On each side of Otsego Lake, north of Cooperstown, the arenaceous shales between the Chittenango and Solsville members of the Marcellus are divisible into two parts. Name Otsego member of Marcellus shale is proposed for the lower portion, which is characterized by a definite fauna. In places the upper part of the Otsego is a heavy sandstone or gray cross-bedded sandstone containing CORNELLITES FLABELLUS and other fossils. Type section is in the "Dugway" on east side of Otsego Lake. Thickness at Otsego Lake is 256 ft, in Schoharie Valley, 385 ft, and in Berne quad., 505 ft. Age is Middle Devonian.

Source: GNU records (USGS DDS-6; Reston GNULEX).

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.

Source: GNU records (USGS DDS-6; Reston GNULEX).