摘要:
本文根据现代沉积学理论,对我国西南及中南部早震旦世南沱组砂岩、砾岩的物质成分、沉积岩相、古板块构造、古气候—地理环境等,进行了系统的分析与研究。认为南沱组是山间泥石流和海相重力流沉积作用的产物,并划分为以下四种类型:（1）山间—山前泥石流（滇东、鄂中古陆）;（2）火山泥石流（四川西昌）;（3）浅海相重力流（黔中、长江中下游）;深水斜坡相重力流（黔东南、桂北及湘南）。南沱期大规模暴发重力流的主要原因:一是南沱组坚硬和巨厚砂岩、砾岩覆于前震旦纪浅变质岩系之上,形成一个易于滑动的界面;二是在低纬度区的热带气旋和火山活动,起到了触发的作用。
Abstract:
In the light of the theory of modern sedimentology, the author has made a systematic analysis and study of the material composition, regional distribution, features of sedimentary facies, paleostructure and paleoclimatic-paleogeographic environments of sandstone and conglomerate of the early Sinian Nantuo Formation in southwestern and south-central China. It is considered that the Nantuo Formation is the product of intermontane debris flow and marine gravity flow deposition. The formation may be divided into the following types: （1） intermontane-piedmont debris-flow deposits （e. g. in eastern Yunnan and at peripheries of the central Hubei oldland）; （2） volcanic debris-flow deposits （e. g. in Xichang, Sichuan）; （3） neritic gravity-flow deposits （e. g. in central Guizhou and the middle and lower Yangtze River valley）; and （4） deep-water slope gravity-flow deposits （e. g. in southeastern Guizhou, northern Guangxi and southern Hunan）. The main causes responsible for the generation of large-scale gravity-flows in the Nantuo’an Stage （early Sinian） are the following: （1） hard and very thick sandstone of the Nantuo Formation overlies pre-Sinian low-grade metamorphic slate and phyllite, forming a very easily sliding structural interface; （2） the tropical cyclore and volcanism in low-latitude areas triggered their occurrence.
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