A Laramide-age push-up block: The structures and formation of the Terlingua-Solitario structural block, Big Bend region, Texas
The Terlingua-Solitario structural block represents a Laramide-age push-up block in the Big Bend region of Texas. Folding, thrust faults, monoclines, east-northeast-trending strike-slip faults and grabens, and tectonic stylolites are associated with push-up block development. Laramide-age east-northeast-directed compression caused sinistral movement on two east-trending, right-stepping, en echelon fault zones. This fault movement placed the area between fault overlap under transpression, which then responded by broad uplift on a northwest-trending fold axis. Local stratigraphic and structural controls suggest uplift initiation between 68-66 Ma with the completion of push-up block formation by about 50 Ma. This push-up block exists within a zone of transfer for Laramide sinistral faulting along the northern and southern boundary of the Texas Lineament zone. Laramide stress trajectories across the uplift as defined by tectonic stylolites indicate a single compressive event, but with stress, trajectory changes locally at developing structures. More recently, during Basin and Range age deformation (24 Ma), dextral movement along the two en echelon fault zones placed the structural block under transtension. Northwest-trending faults and grabens now cut through the eastern half of the push-up block and die out along the southern boundary of the uplift. Local dextral movement was also identified along some of these northwest-trending faults.