Abstract
Abstract Turbidity currents and contour currents are common sedimentary and oceanographic processes in deep-marine settings that affect continental margins worldwide. Their simultaneous interaction can form asymmetric and unidirectionally migrating channels, which can lead to opposite interpretations of paleocontour current direction: channels migrating against the contour current or in the direction of the contour current. In this study, we performed three-dimensional flume-tank experiments of the synchronous interaction between contour currents and turbidity currents to understand the effect of these combined currents on channel architecture and evolution. Our results show that contour currents with a velocity of 10–19 cm s−1 can substantially deflect the direction of turbidity currents with a maximum velocity of 76–96 cm s−1, and modify the channel-levee system architecture. A lateral and nearly stationary front formed on the levee located upstream of the contour current, reduced overspill and thus restrained the development of a levee on this side of the channel. Sediment was preferentially carried out of the channel at the flank located downstream of the contour current. An increase in contour-current velocity resulted in an increase in channel-levee asymmetry, with the development of a wider levee and more abundant bedforms downstream of the contour current. This asymmetric deposition along the channel suggests that the direction of long-term migration of the channel form should go against the direction of the contour current due to levee growth downstream of the contour current, in agreement with one of the previously proposed conceptual models.
Highlights
Turbidity currents are underwater gravitydriven flows that transport large amounts of sediment to the deep sea (Normark, 1970)
Turbidity currents are energetic flows with velocities ranging from few decimeters to a few meters per second (e.g., Azpiroz-Zabala et al, 2017)
We consider the ratio between alongslope contour-current velocity and the maximum downslope velocity of turbidity currents as the best scaling ratio for the relative strength of contour currents and turbidity currents
Summary
Turbidity currents are underwater gravitydriven flows that transport large amounts of sediment to the deep sea (Normark, 1970). The transfer of sediment from the continent to the deep sea through gravity flows has mainly been considered to be a downslope process, many systems show characteristics that suggest that turbidity currents and their related deposits (i.e., turbidites) can be affected by along-slope bottom currents (i.e., contour currents), resulting in the formation of asymmetric channel-levee systems (Fig. 1).
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