CAJ | 학술논문

位于湖北省东部黄石地区制图尺度的近东西向黄荆山向斜和桐梓堡背斜是在印支期造山作用时形成的,主要由古生代及三叠纪沉积岩层序列组成.其中的下、中三叠统包括页岩、泥灰岩、石灰岩、白云质灰岩和白云岩等层状岩系.从构造地质学的观点出发,由下而上可划分为3个力学分层单位或组合,相互间存在有不同的黏度比或相对强度.在大型褶皱翼部,发育一系列中小型褶皱(其振幅从几米至上百米),如屋顶和墙壁状构造、膝状褶皱、平卧褶皱、翻转及叠褶构造等,覆于层理面及低缓角度正断层面之上.详细的三维空间构造解析指出,这些复杂的中小型构造产状和组合样式,与通常的寄生牵引褶皱和大的褶皱关系是相反的,即上层的相对运动或流动指向向斜的槽部,显示重力导致的滑动构造特征.这种滑动构造只是一类继发性的独立构造现象,可以解释为是在重力不稳定性影响下,部分沉积岩层沿着先存的倾斜层理面或拆离剪切带向下坡有限滑动的结果.所发育的特征性构造取决于涉及的岩层及力学分层单位的能干性或相对强度.在大型褶皱翼部岩层向下滑动的尺度、速度及可行性,与层理面的倾斜度及拆离带的厚度、黏度等因素相关.类似的重力滑动构造在中上扬子地区的沉积岩层中常可观察到,同时,地表的滑坡、岩崩及山体垮塌等地质灾害过程与有限的重力滑动构造的发育,其基本原理和许多特征都是相似的.强调指出,重力不稳定性作为地质过程、构造变形及许多地质灾害的起因,在地壳的不同层次和地表都有显示.
위우호북성동부황석지구제도척도적근동서향황형산향사화동재보배사시재인지기조산작용시형성적,주요유고생대급삼첩기침적암층서렬조성.기중적하、중삼첩통포괄혈암、니회암、석회암、백운질회암화백운암등층상암계.종구조지질학적관점출발,유하이상가화분위3개역학분층단위혹조합,상호간존재유불동적점도비혹상대강도.재대형습추익부,발육일계렬중소형습추(기진폭종궤미지상백미),여옥정화장벽상구조、슬상습추、평와습추、번전급첩습구조등,복우층리면급저완각도정단층면지상.상세적삼유공간구조해석지출,저사복잡적중소형구조산상화조합양식,여통상적기생견인습추화대적습추관계시상반적,즉상층적상대운동혹류동지향향사적조부,현시중력도치적활동구조특정.저충활동구조지시일류계발성적독립구조현상,가이해석위시재중력불은정성영향하,부분침적암층연착선존적경사층리면혹탁리전절대향하파유한활동적결과.소발육적특정성구조취결우섭급적암층급역학분층단위적능간성혹상대강도.재대형습추익부암층향하활동적척도、속도급가행성,여층리면적경사도급탁리대적후도、점도등인소상관.유사적중력활동구조재중상양자지구적침적암층중상가관찰도,동시,지표적활파、암붕급산체과탑등지질재해과정여유한적중력활동구조적발육,기기본원리화허다특정도시상사적.강조지출,중력불은정성작위지질과정、구조변형급허다지질재해적기인,재지각적불동층차화지표도유현시.
The major map-scale Huangjingshan syncline and Tongzibao anticline with a predominant E-W trend, formed during the Triassic Indo-China orogeny, are exposed in Huangshi area, eastern Hubei Province. The folds are mainly composed of Paleozoic and Triassic sedimentary strata in which the Triassic sed-imentrary sequence consists of a series of interbedded shales, marls, limestones, dolomitic limestones and dolomites with different values of viscosity contrast. A variety of meso-scale folds, from a few metes to o-ver hundred metres in amplitude, such as roof and wall structure, knee fold, recumbent fold, flap and cascade etc. with flat-lying axial surfaces, resting on bedding planes and low-angle normal faults, occurr on the limbs of the major map-scale folds. Detailed three-dimensional structural observations and analyses have revealed that the intricate structures have an attitude or aggregate that is the reverse of the normal parasitic drag-fold relationship to the major folds. They clearly point to the movement or flow of the upper beds towards the synclinal troughs, and display features of gravity-induced sliding structures. The sliding structures are only secondary, independent phenomena, and hence can be best interpreted as products of the gravitational instability, leading to a limited sliding along the pre-existing dipping bedding planes or detachment shear zones. The particular structures developed depend on the competency or relative strength of the mechanical stratigraphic units and the sedimentary strata involved. The extent of the limited sliding structures and the ease or speed of sliding of bedded rocks down the flanks of the major anticline increase with in creasing bedding plane dip and detachment zone thickness. Similar structures are often seen within sedimentary strata in the upper-middle Yangtze River regions. At the same time, there is a similarity of principle in rockslide or avalanche movements and those of the limited sliding structures. It is emphasized that the gravitational instability appears in different scales and at different levels in the crust as the principal cause of geological processes including many geological disasters.