Tectonic Control on the Sequence Stratigraphy of Nonmarine Retroarc Foreland Basin Fills: Insights from the Upper Jurassic of Central Utah, U.S.A.

摘要

Continental successions of the North American Western Interior retroarc foreland basin provide an excellent opportunity to evaluate the tectonic controls on nonmarine sequence stratigraphy. The transition between the Upper Jurassic Brushy Basin Member anastomosed fluvial system of the Morrison Formation and the gravelly braided-river deposits of the Buckhorn Conglomerate has been studied to assess the dispersal of coarse clastics and the development of associated basin-wide unconformities in a sequence stratigraphic framework. The sharp contact between the two members is interpreted to be conformable based on stratigraphic, sedimentologic, and petrologic data collected at and near Cedar Mountain in central Utah, while a regional, mature paleosol at the top of the Buckhorn Conglomerate indicates the presence of a major sequence boundary. These interpretations are combined with paleoflow data and fluvial architectural analysis to reconstruct the evolution of the alluvial equilibrium profiles that controlled deposition of the succession.