Distinct Responses of Intraplate Sedimentation to Different Subsidence Mechanisms: Insights From Forward Landscape Evolution Simulations

Both the surface processes associated with large intracontinental basins and their underlying geodynamic mechanisms remain unclear. Proposed models include flexural deformation due to orogenic loading, isostatic subsidence in response to lithosphere extension, and dynamic subsidence arising from sublithospheric mantle downwelling. Here we use forward landscape evolution modeling to quantitatively investigate the surface process response to various types of tectonic subsidence during intraplate sedimentation. We find that isostatic subsidence causes continuous accumulation of sediment through time with a largely stable pattern of fluvial drainage. In contrast, dynamic subsidence results in fast intraplate sedimentation followed by regional unconformities and continental-scale reorganization of fluvial networks. Our quantitative simulations reveal that the traditional 1-D isostatic backstripping approach may lead to erroneous estimates of the past tectonic subsidence from the preserved sedimentary records: for lithospheric elastic thickness (T_e) < 50 km, the flexural effect leads to larger (smaller) apparent subsidence at the center (rim) of the basin, compared to the true subsidence; for T_e > 50 km, broadscale flexural support leads to underestimated subsidence throughout the basin. Subparallel tilted strata are a unique stratigraphic feature associated with spatially migratory dynamic subsidence followed by dynamic rebound. Their characteristic slope provides a quantitative constraint on the spatiotemporal pattern of dynamic subsidence. The Cretaceous Western Interior Seaway provides an example of this type of basin fill. We demonstrate that quantitative, forward landscape evolution modeling can help decipher the relationship between intraplate sedimentation and the underlying tectonic drivers.