Buck tongue of Mancos shale. A westward-pointing tongue of Mancos shale, 0 to 350 feet thick, which in part of area [between Sunnyside and Colorado State line] wedges in between Sego and Castlegate sandstone members of Price River formation, of Mesaverde group. Not recognized northwest of Beckwith Plateau. Carries marine invertebrates of Lewis age. [Age is Late Cretaceous.]
Named from Buck Canyon, in T. 19 S., R. 23 E., [Antone Canyon 7.5-min quadrangle, Grand Co.], Book Cliffs, central eastern UT.
[GNC remark (ca. 1936, US geologic names lexicon, USGS Bull. 896, p. 283): This name first appeared in print in USGS Bull. 851, 1934, by C.E. Erdmann, in a report on eastern part of Book Cliffs coal field, where he treated the Buck tongue of Mancos shale as underlying Sego sandstone and overlying Castlegate sandstone, and gave its thickness as 360 feet. (See also 1932 correlation chart of Utah, compiled by M.G. Wilmarth.)]

Source: US geologic names lexicon (USGS Bull. 896, p. 283).

Used as a tongue of Mancos shale in central Book Cliffs, UT east of Green River, Paradox basin, as a unit between the Castlegate sandstone (below) and the Sego sandstone (above). Farther west it fingers into and is not separable from Price River formation. Increases in thickness eastward from about 100 ft in southern Beckwith Plateau to 350 ft at UT-CO line. Merges farther east with rest of Mancos as Castlegate sandstone disappears. Considerable variety of marine fauna (listed). Eight measured sections described. Is characteristically a gray shale that locally may be coaly, gypsiferous, and a buff sandstone. Columnar sections.

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

Buck Tongue of Mancos Shale revised to include Loyd Sandstone Bed. Loyd locally present westward but separately mapped only along west flank of Pinyon Ridge in north-central part of quad. Farther east, where Buck Tongue has merged with main body of Mancos, Loyd considered member of Mancos. Area of report is Rough Gulch quad, Rio Blanco and Moffat Cos, CO, Greater Green River basin and Piceance basin. Geologic map. Late Cretaceous age.

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

Is a unit of middle Campanian age (an age refinement) that overlies the Castlegate Sandstone and underlies the Bluecastle Tongue (removed from Price River and Neslen Formations and assigned to the Castlegate Sandstone) in the Paradox basin.

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

Along with its Loyd Sandstone Bed, is assigned to main body of Mancos Group. Shown in subsurface from Douglas Creek arch area to area west of White River uplift, Rio Blanco Co, CO, Piceance basin. [Buck previously assigned to Mancos Shale. In eastern Uinta and western Piceance, Molenaar and Wilson (198_) raised rank of Mancos dividing it into, in ascending order, Mowry Shale, Frontier Formation and main body in upper part].

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