宁夏香山群深水沉积类型及其研究意义

Sedimentary Type of Deep-water Deposits and Its Research Significance

宁夏中奥陶统香山群为一套遭受轻微区域变质的灰绿色中-细粒长石石英砂岩、板岩、砾屑灰岩和硅质岩等,从下到上可分为徐家圈组、狼嘴子组和磨盘井组。系统地论述了香山群发育的各种深水沉积的特征及其沉积序列,认为香山群由深水原地沉积和深水异地沉积组成,其中后者主要包括浊流沉积、碎屑流沉积、内波、内潮汐沉积和深水复合流沉积。垂向组成单元自下而上依次为浊流沉积层(Ⅰ)、牵引流沉积层(Ⅱ)和半深海沉积层(Ⅲ)。这些认识不仅对进一步开展香山群的沉积学研究具有重要的意义,而且也可为该地区早古生代构造环境的研究提供重要的信息,同时也为目前在国际上引起注意的深水重力流的流体特征研究提供新的实例。

The Xiangshan Group in Ningxia Autonomous Region,composed of grayish green,fine-to medium-grained light metamorphic subarkoses,slates,gravelclast limestones and cherts,was divided into three formations,from bottom to top as follows:Xujiajuan,Langzuizi and Mopanjing Formation.The sedimentary features of each type and the vertical sedimentary association were systematically described.The results indicate that the sedimentary type composed of in situ deposits and autochthonous in deep-water,and the later includes the deposits of turbidity currents,debris flows,internal-waves and internal-tides,and deep-water combined-flows.And the vertical sedimentary association can be divided into a lower dense flow deposit division (Ⅰ),an intermediate traction flow deposit division (Ⅱ),and an upper hemipelagic deposit division (Ⅲ).All these have a great significance both in the sedimentary research of Xiangshan Group and the tectonic environment in early Paleozoic of the study area,and also provide an example for the research of sedimentary currents of gravity flow in deep-water.