IODP site 1476; 7.5 million year record of southeast African climate

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Author(s): Cantu, Katrina; Norris, Richard D.
Author Affiliation(s): Primary:
University of California at San Diego, La Jolla, CA, United States
Scripps Institution of Oceanography, 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: The primary focus of IODP Expedition 361 was southeast African Climate. Site 1476 in the northern Mozambique Channel yielded a sediment record going back roughly 7.6 million years, a time frame particularly interesting due to its relevance to hominid evolution. Previous paleoclimate studies from the region have included lake sediments and soil carbonate isotopes, which have been interpreted as showing a long-term trend toward increasing aridity. Lake Malawi records from the last 1.3 million years show a change during the Mid-Pleistocene Transition (MPT) from high frequency variability and generally lower lake levels to higher amplitude variability and higher lake levels punctuated by long, severe droughts resulting in extreme and long-lasting low-stands. Site 1476 cores were scanned using X-Ray Fluorescence (XRF), which gives semi-quantitative elemental abundances. Elemental abundance ratios are used as proxies for a variety of climate-related signals, such as changes in weathering rates, the nature of terrigenous material, and grain size. Looking at the site's Fe/Ca, K/Ca, and Rb/Zr ratios, the period of 4.5 to about 1.5 million years ago shows higher terrigenous flux, higher clay flux, and a smaller grain size respectively than most of the previous 3 million years, followed by a steep decline before the MPT, before transitioning to a pattern of high amplitude oscillations post-MPT. These higher amplitude oscillations seem to correspond to Lake Malawi low stands in the post-MPT period, suggesting that the higher flux of terrigenous material to site 1476 is due to higher aridity resulting in lower vegetative cover. This data also point to high climate variability in the last million years, likely contributing to the evolution and ecological adaptability of our species.
Year of Publication: 2017
Research Program: IODP Integrated Ocean Drilling Program
IODP2 International Ocean Discovery Program
Key Words: 24 Surficial Geology, Quaternary Geology; Cenozoic; Climate change; Expedition 361; IODP Site U1476; Indian Ocean; International Ocean Discovery Program; Mozambique Channel; Paleoclimatology; Quaternary
Coordinates: S154916 S154915 E0414608 E0414608
Record ID: 2019025821
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