RICE 3–D Reflection and Tomography Experiment: Hill AFB, OU–2, Utah: July–August 2000
The Deep Probe Working Group
The 1995 Deep Probe active source seismic experiment, a continental-scale long-range refraction investigation, extended from the North American orogenic plateau into the Archean Laurentian craton. The seismic profile crossed Proterozoic terranes of the southern Rocky Mountains and Colorado Plateau and the southern part of the Archean Wyoming province, both modified by Phanerozoic tectonism, as well as the northern Wyoming province and the Archean Hearne province, both relatively stable since Archean time. The results suggest that present-day seismic structure is as much controlled by initial terrane accretion as by recent tectonism. Each province is associated with a distinct crustal type, with the Wyoming province crust being thickest and fastest. The data show that the change from low to high upper mantle seismic velocity passing from the orogenic plateau to the shield seen in teleseismic tomography images occurs abruptly in the vicinity of the Cheyenne Belt, which separates the Proterozoic Rocky Mountain terranes from the Archean Wyoming province. The Phanerozoic upper mantle beneath the southern Rocky Mountains has a well-developed P-wave low velocity channel similar to that found beneath the Gulf of California spreading system. The upper mantle beneath the Archean provinces has no low-velocity zone, but resembles the teleseismic average for the Canadian shield.