秦岭南缘大巴山褶皱-冲断推覆构造的特征

    Characteristics of the Dabashan fold-thrust nappe structure at the southern margin of the Qinling

    • 摘要: 秦岭造山带南缘的大巴山巨型逆冲推覆构造主要是在秦岭造山带板块俯冲碰撞造山与中、新生代以来陆内造山过程中长期复合作用形成的。详细的室内外构造研究表明,巴山逆冲推覆构造可以巴山弧形断裂带为界划分为北大巴山逆冲推覆构造和南大巴山逆冲推覆构造。北大巴山自北而南依次由安康-武当推覆体、紫阳-平利推覆体、高桥-镇坪推覆体和高滩推覆体逆冲叠置而成。南大巴山则以镇巴-阳日断裂为界,分为北部的前陆冲断褶皱带和南部的前陆褶皱带。北大巴山主要是印支期碰撞造山作用和燕山期陆内逆冲推覆作用叠加改造的结果,南大巴山则主要是燕山期递进变形过程中的产物。构造变形北强南弱,北以冲断褶皱变形为特征,南以皱褶作用为主;北部褶皱紧闭复杂,向南渐变为宽缓的薄皮构造。逆冲作用在时序上具有由北向南扩展传递的特点。

       

      Abstract: The huge Dabashan thrust nappe structure on the southern margin of the Qinling orogenic belt mainly formed by long-continued combined action of Late Triassic plate subduction and collisional orogeny of the Qinling orogenic belt and intracontinental orogeny since the Meso-Cenozoic. Detailed field and laboratory studies indicate that the Dabashan fold-thrust nappe structure may be divided into the northern Dabashan thrust nappe structure and the southern Dabashan thrust nappe structure with the Bashan arc-shaped thrust fault as the boundary. The former consists from north to south of the Ankang-Wudang nappe, Ziyang-Pingli nappe, Gaoqiao-Zhenping nappe and Gaotan nappe. The southern Dabashan thrust nappe structure is subdivided into the foreland thrust fold belt in the north and foreland fold belt in the south with the Zhenba-Yangriwan fault as the boundary. The northern Dabashan thrust nappe structure mainly resulted from overlapping and modification of the Indosinian collisional orogeny and Yanshanian intracontinental thrusting, while the southern Dabashan thrust nappe structure is the product of Yanshanian progressive deformation. The northern zone is characterized by intense folding and thrusting, while the southern zone by folding. The folds are tight and complex in the north and become gentle thin-skin structure southward progressively. The thrusts propagated southward in terms of the time sequence.

       

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