摘要
西藏西部聂尔错古湖37/ZK7的钻孔剖面深10m,含丰富的介形类和轮藻类等微体水生生物化石。介形类数量多,但分异度低。频繁出现、含量较多的是Leucocythere mirabilis Kaufmann和Limnocythere dubiosa Daday,其他是为数不多的Limnocytherellina,Eucypris和Candona。轮藻类产出层位多,但其藏卵器保存不好,多系营养体碎片及卵膜。据介形类生态环境分析,结合剖面铀系测年和沉积物特征及相关地化背景值等,聂尔错古湖在近20,000—2,000年间的古环境变化大致情况如下:①距今20,000年前后,湖水较深,水温较低,水质微咸,气候较凉湿转暖湿。②约18,700—18,100a BP,湖水蒸发量较大,湖泊收缩,湖水逐渐变浅,含盐度增加,气候偏暖干。③约18,100—11,800a BP,气候冷湿、湖水较深,水温偏低,水质较淡,但是其间有多次气候波动,随着气候的波动,湖泊水体深度和水化学性质发生变化,显示湖区气候较冷湿与凉偏湿频繁交替,晚期凉偏干。④约11,800—10,000a BP,气候偏暖湿(11,800—11,000a BP)转冷干(11,000—10,000a BP),湖泊生态环境恶化,介形类数量急剧减少,应是对全球仙女木事件的响应。⑤10,000a BP进入全新世后,气候偏暖湿(10,000—8,700a BP,7,000—4,800a BP)间偏冷湿(8,700—7,000a BP);4,800—3,000a BP转为偏暖干(4,800—4,600a BP,4,400—4,300a BP,3,800—3,000a BP)与偏冷湿(4,600—4,400a BP,4,300—3,800a BP)交替;3,000—2,100a BP以冷干气候为主,湖泊趋于干涸。
The section of the 10-m-deep 37/ZK7 hole in Nyêr Co paleolake, western Tibet, contains abundant aquatic microfossils such as ostracods and charophytes. Of these, the ostracods are the most abundant group but have a low diversity. The ostracods that occur frequently and have a high abundance are Leucocythere mirabilis Kaufmann and Limnocythere dubiosa Daday, while others including Limnocytherellina, Eucypris and Candona that are of much less abundance. Charophytes occur in many horizons, but their oogonia are poorly preserved and what have been preserved are mostly the fragments of vegetal bodies and the membranes of ova. According to the analyses of the eco-environment of ostracods, combined with the U-series dating and sedimentary data of the section, as well as the relevant geochemical background values, the paleoenvironmental changes of the Nyêr Co Paleolake at 20000-2000 a BP were largely as follows. ① Around 20000 a BP, the lake water was relatively deep, the water temperature relatively low and the water quality slightly salty. The climate was relatively cool-wet and then became warm-wet. ② During 18700-18100 a BP, the lake water had a high evaporation quantity, so that the lake area shrank and the lake became shallow gradually. The salinity increased and the climate was slightly warm-dry. ③ During 18100-11800 a BP, the climate was cold-wet. The lake water was relatively deep, the water temperature slightly low and the water quality relatively tasteless.However, there were several climatic fluctuations and the lake depth and hydrochemical properties changed with climatic oscillations in this period, suggesting that the climate in the lake district was characterized by a repeated alternation of relatively cold-wet and cool-slightly wet and became cool-slightly dry at the late stage. ④ During 11800-10000 a BP, the climate became slightly warm-wet（11800-11000 a BP） and then became cold-dry（11000-10000 a BP）. The eco-environment of the lake deteriorated and the number of ostracods decreased abruptly, which should be the response to the global Dryas event in the study area. ⑤ At 10000 a BP in the Holocene, the climate was slightly warm-wet（10000-8700 a BP and 7000-4800 a BP）, with slightly a cold-wet climate （8700-7000 a BP）; during 4800-3000 a BP, the climate became alternately slightly warm-dry（4800-4600, 4400-4300 and 3800-3000 a BP） and slightly cold-wet（4600-4400 and 4300-3800 a BP）; and during 3000-2100 a BP, the climate was mainly cold-dry and by then the lakes had been nearly dried-up.
出处
《古地理学报》
CAS
CSCD
2007年第6期575-587,共13页
Journal of Palaeogeography：Chinese Edition
基金
国家自然科学基金重点项目(49833010
40531002)
中国地质调查局地调项目(200313000065)资助
关键词
西藏西部
聂尔错
微体古生物
介形类
环境及气候变化
western Tibet, Nyêr Co, micropaleontology, ostracod,environmental and climatic changes
作者简介
刘俊英，女，1939年生。中国地质科学院地质研究所研究员，1963年毕业于成都地质学院地质勘探系。长期从事地层古生物研究，现主要研究沉积环境与微体古生物。
