The strikes in all cases except the one mentioned above are more or less concordant with the outline of the mass on the surface. Around most of the circumference the surface falls sharply down from the more resistant garnet gneiss rim to the valleys underlain by the next older formation, the limestone. The rim is especially noticeable where the edge of the syncline forms the northern side of the valley of O’Malley brook. Surface observations indicate that the western limb is much steeper than the eastern, although the eastern limb probably steepens as it approaches the axial plane. Consequently the areal surface occupied by the easterp limb is greater than that occupied by the western. A little south of West Parishville the fold appears to be slightly overturned. Figure 8 is a '.structure section which crosses the West Parishville syncline near its center. ' • The major structure has, superimposed upon it, a complex series .of minor structures in the form of small pitching folds, crumplings, and warpings. A careful study of these minor structures would, no doubt, throw much light on the major fold (see figure 56). As stated by earlier writers and as restated in the description of the garnet gneiss, the garnet gneiss has acted as comparatively plastic material. The included pyroxenic amphibolite masses and bands have responded to the forces in a more rigid manner so that, they are broken and pulled apart in a great many instances (figures 57 and 6). The complex; foldings in the garnet gneiss are commonly revealed by the alternating bands variously rich in garnets, so that in these gneisses much is evident that is completely obscured in a rock such as the Grenville limestone, which recrystallizes in a more homo- geneous manner. The roughly circular area of garnet gneiss south and west of Brown’s Bridge exhibits many features similar to the West Parish- ville syncline. There can be little doubt that it represents the same formation as the last described structure; therefore from its rela- tions to the West Parishville structure it has also been interpreted by the writer as a syncline. From the observations on the particular 54 NEW YORK STATE MUSEUM area the fold could be considered as an isoclinal anticline, but in that case no correlation with the West Parishville syncline could be attempted. I * f *1 Garnet Gneiss Concealed Figure 6 Sketch of pyroxenite-amphibolite and pegmatite in garnet gneiss. Exposure is in the northern part of the West Parishville syncline Minor structures are common all through the mass just as they were in the West Parishville syncline. The same scarplike rim is prominent. The fold is overturned, however. Areas of Grenville limestone and mixed rocks occur between the overturned domical phacolith and the two garnet gneiss synclines. The same belt swings northward east of the West Parishville syn- cline and occupies a broad zone between that structure and the main granite mass farther east (see figure 7). GEOLOGY OF THE POTSDAM QUADRANGLE 55 The structural features of the belt of limestone and mixed rock are obscure, but on the basis of probable stratigraphic sequence and the structural units already described some suggestions are offered. The stratigraphic sequence from older to younger is as follows: Allen’s Falls and Alder Meadow Brook quartzites ; Grenville lime- stone with some quartzite and quartz schist layers near the base; Grenville garnet gneiss. The broad belt of Grenville limestone, mixed rock and quartzite lying east of the West Parishville garnet gneiss syncline is part of that structure and forms the eastern limb. The thickness prob- ably is not as great as it appears because of the intimate granite injections and the sills in the series. An anticline, perhaps crumpled on the crest, exists between the two garnet gneiss structures in the vicinity of Brown’s Bridge. Erosion has not planed the area deeply enough to expose the quartzite again. Farther to the south the phacolith was intruded into the Gren- ville anticline either at the time of its formation or subsequently. The mixed rock originally passed over the roof of the phacolith. Thus a minor synclinal fold is necessitated between the southern boundary of the phacolith and the main granite mass farther south. This fold dies out to the northeast. The plasticity of the Grenville formations, the variable amounts of intrusive material in them, and the complex nature of the tectonic forces account for the extreme complexity of structure. All of the phenomena described must have taken place far below the surface of the earth. No volcanic rocks have been found in the area and the features displayed are those typical of the results of intense regional metamorphism in the zone of rock flowage. Erosion is responsible for planing down the crust and revealing the structures as they now exist. THE PALEOZOIC Minor movements have taken place since Paleozoic time, as shown by the attitude of the Paleozoic rocks of the quadrangle. The folds are for the most part gentle and dips are rarely found exceeding ten degrees. The major structural features of the Paleozoics within the Potsdam quadrangle are effectively concealed. There is an increasing amount of evidence, however, to indicate that the fold- ing is more like the basin and dome type typical of the Mississippi valley than like the Appalachian type. 56 NEW YORK STATE MUSEUM Several small folds were observed by the writer in the Potsdam sandstone just below Whitaker dam. If the pseudo-unconformities within the Potsdam are interpreted as actual unconformities a vast amount of Cambrian tilting must be assumed, for the planes above and below the pseudo-unconformities are often nearly at right angles to each other. THE POST-PLEISTOCENE Post-Pleistocene tilting is shown by the gradual lateral slope of the shore lines of the Gilbert gulf and of Lake Iroquois. The difference in elevation across the quadrangle is about 40 feet, the eastern end being the higher. RESUME OF GEOLOGIC HISTORY THE PRECAMBRIAN The oldest known rocks of the Potsdam quadrangle and, in fact, the oldest known rocks of the Adirondacks are those that make up the Grenville series. These are represented by garnet gneiss, crystalline limestone, quartzite and a variety of mixed rocks. The great divergence of rock types assignable to the Grenville series is the result of two factors : ( i ) the differences in character of the original sediments and (2) the different manner in which the sedi- ments have responded to subsequent events. The much sought for basement or floor of the sea on which the Grenville sediments were deposited has never been found, or at least has never been recognized as such within the limits of the Adirondacks. Very possibly the rocks of this ancient sea bottom have been rendered unrecognizable by intrusion and metamorphism; Perhaps they have even been remelted to form some of the intrusives. Presumably the garnet gneiss, limestone and quartzite represent argillaceous, calcareous and arenaceous sediments respectively. The complete stratigraphic sequence of the Grenville rocks is not known, but locally the limestone can be placed definitely below the garnet gneiss, and the quartzite, in general, possibly below the limestone. Some time after the deposition of the Precambrian sediments a period of igneous activity was instituted. How much time elapsed between the deposition of the sediments and the time of diastrophism and what the history was during that time are not known. ,The earliest intrusion into the Grenville series was of gabbro. The gabbro is only slightly represented in this quadrangle being confined to a small area near the southwest comer of the quadrangle and being part of a larger mass occupying the Canton quadrangle. Figure 7 StrucJure scclion along C-C’ on Map i w Tl«» )a Jvn bixiU fr"-'Tl ?8i«is HnifiO ^notMmit ^divn^Tf) »«lrto» Otonp hfts Mizjt^uQ BET^' ^ ^>lirn 1 elstip^ d-jui I ;»1«9s (slRaxt'loH 1)00 1 Henjpa rfsui I :3Uht ItntnV \ ■ jy N 4\ N V 'V ' / .» N- \ a <» -4 .% * .V ,: ^ •, * ,» ^ ,, ^ ,V A-V A .', .', ifc 4* •'« v ^ •■> y ; * A ••. •{. :, t> t » cat. i. ,<‘, z, Ai *, * A ; u 1 a B A. 4,.*. ,’. A ., 4 < ,,'i jT'iB^^Aa .'-v . ■ U*'! V»;::ii. -'s . ■ . ‘\nn i t ft •'Cv *• i a ""v.w 'M' y % .!5 ^ v .V/JZ^V.- ^ P'S .'. ^ ■ I V H ^ /j'\ ■'■-■ ■ •■' « •is, i I V « v,/,yi. .V. . „.■, « .•■ u IB. 4 :.v, * ”, .it/ . ' ■ e'i ■ ■’s V <■ HX'V# 4 4 if «\'3'- v*’''»54|->.f '.'S^ , ^Ij. AbM X //^ >v^ ■ A 2: « jnUBi^ .,« »w,yj U..J) .V, )tj4,, »'l' GEOLOGY OF THE POTSDAM QUADRANGLE 57 The gabbro was followed by a series of granitic intrusions that ordinarily show concordant relations to -the Grenville sediments, into which they made their way, in the areas where the Grenville rocks , are conspicuous. A great part of the Precambrian division of the quadrangle, however, is composed almost entirely of granitic rocks that must be interpreted as batholithic in nature. During the orogenic period the sediments were complexly folded and greatly compressed so that they must occupy only a small fraction of their previous area. The forces which folded the sediments were due probably in part to the forces causing the igneous activity and in part to the forces exerted by the intrusions themselves. The Grenville sediments were variously affected by intrusives and the diastrophic forces. The sandstones were changed to quartzites. The limestones were converted to marbles. In many places calcareous sediments were torn apart, shredded and digested by the granites. In other localities calcareous beds were changed over to pyroxenites, amphibolites and pyritous gneiss. In still other localities the lime- stone, in addition to being recrystallized, was permeated by hydro- thermal material, giving rise to feldspar crystals, serpentine nodules and. a number of other minerals. These complicated reactions and additions have been responsible for a large proportion of the mixed rock of the quadrangle. The shales were metamorphosed to garnet gneiss, which is itself a mixed rock, as it is highly injected with granitic or pegmatitic material. The main compressive forces apparently acted in a northwest- southeast direction but were modified somewhat by another minor set of forces which acted nearly at right angles in a northeast- southwest direction. To the interplay of the two sets of forces may be assigned one of the reasons for the complex nature of the folding. During and following the times of great tnountain building and igneous activity above outlined, the region remained a land area, ,SO far as is known, until Cambrian time. There was therefore suffi- cient time for the mountain mass to be worn down by erosion to a comparatively flat sloping plain. The surface of the plain was somewhat rolling and the monotony was relieved by ridges and hills pr harder gneiss and quartzite ledges. The streams must have been ..sluggish and flowed chiefly in the limestone areas. It is probable that deep residual weathering occurred during this interval, for by this means would be liberated the quartz for the great sandstones which were subsequently deposited. 