Vertical grain-size trend of mouth bar in lacustrine fan delta:Flume experiments  

作　　者：Ke Zhang Sheng-He Wu Jun-Jie Wang Yun-Jie Xu Zhen-Hua Xu Jia-Jia Zhang 

机构地区：[1]State Key Laboratory of Petroleum Resources and Prospecting,China University of Petroleum(Beijing),Beijing,102249,China [2]College of Geosciences,China University of Petroleum(Beijing),Beijing,102249,China [3]School of Geosciences,Yangtze University,Wuhan,Hubei 430100,China

出　　处：《Petroleum Science》2022年第5期1964-1977,共14页石油科学（英文版）

基　　金：supported by the National Natural Science Foundation of China(No.41772101)。

摘　　要：Field observational previously indicated a mouth bar of a fan delta could exhibit a fining-or coarseningupward trend,which bring a new challenge to the identification of mouth bar in subsurface studies due to the lack of morphological descriptions.Previous studies have indicated that effluent behavior in rivermouth system can affect the vertical grain-size trend of mouth bar,but the drivers and magnitude of this phenomenon are not understood.We conducted flume experiments to investigate the mechanism and controlling factors of vertical grain-size trend of mouth bar.Experiment with a steeper slope of the substrate layer,greater discharge,higher sediment/water ratio,and coarser sediment induced a finingupward trend of mouth bar,because the effluent was dominated by strong inertia.Mouth bar in the experiment with a gentler slope of the substrate layer,smaller discharge,lower sediment/water ratio,and finer sediment exhibited a coarsening-upward trend dominated by the friction-dominated effluent.The relationship between the vertical grain-size trend of mouth bar and the gradients of foreset bedding in small-scale flume models and the cut-off of 15°-18°are applicable in natural systems.Identifying depositional setting to infer depositional process in river-mouth system and analyzing the plane geometry of sandbodies are two steps in the interpretation of ancient fan deltaic rock record.

关 键 词：Mouth bar Vertical grain-size trend Effluent behavior INERTIA Bed friction 

分 类 号：P618.13[天文地球—矿床学]