青藏高原扎布耶盐湖晚全新世气候环境演化

Late Holocene climatic and environmental changes inferred from multi-proxies from Zabuye Saline Lake in Tibet

青藏高原晚全新世气候变化具有不稳定性。在高原中部扎布耶盐湖边缘取得158．5cm沉积物，通过年代、孢粉、介形虫、粘土矿物、地球化学等多种环境指标，给出了湖区3．8cal．kaBP以来的气候环境演化。孢粉中草本花粉占绝对优势，其中又以蒿属为主，植被类型为水分条件稍好些的半荒漠化草原。粘土矿物主要是伊利石和绿泥石，伊／蒙混层矿物少量，说明湖区风化作用主要是物理风化。（ca＋Mg）／CO3^2- 摩尔比值为0．22～0．96，小于1，CO3^2- 与Na^＋结合形成大量钠碳酸盐矿物如单斜钠钙石、氯碳钠镁石、水碱等。硼砂的出现说明湖区沉积环境稳定，但3．8～1．99cal．kaBP硼等元素和碳酸盐含量变化幅度较大，湖区气候寒冷干燥，但冷暖干湿波动频繁。3．4～3．34cal．kaBP介形虫壳大多破碎，说明此阶段水动力条件强，水体不稳定。1．99cal．kaBP至今，气候相对温暖潮湿，波动较少。太阳辐射和西南季风强度的变化是造成气候变化的主要原因。冰川冻土对寒冷气候的放大作用也是湖区气候变化的一个重要原因。

Holocence paleoclimate reflected from the records available in the Tibetan Plateau was unsteady. Based on the 14C chronology and multi-proxies（pollen, ostracode, clay minerals and geochemistry）from a 158.5 cm-core at the margin of Zabuye Saline l.ake in the central Tibetan Plateau, this paper presented a record of climatic and en- vironmental change during 3.8 -0 cal. ka BP. Vegetation of semi-arid steppe was distributed in the area with the dominant herbs in pollen and dominant Artemisia in herbs. In clay minerals illite and chlorite were dominant indicating dominant physical weathering in the region. Because of many Na-minerals such as gaylussite, northupite, thermonatrite and so on, the mole value of（Ca ＋ Mg）/CO2^3- was less than 1 and ranged from 0.22 to 0.96. Since salt minerals mainly depended on precipitation and temperature, the paper interpreted borax deposited in rather sta- ble climate and other salt minerals as the result of dry and cold climate and environment in Late Holocene, and the changes of carbonate content and elements as the result of frequent variations of climate and environment during 3.8 - 1.99 cal. ka BP. The fragmentations of ostracodes suggested a disturbed water situation during 3.4 - 3.34 cal. ka BP. The stable climate in 1.99 - 0 cal. ka BP was warmer and wetter than the last stage in the area experienced by the stable curves of carbonate contents, elements and pollen. The data shown that the fluctuations witb high am- plitude and frequency were mainly due to the variations of solar radiation and southwest monsoon, however the magnification effect of glacial and frozen earth to cold climate was another reason.