Neotectonics on the Namuncurá (Burdwood) Bank: unveiling seafloor strike-slip processes along the North Scotia Ridge

Abstract

The North Scotia Ridge is the morphostructural expression of the left-lateral transcurrent South American-Scotia Plate Boundary. Several blocks compose the ridge, including the Namuncurá (Burdwood) Bank, which displays a releasing and a restraining bend on its western and eastern sides, respectively. Despite its tectonic relevance, detailed studies of the bank, and especially its western part, are scarce. We present the first detailed study of active structures on the seafloor of the western North Scotia Ridge. From a database of 3D and 2D seismic data, multibeam bathymetry, and sub-bottom profiles, this work evaluates a strike-slip basin, several groups of faults, and an en echelon fold causing deformation in the seabed and shallow sub-bottom. These features compound the northernmost structures associated with the releasing bend of the Namuncurá Bank, fitting well with a left-lateral Riedel shear model oriented at N74°E. The currently active deformation had a main deformational phase in the Neogene and its development was partially controlled by the Malvinas Fold-Thrust Belt. This study allows for a better understanding of the tectonics of the North Scotia Ridge, a morphostructure that influenced the circulation of the Antarctic Circumpolar Current thus impacting on the global climate.