贵州印江三合场剖面志留纪晚期地层研究:兼论黔东北—渝东—湘西地区小溪组分布和第三套红层特征  

UPPER SILURIAN SUCCESSION AT THE SANHECHANG SECTION,YINJIANG,GUIZHOU PROVINCE AND ITS IMPLICATIONS TO THE SPATIAL DISTRIBUTION OF THE XIAOXI FORMATION AND THE LITHOLOGY OF THE THIRD RED BEDS IN THE QIAN–YU–XIANG BORDER REGION

作　　者：王棫萱 张小乐[2] 王凯 陈中强 WANG Yu Xuan;ZHANG Xiao Le;WANG Kai;CHEN Zhong Qiang(School of Earth Sciences,and State Key Laboratory of Biogeology and Environmental Geology,China University of Geosciences,Wuhan 430074;Nanjing Institute of Geology and Palaeontology,Chinese Academy of Sciences,Nanjing 210008;University of Chinese Academy of Sciences,Nanjing 211135)

机构地区：[1]中国地质大学(武汉)地球科学学院,生物地质与环境地质国家重点实验室,湖北武汉430074 [2]中国科学院南京地质古生物研究所,江苏南京210008 [3]中国科学院大学南京学院,江苏南京211135

出　　处：《地层学杂志》2024年第2期115-123,共9页Journal of Stratigraphy

基　　金：国家自然科学基金(42172003);科技部重点研发项目(2022YFF0800202)共同资助。

摘　　要：志留系海相碎屑红层在华南扬子区尤为发育,野外易于识别,主要发育3套。其中,第三套红层(罗德洛统上部至普里道利统下部)的地理分布并不清楚,前人报道的这套红层主要分布于志留纪晚期扬子台地的周缘沉积区,而在其内部沉积区却鲜有报道,其具体发育特征和分布范围缺乏实证。本文以贵州印江三合场剖面志留纪晚期地层研究为基础,综合黔东北—渝东—湘西地区多条剖面的研究结果,探讨该地区小溪组的分布范围及第三套红层的时空分布特征。三合场剖面志留系上部的小溪组以发育砂岩、泥质粉砂岩为特征,夹少量泥岩,其中8层红色薄层沉积格外醒目。依据发育大型虫管遗迹化石、线形植物和植物类表皮等化石层位的地层对比,笔者推测,该剖面小溪组的地层年代为罗德洛晚期至普里道利早期,与台地周缘区四川广元地区车家坝组、云南曲靖地区关底组及台地内部的小溪组属于同期沉积。与扬子区的第一、二套红层和周缘区第三套红层相比,黔东北—渝东—湘西地区第三套红层发育不好,局限于部分剖面,红层厚度亦较薄。本文认为,导致红层发育因地而异的主要原因是,形成红层的陆源碎屑供给量减少,以及古水深差异造成区域上古海洋氧化还原条件分异。The Silurian marine clastic red beds in the Yangtze region are an important component and characteristic of the Silurian system in South China,whose three sets of red beds are conspicuous and serve as important correlation markers in the field.Among them,the third set(upper Ludlow to lower Pridoli)has been reported only from the sedimentary regions around but inside the Yangtze Platform.Although the third red bed is reported occasionally from the interior of the Yangtze Platform,its lithologic features and spatiotemporal distributions remains poorly understood.The Sanhechang section in the Yinjiang County,Guizhou Province,SW China provides a window to explore the spatiotemporal distribution of the Xiaoxi Formation and the lithologic characteristics of the third red bed in the northeastern Guizhou–eastern Chongqing–western Hunan border region.The Xiaoxi Formation in the Sanhechang section is comprised of sandstones,argillaceous siltstones,and a few mudstones,with eight thin red layers.The occurrence of large trace fossils,cuticle-like phytodebris,and the remains of nematophyte fossils in the formation suggests the late Ludlow to early Pridoli in age.The Xiaoxi Formation is correlative to the Chejiaba Formation in the Guangyuan area of Sichuan Province,the Guandi Formation in the Qujing area of Yunnan Province,and the Xiaoxi Formation in the Yinjiang area of Guizhou Province.Compared with the first and second red beds in the Yangtze region,and the third red bed in the surrounding areas of the Yangtze Platform,the third red bed in the border region we studied here is limited in spatiotemporal distribution and is thin in thickness.The remarkable differences of this third red bed from others are likely due to the insufficient supply of terrigenous debris,and unique redox condition related to water depth where the red beds formed.

关 键 词：志留纪晚期 小溪组 时空分布 第三套红层 贵州 

分 类 号：P534.43[天文地球—古生物学与地层学]