摘要:
上世纪80年代初笔者根据现代长江三角洲考察中发现的"海进河床充填砂体",结合其他考察资料和古代砂体特征,建立了"水进型三角洲"模式。30余年来,越来越多的资料表明这个模式是正确的。目前普遍使用的"水下分流河道",经长江三角洲、云南洱海、内蒙岱海等现代沉积考察和大量卫星照片分析表明并不存在。而据旋回地层学、层序地层学等理论分析,水进型沉积是广泛发育的,水槽模拟实验也证实有水进期三角洲发育,因此笔者认为应以水进河床砂微相取代现今普遍误用的水下分流河道砂微相。四川盆地须家河组的须二、四段巨厚且大面积分布的砂岩是由三角洲平原各分支河道(分支河道砂)、前缘河口进积型(河口坝砂)和退积型沉积(水进河床砂)反复叠加,加上河道侧向迁移摆动与各个三角洲体相互拼接连片而成的。水进型三角洲多形成于湖、海水面上升期,地壳运动、气候变化、特殊地质事件、地形地貌以及沉积速率等都可能引起水面升降,当水面上升时常常形成水进型沉积。
Abstract:
According to the "water-transgression caused filling sand-bodies" found in Yangtze delta investigation in 1980s, based on the other investigation data and ancient sand-body features, the "water-transgression delta model" has been established. More than 30 years, more and more data have been showen that the model is correct. The modern deposition investigations and satellite pictures from Yangtze delta, Erhai in Yunnan, Daihai in Inner Mongolia et al., have revealed the recent popular model of "underwater distributary channel" is absent, but according to sedimentary theory (such as the cycle stratigraphy and sequence stratigraphy) analysis, the water-transgression deposition is widely developed. The flume simulation experiment has also confirmed that delta is developed in transgression period, so water-transgression sand-body micro-facies should have replaced the underwater distributary channel micro-facies. Great thickness and largely distributed sandstone in member 2 and member 4 of Xujiahe Formation have been caused by the superimposition of multi-channel river mouth progradation (mouth sand bar), retrogradation (water-transgression channel sand-body),channel lateral migration and piecing together with multi-deltas. Water-transgression deltas have formed in transgression period of lake or sea level, and the tectonism, climate changing, particular geological events, topography and depositional rate and so on. could have caused the up and down of water level, and the water-transgression delta has been developed when the water level have went up.
点击查看大图
下载:
