Bedrock geologic map of the Crown Point quadrangle, Essex County, New York, and Addison County, Vermont
<p>The bedrock geology of the 7.5-minute Crown Point quadrangle consists of deformed and metamorphosed Mesoproterozoic gneisses of the Adirondack Highlands…
Public-domain full text preserved in the Mountain Man Mining Library. Original source: pubs.usgs.gov.
Figure 19. Stratigraphic column for Paleozoic rocks showing the approximate thickness of map units and conodont biozones. Queries (?) in the conodont biozone column represent missing biozones or biozones not recognized. Dashed horizontal lines are approximate biozone boundaries. Wavy lines represent unconformities. Abbreviations: ft, feet; m, meters; na, not applicable. 200 ft (61 m) 175 ft (53 m) 250 ft (76 m) 225 ft (69 m) 400 ft (122 m) 200 ft (61m) 175 ft (53 m) 80 ft (24 m) 70 ft (21m) 450 ft (137 m) 1,000 ft (305 m) Osp Ogf Oo Ov Ocp Opi Ofc Ocu O w ti pt Stony Point Formation Glens Falls Limestone Orwell Limestone Valcour Limestone Crown Point Limestone Providence Island Dolomite Fort Cassin Formation Cutting Dolomite Whitehall Formation Ticonderoga Formation Potsdam Sandstone Ordovician Cambrian Upper Middle Lower Upper Middle(?) System Series Formation Map unit Thickness Iberville Formation (not shown on geologic map) na na Conodont biozone Rossodus manitouensis Macerodus diane Oepikodus communis Cahabagnathus sweeti Plectodina aculeata Belodina compressa ? ? ? KNOX UNCONFORMITY GREAT UNCONFORMITY Figure 17. Photograph (looking east) of the Crown Point iron furnaces in about 1901. Photograph from Barker (1942). Figure 16. Map of the Crown Point quadrangle, Essex County, New York, and Addison County, Vermont, showing abandoned mines and quarries with the principal commodity and related features; locations are also shown on the geologic map. 2 KILOMETERS 2 MILES Mine—Iron (Fe) and graphite (C) Quarry—Feldspar (f) and dolostone (d) EXPLANATION Breed (Fe) Kent (Fe) Butler (Fe) Vineyard (Fe) Hammond (Fe) Crown Point Spar (f) Rose Rock (f) Crown Point Towne (C) MASON (C) Buck Mountain Pond (C) d d Fe Fe d Site of wharf and furnaces Abandoned narrow gauge railroad (1872-1900) To Irondale and Hammondville Abandoned feldspar silos f A K E
H A M P A N 43°52'30" 44°00" 73°22'30" 73°30' Name of mine or quarry Mineral Resource Data System ID Principal reference Principal commodity Host rock and map unit Vineyard Butler Hammond Breed Kent Unnamed off Amy Hill Road Unnamed NW of White Church Towne Mason Buck Mountain Pond Crown Point Spar Company Rose Rock Unnamed near Worcester Pond Unnamed Unnamed Kirby (not located) Dibble Hollow (not located) Blye (not located) W033544 W033544 na na na na na W033561 W03353 W033559 W033549 W033541 na na na dep_id 10200235 dep_id 10127185 na Newland and Kemp (1908) Newland and Kemp (1908) Newland and Kemp (1908) Newland and Kemp (1908) Newland and Kemp (1908) na na Alling (1918) Alling (1918) Alling (1918) Tan (1966) Tan (1966) na na na Whitlock (1903) na Newland and Kemp (1908) Iron Iron Iron Iron Iron Iron Iron Graphite Graphite Graphite Feldspar Feldspar Feldspar Aggregate Aggregate Graphite Iron Iron Migmatitic biotite paragneiss (Ybg) and leucogranite gneiss (Ylg) Leucogranite gneiss (Ylg) Leucogranite gneiss (Ylg) Migmatitic biotite paragneiss (Ybg) and leucogranite gneiss (Ylg) Leucogranite gneiss (Ylg) Leucogranite gneiss (Ylg) Migmatitic biotite paragneiss (Ybg) and leucogranite gneiss (Ylg) Marble (Ym) Marble (Ym) Marble (Ym) Pegmatite (Yp) Pegmatite (Yp) Pegmatite (Yp) Dolostone (Opi) Dolostone (Ocu) Unknown Unknown Unknown Table 4. Mines and quarries in the Crown Point quadrangle, Essex County, New York, and Addison County, Vermont. [Unnamed mines or quarries are not in the Mineral Resources Data System database. Deposits that were not located in this study are not shown on the geologic map. Abbreviations: na, not applicable; NW, northwest] Table 1. Summary of U-Pb zircon ages from the Crown Point quadrangle, Essex County, New York, and Addison County, Vermont. [Abbreviations: na, not applicable; Ma, mega-annum (million years before present); i, igneous cores; rims, refer to metamorphic rims; SHRIMP-II, sensitive high resolution ion microprobe II (analyses at Geological Survey of Canada, Ottawa, Ontario); LA-MC-ICP-MS, laser ablation-multicollector-inductively coupled plasma-mass spectrometry (analyses at Arizona LaserChron Center, University of Arizona, Tucson, Arizona); U-Pb, uranium-lead. Latitude and longitude are in World Geodetic System 1984 (WGS 84) datum. Coordinates for the Sugar Hill pegmatite were corrected from Lupulescu and others (2011) by M. Lupulescu, New York State Geological Survey, unpublished data, 2019] Sample number Rock type and map unit Age, in Ma Method Source Longtitude Latitude CP-4049B CP-4055 CP-4049C CP-4049A na na Syenite within paragneiss (Ybg) at Vineyard mine Leucogranite (Ylg) at Butler mine Pegmatite (Yp) at Vineyard mine Magnetite ore at Vineyard mine Sugar Hill pegmatite (Yp) Crown Point Spar Company pegmatite (Yp) 1,152±7 Ma (i); 1,032±5 Ma (rims) 1,146±6 Ma (i); 1,053±7 (rims) and 1,007 Ma (rims) 1,034±5 Ma (i); 1,024±5 Ma (rims) 1,038±3, 1,004±4, 969±7 Ma 1,048±14 Ma 1,025±1 Ma SHRIMP-II SHRIMP-II SHRIMP-II SHRIMP-II LA-MC-ICP-MS LA-MC-ICP-MS J.N. Aleinikoff, U.S. Geological Survey, unpublished data, 2020 J.N. Aleinikoff, U.S. Geological Survey, unpublished data, 2020 J.N. Aleinikoff, U.S. Geological Survey, unpublished data, 2020 J.N. Aleinikoff, U.S. Geological Survey, unpublished data, 2020 Lupulescu and others (2011) Lupulescu and others (2011) 73.448343° 73.449047° 73.448673° 73.448343° 73.419391° 73.439075° 43.911702° 43.915455° 43.911628° 43.911702° 43.936162° 43.924028° Figure 1. Simplified geologic map of the Adirondacks, upstate New York, showing the location of the Crown Point quadrangle. Rocks in the Adirondack Lowlands are shown with lighter shades of the same colors as in the Highlands. Simplified from Rickard and others (1970) and Isachsen and Fisher (1970) with digital data from Dicken and others (2005). Inset map of the Grenville Province shows Mesoproterozoic inliers in northeastern North America; modified from Hibbard and others (2006). Abbreviation: CCSZ, Carthage-Colton shear zone. Undifferentiated rocks and sediments outside the Adirondacks Quaternary sediments Anorthosite-mangerite-charnockite-granite suite Leucogranitic (alaskitic) gneiss including the Lyon Mountain Granite Gneiss Biotite and (or) hornblende granitic gneiss, locally pyroxenic Charnockitic, mangeritic, granitic, syenitic gneiss with hornblende, pyroxene, and biotite; darkest shade indicates inequigranular texture including the Hawkeye Granite Gneiss from unit "" of Isachsen and Fisher (1970) EXPLANATION Anorthositic rocks Metagabbro Marble and calc-silicate rock Undifferentiated paragneiss and migmatite gneiss Amphibolite Tonalitic gneiss Fault Town 36 KILOMETERS 24 MILES QUEBEC NEW YORK VERMONT ONTARIO St. Lawrence River La ke
