Biostratigraphic and Chemostratigraphic Correlation for the Base of the Middle Ordovician between Yichang and Western Zhejiang Areas, South China

• Published in: Acta geologica Sinica (Beijing) Vol. 85; no. 2; pp. 320 - 329
• Main Authors: ZHANG, Yuandong, MUNNECKE, Axel, CHEN, Xu, CHENG, Junfeng, LIU, Xiao
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01-04-2011; Wiley Subscription Services, Inc; State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Nanjing 210008, China%GeoZentrum Nordbayern, FG Palaoumwelt, University Erlangen-Nuremberg, D-91054 Erlangen, Germany%Research Institute of Petroleum Exploration and Development, East China Company, SINOPEC, Nanjing 210011, China
• Edition: English ed.
• Subjects: chemostratigraphy; Graptolite biostratigraphy; Isotopes; Middle Ordovician; slope facies; South China; 中国南方; 中奥陶统; 化学地层学; 宜昌; 浙江西部; 生物地层学; 相边界; 长江三峡地区; Middle Ordovician; chemostratigraphy; South China; Graptolite biostratigraphy; slope facies
• ISSN: 1000-9515; 1755-6724
• DOI: 10.1111/j.1755-6724.2011.00401.x

The base of the Middle Ordovician （i.e. Dapingian Stage） has been defined at the first appearance datum （FAD） of conodont Baltoniodus？ triangularis at Huanghuachang, Yichang, China,but the precise correlation of the boundary to regions of other facies remain to be resolved. Herein we review the biostratigraphy and chemostratigraphy of the Huanghuachang Global Standard Stratotype-Section and Point （GSSP） section, and present our latest stratigraphic work on the nearby Chenjiahe s ection in Yichang, and the Hengtang Quarry section, Jiangshan, Zhejiang, which is regarded as representative of slope facies. The conodont and graptolite biostratigraphy as well as chemostratigraphy of the Chenjiahe section indicate that the base of the Middle Ordovician also falls within the graptolite Azygograptus suecicus Zone, and coincides with a high or maximum δ13C value within a minor positive carbon isotope excursion, suggesting that the base boundary can be readily recognized across the entire Yangtze Gorges area. The integrated graptolite and conodont biostratigraphy and chemostratigraphy of the Hengtang section, Jiangshan, indicates that the basal boundary probably falls within the graptolite lsograptus caduceus imitatus Zone that overlies the Azygograptus suecicus Zone, and coincides with a remarkable drop of δ13C. This difference indicates that a multi-disciplinary approach is critical to identify the base boundary in those regions where the Baltoniodus ？ triangularis is absent.