| 青藏铁路风火山段晚第四纪断裂活动分析 |
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| 引用本文： | 吴中海,吴珍汉,韩金良,张永双,胡道功,江万.青藏铁路风火山段晚第四纪断裂活动分析[J].现代地质,2005,19(2):181-188. |
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| 作者姓名： | 吴中海 吴珍汉 韩金良 张永双 胡道功 江万 |
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| 作者单位： | 中国地质科学院,地质力学研究所,北京,100081 |
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| 基金项目： | 中国地质调查局“青藏铁路沿线活动断层调查与地应力测量”项目 (1212010340302)。 |
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| 摘 要： | 地表地质调查发现, 第四纪期间在风火山逆冲—褶皱构造带以发生近东西向的伸展变形为特征。在该构造带中形成切割早期近东西向挤压变形构造带、指示近东西向伸展变形、整体沿北60°东向展布的二道沟断陷盆地。断裂活动的地质、地貌证据表明, 控制该盆地晚第四纪断陷的主边界断裂位于其北缘, 是一条断续延伸达24km左右、可能兼具左旋走滑性质的正断层。根据该区晚第四纪沉积物的分布和时代, 并对断裂所错动的晚第四纪地质—地貌体进行初步的年代学分析, 可以初步断定该断裂的晚第四纪垂直活动速率应该介于0 2~0 4mm/a之间。
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| 关 键 词： | 青藏高原 风火山 第四纪 伸展变形 活动断层 |
| 文章编号： | 1000-8527(2005)02-0181-08 |
| 修稿时间： | 2005年3月10日 |
The Late Quaternary Normal Faulting of Fenghuo Shan Thrust-Folds Belt in Central Qinghai-Tibet Plateau |
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| WU Zhong-hai,WU Zhen-han,HAN Jin-liang,ZHANG Yong-shuang,HU Dao-gong,JIANG Wan.The Late Quaternary Normal Faulting of Fenghuo Shan Thrust-Folds Belt in Central Qinghai-Tibet Plateau[J].Geoscience——Journal of Graduate School,China University of Geosciences,2005,19(2):181-188. |
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| Authors: | WU Zhong-hai WU Zhen-han HAN Jin-liang ZHANG Yong-shuang HU Dao-gong JIANG Wan |
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| Abstract: | In the central Qinghai-Tibet Plateau, there is a NE trending and S shaped graben called Erdaogou basin The graben, about 25 km long and about 2 km wide, cuts the east west trending Fenghuo Shan thrust folds belt which had been formed during Tertiary or from Late Cretaceous to Palaeogene The basin floor is covered by Late Quaternary deposits The graben is apparently asymmetric with the main boundary fault along its northern margin Many phenomena indicate the active normal faulting with the component of left lateral strike slip along the fault zones striking NE60°-90° and dipping 50°-80° to the south Along the footwall of fault, there is a prominent triangular facet, which is 200-300 m above the surface of piedmont plain At the base of triangular facets, faulting is pressed by south east facing fault scarps cutting fluvial fans and travertine platform The well preserved fault scarps offset vertically the fluvial fans about 1 5 m and 4 5±1 m formed during Holocene, and Late Pleistocene respectively and maybe offset left lateral the fluvial fans 8 10 m formed during Late Pleistocene Age results of U series and thermo luminescence (TL) indicate that offsets of the Holocene and Late Pleistocene fluvial fans represent the fault throws since 5-6 ka B P and 34-16 ka B P respectively These suggest that the average vertical slip rate is 0 28±0 06 mm/a and the left lateral strike slip rate is 0 5-0 8 mm/a along the faults at north side of Erdaogou graben This corresponds to a “spreading” rate of 0 1-0 2 mm/a across Erdaogou graben The relief across the normal fault indicate that the minimum cumulative displacement on fault maybe is about 500 m Based on the minimum cumulative throws and average slip rate of fault, the initiation age of the normal faulting may be no younger than 2 3 Ma The new data from Erdaogou graben are similar to those from Shuang Hu graben and Wen Quan graben in central Qiangtang block and demonstrate that the rate of Late Quaternary extension in central part of the Qinghai Tibet Plateau is roughly an order of magnitude lower than in southern Tibet The lower slip rate of normal faults is also coincide with less prominent morphologic expressions of grabens or rifts in central Tibet, less continuous and shorter than those in southern Tibet Based on the slip magnitude of fault in central Tibet, the cumulative extensional rate perhaps did not exceed about 3 mm/a across the Qiangtang block during Late Quaternary |
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| Keywords: | Qinghai Tibet Plateau Fenghuo Shan Quaternary extensional deformation active fault |
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