Presenters-0652
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CSDMS 2024: Coastlines, Critical Zones and Cascading Hazards: Modeling Dynamic Interfaces from Deep Time to Human Time
Designing and applying a landscape evolution model infused with cosmogenic nuclides for geomorphic insights
Abstract
Terrestrial cosmogenic nuclides (TCN) are commonly used to assess denudation rates in soil-mantled uplands. The estimation of an inferred denudation rate (Dinf) from TCN concentrations typically relies on the assumptions of steady denudation rates during TCN accumulation and negligible impact from soil chemical erosion on soil mineral abundances. However, in many landscapes, denudation rates are not steady, and the composition of soil is markedly affected by chemical erosion, adding complexity to the analysis of TCN concentrations. We introduce a landscape evolution model that computes transient changes in topography, soil thickness, soil mineralogy, and soil TCN concentrations. With this model, we explored TCN responses in transient landscapes by imposing idealized perturbations in tectonically (bedrock uplift rate) and climatically sensitive parameters (soil production efficiency, hillslope transport efficiency, and mineral dissolution rate) on synthetic, steady-state landscapes. The experiments on synthetic landscapes delivered important insights about TCN responses in transient landscapes. Results showed that responses of Dinf to tectonic perturbations differ from those to climatic perturbations, indicating that spatial and temporal trends in Dinf serve as indicators of perturbation type and magnitude. Also, if soil chemical erosion is accounted for, basin-averaged Dinf inferred from TCN in stream sediment closely tracks actual basin-averaged denudation rate, showing that Dinf is a reliable representation of actual denudation rate, even in many transient landscapes. In addition, we demonstrate how this model can be applied to a real landscape in the Oregon Coast Range and how model predictions can be compared to field measurements of cosmogenic nuclides and chemical depletion in sediments. Overall, landscape evolution models infused with cosmogenic nuclides can be used to scrutinize methodological assumptions, reveal potential real-world patterns in transient landscapes, and deepen the comprehension of field data.
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