【摘要】 对黄土高原西部的陇西盆地中断岘黄土剖面地层中的磁化率、粒度、CaCO3含量和有机碳含量等气候代用指标进行了综合分析。研究表明,青藏高原东北部地区在末次间冰期以来,其冬、夏季风的变化分别经历了多次相对增强的时期;其演化阶段基本可与深海氧同位素曲线(SPEC-MAP)对比,并且与同期的印度洋季风强度变化存在着较高的一致性。由此可以认为,全球冰量变化可能不是控制青藏高原季风演变的决定因素,而其它因素如太阳辐射变化及高原下垫面状况对高原季风演化可能具有更为重要的意义。更多还原

【Abstract】 Duanxian loess section of 40m thick is located at the seventh terrace of the Huanghe River,a pediment of Longxi Basin lying to the west of the Liupanshan Mountains in the northeastern Qinghai-Xizang Plateau.According to the 14C and TL age dating from six paleosol horizons and five loess layers which were found in the Duanxian section,it was estimated that the bottom of the section is at the boundary between MIS 5 and 6,and it can be compared with S1 in the Loess Plateau.Magnetic susceptibility,CaCO3 content and total organic carbon content are widely used as proxies of summer monsoon changes and grain size as proxy of winter monsoon.These proxies of a loess-paleosol sequence in Duanxian were measured.Their variations show that the northeastern part of the Qinghai-Xizang Plateau experienced 5 times of enhanced winter monsoon and 6 times of enhanced summer monsoon periods,respectively,since the last interglacial epoch.Although the variation of the Qinghai-Xizang Plateau monsoon can be compared with the oxygen isotopic stages in deep sea,outstanding difference exists between them.The strength of summer monsoon in interglacial epochs in northeastern Qinghai-Xizang Plateau is not always stronger than that in glacial epochs.The good correlation between variation of monsoon in the plateau and the Indian Ocean monsoon suggested linkage of them in similar forcing factors.Therefore,the results to conclude that changes of the Qinghai-Xizang Plateau monsoon may not be controlled by the change of global ice volume.On the contrary,orbital forcing might be responsible for climate changes in the northeastern Qinghai-Xizang Plateau since at least the last interglacial epoch.更多还原