准噶尔盆地车排子凸起春光区块沙湾组沉积特征新认识

A New Discussion on the Sedimentary Characteristics of Shawan Formation in Chepaizi Area,Junggar Basin

准噶尔盆地车排子凸起沙湾组沉积环境存在较大争议,主流观点认为辫状河三角洲或者滩坝砂沉积。通过对研究区内钻井、古生物、地球物理资料分析认为,车排子凸起沙湾组并非水下环境,而是处于陆上暴露环境,发育冲积扇和河流沉积体系,其中研究区北部发育冲积扇体系,而中南部则发育河流体系,且不同沉积时期沉积体系类型发生变化:沙一段发育冲积扇—辫状河沉积,沙二段发育冲积扇—曲流河沉积,沙三段则缺少典型的河流沉积,以冲积扇体系及洪泛平原沉积为主。总体而言,春光区块沙湾组沉积期具有多物源、多沉积体系发育的特征,垂向上构成了两类冲积扇—河流体系沉积模式。

A big controversy about the sedimentary environment of Shawan Formation in Chepaizi area,of Junggar Basin is still existed in the previous views,the main view about that is considered most likely braided river delta or beach bar sand deposition. A further analysis based on the borehole,paleontology data and physical geography data was deemed that rather than the previous sedimentary model,the Chunguang block was likely exposed,alluvial fan and fluvial deposition. The alluvial fan system developed from the northern part of the study area and fluvial system was found in the south central area. Moreover,in different sedimentary period,the sedimentary system was changed：in member 1 of the Shawan Formation,alluvial- braided river sedimentation was formed and in member 2 of the Shawan Formation,alluvial- meandering river deposit existed,however,in member 3 of the Shawan Formation,Chunguang area lack of typical fluvial deposits,mainly alluvial fan system and the flood plain deposited. All in all,in the shawan sedimentary period,Chunguang block has the character whith multi-source deposition and multiple sedimentary system. In the vertical profile,two different alluvial-braided river sedimentary model have been built up.