青藏高原东缘叠溪海盆地40～30kaBP高分辨率快速气候变化记录

High resolution rapid climate change records of lacustrine deposits of Diexi Basin in the eastern margin of Qinghai-Tibet Plateau,40-30 ka BP

对岷江上游地区叠溪古堰塞湖底部沉积物进行AMS14C定年,得到其沉积时间起始时间约为40.5kaBP。通过沉积物粒度特征的研究得知,粒度指标可以反映降水量变化进而反映气候干湿变化,此外,粒度均值曲线与格陵兰冰心(GISP2)及南京葫芦洞石笋氧同位素曲线的显著相似性说明,粒度特征对全球性气候变化有响应,可以反映气候的冷暖变化。由此,研究区古气候演变可以划分为3个阶段:阶段Ⅰ(40.5～33.4kaBP)气候冷干,阶段Ⅱ(33.4～31.7kaBP)气候暖湿,阶段Ⅲ(31.7～31.1kaBP)气候较暖湿。而粒度均值曲线与冰心及石笋氧同位素曲线的差异,一方面可能是由于地理位置的差异,另一方面可能与当时太阳辐射变化情况以及季风作用有关。

The deposition of Diexi ancient barrier lake in the upper reaches of Minjiang River was re-dated by AMS14C dating,and the result shows it started at 40.5 ka BP.The grain-size proxy index can reflect the precipitation and thus the climate dry-wet change.In addition,the obvious comparability between the mean grain-size curve of Diexi Section lacustrine deposits and the δ18O of Greenland ice core and Nanjing Hulu Cave stalagmites shows that the grain-size proxy index could respond to the global climate change,and reflect the chilling and warming.Thus the paleoclimate evolution in the studied area could be divided into three stages：40.5-33.4 ka BP,cold and dry;33.4-31.7 ka BP,warm and humid;31.7-31.1 ka BP,warm and humid,but not as much as the previous stage.The differences between these curves could be interpreted by the variation in location,insolation and monsoon.