Deep Exploration Possibilities along the Ouachita Trend

KELLER, G. RANDY, University of Texas at El Paso, El Paso, TX

The late Paleozoic Ouachita orogeny produced a sinuous deformed belt that extends from Alabama through Mississippi, Arkansas, Oklahoma, Texas, and finally southward into Mexico. Although this orogenic belt has been studied for many years, it is poorly understood because exposures are very limited and most drill holes stop once low grade metamorphic Ouachita facies rocks are encountered. However, recent geophysical studies have provided important new data that make it possible to reevaluate exploration possibilities along the Ouachita trend. A deep seismic study along a profile extending from the Ouachita Mountains in southwestern Arkansas into northwestern Louisiana has provided a surprisingly clear image of the early Paleozoic continental margin in the area. This margin is largely un eformed and suggests that the Ouachita orogeny involved little if any shortening of continental crust. Along with gravity data, this result implies that Ouachita thrusts are thin-skinned structures that include features such as the Benton and Broken Bow uplifts. Using these results as a base from which to build, we have been able to trace this margin southeastward into Mississippi and westward through Texas and into Mexico. Although some production has been established in Ouachita facies rocks, gravity anomalies and limited amounts of seismic data suggest that two subthrust plays have potential. The first is simply the extension of well known foreland basins (Arkoma, Fort Worth, Val Verde, etc.) beneath the thrusts, and our point is that these basins probably extend further than previous y believed. In addition, there are areas where completely new subthrust basins are possible. The second play is the early Paleozoic continental margin and rift basins that formed during the early stages of its development. Our results to data indicate that these features are not greatly deformed and are at economically drillable depths in many areas. However, the area south of the Paleozoic continental margin should be avoided because the thickness of Ouachita facies rocks exceeds 10 km.

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)