|Geologic age||Early Pennsylvanian|
Sedimentary > Clastic > Mixed-clastic > Sandstone-mudstone (Bed)
|Comments||Shale and sandstone, dark gray, poorly exposed beds a few inches thick; crops out in southern part of Cochran Mountains (fr. Emory Peak-Presidio Sheet, 1979, Geol. Atlas of Texas). Monotonous sequence of intercalated fine-grained sandst. and illite-rich, gray shale beds less than 6 inches thick. the sequence has a max. preserved thickness of 4,300 ft; part of a 12,000 ft sequence of flysch deposited during late Paleozoic time in the Marathon geosyncline, a part of the Ouachita geosyncline (McBride, 1966). Sandst. and carbonaceous shale in regular alternations with an occasional thicker sandst. bed, and near the base some thick layers of shale; in upper part, thick beds of massive arkose and several boulder-bearing mudstone intervals as much as 150 ft thick; thickness of formation exceeds 3,000 ft. (fr. Fort Stockton Sheet of Geol. Atlas of Texas, 1982). Boulder beds are remarkable in size and variety of clasts. Clasts made of fragmented flysch beds, mudst. pods, slump features, erratic debris, rounded clasts of brecciated Caballos Novaculite, and rounded clasts of ss., metamorphic rock, igneous rocks unlike older Paleozoic rocks in the region.|
Bureau of Economic Geology, 1982, Fort Stockton Sheet, Geologic Atlas of Texas, University of Texas at Austin, scale 1:250,000.
Bureau of Economic Geology, 1979, Emory Peak--Presidio Sheet, Geologic Atlas of Texas, University of Texas at Austin.
McBride, E.F., 1966, Sedimentary petrology and history of the Haymond Formation (Pennsylvanian), Marathon Basin, Texas: Bureau of Economic Geology the University of Texas at Austin, Report of Investigation 57, 101 p.
King, P.B., 1937, Geology of the Marathon region, Texas: U.S. Geological Survey Professional Paper 187, 148 p.
Bureau of Economic Geology, 1992, Geologic Map of Texas: University of Texas at Austin, Virgil E. Barnes, project supervisor, Hartmann, B.M. and Scranton, D.F., cartography, scale 1:500,000.
|Counties||Brewster - Pecos - Presidio|