CONTROLS ON SEDIMENT DISPERSAL AND EXTRINSIC SIGNAL TRANSFER FROM SOURCE-TO-SINK: NEOGENE-QUATERNARY ORANGE BASIN, SOUTHERN AFRICA

Sediment production and transport within a drainage basin influence the rate and total volume of sediment delivered to the coast. The rate of sediment delivery has implications for local ecology, land use, and natural resources. Sediment supply is controlled by multiple factors (e.g., drainage basin size, geology, relief and climate) that are nonlinearly dependent on one another, which makes assessments of their relative importance challenging. Physics-based, source-to-sink numerical modeling allows for quantitative analysis of controlling factors across the entire sediment-routing system and time period of interest. We use Dionisos, a nonlinear diffusion-based landscape evolution model, to investigate the roles of climate and tectonism on the generation of sediment from southern Africa during the Late Miocene to Present. We construct a sediment budget that accounts for high-resolution (100 kyr) variability in sedimentation rates and locations of deposition. During this time period, southern Africa experienced uplift in concert with a drying climate. Gross sediment delivery to the margin primarily reflects sensitivity to precipitation, with a secondary control of tectonically influenced (dynamic topography) drainage patterns. Overall, the model results fall within the range of sedimentation rates calculated from interpretation of seismic-reflection data by previous studies as well as accurately predict the locations of the primary depocenters along the West African continental margin. Model results provide a quantitative framework for evaluating the importance of controlling factors in sediment dispersal and continental-margin stratigraphic evolution.