前陆盆地隆后坳陷区湖底扇沉积特征及主控因素——以塔北轮南地区三叠系为例

为了揭示前陆盆地隆后坳陷区湖底扇沉积特征及主控因素，利用岩心、分析化验、钻测井及三维地震资料，采用“点-线-面”相结合的方法系统研究塔北轮南地区中三叠统克拉玛依组T_Ⅱ油组的湖底扇沉积特征。结果表明，研究区发育富砂型湖底扇，其岩性以砾质粗砂岩、含砾粗砂岩以及中粗砂岩为主，垂向上见鲍马序列，递变层理、块状层理以及变形层理发育，测井曲线则具有微齿化线型-箱型或钟形-微齿化线型的组合特征，地震剖面上对应于中强振幅高连续或中强振幅透镜状或短轴状地震反射，均方根振幅属性可见典型的下切弯曲水道。同时，识别出3种亚相、5种微相类型，其中内扇亚相发育补给水道和堤岸微相，中扇亚相发育辫状水道和水道间微相，外扇亚相发育远源浊积岩。区内湖底扇分布在南部坡折带之下，发育多条典型的补给水道，辫状水道连片展布，水道间零星分布。本区湖底扇具备滑塌重力流的成因机制，是西北部和东北部辫状河三角洲前缘砂体堆积坡度过陡重力失稳下切形成补给水道，并经补给水道搬运堆积于深水环境形成的，其发育受到了前陆盆地幕式构造活动、古地貌以及物源供给等多个因素的控制，其中构造活动是湖底扇发育的诱因，古地貌影响其平面分布，物源供给则决定了湖底扇的岩性、物性和规模。

Sedimentary characteristics and controlling factors of sublacustrine fans in backbulge zone of foreland basin: Triassic in Lunnan area,Tarim Basin

In order to discuss the sedimentary characteristics and controlling factors of sublacustrine fans in backbulge zone of foreland basin,based on the cores,analysis assay,well logs and 3D seismic data,combined with the method of "point-line-surface",the characteristics of sublacustrine fan of T Ⅱ oil group of Middle Triassic Karamay Formation in Lunnan area of Tarim Basin were analyzed. The results show that sand-rich sublacustrine fans were developed in the study area, which are mainly composed of gravelly coarse sandstone,conglomeratic sandstone and medium-coarse sandstone,with Bouma sequence vertically developed,and grading bedding,massive bedding as well as deformed bedding could be recognized. In addition,the logging curves show a combination of micro linear dentalization and block or bell shaped. On seismic profiles,they are responded to middlehigh amplitude and high continuity refection or lenticular or short axial refection,and incised sinuous channels are identified on RMS(root-mean-square) amplitude attribute. Meanwhile,three subfacies and five microfacies were recognized,among which feeder channel and levee microfacies were developed in inner fan,braided channel and interchannels were developed in middle fan,and distal source turbidite were developed in outer fan. The sublacustrine fans located below the south slope break belt,with several distinct feeder channels developed,and compared with separated interchannels,the braided channels were continuously distributed. Caused by gravity flows,the sublacustrine fans were formed as a result of that a large amount of sandstone were transported to deepwater environment through feeder channels, and the development of sublacustrine fans were controlled by episodic tectonic activities of foreland basin, paleogeomorphology,and provenance supply. The development of sublacustrine fans was induced by tectonic activities,and the planar distribution characteristics were influenced by paleogeomorphology,with lithology,physical properties,and scale determined by provenance supply.