Geology of Texas

The state's stratigraphy has been largely influenced by marine transgressive-regressive cycles during the Phanerozoic, with a lesser but still significant contribution from late Cenozoic tectonic activity, as well as the remnants of a Paleozoic mountain range.

South and east of these faults, the surface exposures consist mostly of Cenozoic sandstone and shale strata that grow progressively younger toward the coast, indicative of a regression that has continued from the late Mesozoic to the present.

This large region of central Texas, which extends from Brewster County east to Bexar, and northeast to the Red River features extensive Cretaceous shale and limestone outcrops.

From San Saba north to Childress, and from Wichita Falls in the east to Big Spring in the west, the surface consists of late Paleozoic (Pennsylvanian) to early Mesozoic (Triassic) marine sediments.

The geology of west Texas is arguably the state's most complex, with a mix of exposed Cretaceous and Pennsylvanian strata, overlain by Quaternary conglomerates.

The Ouachita Mountains were uplifted across the state during the succeeding Pennsylvanian period; this provided a nearby source of sediment for shale and sandstone, along with more marine limestone deposition.

The strata consist of massive limestone sequences deposited when the entire region was submerged under the Western Interior Seaway, during the last great marine transgression.

The modern coastal plain formed during this time; it comprises increasingly thick sediments (perhaps 15 km deep at the coastline) deposited southeastward into the downwarping Gulf of Mexico.

[1] Later crustal extension created a series of alternating horsts and grabens similar to those in the Basin and Range Province of the western U.S. A late Cenozoic uplift of the Rocky Mountains led to the deposition of a vast fan of eroded sediment to their east, forming the Ogallala Formation that covers much of the Panhandle.