西藏玛旁雍错沉积揭示的晚冰期以来环境变化

玛旁雍错位于青藏高原西南部,是研究印度季风演化的理想地区之一。利用活塞采样器在玛旁雍错75 m水深处获取了一根4.69 m长岩芯,利用^210Pb和AMS^14C测年确定了岩芯的年代,根据元素含量(XRF扫描)、总有机碳(TOC)、总无机碳(TIC)和总氮(TN)等代用指标,重建了该地区14 cal.ka B.P.以来气候环境变化。结果显示,冰消期(14~12 cal.ka B.P.),TOC和TIC含量变化显示了湖区环境整体上较为暖湿;12.0~11.4 cal.ka B.P.,径流明显减弱,可能是新仙女木事件的反映;早中全新世(11.4~3.4 cal.ka B.P.),湖区环境整体上以暖湿为主,气候有所波动,出现了两次冷事件(10.2~9.8 cal.ka B.P.和8.2 cal.ka B.P.左右),7.4~6.6 cal.ka B.P.,出现了一个暖时期;晚全新世(3.4~0 cal.ka B.P.),湖区环境整体上趋向于干旱化,并伴有两次相对湿润时期(2.6~2.0 cal.ka B.P.和1.4~1.0 cal.ka B.P.)。玛旁雍错环境变化表明,晚冰期以来(14.0~3.4 cal.ka B.P.),受到太阳辐射的影响,印度季风带来的降水以及冰川融水较多,湖区环境较为湿润,整体上有利于内源生物的生存;晚全新世(3.4~0 cal.ka B.P.),北半球夏季太阳辐射量减少,印度季风减弱,径流减弱,湖区环境朝干旱化方向发展。

Environmental changes reflected by core sediments since late glacial in Mapam Yumco,southwest Tibet of China

Mapam Yumco, located in the southwest of Tibetan Plateau, is one of the ideal areas to study the evolution of Indian monsoon. A 4.69 m long core was obtained at a depth of 75 m at Mapam Yumco using a piston sampler. The core age was determined by^210Pb and AMS^14C dating. According to the element content(XRF scanning), total organic carbon(TOC), total inorganic carbon(TIC) and total nitrogen(TN) et al, lake environment changes since 14 cal.ka B. P. were reconstructed. The results showed that during the deglaciation period(14~12 cal.ka B. P.), TOC and TIC showed that the lake environment was relatively warm and wet on the whole. 12.0~11.4 cal.ka B. P., runoff was significantly weakened under the influence of the YD event. In the Early and Middle Holocene(11.4~3.4 cal.ka B. P.), the overall environment of the lake area was still warm and humid, and the climate fluctuated. There were two cold events(10.2~9.8 cal.ka B. P. and about 8.2 cal.ka B. P.), and 7.4~6.6 cal.ka B. P., showing a warm period. In the Late Holocene(3.4~0 cal.ka B. P.), the lake environment as a whole tended to be arid, accompanied by two periods of relative humidity(2.6~2.0 cal.ka B. P. and 1.4~1.0 cal.ka B. P.). The changes in the environment of Mapam Yumco show that since the late glacial period(14.0~3.4 cal.ka B. P.), the Indian monsoon brought more precipitation and the glacier melt water had increased under the influence of solar radiation, and the environment in the lake area is relatively humid, which is conducive to the survival of endogenous organisms on the whole. In the Late Holocene(3.4~0 cal.ka B. P.), the solar radiation in the Northern Hemisphere decreased in the summer, the Indian monsoon weakened and lake environment developed towards aridification.