Abstract

The Central Basin Platform (CBP) of West Texas is composed of six structural subprovinces, which moved independently during the Ouachita orogeny. Although the dominant fault movement in the CBP is vertical, sufficient oblique-slip movement between the six mega-blocks produced localized strike-slip structures. This paper proposes a tectonic model for formation of the CBP that is useful for predicting the orientation and spacing of these fault systems.

Of the six subprovinces of the CBP, the three structurally highest: the Fort Stockton, Sand Hills and Lea-Andrews blocks, all show positive gravity and magnetic anomalies. These county-sized blocks (35 x 80 km) are: 1) bounded by strike-slip faults that involve basement uplift; 2) have maximum structural deformation along their margins where bends in the fault systems enhance compression; and 3) trap the majority of oil in high-angle fault structures along the block boundaries. Significantly less oil accumulates in unconformity traps in the relatively undeformed centers of the blocks. These three mega-blocks are separated by three other zones that are characterized by gravity and magnetic lows, R-shears, and en echelon folding.

Structural mapping shows a transition in tectonic style from left-lateral shear in the southern portion of the CBP, to right-lateral shear in the north. Transfer of these opposing stresses occur along a structural sag in the central portion of the CBP in Winkler and Ector Counties. Strike-slip fault systems in West Texas are subtle; however, regional fault fabric analysis shows that the various individual fault segments are parts of through-going strike-slip systems. Understanding the regional distribution of these faults will aid in recognition of undiscovered traps.