The Plio-Pleistocene evolution of the Indian Ocean monsoonal system; evidence from the Arabian Sea and East Africa

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http://abstractsearch.agu.org/meetings/2011/FM/PP13A-1819.html
Author(s): Wilson, K. E.; Maslin, M. A.; Mackay, A. W.; Leng, M. J.; Kingston, J.; Deino, Alan L.
Author Affiliation(s): Primary:
University College London, Department of Geography, London, United Kingdom
Other:
British Geological Survey, United Kingdom
Emory University, United States
Berkeley Geochronology Center, United States
Volume Title: AGU 2011 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2011; American Geophysical Union 2011 fall meeting, San Francisco, CA, Dec. 5-9, 2011. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: It is important to identify the teleconnections between high latitude forcing and tropical monsoonal circulation in order to understand climate change in East Africa during the Plio-Pleistocene. Here we present a record of aeolian dust transport to the Arabian Sea between approximately 2.9 and 2.3 million years ago (Ma), constructed from the high-resolution XRF scanning of sediment cores from ODP Sites 721 and 722. Variations in the delivery of aeolian dust to the Arabian Sea, reflected in normalised flux of titanium, show that monsoonal circulation prior to 2.6 Ma, and after 2.5 Ma, was highly variable and primarily driven by orbitally-forced changes in tropical summer insolation, strongly modulated by the 400,000 year cycle of orbital eccentricity. This is confirmed by the presence of lakes in the East African Rift Valley during key eccentricity maxima. The dust record is coupled with the analysis of a well-dated series of diatomite units from the Baringo-Bogoria Basin which document the rhythmic cycling of large, precessionally-driven freshwater lakes which periodically occupied the Central Kenyan Rift Valley between 2.7 and 2.58 Ma. Analysis of one of these lake sequences using stable oxygen isotope measurements of diatom silica, combined with the XRF analysis of whole-sample geochemistry, reveals that the deep lake phase was characterised by fluctuations in rainfall and lake depth over cycles lasting, on average, 1,400 years. The presence of these millennial-scale fluctuations is confirmed by evidence of abrupt climate cycles in the oceanic dust record from the Arabian Sea.
Year of Publication: 2011
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Africa; Arabian Sea; Cenozoic; East Africa; East African Lakes; East African Rift; Indian Ocean; Lake Baringo; Lake Bogoria; Leg 117; Monsoons; Neogene; ODP Site 721; ODP Site 722; Ocean Drilling Program; Paleoatmosphere; Paleocirculation; Pleistocene; Pliocene; Quaternary; Tertiary
Coordinates: N163718 N163719 E0594746 E0594745
N164038 N164039 E0595147 E0595146
Record ID: 2018030601
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