Microbial–algal community changes during the latest Permian ecological crisis: Evidence from lipid biomarkers at Cili, South China Genming Luo a, b , Yongbiao Wang b , Kliti Grice c , Steve Kershaw d , Thomas J. Algeo e , Xiaoyan Ruan f , Hao Yang a , Chengling Jia b , Shucheng Xie a, ⁎ a State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, People's Republic of China b State Key Laboratory of Geological Processes and Mineral resources, China University of Geosciences, Wuhan 430074, People's Republic of China c WA-Organic and Isotope Geochemistry Centre, Department of Chemistry, Curtin University, Perth, WA 6845, Australia d Institute for the Environment, Brunel University, Uxbridge, Middlesex, UB8 3PH, UK e Department of Geology, University of Cincinnati, Cincinnati, OH 45221-0013 USA f Faculty of Earth Resources, China University of Geosciences, Wuhan 430074, People's Republic of China abstract article info Article history: Received 12 November 2011 Received in revised form 13 October 2012 Accepted 30 November 2012 Available online 8 December 2012 Keywords: microbialite P–Tr boundary mass extinction n-alkanes steranes dibenzofuran Microbialites flourished globally immediately following the latest Permian mass extinction. In this study, lipid biomarker records were analyzed in the Cili section (Hunan Province, South China) in order to determine the types of microbes involved in microbialite formation and their response to contemporaneous environmental changes. Various biomarkers were identified in the aliphatic and aromatic fractions using gas chromatography (GC) and GC–mass spectrometry (GC–MS). Low abundance of steranes in the microbialite layer suggests that it did not contain large amounts of algae, in striking contrast to the abundant algal fossils and algal-derived steranes present in the underlying (pre-crisis) skeletal limestone. Although pristine/phytane (Pr/Ph) ratios increased in the microbialite layer, covariation of Pr/Ph with the ratio of low- to high-molecular-weight n-alkanes (C 20- /C 20+ ) suggests that the former proxy was controlled by microbial (particularly cyanobacterial) inputs rather than by redox conditions. The microbialite also yielded low ratios of hopanes to short-chain n-alkanes (HP/Lalk) and high abundances of C 21 n-alkylcyclohexane, indicating that, in addition to cyanobacteria, anaerobic bacteria, archaea, and possibly acritarchs flourished in the aftermath of the marine extinction event. The upper part of the thinly bedded micritic limestone overlying the microbialite exhibits a bimodal distribution of n-alkanes as well as increased abundances of extended tricyclic terpanes and steranes, suggesting a return of habitable shallow-marine conditions for eukaryotic algae several hundred thousand years after the latest Permian mass extinction. Increases in the dibenzofuran ratio (i.e., DBF/(DBF+DBT+F)) and in the coronene to phenanthrene ratio (Cor/P) in the skeletal limestone immediately below the microbialite are evidence of enhanced soil erosion rates and wildfire intensity, marking the collapse of terrestrial ecosystems. The terrestrial crisis thus slightly preceded the marine biotic crisis in the South China region, to which it may have been a major contributing factor. © 2012 Elsevier B.V. All rights reserved. 1. Introduction The largest mass extinction of the Phanerozoic occurred at the ~252-Ma Permian–Triassic (P–Tr) boundary, eliminating ~ 90% of inver- tebrate species in the ocean and ~70% of vertebrate families on land (Retallack, 1995; Jin et al., 2000; Erwin et al., 2002). The ensuing recov- ery of marine ecosystems lasted ~3 to 5 Myr (Bottjer et al., 2008; Song et al., 2011; Chen and Benton, 2012). Large perturbations of the carbon, sulfur, and nitrogen cycles characterized this extended crisis interval (Newton et al., 2004; Korte and Kozur, 2010; Luo et al., 2010a, 2010b, 2011a, 2011b). During the immediate post-extinction interval, shallow carbonate platform settings accumulated microbialites exhibiting a variety of fabrics, including layered stromatolites, dendrolites, thrombolites and oncolites (Kershaw et al., 1999; Lehrmann, 1999; Lehrmann et al., 2003; Wang et al., 2005; Pruss et al., 2006; Baud et al., 2007). Although calcified microbialites were common throughout the Precambrian (Grotzinger and Knoll, 1999), they flourished only spo- radically during the Phanerozoic (Riding and Liang, 2005), primarily as ‘disaster taxa’ in conjunction with mass extinction events such as that at the P–Tr boundary but also in environments with limited grazing pres- sure from metazoans (Logan et al., 1974; Moore and Burne, 1994). Microbialites are formed by microbial communities through trap- ping and binding of sediment in combination with biotically cata- lyzed cementation (Riding, 2000). Based on petrographic study, the Global and Planetary Change 105 (2013) 36–51 ⁎ Corresponding author. E-mail address: xiecug@163.com (S. Xie). 0921-8181/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.gloplacha.2012.11.015 Contents lists available at SciVerse ScienceDirect Global and Planetary Change journal homepage: www.elsevier.com/locate/gloplacha