58 NEW YORK STATE MUSEUM THE PALEOZOIC The idea is held by some that a climatic change took place early in Cambrian time and that the old surface became a vast desert of wind drifted sand. Cambrian glaciation has also been postulated as responsible for some of the Potsdam conglomerates. These ideas are certainly tenable but must be considered as highly speculative. Thin sections of the Potsdam sandstone at Hannawa Falls show rounded quartz grains typical of water-laid sands from the “fossil sand dunes” of Chadwick. The ancient surface was gradually submerged beneath the sea in middle Cambrian times. The Potsdam sandstones were the first sediments deposited on the floor of this sea. Possibly an uncon- formity signifying a considerable time interval occurs in the Pots- dam. Evidence in this quadrangle, however, is interpreted by the writer as not being indicative of such a break. There were certainly fluctuations in conditions during Potsdam time but direct evidence of a major unconformity within the Potsdam was not found. Not much significance is given to the variable colors of the sandstones, although they do appear to be more highly colored in the lower strata. The large scale cross-beddings at Hannawa Falls and Fort Jackson (Nicholville quadrangle) are believed to be delta phenomena. Our stratigraphic record is lost here for a while because of glacial cover but from other regions it is deduced that gradually deeper water covered the area and the mixed beds of the Theresa, alter- nating strata of sandstone and sandy dolomite, were laid down. Above the Theresa is found the white Heuvelton sandstone indi- cating a minor elevation of the region. A stratigraphic break is believed to occur between the Heuvelton and the beds of the Buck’s Bridge, next above. Any beds originally above the Heuvelton would have been removed; therefore nothing is known of what happened just before the advent of the Ordovician, which is considered as being inaugurated with the deposition of the mixed calcareous, dolomitic and sandy beds of the Buck’s Bridge. It is not at all certain that the Cambrian gives way to the Ordovician with the deposition of the Buck’s Bridge but it seems to be the logical horizon at which to place the change. Another break occurs between the top of the Buck’s Bridge and the Beekmantown (Ogdensburg) dolomite, which is the youngest Ordovician formation found in the Potsdam quadrangle. The record, for this region, is again lost until the advent of the Pleistocene. GEOLOGY OF THE POTSDAM QUADRANGLE 59 THE PLEISTOCENE Just previous to the advance of the ice the physiography and general elevation of the quadrangle was much the same as it is now. The drainage pattern was somewhat different with rivers taking different courses and with possibly a major river flowing parallel to the highlands in the region of the present concealed zone. The ice first reached the quadrangle probably in the northwest corner and it was part of the previously mentioned St Lawrence valley lobe. The advance of this lobe was by means of a spreading flow, in the direction of the main advance in the lobe’s medial parts and curving outward away from that direction toward the thinner lateral parts. Subsequently the advancing ice rode over the entire quadrangle The striae and drumlins were the first formed features that are now recognizable. As the ice cap became thicker and more widespread its weight greatly depressed the land surface. The ice retreated, as it advanced, in an oscillatory manner. At each stand of any length a terminal moraine was built. As the higher rougher land was reexposed small lakes were formed in many valleys by ice dams in the valley mouths and by deposits of drift. The ice also excavated depressions, which were undrained and which became basins for small permanent lakes, as some of the ponds in the southeast ninth of the quadrangle. With further retreat, the upland Adirondack area and outlying low divides farther southwest, — caused perhaps by the lagging rise of the land due to the removal of the heavy ice — became a more continuous divide and the great glacial lakes came into existence. On the north the lake water laved the retreating ice front, which passed to the east diagonally out of the lake onto higher land. This is shown by the emergence of the terminal moraines from below to above the Iroquois shore line. The eskers near Claflin School and Colton must have been formed before the ice retreated from those localities. As the ice retreated northward the ground moraine was deposited over the northern part of the quadrangle. At last the ice front reached the locality of Covey hill, Quebec, and the drainage went into the upper Hudson valley. The outlet gradually lowered until sea water was admitted to the St Lawrence valley region and the bars and deltas of the Gilbert gulf were formed. Subsequent rise of the land caused the sea to recede, uplifted and tilted the old shore lines, and the present conditions came into existence. Erosion has somewhat destroyed the original continuity of some of the features, the terminal moraines in particular. 