西太平洋807A孔的元素地球化学特征及其对中更新世气候转型期的记录

ELEMENT GEOCHEMICAL RECORD OF THE WESTERN PACIFIC OCEAN SITE ODP807A: IMPLICATION FOR THE MIDDLE PLEISTOCENE CLIMATE TRANSITION

  • 摘要: 通过对ODP 807A孔上部60.77 m样品进行元素地球化学分析,揭示了晚上新世3.2 Ma以来的沉积物元素含量变化特征。结果显示元素含量在中更新世过渡期均发生明显变化,具体表现为与陆源碎屑密切相关的元素含量下降,生物源元素含量显著上升,而同期物源区岩石类型没有发生明显变化。陆源元素含量的降低是由陆源碎屑含量降低导致的,反映出中更新世过渡期风搬运能力较弱。生物源元素含量的上升主要受生物生产力提高的影响。稀土元素总和(∑REE)的频谱分析显示了元素地球化学对中更新世气候转型的响应,即主导周期从41 ka过渡到100 ka。

     

    Abstract: The element geochemical analysis of the upper 60.77 m section of ODP Hole 807A reveals climatic variations since 3.2 Ma. Significant changes in element concentrations during the Middle Pleistocene Transition (MPT) are marked by decreases of elements related closely to terrigenous clasts and increases of biogenic elements. Because there was little change in the provenance of terrigenous elements, variations in the terrigenous clastic content were mainly affected by the reduction itself, indicating the weaker wind transportation. The obvious increase of biogenic elements was attributed to the marked enhancement of the ocean productivity during the MPT. Furthermore, the spectral analysis of the sum rare earth elements (∑REE) shows the orbital characteristics of tropical climate changes from 41 ka to 100 ka periods.

     

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