Abstract

Redefinition of the Colorado Plateau in tectonostratigraphic terms suggests the hypothesis that the Colorado Plateau is a major regional blind thrust plate. The abundance of tectonically displaced salt along Plateau margins further suggests a reason for the relative structural simplicity of the Plateau. This hypothesis is supported by the recognition that the sub-thrust sedimentary package of the Wyoming Thrust Belt is present at the same crustal elevation in drill holes in the region from Moroni to the Sevier River valley, which is along the western Plateau margin. The elevation of the top Jurassic salt horizons in this sub-thrust package is about 3.5 kilometers below sea level. The elevation of the top of a low velocity layer in a reversed refraction seismic line from Hanksville to Chinle is also about 3.5 kilometers below sea level. Balanced cross sections on listric normal faults in the well-exposed Grand Canyon region suggest a major regional detachment at about 3.5 kilometers below sea level. Paleomagnetic data suggest that the Plateau has moved northward 160 km ± 36 km relative to North America since the Triassic. The thrust hypothesis usefully suggests tectonic models for many of the margins of the Colorado Plateau plate.