Using provenance of terrigenous sediment to reconstruct the Agulhas leakage during the early and late Pleistocene

Author(s): Pearson, Bevan D.; Franzese, Allison M.
Author Affiliation(s): Primary:
University of Pennsylvania, Philadelphia, PA, United States
Hostos Community College, United States
Volume Title: Geological Society of America, 2017 annual meeting & exposition
Source: Abstracts with Programs - Geological Society of America, 49(6); Geological Society of America, 2017 annual meeting & exposition, Seattle, WA, Oct. 22-25, 2017. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0016-7592 CODEN: GAAPBC
Note: In English
Summary: The Agulhas Current, the strongest western boundary current in the southern hemisphere, is uniquely characterized by its strong retroflection. The current carries water southward from the Indian Ocean toward the cape of South Africa, before turning back on itself. At this point of retroflection, some of the current's flow escapes into the southern Atlantic Ocean. This transfer of water from the Indian Ocean to Atlantic Ocean makes up the Agulhas Leakage. The Leakage occurs in a series of eddies and rings located in the Cape Basin south of the African continent. Scientific literature demonstrates that relatively buoyant leakage water has been a determining factor varying strength of the Atlantic Meridional Ocean Current (AMOC), during glacial-interglacial cycles. It has been demonstrated that radiogenic isotope, major, and trace element concentrations serve as a proxy for terrigenous sediment provenance in the Agulhas region. Current understanding is that terrigenous sediment provenance is older during warmer periods of deposition. This corresponds to more input from southeastern African end members, and thus a stronger Agulhas Current, during warming periods in the paleoclimate record. Conversely, younger terrigenous sediment deposited during colder periods, such as the Last Glacial Maximum, suggests a weaker Agulhas Current, and less Agulhas Leakage. In 2016, on the International Ocean Discovery Program Expedition 361, sediment cores were drilled at 6 sites in the Greater Agulhas region. A major goal of the expedition was to expand knowledge of the relation between changes in the Agulhas System and changes in paleoclimate, southern African climate, and AMOC. We analyzed sediment from Expedition 361 Site U1479 (35°03.53'S; 17°24.06'E; 2615 mbsl) located where the Agulhas Leakage occurs. We measured Argon, strontium isotope ratios, εNd, trace and major element concentrations on the <2 micron clay fraction. Preliminary results foretell promising findings. For instance, for the Early Pleistocene (≈1.3 - 1.5 Ma), K-Ar model ages correlate with shipboard measurements of natural gamma radiation, which show approximate 41 kyr periodicity.
Year of Publication: 2017
Research Program: IODP Integrated Ocean Drilling Program
IODP2 International Ocean Discovery Program
Key Words: 02 Geochemistry; 03 Geochronology; 24 Surficial Geology, Quaternary Geology; Absolute age; Agulhas Current; Alkaline earth metals; Argon; Atlantic Ocean; Cape Basin; Cenozoic; Expedition 361; IODP Site U1479; International Ocean Discovery Program; Isotope ratios; Isotopes; K/Ar; Marine environment; Marine sediments; Metals; Neodymium; Noble gases; Paleo-oceanography; Paleoenvironment; Pleistocene; Provenance; Quaternary; Rare earths; Sediments; South Atlantic; Southeast Atlantic; Sr-87/Sr-86; Stable isotopes; Strontium
Coordinates: S350332 S350331 E0172405 E0172403
Record ID: 2018062293
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States