Landscape Response to Changes in Dynamic Topography on the U.S. Atlantic Passive Margin

Abstract:

Recent global backwards-in time models of mantle convection have resulted in vastly different interpretations of the transient state of dynamic topography on the U.S. Atlantic passive margin over the past 30 Myr (Moucha et al., 2008; Spacejovic et al., 2008; Rowley et al., 2013; Liu, 2014) . A promising way of benchmarking these geodynamic models is by reconciling them with the observed offshore sedimentary record. However, it is difficult to deconvolve the erosional response produced by changes in dynamic topography from other sources of landscape change because the erosional response is a convolution of dynamic topography changes, tectonic uplift/subsidence, flexural response to erosional unloading and depositional loading, rock properties, and climate. Herein, we present results from a new landscape evolution model that is capable of producing simulations that are required at the scale and resolution necessary to quantify the landscape response to various models of dynamic topographic change on the U.S. Atlantic passive margin in the presence of flexural unloading and loading due to erosion and deposition. We perform a sensitivity study on the effects of geodynamic modeling parameters including effective elastic thickness, climate and rock properties. We find that, while models of dynamic topography are difficult to discern from the available sedimentary record at the scale of the continent in part due to induced topologic (stream geometry) change, at the catchment scale deposition rates are vastly different through time with differing dynamic topography models. At this scale, all models show distinct peaks in deposition rates, and varying elastic thickness has a significant effect on altering the timing of peak deposition.