Unveiling the contourite depositional system in the Vema Fracture Zone (Central Atlantic).

A combination of a high sediment input and intense bottom currents often leads to the formation of contourites (sediments deposited or significantly reworked by bottom currents). Both of these components are present in the Vema Fracture Zone valley which is the most important passageway for the distribution of the Antarctic Bottom Water from the West to the North-East of the Atlantic. However, no contourite drifts, moats or contourite channels have been found in this region in more than half a century of research. The prevailing sedimentation paradigm postulates that turbidity currents have predominantly governed sedimentation in this region during the Pleistocene. This work describes the first example of contourite depositional system identified in the Vema Fracture Zone. The discovery was made through detailed high-resolution sub-bottom profiling, as well as numerical modeling and direct measurements of bottom current velocities. Such systems are exceptionally uncommon in fracture zones. This study highlights the importance of further research of contourites along the Vema Fracture Zone based on modern concepts of contourite and mixed depositional systems. The work also emphasizes the need to reevaluate the impact of bottom currents on sedimentation in this region, and particularly in the narrow segments of the fracture zone valley.

CTD data over a repeated section in the Vema Channel.

We present a CTD dataset of repeated sections across the Vema Channel in the South Atlantic approximately along 31°12' S between longitudes 39°18.0 W and 39°30.0' W. The Vema Channel is a narrow conduit for Antarctic Bottom Water across the Rio Grande Rise. The measurements at CTD stations (Conductivity-Temperature-Depth) across the Vema Channel were started by German scientists in 1991. In 2002, Russian scientists took part in this work and have been establishing stations across this standard section until recently. The data were collected using the Sea-Bird Electronics SBE-19 profiler. The data are presented in tabular format. The data are available at http://dx.doi.org/10.17632/hh4hhn6ny8.1.