hamplain Lyon Mountain Port Henry Ticonderoga Plattsburgh Keene Glens Falls Carthage Lake Placid Hawkeye Marcy massif Adirondack Lowlands Adirondack Highlands Crown Point quadrangle h am p a n
Valle y SZ S Z Adirondack massif NY VT Grenville Province 43° 44° 45° 76° 75° 74° 73° G.J. Walsh 43°52'30" 44° 73°22'30" 73°30' INDEX TO GEOLOGIC MAPPING [Colors do not correspond to map unit colors] R.C. Orndorff 43°45' 43°52'30" 44° 44°07'30" 73°15' 73°37'30" 73°30' 73°22'30" INDEX TO 7.5' QUADRANGLES [Study area shown in red] CROWN POINT EAGLE LAKE PORT HENRY WITHERBEE GRAPHITE TICONDEROGA BRIDPORT ORWELL SNAKE MOUNTAIN Simplified surficial geologic map and lidar percent slope of the Crown Point quadrangle LIST OF MAP UNITS Artificial fill (Holocene) Undifferentiated waste rock piles and tailings (Holocene) Landslides (Quaternary) Undifferentiated glacial deposits (Quaternary) EXPLANATION OF MAP SYMBOLS Lidar percent slope—Steeper slopes are darker Shallow outcrop area—Large areas of exposed rock, or areas that are shallow to rock with thin glacial overburden Outcrops—Areas of exposed bedrock or closely spaced contiguous bedrock exposures examined in this study; some areas are enlarged to show location Contact—Approximately located af Qal Qls wt MAP LOCATION NEW YORK VT 1 MILE NATIONAL GEODETIC VERTICAL DATUM OF 1929 7000 FEET 1 KILOMETER SCALE 1:24 000 1/2 APPROXIMATE MEAN DECLINATION, 2022 TRUE NORTH 13 / ° MAGNETIC NORTH Geology mapped by Walsh (2016-2019) and Orndorff (2018-1019) Digital compilation by Walsh Edited by David A. Shields Base modified from New York State Department of Transportation, Crown Point, 1969, and modified from U.S. Geological Survey, Bridport, 1991 Lidar percent-slope from New York State Geographic Information Systems Clearinghouse and Vermont Center for Geographic Information Universal Transverse Mercator Projection, zone 18, North American Datum of 1983 1000-meter Universal Transverse Mercator grid ticks, zone 18 Point elevations shown are in feet 0% 1000% Qal Qal Qal Qal Qls Qls Qls Qls af Qls wt Qls Qls af af wt Qls wt wt Qls Qls wt Qls wt wt af Qls wt wt Qls af Qls Qls wt Qls Qls Qls Qls Qls af af Qls Qls Qls Qls Qls Qls Qls Qal Qls Qls Qal Qal Qal Qal Qal 4872000mN 621000mE 4860000mN 631000mE 73°30' 43°52'30" 43°52'30" 43°55' 43°57'30" 44°00' 43°55' 43°57'30" 44°00' 73°27'30" 73°25' 73°27'30" 73°25' 73°22'30" 73°22'30" 73°30' Buck Mountain Keeney Mountain TOWNER HILL ROAD WARNER HILL ROAD Fivemile Creek SECTION B-B´ SURFACE SURFACE Ylg Ylg Ylg Ylg Ylg Ybg Ybg Ybg Ybg Ybg Ysi Ysi Ysi Yggn Yggn Yggn Yggn Yggn Ya Ya Ya Ysi Ya Ya Ya Yma Yp Ym Ym Ya Ym Ym Ym Ym Ym Ym Unit Yma is mapped where the thick glacial overburden prevents separate mapping of units Ya and Ym. SEA LEVEL 1,000 METERS 100 meters 328 feet Surficial deposits are not shown METERS ' NO VERTICAL EXAGGERATION NORTHWEST SOUTHEAST SEA LEVEL 1,000 LAKE CHAMPLAIN NEW YORK VERMONT Buck Mountain Miller Mountain Keeney Mountain NEW YORK VERMONT STATE ROUTE 22 AND 9N THE VINEYARD ROAD DELAWARE AND HUDSON RAILROAD LAKE SHORE ROAD STATE ROUTE 22 AND 9N VINEYARD ROAD FAULT LAKE CHAMPLAIN FAULT SCHOOLHOUSE BAY FAULT SECTION C-C´ Ysi Ysi SURFACE SURFACE Yggn Ybg Ybg Ybg Ybg Yma Yggn Ysi O w O w Ocu Ocu Ov Oo Ov Oo Ofc Ofc pt ti Opi Ocp Opi Ocp Yu pt ti Yu Osp Ogf Ogf Osp Oib Oib Ybg Ybg Ybg Ybg Ybg Ylg Ylg Ylg Ylg Ylg Ylg Ylg Ylg Ybg Ym Ya Yp Ya Ya Ya Yrbg Ym Ym Ym Ylg Ylg Ylg Ylg Ylg Ylg Ya B 1,000 1,000 METERS 100 meters 328 feet Surficial deposits are not shown METERS B ' NO VERTICAL EXAGGERATION WEST EAST SEA LEVEL 1,100 1,000 1,000 SEA LEVEL 1,100 Bulwagga Mountain WHITE CHURCH ROAD BURDICK ROAD LONG POINT ROAD LAKE SHORE ROAD DELAWARE AND HUDSON RAILROAD NEW YORK VERMONT LAKE CHAMPLAIN STATE ROUTE 22 AND 9N Yhg DIP SLOPE SURFACE SURFACE The Iberville Formation is not mapped but is projected in the air based on an approximate thickness of 1,000 feet (305 meters) from Welby (1961). VINEYARD ROAD FAULT LAKE CHAMPLAIN FAULT Ybg Ybg Ybg Ylg Ylg Ybg Ybg Ybg Ya Ybg Ylg? Yhg Ybg Ybg Oib Oib Osp Osp Ogf Ogf Ofc Ofc Opi Ocu Yu O w O w pt Yu pt ti ti Ylg Ylg Yhg Ylg Ylg Ylg Ylg Ylg Ylgt Oo Oo Ov Ov Ocp Ocp Ocu Opi A SEA LEVEL 1,000 SEA LEVEL 1,000 METERS 100 meters 328 feet Surficial deposits are not shown METERS A ' NO VERTICAL EXAGGERATION WEST EAST Using "Layers," turn on the bedrock map layer and turn off the surficial map layer to view concealed bedrock map units Geology mapped by Walsh (2016-2019) and Orndorff (2018-1019) Digital compilation by Walsh and E.A. Crider Edited by David A. Shields Base modified from New York State Department of Transportation, Crown Point, 1969, and modified from U.S. Geological Survey, Bridport, 1972 Universal Transverse Mercator Projection, zone 18, North American Datum of 1983 1000-meter Universal Transverse Mercator grid ticks, zone 18 MAP LOCATION NEW YORK VT 1 MILE CONTOUR INTERVAL 20 FEET NATIONAL GEODETIC VERTICAL DATUM OF 1929 7000 FEET 1 KILOMETER SCALE 1:24 000 1/2 APPROXIMATE MEAN DECLINATION, 2022 TRUE NORTH 13 / ° MAGNETIC NORTH Ysi Ysi Ysi Yp Ym Ocu Ofc Ymig Ymig Yp Ylg Ya Ysi Ysi Ym Ysi Ysi Ym Ym Ya Yp Ysi Ym Ym Yggn Ybg Yp Yp Yp Ya Ya Ym Yp Ybg Ym Ybg Ylg Ylg Ya Ylgt Ya Yp Ylg Ylg Ylg Yp Yp Ylg Ylg Ysi Ofc Yp Yggn Ym Ya Ya Ya Ya Ya Yggn Ylgg Yggn Ym Ya Yp Yp Ylgt Ofc Ya Yrbg Ym Yggn Ocp Yrbg Ysi Ysi Ya Ya Ylgt Ylg Ylg Ym Yggn Ya Ym Ya Yggn Ym Ygb Ym Ocp Ocp Ylg Yp Yggn Ysi Ya Ybgg Ym Ybgg Ylg Ylg Ybg Ocu Opi Ylg Ya Oo Ylg Ybgg Ylg Ybg Ylg Ylg Ylg Yggn Ya Ya Ya Ya Ybg Ybg Ybg Yp Ybg Yp Yp Ym Yp Yp Yp Ybg Ybg Ybg Ya Ya Ybg Ybg Yp Ygb Yggn Ylg Ylg Ya Yggn Ya Ya Ya Ylg Yp Yp Yp Ylgt Yma Ylg Yggn Yggn Ybg Yp Yma Ylg Ya Ysi Ym Yp Ya Ya Ya Ylg Ya Ya Ya Ya Ybg Ya Ym Ym Ya pt Ycs Ybg Ylgt pt Ym Ym Ya Ylgt Ya Ybg Ybg pt pt Yp Ya Ya Ylg Ylg Ybg Ylgt Ybg Ylgt Ya Ylgt pt Yp Ylgt Ybg Ybg Osp Ya Ya Yhg Ylgt Ylgt Ya Ya Ya Ybg Ym Yp Ylg Ylg Ylg Ybg Ya Ya Ybg Ybg Ybg Ylgt Ya Ybg Ya Ylg Ybg Ybg Ybg Ya Ylgt Ylg Ocu Ya Ylg Ybg Ybg Ybg Ybg Ylg Yhg Ya Ylg Ygb Ybg Ylg Ya Ylg Yhg Ylg Ybg Ylg Ocu Opi Opi Ocp Opi Ylg Ybg Ofc Ofc Opi Ofc Osp Osp Osp Ogf Ogf Ogf Ogf Ogf Ogf Osp Osp Ogf Oo Oo Ocp Ov Ya Ym Ybg Yp Ofc Opi Osp Osp Osp Ocp Ocp Ocp Ocp Ogf Ybg Ylg Ylg Ylg Ylg Ybg Ybg Ybg Ybg Ybg Ylg Ylg Ybg Yggn Ysi Ysi Ylg Ybg Ylg Ybg Ybg Ylg Ylg Ym Yggn Osp Osp Osp Osp Ofc Ofc Ofc Ofc Ocu Ocu Osp Osp