扭断裂及基底掀斜控制上覆地层的褶皱——东海Y构造的一种解释模式

FOLDING OF UPPER LAYERS CONTROLLED WRENCH FA-ULTING AND BASEMENT TILTING-AN EXPLANA-TION PATTERN OF Y STRUCTURE IN THE EAST CHINA SEA

位于东海XH凹陷的Y构造,以其两侧发育的NE—NNE向高角度逆冲断层和构造顶部发育的NW、近EW向的正断层、平面展布的“S”型构成其独特的构造风格。本文致力于应用T.P.Harding的扭动构造理论,结合该构造的成因机制进行了分析,并得出结论:Y构造为中新世末期的龙井运动压扭作用的产物。

Y structure, located in XH sag of the East China Sea, is characterized by the NE-NNE high-angled thrust faults on the western side and the NW (near EW) S-shaped normal faults on the top of the structure. Using T.P.Harding's wrench structure theory, together with on-the-spot exploration data of the structure, this paper has analysized the genetic mechanism of the structure. And a conclusion has been given that Y structure was produced by compressional wrench of Longjing Orogenic Movement in the end of Miocene on the basis of the following evidences. 1. Northern part of Y structure shows positive-flower arched-up folds controlled by wrench faulting. Cone-like deformation part converges downwards and dominant wrench fault inserts into the basement in an almost vertical way. 2. Southern part displays box folds controlled by a set of dextral shear couples. Basement block tilting has been formed due to the vertical components of compressing and wrenching in the duration of shearing, which have also controlled the folding of the upper layers. Half-flower thrust faults and strata drag represent major shear surface on the western side of Y structure. 3. Negative-flower faults developed on the top of Y structure are sub-sinistral wrench faults formed in association with compressional wrenching. Their existence has resulted in the uplift of basement and given a limitation to YX fault zone towards the south.