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

Abstract

The North Scotia Ridge is the offshore morphostructural expression of the left-lateral transcurrent South America-Scotia Plate Boundary. Several blocks compose the ridge, including the scarcely studied Namuncurá Bank (NB, also known as Burdwood). We present the first detailed study of active structures on the seafloor of the western NB from a database of 3D and 2D seismic data, multibeam bathymetry, and sub-bottom profiles. This work assesses the architecture, style of deformation and Cenozoic evolution of NB, where several groups of faults, and en echelon folding, affects the seabed and shallow sub-bottom. These features compound the northernmost structures associated with a releasing bend, fitting well with a left-lateral Riedel shear model oriented at N74°E, slightly rotated with respect to the present-day plate boundary stress regime. The current tectonic scenario started with a main deformational phase in the Neogene, partially distributed by the Malvinas Fold-Thrust Belt, while modern deformation continues to be conditioned by pre-existing structures. This study allows for a better understanding of the tectonics of the North Scotia Ridge, a morphostructure that influences the circulation of the Antarctic Circumpolar Current thus impacting the global climate.