6o NEW YORK STATE MUSEUM ECONOMIC GEOLOGY WATER POWER All three of the rivers which cross the Potsdam quadrangle — the Raquette, the West branch of the St Regis, and the East branch of the St Regis — are being actively exploited for water power at the present time. The power in nearly all cases is converted into elec- trical energy for transportation, but a few dams impound water for use in water power mills such as paper mills and saw mills. The electrical power projects have developed long stretches of the rivers so that very little of the fall goes to waste. For instance, the dam about two and a half miles above Colton backs the water up nearly to South Colton. The dam at Colton backs it up almost to the foot of the last-mentioned dam. The penstock from the Colton dam debouches just above Brown’s Bridge at an elevation only a little above the top of the dam at Hannawa Falls. Sixty per cent is a rough estimate of the part of the fall of the major streams of the area that at the present time is in some meas- ure harnessed. The distribution would be somewhat as follows: Raquette river, total fall in quadrangle 860 feet, of which 570 feet is used in power development; West branch of the St Regis river, total fall 600 feet, of which 400 is used in power development ; East branch of the St Regis river, total fall 140 feet, of which none is used in power development. Most of the electrical power plants are in the Precambrian divi- sion of the quadrangle, but most of the water power mills are in . the Paleozoic division. The reason is obvious. A mill requires only a 10 or 20 foot fall; the head needed in an electrical power plant of the size used in this region is often as much as 100 feet. It is only in the Precambrian division that such a head can be developed in a comparatively short horizontal distance. It is interesting to note that at least two of the larger electrical power developments are located at places where the rivers have been forced to cut rock gorges in Precambrian rocks since the Pleistocene. One is the project from the dam at Colton to the power house at Brown’s Bridge. The other is from the dam at Parishville to the power house near the mouth of Barton brook. Were it not for the dams of glacial material in the preglacial valleys these developments would not have been possible at their present localities. As noted by Chadwick (’19) many of the water power develop- ments below Potsdam on the Raquette are made possible by the rapids caused by the harder ledges of the Heuvelton sandstone. GEOLOGY OF THE POTSDAM QUADRANGLE 6i TALC Some talc is present in various places in the Grenville limestone, but it is doubtful if it exists at any place on a commercial scale. No deposits of commercial value have been discovered. Some prospecting for talc was carried on years ago by means of drilling at several localities east of Brown’s School. The tremolitic rocks east of Colton show no appreciable alteration to talc. LIMESTONE AND DOLOMITE Grenville. The abandoned kilns where Grenville limestone has previously been burned for lime are found at many places over the Grenville limestone areas. There is one on the north-south road about three-quarters of a mile due west of Brown’s Bridge ; several south and east of the large garnet gneiss syncline between Colton and High Flats; and one back of the last house on the east side of the road south of Pickettville before Trout brook is reached. Relatively pure limestone can be found at many places in the Gren- ville areas. As far as is known, no marble has been quarried within the quad- rangle for building purposes. Suitable deposits for such use might be found. Paleozoic. In the northern part of the area several small quar- ries have been opened in the dolomites and mixed beds for road metal. This probably represents the chief value of these forma- tions. Some of those above the Potsdam could no doubt be used locally for foundations, walls and other genera! building purposes. GRANITE Granite gneiss has been quarried in small quantities at several places over the quadrangle for use as road metal. Two such quar- ries are found east of South Colton and north of Parishville respec- tively. They are both intermittently productive. An old granite quarry on the northwest face of White’s hill, on the east side of the road about two miles southeast of Parishville and at an elevation of 1140 feet, has been abandoned because, it is reported, of transpor- tation difficulties. The rock was used chiefly for tombstones. Some of the stones in the cemetery at Parishville are from this quarry. The rock is a pink or grayish, fine to medium, even-grained granite,, which is full of irregular patches and veinlets of pegmatitic material, which on polishing gives a very beautiful effect. The rock is. jointed 62 NEW YORK STATE MUSEUM but not to a degree to make it unsuitable for quarrying into large blocks. The writer believes that this quarry may warrant further consideration from an economic standpoint. IRON ORES About a mile east of Parishville just south of the road intersection at an elevation of 920 feet is an old iron prospect. According to an old resident, considerable quantities of ore were removed from this locality more than 50 years ago. The relations at the present time are concealed to a large extent, and therefore the nature of the deposit is doubtful. It appears, however, to be a series of small lenses of magnetite in a pegmatitic phase of the granite country rock. Considerable pyrite is present in association with the magnetite. Both are later than the feldspars, as shown by thin sections. Were it not for the presence of so much sulphide this deposit might bear further prospecting. No large deposits of hematite, so common in the west and north- west Adirondacks, are known to be present in the quadrangle. These deposits are normally found below the Potsdam and near the contact of Grenville limestone and quartzite, and their origin has been explained by Smyth as the result of the weathering of Precambrian rocks, particularly the pyritic quartzite, the iron of which was carried in solution and