新疆乌什地区奥陶系两个新建岩石地层单位  

TWO NEW ORDOVICIAN LITHOSTRATIGRAPHIC UNITS IN WUSHI COUNTY,XINJIANG,CHINA

作　　者：张雨晨 唐鹏[1] 黄智斌[3] 罗正江 龚方怡 杨果[3] 张小乐 崔雨浓 朱莉叶 王怿[1] 詹仁斌[1,2] ZHANG Yu Chen;TANG Peng;HUANG Zhi Bin;LUO Zheng Jiang;GONG Fang Yi;YANG Guo;ZHANG Xiao Le;CUI Yu Nong;ZHU Li Ye;WANG Yi;ZHAN Ren Bin(State Key Laboratory of Palaeobiology and Stratigraphy,Nanjing Institute of Geology and Palaeontology,Chinese Academy of Sciences,Nanjing 210008;University of Chinese Academy of Sciences,Beijing 100049;Exploration and Development Research Institute,Tarim Oilfield Company,PetroChina,Korla 841000;Research Institute of Experiment and Detection,PetroChina Xinjiang Oilfield Company,Karamay 834000)

机构地区：[1]中国科学院南京地质古生物研究所,现代古生物学和地层学国家重点实验室,江苏南京210008 [2]中国科学院大学,北京100049 [3]中国石油塔里木油田分公司勘探开发研究院,新疆库尔勒841000 [4]中国石油新疆油田分公司实验检测研究院,新疆克拉玛依834000

出　　处：《地层学杂志》2023年第4期416-430,共15页Journal of Stratigraphy

基　　金：中国科学院战略性先导科技专项B类(XDB26000000);国家自然科学基金(42202021、41872035、41972011、41172012)共同资助。

摘　　要：塔里木盆地西北缘乌什县城东南出露的晚奥陶世碎屑岩地层惯称为柯坪塔格组,但其地层序列、厚度、沉积时代和化石面貌等特征与柯坪地区的柯坪塔格组差别甚大,宜另建新组。对于这段地层,本文新建两个岩石地层单位,分别是亚科瑞克组和亚巴格组。亚巴格组由3条剖面拼接而成,分别为亚巴格剖面、斯代剖面及蒙达勒克剖面,指定亚巴格剖面为正层型,斯代剖面和蒙达勒克剖面为副层型。亚科瑞克组主要为铁红色含砾粉砂岩和钙质细砂岩,时代为凯迪早期,与下伏的“丘里塔格群”呈不整合接触,亚巴格剖面为层型。亚巴格组的时代为凯迪中—晚期,分为两段:下段为灰绿色厚层钙质细砂岩、粉砂岩,产牙形类;上段为不等厚韵律互层的灰绿色钙质泥质粉砂岩和钙质粉砂岩,夹薄层砂岩或生物碎屑灰岩,产笔石、腕足类、珊瑚、牙形类、几丁虫等。亚巴格组与下伏的亚科瑞克组呈整合接触,与上覆石炭纪蒙达勒克组呈角度不整合接触。A sequence of thick Late Ordovician clastic strata is exposed in Wushi County in the northwestern margin of the Tarim Basin.This sequence was previously recognized as the Kalpintag Formation,which however is very different from the stratotype of the Kalpintag Formation in terms of its lithology,thickness,age,as well as fossil assemblage.In this study,two new lithostratigraphic units(i.e.,the Yakrik Formation and the Yabage Formation)are proposed based on stratotypes outcropped at three sections(i.e.,the Yabage Section,the Sidai Section,and the Mengdaleke Section).The Yakrik Formation refers to a sequence of reddish pebble-bearing siltstone and calcareous fine-grained sandstone with a thickness of 84 m,which overlies unconformably the“Qiulitage Group”.Conodonts from this formation are assigned to the lower part of the Belodina confluens Biozone,indicating an early Katian age of the Late Ordovician.The Yabage Formation,with a measurable thickness of 2800.7 m,overlies conformably the Yakrik Formation and is covered by Cenozoic deposits.The Yabage Formation is divided into two members(i.e.,the Lower Member and the Upper Member ascendingly).The Lower Member represents a sequence of greenish thick-bedded calcareous siltstone and sandstone while the Upper Member is typified by a sequence of greenish calcareous siltstone and argillaceous siltstone with some thin-bedded bioclastic wackstone interbeds.Different fossils,e.g.graptolites,brachiopods,corals,conodonts and chitinozoans,are recorded from the Yabage Formation.Conodonts from the Lower Member are assigned to the upper part of the Belodina confluens Biozone and the Aphelognathus pyramidalis Biozone,suggesting a middle Katian age.Graptolites and chitinozoans discovered from the Upper Member are attributed to the Dicellograptus complanatus Biozone and the Eisenackitina ripae Biozone respectively,suggesting a late Katian age.Brachiopod Altaethyrella Fauna is recorded at the top of the Upper Member.Late Ordovician lithofacies and biofacies in Wushi area are distincti

关 键 词：亚科瑞克组 亚巴格组 上奥陶统 凯迪阶 生物地层 新疆乌什县 

分 类 号：P534.42[天文地球—古生物学与地层学]