Elda Miramontes | Along-slope and across-slope channels formed or affected by bottom currents скачать в хорошем качестве

Elda Miramontes | Along-slope and across-slope channels formed or affected by bottom currents

Bouma Virtual Sampler Conference 20-22 April 2022 Day 3 - Bottom Current and their Deposits Elda Miramontes | Along-slope and across-slope channels formed or affected by bottom currents Ocean currents flowing near the seafloor (i.e. bottom currents) can profoundly reshape the seafloor and even modify the characteristics of turbidite systems. The interaction of bottom currents with the seafloor can generate erosion or avoid deposition resulting in the formation of channels, which can have different orientations and morphologies depending on their driving processes. Bottom currents flowing alongslope and related to the thermohaline circulation (i.e. contour currents) often form moats or contourite channels at the foot of slopes and are typically associated with a zone of sediment accumulation named contourite drift. Contour currents can also generate channels parallel to the bathymetric contours in open slopes, without an associated drift, when depressions such as pockmarks are present at the seafloor. The interaction of bottom currents with pockmarks induces a significant erosion at their streamwise edges. When pockmarks are distributed aligned in pockmark trains, they can be eroded and elongated in the streamwise direction, finally coalesce and form a channel. Other oceanographic processes can also contribute to the formation of rectilinear channels in open slopes oriented parallel to the contours. This type of channels has been so far mainly identified on upper continental slopes (e.g. in the Mozambican and Namibian margins) and seems to be related to internal waves. The interaction of bottom-current related processes and downslope gravity driven processes and products forms mixed turbidite-contourite systems. The synchronous interaction of contour currents and turbidity currents generates asymmetric channel-levee systems that are oriented across-slope and commonly migrate in the opposite direction of contour currents. Bottom currents can also interact with deposits previously formed by turbidity currents and modify their morphology and sediment facies. For instance, bottom currents flowing along across-slope submarine channels can erode their flanks and induce the deposition of contouritic sand. The role of bottom currents in the inception and modification of channels has widely been recognised based on geophysical and sedimentological observations. However, the oceanographic and sedimentary processes that control the development of such channels are still poorly understood due to the scarcity of in situ observations of the flows, as well as, physical and numerical simulations. Learn more: https://sepm.org/bouma-conference