Following the ending of rifting in the Late Cretaceous to the early Cenozoic, the Big Bend area was subjected to the Laramide orogeny. This period of (now east–west) compression caused the northeast-facing Mesa de Anguila (an uplifted monocline on the park's southwest margin), the southwest-facing Sierra del Carmen–Santiago Mountains (an uplifted and thrust-faulted monocline that forms the park's boundary on the east) and the Tornillo Basin. During the middle Cenozoic, most of the volcanic rocks, including the Chisos Group, the Pine Canyon caldera complex, and the Burro Mesa Formation, formed.
