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The AAPG/Datapages Combined Publications Database

Journal of Sedimentary Research (SEPM)

Abstract


Journal of Sedimentary Petrology
Vol. 41 (1971)No. 1. (March), Pages 97-113

Mixing at Turbidity Current Heads, and Its Geological Implications

J. R. L. Allen

ABSTRACT

The shape of the Previous HitheadNext Hit of a turbidity current is consistent with an inflow of the ambient medium into the current along clefts and tunnels regularly spaced along and back from the overhanging front of the Previous HitheadNext Hit. The rate of inflow of the ambient medium into the Previous HitheadNext Hit is expressed mathematically, and it is shown that the bed shear stresses exerted in the region of the Previous HitheadNext Hit vary transversely across the region with a spatial periodicity. The deducd force structure of the Previous HitheadNext Hit region explains the hitherto puzzling occurrence on turbidite soles of regular bands or clusters of flute marks aligned parallel with flow. It is also shown that the near-bed flow in the Previous HitheadNext Hit is strongly three-dimensional, and this may help to explain the commonly observed non-parallelism of the sole markings observed n single bedding surfaces. The rates of inflow of the ambient medium into the Previous HitheadTop are found to be large enough to account for the density reduction necessary for the transformation of a liquified sediment slump into a turbidity current in a journey down the continental slope and upper rise.


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