Channel-levee evolution in combined contour current-turbidity current flows from flume tank experiments

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.