THE SOUTHERN OKLAHOMA AULACOGEN: NEW INSIGHTS ON THE PALEOZOIC RIFT-RELATED AND INVERSION-RELATED STRUCTURES IN THE WICHITA UPLIFT

The Southern Oklahoma Aulacogen (SOA), defined by the Wichita and Arbuckle Uplifts to the southeast and the Amarillo Uplift to the northwest, remains an enigmatic feature in the tectonic evolution of the North American continent. The SOA evolved from a multiphase tectonic history consisting of initial rifting in the Cambrian during Rodina disassembly, later Paleozoic inversion during Pangea assembly and subsequent burial beneath less-deformed post-Pennsylvanian cover. Here, using high-resolution aeromagnetic, 2D seismic and magnetotelluric (MT) data, we investigate the Cambrian rift-related features and the Pennsylvanian inversion-related structures of the Wichita Uplift segment. 2D seismic and filtered aeromagnetic data provide impressive images of basement faults and mafic intrusions, and MT data resolves the crustal-to-lithospheric -scale structure of the SOA. Our results reveal three distinct tectonic domains within the SOA: 1) A western region where a ~80 km-long E-W-oriented strike-slip fault dominates the basement with a potential ~40 km of left-lateral offset. This fault and a ~100 km-long N-S –striking trough form a conjugate-pattern feature that defines the boundary between the Wichita and Amarillo Uplifts. 2) A central region that is dominated by mafic intrusions, which aeromagnetic data shows as having geometries consistent with vertical (dike) and saucer-shaped (sill) intrusions. Here, upward continuation of the aeromagnetic data reveals two distinct magnetic anomalies. The first corresponds to shallow mafic bodies, which do not extend beyond ~.5-1 km depth, while the other, a N-S magnetic feature, extends to ~5km depth, and is interpreted to be a feeder dyke for the shallower intrusions. 3) An eastern region where basement-related mafic features are less-evident and are mostly confined to the north. Overall, we find that the central and eastern regions are bounded to the south by a fault system that coincides with dike-related aeromagnetic lineaments, suggesting possible fault-bounded and fault-assisted magma plumbing during the Cambrian rifting event. We anticipate that the analyses of our MT survey will provide more insight into the lithospheric-scale structure of the SOA and reveal features that may represent the deep sources of magma that fed the Cambrian igneous intrusions.