鄂尔多斯盆地南缘奥陶系碳酸盐微相及其沉积环境分析  

Microfacies and Facies Analysis of the Ordovician Carbonates in the South Margin of the Ordos Basin

作　　者：袁路朋 周洪瑞[1] 景秀春[1] 王振涛[1] 传婷婷 房强[1] 

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083

出　　处：《地质学报》2014年第3期421-432,共12页Acta Geologica Sinica

基　　金：国家"973"项目(编号2011CB403001)资助成果

摘　　要：平凉—泾阳—耀县地区奥陶系碳酸盐岩发育良好,沉积类型多样。本文根据野外实测剖面研究和室内薄片分析,在研究区奥陶系归纳出10种微相类型,泥晶白云岩(MF-1)、细晶—极细晶白云岩(MF-2)、中—粗晶白云岩(MF-3)、白云岩—灰岩过渡岩(MF-4)、泥晶灰岩(MF-5)、粉屑灰岩(MF-6)、砂屑灰岩(MF-7)、含生物碎屑泥晶灰岩(MF-8)、含生物碎屑砂屑灰岩(MF-9)、砾屑灰岩(MF-10)。其中平凉奥陶系发育了9种、泾阳奥陶系发育了9种、耀县奥陶系发育了6种。比照Wilson碳酸盐沉积相模式和微相特征,将研究区奥陶系划分为局限台地(FZ-8)、开阔台地(FZ-7)、斜坡(FZ-4)、斜坡脚(FZ-3)以及深水陆棚(FZ-2)五个相带。通过对相带特征研究,认为马家沟期,平凉—泾阳—耀县一线自西向东海水由深变浅,反映马家沟期开始海侵方向在研究区自南向北。到平凉组沉积期,鄂尔多斯盆地全区海退,南缘地区海水却突然加深,直到背锅山组沉积期才全部退出。对三条剖面沉积相带组合的横向对比,表明研究区奥陶纪存在着多期的海侵—海退旋回。从区域构造背景分析,这些海侵—海退旋回可能与鄂尔多斯盆地南侧秦岭洋的演化有密切关系。Ordovician carbonate rocks are well-developed and various depositional types can be recognized in the Pingliang-Jingyang-Yaoxian area,which is located in the south margin of the Ordos Basin.Based on the observation at the outcrop and indoor microfacies analysis,10 microfacies can be divided,as Pingliang has 9 species,Jingyang has 9 species and Yaoxian has 6 species.According to these microfacies＇features of the vertical and horizontal combination and reference Wilson＇s （1975） carbonate sedimentary facies model,5 sedimentary facies belts can be summarized according to the microfacies combinate as restricted platform,open platform,slope facies,sloped footing and deep shelf.The combination characteristics of the sedimentary facies belts indicate that there are several transgression to regression occurred during the Ordovician.The comparison of sedimentary facies of Ordovician System in the study area indicate that sea shallowed from west to east,which can be infer that Majiagou Formation transgression direction from south to the north.In the deposition of the Pingliang Formation,regression occurred the whole Ordos Basin,but the water in the south margin of the Ordos Basin had suddenly deepened.And regression in this member occured at deposition of Beiguoshan Formation.That＇s may be related to Qin Lingyang＇s evolution.

关 键 词：微相分析 沉积环境 碳酸盐岩 奥陶系 鄂尔多斯南缘 

分 类 号：P578.6[天文地球—矿物学]