山东仙境源黄土常量元素特征及其古气候环境意义

Geochemical characteristics of major elements and their paleoenvironmental significance of the Xianjingyuan loess in Shandong Province

  • 摘要: 通过对南长山岛仙境源黄土的常量元素组成特征进行分析,结合风化判别指标和元素综合参数探讨了该黄土堆积过程中经历的化学风化强度与气候变化特征,并将其与砣矶岛黄土、平阴黄土以及洛川黄土-古土壤进行对比,结果表明:(1)仙境源黄土的主要化学成分为SiO2、Al2O3和CaO,常量元素含量呈SiO2>Al2O3>CaO>Fe2O3>K2O>Na2O>MgO>TiO2>P2O5>MnO的组合特征;(2)仙境源黄土整体处于初等化学风化阶段,并在堆积过程中先后经历了5次暖湿与冷干的气候变化,该区气候环境与全球气候环境的变化之间存在较好的响应关系;(3)山东的粉尘物源和古气候环境总体上存在较高相似性,但因海陆位置与地形的影响使气候环境存在区域性的差异,而仙境源黄土与平阴黄土之间明显的差异表明二者粉尘物源存在差别;(4)对于仙境源黄土与洛川黄土-古土壤在元素组成与风化强度上存在的明显差异,我们认为主要是因粉尘的物源不同导致。

     

    Abstract: The loess deposited in the Miaodao Islands has great significance to the revealing of paleoclimatic and paleoenvironmental changes. In this study, we analyzed the compositional characteristics of the major elements of the Xianjingyuan loess on the Nanchangshan island. Combined with the chemical weathering indexes and integrated elemental parameters, we discussed in this paper the characteristics and intensity of chemical weathering and climate changes during the accumulation of Xianjingyuan loess. Also made are comparisons to the Tuoji loess, Pingyin loess and Luochuan loess-palaeosol. It is revealed that: (1) The Xianjingyuan loess is dominated by the major elements of SiO2, Al2O3 and CaO, and the abundance of major elements are in an order of SiO2>Al2O3>CaO>TFe2O3>K2O>Na2O>MgO>TiO2>P2O5>MnO; (2) Chemical weathering indicators indicated that the Xianjingyuan loess was in an initial stage of chemical weathering; and the integrated element parameters suggest that the region had experienced five times of climatic change from warm and humid to cold and dry, and the climate environment of Xianjingyuan has a good response to the global climate environment; (3) The dust sources and the paleoclimate environment are highly similar to the loess found in Shandong Province, but the regional environment was effected by geographic location and topographic conditions, the obvious difference between Xianjingyuan loess and Pingyin loess suggest that there is difference in dust sources; (4) the difference between the major elements and chemical weathering in Xianjingyuan loess and Luochuan loess-palaeosol owes its origin to the difference of dust sources.

     

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