Circulation of hydraulically ponded turbidity currents in
three-dimensional minibasins with implications for turbidite shape
Abstract
Minibasins on continental margins trap turbidity currents transporting
material downslope, but little is known about the inherently
three-dimensional (3-D) mechanics of these confined flows. Utilizing new
methodology, experimental results quantify flow dynamics in minibasins
for the first time. It is shown that dynamics are dominated by 3-D
circulation cell structures, across the fill-to-strip-to-spill
transition that are controlled by flow discharge. Measurements of
velocity throughout circulation cells indicate vorticity dominates
strain rate with fluid rotating into the center of cells where it
upwells: this influences minibasin sediment trapping potential and
deposit heterogeneity. Flow properties link to depositional patterns on
minibasin slopes. Specifically, higher input discharges are correlated
with higher fluxes into the center of minibasins and reduced deposit
tapering on minibasin slopes. This geometry is linked to the amount of
sediment rich flow runup on the distal minibasin wall, where flow and
sediment is delivered to circulation cells.