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大量的地质资料表明,渤海湾地区下第三系断陷式凹陷中有着发育的重力流沉积。沉积物主要由陆源碎屑组成,其它的再沉积碎屑组份有鲕粒、化石碎屑、植物碎屑和海绿石等。重力流沉积作用的机制包括洪水类型和滑塌类型。地理环境方面,在陡岸、缓岸和深水平原均有重力流沉积。形态上有扇形和层状两种类型。笔者认为这种浊积扇采用“湖底扇”一词更为适宜,因为海底扇一词经常指示一个相当大的范围。 深水碎屑岩由典型的浊积岩(或传统的浊积岩)、块状砂岩、卵石质砂岩、颗粒支撑砾岩和杂基支撑岩层(包括泥石流、卵石质泥岩和滑塌岩)组成。浊积岩沉积在正常的湖相暗色泥岩之中。 湖底扇浊积岩中有一系列的沉积构造,诸如鲍玛序列、粒序层理、垂向液化逃逸管、碟状构造、撕裂屑、重荷构造、包卷层理和槽模等。
A large number of geological data show that there are developed gravity flow deposits in the lower Tertiary fault depression in the Bohai Bay area. Sediments are mainly composed of terrigenous debris, and other redeposited detritus components include oolites, fossil clasts, plant debris and glauconite. Mechanisms of gravity flow sedimentation include flood types and slump types. In terms of geographical environment, gravity flow deposits are found on steep banks, shore banks and deep-water plains. Form a fan-shaped and layered two types. The author believes that this turbidite fan uses the term “lake fan” is more appropriate, because the word sea fan often indicates a rather large range. Deep-water clastic rocks are composed of typical turbidite (or conventional turbidite), massive sandstone, pebble sandstone, grain-bearing conglomerate and miscellaneous supporting strata (including debris flow, pebble mudstone, and slump rock). Turbidites are deposited in the normal lacustrine dark mudstone. There are a series of sedimentary structures in turbidites of the lacustrine fan, such as the Bowman sequence, the sequence stratification, the vertical liquefaction escape tube, the sagittal structure, the tearing debris, the heavy load structure, the lamination bedding and the slot die.