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The AAPG/Datapages Combined Publications Database

Rocky Mountain Section (SEPM)

Abstract


Mesozoic Systems of the Rocky Mountain Region, USA, 1994
Pages 181-216

Reconstruction of the Early Mesozoic Cordilleran Cratonal Margin Adjacent to the Colorado Plateau

John E. Marzolf

Abstract

Comparison of palinspastically restored lower Mesozoic tectonosequences near the latitude of Las Vegas, Nevada and on the Colorado Plateau with equivalent tectonosequences in the northwestern Nevada Mesozoic marine province suggests that the latter lay in western Utah and eastern Nevada during the early Mesozoic (state boundaries fixed relative to the Colorado Plateau). On the Colorado Plateau, lower Mesozoic stratigraphy is subdivided by regional unconformities into the Moenkopi, Holbrook, Chinle, Dinosaur Canyon, Glen Canyon, and lower San Rafael tectonosequences. Each unconformity is indicative of significant tectonic reconfiguration of the sedimentary basins in which the tectonosequences were deposited and each tectonosequence records the depositional history within a different tectonic setting. During deposition of the Moenkopi tectonosequence in the Early Triassic, the western margin of cratonal North America was bounded by a passive-margin-like sedimentary prism extending from southeast Idaho to western Arizona and northwest Mexico. The prism was constructed on folded and thrust-faulted Permian and older rocks on the distal side of a peripheral foreland basin formed subsequent to accretion of Sonomia. The Holbrook and Chinle tectonosequences record uplift and volcanism, and erosion of the southern margin of the North American craton from early Anisian through middle Norian, and progradation of major deltas northwestward across the cratonal shelf from late Carnian through middle Norian time. Deposition of the Dinosaur Canyon tectonosequence records relative volcanic quiescence on the south coeval with westward progradation of the cratonal margin. The Glen Canyon tectonosequence records Sinemurian to Aalenian development of a Jurassic continental-margin arc and back-arc, arid-climate deposition of the Glen Canyon Group coeval with initiation and continued left-lateral motion on the Mojave-Sonoran megashear. Bajocian through Bathonian deposition of the lower San Rafael tectonosequence included a voluminous, eastward-displaced outburst of silicic volcanism accompanied by north-to-south marine transgression in the back-arc basin. The present left-lateral offset between the western Nevada Mesozoic marine province and Mesozoic terranes to the south was created by back-arc extension accompanied by rapid left-lateral motion on the Mojave Sonoran megashear in the late Middle Jurassic.


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