Oo Oo Opi Opi Opi Opi Opi Osp Ym O w ti pt ti Ylg Ybg Yp Yp Ylg Qal Qls Qls Qls Qls Qls af wt Qls Qls af af wt Qls wt wt Qls Qls Qls wt wt af Qls wt wt Qls af Qls Qls wt Qls Qls Qls Qls Qls af af Qls Qls Qls Qls Qls Qls Qls Qls Qal Qls Qls Qls Qls Qal Qal Qal Qal Qal Qal Qal Qal Qal Qal Qal Qal Qal Qal Qal Qal Qal Qal Qal KE ENE Y MOUN TAI N SYN F O RM Zd Zd Zd Zd Zd Zd Zd Zd Zd Zd Zd Zd Zd Zd Zd Zd Zd Zd M M LEONARD BAY FAULT LAKE C HAMPLAIN FAULT VINEYARD ROAD FAULT N E YARD ROAD FAU LT VINEYARD ROAD FAULT SCH OO L HO USE B AY FA ULT SCHOOL HOUSE BAY FA UL T LAKE CH AMPLAI N FAU LT CP-3000 CP-3072 CP-3075 CP-3047 CP-3041 Crown Point Spar Company Towne Hammond Kent Breed Buck Mountain Pond Vineyard Butler Rose Rock Mason 1,025±1 Ma 1,048±14 Ma Ticonderoga well field Street Road delta Site of abandoned wharf and iron furnaces Sil A A ' B B ' ' 4872000mN 621000mE 4860000mN 631000mE 73°30' 73°30' 43°52'30" 43°52'30" 43°55' 43°57'30" 44°00' 43°55' 43°57'30" 44°00' 73°27'30" 73°25' 73°27'30" 73°25' 73°22'30" 73°22'30" ISSN 2329-132X (online) ://doi.org/10.3133/sim3491 Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government For sale by U.S. Geological Survey, Box 25286, Denver Federal Center, Denver, CO 80225; ://store.usgs.gov; 1-888-ASK-USGS (1-888-275-8747) Suggested citation: Walsh, G.J., Orndorff, R.C., and McAleer, R.J., 2022, Geologic map of the Crown Point quadrangle, Essex County, New York, and Addison County, Vermont: U.S. Geological Survey Scientific Investigations Map 3491, 1 sheet, scale 1:24,000, 44-p. pamphlet, ://doi.org/ 10.3133/sim3491. Geologic Map of the Crown Point Quadrangle, Essex County, New York, and Addison County, Vermont By Gregory J. Walsh, Randall C. Orndorff, and Ryan J. McAleer DESCRIPTION OF MAP UNITS [Minerals described in order of increasing abundance where hyphenated. Representative photographs of map units are included in appendix 1] HOLOCENE AND QUATERNARY DEPOSITS Artificial fill (Holocene)—Includes large areas of fill associated with the airport, landfill, paper mill, and the railroad at Gilligans Bay. The unit was mapped with light detection and ranging (lidar) and ground observations. Small areas of fill associated with roads and bridges are not mapped Undifferentiated waste rock piles and tailings (Holoocene)— Areas of filled land or mine dumps related to historic mines. The unit was mapped with lidar and ground observations Landslides (Holocene and Quaternary)—Areas of noted landslides. The unit was mapped with lidar and ground observations. Deeply incised stream channels of Putnam Creek and its tributaries are not mapped, though this area contains thick glacial deposits with steeply eroded banks, which may contain landslides that were not examined in detail in this study Undifferentiated glacial deposits (Quaternary)—Large areas of the Champlain Valley are covered in thick glacial deposits, which may include undifferentiated till, lake sediments, beach deposits, terraces, and deltas; these areas are not subdivided on the maps. On the lidar map, Qal is shown as transparent yellow so the lidar percent-slope can be seen beneath it. See De Simone and others (2008) and Rayburn (2004) for a discussion of the surficial geology which has yet to be mapped in this quadrangle. The large Street Road delta is exposed in Ticonderoga between Routes 7 and 9N/22, with bottomset sand beds to the east and topset beds in sand and gravel to the west; the topset-foreset contact is exposed at an elevation of 525 feet (ft) (De Simone and others, 2008). Limited publicly available water well data shows that the overburden thickness locally exceeds 200 feet. Unpublished well logs for eight water wells drilled for the new Ticonderoga well field along Street Road (approximate location shown on the map) indicate depth to bedrock as >250, 245, >235, >59, and 39 meters [m]) (F. Bickford, HydroSource Associates, written communication, 2018) PALEOZOIC SEDIMENTARY ROCKS [The stratigraphic column is shown in figure 19] Iberville Formation (Upper Ordovician)— Dark-gray shale with thin discontinuous beds of crossbedded and graded dolomitic siltstone. Present only in cross sections A-A' and B-B' Stony Point Formation (Upper Ordovician)—Dark-gray to black, light-gray- to locally tan-weathering, calcareous shale interbedded with dark-gray to black, thin-bedded shaly limestone. The basal contact is placed at the transition from fossiliferous thin-bedded limestone of the Glens Falls Limestone to thin-bedded shaly limestone interbedded with calcareous shale. The unit is well exposed from Girards Bay to Jones Dock on the eastern shore of Lake Champlain. Thickness of the unit is undetermined due to an incomplete section in the map area. Welby (1961) estimated the thickness of the unit at about 1,000 ft (305 m) in Vermont where the Stony Point Formation is overlain by the Iberville Formation (Oib); the Iberville Formation is shown only in cross sections A-A' and B-B' where it is projected in the air Glens Falls Limestone (Upper Ordovician)—Dark-gray to black, bluish-gray weathering, thin- to medium-bedded, fossiliferous, grainstone limestone with argillaceous partings interbedded with dark-gray shaly limestone. The basal contact is placed at the transition from medium-bedded limestone of the Orwell Limestone to the interbedded, thin-bedded limestone and shaly limestone of the Glens Falls Limestone. The unit grades locally upward into sooty-weathering shaly limestones containing beds rich in fragments of the trilobite Cryptolithus. The unit is well exposed on the eastern shore of Lake Champlain from just north of West Bridport, Vt., to Leonard Bay. Thickness is estimated at 450 ft (137 m) Orwell Limestone (Upper Ordovician)—Dove-gray weathering, black to dark-gray, medium-bedded, fine-grained limestone containing black chert nodules. Samples from the lower part of the formation contain conodonts of the Belodina compressa Biozone (fig. 19, table 2). The lower contact is not exposed in the quadrangle. The unit is best exposed north of the Crown Point quadrangle in the Port Henry quadrangle at Crown Point State Historic Site, N.Y., where the lower contact is above the highest dolostone of the Valcour Limestone. A quartz arenite occurs several feet above the contact with the Valcour Limestone. Thickness is estimated at 70 ft (21 m) Valcour Limestone (Upper Ordovician)—Dark- to light-gray, thick-bedded, medium-grained limestone, dolomitic limestone, and dolostone. Dolostone weathers light brown. The lower contact is not exposed in the quadrangle. The unit is best exposed north of the Crown Point quadrangle in the Port Henry