Cook Mountain Formation (TXEOcm;0)

State	Texas
Name	Cook Mountain Formation
Geologic age	Phanerozoic \| Cenozoic \| Tertiary \| Eocene
Original map label	Ecm
Comments	clay and marly sand, argillaceous and carbonaceous sand, marl and clay, marly clay. In San Antonio Sheet clay and glauconitic sandstone, marine fossils, unit about 230 ft thick. In Seguin Sheet clay and sandstone about 200-230 ft thick. In Crystal City Sheet clay and sandstone; clay gypsiferous, sl. lignitic, sandst. v. fine grained, marine megafossils and microfossils abdt; thickness about 200-350 ft thick.
Primary rock type	clay or mud
Secondary rock type	sandstone
Other rock types	coal
Lithologic constituents	Major Sedimentary > Clastic > Sandstone (Bed) Sedimentary > Clastic > Mudstone > Claystone (Bed) Minor Sedimentary > Clastic > Siltstone (Bed) Incidental Sedimentary > Carbonate > Marlstone (Bed) Sedimentary > Coal > Lignite (Bed)
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	Bureau of Economic Geology, 1976, Crystal City-Eagle Pass Sheet, Geologic Atlas of Texas, University of Texas, Bureau of Economic Geology, scale 1:250,000. Bureau of Economic Geology, 1974, Seguin Sheet, Geologic Atlas of Texas, University of Texas, Bureau of Economic Geology, scale 1:250,000. Bureau of Economic Geology, 1974, San Antonio Sheet, Geologic Atlas of Texas, University of Texas, Bureau of Economic Geology, scale 1:250,000. Bureau of Economic Geology, 1967, Palestine Sheet, Geologic Atlas of Texas, Bureau of Economic Geology, University of Texas at Austin, scale 1:250,000.
Geographic coverage	Anderson - Angelina - Atascosa - Bastrop - Brazos - Burleson - Cherokee - Fayette - Frio - Gonzales - Houston - La Salle - Lee - Leon - Madison - Nacogdoches - Robertson - Sabine - San Augustine - Wilson