Big Bend National Park and adjacent Big Bend Ranch State Natural area lie within the Trans Pecos Region of West Texas. Here are found extensive Tertiary, intrusive and extrusive igneous rocks, including dikes, sills, laccoliths, ash flows, calderas, and lava flows. Major deformational events affected the region during the Paleozoic, Cretaceous and Cenozoic. These deformations created folds including anticlines, synclines, and monoclines as well as faults including normal faults, thrust faults, strike-slip faults, and grabens. A variety of fossils and minerals occur throughout the area.
Santa Elena Canyon is one of the outstanding geologic locales locales in the Big Bend region. It is probably the most striking exposure of Cretaceous rocks in North America.
Spectacular exposures of many kinds of faults abound in the Big Bend region. Some were formed during the Ouachita deformation, many were formed during the Laramide deformation, and others were formed during the Basin and Range deformation.
Folds were created during the Ouachita deformation and during Laramide deformation. The Ouachita folds are best displayed in the Solitario or just north of the national park along the road to Marathon. Laramide folds are found at Persimmon Gap, throughout the Sierra del Carmen Range, at Terlingua monocline, and in Mesa de Anguila.
An excellent reference to the state park is Geology of Big Bend Ranch State Park, Texas by C.D. Henry and a good reference for the national park is The Big Bend of the Rio Grande by R.A. Maxwell. Both contain geologic maps and are available from the Bureau of Economic Geology.
This is a Digital Elevation Model (DEM) of Big Bend National Park (right half) and Big Bend Ranch State Natural Area (left half). It was constructed from a mosaic of fifty five 7.5' quadrangles. An enlarged, more detailed view of the red square is shown below. Width of Image is 80 miles.
Shown below is a little more of the detail available on the above DEM.
Several interesting features are obvious on this DEM. Trending WNW from the lower right corner is the Terlingua monocline. Trending NE-SW in the north half are several faults that have both normal and strike-slip displacement. One can determine the sense of up-down displacement from the topography. (Dark blue is highest elevation, yellow-green is lowest.) The circular, blue feature in the middle is the Black Mesa laccolith. Width of Image is 6.5 miles
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