Seismic Vp & Vs tomography of Texas & Oklahoma with a focus on the Gulf Coast margin

The northwestern Gulf of Mexico passive margin contains an extensive record of continental collision and rifting, as well as deformation associated with orogenic events and heavy sedimentation. Seismic traveltime tomography that incorporates new data from 328 broadband seismic stations deployed throughout the region reveals features that correlate well with expected mantle structures, as well as features that have no obvious expression at the surface. Among the former are a large fast anomaly that corresponds to the southern extent of the Laurentia craton and a large slow anomaly associated with the Southern Oklahoma Aulacogen. Among the latter are a slow layer that we interpret to be a shear zone at the base of the cratonic and transitional continental lithosphere, a zone that is bounded at its top and bottom by discontinuities and high levels of seismic anisotropy identified in companion receiver function and shear wave splitting studies, respectively. A high velocity body underlying the Gulf Coastal Plain may mark delaminating lower crust. If this is true it could provide indirect evidence for an elevated geotherm during the rifting process that created the Gulf of Mexico.