| 摘要: |
| 于1993年在青藏高原东北部若尔盖盆地沉积中心钻取一长310m的湖泊岩芯（RM孔），对其上部31m的湖泊沉积物进行了年代测定以及自生碳酸盐氧同位素、有机碳氮分析，重建了14万a来的古气候演化过程,基本上可以区分出5个阶段。结果表明，5阶段（140–80kaB.P.）气候温暖湿润,内部又可区分出5a–5e；4阶段（80–60kaB.P.）气候以冷干为主；3阶段（60–30kaB.P.）为相对温湿期，降水丰富，流域径流量较大；30kaB.P.以来若尔盖古湖逐渐被黄河支流切开，各项代用指标的环境指示意义不明显。同时对比邻区陆相记录，探讨了高原东北部不同阶段气候演化的过程和细节。 |
| 关键词: 青藏高原 古气候 若尔盖盆地RM孔 自生碳酸盐氧同位素 有机碳氮比值 |
| DOI： |
| 分类号: |
| 基金项目:中国科学院重大资助项目，KZ951-Al-402号 |
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| PALAEOCLIMATE OF NORTHEASTERN QINGHAI-XIZANG(Tibet) PLATEAU SINGCE LAST INTERGLACIATION—A CASE STUDY FROM CORE RM OF THE ZOIGE BASIN |
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XUE Bin, WANG Su-min, WU Jing-lu, QIAN Jun-long
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Nanjing Institute of Geography and Limnology, The Chinese Academy of Sciences, Nanjing, 210008
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| Abstract: |
| Core RM, 310m in length, collected from the central part of the Zoige Basin, eastern Tibetan Plateau, was analyzed. The upper 31m provides continuous palaeoclimatic information during the past 140ka, which is reconstructed on the basis of stable oxygen isotope analyses of authigenic carbonate, organic carbon and nitrogen analysis. The δ18O of authigenic carbonate is a good indicator for the palaeotemperature, whereas the variation in the C/N ratio corresponds with the percentage of the autothonous to allothonous organic matter in the lake sediments, reflecting the changes of the runoff and palaeo-precipitation conditions, therefore, the analytical results have revealed changes in the palaeoenvironmental condition, induced by climate changes and / or local hydrological factors.
Five stages are identified for the palaeoclimate in the past 140ka and can be compared with the oxygen isotope curve of deep sea cores. Stage 5 (140–80ka B.P.) is equivalent to the Last Interglaciation, in which 5 substages (5a–5e) can be identified. 5e is the warmest, 5d is the coldest and 5a has the best effective moisture within stage 5. Substage 5e can be identified in to further 5 little stages, and this kind of geological phenomena has been shown in a lot of records, e.g, magnetic susceptibility records from adjacent areas, pollen records from Europe, δ18O records from deep sea cores and Greenling ice cores, which has been speculated to be a result from the change in the summer solar insolation. Stage 4 is characterized by cold/dry climate. Stage 3 (60–30ka B.P.) is a relatively warm and wet period, characterized by abundant precipitation. The Zoige Basin was cut through by the Yellow River since 30 ka B.P. and the proxies are of no use in terms of the identification of the palaeoclimate. The peak value of C/N in Core RM of this period suggests intensified river processes, and an increase in precipitation over the drainage area. The special characteristics of stage 3 in Qinghai-Xizang Plateau should be considered in the future Quaternary studies. Comparative study has been undertaken for the Core RM records with the other records of adjacent areas and in the world, and the climatic evolution and its characteristics in different stages of the northeastern Qingzang Plateau have been discussed. |
| Key words: Qinghai-Xizang Plateau, Palaeoclimate, Core RM from Zoige Basin, Oxygen isotope of authigenic carbonate, C/N ratio |
