The black shale below the Mount Marion formation in eastern NY, formerly referred to "Marcellus," remains unidentified by Dr. Cooper with any of his Hamilton units and is therefore here called Bakoven (pronounced Bok-o-fen) shale, from local Dutch name of valley it forms. Age is Middle Devonian.

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

Pg. 240-249. Bakoven shale. In Coxsackie quadrangle, forms narrow belt for full length of area. In upper part, it is entirely included in Hamilton escarpment, which rises abruptly above Onondaga Flats. Further south, in part, it forms east face of Hamilton Hills and, in part, underlies a hilly valley occupied in extreme south by Hollister Lake and a branch of the Catskill. Thickness for this area [is] between 180 and 200 feet. Not in contact with Onondaga in this quadrangle. Underlies Stony Hollow member [of G.A. Cooper (1941, Washington Acad. Sci. Jour., v. 31, no. 5, p. 179-180; see also p. 247-248, this report] of Marcellus Shale. Bakoven shale of Chadwick [1933, Amer. Jour. Sci., 5th ser., v. 16, p. 480, 483] now represents gray shale facies of Union Springs member of Marcellus.

Source: US geologic names lexicon (USGS Bull. 1200, p. 198).

Bakoven, formerly termed "Marcellus shale," is assigned to Hamilton group as basal formation in Albany Co., NY. Typically black pyritiferous fissile shale. Thickness about 200 ft. Underlies Mount Marion formation; overlies Onondaga limestone. Age is Middle Devonian.

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

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 New York), and an upper Oatka Creek Formation (in central and western New York), in a publication by Ver Straeten and others (in prep). Union Springs Formation will incorporate three members across New York: the Bakoven Member (geographically extended across the State of New York), 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. The Bakoven will include all black shale-dominated strata in the Union Springs. Contains bone bed. Bakoven unconformably overlies the Seneca Member or, where absent, the Moorehouse Member of the Onondaga Formation.
["Subgroup" not recognized as a formal stratigraphic rank term (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005, 2021). Considered informal and should not be capitalized.]

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