New Perspectives on Sediment Routing in Arid Mixed Systems, Examples from the Northern Red Sea

Interactions between the Red Sea’s extensive fringing reef and upland wadi systems represent Earth’s best example of mixed sedimentation in an active rift basin. Absent vegetation or turbidity, the region is ideal for land-marine remote sensing applications. This study uses topographic, bathymetric, and field datasets from the northern Red Sea to assess feedbacks between desert surface processes, coastal carbonate ecology, and climate/sea-level cycles that facilitate sediment transfer, mixing/partitioning, and deposition in a steep arid rift setting. Broadest areas of carbonate sedimentation occur on subaqueous portions of fan deltas near outlets of the largest wadis. Reef growth influences siliciclastic sediment transfer to the basin by 1) increasing confinement and effective depth of canyon heads or 2) by plugging canyon heads associated with inactive wadi systems creating barriers that reroute siliciclastics into littoral cells or trap it in backreef lagoons. Relatively broad shelf areas choke sediment transfer compared to narrow shelf areas where knickpoints migrate into wadi channels and source direct-fed slope systems comprising canyons, ridges, and submarine fans. Where wadis become distributary before reaching the coast they source line-fed slope systems with abundant slump and slide features. These feedbacks between carbonate and siliciclastic depositional processes challenge paradigms supporting a universally suppressive impact of siliciclastic influx on carbonate deposition and instead suggests, at the basin scale, influx of intermittent high siliciclastic loads may be critical for carbonate shelf expansion in steep, deep settings. This study also highlights overlooked influence carbonate frame builders have on siliciclastic routing in mixed settings.