INVESTIGATING MECHANISMS OF THE CRETACEOUS WESTERN INTERIOR SEAWAY AND ITS SEDIMENTATION HISTORY USING LANDSCAPE EVOLUTION SIMULATIONS

The surface geology of Late Cretaceous Western Interior Seaway (WIS) has been extensively studied, and many recent studies suggest the presence of dynamic loading due to flat slab subduction. However, it remains unclear how surface processes respond to tectonic forcing originated from either lithospheric flexural isostasy or sub-lithospheric mantle convection. Landscape evolution models represent an ideal tool to test the surface responses under different tectonic scenarios, each of which is designed to reflect a certain physical mechanism. In this research, we aim to use landscape evolution models to investigate the mechanisms accounting for the characteristics in the observed WIS stratigraphy. The results suggest that only a geographically migratory subsidence based on geodynamic modeling can produce eastward tilted strata and shifting depocenter, both of which are key features in the WIS sedimentary record. This implies that the tectonic subsidence of the WIS likely originated from deep mantle downwelling underneath the westward-moving North American plate. The comparison of sediment isopachs through the Late Cretaceous between the observation and the prediction shows that the predominantly control of the sedimentation pattern switches from flexural subsidence (100-84 Ma) to dynamic subsidence (84-66 Ma). Furthermore, this migratory subsidence of mantle origin can also explain the eastward-shifting sediment flux to the Gulf of Mexico during the Cenozoic.