重庆石柱地区上二叠统吴家坪阶牙形石动物群及沉积环境  

Conodont Fauna and Sedimentary Environment of Wuchiapingian of Upper Permian in Shizhu Area,Chongqing

作　　者：杨宝忠[1] 张宁[1] 夏文臣[1] 

机构地区：[1]中国地质大学地球科学学院,武汉430074

出　　处：《地质科技情报》2008年第4期27-32,共6页Geological Science and Technology Information

基　　金：国家自然科学基金项目(40576028)

摘　　要：重庆市石柱县冷水溪剖面上二叠统吴家坪阶下部为粉砂岩、泥岩，局部夹煤线，上部为灰岩（含白云岩），夹硅质岩和页岩。对上部灰岩研究发现：下段（第161-181层）由灰泥岩、粒泥灰岩、白云岩化灰泥岩和白云岩组成，未发现牙形石；上段（第182～189层）以灰泥岩、粒泥灰岩为主，仅局部夹少量白云岩，牙形石含量极其丰富，共发现1属11种，包括Cguangyuanensb，forientalis、C．1iangshanensis，C．bizarrensis，C．longicuspidata，C．inflecta，C．renewalpostbitteri，C．protowangi，C．n．sp．A，C．n．sp．B和C．n．sp．C，其中C．renewalpostbitteri，C．protowangi，C．n．sp．A，C．n．sp．B和C．n．sp．C为新种。碳、氧同位素分析显示：下段岩层同位素值由下至上逐渐增高，向正向偏移，曲线呈锯齿状；上段岩层同位素值向上略变小，曲线平直，反映沉积环境变化较大。综合分析认为：下段岩层属于近岸局限环境，受淡水混合影响，海水盐度异常，不利于牙形石生存；上段岩层属于正常浅海环境，适合牙形石生活，牙形石含量极其丰富。根据C．renewalpostbitteri的首现位置可将吴家坪阶分为上亚阶和下亚阶。The Wuchiapingian of Upper Permian in the Lengshuixi section in Shizhu, Chongqing, is composed of siltstone, mudstone and limestone （including dolomite）, with intercalations of chert beds and shale. Based on the study of conodont biostratigraphy, the limestone was divided into 2 members. The lower member is composed of mudstone, wackestone and dolomite （lack in conodonts）, while the upper member is comprised of mudstone and wackestone, with a little dolomite （abundance conodonts）. Eleven species conodonts have been discovered, Clarkina guangyuanensis ,C. orientalis,C, liangshanensis,C, bizarrensis,C, longicuspidata,C, inflect,C, renewalpostbitteri,C, protowangi、C, n. sp. A,C. n. sp. B and C. n. sp. C, some of whom are new species, as C. renewalpostbitteri,C, protowangi,C, n. sp. A, C. n. sp. B and C. n. sp. C. The isotope analysis of carbon and oxygen shows that： the isotope values changed frequently in the lower member （lack in conodonts） while that changes less in the upper limestone member （rich in condonts）. The result reflects that the sedimentary environment has changed obviously. The lower member belongs to the alongshore circumstance where the salinity of sea water was abnormal due to the mixture of freshwater and the conodont growth was restricted. The upper member belongs to the normal shallow sea environment, where the conodonts grew well and abundant. Wuchiapingian can be subdivided into the Upper Wuchiaping substage and the Lower Wuchiapingian substage according to the first occurrence of C. renewalpostbitteri.

关 键 词：牙形石 沉积环境 上二叠统 吴家坪阶 

分 类 号：P534.46[天文地球—古生物学与地层学]