quadrangle at Crown Point State Historic Site, N.Y., where the lower contact is placed at the base of the lowest dolostone. Thickness is estimated at 80 ft (24 m) Crown Point Limestone (Upper and Middle Ordovician)—Medium dark-gray, thin- to medium-bedded, coarse-grained fossiliferous limestone with very dark gray argillaceous partings. Basal beds are very light gray weathering, medium- to dove-gray, thick-bedded mudstone limestone. Contains the diagnostic gastropod Maclurites. Upper beds contain quartz and feldspar sand grains. The contact with the underlying Providence Island Dolomite is placed at the base of high-calcium mudstone overlying fetid dolostone. The upper part of the unit is best exposed north of the Crown Point quadrangle in the Port Henry quadrangle at Crown Point State Historic site, N.Y., Thickness is estimated at 175 ft (53 m) Providence Island Dolomite (Middle and Lower(?) Ordovician)— Tan and light-gray weathering, gray to light-gray, laminated dolostone with interbedded gray limestone, noncalcareous shale, and argillaceous partings. Has "beeswax-scored" and "butcherblock" surfaces on weathered surfaces. Samples for conodonts were barren. The lower contact is not exposed in the quadrangle. The unit is well exposed in an abandoned quarry just east of NY State Route 9N and north of Shore Airport Road. Thickness is estimated at 200 ft (61 m) Fort Cassin Formation (Lower Ordovician)—Yellowish-gray, orangish-gray, and tan weathering, gray, medium- to thick-bedded dolostone and minor dolomitic limestone. Weathered surfaces have "butcherblock" patterns. The conodont Oepikodus communis Biozone (fig. 19, table 2) occurs within the Fort Cassin Formation. The lower contact is not exposed in the quadrangle. The unit is best exposed along the western shore of Lake Champlain between Hickock Point and Porters Marsh. Thickness is estimated at 400 ft (122 m) Cutting Dolomite (Lower Ordovician)—Light-gray to light-tan weathering, medium-gray to dark-olive-gray, thick-bedded, crystalline dolostone, sandy dolostone, and dolomitic sandstone. Well crossbedded in places. Weathered surfaces have butcher-block patterns. The lower contact is placed at the transition from massive, crystalline dolostone of the Whitehall Formation to quartz sand dolostone of the Cutting Dolomite. The basal sandstone that Rodgers (1937) described resting unconformably on the Whitehall Formation was not observed in the Crown Point quadrangle. However, the lower part of the formation is crossbedded quartz sand with dolomitic cement; sand grains weathering in relief. The conodont Rossodus manitouensis Biozone occurs within the Cutting Dolomite (fig. 19, table 2). The unit is exposed in an abandoned quarry on the east side of NY State Route 9N south of the intersection with NY State Route S185 in the northern part of the quadrangle. The unit is best exposed in the northern part of the Ticonderoga quadrangle along Shore Airport Road just north of NY State Route 22/74. Thickness is estimated at 225 ft (69 m) Whitehall Formation (Lower Ordovician and Upper Cambrian)— Light- to brownish-gray and pinkish, thick-bedded to massive, medium to coarsely crystalline (sugary) dolostone with local sand and limestone interbeds and black chert nodules. The unit is siliceous in places with a fetid odor from fresh surfaces. The lower contact with the Ticonderoga Formation is gradational and placed where sandy dolostone grades upward to dark-gray crystalline dolostone of the Whitehall Formation. The unit is well exposed at Sheepshead Island, on the western shore of Lake Champlain west and southwest of the island, and at railroad cuts in the same area off Rock Way (the road name is not on the maps). Thickness is estimated at 250 ft (76 m) Ticonderoga Formation (Upper Cambrian)—Brownish-gray, yellowish-gray, buff, to light-gray weathering, dark- to medium-gray, medium- to thick-bedded, cherty and sandy, fine- to medium-grained dolostone with quartzose dolostone and pebbly dolomitic sandstone interbedded with quartz sandstone. Chert occurs as black nodules. Sandy dolostone beds weather yellowish gray. Quartz grains are subrounded to rounded and frosted. The base of the unit is gradational and marked by decreasing sandstone of the Postsdam Sandstone to dolomite and sandy dolomite of the Ticonderoga Formation and placed at the first significant dolostone beds. Locally, the unit contains worm burrow trace-fossils. The unit is well exposed on the western shore of Lake Champlain 0.5 kilometers (km) south of Sheepshead Island. Thickness is estimated at 175 ft (53 m) Potsdam Sandstone (Upper and Middle(?) Cambrian)—Gray to greenish-gray, locally maroon, tan, or rusty weathering, poorly sorted, subangular to subrounded, coarse- to medium-grained, well-bedded sandstone, with coarse sandstone and pebble conglomerate near the base of the unit. Bedding thickness varies from meter- to decimeter-scale and is locally massive and crossbedded. Contains abundant ripple marks. The unit grades upwards from arkosic sandstone to quartz arenite interbedded with dolostone and dolomitic sandstone. The basal contact is an unconformity overlying Mesoproterozoic rocks. The unit is well exposed on the western shore of Lake Champlain 0.4 miles (mi) (0.6 km) south of Sheepshead Island, and along Putnam Creek from Crown Point Center to an elevation of about 490 ft (149 m). The basal unconformity is well exposed at a waterfall on Putnam Creek in Crown Point Center at an elevation of about 300 feet (91 m). Thickness is extremely variable (based on the paleotopographic surface) and is as much as 200 ft (61 m) PROTEROZOIC IGNEOUS AND METAMORPHIC ROCKS NEOPROTEROZOIC IGNEOUS ROCKS Mafic dikes (Ediacaran)—Dark-gray to olive-green or black, black to dark-reddish-green or rusty maroon weathering, aphanitic to phaneritic, equigranular diabase dikes. Dikes may show chilled margins, and thicker dikes are medium to coarse grained in the center and consist mostly of clinopyroxene and plagioclase exhibiting an ophitic texture, with minor amounts of olivine altered to serpentine, chlorite, biotite, opaques, and uralite alteration. Measured dikes range in thickness from 0.03 to 4 m. The steeply dipping dikes trend northeast with a mean trend of 60°±6° (fig. 11) and crosscut every Proterozoic rock unit, but are not found in the Paleozoic rocks, and thus predate the basal unconformity. Nineteen measured dikes are shown with strike-and-dip symbols. The dikes are also shown as mapped lines extrapolated for as much as 4 km where the linear trend is clearly visible in several places in the lidar percent-slope map, especially