Palaeoenvironmental change during the end-Guadalupian (Permian) mass extinction in Sichuan, China Xulong Lai a,b , Wei Wang c , P.B. Wignall d, ⁎, D.P.G. Bond d , Haishui Jiang a , J.R. Ali e , E.H. John d , Yadong Sun a a Faculty of Earth Sciences, China University of Geosciences, Wuhan, Hubei 430074, PR China b Laboratory of Biological and Environmental Geology, China University of Geosciences, Wuhan, Hubei 430074, PR China c Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences, 39 East Beijing Road, Nanjing 210008, PR China d School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK e Department of Earth Sciences, University of Hong Kong, Hong Kong, PR China abstract article info Article history: Received 8 February 2008 Received in revised form 10 July 2008 Accepted 9 August 2008 Keywords: Flood basalts Regression Mass extinction Permian The end-Guadalupian mass extinction has been investigated in Sichuan province, SW China. In the south of the province the platform carbonates of the Maokou Formation are overlain by the Emeishan flood basalts, a possible factor in the extinction event, and in the north of the province the formation is succeeded by shallow-marine carbonates of the Wuchiaping Formation (Late Permian). The extinction event is primarily recorded by the loss of fusulinaceans and possibly by species-level turnover amongst calcareous algae. The high-diversity, Middle Permian microfossil assemblages are last seen beneath a surface recording widespread emergence and karstification. In northern Sichuan emergence occurred early in the Capitanian Stage and the succeeding strata record restricted hypersaline deposition that preceded the deposition of a thick ash horizon, the Wangpo Bed. These mid-Capitanian arid conditions are replaced by humid conditions towards the end of the stage as indicated by the development of a widespread coal seam. In southern Sichuan only a thin development of this humid, coaly facies is seen developed atop the Maokou karstic surface and below the oldest flood basalt. The Guadalupian interval saw the development of large C isotope excursions in the carbonate record. These include a positive-then-negative swing late in the Capitanian and a newly discovered negative spike superimposed on an early Capitanian heavy interval. This spike may be a global phenomenon but the magnitude (8‰) may have been exaggerated by an increased contribution from light, respired C derived from soils during relative sea-level fall. A plethora of environmental factors approximately coincide with the extinction event, including regression, acidic volcanism and flood basalt volcanism making it difficult to unravel the relative significance of each. © 2008 Elsevier B.V. All rights reserved. 1. Introduction The end-Guadalupian mass extinction event is one of the most recently identified crises of the fossil record (Jin et al., 1994; Stanley and Yang, 1994; Retallack et al., 2005) and its cause remains poorly understood. Like all mass extinction events of the past 300 myr it closely coincides with the eruption of a large igneous province, in this case the Emeishan flood basalts of SW China (Wignall, 2001, 2005). However, the connection between this volcanism and the extinction losses is enigmatic and recent proposals suggest that the Emeishan- extinction link is mere coincidence (Isozaki et al., 2007a,b). This paper examines the relationship between these two phenomena in Sichuan Province, southwestern China. This is an ideal region to investigate the link because there are excellent exposures of Middle Permian (Guadalupian) and early Late Permian (Wuchiapingian) carbonate platform strata. These contain a good fossil record, particularly of shallow-water taxa that include the fusulinaceans, the group that suffered some of the most extreme extinction losses (Stanley and Yang,1994; Jin et al., 1994; Leven, 2003; Yang et al., 2004; Ota and Isozaki, 2006). In the south of the province the Guadalupian carbonates (Maokou Formation) are overlain by flood basalts that represent a relatively thin development of the lava pile on the northern margin of the main province. In this area the substantial facies changes that herald the onset of the volcanism are particularly well seen. 2. Aims and techniques Field-based sedimentary logging and detailed facies analysis was undertaken at Guadalupian–Lopingian boundary sections in both northern and southern Sichuan (Fig. 1). Carbonate facies classification and identification of the foraminiferal and calcareous algal fossil content was then achieved using a suite of thin sections. These groups provide a record of turnover around the end-Guadalupian interval and the former also provides some measure of biostratigraphic control. Palaeogeography, Palaeoclimatology, Palaeoecology 269 (2008) 78–93 ⁎ Corresponding author. E-mail address: wignall@earth.leeds.ac.uk (P.B. Wignall). 0031-0182/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.palaeo.2008.08.005 Contents lists available at ScienceDirect Palaeogeography, Palaeoclimatology, Palaeoecology journal homepage: www.elsevier.com/locate/palaeo