Using Mixed-clay Sediment Gravity Flow Rheology as an Indicator for Flow Velocity and Runout Distance
2026
Baker, Megan L | Baas, Jaco H | Malarkey, Jonathan | Silva Jacinto, Ricardo
It is important to determine whether the dynamics of mixed-clay sediment gravity flows (SGFs) can be predicted from their dominant clay type, because natural SGF deposits can contain mixtures of clay minerals of different cohesive strength, and latitudinal zonation in clay mineral production may influence depositional patterns in mud-rich submarine fans. The present lock-exchange experiments produced high-density SGFs carrying different proportions of strongly cohesive bentonite clay and weakly cohesive kaolinite clay with a fixed 20% volumetric concentration. Head velocity and runout distance of the flows decreased, and starting suspension yield stress increased, as the bentonite fraction increased beyond 20%. However, for bentonite fractions ≤20%, the initial suspensions had lower yield stresses and the flows were more mobile than the pure kaolinite flow, implying that small bentonite fractions reduce the cohesive strength of the suspensions. Predictive equations for the yield stress, head velocity, and runout distance of mixed-clay flows, based on yield stresses of pure-clay constituents, indicate minimal interaction between the constituents for bentonite fractions ≤20%. However, for bentonite fractions >20%, the equations demonstrate an increasingly nonlinear interaction. These results suggest natural SGF dynamics and deposits may be sensitive to the most cohesive clay rather than the dominant clay.
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