| State | Texas |
|---|---|
| Name | Fredericksburg Group |
| Geologic age | Early Cretaceous; Comanchean Series |
| Lithologic constituents |
Major
Unconsolidated > Marl (Bed)
Sedimentary > Carbonate > Limestone (Bed)
Sedimentary > Carbonate > Dolostone (Bed)
Minor
Sedimentary > Chemical > Chert (Bed)
|
| Comments | 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). Edwards Limstone, limestone, dolostone, and chert 60-350 ft thick. Comanche Peak Limestone 80 ft thick. Keys Valley Marl, soft, white as much as 50 ft thick. Cedar Park Limestone similar to Comanche Peak Ls (fine to v. fine grained, fairly hard, nodular, lt. gray, burrowed). Bee Cave Marl soft, white Exogyra texana abdt, thickness 25-40 ft. |
| Stratigraphic units | Includes:Edwards Limstone, Comanche Peak Limestone, Keys Valley Marl, Cedar Park Limestone, Bee Cave Marl |
| 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, 1974, Austin 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 - Crane - Crockett - Ector - Pecos - Travis - Upton - Williamson - Winkler |