华南上扬子区下奥陶统红花园组顶界的穿时性  

PHENOMENAL DIACHRONEITY IN THE UPPER BOUNDARY OF THE LOWER ORDOVICIAN HUNGHUAYUAN FORMATION IN THE UPPER YANGTZE REGION , SOUTH CHINA

作　　者：廖翰卿[1] 刘建波[1,2,3] 吴荣昌[3] 孙永超[1] 詹仁斌[3] 

机构地区：[1]北京大学地球与空间科学学院,北京100871 [2]造山带与地壳演化教育部重点实验室(北京大学),北京100871 [3]现代古生物学和地层学国家重点实验室,中国科学院南京地质古生物研究所,南京210008

出　　处：《古生物学报》2013年第1期18-34,共17页Acta Palaeontologica Sinica

基　　金：国家自然科学基金(40972020,41272035,41290260);国家“创新研究群体”项目(41221001);现代古生物学和地层学国家重点实验室基金联合资助;IGCP591项目“早、中古生代生物事件”的阶段成果

摘　　要：在早奥陶世弗洛早期,广布于华南扬子台地的浅海碳酸盐台地沉积(红花园组)逐渐被陆源碎屑沉积所替代,而海洋生物分异度快速升高,随后出现了奥陶纪生物大辐射的第一次高潮。因此下奥陶统红花园组顶界附近的岩石地层学和年代地层学研究具有重要意义。目前该组顶界的穿时性及其横向分布规律尚无定论。通过对贵州桐梓红花园、习水吼滩、湖北兴山古洞口和湖南张家界温塘4个剖面红花园组牙形石动物群的系统分析,从下至上识别出了3个牙形石带,分别是Serratognathus diversus带、Prioniodus honghuayuanensis-Oepikodus communis带和Oepikodus evae带。采用统一的红花园组顶界定义,即以中—厚层亮晶颗粒灰岩的消失作为红花园组与上覆地层之间的界线,结合研究剖面和前人牙形石生物地层学资料,发现上扬子区红花园组顶界具有明显的穿时性,而且这种穿时性在空间上还具有一定的规律性。上扬子区红花园组顶界大部分位于P.honghuayuanensis-O.communis带内;从上扬子区中部向台地南北两侧的边缘区,红花园组顶界大体上逐渐升高至O.evae带;而在靠近陆源碎屑沉积的西部地区顶界则降低至S.diversus带。造成这一现象的主要控制因素除了海平面的升高外,可能还与陆源碎屑供应的增多有关。During early Floian （Early Ordovician） time, extensive shallow-marine carbonates （named the Hunghuayuan Formation） were deposited on the Yangtze platform, which were gradually replaced by the deposition of terrigenous clastics and mixed carbonate-siliciclastic sediments later. In the meantime, the hiodiversity of the marine biota increased rapidly, and reached its first aeme in the middle Floian. Thus, further studies on the lithostrati- graphic and chronostratigraphic successions of the upper Hunghuayuan Formation is necessary, as there are still some ongoing debates over its diachroneity. Diverse conodont faunas recovered from the studied sections （Honghuayuan of Tongzhi and Houtan of Xishui, northern Guizhou Province, Gudongkou of Xingshan, western Hubei Province, and Wentang of Zhangjiajie, northwestern Hunan Province） indicate that three conodont biozones could be recognized from the Hunghuayuan Forma-tion, i. e. , the Serratognathus diversus Biozone, the Prioniodus honghua yuanensis-Oepileodus communis Biozone, and the Oepikodus evae Biozone. The top of the Hunghuayuan Formation, marked by the vanishing surface of medium- to thick-bed- ded lime grainstones in the Upper Yangtze region is substantially diachronous from the S. diversus to the O. evae biozones. The upper boundary of the formation in most part of the Upper Yangtze platform is in the P. honghuayuanensis-O, communis Biozone. However, this part of the forma- tion gets progressively younger （in the O. evae Biozone） towards the northern and southern marginal areas of the Yangtze platform. The upper boundary of the formation on the western platform which is in close association to the depositional area of terrigenous clastics lies within the S. diversus Biozone. The spatial distribution of this phenome- nal diachroneity in the upper boundary of the Hunghuayuan Formation of the Upper Yangtze plat- form was possibly controlled by a rapid eustatic sea-level rise as well as an increase in the terrige- nous supply due to erosion from t

关 键 词：牙形石 红花园组 穿时 奥陶系 扬子区 地层 中国 

分 类 号：Q915[天文地球—古生物学与地层学]