• 责任者：Wang Yi (State Key Laboratory of Palaeobiology and Stratigraphy ; Nanjing Institute of Geology and Palaeontology ; Chinese Academy of Sciences ; Nanjing 210008 ; China) ; Rong Jiayu
• 刊名：Journal of Stratigraphy
• 出版年：2013
• 卷期：37(3)
• 关键词：奥陶纪 ; Ordovician ; 志留纪 ; Silurian ; 地层界线 ; stratigraphic boundary ; 湖北 ; Hubei Province
• 页码：p.264-274
• 图表：illus., 35 refs.
• 分类号：1200
• issnNo：ISSN0253-4959
• isbnNo：CN32-1187/P

     Investigation on eight Ordovician-Silurian boundary sections in Wufeng, Hefeng, Yidu and Changyang counties, southwestern Hubei Province, shows that there is a hiatus between the Upper Ordo- vician and the lower Silurian in this region, which is solid evidence of the Yichang Uplift. This hiatus oc- curred between the late Ordovician Paraorthograptus pacificus Zone and the early Silurian Coronograptus cyphus Zone, missing at least four graptolitic biozones, including the Normalograptus extraordinarius Zone, Normalograptus persculptus Zone, Akidograptus ascensus Zone and Parakidograptus acuminatus Zone. At some sections, the top two to three biozones of upper Katian （Late Ordovician） are also missing including the P. pacificus Zone, the Dicellograptus complexus Zone and part of the D. complanatus Zone. The longest hiatus at the Xiaohe Village, Wufeng County, where the middle Aronian Demirastrites convolutus Zone directly and disconformably overlies the lower-middle Katian D. complanatus Zone with more than 10 graptolitic biozones missing. There are three kinds of contacts between the Ordovician and the Silurian in the study area. In Type A contact, a disconformity is developed between the Wufeng and Lungmachi formations. In Type B contact the Lungmachi Formation disconformably overlies the Linhsiang Formation. In Type C contact, a weathering crust occurs at the boundary between the Ordovician and Silu- rian. Based on our detailed investigation conducted in southwestern Hubei, the Yichang Uplift commenced at a time roughly corresponding to the upper P. pacificus Zone （the upper Wufeng Formation, -446 Ma）, and ended diachronously. At Panjiawan of Yidu County, the Yichang Uplift ended in the Cystograp- tus vesiculosus Zone （-442 Ma）, while at most other localities it ended in the C. cyphus Zone. The Xiao- he village of Wufeng County is the only locality where the Yichang Uplift lasted till the end of the D. conv- olutus Zone （-439 Ma）. So, the Yichang Uplift in southwestern Hubei lasted about 4-7 Ma. Analysis of kaolinite minerals and weathering residual of the Wufeng Formation in the ancient weathering shows that the Yichang Uplift caused subaerial emergence and weathering in the study area. The Uplift was probably connected with the western and northwestern movement of the Cathaysian Oldland during the Late Ordovi- cian and early Silurian. The movement was a major force driving the Yichang Uplift which had different manifestations （such as magnitude and duration） at different localities owing to the different paleogeo-graphic conditions.