Steven L. Dorobek2
(1) Texas A&M University, College Station, TX
(2) Texas A&M University
Abstract: Late Pennsylvanian-early Leonardian tectonic history at Wilshire field and adjacent areas, west-central Upton County, southwestern Midland Basin, West Texas
Wilshire field is one of several oil and gas fields situated along the Pegasus-Amacker structural trend in the subsurface of west-central Upton County. It is characterized by a north-south trending fault system that formed during late Paleozoic time. This study examined the late Paleozoic stratigraphic architecture and structural features at Wilshire field and adjacent areas in order to constrain the timing of deformational events and resultant effects on late Paleozoic deposition in the southwestern Midland Basin.
Before Missourian-Virgilian time, the study area was a tectonically stable region dominated by extensive shallow-water carbonate sedimentation. Soon after deposition of Strawn carbonate ramp facies, tectonic deformation occurred in the western and eastern parts of the study area. The eastern part is characterized by an asymmetric anticline cut by a basement-involved fault system. The western part is bounded by the uplifted Central Basin Platform, which is dominated by strike-slip styles of deformation. The overlying upper Pennsylvanian through lower Leonardian interval represents a synorogenic sedimentary wedge that prograded from the Central Basin Platform. The study area returned to tectonically stable conditions during development of middle-upper Leonardian carbonate platforms, which built away from remnant structural highs that formed during the previous deformation.
Differential truncation of the Strawn Formation across the study area can help to estimate the structural relief and constrain the relative timing of late Paleozoic deformation events across the southwestern Midland Basin. Compared with the Central Basin Platform, the Wilshire structure had much lower structural relief and a shorter deformational history.
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana