扬子台地西缘奥陶纪末赫南特期地层划分对比与古地理  

Hirnantian(latest Ordovician)Stratigraphy and Palaeogeography of the Western Yangtze Platform,South China

作　　者：王光旭[1,2] 魏鑫 崔雨浓 张小乐 王骞[1,2,4] 詹仁斌 WANG Guangxu;WEI Xin;CUI Yunong;ZHANG Xiaole;WANG Qian;ZHAN Renbin(State Key Laboratory of Palaeobiology and Stratigraphy,Nanjing Institute of Geology and Palaeontology,Chinese Academy of Sciences,Nanjing 210008,China;Center for Excellence in Life and Paleoenvironment,Chinese Academy of Sciences,Nanjing 210008,China;The Key Laboratory of Orogenic Belts and Crustal Evolution,Ministry of Education,School of Earth and Space Sciences,Peking University,Beijing 100871,China;University of Chinese Academy of Sciences,Beijing 100049,China)

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,南京210008 [2]中国科学院生物演化与环境卓越创新中心,南京210008 [3]北京大学地球与空间科学学院造山带与地壳演化教育部重点实验室,北京100871 [4]中国科学院大学,北京100049

出　　处：《高校地质学报》2023年第2期298-315,共18页Geological Journal of China Universities

基　　金：国家自然科学基金(42072007);现代古生物学和地层学国家重点实验室(20191102,213123);中国科学院青年促进会(2020311)联合资助。

摘　　要：华南上扬子区是奥陶纪末生物大灭绝研究的经典地区之一,但由于交通等因素,该区西缘(今昆明—西昌—成都之间)赫南特期浅水相沉积的时空分布规律仍不清楚。文章通过总结近年来的调查新成果与已发表资料,系统分析了研究区赫南特期地层划分对比和古地理,并取得一些新认识。在赫南特早期,研究区以含较凉水壳相动物群(TBF 1)的泥灰岩、灰岩发育为特色,统归入观音桥组(近岸相仅包含其下部)。赫南特中期开始发生明显的相带分异:近岸一侧广泛发育一套含暖水壳相动物群(TBF 2)的生物碎屑灰岩,归于观音桥组上部,向远岸一侧相变为黑色笔石页岩(龙马溪组底部)。至赫南特晚期,近岸的少数地区(如镇雄北部)以产出暖水壳相动物群(TBF 3)的粗碎屑沉积为特色,创名尾坝组;远岸一侧与前一时期类似,以龙马溪组底部黑色页岩沉积为代表。文章还通过综合已知数据,分别对区内赫南特早—中期和晚期古地理进行高精度重建。Hirnantian(latest Ordovician)rocks and fossils have still not been sufficiently documented in the western Yangtze region of South China(today’s southwestern Sichuan and northeastern Yunnan provinces,Southwest China).Compilation of published and new data results in refined Hirnantian stratigraphy and palaeogeography of the region.The lower Hirnantian is typified by the dark-grey cacareous mudstone or argillaceous limestone of the Kuanyinchiao Formation yielding cool-water Transitional Benthic Fauna 1(TBF 1).The middle Hirnantian strata,however,can be grouped into a near-shore lithofacies belt with distinctive grainstones of the upper Kuanyinchiao Formation yielding warm-water TBF 2,and a more offshore belt characterized by black shales of the basal Lungmachi Formation.A similar facies differentiation occurs in the upper Hirnantian of the region,but the near-shore sediments are in places represented by TBF 3-bearing calcareous siltstones,for which a new lithostratigraphic unit,the Weiba Formation,is proposed.On this basis,refined Hirnantian paleogeographic reconstructions of the western Yangtze Platform are presented.

关 键 词：地层学 古地理 奥陶纪 赫南特期 扬子台地西缘 

分 类 号：P535[天文地球—古生物学与地层学]