Reconstruction of oceanic currents and climate change in the Transkei Basin, South African gateway

• Main Author: Schlüter, Philip
• Other Authors: Miller, Heinrich, Uenzelmann-Neben, Gabriele, Huhn, Katrin
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Universität Bremen 2007
• Subjects: reflection seismics; sediment drifts; bottom currents; 550; 550 Earth sciences and geology; ddc:550; Drake Passage; NADW; North Atlantic Deep Water; North Atlantic
• Online Access: https://media.suub.uni-bremen.de/handle/elib/2422; https://nbn-resolving.org/urn:nbn:de:gbv:46-diss000108446

The region south of South Africa has been a crucial gateway for large scale Thermohaline Circulations since late Eocene times. Here, three of the most important currents for maintaining the global heat exchange, namely the warm and surface related Agulhas Current (AC), and the cold and denser North Atlantic Deep Water (NADW) as well as the Atlantic Bottom Water (AABW), flow around South Africa. Due to the special tectonic and geologic situation, a huge amount of the deep and bottom water masses that flow around South Africa have to pass the narrow Agulhas Passage, located between the South African continental shelf and the submarine Agulhas Plateau. As a result, the sedimentary infill of the Transkei Basin, which is located east of the Agulhas Plateau, has been predominantly influenced by NADW and AABW activity since ~36 Ma. Via the analysis of this sedimentary infill, a palaeo current reconstruction of (proto-) NADW and (proto-) AABW revealed changing flow paths and flow strengths since then. These variations in current attributes were triggered by large scale effects, such as the opening of the Tasman Gateway and the Drake Passage in the Late Eocene, or the closure of the Isthmus of Panama in the Pliocene. A more detailed analysis of the Transkei Basin's depocentre locations and interface outlines resulted in a palaeo flow path reconstruction for this region.Moreover, palaeo climate conditions from the Late Cretaceous were partially reconstructed via the analysis of high amplitude seismic reflections, so called bright spots, from the central Transkei Basin. The evaluation of these bright spots provided indications for anoxic conditions for a period between ~90 Ma and ~80 Ma for the region south of South Africa, which could be related to worldwide Oceanic Anoxic Event 3.