Early rifting of Gondwana: Conclusions from the crustal structure of the Falkland Plateau

• Main Author: Schimschal, Claudia
• Format: Thesis
• Language: unknown
• Published: 2018
• Subjects: Antarctic; New Zealand; Maurice; Ewing; Falkland Plateau; Georgia Basin; Maurice Ewing Bank; Antarc*; Antarctica; South Atlantic Ocean
• Online Access: https://epic.awi.de/id/eprint/51598/; https://epic.awi.de/id/eprint/51598/1/Schimschal-2018-diss-FalklandPlateauCrust.pdf; https://hdl.handle.net/10013/epic.b835ebfd-4d02-4c0a-a6ff-5739b819f23d

The reconstruction of continents has been a research field for more than 100 years, since Alfred Wegener proposed his theory of continental drift in 1915. The changing configuration of landmasses and oceans influences the evolution of climate and biosphere and is therefore of great scientific importance. In the southern hemisphere, Gondwana, which comprised the present-day continents of Antarctica, South America, Africa and Australia and smaller landmasses like India, New Zealand, Madagascar and the Arabian Peninsula, was the last supercontinent. In the centre of the continent, the Falkland Plateau was located between the South American, African and Antarctic plates. Today, the Falkland Plateau is a remarkable bathymetric feature in the South Atlantic Ocean offshore southern South America. It stretches for 1500km eastwards from the Falkland Islands into the Georgia Basin, at depths of between one and three kilometres shallower than its surroundings. The central part of the plateau hosts the Falkland Plateau Basin. A bathymetric high, Maurice Ewing Bank (MEB), is located at the eastern termination of the plateau. Although the Falkland Plateau is a key element in Gondwana reconstructions, its crustal structure has long remained speculative. Outcrops on the Falkland Islands prove the presence of Precambrian continental crust at the western end of the plateau. At the eastern end, gneisses recovered at DSDP drill site 330 on MEB, were interpreted to show its continental composition. For the crust underneath the Falkland Plateau Basin, a variety of approaches have led to conflicting conclusions on the presence of continental or oceanic crust. The lack of certainty regarding the crustal composition here has both stimulated and permitted a range of contrasting Gondwana reconstructions. To close this gap, the expedition ANT-XXIX/5 with the research vessel RV Polarstern was conducted in 2013. Wide-angle seismic data were acquired using land stations onshore East Falkland and ocean bottom stations along the 1450 km long ...