1. Introduction South China is an internationally significant region for the study of Upper Ordovician stratigraphy, having been selected as the site of the Global Boundary Stra- totype Section and Point (GSSP) for the base of the Hirnantian Series, at the Wangjiawan section near Yichang, western Hubei (Chen et al. 2006). High-reso- lution correlation of Hirnantian strata is vitally impor- tant for a better understanding of the end-Ordovician mass extinction event that was associated with exten- sive global cooling and glaciation. In South China, the Hirnantia fauna-bearing Kuanyinchiao Formation, which is interpreted as representing cool-water carbon- Newsletters on Stratigraphy, Vol. 48/3 (2015), 241–252 Article Published online June 2015; published in print August 2015 Late Hirnantian (latest Ordovician) carbonate rocks and shelly fossils in Shiqian, northeastern Guizhou, Southwest China Guangxu Wang 1 , Renbin Zhan 1 , Ian G. Percival 2 , Bing Huang 1 , Yue Li 3 , and Rongchang Wu 3 With 7 figures Abstract. The Kuanyinchiao Formation has generally been regarded as representing the only carbonate sediments deposited during the Hirnantian (Late Ordovician) interval in South China, where the Hirnantian GSSP is situated. Reinvestigation of several key Ordovician–Silurian boundary sections in Shiqian, north- eastern Guizhou Province, Southwest China, reveals a lithologically distinct carbonate unit with abundant shelly fossils, including tabulate and rugose corals, conodonts, brachiopods, trilobites and stromatoporoids, many showing close Silurian affinities and suggesting a level stratigraphically much higher than the Kuanyin- chiao Formation. This observation, together with further evidence that graptolites indicative of the Akido- graptus ascensus biozone are present in immediately overlying rocks at a nearby section, implies that these shelly fossiliferous strata are of latest Hirnantian age (possibly straddling the Ordovician – Silurian boundary). Hence they were most likely deposited after the Hirnantian glaciation, rather than representing glacial cool water sediments (the Kuanyinchiao Formation) as was previously thought. Ordovician – Silurian boundary se- quences in South China typically reflect global glacio-eustatic sea-level changes. Owing to their unique lithol- ogy and palaeontology, these newly recognized carbonate rocks, here formally named the Shiqian Formation, add substantially to our knowledge of Ordovician – Silurian stratigraphy in this region. Key words. Hirnantian, Ordovician, Carbonates, Glaciation, Fossils, South China © 2015 Gebrüder Borntraeger, Stuttgart, Germany DOI: 10.1127/nos/2015/0062 www.borntraeger-cramer.de 0078-0421/2015/0062 $ 3.00 Authors’ addresses: 1 State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Acad- emy of Sciences, Nanjing 210008, China. E-Mail: gxwang@nigpas.ac.cn, rbzhan@nigpas.ac.cn, bhuang@nigpas.ac.cn 2 Geological Survey of New South Wales, 947-953 Londonderry Road, Londonderry, NSW 2753, Australia. E-Mail: ian.percival@trade.nsw.gov.au 3 Key Laboratory of Economic Stratigraphy and Palaeogeography, Nanjing Institute of Geology and Palaeontology, Chi- nese Academy of Sciences, Nanjing 210008, China. E-Mail: yueli@nigpas.ac.cn, rcwu@nigpas.ac.cn Corresponding author: Guangxu Wang eschweizerbart_xxx