Spectral reflectance analysis of SW and N of the South China Sea with their paleoenvironmental variation

To reconstruct a long time scale paleoenvironmental variation of a certain area has been challenging usually because the lack of the accessibility of long continuous sedimentary records and the selection of a robust proxy. As the largest marginal basin in SE Asia initiated in early Cenozoic, namely the South China Sea (SCS), it provides an ideal location for the paleoenvironmental work as its sediment record from deep sea environment could span from Paleocene to presence. Multiple proxies have been carried out by previous work to recover the local paleoclimate evolution of SE Asia which is commonly accepted to be under the influence of East Asian Summer Monsoon (EASM). However, consensus of this atmospheric circulation records in Cenozoic has not been achieved due to each individual proxy's limitation. Therefore, taking advantage of applying multiple proxies will significantly improve the reliability of those plaeoenvironmental reconstruction. In this study, we used a new method, developed from Spectral Reflectance Scanning of sedimentary cores, to indicate a 10 Ma, 3 Ma and 15 kys record from several International Ocean Discovery Program(IODP) sites within the South China Sea. With this high-resolution records (sampled every 5 cm) of Hematite/Goethite (565nm/435nm), we attempt to reconstruct a record of humid versus arid from million to millennial scale and to test if SW SCS underwent the same climatic impact as N SCS which have two different provenances. Geochemical data, clay mineral assemblage and palynological results from these deep sea drilling sites are also combined with our spectral reflectance data to better constrain this question. Our result shows that two different trend among these proxies are observed from the sites of SW and N SCS, we conclude this to be a result of the impacts from other fluvial system which delivers the sediment in different patterns, and also could be an interaction between multiple climatic circulation instead of a single EASM's impact, such as a mixture between EASM and South Asian Summer Monsoon for those SW SCS sites.