峡东早震旦世南沱期冰川事件沉积

三峡东部早震旦世南沱期,自下而上由冰碛相、冰水相组成三套冰进-冰退不完整的沉积旋回。80 年代冰与非冰成为争论的焦点,但王丰岗南沱组剖面不具泥石流沉积的结构构造特征,两层紫红色冰碛岩所反映的只是冰川形成前冰碛物原始组分的富集方式,而非气候炎热的标志。根据区内南沱冰碛层中未发现海相夹层、未见波浪和潮汐水流构造、冰川坠石构造,以及横向变化迅速的特点,倾向于属大陆冰川,为低纬度、低高程的大陆冰盖型沉积,地球冰环模式可以比较圆满地加以解释。

GLACIAL EVENT SEDIMENTS OF EARLY SINIAN NANTUO STAGE IN THE EAST OF THE THREE GORGES

During Early Sinian Nantuo Stage,three sets of incompleted glacial advance glacial recession sedimentary cycles composed of glacial drift and aqueoglacial facies developed in the eastern Yangtze Gorges.In 1980s,the sediments that were glacigenous or acryogenic had once been the point at issue.But that the section of Nantuo Formation in Wangfenggang has no debris flow sedimentary structure,two wine tillite beds only reflect the enriching pattern of the origenal component of glacial till before the formation of glacier but not the mark of hort paleoclimate.According to the facts that no marine intercalated bed,no wave and tidal flow structures could be foundin the Nantuo Formation drift sheet,and rapid lateral changes could be found there,the sediments of the study area are suggested to be continental glacial sediments of low latitude and low altitude ice sheet type.This could be interpreted by global glacial ring model.