Intra-cratonic Volcanism in the Colorado Plateau and Association with Basin and Range Rifting

William J. Sercombe¹ and Thomas W. Radford^2
1bp, Houston, TX
²BP, Calgary, AB

The Yellowstone Absaroka volcanics have been previously attributed to a volcanic ‘hot spot' suggesting that they occur as the North American plate moves over a mantle plume.A wider review of public domain data on tectonics, volcanic occurrence and general geology suggests that Yellowstone is at the apex of the north-south indentation of the profound Wasatch/Mogollon rift system which separates the Tertiary Basin and Range extension province from the Colorado Plateau and North American craton. West of Yellowstone the volcanics of the Snake River down-warp, Columbia plateau and Basin and Range do not indicate consistently younger age dating of volcanics to the east as a hot spot would require. The magnitude of areal coverage of the western Tertiary volcanics does not indicate a unique single traverse of volcanic activity. This volcanic rift indentation is also comparable to the north-south Rio Grande volcanic dominated rift to the east which extends deep into central Colorado from Mexico and separates the Colorado Plateau from the interior craton. The Colorado Plateau contains numerous volcanic fields such as the San Francisco and Zuni-Bandera volcanics. The intensity of volcanism decreases eastwards away from the major rift settings. This decrease in volcanism is also associated with a decrease in extensional tectonics away from major rifts. Extensional features include the very deep but narrow inter-montaine Big Hole basin. The mechanism of volcanics traveling through dilation on faults associated with major rifts would explain the intra-cratonic volcanics and north-south trending rift volcanics more consistently than east-west traverse of volcanics over single hot mantle plumes.

AAPG Search and Discovery Article #90072 © 2007 AAPG and AAPG European Region Conference, Athens, Greece