鄂尔多斯盆地西南缘岐山地区中奥陶统沉积特征及沉积环境研究  

A study on the Middle Ordovician sedimentary characteristics and environment of Qishan region at the southwest margin of Ordos Basin

作　　者：刘溪[1] 任战利[1] 李文厚[1] 陈强[2] 贾德生[1] 

机构地区：[1]西北大学地质学系西安710069 [2]长安大学地球科学与资源学院西安710054

出　　处：《地质科学》2017年第3期931-942,共12页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：国家自然科学重点基金项目（编号：41330315）和中央高校基本科研业务费专项（编号：0009.2014G1271062）资助.

摘　　要：摘要本文通过野外剖面实测、样品采集、薄片鉴定等手段，收集地球化学数据及前人研究材料，对岐山地区岩性组合、沉积构造进行了研究，分析其中奥陶统沉积环境演化过程。结果表明，岐山地区在中奥陶统下马家沟组早期沉积自云岩，为局限海台地环境；下马家沟组中、晚期沉积中厚层状灰岩，为开阔海台地环境；上马家沟组沉积厚层的纹层状灰岩夹碎屑流、浊流等深水沉积建造，水体逐渐加深，并进入台地前缘斜坡沉积环境；峰峰组发育厚层的纹层状灰岩，为台地前缘斜坡环境并向深水海盆靠近。由此判断岐山地区应为南缘凹陷上，除淳化一句邑次级凹陷以外的另一个水体更深、坡度更大的次级凹陷。Through the feild sections measurement, sample selection and thin section analysis and the selection of geochemical data and previous research matetials, this paper studies the lithology composition and sedimentary structure in Qishan area and analyzes the evolution of sedimentary environment in Middle Ordovician. The results show that in Middle Ordovician Qishan area was in limited sea platform environment with deposition of dolomite at early stage of Lower Majiagou Formation and was in open sea platform environment with midium thich limestone depositing at the middle-late stage of Lower Majiagou Formation. In Upper Majiagou Formation, the area developed deposits of thick lamellar limestone interbedded with deep-water sedimentary construction like debris flow and turbidity flow which indicated platform foreslop enviroment and then in Fengfeng Formation, Qishan was still in platform foreslop enviroment but closer to deep water basin and developed thick lamellar limestone. With such envelops, it can be concluded that in Middle Ordovician, besides Chunhua-Xunyi depression Qishan region should be in another secondary depression with deeper water and steeper slope on southern depression.

关 键 词：地层特征 岩性 沉积构造 重力流 地球化学 沉积环境 中奥陶统岐山地区 

分 类 号：P512.2[天文地球—地质学]