西藏台错沉积记录与更新世晚期-全新世气候变化

Sedimentary Records and the late Pleistocene-Holocene climatic changes in Tai Co,Tibet(Xizang)

西藏西部台错湖T1阶地的两个剖面沉积中,除下部10余厘米含炭化植物和50～70cm处为暗色碳酸盐粘土及粘土外,中、上部全系粘土碳酸盐层,含丰富的介形类和轮藻类。据碳酸盐、介形类、轮藻类的碳、氧稳定同位素值与微体古生物群落生态特征等提供的环境气候变化指标,指示该区距今41.4～4.5 ka BP间气候变化为:在41.4～26.2kaBP气候较湿润;26.2～25.5 ka BP偏暖稍干;25.5～22.5 ka BP气候暖湿;22.5～21.0 ka BP气候偏冷湿;20.5～17.5 ka BP气候骤冷、偏湿,反映本区处于末次冰期盛冰期;17.5～16.0kaBP偏冷偏干;16.0～11.8kaBP气候偏暖湿,为全球间歇性暖事件的响应;11.8～10.4 ka BP气候较冷干,大致相当于新仙女木期,10.4 ka BP气温开始回升;10.4～9.4 ka BP气候偏暖湿;9.4～8.5kaBP气候呈现短暂暖湿颤动;8.5～7.9 ka BP气候偏干冷,为冰后期强烈降温偏干事件;7.8～6.3kaBP气候偏暖湿;6.3～4.5 kaB P气候趋向冷干,4.5 ka BP记录了晚更新世晚期以来最大的干燥期。

Two sections were surveyed in Tai Co （lake）, western Tibet. Their middle and upper parts consist all of clay carbonate and contain abundant gastropods, ostracods and charophytes, while in their lower part the 10余, cm interval contains carbonized plants and the 50-70 cm interval is composed of dark-colored carbonate clay and clay. According to the carbon and oxygen stable isotope values of carbonate, ostraeods and charophytes and ecological features of micro-paleocommunities, the climatic changes at 41.4-4.5 ka BP were as follows, wet at 41.4-26.2 ka BP; slightly warm-slightly dry at 26.2-25.5 ka BP; warm-wet at 25.5-22.5 ka BP; slightly cold-wet at 22.5-21.0 ka BP;and abruptly cold and slightly wet at 20.5- 17.5 ka BP, reflecting that this area was in the Last Glacial Maximum, slightly cold-slightly dry at 17.5% 16.0 ka BP slightly warm-wet at 16. 0- 11. 8 ka BP1 and relatively cold-dry at 11. 8- 10. 4 ka BP, roughly equivalent to the Younger Dryas; began to become warmer at 10.4 ka BP~ slightly warm-wet at 10.4-9.4 ka BP1 showed short warm-wet oscillations at 9.4-8.5 ka BP; slightly dry-cold at 8.5-7.9 ka BP, representing a postgaeial strong temperature-falling and slightly dry event slightly warm-wet at 7.8 -6.3 ka BP; and tended to be dry-cold at 6.3-4.5 ka BP1 and the 4.5 ka BP witnessed the longest dry stage since the late part of the late Pleistocene.