Deep Structure of Phanerozoic Basins in Southwestern North America: Tectonic and Exploration Implications

KELLER, G. RANDY, Department of Geological Sciences, University of Texas at El Paso, El Paso, TX 79912 915-581-5257 [email protected]

Southwestern North America is an excellent place to study the structure and evolution of sedimentary basins. The area contains extensive hydrocarbon resources and has experienced a complex Phanerozoic tectonic evolution beginning with the break-up of the Rodinian supercontinent in the Neoproterozoic/Cambrian. This break-up involved much rifting in the region and established the tectonic framework for the much of region that has influenced the development of many younger structures. In addition, the rifting created sedimentary basins along the margin and in the continental interior that have in many cases survived to the present. In at least some cases, these strata contain both source and reservoir rocks. Throughout the southwest, the number of wells that have drilled completely through the Ellenberger Formation and equivalent units is relatively small. Also, many “basement” tests are questionable due to the many Tertiary intrusions present. There remain many unknowns, but it seems clear that significant thicknesses of prospective strata lie beneath the lower Paleozoic in many areas of the southwest. Thus, there is frontier defined by stratigraphic depth. In addition, younger structures such as those associated with the Ancestral Rocky Mountains have often been affected by older rift structures preserving significant thicknesses of Paleozoic strata. The formation of the Ancestral Rocky Mountains is an enigmatic and globally significant episode of intraplate deformation. Recent geophysical and drilling results are documenting the diversity large size of the structures associated with this orogeny. Finally, the Laramide orogeny and the formation of the Basin and Range/ Rio Grande rift are both complicating factors and exploration opportunities.