Plate tectonic development of the Scotia Sea

• Main Author: Eagles, Graeme
• Format: Conference Object
• Language: unknown
• Published: 2013
• Subjects: Antarc*; Antarctic; Antarctica; Graham Land; Scotia Sea; Tierra del Fuego
• Online Access: https://epic.awi.de/id/eprint/33233/; https://hdl.handle.net/10013/epic.41722

The Scotia Sea opened to fill the widening space created between the dominantly-westward motion of the South American plate and the dominantly-eastward motion of the South Sandwich Trench and its ancestors, as seen from Antarctica. Presently this space opens along an east-west azimuth, and is partitioned into complex transform motions on two large fault zones at the southern and northern edges of the Scotia Sea, and post-17 Ma seafloor spreading in the East Scotia Sea back-arc basin just west of the trench. A patchwork of basins and extended microcontinents within the floor and margins of the Scotia Sea show that, in the past, other divergent plate motions saw to the growth of much of the area west of the back-arc basin by seafloor spreading and continental extension. Two different assumptions about the tectonic history of the Scotia Sea steer interpretations of these basins and microcontinents. The first is predicated on a 19th Century view of the regional geology in which ‘the Andes are to be seen again in Graham Land’; that is, on the assumption that the Scotia Sea grew by the disruption of a compact segment of an initially-continuous convergent Antarctic-South American continental margin. The second assumes that the Scotia Sea grew within the space generated by the relative motions of the major plates behind the active continental margin. The oldest remnants of the Scotia Sea’s growth are Jurassic and Cretaceous rocks of Tierra del Fuego and South Georgia. These rocks can be interpreted in terms of the growth of a back-arc basin, the Rocas Verdes basin, at the active continental margin of Gondwana. They are alternatively interpretable as records of basins that formed during NE-directed South American–Antarctic relative plate motions in the supercontinent interior. In Tierra del Fuego, remnants of small extensional basins with Paleogene sedimentary fills record the onset of WNW-directed motion of the South American plate at ~50 Ma. Ongoing plate motion in this sense culminated in the development of a large ...