Jason W. Currie¹, Kevin J. Smart¹

(1) University of Oklahoma, Norman, OK

ABSTRACT: Microstructural Analysis of Pennsylvanian Sandstones: Implications for the Ouachita Mountains Kinematic Development

The Ouachita tectonic system, like the Appalachians, formed following collision of Laurasia and Gondwana during the final assembly of Pangea in the Late Paleozoic. The clastic-dominated Ouachitas, however, contrast with the Appalachians and its thick, lower Paleozoic carbonate sequence. This study area offers an opportunity to study foreland structural processes in a clastic-dominated fold-thrust system.

The Choctaw fault separates imbricated Pennsylvanian strata in the Ouachita frontal zone from the mildly-deformed, Pennsylvanian and younger Arkoma Basin. Although, macrostructures in the frontal zone are well-studied, the complete kinematics of this system, particularly small-scale processes, remains incomplete. Here, microstructural analyses are used to more fully constrain the kinematic development of the frontal zone and Arkoma Basin. The data set yields information on variations in shortening direction and intensity along with data on the relative timing of thrust movements.

The target units are the Pennsylvanian Spiro sandstone in the frontal zone and Pennsylvanian Krebs Group sandstones in the Arkoma Basin. These units are well-exposed in the study area, and provide appropriate markers for detailed microscale strain analysis. Oriented samples will be analyzed with thin sections that are photographed under transmitted light and cathodoluminescence. Normalized Fry and Rf/f methods will yield finite strains that can be analyzed with maps and cross-sectional profiles. Abundance and relative timing of microscale deformation mechanisms will be determined via systematic point-counting of microstructures. This work complements on-going research on Ouachita structural development and provides a starting point for more complete and systematic kinematic analyses of the Ouachita tectonic system.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado