Sea-level and monsoonal control on the Maldives carbonate platform (Indian Ocean) over the last 1.3 million years
Abstract. Changes in sea-level are linked to glacial-interglacial variability and have been claimed as the main factor controlling the production of carbonate platform factories. The Maldives archipelago (Indian Ocean), composed of two rows of atolls that enclose an inner sea, is a very sensitive region to sea-level changes. The sediments of the Inner Sea, offer an excellent study site to explore the impact of sea-level changes on carbonate platforms. Elemental geochemical composition records, obtained by X-ray fluorescence (XRF) core-scanning, from the Maldives Inner Sea (IODP Site U1467), have been used in this work to evaluate the influence of orbitally-driven sea-level fluctuations on the carbonate production and export from the neritic environment into the Maldives Inner Sea over the last 1.3 million years. High Sr aragonite-rich carbonates (HSAC) from neritic settings are deposited in the Maldives Inner Sea during sea-level highstand intervals, increasing the values of the Sr/Ca ratio. In contrast, during sea-level lowstand periods large areas of the atolls were exposed or unable to grow and the demise in the carbonate production and sediment export is reflected as low Sr/Ca values in the Inner Sea. However, we propose that sea level is not the only factor controlling the production of HSAC during sea-level highstands since several interglacial periods before and after the Mid-Brunhes event (MBE, ~430 ka) indicate high carbonate production (high Sr/Ca). The intensity of the summer monsoon and the Indian Ocean Dipole probably modulated the production at the atolls. Marine Isotope Stage 11 stands out as a period with high sea-level and rather high carbonate production in the Maldives platform. This extraordinary carbonate production in the Maldives atolls (and in other low latitude carbonate platforms) probably contributed to the Mid-Brunhes dissolution event through a strong shelf-to-basin fractionation of carbonate deposition.
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