INVESTIGATING THE DRIVING MECHANISMS FOR THE SEDIMENTATION HISTORY OF THE CRETACEOUS WESTERN INTERIOR SEAWAY USING LANDSCAPE EVOLUTION MODELS

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 histories, each of which can reflect a certain physical process. In this research, we aim to use forward landscape evolution models to investigate the mechanisms accounting for the characteristics in the observed WIS stratigraphy. Specifically, we first rely on idealized models to better understand the quantitative relationships between the tectonic forcing and the resulting strata in intra-continental sedimentary basins. Results from these models suggest that only with geographically migratory subsidence can there be tilted strata and migratory depocenter, both of which are characteristic for the WIS stratigraphy. This implies that the tectonic subsidence of the WIS is likely originated from deep mantle downwelling underneath the westward-moving North American plate. This is then confirmed by data-oriented landscape evolution models, where we test lithospheric and mantle forcing from different geodynamic scenarios. Furthermore, we also investigate the effect of orogeny-induced flexural subsidence on the WIS stratigraphy, with the goal of better understanding the temporal history of the Sevier Orogeny and the flexural strength of the underlying lithosphere.