2019 CSDMS meeting-068

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Investigating Mechanisms of the Cretaceous Western Interior Seaway and its Impacts on Surface Processes using Landscape Evolution Simulations

Ching Chang, University of Illinois at Urbana-Champaign Urbana Illinois, United States. cchang57@illinois.edu

Lijun Liu, University of Illinois at Urbana-Champaign Urbana Illinois, United States. ljliu@illinois.edu

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 is designed to reflect a certain physical mechanism. In this research, we aim to use forward landscape evolution models to investigate the mechanisms accounting for the characteristics in the observed WIS stratigraphy. In our data-oriented landscape evolution models, where we test different scenarios of lithospheric and mantle forcing, the results suggest that only a geographically migratory subsidence can produce 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. Furthermore, this migratory subsidence of mantle origin can also explain the continental drainage reorganization over middle North America after the WIS and the eastward-shifting sediment flux to the Gulf of Mexico during the Cenozoic.