on Bulwagga Mountain and the north slope of Buck Mountain. A typical dike is well exposed at several places in the steep stream canyon on the west slope of Bulwagga Mountain, 0.7 km west of the junction of Route 9N/22 and 185 (the latter is labeled Route S on the base map). A more readily accessible dike measuring 0.4-m thick is located at a roadcut on Route 9N/22, 0.55 km north of Spar Mill Bay (point CP-5060 in the database) MESOPROTEROZOIC IGNEOUS ROCKS Undifferentiated rocks (Mesoproterozoic)—Rocks concealed beneath glacial deposits on the map or shown in cross-sections A-A' and B-B' at depth. Late- to Post-Tectonic Igneous Rocks Pegmatite (Mesoproterozoic)—Pink and white to white, coarse to very coarse grained, hornblende-biotite granite pegmatite and clinopyroxene granite pegmatite. Magnetite is common. Locally, the unit contains garnet and graphite. May contain epidote, allanite-Ce, polycrase-Y, titanite, zircon, and fluorite; the feldspars are microcline and albite (Lupulescu and others, 2011). The pegmatites are reportedly low in lithium but elevated in rare earth elements (Tan, 1966; Lupulescu and others, 2012). In addition to quartz and feldspar, Newland (1921) reported biotite, chlorite, hornblende, titanite, magnetite, zircon, tourmaline, pyrite, chalcopyrite, and allanite from the Crown Point Spar Company quarry on Breed Hill, where large crystals of biotite, hornblende, and garnet occur in the wall rock (Tan, 1966). Tan (1966) classified the bodies at the Crown Point Spar Company quarry and the Rose Rock quarry as hornblende-biotite pegmatites. Clusters of allanite locally occur at the Crown Point Spar Company quarry (Tan, 1966), and coincide at one place in this study with elevated gamma radiation readings above background using a portable detector. Other pegmatites locally showed similar elevated gamma radiation readings (see section on Gamma Radiation Measurements). Well-exposed mapped pegmatite occurs at the Crown Point Spar Company and Rose Rock quarries (along Route 9N/22 near Spar Mill Bay) and on the west-facing cliffs on the southwest side of Miller Mountain where it is undifferentiated yet abundant Syn- to Post-Tectonic Igneous Rocks Lyon Mountain Granite Gneiss (Postel, 1952) Leucogranite gneiss (plus Ylgg) (Mesoproterozoic)—Pink to white, light-gray to white and locally rusty tan weathering, medium-grained, equigranular, variably well layered and gneissic to poorly foliated, undifferentiated quartz-plagioclase-alkali feldspar rocks consisting of microperthite granite, microcline granite, quartz syenite, alkali feldspar granite (alaskite), syenogranite, monzogranite, and quartz-albite rock with ubiquitous, as much a 5 percent magnetite, and <2-5 percent biotite, hornblende, or clinopyroxene. K-feldspar may exhibit rims of plagioclase. The amounts of biotite, hornblende, and clinopyroxene vary and most samples are dominated by only one of the minerals. In many places, magnetite is the only mafic mineral visible in hand sample. The granite locally contains accessory garnet, chlorite, titanite, titanomagnetite, apatite, and trace amounts of zircon, monazite, and allanite. Garnet is locally abundant, especially near contacts with paragneiss, and in one place on the south slopes of Buck Mountain it was mapped separately as leucogranite gneiss with garnet (Ylgg). Layer-parallel and less abundant crosscutting veins of magnetite and quartz locally occur. Secondary epidote is locally present as veins and microscopic grains and saussurite alteration of calcic plagioclase; this alteration locally imparts a pale-greenish-gray color to the rock. The unit is well exposed and commonly forms resistant, glacially rounded blocky outcrops. The leucogranite is well layered at the centimeter (cm)- to m-scale and varies in modal grain size and primary mafic mineralogy between individual, submeter thick layers, but it is generally homogenous at the map scale; no systematic variation could be mapped. The unit contains both layer-parallel and crosscutting magnetite-bearing clinopyroxene or biotite granitic pegmatite. The unit locally contains partially assimilated xenoliths and screens of amphibolite (Ya) associated with mafic respite; xenoliths and screens of migmatitic paragneiss, quartzite, and metagabbro are less common. Contacts between unit Ylg and adjacent paragneiss units, especially Ybg, are gradational and marked by a transitional zone of migmatization (unit Ylgt). Unit Ylg contains rare magnetite-quartz-sillimanite nodules at one place on the southeast slope of Buck Mountain in Ticonderoga (labeled "Sil" on the map), which are interpreted as metasomatic in origin (McLelland and others, 2002). Adjacent to regions of magnetite ore there is evidence for metasomatic alteration by potassic and sodic fluids (Valley and others, 2009, 2011), and the granite near ore deposits is commonly bleached white and consists of a magnetite-quartz-albite assemblage Transitional migmatitic paragneiss and Ylg (Mesoproterozoic)— Very complex, banded pink, white, dark-gray, black, brown, and green, well-layered stromatic migmatite consisting of paragneiss (Ybg) with increasing amounts of pink and white leuocosome in the host paragneiss towards masses of Ylg. The transitional unit contains discrete pods, sills, lit-par-lit bands and irregular bodies of leucogranite and abundant segregations and megacrysts of clinopyroxene, hornblende, and microcline, and local concentrations of magnetite-hornblende-clinopyroxene in grains, boudins, and pods. This transitional border was noted but not mapped by Walton (1966a, b). It locally contains retrograde mineral assemblages of saussuritized plagioclase, biotite, hornblende, and clinopyroxene broken down to chlorite and (or) actinolite, and paleosome containing greenish alteration assemblages of chlorite, epidote, albite, scapolite, and appreciable amounts of pegmatite too small to map separately. The composition and modal mineralogy vary within individual exposures, and the unit is well layered to massive. Marble is coarse grained, well annealed, and contains coarse (up 1 cm) quartz in recrystallized masses that compose <15 percent of the rock, but weather in high relief. Medium- to coarse-grained clinopyroxene (diopsidehedenbergite), calcite, and dolomite crystals are commonly present. The amount of flake graphite (up to 2 cm) varies between to 30 percent and is variable on the cm to m scale. Varying accessory phases include graphite, scapolite, phlogopite-biotite, plagioclase, microcline, hornblende, wollastonite, olivine, diopside, garnet, hornblende, molybdenite, tremolite, pyrite, tourmaline, and