最后两个冰期旋回季风-沙漠系统不稳定性的高分辨率黄土记录

黄土高原西北部黄土沉积的粒度变化同时受控于沙漠进退和冬季风强度波动,因此,此区粒度可视为季风-沙漠系统变迁的替代性指标。本研究以2cm为间隔,对李家塬和新庄源S₂以上部分做了粒度分析。结果表明,倒数第二次冰期中的冰阶时段与末次冰期类似,存在着频繁的千年尺度的气候波动；而末次间冰期这类变化并不明显。

HIGH-RESOLUTION CLIMATIC RECORDS OF THE LAST TWO GLACIATIONS:EVIDENCE FROM LOESS-SOIL SEQUENCES,NORTH-CENTRAL CHINA

The Xinzhuangyuan and Lijiayuan loess sections in the northwestem part of the Chinese Loess Plateau were studied down to the paleosol tnt S2, which was formed during the marine oxygen isotopic stage 7. The thickness of the loess-soil sequence above S, is about 63 m at Xinzhuangyuan and 43 m at Lijiayuan. Samples were taken at 2 cm intervals from both of the sections. TIs sample spacing yields a mean depositional resolution of 50-80 years for the last and Penultimare glacial loess layers of L, and Li, and about 200 years for the last interglacial soil unit S1, thus enabling us tO reconstruct high-resolution climatic changes during the last two glacialinterglacial cycles. Grain size was measured on a total of 5 300 samples. The grain-size records are regarded as a proxy of changes in the monsoon-desert system over northern China. ResultS show that frequent large-amplitude climatic oscillations on millennial bine scales occurred during the Penultimare glaciation in a manner similar to that during the last glaciation, suggesting that sub-orbital scale climatic variations may be a common featUre of the climate system during glacial periods of the late Pleistocene. The last interglacial soil S, is composed of three individual soils and tWo thin intervening loess horizons in both of the sections. Short-term variations in grain-size are not prominent within the soil complex, implying the absence of strong millennial -scale climatic oscillations during the last interglaciation in northern China.