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Geometric and Lithic Variability within the Syndepositional Cave Graben Fault System, Guadalupe Mountains, New Mexico

Abstract

Permian Capitan shelf margin exposures in Rattlesnake and Slaughter Canyons in the Guadalupe Mountains, New Mexico, reveal a complex syndepositional fault and fracture system which has developed as a result of gravitational loading and differential compaction on, and in front of, the early cemented Guadalupian 24 (G24) shelf margin reef. Extensive syndepositional deformation within the Permian Capitan depositional system is known to have influenced the stratigraphic architecture of the system, as well as diagenetic patterns and karst development, and may influence the reservoir properties of the shelf margin system. A real-time kinematic GPS was used to map faults and fractures exposed on the canyon walls, while high-resolution digital imagery and airborne lidar provide a context for 2 and 3-D visualization and interpretation. Detailed mapping of the fault system reveals a complex deformational history and high degree of variability in fault geometry, including the presence of vertical and lateral fault relays, highly variable fault apertures, and variable fracture intensity and strain magnitudes with distance from the main faults and within different stratigraphic units. Fault breccias ranging from less than a centimeter to several meters in aperture contain entrained sediment and clasts of variable age and composition. Deformation zones extend up to tens of meters in width and stratal geometries near the faults are characterized by thickness changes and inclined bedding. Integration of the fault geometry, stratal relationships, and breccia fills has revealed an episodic growth of the Cave Graven Fault System, which can be compared to previous work in Slaughter, Rattlesnake, Walnut, and Dark Canyons. This comparison highlights a variable fault cessation and reactivation sequence for each canyon over the G24 through G30 high frequency sequences.