precipitated by the action of the limestone. The associated quartzite and locally the Potsdam cover prevented their complete erosion. Smyth’s explanation is adhered to by Chadwick in his Canton quadrangle report. Some indications of such a deposit were noticed on the east side of the road that parallels the Raquette river on its east bank south from Potsdam a quarter of a mile south of Stafford brook. Cushing (’98) mentions this place in his report on the Potsdam-Precambrian boundary. PYRITE It is likely that even the well-known large pyrite deposits of the northwest Adirondack region are now of little present commercial value. It may be worthy of passing mention, however, that thin highly pyritic layers are present in the Grenville series in this region. One occurrence, which has been prospected, is found on the south side of the road near the western border of the quadrangle about two and a half miles west of Colton. The thickness of the pyritic stratum is probably about ten feet. A similar occurrence is in the river bank about half-way between Colton and Brown’s Bridge. GEOLOGY OF THE POTSDAM QUADRANGLE 63 SANDSTONES The best building stone to be found within the limits of the quad- rangle is the red Potsdam sandstone. This rock has been quarried extensively, only in a comparatively small area along the Raquette river in the vicinity of Hannawa Falls. All of the quarries are now abandoned and most of them are partially or completely flooded by the water backed up by the power dams. Several color varieties have been used extensively for building purposes ; one is banded dark and light red ; another is banded red and buff; another a deep, dark, even red; and one is essentially buff. In figures 58, 59 and 60 are shown buildings constructed of the Potsdam sandstone. The writer believes that the sandstone warrants further prospecting as a building material. A few houses in the eastern part of the area have been built of a light varicolored phase of the sandstone in which mottled browns, yellows and greens predominate. The source of this material is reported to be the abandoned quarries at Fort Jackson (Nicholville quadrangle) . Just above the Whitaker dam the white Potsdam sandstone has been quarried on a moderate scale (figure 42). Road metal is still being taken from this quarry in spite of the fact that the sandstone is a rather poor road material because of its crumbly nature, GRAVELS There are many gravel pits scattered over the quadrangle. Most of them are small and all of them are of Pleistocene age. There is a great supply of material that is suitable for road metal, but gravel suitable for concrete without prohibitive amounts of crushing, washing or screening is difficult to find. There is a large supply of clean, water-sorted gravel northeast of Hawk ledge in the flat between the two brooks, but it is isolated from the more settled regions. The terminal moraine areas are in general too sandy or too poorly sorted to furnish material of any economic importance except on a very small scale. Some of the kames may, however, contain good deposits of gravel. The gravel bars are worthy of more careful prospecting. There is a fine pit in one of the bars northeast of Parishville. The beach terraces and deltas are for the most part too sandy to be of economic importance. A few local deposits may be coarse enough to be usable. Ground moraine and drumlins furnish poorly sorted gravel and are workable only in exceptional cases. 64 NEW YORK STATE MUSEUM BIBLIOGRAPHY Adams, F. D. & Barlow, A. E. 1910 Geology of the Haliburton and Bancroft Areas. Province of Ontario. Can. Geol. Surv., Mem. 6: 1-419, maps Agar, W. M. 1923 Contact Metamorphism in the Western Adirondacks. Amer. Phil. Soc. Proc. 62, 3 : 95-174, 2 figs. AlUng, H. Ll 1919 Some Problems of the Adirondack Precambrian. Amer. Jour. Sci. 48 : 47-68, 3 figs. Buddington, A. F. 1919 Foliation of the Gneissoid Syenite-Granite Complex of Lewis County, New York. N. Y. State Mus. Bull. 207-8: loi-io, 6 pis. 1929 Granite Phacoliths and their Contact Zones in the Northwest Adi- 1 rondacks. N. Y. State Mus. Bull. 281:51-107, 14 figs. Burling, L. D. & Kindle, E. M. 1915 Structural Relations of the Precambrian and Paleozoic Rocks North 1 of the Ottawa and St Lawrence Valleys. Can. Geol. Surv., Mus. , Bull. 18 : 1-23, maps Chadwick, G. H. 1919 The Paleozoic Rocks of the Canton Quadrangle. N. Y. State Mus. \ Bull. 217-18:1-60, 12 pis., map Cook, John H. 1924 The Disappearance of the Last Glacial Ice Sheet from Eastern New , York. N. Y. State Mus. Bull. 251 : 158-76 Cushing, H. P. ■ 1899 Report on the Boundary between the Potsdam and Precambrian Rocks North of the Adirondacks. N. Y. State Geol., An. Rep’t 16 : 1-27, map 1905 Geology of the Northern Adirondack Region. N. Y. State Mus. Bull. 95:271-453, maps 1915 Age of the Igneous Rocks of the Adirondack Region. Amer. Jour. Sci. 4th Series, 39:288-94 Fairchild, H. L., Ruedemann, Rudolf, & Smyth, C. H. 1910 Geology of the Thousand Islands Region. N. Y. State Mus. Bull. 145 : 1-194, maps Newland, D. H. 1925 Geology of the Gouverneur Quadrangle. N. Y. State Mus. Bull. 259: 1-122, 16 figs., 14 pis., map Emmons, Ebenezer 1842 Geology of New York, Part 2, Sur. 2d Geol. Dist. St Lawrence County, p. 335-66. Fairchild, H. L. 1918 Pleistocene Marine Submergence of the Hudson, Champlain, and St Lawrence Valleys. N. Y. State Mus. Bull. 209-10 : 1-76, 25 pis. Fenneman, N. M. 1917 Physiographic Divisions of the United States. Assoc. Amer. Geog., An. Rep’t 6 : i9-<>8, map GEOLOGY OF THE POTSDAM QUADRANGLE 65 Flint, R. F. 1929 The