Possible tectonic controls on Late Triassic sedimentation in the Chinle Basin, Colorado Plateau
Lawrence H. Tanner
Patterns of deposition of the Chinle Group formations record the infl uence of arc magmatism and the organization of a mobile foreland basin system during Late Triassic time. Accumulation of basal Chinle strata was controlled by paleorelief on the Tr-3 unconformity surface. Subsequent deposition of the Petrifi ed Forest Formation may have been infl uenced by arc-related thermo-tectonic uplift, resulting in the Tr-4 unconformity. Depositional trends of the Owl Rock and Rock Point formations record the organization of elements of the Cordilleran foreland basin during Norian and Rhaetian time. Thinner packages of sediment were deposited over the crest of the forebulge and thicker sections were deposited in the backbulge axial basin. Migration of the forebulge, accompanied by regional uplift, caused incision of the Owl Rock depositional surface and formed an unconformity (the Tr-5) that cuts down to the west of the Four Corners area. Rock Point strata onlap the forebulge fl ank from east to west and are vertically gradational with overlying Wingate/Moenave strata. There is no evidence of a separate J-0 unconformity.
- Tanner, Lawrence H., 2003, Possible tectonic controls on Late Triassic sedimentation in the Chinle Basin, Colorado Plateau, in: Geology of the Zuni Plateau, Lucas, Spencer G.; Semken, Steven C.; Berglof, William R.; Ulmer-Scholle, Dana S., New Mexico Geological Society, Guidebook, 54th Field Conference, pp. 263-267.