断陷湖泊水下扇类型与分布模式*

水下扇是断陷湖泊中一种重要沉积类型,近年来受到关注度越来越高。海洋和湖泊中与重力流有关的各类扇体的术语很多,诸如深水扇、盆底扇、湖底扇、斜坡扇、滑塌扇和浊积扇等,而它们都是不同类型的水下扇。国内沉积学界对湖泊水下扇这一术语的合理性一直有争议,与之相关的术语有水下冲积扇、近岸水下扇和远岸浊积岸等。文中梳理了有关水下扇的一些术语的含义异同,进而明确了断陷湖泊水下扇的基本类型;明确提出了湖泊外部物源体系与内部物源体系,并由此建立了湖泊水下扇的沉积分布模式;最后讨论对比了水下扇、冲积扇及扇三角洲之间的沉积差异,以期为今后深入研究这一类型沉积体提供借鉴。

Classification and sedimentary distribution pattern of subaqueous fan in fault lacustrine environment

As one of important sedimentary facies in fault lacustrine environment,subaqueous fans have been getting increasing concern in recent years. Although there are many terms for various types of fans associated with gravity flow in oceans and lakes,such as deep-water fan,basin flow fan,lacustrine fan,slope fan,slump fan,turbidite fan,etc,they are different types of subaqueous fans. It is controversial about the rationality of the term “subaqueous fan” in domestic sedimentology community. Terms related to it include subaqueous alluvial fan,near-shore subaqueous fan,and distal turbidite fan delta etc. In this paper,the similarities and differences of some terms related to subaqueous fan are clarified,and the basic types of subaqueous fan in fault lacustrine environment are defined. Based on the proposed concept of internal- and external-sediment source system of lacustrine environment,the conceptual sedimentary distribution pattern of subaqueous fan of fault lacustrine environment is established. The sedimentary differences among subaqueous fan,alluvial fan and fan delta are also discussed,in order to provide a reference for the further study of this type of sedimentary facies.