Laramide age development of the Terlingua-Solitario push-up structure was investigated by field mapping, experimental study, and theoretical analysis. Field mapping suggested a four-stage development involving Laramide age compression followed by Basin and Range age tension. The push-up structure is composed of Cretaceous limestones, shales, and marls. Thick competent units of limestone (rigid plates) are imbedded within thick formations of thinner bedded incompetent shale and marl. Deformation occurred when the tectonic load rose to sufficient magnitude to overcome the strength of the competent units. The Santa Elena Limestone was investigated experimentally to determine its burial depth and mechanical properties. The critical buckling stress and the state of stress were then determined within the Santa Elena, using field mapping to establish ''boundary conditions'' for the theoretical work. Plate bending theory, linear elasticity, and fracture mechanics were used to describe incipient deformation of the push-up structure. The critical stress required to initiate cylindrical bending was calculated at 7.9 MPa (79 bars) and reflects the regional Laramide tectonic stress acting on the outer edge of the Santa Elena plate. The state of stress within the plate was determined by linear elasticity theory combined with Laramide tectonic strain measurements. Compressive principal stresses of 209.2 MPa (2092 bars), 40.8 MPa (408 bars), and 18.6 MPa (186 bars) were calculated and are much higher in magnitude than the critical stress. However, near preexisting flaws (i.e., pore space, microcracks), tensile stresses of several hundred bars are required by fracture mechanics. This local tensile loading caused small cracks to propagate and eventually to coalesce to form joints and fractures, many of which later developed into strike-slip and dip-slip faults parallel to Laramide &sgr;1. ¿ American Geophysical Union 1992