Strawn Group (TXPAst;0)

State	Texas
Name	Strawn Group
Geologic age	Phanerozoic \| Paleozoic \| Carboniferous Pennsylvanian-Middle [Atoka Des Moines]
Original map label	IPst
Comments	Unit redefined, renamed, or modified as described in at least 11 publications up to 1960 since orginally described by Dumble (1890) as alternating clays and shales and thin-bedded limestones, with fire clay and coal, overlying Richland-Gordon sandstones and underlying Brownwood-Ranger series. Mostly sh. and mudst., silty, greenish gray to red, mudcracks common, generally poorly exposed, underlies subdued topography, fossils include plants and marine magafossils locally; limestone beds generally impure and discontinuous, more abdt. near top; sandst. forms thin discontinuous sheets and small channel fills, fewer beds near top. Ricker Station Ls.(1-4 ft thick) and Capps Ls. (up to 20 ft thick) in upper part of Strawn GroupUpper part above Capps Ls. equivalent to Brownwood Shale (fr. Brownwood Sheet, 1976). Group 1300-1400 ft thick.
Primary rock type	shale
Secondary rock type	sandstone
Other rock types	clay or mud; sandstone; conglomerate; coal
Lithologic constituents	Major Sedimentary > Clastic > Mudstone > Claystone (Bed)mostly mudstone with thin sandst. units and a few limest. lentils
Map references	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
Unit references	Cooper, G.A., and Grant, R.E, 1972, Permian brachipods of West Texas, I, in Smithsonian Contributions to Paleobiology no. 14. Dumble, E.T., 1890, Texas Geological Survey 1st Annual Report, pl. 3, p. lxvi. Plummer, F.B., and Moore, R.C., 1921, Stratigraphy of the Pennsylvanian formations of north-central Texas: University of Texas Bulletin 2132. Bureau of Economic Geology, 1976, Brownwood sheet, Geologic Atlas of Texas, Bureau of Economic Geology, University of Texas at Austin, scale 1:250,000.
Geographic coverage	Brown - Lampasas - McCulloch - Mills - San Saba