Temporal and spatial evolution of the Cave Graben Fault System, Guadalupe Mountains, New Mexico



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Numerous recent studies have demonstrated the importance of syndepositional faulting as an inherent element of steep-rimmed carbonate margins. However, these studies have not emphasized the relationship to older shelf margins, multiphase deformation history, and complexity of fault zone internal structure. In the Guadalupe Mountains, New Mexico, extensive syndepositional deformation parallels the Permian Capitan shelf margin reef and has developed in the absence of regional tectonic forces due to a combination of early carbonate cementation, gravitational instability, differential compaction, and variable progradation to aggradation at pre-existing shelf margins. This study focuses on the geometry, growth history, and internal fill type distribution within the Cave Graben Fault System (CGFS) in Slaughter and Rattlesnake Canyons of the Guadalupian (Capitan) shelf margin with the intent to understand the temporal and spatial evolution of deformation in front of the G24 shelf margin. Stratigraphy, faults and fractures exposed within the CGFS were mapped using high-resolution gigapan photos and GPS, along with RCRL Guadalupe airborne lidar, provides a geospatial database for 3D visualization, quantification, and interpretation. Detailed mapping reveals a high degree of variability in fault geometry, including the presence of vertical and lateral fault relays, antithetic and synthetic splays, and highly variable fault and fracture apertures, suggesting a complex deformational history. Hundreds of early-formed fractures have been mapped within the G24-G25 shelf margin system, but the development of significant faults with appreciable displacement only occurs in front of the G24 margin. Vertical fault displacement varies from 9 to 34 m in the CGFS. Breccias several meters in width fill the main faults and contain entrained sediment and clasts of variable age and composition. Stratal geometries reveal that movement and episodic growth occurred along the faults soon after deposition. Further investigation of the sediment and breccia fills suggests that a significant dissolution event along the fault allowed for the entrainment of much younger, post-Permian sediment. Based on these findings it appears that in Rattlesnake Canyon at least 30-60% of the CGFS vertical displacement occurs in the Permian, whereas up to 40-70% may develop post-Permian, providing a significant advancement in the understanding of timing of fault systems within the Capitan shelf margin.