近岸水下冲积扇相特征及实例

CHARACTERISTIC OF BEACHY UNDERWATER ALLUVIAL FAN FACIES——WITH A PRACTICAL EXAMPLE

董荣鑫 苏美珍

Dong Rongxin Su Meizhen

同济大学海洋地质系

Department of Marin Geology, Tong Ji University

研究区为苏北东台坳陷中的一个北缓南陡的箕状凹陷——高邮凹陷。该凹陷形成于始新世末,其中沉积了厚达数千米的陆相砂泥岩地层,剖面层序如表1。前人曾认为戴南组的砂体是三角洲相。近年来,笔者对戴南组的沉积类型及其沉积环境进行了研究,认为戴南组的沉积受古地理环境的控制,北部缓坡带上,沉积物源主要来自北部,以三角洲相为主;南部陡坡带上,沉积物源主要来自南部,其沉积特征与三角洲明显不同,为另一种沉积物类型——近岸水下冲积扇相,本文着重讨论戴南组的近岸水下冲积扇相的特征。

Gaoyou Depression is a dustpan like depression steep in north and gentle in south. The properties of sediments from Dainan Formation in the depression are obviously controlled by paleogeographic environment. The sediments on the northern gentle slope belt of the depression mainly are of delta facies and that on the southarn slope belt mainly of beachy underwater alluvial fan facies. The origin of the beachy underwater alluvial fan facies can be either the transport of terrigenous elastics directly into the lake or the extension of the terrigenous pluvial facies into a lake basin, or may be the both. This paper introduces the lithological properties, the rock texture, and the structure of the beachy underwater alluvial fan facies in details, and presents a profile model as well.

https://doi.org/10.11781/sysydz198504294