沙漠—黄土过渡带杨桥畔全新世地层及沉积环境研究

Holocene Strata of the Yangqiaopan Section in Desert-Loess Transitional Zone and Its Sedimentary Environment

通过对沙漠—黄土过渡带杨桥畔全新世风成砂—砂质黄土—砂质古土壤型地层序列的粒度、磁化率、硅铁铝率和全铁含量等多项气候环境代用指标的综合分析,并结合光释光（OSL）与14CAMS测年结果资料,探讨了近万年以来该地区的古气候环境演化过程。研究结果表明：13.0~11.7ka B.P.,气候干冷,环境恶劣,沙漠处于扩张活化阶段;11.7~10.0 ka B.P.,气候趋于略温干,沙漠处于半固定—半流动状态;10.0~6.4 ka B.P.,气候温和偏湿,为该地区全新世适宜期,沙漠处于（半）固定状态;6.4~1.6 ka B.P.,气候偏冷干,沙漠处于半固定—半流动状态;1.6~0 ka B.P.,气候继续向冷干方向发展,并且存在着气候冷暖频繁交替。

By the systematic measurement and analysis of grain size,magnetic susceptibility,silica sesquioxide ratio,total iron content,optically stimulated luminescence（ OSL） and14C- accelerator mass spectrometry（14C- AMS） dating data of the Yangqiaopan section in the desert- loess transitional zone,the paleoclimate and paleoenvironment evolution in the Yangqiaopan district during the holocene were discussed emphatically. The aeolian sand- sandy loess- sandy paleosol sedimentary sequence of the Yangqiaopan deposits in the desert- loess transitional zone not only recorded the paleoenvironment evolution of Mu Us sandy land in historical time,but also included the paleoclimate change information of the East Asian monsoon. The paleoclimate change and paleoenvironment evolution in the Yangqiaopan district could be divided into several stages： The climate there was cold and arid during 13. 0- 11. 7 ka B.P.,and the desert expanded. The climate tended to be slightly warm and arid during 11. 7- 10. 0 ka B. P.,and the desert was in the semi fixed and semi flow state. The climate was warm- moist during 10. 0- 6. 4 ka B. P.,and the desert was in the fixed- half state.The climate became slightly cold- arid during 6. 4- 1. 6 ka B. P.,and the desert was in the semi fixed and semi flow state. The climate sustained cold- arid climate condition since 1. 6 ka B. P.,whereas its changes with cold and warm alternated frequently.