Insights into the kinematic Cenozoic evolution of the Basin and Range-Colorado Plateau transition from coincident seismic refraction and reflection data

摘要: Estimates of surface extension in the southern Basin and Range province transition into Colorado Plateau range from a few percent to several hundred locally, yet crustal thickness varies perhaps only 10-15 km across these provinces. Within metamorphic core complex belt, extremely extended crust is directly juxtaposed against equally thick (or thinner) that underwent far milder extension. Unless preextension varied dramatically over short distance, must have maintained its during extension, through mechanisms involve flow magmatism. We employ 300-km-long profile seismic refraction coincident vertical-incidence reflection data investigate geophysical signature processes unextended Plateau. By integrating velocity with pattern reflectivity along profile, we estimate amounts Tertiary magmatism occurred. an upper bound 8 mafic material intruded beneath belt 4 5 Transition Zone province, respectively. emphasize this 8-km strictly bound, actual amount was probably less (3 km). further speculate kilo-meters silicic rock added via ductile flow. As suggested by numerous numerical models conclude mobile, felsic midcrustal layer accommodated most This appears be thickest terranes thinnest In contrast, lowermost thinned passively corresponds more regional