Lockport Group

Oak Orchard and Penfield Dolostones; both replaced eastwardly by Sconondoa Formation-limestone, dolostone.
State New York
Name Lockport Group
Geologic age Upper Silurian
Lithologic constituents
Sedimentary > Carbonate > Dolostone
Sedimentary > Carbonate > Limestone
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).
NGMDB product
Counties Cayuga - Madison - Monroe - Oneida - Onondaga - Oswego - Wayne