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Experimental Studies of Supercritical Bedforms Applied to Coarse-Grained Turbidite Deposits of the Tabernas intermontane Basin (SE Spain, Late Miocene)


Modern submarine canyon floors are in many cases covered with bedform patterns linked to supercritical turbidity currents. However, outcrop recognition of sedimentary structures associated with such bedforms has been rare. Here a conceptual model of facies characteristics for supercritical turbidity current is presented to facilitate outcrop recognition of these bedforms. On the basis of experimental work on sedimentary structures produced by supercritical free-surface flows and on the vertical flow structures of high-density turbidity currents, a 3-dimensional bedform stability diagram for turbidity currents and a related sedimentary facies diagram was constructed. To allow scaling of this diagram to natural flows, four non-dimensional parameters were used: 1) densimetric Froude number, 2) grain-roughness related mobility parameter, 3) dimensionless grain size and 4) sediment concentration in the basal layer. Combinations of bedforms and basal layer sediment concentrations were linked to a characteristic facies. Numerical and theoretical models from the literature and from observations of modern turbidite systems were used to estimate characteristic dimensions of the bedforms formed below turbidity currents of various concentration and grain size. The model was applied to a sequence of four outcrops spanning the transition from canyon to fan of the turbidite fan systems in the Tabernas Basin (SE Spain, late Miocene). An idealized vertical succession was deduced from the model and is discussed in the context of classical models of high-density turbidity current deposits.