Invited Talk – A Multi-Proxy Approach to Understanding Continental-scale Landscape Evolution: A North American Example
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The generation and evolution of continental topography are fundamental geologic and geomorphic concerns. In particular, the history of landscape development might contain useful information about the spatio-temporal evolution of deep Earth processes, such as mantle convection. A significant challenge is to generate observations and theoretical predictions of sufficient fidelity that would enable landscape evolution to be constrained at scales of interest. Here, we present a multi-proxy approach to determine how the North American landscape evolved. First, stratigraphic markers are used to estimate post-depositional regional uplift. Present-day elevations of these deposits demonstrate that > 2 km of long wavelength uplift centered on the Colorado-Rocky-Mountain plateaux occurred in Cenozoic times. Secondly, to bridge the gaps between measurements, an inverse modeling scheme is used to calculate the smoothest spatio-temporal pattern of uplift rate that yields the smallest misfit between 4161 observed and calculated longitudinal river profiles. Our results suggest that Cenozoic regional uplift occurred in a series of stages, in agreement with independent stratigraphic observations. Finally, a landscape evolution model driven by this calculated uplift history is used to determine drainage patterns, denudation and sedimentary flux from Late Cretaceous times until the present day. These patterns are broadly consistent with stratigraphic and thermochronologic observations. We conclude that a calibrated inverse modeling strategy can be used to extract the temporal and spatial evolution of the North American landscape at geodynamically useful scales, where Cenozoic sub-plate support has played a defining role in generating topography, especially at wavelengths greater than a few tens of kilometers.