Superposed deformation in the Santiago and northern Del Carmen Mountains, Trans-Pecos Texas
— Robert C. Cobb and Stephen Poth

Persimmon Gap, the northeast entrance to Big Bend National Park, lies astride a northwest-trending segment of the Santiago Mountains. Structural features in the Santiagos and northern Del Carmen Mountains display evidence of two periods of deformation. Laramide compressional deformation produced the southwest-facing reverse-faulted monocline of the Santiagos. Reversal of slip during Basin and Range extensional deformation used steep segments of the Laramide fault planes to produce high-angle, normal faults. The regional pattern suggests a strike-slip component of movement along the Texas Lineament: left-lateral during the Laramide episode and right-lateral during Basin and Range time (see also Muehlberger, this guidebook).