A Carbonate Platform Record of Neogene Paleoenvironmental Changes in the Indian Ocean (Maldives)
Abstract
The Maldives Inner Sea is a natural sediment trap which preserves a 25 Myrs record of paleoenvironmental changes in the Indian Ocean. This encompasses records of past changes in sea level, productivity, and circulation, but also of the dust influx. As such, the sedimentary succession, which has been cored during IODP Expedition 359, provides the opportunity to study the evolution and the dynamics of the South Asian Monsoon. This amends the reconstruction developed in other, mainly siliciclastic records such as in the Bengal and Indus fan deposits. Seismic-, downhole-, and core data show that windblown dust has been deposited in the Maldives since 22 Ma. However, from 22 to 13 Ma the sedimentation in the Maldives under a weak monsoon was mainly controlled by sea level changes. At 13 Ma this situation changed, and wind driven currents started to control sedimentation, as reflected by the onset of widespread drift deposits. This is interpreted to reflect a more vigorous atmospheric circulation. Linked to the current onset, there was a rise of productivity and a coeval expansion of the oxygen minimum zone. Changes in magnetic susceptibility during the Late Miocene and Pliocene, as imaged in downhole magnetic susceptibility logs are interpreted to reflect fluctuations of the dust influx, mainly from the Indian subcontinent. The combination of XRF data and non-carbonate grain-size data allows a further and detailed reconstruction of variations in the dust influx and bottom-current changes for the last 4 Myrs.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFMOS54B..07B
- Keywords:
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- 1051 Sedimentary geochemistry;
- GEOCHEMISTRY;
- 3022 Marine sediments: processes and transport;
- MARINE GEOLOGY AND GEOPHYSICS;
- 3036 Ocean drilling;
- MARINE GEOLOGY AND GEOPHYSICS;
- 8177 Tectonics and climatic interactions;
- TECTONOPHYSICS