238-2 Transport Dynamics of Mixed Siliciclastic–Carbonate Turbidity Currents Under Variable Flow Concentrations

Session: Recent Advances and New Voices in Marine and Coastal Geoscience

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Abstract:

Turbidity currents are powerful, sediment-laden flows that shape submarine seascapes and transport sediment, carbon, nutrients, and pollutants into the deep ocean. While siliciclastic systems have been widely studied, the behavior of poorly sorted carbonate turbidity currents remain poorly understood. Our study addresses this gap by investigating flow structure, transport dynamics, and depositional characteristics of mixed-lithology turbidity currents using four flume experiments with natural, irregular-shaped carbonate sediments collected from modern lagoonal sediments in the Red Sea. The sediments consist of approximately 50% carbonate and 50% siliciclastic grains, with a mud content of about 30%. Our experiments demonstrate that increasing sediment concentration promotes flow stratification, characterized by a dense basal layer driven by grain-to-grain interactions and overlying turbulent layers capable of suspending coarse grains. Sediment deposition occurred along the flume floor in all experiments, resulting in mm- to cm-scale ‘beds’ with overall vertical and downslope fining trends that correlate with measured velocity gradients. Higher-concentration flows exhibited higher flow velocities and greater resistance to shear-induced mixing at the upper flow boundary, while lower-concentration flows moved slower and were less stratified. Our results suggest that carbonate-rich turbidity currents can achieve significant run-out distances and efficiently transport coarse sediment into deep basinal settings. These findings imply that carbonate turbidity currents are capable of building significantly-sized submarine fans, with important implications for carbon cycling, geohazard assessment, and subsurface reservoir prediction.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-6770

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