【摘要】 文章讨论了末次冰消开始时期青藏高原南部普莫雍错湖芯沉积反映的环境暖湿化以及原因。通过对现代湖泊和周边河流水文状况调查,发现流域内发育众多冰川,冰川融水构成维持湖面稳定的重要来源;湖面以及湖泊沉积环境的变化与冰川融水以及相应的温度改变具有密切的联系。利用湖泊沉积岩芯PM-1孔,通过加速器14C测年和粒度、元素、碳酸盐含量、总有机碳以及有机碳同位素、总氮、分子标志化合物、孢粉等环境指标的分析,发现在16.4~15.4cal.kaB.P.有大量流水进入湖泊,使湖面扩大,湖水加深;流域地表产生大量有机碎屑,并被流水带入湖泊进行沉积;流域内的喜湿植被得以发展。该时段湖泊扩张、陆源植被发展的原因一方面得益于冰期过后气候向温暖湿润方向转化,另一方面温度上升带来大量冰川融水则可能具有更加重要的影响,对于深入理解当前青藏高原冰川普遍退缩和一些湖泊的水面上涨具有重要的参考价值。更多还原

【Abstract】 This paper revealed a warm and humid environment during the initial stage of the last deglacial period in the Pumoyum Co Lake of the southern Tibet and analyzed several possible reasons. Investigation of lake hydrological conditions has indicated that there were many glaciers,of which the melting water constituted significant supply for the lake. Variations of lake water level and lake sedimentary environment have close relationship with the glacier melting water and the temperature changing background. By using HD-27 single frequency echo-sounder and HD8500 GPS receiver,the isobath of the lake were surveyed and sedimentary transportation processes were analyzed. In 2001,the authors drilled a PISTON core (PM-1) at 46.5m water depth site in the east part of the lake,which was far away from terrestrial sediments source. 4 AMS 14 C dating data,12922±49aB.P.,13435±48aB.P.,14642±49aB.P.,and 14819±50aB.P. were obtained from vegetation debris at the depths of 212cm,300cm,370cm,and 380cm in the lower part of the core and the ages were also calibrated as 15410±250aB.P.,16430±240aB.P.,17550±270aB.P.,and 17740±280aB.P. by CALIB 3.0. Environmental proxies of grain size,trace elements,CaCO_ 3 ,Total Organic Carbon (TOC),C/N,δ 13 C_ org. ,biomarkers as well as pollen and spores were analyzed. During 16.4～15.4 cal.kaB.P.,increased grain-size implied that there were more “coarse” particles transported into the lake due to surface inflow enhancing. CaCO_ 3 and Fe/Mn data indicated that the lake water volume was enlarged and lake water level increased. No matter where (the internal or external) TOC source was from,the increased TOC in lake sediments suggested that the temperature rising resulted in lake zooplankton or terrestrial vegetation development. However,C/N and biomarkers of HMFA and HMA showed that more terrestrial organic materials were deposited in the sediments. On the one hand,it was an evidence for a developed terrestrial vegetation,while on the other hand the terrestrial vegetation debris were more easily transported into the lake due to more surface water inflow. Pollen and spore assemblages in this section also suggested that,humid-adaptive vegetations (Gramineae and Cyperaceae) developed while dry-adaptive vegetation (Chenopodiaceae) decreased. The lake enlargement and terrestrial vegetations development were due to plenty of glacier melting water supply and a warmer and more humid climate after the end of the Last Glacial Maximum (LGM).更多还原