Three-Dimensional Geometry and Kinematics of the Gale-Buckeye Thrust System, Ouachita Fold and Thrust Belt, Latimer and Pittsburg Counties, Oklahoma

Abstract

The Gale-Buckeye thrust system consists of a series of blind thrusts and associated folds near the boundary between the Ouachita fold and thrust belt and the Arkoma basin in Oklahoma. A dense grid of high-resolution seismic reflection data, augmented by data from exploration and production wells, provides a unique opportunity to analyze the three-dimensional geometry and kinematics of these structures in detail. Results from our interpretation provide new insight into the extent, style, and sequence of thrusts within the Gale-Buckeye thrust system, and contrast with previous models for the region. Specifically, we recognize two previously unmapped transverse structures in the Gale-Buckeye thrust system: a sharp, left-stepping zone of oblique ramps, and a tear fault within the Gale thrust sheet. These transverse structures are spatially coincident with similar structural trends in lower Paleozoic strata beneath the thrust system as well as outcropping structural trends on the surface. This interpretation extends thrusts in the Gale-Buckeye system to minimum strike lengths of 7-9 mi (11-15 km) and fault length-to-displacement ratios of about 10:1. Furthermore, interpreted structural relationships suggest that the Gale and Buckeye thrusts formed in a backward-stepping manner, a new interpretation for faults in this system. Measurement of differential transport angles from our interpretations of the Gale-Buckeye thrust system indicates that along-strike displacement variations of the Gale and Buckeye thrusts are consistent with thrusts from other nonmetamorphic fold and thrust belts. Using the differential transport model, we infer that the tear fault in the Gale thrust sheet indicates a region that became segmented to accommodate excessive along-strike differences in displacement. In addition, we use the model to explain errors in previous interpretations of the Gale-Buckeye thrust system that resulted in the drilling of dry holes. Integrating realistic differential transport angles with our interpretations for extent, style, and sequence of thrusting provides new strategies for hydrocarbon exploration hroughout the region.