| 第四纪洞庭盆地澧县凹陷构造活动特征及动力学机制探讨 |
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| 关键词:Lixian sag faulted basin depressive basin dynamic mechanism Quaternary |
| 基金项目:中国地质调查局地质大调查项目(编号: 1212010610706)和国家自然科学基金项目(批准号: 40672206) |
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| Tectonic Activities and Dynamic Mechanisms of the Quaternary Lixian sag of Dongting Basin |
| Quaternary Lixian sag is a second-order tectonic unit in the northwestern part of the Dongting Basin. The authors studied the Quaternary sedimentary, geomorphic and tectonic characteristics of the Lixian sag and its adjacent areas based on near-surface survey and borehole data, and then probed into the tectonic dynamic mechanism. The Lixian sag is a triangle restricted by three normal faults located respectively along the south, northwest and northeast boundary. During Early Pleistocene-middle Middle Pleistocene, the normal faults moved violently, the sag subsided greatly, the sediments mainly composed of sand and gravel beds became increasingly thicker from the margin to the center of the sag, and local footwall evidently experienced strong subsidence. At the same time, the west and south periphery of the sag rose and the base terraces covered by alluvial deposits were formed. The sag and its peripheral areas rose as a whole since late Middle Pleistocene, when there occurred eastward tilt in northern Lixian sag and in south periphery, and small-sized folds were formed in the northern sag. These tectonic activities suggest that the Lixian sag was a faulted basin during Early Pleistocene-middle Middle Pleistocene and has become a depressive basin since late Middle Pleistocene. The authors hold that the tectonic activities during Early Pleistocene-middle Middle Pleistocene were related to mantle uplift: as the deep uplifting mantle heated the crust in Lixian sag, the ductile matter of the middle curst expanded and moved toward the periphery and then shrank by cooling, which brought about collapse and subsidence of the upper crust, and hence normal faults were formed on the margin of the subsided block. In addition, gravity isostasy might have played a part in the subsidence. The tectonic activities since late Middle Pleistocene were possibly related to the return of the earlier transported matter, the movement of the plate-scale material and the compression. |
| BAI Dao-yuan,LI Chang-an,WANG Xian-hui,MA Tie-qiu,PENG Yun-yi.2010.Tectonic Activities and Dynamic Mechanisms of the Quaternary Lixian sag of Dongting Basin[J].Acta Geoscientica Sinica,31(1):43-55. |
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