Bedrock geologic map of the Crown Point quadrangle, Essex County, New York, and Addison County, Vermont

First posted October 28, 2022 For additional information, contact: Director, Florence Bascom Geoscience CenterU.S. Geological Survey926A National Center12201 Sunrise Valley DriveReston, VA 20192Contact Pubs Warehouse The bedrock geology of the 7.5-minute Crown Point quadrangle consists deformed and metamorphosed Mesoproterozoic gneisses Adirondack Highlands unconformably overlain by weakly lower Paleozoic sedimentary rocks Champlain Valley. occur on eastern edge represent an extension Grenville Province Laurentia. Granulite facies paragneiss, marble, amphibolite hosted emplacement granitic orthogneiss at approximately 1.18–1.15 giga-annum (Ga, billion years before present). earliest four phases deformation (D1) is characterized gneissosity, rarely preserved F1 isoclinal folds, migmatite in host rocks. Subsequent D2 produced a composite penetrative migmatite, F2 folds. Towards end D2, felsic magmatism (including regionally extensive Lyon Mountain Granite Gneiss, abbreviated “LMG”) spread migration as semiconcordant alkali feldspar granite sheets subparallel to S2 into previously lithologies. LMG crystallized 1.15 Ga displays synkinematic folds thus constraining time deformation. Exhumation during D3 F3 exhibited regional domes basins, such Keeney synform, local reactivation foliation, partial melting, metamorphism, metasomatism, iron ore remobilization, intrusion magnetite-bearing pegmatite both layer-parallel sills crosscutting dikes. D4 created NE- NW-trending boudinage, high-grade ductile shear zones, Kilometer (km)-scale lineaments readily observed lidar data are Ediacaran mafic dikes Phanerozoic brittle faults. part Early Cambrian Late Ordovician great American carbonate bank ancient margin Cambrian-Ordovician stratigraphy records 1-km-thick section transition from synrift clastics passive peritidal buildups gradually deeper water subtidal shelf carbonates foreland basin development associated with Taconic orogeny. folded block faulted. Large areas covered undifferentiated glacial deposits, some which contain mapped landslides. map also shows waste rock piles tailings historical mining operations large artificial fill.This study was undertaken improve our understanding Highlands, establish modern framework for 1:24,000-scale geologic mapping Adirondacks, provide context mines update New York Vermont. This Scientific Investigations Map sheet, explanatory pamphlet, geographic information system database that includes units, faults, outcrops, structural information. sheet map, correlation description explanation symbols, three cross sections, simplified surficial percent slope. pamphlet discussion geology.The multi-layered has been designed enable user turn off layer view concealed units.