Deep-sea Pollen From The Southern South China Sea And Its Correspondence To Global Climate Changes

In order to study the vegetation and climate related to the East Asian Monsoon System around 2.5MaB.P., and to better understand the response of vegetation evolution to global climate changes, pollen samples in Site1143 deep-sea sediments from ODP Site 1143 in southern South China Sea(SCS) were analyzed. Based on high-resolution(7ka) pollen records, the pollen-assemblage sequence and the vegetation evolution series during 3.0 ～ 2.0MaBP were rebuilt. The research emphasizes on the response of vegetational evolution in the SCS ambient areas to climatic variations during this period. The result provides a line of important evidence for the research of the history of Asian paleo-Monsoon and paleo-environments. Site 1143(9o22′N,113o17′E)deep-sea sediments were drilled during Ocean Drilling Program(ODP) Leg 184 at a water depth of 2772m in Nansha area. A total of 146 samples with an average time resolution of 7 000 years were analyzed at the depth of 135～95m(3.0～2.0 Ma B. P.). Based on the results of biological stratigraphy and oxygen-isotope chronology, the ages of pollen samples were deduced. The pollen samples were prepared mainly by using hydrochloric and hydrofluoric acids to remove carbonates and silicates. To concentrate pollen and spores, the remaining material after acid reactions was sieved in an ultrasonic bath. The identification and statistic of pollen were performed under optical perspective microscope. The results are as follows: 1. The pollen influx has a distinct change. The average value of pollen influx during 2.6～2.0 Ma B. P. is different from that of 3.0～2.6 Ma B. P., with a notable raise. The fact shows that the sea level of the SCS fell distinctly at 2.6 Ma B. P., corresponding with the formation of the Northern Hemisphere glaciation and the enhancement of the East Asian Monsoon. 2. The correspondence of pollen influx changes with oxygen isotope stages represents many times of glacial-interglacial gyration, indicating that many times of rise and fall of the sea level of South China Sea occurred after 2.6 Ma B.P.. 3. Results of spectrum analyzing show that there existed 0.1 Ma(eccentricity) and 46.9ka(obliquity) cycles during 3.0～2.0Ma B. P..