The Indian-Atlantic Ocean gateway during the Pliocene: current dynamics and changing sediment provenance

• Main Authors: Gruetzner, Jens, Uenzelmann-Neben, Gabriele
• Format: Conference Object
• Language: unknown
• Published: 2017
• Subjects: NADW
• Online Access: https://epic.awi.de/id/eprint/44305/; https://epic.awi.de/id/eprint/44305/1/Gruetzner_DFG-IODP-Kolloq_2017.pdf; https://hdl.handle.net/10013/epic.50653; https://hdl.handle.net/10013/epic.50653.d001

The Pliocene epoch represents a discrete interval which reversed a long-term trend of late Neogene cooling and is also the most recent geological interval in which global temperatures were several degrees warmer than today. It is therefore often considered as the best analogue for a future anthropogenic greenhouse world. However, there is growing evidence that the Pliocene was not a stable period but can rather be subdivided in several distinct climate phases. Our understanding of Pliocene climate variability in the Southern Hemisphere, and especially in the Atlantic-Indian ocean gateway, is limited by scarce marine records and poor age control on existing terrestrial climate archives. At five from six drilling locations of IODP Exp. 361 (Jan. – March 2016) high resolution complete Plio-/Pleistocene sections have been recovered (see IODP Expedition 361 – Southern African Climates and Agulhas LGM Density Profile by Gruetzner et al., this Volume). Our new research proposal focuses on three of these sites forming a latitudinal transect in the Atlantic-/Indian Ocean gateway and combines chemical, physical property and seismic methods. Primary site for our investigations is Site U1475 with the focus on the interplay between northern and southern sourced deep water masses at the Agulhas Plateau. This will be augmented by investigations at Sites U1479 (Cape Basin) and U1474 (Natal Valley), both located in the pathway of modern NADW. Our research is driven by three main working hypotheses: Seismic stratigraphies for the last 6 Ma and sediment drift growth in the Atlantic-Indian gateway are mainly controlled by bottom water flow changes Using the new sediment archives and physical property records from IODP Exp. 361 (Hall et al., 2016) we aim to construct detailed seismic stratigraphies for the Agulhas Plateau, the Natal valley and the Cape basin for the last 6 Ma. At all Exp. 361 sites P-wave velocity and density records are of sufficient quality to enable detailed correlations of drilling results and site survey data ...