| 青藏高原的冰碛层与环境 |
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| 引用本文： | 吴锡浩,李永昭.青藏高原的冰碛层与环境[J].第四纪研究,1990,10(2):146-158. |
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| 作者姓名： | 吴锡浩 李永昭 |
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| 作者单位： | 地质矿产部地质力学研究所，成都地质学院 |
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| 摘 要： | 最近3.4 Ma青藏高原尤其是南部可见七套冰碛层（自新至老M0—M6）,M1—M6上对应发育古土壤MS0—MS5,除M0和MS0外,形成于六次冰期和五次间冰期。通过与黄土高原对比,除M6外,可用黄土-古土壤序列确定它们的年代。分别以M0—M5上的古土壤为标志,算出高原于1.56—1.23 Ma B.P.、平均高程约2500m开始整体隆升、经历时约0.4 Ma的三个阶段,在0.075 MaB.P.已升到4300m,上升速率从2.0、2.5、2.8增至8.7 mm/a,导致冰期雪线升高,冰进范围缩小。冰期和季风气候变化及阶段性隆升共同决定了高原的环境变迁。
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| 关 键 词： | 青藏高原 冰碛层 古土壤 高原隆升 环境变迁 |
MORAINES AND ENVIRONMENTS IN QINGHAI-XIZANG PLATEAU |
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| Institution: | 1. Institute of Geomechanics, Ministry of Geology and Mineral Resources;
2. Chengdu College of Geology |
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| Abstract: | There totally exist seven series of the horizons of moraines formed by the palaeoglaciations in Qinghai-Xizang Plateau, especially in its southern part. According to the classical subdivision, the lst-6th moraines （M1—M6） have been deposited respectively in the lst-6th glacial stages in reverse order and one （M0） in the Postglacial during the last 3.4 Ma. Usually, M6 related to the fluviolacustrine formations in the early of Gauss Chron; M5 distributed over the plateau planes of denudation; M4 lied on the wide-valleys which have shallow downcutting for the denudation planes; M3 occurred on the low shoulders of the deep downcutting valleys, M2 developed in the valleys which cut the tables on terraces existing M5, M4 and M3; M1 just emerged in the middle-upper reaches of the U-valley having M2; and Mo all can be seen in the front of the present glaciers. However, the palaeosols or weathered crusts （MS1-MS5） have been developed correspondingly on M2-M6 in the 1st-5th interglacial stages in reverse order, except the last palaeosol （MS0） developing on M1 in the optimum of the Postglacial. In the southern part of the plateau, it has been proved that MS0 is the burozem, MS1, the drab soil; MS2-MS4, the cinnamon red soils; and MS5, the red weathered crust.On the basis of the magnetostratigraphical data related to the horizons of moraines in Qinghai-Xizang Plateau, and their correlation with the sequences of stratigraphy and chronology of the loess-palaeosol in Loess Plateau, it can be determined approximately that their upper most boundary ages of the moraines and palaeosols or the glacial and interglacial stages are as follows: M6 3.0 Ma B. P, MS5 2.35 Ma B. P., M5 1.56 Ma B. P., MS4 1.23 Ma B. P., M4 0.96 Ma B. P., MS3 0.61 Ma B. P., MS2 0.48 Ma B. P., M2 0.13 Ma B. P., MS1 0.075 Ma B. P., MS0 0.005 Ma B. P. Generally speaking, the horizons of the moraines in Qinghai-Xizang Plateau correspond to that of the weak weathered loess in Loess Plateau, and the horizons of palaeosols on the moraines compare with the drab soils intercalated in the loess layers showing the stronger podogenesis. This reflects the foundamental identity of the neotectonic movements between two plateaus.The quantitative or semi-quantitative studie of the uplift periods, extents and rates of the plateau have been made by taking the palaeosol on the moraines for the main markings. It can be shown that the plateau plain in Qinghai-Xizang area formed by the processes of denudation and aggradation during the time from 4.5 Ma B. P. to 1.53 Ma B. P. During the period of 1.56—1.23 Ma B. P. and when the mean altitude was approximately 2 500 m the plateau began to uplift as a whole. Through three periods which lasted about 0.4 Ma, the plateau plain reaches up to about 4 300 m in mean altitude in the age of 0075 Ma B. P., and the accumulated uplift rates gradually increased from 2.0 to 2.8 mm/a, and then speeded up to 8.7 mm/a, and the instantaneous uplift rate was about 30 mm/a and the uplifting was about 150 m high during the last 0.005 Ma B. P.Since the 3rd interglacial stage （0.96—0.83 Ma B. P.） from the last one the marine climate in the southern part of the plateau has been weakened step by step. Especially after the time of 0.48 Ma B. P. when the mean altitude of the plateau reached about 4 000 m, a sudden change of the general circulation of atmosphere took place. Resulting in further lift in the altitudes of snowlines and reduction in the scale of glaciers in the glacial stages. In a word, the environmental changes of the Qinghai-Xizang Plateau have been jointly controlled by the global glacial climate, the regional monsoon climate and the uplift effect of climate its own. |
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