Stagnation and Dissipation of the Last Ice Sheet. Geog. Rev. 19, No. 2:256-89, 25 figs. Gillson, J. L., Callahan, W. H. & Millar, W. B. 1928 Adirondack Studies : The Age of Certain of the Adirondack Gab- bros, and the Origin of the Reaction Rims and Peculiar Border Phases Found in Them. Jour. Geol. 36: 149-63, 6 figs. Martens, J. H. C. 1920 Glacial Boulders in Eastern, Central, and Northern New York. N. Y. State Mus. Bull. 260:81-116, 4 figs. Martin, J. C. 1916 The Precambrian Rocks of the Canton Quadrangle. N. Y. State Mus. Bull. 185:1-112, maps Miller, W. J. 1916 Origin of the Foliation in the Precambrian Rocks of Northern New York. Jour. Geol., 24:587-619, map 1918 Banded Structures of the Adirondack Syenite-Granite Series. Science, n. s., 48 : 560-63 1926 Geology of the Lyon Mountain Quadrangle. N. Y. State Mus. Bull. 271 : i-ioi, 9 figs., 13 pis., map Smyth, C. H. jr 1894 Report on the Geology of Four Townships in St Lawrence and Jefferson Counties. N. Y. State Mus. An. Rep’t 47 (1893) ; 685-709, map 189s Crystalline Limestones and Associated Rocks of the Northwestern Adirondacks Region. Geol. Soc. Amer. Bull. 6 : 263-84 1897 The Crystalline Rocks of St Lawrence County. N. Y. State Geol. An. Rep’t 15:20-21, 477-99 1901 Geology of the Crystalline Rocks in the Vicinity of the St Lawrence River. N. Y. State Mus., An. Rep’t 53 : 83-101, map & Buddington, A. F. 1926 Geology of the Lake Bonaparte Quadrangle. N. Y. State Mus. Bull. 269: 1-106, 24 pis., map Taylor, F. B. 1924 Moraines of the St Lawrence Valley. Jour. Geol. 32:641-67, 12 figs. Winchell, N. H. 1893 Minn. Geol. Surv. An. Rep’t 21 Figure 9 View in nortlierly direction from U. S. G. S. trianguhtion i>oiut, elevation 1427'. on top of White's hill. View is across the broad St Lawrence Valley. Note the level sky line of the Tertiary peneplain Figure 10 View north and northwest from hilltop (north end of West Parishv-illc synclinc) three miles cast of Hannawa Falls. Note gentle relief of St Lawrence Valley floor and level sky line. i i Figure ii View southwest toward Allen’s falls. The scarp is formed of Pre_cafnbrian quartzite which dips steeply in a westerly direction away from the observer Figure 12 Outcrop of white Grenville quartzite a mile east of High Flats. The observer is standing on quartz schist which immediately overlies the quartzite [69] Figure 13 Photomicrograph of quartzite from just above the bridge at Allen’s falls. Quartz groundmass is pulverized. Note several phenocrysts of microcline and albite. A very little magnetite was seen in this section. Crossed nicols, x 86 Figure 14 Looking south, upstream, at same locality as above, showing typical outcrop of the quartzite [70] [71] [72] Figure 17 Crumpled quartz schist on hilltop a mile south of Brown's School Figure i8 Outcrop of Grenville limestone a mile and a quarter north- east of Brown’s School. Note rounded surfaces and crumbly character of outcrop. In the right foreground, feldspar crystals may be seen in the marble Figure 19 Photomicrograph of the rock of the above locality. Main constituent is calcite. Note the rounded masses of serpentine. Many of these have magnetite in their centers [73] Figure 20 Photomicrograph of light-colored pyroxenite from the banks of the Raquette river, a mile below Rainbow falls. Diopside is the only mineral. Magnification, x 86 Figure 21 Looking east parallel to the strike at outcrop of pyroxene- bearing mixed rock a mile and a quarter northwest of Colton. The hammer handle is parallel to the dip [74l Figure 22 Typical outcrop of pyroxene-bearing mixed gneiss. This out- crop is a mile north of South Colton. Note crumpling of quartz layers Figure 23 Photomicrograph of amphibolite. Most of the dark material is hornblende. Some of the grayish laths are biotite. The light minerals are feldspar with a few grains of quartz. Nicols partially crossed, x 48 [75] Figure 24 Photomicrograph of garnet gneiss from a short distance north- east of West Parishville. Most of the dark patches are amphibole, a few are magnetite. A large irregular biotite lath shows in the center of picture. The light mineral with high relief is garnet, x 28 Figure 25 Photomicrograph of typical pyroxenite-amphibolite from West Parishville. Light areas are chiefly feldspar (albite and a more calcic one). The twinning bands are dimly visible. The large irregular crystal in the center, surrounding bleblike areas of feldspar, is pyroxene (augite). Most of the black areas are hornblende. Nicols partially crossed, x 28 [76] Figure 26 Exposure halfway between Parishville Center and Stafford Corners showing amphibolite-pyroxenite in- clusion in garnet gneiss being cut by pegmatite. Compass is about parallel to the average dip. The thin pegmatite stringer cutting the amphibolite is about six inches above the top of the compass Figure 28 View of garnet gneiss outcrop southwest of Brown’s Bridge. Thin, light-colored pegmatite injections may be seen, especially in the lower part of the photograph. The hammer handle crosses one pyroxenite-amphi- bolite inclusion, the head points to another, and a third is visible above and to the left of the hammer Figure 29 View of typical exposures of the garnet gneiss. Locality is near Pierrepont, on western border of the quadrangle west of Colton. Note simi- larity of outcrops to breaking waves. The moss in the foreground is on the dip surface [781 Figure 30 Photomicrograph of granite southeast of High Flats. Most of the phenocrysts are quartz although some are orthoclase. The fine- grained groundmass is chiefly quartz with some plagioclase. Mag- netite, hornblende, apatite and biotite are the accessories. Protoclastic texture. Nicols crossed, x 28 Figure 31 Photomicrograph of granite about halfway between Colton and Brown’s School. Excellent example of protoclastic texture. Dark bands are leaves of quartz. Groundmass is chiefly microcline. A little zircon is present in this section, x 48 [79] Figure 32 Photomicrograph of tourmaline-bearing granite from a mile north and a little west of South Colton. The black spots are tourmaline. The rest is microperthite with some quartz. Nicols partially crossed, X 28 Figure 33 Photomicrograph of granite from three-fourths of a mile north of Gain Twist falls. Composed principally of quartz and micro- perthite. Crossed nicols, x 48 I80I [8i] Figure 34 Contorted amphibolite in process of being Figure 35 Granite outcrop a half mile northwest of South digested by medium-grained granite. Locality a mile Colton. The face of the outcrop is one joint plane and the and a quarter above South Colton on the south bank of traces of a horizontal set of joint planes may be seen the Raquette river Figure 36 View up the Raquette river from the bridge at Gain Twist falls. The rock is the typical coarse-grained, pink granite gneiss Figure 37 View along the Raquette river near the southeast corner of the quadrangle, showing coarse-grained granite [82] Figure 38 Exposure below Whitaker dam on the St Regis river. At the right is a white appearing, sloping surface of granite gneiss. Overlying this and just beyond the pool is Potsdam sandstone Figure 39 Photomicrograph of Potsdam sandstone from quarries below Hannawa Falls. Made up of rounded to subangular quartz grains, each grain surrounded by a thin film of hematite. The cement is silica which is frequently in parallel optical orientation with the quartz grain which it surrounds. A few crystals of zircon and apatite are present [83] Figure 40 Quarry face in Potsdam sandstone below the power house at Hannawa Falls. Note apparent unconformity which the writer believes to be cross-bedding on a gigantic scale Figure 41 A large boulder of Potsdam conglomerate a short distance north of West Parishville. Pebbles are white quartz and matrix is sand stained with hematite [84] Figure 42 View of a partially flooded old quarry in white Potsdam sandstone a short distance above Whitaker dam Figure 43 Cross-bedding in typical outcrop of red Potsdam sandstone a mile below Fort Jackson (Nicholville quadrangle) along the East Branch of St Regis river [85] Figure 44 Apparent unconformity in white Potsdam sandstone in the bed of a small stream halfway between Hopkinton and Fort Jackson (Nichol- ville quadrangle). The observers stand on the plane of apparent uncon- formity. The beds below dip toward the observer. The beds at right dip away from the observer Figure 45 Another view of the same locality as figure 44. The stream flows over the plane of apparent unconformity. The beds in the stream-bed dip upstream; those on the observer’s left dip away from him about in the >direction of his left arm [86] Figure 46 Looking southwest at exposure of the Theresa formation in the small quarry halfway between Sanfordville and Potsdam. The boulders in the background are from the Theresa Figure 47 View northeast along outcrop of Heuvelton sandstone in the bed of Plum brook three miles southeast of Norwood. The dip is about 10° to the north, which is unusually steep for this region [87] Figure 48 Looking northeast along valley strewn with boulders of Heuvelton sandstone. This locality is about a mile south of the locality shown in figure 47 Figure 49 View north at outcrop a quarter of a mile west of John’s pond. The pink granite gneiss juts up through the delta of Lake Iroquois [881 Figure 50 View southeast from a point one mile and a half south of Parishville Center, showing the sandy shore of Lake Iroquois Figure 51 Wind-blown sand on the surface of the delta built by the East Branch of St Regis river in the Gilbert Gulf [89] Figure 52 Looking northwest from near High Flats at Lake Iroquois beach terrace Figure S3 Drifted sand in same locality as shown in figure 52 [90] southeast from figure 54 View southeast from a poin the Gilbert Gulf delta of the East Branch liie southeast of Bucktoii, looking at front of Figure 56 Minor pitching synclinal fold in garnet gneiss three miles east of Hannawa Falls. Camera points west and the pitch of the fold is to the south Figure 57 Broken inclusion of pyroxenite-amphibo- lite in garnet gneiss a mile and a half southwest of Brown’s Bridge [93] [94] Figure 58 Front view of Potsdam State Normal School, constructed of bufif Potsdam sandstone Figure 59 Small mausoleum constructed of red Potsdam sandstone in cemetery southeast of Potsdam ‘.til Figure 60 Potsdam Catholic Church, illustrating the use of red , Potsdam sandstone as a building stone [95] INDEX Adams, F. D. & Barlow, A. E., cited, i6, 64 Adirondacks, in glacial period, 37 Agar, W. M., cited, 64 Ailing, H. L.,. cited, 64 Aluminous strata, mixed rocks de- rived from, 18 Amphibole-bearing gneiss, 18 Area, 5 Bed rock, division of topography controlled by, 42 Bibliography,, 64 Biotite gneiss, 17 Buck’s Bridge mixed beds, 35 Buddington, A. F., acknowledgment to, 8; cited, 52, 64 Burling, L. D. & Kindle, E. M., cited, 64 Calcareous strata, mixed rocks de- rived from, 14 Cambrian formations, 28 Chadwick, G. H., cited, 9, 28, 32, 34, 36, 41, 48, 6o„ 62, 64 Coarse-grained granite gneiss, 26 Cook, John H., cited, 37, 64 Culture, 7 Cushing, H. P., cited, 9, 62, 64 Dolomite, 36, 61 Drainage channel, glacial, 45 Drift,, division of