大型坳陷湖盆坡折带背景下的重力流沉积模式

Depositional Model of Gravity Flow of Slope in Large Down Warped Lake Basins

沉积盆地的坡折带是重力流发育的最有利场所,湖盆发育有和陆坡特征相似的坡折带,开展大型坳陷湖盆坡折带背景下的重力流沉积模式及其分布规律的研究具有重要意义。松辽盆地的龙虎泡—大安阶地具有明显的坡折带特征,且发育两级坡折。湖底扇是由沉积物重力流所搬运的沉积物在湖底堆积形成的沉积体,松辽盆地南部湖底扇主要由滑坡、碎屑流、浊流搬运的碎屑堆积而成。以松辽盆地为例,建立了短缓坡和长缓坡两种类型的重力流沉积模式,两种模式的湖底扇和下切水道的形态和分布模式均存在明显不同。

Slope break belt is the most favorable setting for gravity flow development. Slope break belt can be developed in Lake basins and has the similar characteristics with one in continental slopes. Therefore, the study on depositional model and distribution regularity of gravity flow of slope breaks in large down warped lake basins is of important significance. The characteristic of slope break belt in Longhupao-Da＇an terrace of Songliao Basin is distinctive, and it is a two-level slope break. Sublacustrine fan is formed by sediment that carried by gravity flow. The sublacustrine fan of the south Songliao basin consists chiefly of clastics carried by landslide, debris-flow and turbidity current. Taking slope break of Songliao basin as an illustration, the paper elaborated depositional models of gravity flow in short gradual slope and long gradual slope setting. This study has shown that there are distinctly different features between two type models, especially the shape and distribution pattern of sublacustrine fan and incised waterway.