东海陆架晚更新世以来沉积物常量元素的分布及其地质意义

Content Distributions and Its Geological Implication of Major Elements in Sediments from the Continental Shelf of the East China Sea During the Late Pleistocene

对东海陆架西湖凹陷区SFK-1孔的岩性、粒度、常量元素以及测年数据的综合分析表明:元素地球化学信息对于地层的划分有良好的指示意义。SFK-1孔沉积物常量元素质量分数平均值分别为SiO265.35%、Al2O3 12.12%、FeO 1.75%、CaO 3.88%、MgO 2.04%、K2O 2.63%、Na2O 2.04%、TiO20.66%、P2O50.12%、MnO 0.065%、TFe2O34.74%、CaCO35.38%,标准差系数较小,反映SFK-1孔常量元素离散程度较小。SFK-1孔沉积物CaCO3/TiO2、CaO/TiO2和P2O5/TiO2反映了化学风化程度的强弱;TiO2/Al2O3可以作为古水流能量的指标,反映当时河流水动力条件的影响强度;而SiO2/TiO2、Na2O/TiO2可以用来反映沉积水动力的强度。依据常量元素质量分数垂直变化特征划分的8个层段分别与沉积物粒度、气候变化地层划分界线吻合。研究区自91ka BP以来沉积环境经历了剧烈变化,它们分别反映了末次间冰期(暖期)晚期以来东海陆架区沉积环境的变化。

Based upon analysis of lithology,grain-size,major elements and dating data for core SFK 1,which is located in the depression area of Xihu on the continental shelf of East China Sea,this contribution studied the geochemical characteristics of sediments since the Last Pleistocene.The results showed that geochemical information of elements has good indicator significances to stratigraphicaldivision.The mean of each major element was respectively SiO2 65.35%,Al2 O3 12.12%,FeO 1.75%, CaO 3.88%,MgO 2.04%,K2 O 2.63%,Na2 O 2.04%,TiO2 0.66%,P2 O5 0.12%,MnO 0.065%, TFe2 O3 4.74%,CaCO3 5.38%,with less coefficient of variation,indicated a smaller divergent extent of major element.The variations of CaCO3/TiO2 ,CaO/TiO2 and P2 O5/TiO2 ratios can reflect the intensity of weathering;The TiO2/Al2 O3 ratio can be used as a paleo-stream energy indicator to reflect the intensity of stream hydrodynamic conditions;The variations of SiO2/TiO2 ,Na2 O/TiO2 ratios can be used as proxies to reconstruct the sedimentary hydrodynamic conditions for the whole core sediment. The divisions of the 8 layers are respectively connected with the grain size of sediment,climate change boundary,strata boundaries according to the vertical variation characteristics of major elements,which reflect the change of sediment environment in East China Sea since the late last interglacial cycle （warm period）.