腾格里沙漠南缘末次冰消期气候不稳定性记录

INSTABILITY RECORD OF THE LATE GLACIAL IN THE SOUTHERN TENGGER DESERT

通过对红水河剖面元素地球化学和孢粉以及地层岩性的分析,在讨论了沉积地层连续性和记录完整性的基础上,重建了腾格里沙漠南缘末次冰消期的气候环境演变序列。结果表明,沉积物中Ca,Fe,Mg,K,Na和Mn等元素含量的变化以及结合其不同的孢粉组合,不仅与沉积环境紧密相关,而且可以很好地揭示该地区晚冰期以来气候环境变化的基本特征和历史,显示研究区在13.6～9.7cal.kaB.P.期间主要经历了以下几个阶段:13.60～13.08cal.kaB.P.,12.75～12.20cal.kaB.P.和11.60～10.45cal.kaB.P.期间气候较温暖湿润;13.08～12.75cal.kaB.P.和10.45～9.70cal.kaB.P.期间气候相对冷干;而在12.2～11.6cal.kaB.P.期间,则表现相对冷湿。自11.6cal.kaB.P.之后,研究区进入全新世暖期,元素Ca,Fe,Mg,K,Na及Mn的含量和孢粉A/C比值变化曲线均表明在全新世初期气候波动频繁,并在11.3cal.kaB.P.和10.5cal.kaB.P.左右出现较强的冷波动。通过与其他研究区地质记录对比,指出研究区腾格里沙漠南缘末次冰消期气候环境变化尽管存在一定的区域特点,但基本格局与全球气候变化一致。

The studied section is 600cm thick and 12 stratigraphical units can be identified. Based on the field observation results,it was found that the depositional structures, color and grainsize changed abruptly at the depth of 370cm to 416cm and 580cm,it was concluded that there were deposition hiatus in the section. Further conventional ^14C datings proved these facts. Therefore,only the upper 370cm thick section has been studied. The sampling was carried out once every 10cm in the coarse sandy layers and once every 5cm in the fine clay-sand layers. A total of 54 samples were obtained for pollen analyses and 43 samples for element analyses. The chronology establishment was based on 12 conventional ^14C datings on organic matters and inorganic carbonates of 8 samples. The results shows that pollen data from the section presents nearly synchronous, close correspondence with major elements contents such as Ca, Fe, Mg, K, Na and Mn, indicating vegetation rapid response to deglacial climate oscillation between 13.6cal. kaB. P. and 9.7cal. kaB. P. From 13.6cal. kaB. P. to 12.2cal. kaB. P., the climate condition improved and can be divided into three stages： two mild and wet stages between 13.60 - 13.08cal. kaB. P. and 12.75 - 12.2cal. kaB. P., and a cold and dry stage from 13.08cal. kaB. P. to 12. 75cal. kaB. P. But the climate deteriorated and became cold and wet during 12.2 - 11.6cal. kaB. P., corresponding to the Yonger Dryas （YD） event. A mild and wet climate returned from 11.6cal. kaB. P.,but it was characterized by strong instability,which was recorded by rapid shifts of both A/C ratio and elements contents. Two extremely cold events occurred around 11.3cal. kaB. P. and 10.5cal. kaB. P. corresponded with the other records in the world. Our results indicate that though climate change in Tengger Desert possesses strong regional characteristics,it is generally consistent with the global climate change pattern, especially the abrupt climate change signals. Therefore, the regional climate change process was controlled by the similar mechanisms under the global climate change background.