摘要
在系统回顾传统三角洲成因模式基础上,介绍了一种发育于低可容纳空间背景条件下,由内部结构相对简单、规模相对局限的多个朵体相互叠置而成的叠覆式浅水三角洲。以现代浅湖沉积过程分析、实验模拟等为基础探讨了此类三角洲的形成过程、内部结构特征与解剖思路、连片性与连通性及沉积发育条件等。结果表明,叠覆式浅水三角洲发育过程分为2个阶段:单一朵体发育与复合朵体发育。单一朵体发育又可分为舌状向前伸展式和帚状侧向加积式,复合朵体发育则表现为进积、退积、侧积等多种叠置方式,进而以不同时期分流河道为纽带叠合成大面积的沉积体;朵体发育过程中遵循"填洼"原理,即优先沉积于可容纳空间发育的低洼处,一旦有效可容纳空间被填满,朵体或复合朵体将会迁移至其他低洼处;叠覆式浅水三角洲不具有传统三角洲以分流河道为骨架的层状结构特征,而是由不同时期三角洲朵体相互叠置而成,具有典型的"同层不同期"特征;不同时期三角洲朵体受可容纳空间与动态地貌控制而呈三维叠置,而非简单的层状叠加,使得三角洲内部呈现出立体拼合的结构特征,单一朵体是地层对比的基本单元,展布范围有限,与相邻朵体发育于不同时间单元,只能在复合朵体约束下小范围追踪。不同时期朵体之间的连通性受控于分流河道下切能力、沉积物供给沙泥比、湖平面升降周期等因素;沉积物供给充足、地形坡度低、湖平面长距离迁移造成的河道稳定性弱是此类三角洲发育的重要条件。叠覆式浅水三角洲成因模式的提出为此类发育于低可容纳空间背景下大型河流-湖泊三角洲提供了一种合理的地质成因解释模型,进一步深入分析其内部结构特征将为提高此类三角洲的勘探开发效率提供有益指导。
Based on a systemic review to the genetic model of traditional delta,a kind of superimposed shallow-water delta was introduced which is developed in low-accommodation condition and consisted of numerous lobes with relatively simple internal structures and limited scales.The formation process of this type of delta,internal structure characteristics,anatomic strategy,connectivity and depositional condition are discussed on the foundation of sedimentary process analysis as well as experimental simulation of modern shallow lake.It turned out that the development process of superimposed shallow-water delta can be divided into two stages,namely single and compound lobe developments.Single lobe development can also be divided to linguloid forward-and lateral accretion-types;compound lobe development shows multiple superposition patterns such as progradation,retrogradation and lateral accretion,and then superimposed to large-area sedimentary bodies by the link of distributary channel from different times.The development process of lobes follows filling depression principle,namely preferentially depositing in low-lying areas in accommodation,and these lobes or compound lobes will transfer to other low-lying areas once the valid accommodation was filling-in.Superimposed shallow-water delta is formed from the superposition of delta lobes from different periods with typical feature of ＂same layer in different time period＂,rather than stratified structure in the framework of distributary channel for traditional delta.Delta lobes from different periods are superimposed in 3-dimension controlled by accommodation and dynamic landform,rather than simple superimposition,which in turn make delta interior with stereoscopic structure.Single lobe is the basic unit for stratigraphic correlation with limited distribution range,which is developed in different time unit with adjacent lobes,an can only be tracked in a small range under the control of compound lobes.Connectivity between different lobes is depended on several factors suc
出处
《地质科技情报》
CAS
CSCD
北大核心
2013年第3期59-65,共7页
Geological Science and Technology Information
基金
国家自然科学基金项目(41172106
41072087)
关键词
低可容纳空间
浅水湖盆
动态地貌
成因结构
叠覆式浅水三角洲
low-accommodation
shallow-lacustrine basin
dynamic geomorphology
internal architecture
superimposed shallow-lacustrine delta
