Abstract Outcrops of Turonian through Campanian strata in the Kaiparowits Plateau of southern Utah provide a unique opportunity to examine both shallow-marine and continental strata within the context of unconformity bounded depositional sequences. This approach provides insights to the evolution of the strata within the plateau as well as regional chrono- and lithostratigraphic relationships within the southwestern Colorado Plateau. We recognize five unconformity-bounded depositional sequences. These sequences are defined by regional surfaces of erosion that juxtapose amalgamated fluvial deposits over shoreface, alluvial plain, or coal-bearing strata and reflect an abrupt basinward shift in facies tracts. Between these sequence boundaries transgressive and highstand systems tracts are recognized. Transgressive systems tracts are characterized by a progression from amalgamated channel deposits to isolated meanderbelts that have evidence of tidal influence within what is otherwise a wholly alluvial succession. These tidally-influenced fluvial deposits are temporally equivalent to marine maximum flooding surfaces. Early-highstand systems tract deposits are characterized by thick, aggradational shoreface parasequences, thick coal beds, and isolated meanderbelt sandstones encased in thick, fine-grained flood plain strata. Late-highstand systems tract deposits are relatively thin and are characterized by progradational shoreface parasequences, thin, discontinuous coal seams, and fine-grained channel deposits. We interpret these changes in stratigraphic architecture to reflect significant changes in stratigraphic base level that we have correlated to adjacent outcrop belts in the Wasatch Plateau of central Utah, at Black Mesa in northern Arizona, and the San Juan basin in New Mexico. We have compared our estimates of stratigraphic base level with those of Haq et al. (1988) and suggest some modifications in order to account for the observed stratigraphy throughout the southern Colorado Plateau. Recognizing cycles of base-level change has allowed us to synthesize our observations in the Kaiparowits Plateau and extend them across a broad region. Recognition of the relationship between sedimentary architecture and position within a sequence has resulted in a model that allows the geometry and interconnectedness of sedimentary facies to be predicted within the context of parasequence stacking patterns. This provides a useful tool for both exploration and development.

The Kaiparowits Plateau comprises a 2-km-thick sequence of Upper Cretaceous rocks. The oldest Cretaceous unit in the sequence, the Dakota Formation, has Cenomanian palynomorphs in the middle nonmarine member and late Cenomanian molluscs in the overlying marine member. The Tropic Shale has been dated by marine molluscs as latest Cenomanian to middle Turonian. The Straight Cliffs Formation spans the middle Turonian through the Santonian and has been divided into four members. The Tibbet Canyon Member is of middle Turonian age, based on inoceramid bivalves, and the overlying terrestrial Smoky Hollow Member, though undated, is probably late Turonian in age. An unconformity of latest Turonian age separates the top of the Smoky Hollow Member from the overlying member. Molluscs in the marine facies of the John Henry Member indicate an early Coniacian through Santonian age. The overlying Drip Tank Member is undated. The Straight Cliffs Formation thickens northward across the Kaiparowits basin, indicating greater rates of subsidence in that direction. The overlying Wahweap Formation is considered to be of early Campanian age on the basis of its mammalian fauna. It is divided here into four informal members. The Kaiparowits Formation is middle to late Campanian in age, based on mammalian faunas and reevaluation of previously reported palynofloras. The Canaan Peak Formation has been dated as late Campanian based on palynomorphs, and if this date is valid, the folding and erosion of the underlying sequence occurred very rapidly near the end of the Campanian.

Abstract The Paradox region, within the Colorado Plateau physiographic province, contains such major features as the San Juan, Blanding, Henry Mountain, and Kaiparowits intermontane basins, the San Rafael swell, and the Monument and Circle Cliffs uplifts. Permian carbonate rocks and sandstone have the greatest potential for future production. The Pennsylvanian section, now the most productive part of the Paleozoic sequence, is second in potential, followed in order of decreasing potential by the Mississippian, Devonian, and Cambrian sections. Ordovician and Silurian rocks are absent in the area. Permian, Pennsylvanian, Mississippian, and Devonian shelf-carbonate rocks in the area between the Cordi- lleran geosyncline and the Uncompahgre uplift show much promise for future prolific production from strati- graphic and structural traps. These carbonate rocks probably will be more productive in the western Paradox region than elsewhere in the area. Large accumulations of oil may be found in Mississippian and Devonian carbonate rocks on structures in the Paradox fold and fault belt. Many stratigraphic traps and some structural traps are expected to be present in sequences of very porous and permeable Permian sandstone in southeastern Utah and in northwestern New Mexico. Mesozoic and Tertiary sequences within the area are predominantly sandstone, siltstone, and shale; they show limited potential for future exploratory success. Cretaceous rocks have been eroded or are near the surface in most localities. Where the Cretaceous is buried in the San Juan basin, it has been drilled extensively to develop the prolific San Juan basin oil and gas fields. Jurassic and Triassic sequences have been explored extensively in the Blanding basin without success. These sequences generally are buried in the San Juan, Henry Mountain, and Kaiparowits basins but may lack associated source rocks, Mesozoic and Tertiary strata are potentially productive in the virtually unexplored Rio Grande trough and San Luis Valley. Obstacles to finding new production are: (1) the relatively high costs of exploration in large parts of the region; (2) the poor surface accessibility in some areas, which limits the acquisition of sufficient seismic control to map the subsurface structure; (3) the inability to acquire acreage and explore in areas where shallow production already is established; and (4) the prohibition of exploration in national parks and monuments.

Abstract The Kaiparowits Basin, located mostly within Grand Staircase–Escalante National Monument, preserves an outstanding record of Late Cretaceous sedimentation in a foreland basin setting. Hosted in these rocks is one of the most continuous and complete records of this period’s ecosystems known from any one geographic area in the world. Recent work in the basin has emphasized macrovertebrate remains and documented many new sites of high scientific value. Recent stratigraphic studies have further refined our knowledge of the depositional systems and chronostratigraphic relationships. Provided is an overview of some of these recent advances, along with the necessary background to provide context .