| State | Texas |
|---|---|
| Name | Washita and Fredericksburg Groups, undivided |
| Geologic age | Early Cretaceous; Comanchean Series |
| Lithologic constituents |
Major
Unconsolidated > Fine-detrital > Clay (Bed)
Minor
Sedimentary > Carbonate > Limestone (Bed)
Incidental
Sedimentary > Carbonate > Dolostone (Bed)
|
| Comments | Washita Group--alternating thick clay units and thin limestone units; clay, calcar, commonly sandy, dk bluish gray and black; limestone in lower part hard, bluish gray to shtie, in upper part soft, thickbedded; marine megafossils; thickness 200 ft. Fredericksberg Group--Limestone,dolomite,chert, marl. Limestone nodular, aphanitic, marly, gray, yell, white, pink; dolomite, find grained, gray; chert, in thin layers and nodules; marl locally gypsiferous, gray. abundant Exogyra texana some beds made almost entirely of Gryphaea sp., exposed thickness 50 ft in Hobbs Sheet (1976). |
| References | Bureau of Economic Geology, 1976, Hobbs Sheet, Geologic Atlas of Texas: University of Texas at Austin, Bureau of Economic Geology, scale 1:250,000.Bureau of Economic Geology, 1966, Texarkana Sheet, Geologic Atlas of Texas, University of Texas, Bureau of Economic Geology, scale 1:250,000.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. |
| NGMDB product | |
| Counties | Brewster - Pecos |