titanite. Faults and fractures locally contain, at least in one place, white to light-gray asbestiform fibrous minerals (fig. 14). Alteration products of silicates include chlorite, talc, tremolite, actinolite, serpentine as asbestiform chrysotile-antigorite, sericite, and zoisite. Pale-green to gray, rusty weathering, calc-silicate gneiss is layered on the cm- to decimeter-scale, and consists of varying proportions of diopside, talc, tremolite, quartz, and dolomite with accessory tourmaline, titanite, and pyrite. Thick recrystallized marble horizons may contain foliated and locally folded tectonic rafts of adjacent units, especially quartzite, amphibolite, and paragneiss. This unit exhibits distinctive alternating resistant and highly recessive layers due to varying amounts of quartz and or calc-silicate minerals. The marble and calc-silicate rocks are interpreted as end-members of the same metasedimentary unit. The unit is well exposed at Mine Hill, at the Buck Mountain Pond Property Mine in Ticonderoga. The unit may correlate with units Y2dm, Y2cs, and Y2m in Vermont (Ratcliffe and others, 2011) Amphibolite, marble, and calc-silicate gneiss member (Mesoproterozoic)—Interlayered amphibolite, marble, and calc-silicate gneiss. The unit is mapped where the exposure is insufficient, or end-members are so complexly interlayered at a fine scale, to prohibit separate mapping of members Ya and Ym Calc-silicate gneiss member (Mesoproterozoic)—Light-green, white and gray to tan and earthy yellowish-brown or rusty weathering, medium-grained, epidote-tremolite-quartz-diopside calc-silicate gneiss to granofels. The unit contains accessory plagioclase, tremolite-actinolite, magnetite, chlorite, and apatite, and is dominated by a retrograde mineral assemblage, where plagioclase is saussuritized and diopside is replaced by tremolite-actinolite and epidote. The unit is layered within Ybg; its size is exaggerated on the map to show the location. The unit is mapped in only one place where it is well exposed and extends from under the power lines to along the west side of Route 9N/22, southwest of Sheepshead Island. Similar greenish calc-silicate rocks occur elsewhere in unit Ybg but are not mapped separately. The unit may correlate with unit Y1,2be in Vermont (Ratcliffe and others, 2011) Amphibolite gneiss member (Mesoproterozoic)—Massive to well-foliated, dark-green to black, gray weathering, medium-grained, amphibolite consisting of hornblende-plagioclase gneiss or pyroxene-hornblende-plagioclase gneiss. Where pyroxene is present, clinopyroxene is always part of the assemblage with or without orthopyroxene. Garnet is common and abundant in many places. Locally, the unit contains biotite; microcline and quartz are present locally where the rock is migmatitic. Unit Ya is interlayered within units Ybg, Ysi, and Ym, and the layering is probably primary. The unit locally occurs as xenoliths or screens in units Ylg, Yhg, and Yggn. Amphibolite gneiss also occurs along the margins of metagabbro bodies but it is not mapped separately in these places at the scale of the map. The amphibolite is locally interlayered with marble and calc-silicate gneiss at a scale too small to map. The unit is well exposed on Keeney Mountain and Mine Hill in the core of the Keeney Mountain synform. The unit may correlate with units Y2a and Y1a in Vermont (Ratcliffe and others, 2011) EXPLANATION OF MAP SYMBOLS Contact—Approximately located; dotted where concealed. In cross section, dotted where projected above the ground surface; projections are based on structural measurements of surface exposures Outcrops—Areas of exposed bedrock or closely spaced contiguous bedrock exposures examined in this study; some areas are enlarged to show location FAULTS [Approximately located; dotted where concealed. In cross section, dotted where projected above the ground surface. Listed from youngest to oldest] Brittle fault (Mesozoic or Paleozoic)—Steeply dipping, dotted where concealed. Locally characterized by cataclasite, breccia, and veins; bar and ball on downthrown side, arrows show lateral offset where known Ductile shear zone (Mesoproterozoic)—Characterized by penetrative mylonitic textures with quartz ribbons and deformed feldspar; dotted where concealed; arrows indicate relative motion. Shear zones are characterized by upper amphibolite facies metamorphic assemblages that are syn- to post-pegmatite emplacement. Only one shear zone was mapped in the area, on the southern flank of Bulwagga Mountain. Similar structures occur at outcrop scales, and they are shown with strike and dip symbols. M, Mesoproterozoic FOLDS [Symbols show trace of axial surface and direction of dip of limbs; location is known] Axial trace of dome-stage F3 fold (Mesoproterozoic)—Associated with the Kenny Mountain synform and related structures Antiform Synform Overturned synform MINOR FOLDS [Folds in the Mesoproterozoic rocks; listed from youngest to oldest] Strike and dip of D4 shear bands—Includes axial surface of related minor folds; locally filled with pegmatite (Yp) Inclined, sinistral Inclined, dextral Strike and dip of F4 axial surface—Includes minor open fold or plane of boudinage; locally filled with pegmatite (Yp) Inclined Vertical Strike and dip of F3 axial surface—Includes minor open to tight fold; locally filled with pegmatite (Yp) and rarely expressed as a nonpentrative cleavage; arrow, if present, shows bearing and plunge of hinge line of fold Inclined Vertical Strike and dip of inclined F2 axial surface—Includes minor tight to isoclinal fold; locally filled with pegmatite (Yp); arrow, if present, shows bearing and plunge of hinge line of fold PLANAR FEATURES [Symbols may be combined; point of intersection shows location of measurement; listed from youngest to oldest] Strike and dip of inclined bedding in Paleozoic rocks Strike and dip of mafic dike (Zd) (Ediacaran) Inclined Vertical Strike and dip of quartz vein (Mesoproterozoic)—Locally common in the leucogranite gneiss (Ylg); may contain feldspar, epidote, magnetite, hematite, and calcite. Quartz-carbonate veins occur in the Paleozoic rocks but were not mapped Inclined Vertical Strike and dip of inclined pegmatite dike or sill (Yp) Strike and dip of inclined leucogranite sill (Ylg) FOLIATION [Symbols may be combined; point of intersection shows location of measurement; listed from youngest to oldest] Strike and dip of inclined cleavage in Paleozoic rocks (Ordovician)—Shown only in the Stony Point Formation Strike and dip of S2 gneissosity (Mesoproterozoic)—The most conspicuous foliation in the Mesoproterozoic rocks; includes