|Geologic age||Middle Devonian|
|Comments||part of Hamilton Group 200-500 ft. (60-150 m). Secondary unit descriptions from USGS Lexicon website (ref. NY046) and references NY015 and NY024: Marcellus Shale of the Hamilton Group is the oldest of the extensive black gas shales. Unit crops out in the Valley and Ridge from southeastern NY to northern WV. The Marcellus or its partial equivalent the Millboro Shale, is present in the subsurface in NY, PA, OH, western MD, VA, WV, and northeastern TN. Consists for the most part of sooty black shale and a few beds of medium-gray shale and limestone nodules or beds of dark gray to black limestone. Marcellus is approximately 1,000 ft thick in central PA, but thins to the north, west, and south. Feathers out in eastern OH, western WV, and southwestern VA. The Cherry Valley Limestone Member is an extensive unit in the subsurface of NY, PA, and WV (deWitt and others, 1993). Marcellus Formation will be formally raised to subgroup status within the Hamilton Group and be divided into a lower Union Springs Formation and an upper Mount Marion Formation (in eastern NY) and an upper Oatka Creek Formation (in central and western NY) in a publication by Ver Straeten and others (in prep). Union Springs Formation will incorporate three members across NY: The Bakoven Member (geographically extended across the State of NY), the Stony Hollow Member (restricted), and the Hurley Member (new). The Hurley underlies the Cherry Valley Member at the base of the laterally equivalent Mount Marion and Oatka Creek Formations. By extending the Cherry Valley across the State, it now includes strata formerly assigned to the upper part of the Stony Hollow Member. The revised Cherry Valley is composed of two lithosomes; an eastern sand-dominated facies and a central to western carbonate-dominated facies. Strata above the Cherry Valley in the Oatka Creek remain unnamed, though they bear some resemblance to the Chittenango Shale Member of the Mount Marion Formation of west-central NY (Ver Straeten and others, 1994). Name Oatka Creek shale proposed for upper member of Marcellus shale from Cayuga Lake westward to Seneca Lake. Underlies Mottville member of Skaneateles shale and overlies Cherry Valley limestone member of Marcellus. West of Seneca Lake, the Oatka Creek member comprises all of Marcellus and includes time equivalents of (ascending) Union Springs member, Cherry Valley limestone member, Chittenango member and Cardiff member. In the area west of Cayuga Lake, the Oatka Creek member is overlain by Stafford limestone, the equivalent of the Mottville member. The Oatka Creek consists of black shale, distinctly calcareous and fossiliferous, and thus differing from the black Chittenango shale, which overlies the Cherry Valley limestone in eastern part of the State. Thickness is 30 ft at type section at Le Roy where whole section is exposed. Thickens to the east and to the west to over 50 ft. Other exposures are in bed of Conesus Creek at Ashantee, Genesee Valley, and in Flint Creek 1.5 mi northeast of Orleans. At all these localities it is overlain by a thin Stafford limestone. Age is Middle Devonian.|
|Primary rock type||black shale|
|Secondary rock type|
|Other rock types|
Sedimentary > Clastic > Mudstone > Shale > Black-shale
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.
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.