Abstract

The Central Basin Platform (CBP) is an important tectonic element in the subsurface of the Permian Basin region. It is a major intraforeland uplift that trends at high angle to the Marathon fold-and-thrust belt. This study examined structural features across the southwestern Midland Basin and eastern CBP along with a compilation of published information from the eastern Delaware Basin and other parts of the CBP in order to document the tectonic history of these areas.

Structural interpretation from seismic data, structure contour maps, and structural cross sections show that the southwestern Midland Basin, interior CBP, and eastern Delaware Basin are characterized by NW-SE trending en echelon folds. These folds are typically asymmetric in cross-section with the steeper limb of the fold being cut by steeply dipping reverse faults that trend sub-parallel to fold axes. The folds are arranged in a right-stepping en echelon pattern with low obliquity to the boundary fault zones of the CBP. At a larger scale, the CBP consists of two main crustal blocks that also are arranged in en echelon pattern with steeply dipping reverse and thrust faults, asymmetrical flower structures, and a few normal faults at boundaries. The western margin of the CBP has greater structural relief, vertical separation, and basement shortening than the eastern margin. The dominance of contractional structures and en echelon arrangement of these structures in map view indicate that the CBP and adjacent areas formed in a right-lateral convergent strike-slip (transpressional) tectonic setting.

A simple geometric method was applied to evaluate the slip motions along the boundary faults of the CBP. Geometric analysis shows that the NNW-NW trending boundary faults were subjected to right-lateral convergence-dominated oblique-slip deformation, whereas the ENE-WSW trending boundary faults were subjected to left-lateral strike-slip dominated oblique-slip deformation. The derived slip motions along the boundaries of the CBP explain the wide variety of structural features observed and also agree with previously proposed models that involve clockwise rotation of crustal blocks within the CBP.

The structural patterns associated with the eastern Delaware Basin, CBP, and western Midland Basin can be explained by considering these areas together as a transpressional deformation zone. Three stages of deformation can be recognized based on significant changes in the style of the deformation and by the area of active deformation through time. An initial NE-SW directed compressive stress caused minor en echelon folding across parts of the eastern Delaware Basin, CBP region, and western Midland Basin during late Mississippian-middle Pennsylvanian time. After a middle Pennsylvanian phase of relative tectonic quiescence, renewed and amplified compressive stress in late middle Pennsylvanian time generated right-lateral convergent shearing across the transpression zone and was responsible for the formation of regionally distributed en echelon faulted anticlines. During late Pennsylvanian-Wolfcampian time, strain partitioning occurred within the transpression zone. En echelon folding within the sub-basins ceased, but continued right-lateral oblique slip across the transpression zone was accommodated along the boundaries of the CBP, where pre-existing basement weaknesses were reactivated as high-angle faults. Major uplift of the CBP occurred during this last phase of late Pennsylvanian-Wolfcampian deformation.

The tectonic relationships between the subtle structures within the sub-basins and the CBP are an example of the sequential development of structures that can develop during progressive transpressional deformation across a foreland basin. Our study of the CBP and adjacent areas may provide insight into the origins of similar intraforeland basement uplifts that developed elsewhere across the interior of the North America during late Paleozoic time.