Geological, Geochemical, and Geophysical Studies by the U.S. Geological Survey in Big Bend National Park, Texas.

摘要

Geologic features in Big Bend National Park (BBNP) formed from repetitive cycles of rifting, mountain building, basin development, faulting and folding, and volcanism and plutonism. The oldest tectonic episode recorded in the park is mountain building associated with the Marathon orogeny, which deformed he rocks in the park region from Middle Mississippian to Early ermian time (about 330285 Ma). During this episode, deep oermian time (about 330285 Ma). During this episode, deep thrust northwestward onto the edge of the North American continent by collision between the North and South American plates. From the Late Triassic into the Late Cretaceous (about 20085 Ma), the BBNP area experienced subtle effects of rifting between the North and South American continents; this rifting largely controlled the opening of the Gulf of Mexico. Drifting largely controlled the opening of the Gulf of Mexico. carbonate platform where the sediments that would become Lower and Upper Cretaceous limestone and shale units were deposited in shallow, open-marine water.The Late Cretaceous to early Tertiary Laramide orogeny (about 7050 Ma) had significant influence on the tectonic evolution of BBNP. This period of contractional deformation produced major uplifts, basins, and faults and folds that formed from northeast-directed compression related to collision between the North American continent and the Pacific/Farallon plate at the western edge of the continent. Major Laramide features in BBNP include the northeast-facing Mesa de Anguila, an uplifted monocline on the southwest margin of the park, and the southwest-facing Sierra del CarmenSantiago Mountains, an uplifted and thrusted monocline bounding the east part of the park. The Tornillo Basin developed between these uplifted basin margins.