Sedimentology and revised nomenclature for the upper part of the Upper Triassic Chinle Formation and the lower Jurassic Wingate Sandstone, northwestern New Mexico and northeastern Arizona
Russell F. Dubiel
Sedimentologic and stratigraphic study of the Upper Triassic Chinle Formation in the area around the Defiance uplift in northwestern New Mexico and northeastern Arizona indicates that the uppermost Petrified Forest, Owl Rock and Rock Point members were deposited in fluvial, lacustrine and eolian environments. A Late Triassic age for Owl Rock and Rock Point fossils compared to an Early Jurassic age for palynomorphs from rocks equivalent to the overlying Wingate Sandstone, and lithologies of the Owl Rock and Rock Point members related to depositional environments, indicate a closer affinity of the Rock Point to the Chinle Formation than to the overlying Wingate Sandstone. The Rock Point Member contains mudflat, eolian sand-sheet and eolian dune deposits, and represents a transition from underlying Owl Rock fluvial and lacustrine systems to overlying eolian erg deposits of the Wingate Sandstone. The Rock Point is here recognized as a member of the Chinle Formation, and the name of the overlying Lukachukai Member is here abandoned in favor of the name Wingate Sandstone. Recurrent stratigraphic problems underscore the need for continued research on depositional environments, the designation of a type section for the Wingate Sandstone and recognition of the stratigraphic position of the Triassic-Jurassic boundary and regional unconformities.
- Dubiel, Russell F., 1989, Sedimentology and revised nomenclature for the upper part of the Upper Triassic Chinle Formation and the lower Jurassic Wingate Sandstone, northwestern New Mexico and northeastern Arizona, in: Southeastern Colorado Plateau, Anderson, Orin J.; Lucas, Spencer G.; Love, David W.; Cather, Steven M., New Mexico Geological Society, Guidebook, 40th Field Conference, pp. 213-223.