Quantitative stratigraphy of the Wufeng and Lungmachi black shales and graptolite evolution during and after the Late Ordovician mass extinction Junxuan Fan a, ⁎, Qing Chen a,b,c , Michael J. Melchin b , H. David Sheets d , Zhongyang Chen a,c , Linna Zhang a,b,c , Xudong Hou a a State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, PR China b Department of Earth Sciences, St. Francis Xavier University, Antigonish, NS B2G 2W5, Canada c Graduate University of Chinese Academy of Sciences, Beijing 100049, PR China d Department of Geology, University at Buffalo, SUNY, 411 Cooke Hall, Buffalo, NY 14260-4600, USA abstract article info Article history: Received 5 May 2013 Received in revised form 16 July 2013 Accepted 1 August 2013 Available online 13 August 2013 Keywords: Quantitative stratigraphy Rarefaction Late Ordovician mass extinction South China Graptolites Graptolite-bearing black shales are widely distributed on the Yangtze Platform in South China. Based on 19 sec- tions systematically studied recently, we conducted a quantitative stratigraphic analysis of the graptolite biodi- versity change during and after the Late Ordovician mass extinction. The combination of graphic correlation and rarefaction methods make it possible to evaluate the effect of sampling intensity on biodiversity estimates. Graptolite diversity reached its peak in the Dicellograptus complexus Chron, and then a gradual decline to the P. pacificus Chron. It was followed by a two-step mass extinction, the first and major phase occurred in the Metabolograptus extraordinarius Chron, and the second and minor phase in the latest M. persculptus Chron. The second phase of the extinction was mostly represented by the elimination of the Diplograptina survivors from the major extinction event, but did not show significant decline in standardized diversity curve. Thereafter, a moderate increase in richness appeared in the early and mid Parakidograptus acuminatus Chron, which was followd by a considerable decrease of graptolite richness in the late P. acuminatus Chron and early C. vesiculosus Chron. The present study also indicates slow and uneven sedimentation rates in the studied sections from mid-Katian to early Rhuddanian, including a relatively slower sedimentation rate during the Hirnantian Epoch. The latter, and the hiatus at the Honghuayuan and Guanwu sections, probably reflect the effects of the Hirnantian glaciation and regional tectonic movements. © 2013 Elsevier B.V. All rights reserved. 1. Introduction The Late Ordovician mass extinction, the second largest (in terms of species lost) of the five major events in the Phanerozoic, is estimated to have eliminated 86% of species (Jablonski, 1991). Recent studies from South China also indicate that this event eliminated at least 75% of gen- era of marine animals (Rong et al., 2007). The patterns and processes of mass extinction of graptolites (Chen et al., 2004a, 2005a; Fan and Chen, 2007) have been described based on high-resolution sampling in South China and quantitative biostratigraphic methods. However, there are still several key issues to be addressed, one of which is the effect of sam- pling intensity on the diversity curves, and the second is the patterns and processes of graptolite recovery from the mass extinction. When we conducted the analyses published in 2005 and 2007 (Chen et al., 2005a; Fan and Chen, 2007), the graptolite fauna in lower Rhuddanian strata in South China had not yet been systematically studied (see p. 84, Fan and Chen, 2007), so we were unable to make meaningful interpreta- tions of graptolite evolution in the early Rhuddanian, even though the curves were already extended into that interval. In the present paper, we present data from 19 late Katian–Rhuddanian sections from South China as a composite section. The graptolite faunas from late Katian to early Rhuddannian have been systematically studied and described by Chen et al. (2005b) and the present authors, and the recent systematic work by Štorch et al. (2011) and Melchin et al. (2011) is utilized in the present study as well. We also make significant improve- ments to a program for graphic correlation, SinoCor, so that we can con- duct the compositing more efficiently (Fan et al., in review). The new program also provides some useful analytical functions, such as calibrat- ing both the composite and the 19 individual sections to a geochronologic scale, generating a taxonomic richness curve based on the composite or calibrated composite, and creating a fence diagram showing the correla- tion between the composite and the individual sections. We also design a new method to run rarefaction analysis based on the 19 calibrated sections. Palaeogeography, Palaeoclimatology, Palaeoecology 389 (2013) 96–114 ⁎ Corresponding author. Tel./fax: +86 25 83282148. E-mail address: fanjunxuan@gmail.com (J. Fan). 0031-0182/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.palaeo.2013.08.005 Contents lists available at ScienceDirect Palaeogeography, Palaeoclimatology, Palaeoecology journal homepage: www.elsevier.com/locate/palaeo