topography con- trolled by, 38 Drumlins, 40 Drumloidal hills, 40 Economic geology, 60 Electrical power plants, 60 Elevations, 5 Emmons, Eb.enezer, cited, 64 Eskers, 42 Fairchild, H. L., cited, 41, 45, 47, 64 Fenneman, N. M., cited 5, 64 Flint, R. F., cited, 37, 65 Gabbro, 21, 50, 56 Garnet gneiss, 18, 19, 20, 52 Geographic location, 5 Geologic history, resume, 56 Geologic statement, general, 8 Gilbert gulf, 45,, 47 Gillson, J. L., Callahan, W. H. & Millar, W. B., cited, 65 Glacial drainage channel, 45 Glacial formations, 36; historical background, 37 Glacial lakes, 45 Glacial striae, see Striae Glaciation, 38, 59 Gneisses, amphibole-bearing, 18; bio- tite, 17; garnet, 20; mixed, 14; pyritous, 17; pyroxene-bearing, 17 Granite, 22, 27, 50, 52, 61 Granite gneiss, coarse-grained, 26; medium-grained, 23 Gravels, 63 Grenville limestone, 12, 61 ; term de- fined, 13 Grenville rocks, 52 Grenville sediments, 49, 56 Ground moraine, see Moraine Heuvelton sandstone, 35 Highways, 7 Hills, drumloidal, 40 Howell, B. F., acknowledgment to, 8 Ice sheets, 37, 59 Industries, 7 Iron ores, 62 Karnes, 43 Lake Emmons, 47 Lake Iroquois, 37, 45 Limestone, 61 ; Grenville, 12, 13, 61 ; impurities, 13; occurrence, 12; term defined, 13 Limestone, quartz mesh, term defined, II Location, 5 [97] 98 INDEX MacClintock, Paul, acknowledgment to, 9 Martens, J. H. C., cited, 65 Martin, J. C, cited, 10, ii, 22, 41, 50, 6s Medium-grained granite gneiss, 23 Miller, W. J., cited, 65 Mixed beds. Buck’s Bridge, 35 ; Theresa, 33 Mixed rocks, 14; from aluminous strata, 18 Moraine, 39 Moraine areas, terminal, 43 Ogdensburg dolomite, 36 Ordovician formations, 28 Paleozoic dolomite, 61 Paleozoic formations, 28, 55 ; resume, 58 Peneplains, 6 Phillips, A. H., acknowledgment to. 9 Pleistocene, resume, 59 Post-Pleistocene tilting, 56 Potsdam sandstone, 29 Power plants, 60 Precambrian formations, 9, 48 ; resume, 56 Pyrite, 62 Pyritous gneiss, 17 Pyroxene-bearing gneisses, 17 Pyroxenite, 16 Quartz mesh limestone, term defined, II Quartz schist, 10, ii Quartzite, 10; term defined, ii Quaternary formations, 36 Raquette river, 46 Rivers, 5 ; water power, 60 Roads, 7 Rocks, general geologic statement, 8 St Regis river, 47 Sandstones, 63 ; Heuvelton, 35 ; Pots- dam, 29 Schist, see Quartz schist Smyth, C. H. jr, cited, 62, 65 Smyth, C. H. jr & Buddington, A. F., cited, 16, 52, 65 Striae, 38, 42, 59 Structural geology, Paleozoic, SS ; Post-Pleistocene, 56 ; Precambrian. 48 Surface, 6 Swamp areas, 41 Talc, 61 Taylor, F. B., cited, 43, 65 Theresa mixed beds, 33 Till, 42 Topography, 5; division controlled by bed rock, 42; by glacial drift, 38 Towns, 7 Ulrich, cited, 33 Valley, circumferential, 42 Water power, 60 Winchell, N. H., cited, 65 98 INDEX MacClintock, Paul, acknowledgment to, 9 Martens, J. H. C., cited, 65 Martin, J. C, cited, 10, ii, 22, 41, 50, 65 Medium-grained granite gneiss, 23 Miller, W. J., cited, 65 Mixed beds. Buck’s Bridge, 35 ; Theresa, 33 Mixed rocks, 14; from aluminous strata, 18 Moraine, 39 Moraine areas, terminal, 43 Ogdensburg dolomite, 36 Ordovician formations, 28 Paleozoic dolomite, 61 Paleozoic formations, 28, 55 ; resume, 58 Peneplains, 6 Phillips, A. H., acknowledgment to. 9 Pleistocene, resume, 59 Post-Pleistocene tilting, 56 Potsdam sandstone, 29 Power plants, 60 Precambrian formations, 9, 48 ; resume, 56 Pyrite, 62 Pyritous gneiss, 17 Pyroxene-bearing gneisses, 17 Pyroxenite, 16 Quartz mesh limestone, term defined, II Quartz schist, 10, ii Quartzite, 10; term defined, ii Quaternary formations, 36 Raquette river, 46 Rivers, 5 ; water power, 60 Roads, 7 Rocks, general geologic statement, 8 St Regis river, 47 Sandstones, 63 ; Heuvelton, 35 ; Pots- dam, 29 Schist, see Quartz schist Smyth, C. H. jr, cited. 62, 65 Smyth, C. H. jr & Buddington, A. F., cited, 16, 52, 65 Striae, 38, 42, 59 Structural geology. Paleozoic, 5S ; Post-Pleistocene, =;6 ; Precambrian, 48 Surface, 6 Swamp areas, 41 Talc, 61 Taylor, F. B., cited, 43, 65 Theresa mixed beds, 33 Till, 42 Topography, 5; division controlled by bed rock, 42; by glacial drift, 38 Towns, 7 Ulrich, cited, 33 Valley, circumferential, 42 Water power, 60 Winchell, N. H., cited, 65 LEGEND 98 INDEX MacClintock, Paul, acknowledgment to, 9 Martens, J. H. C., cited, 65 Martin, J. C, cited, 10, ii, 22, 41, SO, 6s Medium-grained granite gneiss, 23 Miller, W. J., cited, 65 Mixed beds. Buck’s Bridge, 35 ; Theresa, 33 Mixed rocks, 14 ; from aluminous strata, 18 Moraine, 39 Moraine areas, terminal, 43 Ogdensburg dolomite, 36 Ordovician formations, 28 Paleozoic dolomite, 61 Paleozoic formations, 28, 55; resume, 58 Peneplains, 6 Phillips, A. H., acknowledgment to. 9 Pleistocene, resume, 59 Post-Pleistocene tilting, 56 Potsdam sandstone, 29 Power plants, 60 Precambrian formations, 9, 48 ; resume, 56 Pyrite, 62 Pyritous gneiss, 17 Pyroxene-bearing gneisses, 17 Pyroxenite, 16 Quartz mesh limestone, term defined, II Quartz schist, 10, ii Quartzite, 10; term defined, ii Quaternary formations, 36 Raquette river, 46 Rivers, 5 ; water power, 60 Roads, 7 Rocks, general geologic statement, 8 St Regis river, 47 Sandstones, 63 ; Heuvelton, 35 ; Pots- dam, 29 Schist, see Quartz schist Smyth, C. H. jr, cited. 62, 65 Smyth, C. H. jr & Buddington, A. F., cited, 16, 52, 65 Striae, 38, 42, 59 Structural geology. Paleozoic, 55 ; Post-Pleistocene, 56 ; Precambrian, 48 Surface, 6 Swamp areas, 41 Talc, 61 Taylor, F. B., cited, 43, 65 Theresa mixed beds, 33 Till, 42 Topography, 5; division controlled by bed rock, 42; by glacial drift, 38 Towns, 7 Ulrich, cited, 33 Valley, circumferential, 42 Water power, 60 Winchell, N. H., cited, 65