The Ti/Al molar ratio as a new proxy for tracing sediment transportation processes and its application in aeolian events and sea level change in East Asia

Abstract

Ti/Al molar ratios of sediments in various sedimentary environments are used to explain sediment transportation from source regions to sink areas. Samples were collected from outcrops, soils, fluvial, lake, and marine sediment environments. Initial Ti/Al molar ratios of sediments are controlled by those of parent soils or rocks. These ratios tend to decline gradually as a result of heavy-mineral gravity fractionation during transportation. Sedimentary Ti/Al molar ratios in sink areas such as lakes and pelagic environments are lower than those in source regions. In this study, for the Changjiang River, Huanghe River, and Kaoping River, Ti/Al molar ratios decline considerably from downstream to estuary environments. Additionally, well sorted aeolian sands have extremely low Ti/Al molar ratios in northern China. The Ti/Al molar ratios of aerosol particles found in Taiwan and the East China Sea show reduced ratios as a result of Asia Dust Storm episodes. Furthermore, lower Ti/Al molar ratios in deep ocean sediments were discovered by tracing the distribution of sedimentary Ti/Al molar ratios in the South China Sea. When sea levels dropped during glacial periods, the river estuary was closer to deep marine areas and carried more terrestrial sediments into deep marine environments. The closer estuary with relatively higher Ti/Al ratio would lead increase of Ti/Al molar ratios in deep sea sediments. In this study, Ti/Al molar ratio is promoted as a new proxy to help with understanding changes in sedimentary environments.