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通过对黄土高原南缘白鹿塬黄土剖面8种主要元素含量的测定,研究了该地区元素地球化学的演化及其指示的古气候意义。最近140ka以来的氧化物演化序列中,Al2O3、K2O、MnO和TiO2的变化趋势与磁化率相同,在黄土中高,在古土壤中低,表明黄土中风尘物质的风化程度明显弱于古土壤,这与野外观察的黄土地层变化相一致。Na/Al和Fe/Al分别作为指示粉尘沉积物的风化成熟程度和粉尘来源物质变化的地球化学指标,它们的演化与深海SPECMAP和GRIP冰心中氧同位素曲线对比良好,表明中国北方干旱与半干旱区的古气候变化主要受控于地球轨道的变化,与全球气候变化具有一致性。另外,剖面中Fe/Al比值的地球化学演化对气候变化的反映很敏感,表现出高频震荡的变化特征。
Based on the determination of eight major elements in the Loess Plateau in the southern edge of the Loess Plateau, the evolution of element geochemistry and its paleoclimate significance in the area were studied. The change trend of Al2O3, K2O, MnO and TiO2 in the sequence of oxide evolution since the last 140 ka is the same with the magnetic susceptibility, high in loess and low in paleosol, indicating that the weathering of dust and dust in loess is weaker than that of paleosol It is consistent with the change of loess stratum in the field. Na / Al and Fe / Al, respectively, serve as geochemical indicators for the degree of weathering and maturity of dust sediments and dust source materials. Their evolution is in good contrast with the oxygen isotope curves of SPECMAP and GRIP ice cores in the deep sea, indicating that the arid and semi-arid The paleoclimatic changes in the area are mainly controlled by the changes of the Earth’s orbit and are consistent with the global climate change. In addition, the geochemical evolution of the Fe / Al ratio in the profile is sensitive to the change of climate and shows the characteristics of high-frequency oscillations.