ABSTRACT: Marathon Foreland Uplifts and Flexure of Adjacent Basinal Areas, Permian Basin, Texas and New Mexico

YANG, KENN-MING, and STEVEN L. DOROBEK, Texas A&M University, College Station, TX

The Permian basin is in the foreland area of the late Paleozoic Marathon orogenic belt. The Central Basin platform-Ozona arch complex are large scale uplifts which trend at variable angles to the Marathon thrust front. These uplifts are bounded by complex fault systems that were activated at the same time as deformation in the Marathon orogen.

Removal of postorogenic sediments and decompaction of synorogenic sediments above lower Paleozoic strata in the Permian basin produces restored stratigraphic cross sections that provide some idea of the form of the foreland deflection resulting from tectonic loading by the Marathon orogen. Restored cross sections that are oriented at high angles to the Marathon thrust front have profiles that are difficult to attribute entirely to flexure. The wavelength of the deflection across the foredeep suggests very low flexural rigidities for the foreland lithosphere. Calculated rigidities are on order of 1021-10 Nm. In addition, the amplitude of the deflection in the proximal foredeep (up to 6 km) seems abnormally high for best estimates of the topographic load produced by the Marathon orogen. /P>

The Ozona arch and Fort Stockton block (southernmost parts of the Central Basin platform) are located in the presumed forebulge area of the flexed lithosphere. Profiles that trend perpendicular to the Marathon thrust front and across these uplifts have complex forms that are not characteristic of lithospheric flexure. Weak lithosphere in the Marathon foreland may explain the complex cross-sectional profiles of the forebulge areas and the magnitude of the deflection in the proximal foredeep.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)