Evidence of structural complexity of the lower crust and upper mantle from seismic reflection profiling

Abstract

Abstract Recent field work by the Consortium for Continental Reflection Profiling (CCORP) in the Rio Grande Rift near Socorro, N.M. and in the Wind River Uplift area of SW Wyoming suggests that the lower crust and upper mantle in these regions show considerable complexity. Preliminary analysis of 52.5 km of 24-fold CDP reflection profiling results across part of the Green River Basin and onto the Wind River Uplift indicates a fairly continuous reflector, possibly the Moho, exhibiting apparent offsets and topography. Several relatively strong, though generally discontinuous, sub-Moho reflections are apparent under both the Green River Basin and the Wind River Uplift, at two-way travel times of at least 15 seconds (approx. 45 km—total recording time was 30 seconds). Initial results from the Rio Grande Rift area (127 km of 24-fold results, 25 seconds recording time) provide further evidence for Sanford's mid-crustal magma body as well as for discontinuous deeper reflectors, and suggest striking high-angle megastructure in the western part of the Rift north of Socorro. These results provide high resolution evidence of lithospheric structural contrasts between a tectonically active and a tectonically (relatively) stable part of the North American continent.