Print this pageWest-central Arizona and southeastern California represent a key region in reconstructing the Early Mesozoic depositional and tectonic history of southwestern North America. Although subsequent deformation, metamorphism, and magmatism obscure the original relations of the metasedimentary rocks of this region to units of the Colorado Plateau, stratigraphic correlation can still be made based on stratigraphic position, depositional environment, volcanic components, and regional uplift events.
The Buckskin Formation is a regional unit commonly consisting of four informal members. The two lower members correlate to the Lower and Middle(?) Triassic Moenkopi Formation, and the two upper members probably correlate to the Upper Triassic Chinle Formation. The Vampire Formation overlies the Buckskin Formation along a basal angular unconformity. This unconformity represents an important uplift that exposed Proterozoic basement rock and is equivalent to the regional J-O unconformity of the Colorado Plateau.
The Vampire Formation has two regional members: a lower metaconglomerate member and an upper quartzite member. The metaconglomerate member probably correlates to the Lower Jurassic undivided Moenave/Kayenta Formation (Glen Canyon Group), and the quartzite member correlates to the Lower Jurassic Navajo-Aztec Sandstone (Glen Canyon Group). The similar geologic histories of west-central Arizona and southeastern California and the Colorado Plateau for Triassic and Early Jurassic time implies a significant paleogeographic and depositional connection between them.
AAPG Search and Discovery Article #90925©1999 AAPG Foundation Grants-in-Aid