The Changes in Eolian and Alluvial Sediment Fluxes to the Oman Margin of the Arabian Sea During the Mid-Late Pleistocene Period.

High resolution studies on the variations in sediment source of the dust-dominant Oman margin can contribute to understand the influence of climate systems on sediment flux to the Arabian Sea. This study was carried out using the ODP leg 117 Hole 728 A sediment core located on the continental margin of Oman.

Chemical composition (XRF) and color reflectance (DSR) measurements were taken at 1 cm resolution along the core axis of the top 4.5 m using ITRAX core scanner at KOCHI core center Japan. A high-resolution age model constructed by combining tie points of the a* (red (+) green (-) contrast) record with the NGRIP2 ice core δ¹⁸O record and points from the age model by Busch(1991) yielded 90 ka for the studied section. Two principal components (PCs) of the first derivatives of color reflectance data, DSR- PC1 (Chlorite and Illite) and DSR-PC2(Hematite), and one PC from XRF composition data, XRF-PC1 (K, Mn, Fe, Ti), were used to identify the source. L* (brightness), Ca/Ti, and Ni was also used to verify interpretations.

Results show that L*, XRF-PC1, DSR PC1 increase during stadials (MIS2 and MIS4) and decrease during interstadials (MIS1 and MIS3). In contrast, DSR PC2, a*, Ni, and Ca/Ti show the opposite behavior. Increase in DSR-PC1 which is correlating with illite+chlorite, major constituents of the dust in Arabian Peninsular, and XRF-PC1 which has a high correlation with constituent elements (K, Fe) of the above minerals, indicate that they represent aeolian component. Opposite behavior of L* with Ni which are considered as proxies for organic matter indicates that L* increases due to an increase in brightness by dust during stadials. The increase in a* (redness) and hematite during interstadials shows that alluvial material was the major terrigenous component during warm periods.

Heinrich events H1-H6 are marked by lower dust input and increased alluvial input resulted by increased winter monsoon which is the major source of rain in the Arabian Peninsular. Warm intervals of DO cycles are marked by increased dust input and decreased alluvial input due to the increased northwesterly wind which is the major source of dust and decreased winter monsoon rain.

Therefore, results show that sediment source of Oman Margin is controlled by both longer scale global stadial-interstadial variability and shorter, regional monsoon variability.