Tectonic Reconstructions of the Southernmost Andes and the Scotia Sea During the Opening of the Drake Passage

Study of the tectonic development of the Scotia Sea region started with basic lithological and structural studies of outcrop geology in Tierra del Fuego and the Antarctic Peninsula. To nineteenth- and early twentieth-century geologists, the results of these studies suggested the presence of a submerged orocline running around the margins of the Scotia Sea. Subsequent increases in detailed knowledge about the fragmentary outcrop geology from islands distributed around the margins of the Scotia Sea, and later their interpretation in the light of the plate tectonic paradigm led to large modifications in the hypothesis such that by the present day the concept of oroclinal bending in the region persists only in vestigial form. Of the early comparative lithostratigraphic work in the region, only the likenesses between Jurassic–Cretaceous basin floor and fill sequences in South Georgia and Tierra del Fuego are regarded as strong enough to be useful in plate kinematic reconstruction by permitting the interpretation of those regions’ contiguity in mid-Mesozoic times. Marine and satellite geophysical data sets reveal features of the remaining, submerged, 98 % of the Scotia Sea region between the outcrops. These data enable a more detailed and quantitative approach to the region’s plate kinematics. In contrast to long-used interpretations of the outcrop geology, these data do not prescribe the proximity of South Georgia to Tierra del Fuego in any past period. It is, however, possible to reinterpret the geology of those two regions in terms of the plate kinematic history that the seafloor has preserved

Bottom-current control on sedimentation in the western Bellingshausen Sea, West Antarctica

A set of single channel and multi channel seismic reflection profiles provide insights in the young Cenozoic sedimentation history on the continental rise of the western Bellingshausen Sea west and north of Peter I Island. This area was mainly influenced by the glacial controlled sediment supply from the continental shelf and by bottom current activity. The seismic data show northwards structural altering of a prominent sediment mound from a sediment drift structure into a oppositional orientated large channel-levee complex lying west of an erosional channel. This change indicates a northward decreasing influence of a westward flowing bottom contour current. The topography suggests Peter I Island to be the main feature for the change of the bottom current influence, acting as a barrier for the bottom current and the entrained sediment material. West of Peter I Island the eastward orientated Coriolis force remains as the affecting force which deflects suspended load of the turbidites to the west and leads to a stronger grow of the western channel-levee. Calculated sediment deposition rates based on the seismic data reveal the sediment mound as a remarkable and important sediment depocentre for young Cenozoic glacial transported and contouritic sediment material in the Bellingshausen Sea