逆冲活动对准南前陆盆地层序构成的影响及意义

Influence of Thrust Tectonism on Sequence Contexture of Southern Junggar Foreland Basin and Its Significance

摘要:

新近纪准噶尔盆地南缘是在北天山强烈逆冲构造背景下发育的前陆盆地.其新近系沙湾组塔西河组可划分为1个二级层序,2个三级层序,均由角度不整合、平行不整合或沉积环境转换面所分隔.整个二级层序的沉积构成反映了从前陆逆冲挠曲沉降到回弹隆升的演化过程,层序1沉积构成明显受逆冲构造活动控制,而回弹隆起影响了构造相对宁静期的层序2内部沉积构成.新近纪逆冲构造活动阶段的内部演化,制约了同期的冲积扇扇三角洲沉积体系.受逆冲构造活动影响,层序1(沙湾组)扇三角洲砂体不断向盆地推进,侧向连片,垂向上相互叠置形成厚度可观的储集体,其下伏前期深湖相烃源岩,离生烃中心近,上覆层序2(塔西河组)发育的大量细粒沉积物作为良好的盖层,易形成大型油气田.

Abstract:

The southern margin of Junggar Basin was the foreland basin at the tectonic underground of intense thrust of North Tianshan in the Neocene.The Shawan FormationTaxihe Formation of Neocene was divided into one secondorder sequence,two thirdorder sequences,which were separated by angle unconformity,parallel unconformity,and transformation surface of depositional environment.All the depositional contexture of the secondorder sequence reflected the evolutionary process which was from flexural subsidence caused by foreland thrust to rebounded uplift,the depositional contexture of Sequence 1 was obviously controlled by thrust tectonic activities,and rebounded uplift influenced the inner depositional contexture of Sequence 2 which was in the period of tectonic relative quiet.The inner evolution of thrust tectonic activities of Neocene restricted the synchronous depositional systems of alluvial fanfan delta.Influenced by the thrust tectonic activities,the fan delta sand body of Sequence 1 (Shawan Formation) advanced continuously towards the basin,its lateral communicated,its vertical mutually superimposed to form considerable thick reservoir body,which was on the earlier deep lake oil source rock,and near to the oil source center,the overlying massive fine sediments of Sequence 2 (Taxihe Formation) may be favorable cap formation,large oil and gas field could easily be formed.