Sediment Characteristics And Paleoenvironmental Significance Of Core DLW3101 From Northern Slope Of South China Sea

As the largest marginal sea in China, South China Sea have high rate of sediment,its sediments record information about the changes in marine environment and the paleoclimate change in East Asia. The South China Sea has become an ideal place to study the present and past global climate change, and the northern slope of South China Sea is the hot areas of the South China Sea paleoceanography study. In this paper, we choose the slope sediments(core DLW3101) in Northern South China Sea to make grain-size, calcium carbonate, carbon\oxygen isotope and XRF element scan test. Based on the analysis of experimental data we obtained some comprehension about paloclimatical and paloenvironmental indexes about the northern slope of South China Sea. Detailed conclusions are shown below:1、Using the planktonic foraminifera oxygen isotope curve to establish the age mode of the core of the past 306 kyr. The deposition rate during glacial period is higher than interglacial period.2、The grain size of this core is very stable, with silt and clay based. Two master control factors F1 and F2 were obtained from the main ingredient factorial analysis to grain size of terrigenous clast in DLW3101 core. F1 is controlled by two grades 2.32μm-13.14 μm and 22.1 μm-63 μm. F2 is controlled by only one grade 0.35 μm-1.16μm. 0.175 μm-17.105 μm, 17.105 μm-162.75 μm and >162.75 μm, these three different environmental sensitive grain size fractions were obtained from the grade-standard deviation method. The content of >162.75 μm is almost zero. Fine grain size of 0.35 μm-1.16 μm, 2.32 μm-13.14 μm, and 0.175 μm-17.105 μm grades show the same change rule. High values of these three grades may represent the enhancement of the East Asian summer monsoon and the rise of the sea level. Coarse grain size of 22.1 μm-63 μm and 17.105 μm-162.75 μm grades show the same change rule. High values of these two grades may represent the enhancement of the East Asian winter monsoon and the decline of the sea level.3 、 Spectrum analyses to different grain size composition contents of core DLW3101 shows that core DLW3101 is influenced by the change of the sea level and the East Asian monsoon which is driven by the tropical low latitude process.Eccentricity period of 103 kyr represents the interglacial-glacial cycle changed the input of the grain size indexes. Precession period of 28 kyr represents the East Asian monsoon, which is driven by the tropical low latitude process, influenced on the grain size indexes.4、Based on the analysis data of elementary geochemistry in DLW3101 core,Al/Ti and K/Ti ratio are adopted to reflect chemical weathering degree of sediments source area. These two indexes show higher during interglacial period and lower during glacial period, illustrate that the East Asia summer monsoon of northern South China Sea was popular during interglacial period and the chemical weathering of sediment source area was very strong.5、The analysis of grain size and elementary geochemistry about DLW3101 core shows that in Isotope Stage 3 global climate is in a weak warm period and not stable,the frequency of dry and wet changes is very high.