青藏高原日土地区全新世中期以来介形类和孢粉组合变化及其古环境意义

Paleoenvironment of Ostracods and Pollen Record since Middle Holocene in Rutog Area,Tibet

本文综合分析了青藏高原日土地区RT-1剖面中介形类和孢粉种类组合的变化,结合三个光释光测年数据,探讨了该地区6510aBP以来古环境、古气候的演变。分析表明:日土地区在全新世中期曾有一个温暖湿润期(6170～5540aBP),之后气候环境频繁波动,逐渐趋向冷干,接近现代气候环境。43～30kaBP期间在鲁玛江冬错和班公错之间的古泛湖解体后,日土地区因为地势低洼,而在当时成为一个封闭的水体,并且一度与相邻的班公错相连。当时的水体一直持续到全新世,在经历了全新世暖湿期时短暂的湖涨期以后,逐渐萎缩,至约1570～1380aBP最终干涸消失,形成现今地貌。研究表明全新世大暖期在本地区也有反映,但是在高原深部,大暖期更为短暂,气候波动更为频繁。

Based on OSL dating,this paper reports the paleoenvironmental and climatic evolution in Rutog area,Tibet,since 6510 a BP.Ostracods and pollen record indicated a warm and wet period（6170~5540 a BP）in middle Holocene in Rutog area.Climate varied frequently after this period and tended to be cold and dry,which was similar to modern climate.After disassembly of the 43~30 ka BP paleolake between Lumajiangdong Co and Bangong Co,the topographic low Rutog area became an enclosed lake basin,and connected to the adjacent Bangong Co for some time.After a short time of enlargement during warm-wet period in Holocene,the lake shrinked and eventually dried up during 1570~1380 a BP,similar to the modern environment.The Megathermal in Holocene became shorter and climate changed more frequently during this period in the deep part of Qinghai-Tibetan Plateau.