Dynamic control on grain-size distribution of terrigenous sediments in the western South China Sea: Implication for East Asian monsoon evolution
Dynamic control on grain-size distribution of terrigenous sediments in the western South China Sea: Implication for East Asian monsoon evolution
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DOI：
10.1007/s11434-008-0078-y
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发表时间：
2008-06
影响因子：
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通讯作者：
Guocheng Chen;Hongbo Zheng;Jianru Li;Xin Xie;X. Mei
中科院分区：
文献类型：
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作者：
Guocheng Chen;Hongbo Zheng;Jianru Li;Xin Xie;X. Mei
对南海西部越南东部海域的MD 05 -2901岩心进行了高分辨率氧同位素地层学研究，结果表明该岩心的时间跨度约为450 ka。根据沉积物的体积密度、孔隙度和岩石成分，得到了间冰期的陆源物质积累速率（TMAR）为4.9-6.0 g cm−2ka− 1，高于冰期的1.9-5.0 g cm − 2ka −1，这与北方和南部冰期TMAR较高的情况不同。通过对所有样品粒度分布的主成分分析，得到了两个主要的控制因子（F1和F2），它们对粒度变异的贡献率约为80%。对F_1敏感的1.26-2.66 μm%和10.8-14.3 μm%的粒级含量波动频率较高，与15°N夏季日照有较好的相关性。它们在23 ka和13 ka附近具有明显的旋回性，而在4.24-7.42 μm%和30.1-43.7 μm%的代用指标中，在100 ka附近有一个强的频率峰，主要受F2控制。这部分南海的沉积特征受南海西南和北部两个主要源区输入通量变化的控制，这两个源区分别受东亚夏季风和冬季风驱动的不同表层流环流的输送。我们认为，东亚夏季风的波动频率很高，并受低纬太阳辐射变化的影响，与岁差和半岁差有关，而冰量强迫可能是决定东亚冬季风强度和时间的主要因素，但太阳辐射强迫作用不太重要。
High-resolution oxygen isotope stratigraphy of Core MD05-2901, which is located off eastern Vietnam in the western South China Sea (SCS), was established and indicated that the core spans a time period of the past 450 ka. Based on the bulk density, fractional porosity and lithogenic content of the sediments, terrigenous mass accumulation rate (TMAR) was obtained, which is 4.9–6.0 g cm−2ka−1on average during interglacial stages, higher than that during glacial stages, i.e. 1.9–5.0 g cm−2ka−1, which is different from northern and southern SCS which show higher TMAR in glacial stages. By principle component analysis of grain size distribution of all the samples, two main control factors (F1 and F2) were obtained, which are responsible for about 80% variance of granularity. The contents of grain size population 1.26–2.66 μm% and 10.8–14.3 μm% which are sensible to F1 show high-frequency fluctuation, and correlate well with the summer insolation at 15°N. They exhibit a distinct cyclicity with frequencies near 23 ka and 13 ka, in contrast to a strong frequency peak near 100 ka obtained in proxies 4.24–7.42 μm% and 30.1–43.7 μm% controlled mainly by F2. The sedimentary character of this part of the SCS was controlled by variations of input flux from two main source areas, namely the southwest and north SCS, which were transported by different circulations of surface current forced by East Asian summer monsoon and winter monsoon respectively. We believe that the East Asian summer monsoon has fluctuated with high frequency and been forced by changes in solar insolation in low latitude associated with precession and half precession, while ice-volume forcing is probably a primary factor in determining the strength and timing of the East Asian winter monsoon but with less important insolation forcing.