摘要
大型湖泊三角洲主要形成于淡水或微咸水湖的滨岸地带。湖泊三角洲的突出特征是以分流河道砂体为骨架,河口坝沉积不发育.笔者按地层特征将湖泊三角洲分为两种基本类型:一种是缺乏完整进积序列的薄的浅水台地型三角洲,另一种是进积序列较完整的巨厚的深水盆地型三角洲。前者发育在基底稳定.水深很浅的滨岸带,后者是三角洲推进到有巨厚泥质充填物的深盆地区的产物。在大型湖盆中,随着盆地的充填作用,三角洲体系可以在空间上从“浅水”型向“深水”型过渡,在时间上从“深水”型向“浅水”型连续地演变。
Large lacustrine deltas are mainly formed in the shore area of fresh or low salinity lakes. They are usually interpreted as the type of Mississippi river-dominated deltas because of low wave energy and lacking of tidal effect. The development of a complete progradational sequence is used as an important criterion for the identification of such deltas in subsurface geological study, and the river mouth bars are considered as an essential genetic facies which marks the site of major accumulation of sand deposits and represents a favourable fades zone for hydroncarbon accumulation. Based on observation and analysis of modern and ancient lacustrine deltaic deposits, the authors suggest that the marine Mississippi delta can not be used as a universal model for lacustrine deltas. The majority of lacustrine deltas in the subaerial basins bearing oil and gas of China are formed in freshwater lakes. The bed load is translated into the lake far off the river mouth instead of constructing conspicuous river-mouth bars, because the density of river water ladden with sediments is usually greater than that of lake water and river can maintain a high speed after entering the lake. Even though any thin river-mouth bars are ever formed,they are likely to be eroded by latter river action which sometimes cuts deep into the basement of the lake. The skeletal sand bodies of lacustrine deltas are therefore composed mainly of river channel or distributary channel sands.
The lacustrine deltas in the Oidos basm and other oil-bearing basins of China are subdivided into two basic types on the basis of their stratigraphic character, namely shallow-water platform delta with an incomplete progradational sequence and deep-water basin delta with a fairly complete and thick progradational sequence. The former is formed in the shallow shore area with a stable bassement. It progrades lakeward quickly and has a wide distribution with banded channel sand bodies. The latter is the product of delta prograding onto the deep basin filled with th
出处
《沉积学报》
CAS
CSCD
北大核心
1991年第4期1-11,共11页
Acta Sedimentologica Sinica
