西藏错那—沃卡裂谷带中段邛多江地堑晚新生代正断层作用

吴中海; 张永双; 胡道功; 赵希涛; 叶培盛

西藏错那—沃卡裂谷带中段邛多江地堑晚新生代正断层作用

1.
中国地质科学院地质力学研究所, 北京 100081
2.
中国科学院地质与地球物理研究所, 北京 100029

基金项目:

中国地质调查局项目《滇藏铁路沿线地壳稳定性调查评价》 1212010541404

国家自然科学基金项目 40501006

科技部国际合作项目 2006DFA21320

详细信息

作者简介:
吴中海(1974-), 男, 博士, 副研究员, 主要从事第四纪地质与活动构造研究。E-mail:wzhly@sina.com

中图分类号: P542⁺.32;P542⁺.31
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出版历程
- 收稿日期: 2007-04-15
- 刊出日期: 2007-12-01

LATE CENOZOIC NORMAL FAULTING OF THE QUNGDO'GYANG GRABEN IN THE CENTRAL SEGMENT OF THE CONA-OIGA RIFT, SOUTHEASTERN TIBET

1.
Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China
2.
Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China

摘要

摘要: 遥感解译和地表调查结果显示, 位于西藏曲松县境内的邛多江盆地构成了藏南近南北向裂谷带最东端的错那-沃卡裂谷的中段。它是在该区近东西向逆冲构造带停止活动之后, 上地壳沿N108～115°E方向发生引张作用所形成的第四纪半地堑式断陷盆地。控制晚第四纪盆地发育的主边界正断裂带位于盆地西缘, 总体呈NNE走向, 向东倾, 长40 km左右。断裂活动位移测量和年代学测试结果表明, 该边界正断层带在5Ma左右就已开始活动, 总累计垂直位移量至少为2.6～2.8 km, 最小长期平均垂直活动速率约0.5mm/a。末次冰期盛冰期以来, 该断裂平均活动速率的最合理的估计值为1.2 ±0.6 mm/a。
- 西藏 /
- 第四纪 /
- 错那-沃卡裂谷 /
- 邛多江地堑 /
- 正断层作用
Abstract: The Qungdo'gyang graben in Qusum County, Tibet, belongs to the central segment of the NNE-trending Cona-Oiga (or Cona-Sangri)rift zone, which is the only rift located at the easternmost end of the nearly N-S-trending Yadong-Gulu rift zone in southern Tibet.It is a Quaternary semi-graben downfaulted basin formed by extension of the upper crust occurring in the N108-115°E direction after the nearly E-W-trending thrust zone in the study area ceased its activity.The main boundary normal fault controlling the development of the late Quaternary basin is located at the western margin of the basin.It generally strikes NNE and dips E with a length of ～40 km.Displacement measurements and isotopic dating indicate that:this boundary normal fault began activity at ～5 Ma BP; the total cumulative vertical displacement ranged from 2.6 to 2.8 km; and the minimum long-term average throw rate was ～0.5 mm/a.The most rational estimate of the average throw rate since the last maximum glaciation (MIS2)of the fault is 1.2±0.6 mm/a.
- Tibet /
- Quaternary /
- Cona-Oiga rift /
- Qungdo'gyang graben /
- normal faulting

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图 1 邛多江地堑及其邻区的ETM遥感影像、研究区位置和盆地拉伸方向判别图

Figure 1. ETM remote sensing image interpretation of the Qungdo'gyang graben and its adjacent areas, location of the study area and extensional orientation of the graben

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图 2 邛多江盆地地质—地形横剖面

Figure 2. Geological-topographical cross-section of the Qingduojiang graben

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图 3 邛多江盆地20道班西北侧山前的断层三角面地貌(镜向:西南)

Figure 3. Fault triangle facets along the front of a mountain NW of maintenance station 20 in the Qungdo'gyang graben (looking toward SW)

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图 4 山前正断层上的断层摩擦面及其上的断层擦痕(镜向:西; 图 1中的位置Ⅰ)

Figure 4. Friction surface of a piedmont normal fault and striations on it (looking toward W; localityⅠ in Fig. 1)

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图 5 山前正断层垂直错动末次盛冰期冰川侧碛垄(镜向:西南; 图 1中的位置Ⅲ)

Figure 5. Vertical offset of the glacial lateral moraine ridge fo rmed in the last maximum glaciation by the piedmont normal fault (looking toward SW; locality Ⅲ in Fig. 1)

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图 6 邛多江西侧山前错动全新世地貌体的断层崖剖面

Figure 6. Topographic sections of Holocene fault scarps offset along the western side of the Qungdo'gyang graben

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图 7 邛多江西侧山前错动晚更新世地貌体的断层崖剖面

Figure 7. Topographic section of late Pleistocene fault scarps offset along the western side of the Qungdo'gyang graben

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图 8 邛多江—沃卡盆地主边界断裂带晚第四纪垂直活动速率分布图

Figure 8. Distribution of late Quaternary throw rates of the main boundary fault in the Qungdo'gyang-Oiga basin

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表 1 邛多江盆地晚第四纪沉积物、断层岩的年代学测试结果和断裂带垂直活动速率估算值

Table 1. TL dating of late Quaternary deposits and fault rock in the Qungdo'gyang basin and estimated vertical throw rates of the fault zone

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