the layer-parallel foliation in the Lyon Mountain Granite Gneiss, which may, in part, be related to flow banding and emplacement Inclined Vertical Strike and dip of inclined S1 gneissosity (Mesoproterozoic)— Foliation is parallel to compositional branding in paragneiss. The S1 foliation predates the Lyon Mountain Granite Gneiss LINEAR FEATURES [Symbols may be combined; point of intersection shows location of measurement; listed from youngest to oldest] Bearing and plunge of paleocurrent—From ripple marks in the Potsdam Sandstone Bearing and plunge of F3 minor fold axis—Associated with dome-stage folds, locally parallel to aligned nodules of sillimanite and quartz Bearing and plunge of L2 intersection lineation—Intersection between the S1 and S2 foliations Bearing and plunge of F2 minor fold axis—Fold axis of tight, isoclinal, or rootless fold associated with S2 Bearing and plunge of L2 mineral lineation—Aggregate lineation or grain lineation associated with the S2 foliation; consists of quartz, biotite, hornblende, or sillimanite OTHER FEATURES Abandoned narrow gauge railroad Abandoned quarry or mine—Abandoned quarries occur in Mesoproterozoic pegmatite bodies and in the Paleozoic carbonate rocks. Abandoned iron mines occur in Mesoproterozoic migmatitic biotite gneiss (Ybg) and the Lyon Mountain Granite Gneiss (Ylg). The locations of the quarries and mines are shown on the geologic map and in figure 16 Quarry Mine Conodont sample location—Shows sample number from table 2 Gamma radiation point—Shows location where a portable radiation detector measured more than two times the background radiation Geochronology sample location—Shows uranium-lead (U-Pb) zircon age of pegmatite (Yp) in Ma (mega annum, million years before present). U-Pb ages from the Sugar Hill pegmatite (1,048±14 Ma) and the Crown Point Spar Company pegmatite (1,025±1 Ma) are from Lupulescu and others (2011). Geochronology samples collected from the Vineyard and Butler mines (J.N. Aleinikoff, U.S. Geological Survey, unpublished data, 2020) are not shown individually on the geologic map for cartographic reasons; location coordinates of samples are provided in table 1 and the database. All sample ages are also provided in table 1 Kettle on Street Road delta quartz. This migmatite zone has not previously been mapped in the Adirondack Highlands but may correlate with what has informally been called the "Lyon Mountain Granite intrusion breccia" by McLelland and others (Stop 3, 2011) near Putnam Station, New York. On the map, we locally show the transitional migmatitic unit where it can be mapped in zones up to a few hundred meters wide along the contacts between Ylg and Ybg. We also show it mapped in places where the exposure is insufficient or end members (Ylg or Ybg) are so complexly interlayered at a fine scale to prohibit separately mapping either end member. Similar migmatitic rock occurs along the contacts with Ylg in most places, but it was difficult to separate all occurrences at the scale of the map. Areas within Ybg may contain transitional migmatitic rocks matching this description, but they are not mapped at all places due to the complexity and the challenge of mapping this unit at the scale of the map; such areas are noted in the GIS database. A typical exposure of the transitional unit occurs in Crown Point along Route 9N/22 at the Sacred Heart Church (the church symbol is shown on the map, across the street from the cemetery labelled "Sacred Heart Cem") Metagabbro (Mesoproterozoic)—Dark-green to black, dark-gray to tan weathering, massive to weakly foliated, medium- to coarse-grained, equigranular, olivine-plagioclase-orthopyroxene metagabbro to metanorite with accessory clinopyroxene and ilmenite. The unit typically contains dark clots of concentrically zoned mafic phases and contains a metamorphic assemblage of plagioclase, clinopyroxene, biotite, hornblende, garnet, and minor orthopyroxene developed as coronas around primary phases. Locally, the margins of the metagabbro bodies contain an undifferentiated zone of foliated migmatitic amphibolite; the marginal amphibolite is interpreted as deformed and migmatitic equivalents of the metagabbro cores Syn- to Pre-Tectonic Igneous Rocks Clinopyroxene-hornblende granitic gneiss (Mesoproterozoic)— Light- to dark-gray, white weathering, medium- to coarse-grained, equigranular, moderately foliated clinopyroxene-hornblende granitic gneiss ranging in composition from granite to syenite. Contains primary plagioclase, K-feldspar, and quartz. K-feldspar consists of microperthite and microcline that locally exhibits flame perthite, braid perthite, and patch perthite textures. K-feldspar may exhibit rims of plagioclase. Clinopyroxene is blue-green and contains thin lamellae, hornblende is olive green to light brown; the two minerals occur in variable quantities with hornblende the more abundant and both comprise about 10-15 percent of the rock. The rock contains about 1-2 percent magnetite and trace amounts of titanite, apatite, hematite, and zircon. The unit occurs in two places on the map on the north and west side of Bulwagga Mountain. All outcrops occur in wooded areas, and at the time of mapping, the locations south of Cold Spring Park on the north side of Bulwagga Mountain occurred in an active logging area and thus offered the best exposure Migmatite gneiss with pegmatite (Mesoproterozoic)—Heterogeneous, white to gray, dull gray weathering, well-foliated migmatite gneiss with garnet-rich leucosome and abundant pegmatite; the latter occurs as both well-foliated varieties and coarse grained; unfoliated varieties resembling unit Yp. Locally, the unit contains biotite, sillimanite, and flake graphite. The unit is a complex mixture of leucosome and pegmatite of different ages, and it occurs in contact with units Ysi and Ym on the southwest side of an unnamed hill in the southwest corner of the map. The unit is also exposed in the adjacent Ticonderoga quadrangle, and has been described at a roadcut on Route 74 by Regan and others (2015) and Williams and others (2018); the latter report uranium-lead (U-Pb) zircon ages of 1,177±10 Ma and 1,067±6 Ma from the migmatite, a 1,015±10 Ma age from a crosscutting pegmatite, and monazite ages from about 1,150-930 Ma with a dominant population at about 1,050 Ma Granitic augen gneiss (Mesoproterozoic)—Light-gray, locally light-pink, very light-gray to dark-gray-green weathering, wellfoliated, inequigranular, megacrystic granite gneiss with K-feldspar (perthite-microperthite) augen (1-5 cm) in a matrix of quartz, plagioclase, K-feldspar, biotite, and locally abundant