Vol. 29 No.3 September 2006

Journal of International Geoscience

Published by the International Union of Geological Sciences

by Xu Chen ¹, Jiayu Rong¹, Junxuan Fan¹, Renbin Zhan ¹, Charles E. Mitchell², David
A.T. Harper³, Michael J. Melchin⁴, Ping'an Peng⁵, Stan C. Finney⁶, and Xiaofeng Wang⁷

The Global Boundary Stratotype Section and
Point (GSSP) for the base of the Hirnantian Stage
(the uppermost of the Ordovician System)

1. State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, 39 East Beijing Road, Nanjing 210008, China. E-mails: xu1936@yahoo.com; jyrong@nigpas.ac.cn; fanjuanxuan@yahoo.com; rbzhan@nigpas.ac.cn
2. Department of Geology, the State University of New York at Buffalo, NY 14260-3050, USA. E-mail: cem@geology.buffalo.edu
3. Geological Museum, University of Copenhagen, Øster Voldgade 5-7, DK-1350 Copenhagen, Denmark. E-mail:dharper@savik.geomus.ku.dk
4. Department of Earth Sciences, St. Francis Xavier University, Antigonish, N.S. B2G 2W5, Canada. E-mail: mmelchin@stfx.ca
5. State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640,China. E-mail: pinganp@gig.ac.cn
6. Department of Geological Sciences, California State University at Long Beach, Long Beach, CA 90840, USA. E-mail: scfinney@csulb.edu
7. Yichang Institute of Geology and Mineral Resources, 21 Gangyao Road, Yichang 443003, China. E-mail: ycwxiaofeng@yahoo.com.cn

Abstract

 The Global boundary Stratotype Section and Point (GSSP) for the base of the Hirnantian Stage (the uppermost of the Ordovician System) is defined at a point 0.39m below the base of the Kuanyinchiao Bed in the Wangjiawan North section. The section is located near Wangjiawan village, 42 km north of Yichang city (western Hubei, China), at 30o 58’56”N and 111o 25’10”E. The GSSP level coincides with the first appearance of the graptolite species Normalograptus extraordinarius (Sobolevskaya). Secondary markers include the onset of a positive carbon-isotope excursion, and a slightly earlier first appearance of Normalograptus ojsuensis (Koren and Mikhailova). The Wangjiawan North section possesses continuity of sedimentation and biozonation with completeness of exposures, abundant and well-preserved graptolites and shelly fossils, i. e. the Hirnantia-Dalmanitina shelly fauna which is a key element for recognition of the Hirnantian Stage. The Wangjiawan North, South and Riverside sections possess favorable facies and widespread correlation potential, are free from structure complication, metamorphism and other alteration, and have good accessibility. The Riverside section in particular possesses amenability to isotopic age determination. The beginning of the Hirnantian was followed by a global episode of a major extinction event, which happened in the Diceratograptus mirus Subzone. The proposal was voted by the International Subcommission on Ordovician Stratigraphy in October, 2004, approved by the International Commission on Stratigraphy in February, 2006, and ratified by the International

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