Study on Sedimentary Records of Paleoclimate and Paleoenvironmental Evolution of the Dongsha Atoll of South China Sea in Recent 70 Thousand Years

摘要

The Dongsha Atoll of South China Sea are located on the western reef terrace of Dongsha Atoll, where a large amount of terrigenous clastic materials and marine biomass are accumulated, which play an important role in the global material cycles. In recent years, the water level in this area has been on the decrease along with the frequent occurrence of floods, red tides, low-oxygen conditions and warmer waters as a result of worsening global ecology. In this paper, accelerated mass spectrometer (AMS) 14C was used to analyse the sediments in Dongsha Atoll of South China Sea, and studied the organic matter deposition in this area in the past 70,000 years combined with sediment grain size, geochemistry and other indicators, which revealed the influence of paleoclimate environment and climate change on the development of this area. The results showed that the environment and climate are essential to the distribution of particles, which can be divided into three layers from bottom to top, i.e., calcium-rich layer, organic matter layer and fine-grained sediment layer. Al2O3, K2O, TFe2O3 and MgO contribute 58.84% to the total variance, indicating that the composition plays a decisive role in the content of major elements in the region. Turbidity sediments have been widely distributed in different areas of the region since last glacial period, among which turbidity occurred most frequently in the period 200,000 years ago when the sea level was relatively low. This study provided a theoretical basis for the evolution of climate and environment in the South China Sea.