晚更新世晚期以来古尔班通古特沙漠南部的气候环境演化

THE CLIMATE-ENVIRONMENT CHANGES IN THE SOUTH OF GURBANTUNGGUT DESERT SINCE 80ka BP

本文通过对古尔班通古特沙漠南部的一个钻孔剖面沉积物沉积物沉积特征的分析 ,证明该沙漠南部地区在晚更新世晚期气候相对寒冷 ,并有两次气候偏湿波动 ;全新世时期 ,该区气候以温暖干旱为主 ,全新世中期有一次明显的气候偏湿波动。

Gurbantunggut Destert is the second largest desert in China. Some samples was taken from a borehole section in a depth of 34.5m in the south of Gurbantunggut desert in 1993. Based on the studies of the Quaternary sediments, such as dating of TL, analyses of spore and pollen, sand grain size, geochemical elements, minerals, and miniature structure in the sand surface, some information about climate environmental changes in the south of Gurbantunggut desert since 80 ka BP have been analysed. As most of spores and pollens which were contained in these samples were those of arid plants, the south of Gurbantunggut Desert has been controlled by arid climate since 80 ka BP Two spore pollen groups can be devided in this borehole section. One is Ephdera-chenopodiiaceae-Artemisia group, which indicates that the climate was colder and humider during the period from 80ka BP to 12 ka BP than that of today. Another is Artemisia-Chenopodiaceae-Ephedra group, which indicates that the climate is similar to that of today during the period from 12ka BP to now. Sand grain size was measured according to the standard of Foker and Woder. The sand layers deposited during the period from 80 ka BP to 12 ka BP have the grain size characteristics of aeolian sand, and indicates an arid sedimentary environment. Apart from sand, there are two clay layers in this section. They respectively deposited in 62 ka BP and 28 ka BP and indicate two periods of relative humid sdeimentary environment. All the sediments deposited from 12 ka BP to now are sand. The sand deposited during the period from 6 ka BP to 7 ka BP have the grain size characteristics of hydromorphic sand. The content of SiO 2 in sand is higher than in clay, while the content of other oxides in sand are lower than in clay. Only the sand samples deposited during the period from 6 ka BP to 7 ka BP have the different contents of oxides compared to other sand samples. The geochemical characteristis of these sand samples indicate a relative humid sedimentary environment druing the period from 7 ka BP to 8 ka BP The miniature structure of the granite sand surface also indicate its sedimentary environment. For example, the surfaces of granite sand deposited during the period from 6 ka BP to 7 ka BP have more SiO 2 sediment than in the granite sand deposited in other periods. Formed by water, this miniature structure indicates a relative humid period of sedimentary environment. The surfaces of granite sand deposited in other periods have granulated structure, and indicate a windy sedimentary environment.From the words above, a sequence about climate environmental changes in this area since 80 ka BP can be set up. During the period from 80 ka BP to 12 ka BP, the climate was colder and humider than that of today, and this area experienced two humid stages: one occurred 62 ka BP, another occurred about 28 ka BP since 12 ka BP, it has been generally warm and arid, but a humid stage ocurred during the period from 6 ka BP to 7 ka BP