Lockport Group (NYSl;5)

State	New York
Name	Lockport Group
Geologic age	Upper Silurian
Original map label	Sl
Comments	80-175 ft. (25-55 m). Unit descriptions from USGS Lexicon website (ref. NY046) and reference NY018: Proposed abandonment of the Oak Orchard because unit is similar to Eramosa Dolomite and allows uniformity of nomenclature and stratigraphy with interval in Ontario, CAN (Brett and others, 1995). The Eramosa Dolomite of the Lockport Group is revised to include lower interval formerly called the Oak Orchard Dolomite of the Lockport Group or the Oak Orchard Member of the Lockport Formation by Zenger (1965) and an upper interval formerly assigned to the Guelph Dolomite. The Oak Orchard is proposed for abandonment herein. The revised Eramosa consists of massive, pale brownish-weathering, vuggy, commonly biostromal dolomite with intervals of sparsely fossiliferous, medium-bedded, flaggy-weathering, brownish-gray, bituminous dolomite and stromatolite bioherms. Formation can be divided into six informal units. Unit A is a 7 to 8 foot thick, massive, biostromal dolomite characterized by thickets of ramose tabulate coral and abundant white chert nodules. Unit B is a 13 to 20 foot thick, fine-grained, sparsely fossiliferous and bituminous dolomite that weathers medium-bedded to flaggy. Unit C consists of tabulate coral biostromes (similar to unit A) and masses of stromatolites; unit is massive or thick-bedded, brownish-weathering, saccroidal dolomite with large vugs. Unit D is a 16.8 foot thick flaggy-weathering, dark brownish-gray, nonfossiliferous, saccroidal dolomite with a middle massive interval that contains coral. Unit E is a 1- to 2-foot-thick marker bed of light-gray, laminar, stromatolitic dolomite. Unit F consists of 7.4 ft of medium-grained, olive-gray dolomite that locally contains scattered oolites and corals (similar to unit D). Thickness of the Eramosa is 38 to 50 ft. Well exposed in the Niagara River Gorge on old sewage treatment plant access road in Niagara Falls, Niagara Co., NY. Unconformably overlies the Goat Island Dolomite and underlies the Guelph Dolomite, both of the Lockport Group. The Eramosa is of Late Silurian (Ludlovian) age based on conodonts (Brett and others, 1995).
Primary rock type	dolostone (dolomite)
Secondary rock type	limestone
Other rock types
Lithologic constituents	Major Sedimentary > Carbonate > Dolostone Incidental Sedimentary > Carbonate > Limestone
Map references	NYS Museum, NYS Geological Survey, NYS Museum Technology Center, 1999, 1:250,000 Bedrock geology of NYS, data is distributed in ARC/INFOr EXPORT format (with ".e00" extension) in 5 seperate files based on printed map sheets, http://www.nysm.nysed.gov/gis.html. [http://www.nysm.nysed.gov/gis.html.]
Unit references	D. W. Fisher; Y. W. Isachsen, L. V. Rickard, 1970, Geologic Map of New York State, consisting of 5 sheets: Niagara, Finger Lakes, Hudson-Mohawk, Adirondack, and Lower Hudson, New York State Museum and Science Service, Map and Chart Series No. 15, scale 1:250000. Brett, C.E., Tepper, D.H., Goodman, W.M., LoDuca, S.T. and Eckert, Bea-Yeh, 1995, Revised stratigraphy and correlations of the Niagaran Provincial Series (Medina, Clinton, and Lockport Groups) in the type area of western New York: U.S. Geological Survey Bulletin, 2086, 66 p., Prepared in cooperation with the U.S. Environmental Protection Agency and the University of Rochester, Department of Earth and Environmental Sciences. [http://pubs.er.usgs.gov/publication/b2086] USGS Geologic Names Lexicon (GEOLEX) [http://ngmdb.usgs.gov/Geolex/]