准噶尔盆地南缘古牧地背斜几何学与运动学分析

Geometric and Kinematic Analyses of Gumudi Anticline in Southern Margin of Junggar Basin

古牧地背斜是北天山山前典型的断层相关褶皱及其叠合的复杂构造单元,经历了强烈的构造变形。从过古牧地背斜地震剖面的构造分析入手,以地表露头和钻井揭示的构造现象为约束条件,通过断层相关褶皱分析确定浅层褶皱形态,并根据褶皱与断层形态在几何学上的定量关系,推测深部构造样式,建立与实际吻合的构造模型,并对古牧地构造进行了运动学恢复,再现了构造变形过程。分析表明,古牧地构造整体为一近东西走向背斜,构造变形发生在燕山运动Ⅲ幕至喜马拉雅运动中晚期;古牧地构造浅层构造东段为前缘突破的断展背斜,向西逐渐过渡为近似两边对称的滑脱型断展背斜,深部构造是以中侏罗统西山窑组煤层和二叠系芦草沟组为顶、底板的双重堆垛构造。

The Gumudi anticline is a typical and complex structure unit of superimposed fault-related folds in the piedmont of northern Tianshan Mountains, with strong deformation. Based on the analysis of 2D seismic profile crossing Gumudi anticline, constrained by the surface outcrop and drilling-revealed structural appearances, this paper presents the shallow folds shapes by fault-related folds analysis, speculates the deep structural styles according to the fold-fault quantitative relationship, in geometry, and then develops the reasonable structural model for Gumudi anticline, by which reappears the structural deformation procedures through kinematic recovery of this anti- cline. The study indicates that Gumudi anticline is a nearly east-west trending anticline and its tectonic deformation took place from late Yanshan movement to middle-late Himalayan movement. The eastern part of the shallow structures in Gumudi anticline is a front faulted- extensional anticline, toward the west it transits to nearly two-side symmetrical detachment-like faulted-extensional anticline, and the deep structure is a dual-stacking structure with the roof Xishanyao coal seam of the Middle Jurassic and the floor Lueaogou formation of Permian.