甘肃北山大豁落地区牙形刺化石的发现及其对白云山组时代的限定  

The Discovery of Conodont Fossils in Dahuoluo Area in Ganau and the Related Date Determination for Baiyunshan Formation

作　　者：余吉远 王国强[1,2] 赵国斌 计波[1,2] 李向民 谢从瑞 彭璇[1] YU Jiyuan;WANG Guoqiang;ZHAO Guobin;JI Bo;LI Xiangmin;XIE Congrui;PENG Xuan(Xi’an Center of China Geological Survey/Northwest China Center of Geosciences Innovation,Xi’an 710119,Shaanxi,China;Orogen Research Center of China Geological Survey,Xi’an 710119,Shaanxi,China)

机构地区：[1]中国地质调查局西安地质调查中心/西北地质科技创新中心,陕西西安710119 [2]中国地质调查局造山带地质研究中心,陕西西安710119

出　　处：《西北地质》2024年第5期224-231,共8页Northwestern Geology

基　　金：中国地质调查局项目“中大比例尺地质图数据整合与接图”(DD20242292)、“公婆泉地区1:5万区域地质调查”(DD20243411);国家自然科学基金项目“中天山构造带阿拉塔格环状杂岩体成因研究”(41202045);陕西省基金项目“红柳河蛇绿岩地幔属性与深部岩浆演化”(2023-JC-YB-233)、“北祁连中段早古生代俯冲-增生杂岩岩石组成与构造研究”(2022JM-165)联合资助。

摘　　要：甘肃北山大豁落地区出露的白云山组是一套板岩、砂岩、砂砾岩、砾岩,局部夹灰岩的一套碎屑岩组合,由于缺乏地层学依据而被划归奥陶纪锡林柯博组(硅质岩为主,夹灰岩、砂岩、砂砾岩组合的一套浅海相沉积)。通过野外路线地质调查和剖面实测,在白云山组灰岩夹层中获得了保存较好的牙形刺化石,分别为大围刺Periodon grandis、原潘德尔刺(未定种)Protopanderodus sp.、镰箭(未定种)Drepanoistodus sp.、刺形刺(未定种)Spinodus sp.、小剑刺(未定种)Scabbardella sp.,将该套岩石组合时代限定为晚奥陶世。综合岩石组合特征、沉积层序与沉积相分析,认为白云山组形成于山前前陆盆地环境,预示着在晚奥陶世北山地区已进入初始造山阶段,为完善北山地层格架提供重要依据。The Baiyunshan Formation exposed in the Dahuoluo area of Beishan,Gansu Province is a set of clastic rock assemblages of slate,sandstone,glutenite,conglomerate,and locally intercalated limestone.Due to the lack of stratigraphic basis,it is classified as the Ordovician Xilinkebo Formation(a set of shallow marine sediments dominated by siliceous rocks,intercalated with limestone,sandstone and glutenite).Through field route geological survey and profile measurement,well-preserved conodont fossils have been obtained in the limestone interlayer of the Baiyunshan Formation.They are Periodon grandis,Protopanderodus sp.,Drepanoistodus sp.,Spinodus sp.,Scabbardella sp.,and the age of the rock assemblage is limited to the Late Ordovician.Based on the analysis of rock assemblage characteristics,sedimentary sequence and sedimentary facies,it is considered that the Baiyunshan Formation was formed in the piedmont foreland basin environment,indicating that the Beishan area has entered the initial orogenic stage in the Late Ordovician,which provides an important basis for improving the stratigraphic framework of Beishan.

关 键 词：牙形刺 白云山组 沉积层序与沉积相 晚奥陶世 北山造山带 

分 类 号：P52[天文地球—古生物学与地层学]