辽河坳陷双台子构造带沙三段层序格架内沉积特征及演化

针对辽河坳陷双台子地区勘探程度低、物源类型多、沉积条件复杂等问题，以陆相断陷湖盆层序地层学和沉积学理论为指导，对研究区沙河街组三段层序地层格架内的沉积相进行研究。通过岩心相标志分析，结合钻、测井和地震资料，识别了研究区沙三段发育扇三角洲、湖底扇和湖泊相3种沉积相类型。运用层序地层学理论及技术方法，建立了研究区沙河街组三段层序地层格架，将沙河街组三段划分为沙三下层序、沙三中层序和沙三上层序3个三级层序。沙三下层序和沙三中层序上升半旋回时期以大规模发育湖底扇为主；沙三中层序下降半旋回和沙三上层序时期北部发育扇三角洲，南部发育湖底扇。总体上，湖底扇呈现不断向凹陷中心迁移的特征，规模上呈现由小到大、再变小的沉积格局。

Characteristics and evolution of sedimentary sequences of the 3rd member of Shahejie Formation in Shuangtaizi tectonic belt,the Liaohe Depression

The Shuangatizi area in Liaohe Depression with multi-typed provenances and complicated sedimentary conditions has not been well explored.Armed with terrestrial rift basin sequence stratigraphy and sedimentology theories,the authors studied the sedimentary facies in the sequence stratigraphic framework of the third member of Shahejie Formation (Sha-3 member) through comprehensive analysis of core facies marks,drilling/logging and seismic data.Three sedimentary facies were identified,including the fan delta,the sublacustrine fan and the lacustrine facies.A sequence stratigraphic framework with 3 third-order sequences (namely the lower Sha-3 sequence,the middle Sha-3 sequence,the upper Sha-3 sequence) was also established by using relevant theories and technologies for the third member.It shows that sublacustrine fans were developed extensively during the full sycle of the lower and the ascending half cycle of the middle Sha-3 sequences,fan deltas were developed in the north part of the area and sublacustrine fans were developed in the south part of the area during the descending half cycle of the middle Sha-3 and the full cycle of the upper Sha-3.In general,the sublacustrine fans show features of migration towards the central depression with scales changing from small to large and then to small again.