| 班戈错晚第四纪湖泊发育、湖面变化与藏北高原东南部末次大湖期湖泊演化 |
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| 关键词:North Tibetan Plateau Bankog Co Late Quaternary last great lake period lake evolution denivellation |
| 基金项目:中国地质调查局“青藏高原及其周边地区第四纪湖泊环境演变序列和气候变迁”项目(编号: 20313000065) |
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| Late Quaternary Lake Development and Denivellation of Bankog Co as well as Lake Evolution of Southeastern North Tibetan Plateau during the Last Great Lake Period |
| The Bankog Co is a small lake separated from the eastern part of the Silin Co during the late Late Pleistocene. From May to July, 2003, the authors made a detailed investigation of geomorphology and Quaternary geology along the bank of Bankog Co, which included the leveling survey of lake level levations, the measurement of lake terrace heights along six profiles and the collection of lake deposit samples for U-series dating. The study results show that there are 6 level terraces (T1-T6) along the Bankok Co. Except that T1 was formed after separation from the Silin Co, the heights above the lake level and U-series ages of the other terraces are 11.8~29.8 m and 10.9±1.9~14.8±1.1 ka BP for T2, 32.4~59.8 m and 31.1±2.5 ka BP for T3, 52.4~83.7 m and 36.3±3.1~38.8±3.7 ka BP for T4, 82.2~112.9 m and 35.1±2.9 ka BP for T5, and 121.8~139.8 m and 47.9±3.8 ka BP for T6, respectively. Correspondingly, for the heights of individual terraces of the Silin Co, 9 meters should be subtracted from the heights of the Bankok Co terraces, which is the lake level height difference between the two lakes. The 6 level terraces of the Silin Co and the Bankok Co can be well correlated in the formation time with the 6 level terraces of the Nam Co. In addition, some high lake deposits of the early and middle Late Pleistocene may be found in southeastern North Tibetan Plateau. Therefore, the lake evolution of southeastern North Tibetan Plateau since MIS 5 of the last great lake period can be divided into two stages: the Qiangtang great lake stage of 125~30 ka BP, MIS 5e~MIS 3 and the North Tibetan lake group stage during 30~0 ka BP, MIS 2~1. The former can be further divided into four substages: the Qiangtang great lake substage of 125~96 ka BP, MIS 5e~c, the east Qiangtang lake substage of 96~75ka BP, MIS 5b~a, the retreated great lake substage of 75~37 ka BP, MIS 4~MIS 3a and the remnant great lake substage of 37~30 ka BP, MIS 3a. The latter can be further divided into two substages: the lake salting substage of 30~10 ka BP, MIS 2 and the saline lake forming substage of 10~0 ka BP, MIS 1. The study results also show that, from 1959 to 2003, the lake surface of the Bankog Co was overall rising, reaching up to 1.75 m, although from 1959 to 1973 or a little later, there occurred a process of first falling, then rising and again slight falling, with a fall of 0.25 m, and an accompanied contraction of the lake area. |
| ZHAO Xi-tao,ZHAO Yuan-yi,ZHENG Mian-ping,MA Zhi-bang,CAO Jian-ke,LI Ming-hui.2011.Late Quaternary Lake Development and Denivellation of Bankog Co as well as Lake Evolution of Southeastern North Tibetan Plateau during the Last Great Lake Period[J].Acta Geoscientica Sinica,32(1):13-26. |
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