garnet. The unit contains accessory epidote, zircon, and allanite, and contains lesser amounts of variably foliated, layer-parallel pegmatitic granite gneiss with quartz, mesoperthite, and accessory epidote. The granite typically contains abundant xenoliths of nearby amphibolite (Ya) associated with mafic respite. The unit is well exposed and commonly forms resistant, glacially rounded blocky outcrops. Because of its characteristic texture and resistant weathering, the unit is relatively easy to recognize and map in the field. It occurs as highly deformed, foliation-parallel, thin sill-like bodies on Keeney Mountain, on the North side of Buck Mountain, on Miller Mountain, and in an area west of Route 9N/22 just east of the Crown Point Street Road delta sand and gravel pits. Regan and others (2019) report a sensitive high resolution ion microprobe (SHRIMP) U-Pb zircon age of 1,185±11 Ma from a sample collected in the adjacent Eagle Lake 7.5-minute quadrangle Mesoproterozoic Metasedimentary and Metavolcanic Paragneiss Grenville Complex [Lithodemic units are not described in stratigraphic order; order is unknown] Migmatitic biotite gneiss member (plus Ybgg and Yrbg) (Mesoproterozoic)—Gray to dark-gray, dark-gray to black and white banded, light-gray weathering, well-foliated, migmatitic, mediumgrained, biotite-K-feldspar-quartz-plagioclase paragneiss with locally undifferentiated amphibolite and calc-silicate rock. The unit is well layered and varies from an equigranular quartz-feldspar gneiss to a well-layered biotite-rich migmatite. Accessory phases include hornblende, garnet, sillimanite, diopside, epidote, apatite, zircon, and allanite. Where garnet and sillimanite are locally abundant, the rock is mapped as biotite gneiss with garnet (Ybgg); this rock is distinctly non-rusty weathering and non-graphitic and is thus distinguishable from unit Ysi. A rusty sulfide-rich biotite-bearing paragneiss without garnet or sillimanite (unit Yrbg) is mapped in two places on Mine Hill; the lack of obvious garnet or sillimanite distinguishes this minor unit from unit Ysi. Sedimentary layering is largely destroyed due to metamorphism and tectonism, but local compositional banding, especially of interlayered light-green calc-silicate rocks, is likely a remnant of original bedding. The unit is locally interlayered on the meter-scale with fine-grained amphibolite, locally mapped as unit Ya where thick enough. Leucosome occurs as pegmatitic segregations, dikes, and sills. Non-migmatitic varieties contain little biotite, and consist mostly of K-feldspar, quartz, and plagioclase. Map unit Ybg is the most widespread metasedimentary unit in the area and is well exposed on Miller Mountain and Buck Mountain. Good exposures occur along the west side of Route 9N/22 north of Spar Mill Bay, under the power lines northwest of Spar Mill Bay, and along Putnam Creek between an elevation of 510 and 580 feet, west of Crown Point Center. The unit may correlate with unit Y1,2bg in Vermont (Ratcliffe and others, 2011) Rusty garnet-sillimanite gneiss member (Mesoproterozoic)—Gray to dark-gray and tan, white to tan-gray and rusty weathering, well-foliated, migmatitic, garnet-sillimanite-K-feldspar-plagioclasequartz paragneiss with variable amounts of graphite and biotite. Locally, the unit is sulfidic and very rusty weathering. Accessory phases include pyrite, monazite, zircon, apatite, xenotime, allanite, epidote, and ilmenite. Paragneiss contains undifferentiated interlayered quartzite, calc-silicate gneiss, marble, and amphibolite, and abundant layer-parallel, locally garnet- and (or) graphite-rich pegmatite as variably dismembered pegmatite boudins and sill-like intrusions. Leucosome occurs as pegmatitic segregations, dikes, and sills. Layering varies in thickness but is predominately on the order of meters to decimeters except where interleaved with calc-silicate gneiss and quartzite, where it is layered on the cm- to decimeter-scale. Referred to as khondalite (McLelland and others, 1988) or kinzigite (Walton, 1966b). The unit is interpreted as metamorphosed interbedded psammitic to pelitic rocks that underwent partial melting. Locally, coarse garnet (up to 2 cm) comprise up to 50 percent of the rock. Garnet typically contains abundant quartz inclusions and is locally book-shelved and partially replaced by biotite or sillimanite. Although tectonic and metamorphic in origin, large exposures of this unit exhibit modal variations in biotite, garnet, and quartz at the cm scale, which is interpreted as a pseudostratigraphy. The unit is well exposed on Breeds Hill north of the Crown Point Spar Company quarry and roadcuts along Route 9N/22 near Spar Mill Bay. The unit may correlate with units Y2rs and Y2rss in Vermont (Ratcliffe and others, 2011) Marble and calc-silicate gneiss member (Mesoproterozoic)—White to green, white and dark-green to black spotted, tan to earthy yellowish-brown or rusty weathering, poorly exposed, deeply weathered, coarse-grained dolomite marble, calcite marble, calc-silicate gneiss, quartzite, and quartz-rich pods. The unit contains Opi Ofc Ocu Ogf Oo Ov Ocp O w ti pt Zd Yp Yu Ylg Ylgg Ylgt Ygb Ym Yma Yhg Ymig Yggn Ybg Ybgg Yrbg Ysi Ycs Ya Oib Osp af Qls Qal wt 1,048±14 Ma CP-3000 M Qls Qal Mafic dikes In cross section only PALEOZOIC SEDIMENTARY ROCKS PROTEROZOIC IGNEOUS AND METAMORPHIC ROCKS NEOPROTEROZOIC IGNEOUS ROCKS ORDOVICIAN Upper Ordovician Middle Ordovician MESOPROTEROZOIC Stratigraphic order is unknown NEOPROTEROZOIC Ediacaran Pegmatite QUATERNARY CAMBRIAN Upper Cambrian Upper and Middle(?) Cambrian Grenville Complex Syn- to Post-Tectonic Igneous Rocks Syn- to Pre-Tectonic Rocks Late- to Post-Tectonic Igneous Rocks af wt Ogf Oo Unconformity Ov Unconformity Ocp Knox Unconformity Great Unconformity Oib MESOPROTEROZOIC IGNEOUS ROCKS Mixed paragneiss and orthogneiss Yp Ylgt Yu Ymig Ygb Orthogneiss Ylg Ylgg Ybg Ycs Ybg Ya Ybg Ybgg Ybg Yrbg Osp Ocu O w ti pt Ysi Ym Yma Ya Yhg Yggn Opi Ofc HOLOCENE AND QUATERNARY DEPOSITS CORRELATION OF MAP UNITS Lower Ordovician Brittle Faulting Paleozoic Cleavage RELATIVE TIMING OF DEFORMATION EVENTS Penetrative Deformation D2 Cryptic Deformation D1 Doming D3 Boudinage and Shear Bands D4 Rifting Zd Mesoproterozoic Metasedimentary and Metavolcanic Paragneiss Lyon Mountain Granite Gneiss (Postel, 1952) U.S. Department of the Interior U.S. Geological Survey Scientific Investigations Map 3491 Pamphlet accompanies map Prepared in cooperation with the STATE OF VERMONT, VERMONT AGENCY OF NATURAL RESOURCES, VERMONT GEOLOGICAL SURVEY and the STATE OF NEW YORK, DEPARTMENT OF EDUCATION, NEW YORK GEOLOGICAL SURVEY