Yegua Formation (TXEOy;0)

State	Texas
Name	Yegua Formation
Geologic age	Middle Eocene
Lithologic constituents	Major Sedimentary > Clastic > Sandstone (Bed) Sedimentary > Clastic > Mudstone > Claystone (Bed) Incidental Sedimentary > Carbonate > Limestone (Bed) Sedimentary > Coal > Lignite (Bed) Igneous > Volcanic (Pyroclastic-air fall)
Comments	clay with minor beds of sandstone, some concretionary limestone beds and lenses of oyster shells. sandst fine grained, calcar., glauconitic, massive, laminated, crossbedded; fossil wood; Volcanic ash included. silicified tuff containing an oyster and gastropod fauna (Eargle, 1968); 1,000 ft thick in San Antonio Sheet (1974). In East Texas and Gulf Coast to Rio Grande: Overlies Cook Mt. Formation; overlain by Caddell Fm. Unit is sandstone, clay, and lignite. Sandst. is mostly quartz and some chert, fine-grained, laminated, corssbedded; clay, lignitic, sandy, bentonitic, well laminated, lentils of lignite. In Seguin Sheet unit is about 1000 ft thick.
Stratigraphic units	Claiborne Group
References	Eargle, D.H., 1968, Nomenclature of formations of Claiborne Group, Middle Eocene, coastal plain of Texas: U.S. Geological Survey Bulletin 1251-D. https://pubs.er.usgs.gov/publication/b1251D Bureau of Economic Geology, 1970, Waco 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, 1974, Seguin Sheet, Geologic Atlas of Texas, University of Texas, Bureau of Economic Geology, scale 1:250,000. 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, 1967, Palestine Sheet, Geologic Atlas of Texas, Bureau of Economic Geology, University of Texas at Austin, 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	NGMDB product page for 68390
Counties	Angelina - Atascosa - Bastrop - Brazos - Burleson - Fayette - Frio - Gonzales - Grimes - Houston - Karnes - La Salle - Lee - Leon - McMullen - Madison - Nacogdoches - Sabine - San Augustine - Starr - Trinity - Uvalde - Walker - Webb - Wilson - Zapata

State

Texas

Name

Yegua Formation

Geologic age

Middle Eocene

Lithologic constituents

Major

Sedimentary > Clastic > Sandstone (Bed)

Sedimentary > Clastic > Mudstone > Claystone (Bed)

Incidental

Sedimentary > Carbonate > Limestone (Bed)

Sedimentary > Coal > Lignite (Bed)

Igneous > Volcanic (Pyroclastic-air fall)

Comments

clay with minor beds of sandstone, some concretionary limestone beds and lenses of oyster shells. sandst fine grained, calcar., glauconitic, massive, laminated, crossbedded; fossil wood; Volcanic ash included. silicified tuff containing an oyster and gastropod fauna (Eargle, 1968); 1,000 ft thick in San Antonio Sheet (1974). In East Texas and Gulf Coast to Rio Grande: Overlies Cook Mt. Formation; overlain by Caddell Fm. Unit is sandstone, clay, and lignite. Sandst. is mostly quartz and some chert, fine-grained, laminated, corssbedded; clay, lignitic, sandy, bentonitic, well laminated, lentils of lignite. In Seguin Sheet unit is about 1000 ft thick.

Stratigraphic units

Claiborne Group

References

Eargle, D.H., 1968, Nomenclature of formations of Claiborne Group, Middle Eocene, coastal plain of Texas: U.S. Geological Survey Bulletin 1251-D.

https://pubs.er.usgs.gov/publication/b1251D

Bureau of Economic Geology, 1970, Waco 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, 1974, Seguin Sheet, Geologic Atlas of Texas, University of Texas, Bureau of Economic Geology, scale 1:250,000.

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, 1967, Palestine Sheet, Geologic Atlas of Texas, Bureau of Economic Geology, University of Texas at Austin, 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

NGMDB product page for 68390

Counties

Angelina - Atascosa - Bastrop - Brazos - Burleson - Fayette - Frio - Gonzales - Grimes - Houston - Karnes - La Salle - Lee - Leon - McMullen - Madison - Nacogdoches - Sabine - San Augustine - Starr - Trinity - Uvalde - Walker - Webb - Wilson - Zapata