Study On The Structural Evolution And Its Sedimental Response Of South Turgay Basin,Kazakhstan

South Turgay basin is located in central Kazakhstan.Its tectonic position is in the turning end of Ural-Tianshan suture zone.It is a typical Mesozoic rift basin.Guided by the rules of structural geology,sedimentology and sequence stratigraphy,this paper used seismic,drilling,logging and geological data to study the Mesozoic tectonic evolution of south Turgay basin.It revealed the structural features of strike-slip and inversion in south Turgay basin and studied the active stages as well as flat distribution of each main boundary fault.Combined with stratigraphic thickness diagram,It studied the evolution of basin pattern in Jurassic-Cretaceous.On this basis,this paper also studied the slope type and its distribution characteristics as well as the response characteristics in different tectonic evolution stages.Mesozoic tectonic evolution of south Turgay basin is divided into five stages:initial rift period,main rift period,rift-depressed diversionary period,depression period and uplift period.Main growth faults controlled the settlement of each depression;Different evolutionary stages developed different types of slopes breaks,it mainly developed fault slope break zone and bent slope break zone in rift period;it developed fault slope break zone and gentle slope topography in rift-depressed diversionary period;it developed wide and gentle slope topography in depression period.There were different distribution characters of slope break in different stages.Tectonic movement controlled sedimentary system.Episodic tectonic motion controlled sequence of sedimentary filling.The filling sequence is divided into three main basins:it mainly developed lake sediments in J1-J2 period,delta and lake sediments in J3 period,alluvial plains sediments in Cretaceous period.Palaeogeomorphology controlled the distribution of sedimentary facies.Projections between depressions controlled the distributions of source;structural fault adjustment zone controlled the aggregation direction and transport channel of source;The structural slope-break zone controlled the developmental type and distribution law of depositional systems.In rift-depressed diversionary period,gentle slope topography controlled of a large river-delta system;basin topography of slip-reverse controlled of deposition of J3ak period.In depression period,tectonic pattern is relatively flat,source supply and variation of accommodation controlled the development of river and delta sedimentary.Highland in lake controlled beach bar deposition.Basin gradually shrink until it is filled.