Terrigenous provenance follows climate variability at IODP Site U1474, southwestern Indian Ocean

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Author(s): Babin, Daniel P.; Hemming, S. R.; Simon, M.; Hall, I. R.; Franzese, A. M.; Goldstein, S. L.; Cai, Y.; Liu, T.; Johns, Matthew A.; Tejada, Luis; LeVay, L.
Author Affiliation(s): Primary:
Columbia University in the City of New York, Department of Earth and Environmental Sciences, New York, NY, United States
Cardiff University, School of Earth and Ocean Sciences, Cardiff, United Kingdom
CUNY Hostos Community College, Natural Sciences, Bronx, NY, United States
Lamont-Doherty Earth Observatory, Palisades, NY, United States
Texas A & M University, College Station, TX, United States
Volume Title: AGU 2017 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2017; American Geophysical Union 2017 fall meeting, New Orleans, LA, Dec. 11-15, 2017. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: International Ocean Discovery Program (IODP) Expedition 361 "South African Climates" sought records to document the role of the greater Agulhas Current system in global climate variability and southeast African hydroclimate over the past 5 Ma. IODP Site U1474 is located at the headwaters of the fully constituted Agulhas Current. Being close to the southeast African margin, the core location is ideally situated to track variations of terrigenous sediment delivery to the site, which may relate to climatic changes in southern Africa that follow variability in the Agulhas Current heat content. To analyze climate variability, we consider an XRF record for the site in combination with major and trace element chemistry and K-Ar ages from the clay fraction (<2um) plus bulk major element chemistry of 60 shipboard moisture and density samples spanning 4.8 Ma. These data are interpreted with a sea surface temperature (SST) record from Mg/Ca measurements spaced at ≈40 kyr on the surface dwelling (mixed layer) planktonic foraminifera Globigerinoides ruber. Both long-term trend and precessionally-paced changes in the terrigenous composition are evident. Fe/K ratios from XRF core scanning data are consistent with those previously reported (Simon et al. 2015 Sci. Reports) in a nearby core that spans the last 270 ka. Terrigenous mass accumulation rates are relatively constant at ≈3 g/cm3/ky from 5-2.5 Ma, then gradually decrease to ≈2 g/cm3/ky at the top. This declining flux is accompanied by older and more weathered and mafic sources, possibly a result of reduced precipitation in proximal catchments. It is suggested that the relationships between these proxies is explained by a greater relative contribution of sediment supplied from the Limpopo catchment compared to nearby drainage basins such as the Tugela. The SST record shows a cooling trend from the ≈27 °C average between 4.5-2.5 Ma to ≈25 °C at 1.0 Ma, followed by high amplitude changes (6 °C changes instead of 3° C) in SST in the 0-1.0 Ma interval, with minimum SST estimates of ≈21 °C. These changes are consistent with, but could lag behind models predicting aridification in Africa associated with a drop in Indian Ocean temperatures around 3-4 Ma, caused by tectonic changes in the Indonesian Throughflow that shifted its Pacific source waters further north (Cane & Molnar 2001 Science).
Year of Publication: 2017
Research Program: IODP Integrated Ocean Drilling Program
IODP2 International Ocean Discovery Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Agulhas Bank; Cenozoic; Climate change; Expedition 361; IODP Site U1474; Indian Ocean; International Ocean Discovery Program; Neogene; Paleo-oceanography; Paleoclimatology; Pliocene; Quaternary; Tertiary
Record ID: 2018093812
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data supplied by, and/or abstract, Copyright, American Geophysical Union, Washington, DC, United States

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