Crustal velocity structure of the Omineca and Intermontane Belts, southeastern Canadian Cordillera

摘要: We provide information on the physical properties across two important morphogeological regions of southeastern Canadian Cordillera, Omineca and Intermontane Belts, tie together previously interpreted wide-angle seismic lines which have separately probed each zone along strike. The data analyzed here, Line 7 Lithoprobe's 1990 Southern Cordillera Refraction Experiment in southern British Columbia is a 410-km profile from Fraser River to Radium Hot Springs near Rocky Mountain Trench. Iterative forward inverse modeling travel times, constrained by amplitude characteristics earlier cross-line interpretations, defines thin crust with relatively low velocities. upper has an average thickness 15.3 km P wave velocity less than 6.1 s -1 velocities at bottom reaching 6.2 - 6.3 . It further characterized gradients decrease markedly depth low-velocity trends correlate traces crustal-scale shear zones. A high-velocity region west end coincident major uplift structure. midcrust 9.2 below except for extreme profile. This midcrustal (LVZ) Belt partly Belt. lower crust, 24 34 depth, averaging 6.6-6.7 Higher deep may mark westward extent North American cratonic rocks Okanagan Valley. mantle 8.0 5-increasing 8.2 maximum ray penetration 48 km. model presented here compliments well interpretations vertical incidence reflection profiles. structure especially LVZ, closely correlates regional isotherms. While there seems be no well-defined boundary between are distinct differences neighboring Coast Plutonic Complex west. much belts consequence temperature control parameters crust. lithosphere clearly anomalous respect northwest America, terms crustal structure, it similar only Basin Range province United States.