塔里木盆地西南部叶城凹陷下白垩统克孜勒苏群扇三角洲沉积特征及模式

以野外露头、岩心观察为基础,结合录井、测井及粒度分析,认为叶城凹陷下白垩统克孜勒苏群发育进积型扇三角洲,划分出扇三角洲平原与扇三角洲前缘水下分流河道、分流间湾与河口坝。扇三角洲平原受重力流作用明显;扇三角洲前缘主要受牵引流作用,在盆地的短轴方向延伸范围较小,而在长轴方向延伸范围较大,与相邻扇三角洲前缘朵叶叠置连片。扇三角洲由山前向断陷湖盆进积,在盆地的短轴方向构成一侧为陡坡、另一侧为宽缓斜坡的单断式断陷盆地充填模式。这种沉积模式不仅控制了扇三角洲各亚相单元的发育特征,而且对微相类型与砂体分布有控制作用。

Depositional features of the fan delta from lower Cretaceous Kezilesu Group in Yecheng sag, southwestern Tarim Basin

Based on field outcrop and core observation,combined with mud logging,logging and grain size analysis,the authors found that there are prograded fan delta sediments in lower Cretaceous Kezilesu Group of Yecheng sag,which can be divided into fan delta plain,fan delta frontier underwater distributary channel,mouth bar and interdistributary bay.Fan delta plain was obviously affected by gravity flow,whereas fan delta frontier was mainly affected by traction current.The latter extended limitedly in the direction of the short axis,and extended a considerable distance in superimposition association with adjacent fan delta frontier leaves in the direction of the long axis.Fan delta experienced progradation from the piedmont area to the faulted lake basin,forming mono-faulted fault basin filling model in the direction of the short axis,which was steep slope on one side,and wide and gentle slope on the other side.This sedimentary model controlled not only characteristics of each unit of the fan delta but also microfacies types and sand distribution.