中国东部近海沉积物地球化学:分布特征、控制因素与古气候记录

Geochemical Characteristics,Controlling Factor and Record of Paleoclimate in Sediments from Eastern China Seas

本文系统总结了中国东部近海沉积物中常、微量元素分布特征、控制因素及全新世以来的古气候沉积记录。指出表层沉积物中Si O2和Al2O3含量最高,两者可占沉积物总量的75%以上,而其他元素含量较低,且空间分布变化明显,主要受控于陆源物质输入、生物沉积作用、海洋化学沉积和成岩作用等因素。长江和黄河贡献了主要的陆源物质,非线性规划数学模型结果显示两者大致以123°E和32°N为南北向和东西向分界线,黄河物质控制了渤海和黄海大范围的区域,而长江物质则主要影响东海内陆架区域。东海内陆架泥质区南部的MZ01孔沉积物中CIA、Ba/Sr和Ca O/Mg O值指示了中全新世以来中国东部气候演化历史：8400-4200 a BP期间为暖湿期;4200-2300 a BP期间为波动变冷期;2300 a BP以来为持续的变暖期。功率谱分析表明太阳活动对中国东部古气候的周期性演化过程具有控制作用。

Geochemical characteristics and distribution pattern of surface sediments from eastern China seas were studied and the paleoclimate evolution since the mid-Holocene were further reconstructed in this paper. The results showed that the Si O2 content,with a mean up to 63%,are highest in the sediment samples,Al2O3 content is the next to Si O2,having a mean of 12%,consequently,the total of other elements take up a very small proportion. R-factor analysis revealed the compositions of major and trace elements are controlled by multiple factors,such as terrigenous clastic matter,marine biogenous sediment,marine chemistry and diagenesis. The Yangtze River and the Yellow River carried dominating terrigenous sediments to the sea field,a mathematic method model was produced to calculate the sediment provenance quantitatively. Based on the model and the tracers,the boundary was determined at 123°E and 32°N,the Yellow River controlled the most area of the Bohai Sea and the Yellow Sea,while the Yangtze River mainly controlled the inner shelf of the East China Sea. Geochemistry proxies including CIA,Ba / Sr and Ca O / Mg O were chosen to reconstruct the paleoclimate evolution in the eastern China seas,we found that from 8300 a BP to 4200 a BP the climate was moderately warm and humid.From 4200 a BP to 2300 a BP the climate was cool and dry,with large fluctuations between cool-dry（ 3700 a BP,2850 a BP and 2400 a BP） and warm-wet（ 3250 a BP and 2650 a BP）. Since 2300 a BP,our records indicated that the climate had gradually become warmer,although some cold events centered by the Little Ice Age interrupted this warming trend. We also found significant 238 yr cycles in our CIA records that imply a possible solar influence on the regional climate changes since the mid-Holocene.