阿尔泰诺尔特地区晚古生代的沉积环境和古地理分析

Sedimentary environment and palaeogeography of late Palaeozoic in Nurt area, Xinjiang

诺尔特地区位于新疆阿尔泰东北部 ,地理位置属富蕴县。该地区主体构造为北东向 ,出露地层为前震旦系富蕴群、震旦系哈巴河群、泥盆系忙代恰组和石炭系红山嘴组 ,其中后两者占主导地位。泥盆系为一套类复理石建造 ,主要岩性有粉砂岩、细砂岩、钙质粉砂岩和少量火山岩 ;石炭系红山嘴组可以分为三个段 ,一段为粉砂岩、粉砂质泥岩、细砂岩与粉砂岩交替的韵律沉积岩、岩屑砂岩等 ,二段为粉砂质泥岩、粉砂岩、钙质粉砂岩和生物屑灰岩 ,三段火山物质大量出现 ,下部为火山碎屑和陆源碎屑的混合沉积 ,上部以凝灰岩为主 ,顶部出现火山角砾岩。根据岩性特征和沉积构造分析 ,泥盆系的沉积环境为浅海 -半深海 ,以大陆斜坡为主 ;石炭系的沉积环境为浅海陆棚、滨岸和开阔台地 ,其中又包括一些小环境。通过沉积环境的分析 ,可以得出三种沉积相模式。

The Nurt distinct lies in northeastern Altay, Xinjiang. The strata exposed in the area are pre-Sinian,Sinian?Devonian and Carboniferous. The two later are dominated. Devonian is a flysch-similar formation which consists of siltstone, fine-sandstone, tuffy siltstone and a little amount of conglomerate, pyroclastic rock. Carboniferous includes three members. The first one consists of siltstone, silty mudstone, debris sandstone and rhythmic laminae of fine-sand and silt which exist expansively. The second one is composed of muddy siltstone, silty mudstone, bioclastic limestone and a small amount of pyroclastics. The mixed sediments of terrestrial and pyroclastic make up the third one. Based on the analyses of sedimentary facies and sedimentary structure, we consider the sedimentary environment of Devonian as a continental slope, i.e. there was a shallow sea in middle Devonian and a bathyal in late Devonian. In Carboniferous this area underwent shelf, shore and open platform with a few small environments. Then the crust rose to be a continent. Three models of sedimentary facies are suggested in result of the above studies.