| OCR Text |
Show 121 Tidwell Member of the Morrison Formation overlies the Summerville Formation. East of Moab, Utah and into western Colorado, the Tidwell Member overlies the Wanakah Formation, which is correlative with the upper Entrada Sandstone and lower Curtis Formation in the San Rafael Swell (O'Sullivan, 1980b, 1981a, 1992; O'Sullivan and Pierce, 1983) and intertongues with the Entrada Sandstone in the Four Comers area (Condon and Huffman, 1988; Peterson, 1988; O'Sullivan, 1996). East of the Black of the Gunnison National Monument in southwestern Colorado, the Tidwell Canyon Member directly overlies pre-Cambrian contact of the Tidwell Member with (Gilluly the and basement rock strata is underlying angular in the San Rafael Swell Reeside, 1928; Gilluly, 1929; McKnight, 1940; O'Sullivan, 1984) and in Henry Mountains (Hunt et aI., 1938). Peterson (O'Sullivan, 1992). The basal In contrast, 0' Sullivan (1984a, 1992) and (1988) have demonstrated that the Tidwell Member interfingers with overlying Salt Wash Member regionally across the the western Colorado Plateau. Correlations Regional Across much of the western Colorado Plateau, the Tidwell Member is recognized According as to the base of the Morrison Formation this stratigraphic framework, by the USGS stratigraphy. the Summerville Formation that underlies the Tidwell Member in the San Rafael Swell "is truncated beneath the J-5 between the Green River and Moab, Utah (O'Sullivan, 1980a, 1984a, 1991). National Park, the Tidwell Member red beds of the Entrada Sandstone Comers area, the USGS unconformity directly (or the Curtis Formation). stratigraphy recognizes a overlie the Moab In Arches Tongue Member In southeastern Utah and the Four separate formation, the Wanakah Formation, which underlies the Tidwell Member and the J-5 unconformity (Figure 35). |
