|Name||Undifferentiated Lower Hamilton Group|
|Geologic age||Middle Devonian|
Sedimentary > Clastic > Mudstone > Shale
Sedimentary > Clastic > Sandstone
Sedimentary > Carbonate > Limestone
|Comments||part of Hamilton Group 1700-2800 ft. (520-850 m). Secondary unit descriptions from USGS Lexicon website (ref. NY046) and references NY022, NY025, and NY026: Mount Marion Formation of Hamilton Group is divided into Berne and overlying Otsego Members. The boundary between the two members is revised in this report. The base of the Otsego is placed at the base of a coral-brachiopod biostrome, the lowest rugose coral in a massive sandstone or the top of the massive sandstone (in the absence of corals). In the absence of both, the base is placed at the lowest shell-bed-rich shales that overlie an 8.0-m-thick package of thin sandstones and shales. The base is somewhat diachronous due to local erosive beveling. Formal names are proposed here for four key beds within the Formation: the Dave Elliott occurs in the upper part of the Berne Member; the Halihan Hill Bed marks the base of the Otsego; and the Katsbaan and Timmerman Hill Beds occur in the lower part of the Otsego (Ver Straeten, 1994). Stony Hollow member of Marcellus formation named in this report. Unit extends from southeastern NY to northeastern PA. Composed chiefly of fine-grained calcareous sandstone 75-100 ft thick. Underlies Mount Marion formation of Grabau at its type section. Beds formerly classified as "Marcellus" shale (Bakoven of Chadwick) immediately underlie Stony Hollow member and are now proved to be equivalent of Union Springs member. Southwest of Albany, layers of limestone appear in upper part of sandstone that has thinned to 24 ft. West of Onesquethaw Creek, these limestones of the Stony Hollow become the Cherry Valley limestone as exposed in Stony Creek, Schoharie Valley. Middle Devonian age given by Cooper and others (1942: GSA Bull., v. 53, no. 12, pt.1, p. 1783) (Cooper, 1941). Union Springs member of Marcellus formation named in this report. Consists of alternating beds of black limestone and sooty shale overlying Onondaga limestone and underlying Cherry Valley limestone member of Marcellus from Unadilla Valley westward to Seneca Lake. Thickness is 17 ft at type section in Wood's quarry. At Marcellus it is 13 ft thick, at Oneida Creek above Stockbridge Falls, 25 ft, and on Flint Creek, near Phelps, 9 ft. It is not known west of Phelps, Ontario Co., NY (Cooper, 1930).|
Fisher, D.W., Isachsen, Y.W., and Rickard, L.V., 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 1:250,000.
Cooper, G.A., 1930, Stratigraphy of the Hamilton Group of New York: American Journal of Science, 5th series, v. 19, no.53, pts. 1-2, p. 116-134, 214-236.
Ver Straeten, C.A., 1994, Microstratigraphy and depositional environments of a Middle Devonian foreland basin; Berne and Otsego Members, Mount Marion Formation, eastern New York, IN Landing, Ed, ed., Studies in stratigraphy and paleontology in honor of Donald W. Fisher: New York State Museum Bulletin, no. 481, p. 367-380.
Cooper, G.A., 1941, New Devonian stratigraphic units: Washington Academy of Sciences Journal, v. 31, no. 5, p. 179-181.
USGS Geologic Names lexicon found at: http://ngmdb.usgs.gov/Geolex/
|Counties||Albany - Greene - Schoharie - Ulster|