Sp receiver function imaging of a passive margin : transect across Texas’s Gulf Coastal Plain.

A Sp receiver function common conversion point (CCP) stacked image beneath Texas Gulf Coast Plain (GCP) reveals anomalies that may be detached lower crust sinking into the mantle. The detached crust may have resulted from distinct episodes of delamination as the lower crust peeled away from the upper crust. The apparent presence of delaminated crust in the mantle indirectly points to a thermal anomaly in the mantle that may have initiated the rifting episode that created the Gulf of Mexico. The CCP stacked image also reveals a significant structure with negative polarity ~110 km beneath the array. Discontinuities of this polarity at this depth have been interpreted elsewhere as the lithosphere-asthenosphere boundary (LAB) and this interpretation is consistent with previous results for this region. The observed variations in amplitudes of Sp conversions at this “LAB” discontinuity may be produced by large contrasts in seismic anisotropy created by a shear zone.