CAJ | 학술논문

南大巴前陆冲断带位于秦岭造山带向四川盆地过渡的部位,是晚三叠世扬子-秦岭俯冲碰撞与中新生代以来陆内造山形成的.根据构造变形的几何学特点,自北东向南西发育紧靠城口断层的根带、坪坝断裂与鸡鸣寺断裂之间的中带、镇巴-鸡鸣寺断裂与铁溪-巫溪隐伏断裂之间的锋带.各带发育不同的构造变形:根带的冲断层系统以逆冲叠瓦构造为主控构造组合,同时发育构造三角带、冲起构造和双重构造等组合;中带的冲断褶皱系统以发育断层相关褶皱组合为主;锋带发育为滑脱褶皱系统,以类侏罗山式褶皱为主控构造,同时发育了箱状背斜、膝折构造、倒转背斜、平卧褶皱、紧闭背斜、同斜背斜、虚脱不协调背斜等滑脱褶皱.垂向上发育3套区域性滑脱层:震旦系泥页岩和寒武系泥页岩、志留系泥页岩、下三叠统膏盐岩;在南秦岭自北而南的推覆作用下,依次沿这3套滑脱层逐级抬升而向南滑脱,存在"推覆作用(叠层滑动)→冲断作用(切层滑动)→层滑作用(顺层滑动)"的滑脱变形序列,从而造就南大巴的多种构造变形类型及其有序分布特征.
남대파전륙충단대위우진령조산대향사천분지과도적부위,시만삼첩세양자-진령부충팽당여중신생대이래륙내조산형성적.근거구조변형적궤하학특점,자북동향남서발육긴고성구단층적근대、평패단렬여계명사단렬지간적중대、진파-계명사단렬여철계-무계은복단렬지간적봉대.각대발육불동적구조변형:근대적충단층계통이역충첩와구조위주공구조조합,동시발육구조삼각대、충기구조화쌍중구조등조합;중대적충단습추계통이발육단층상관습추조합위주;봉대발육위활탈습추계통,이류주라산식습추위주공구조,동시발육료상상배사、슬절구조、도전배사、평와습추、긴폐배사、동사배사、허탈불협조배사등활탈습추.수향상발육3투구역성활탈층:진단계니혈암화한무계니혈암、지류계니혈암、하삼첩통고염암;재남진령자북이남적추복작용하,의차연저3투활탈층축급태승이향남활탈,존재"추복작용(첩층활동)→충단작용(절층활동)→층활작용(순층활동)"적활탈변형서렬,종이조취남대파적다충구조변형류형급기유서분포특정.
The southern Dabashan foreland fold-thrust belt lies between the Qinling orogenic belt and Sichuan cra-tonic basin, which is formed by the combined action of Late Triassic plate subduction and collision of the Qinling o-rogenic belt and subsequent intracontinental orogeny. From NE to SW, it can be divided into three sub-belts based on geometrical characteristics of its structural deformation. ( 1 ) The inner-belt adjacent to the Chengkou fault is characterized by an intense thrust system. The dominant structural assemblage is imbricate faults, accompanied by such subordinate structural assemblages as duplex, the triangle zone and pop-up structure. (2)The middle-belt between the Pingba fault and Jimingsi fault is characterized by the thrust-fold system with the fault-bend fold as its dominant structural assemblage. (3)The outer-belt between the Zhangba-Jimingsi fault and Tiexi-Wuxi concealed fault is characterized by the deformation-fold system. The dominant structural assemblage is the Jura-type-fold with different types of deformation-folds such as box anticline, kink structure, over anticline, recumbent fold, tight anticline, isoclinal anticline and detachment-disharmonic anticline. Three major regional detachment layers are found vertically: Sinian to Cambrian clay shale, Silurian clay shale and Lower Triassic halite-bearing gypsum. As the southern Qinling belt propagated southward, the fold-thrust system developed from nappe thrusting, with elevation of the three main deformation layers and detachment toward south within these layers. Actually it grows on the detachment evolvement sequence: errace slipping→secant slipping→interlayer-slipping. This model provides new insights into evolution of folding and thrusting by cap rock detachment, and is helpful to understand the deformation mechanism of the southern Dabashan foreland fold-thrust belt.