GSA DATA REPOSITORY

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1 GSA DATA REPOSITORY Luo et al. Supplementary Information Geological Background The Taiping and Zuodeng sections outcrop in the deepwater Nanpanjiang Basin along the southern margin of the South China craton (Fig. DR1). Numerous low-relief carbonate banks appeared in the basin during the Late Permian and evolved into high-relief platforms during the Early Triassic (Lehrmann et al., 2003). The Taiping and Zuodeng sections are located in the interiors of the Pingguo and Debao platforms, respectively (Fig. DR1). The Upper Permian Heshan Formation consists of skeletal limestone and cherty skeletal limestone, containing typical uppermost Permian fusulinids including Nankinella, Spaerulina and Condofusulina (Fig. DR2a), as well as the conodont Hindeodus latidentatus (Wang et al., 1999). Overlying this unit is the basal member of the Majiaoling Formation, consisting of a microbialite facies containing few fossils (Lehrmann et al., 2003; Luo et al., 2010). The P-Tr boundary, as indicated by the first appearance of the conodont Hindeodus parvus, occurs in the lower part of the microbialite, about 1 m above the lithological boundary (Wang et al., 1999). Sedimentary and geochemical records indicate no deposition hiatus between the two lithology units (Lehrmann et al., 2003; Luo et al., 2010). The microbialite is overlain by thinly bedded limestone of the Majiaoling Formation. Most organisms disappear at the base of the microbialite. No distinct fossil can be found in thin sections of the microbialite except some some microorganisms including ostracods, microgastropods and microconchids (Yang et al., 2010). This infers that the lithology boundary between skeletal limestone and microbialite is supposed to be the main marine mass extinction boundary (Lehrmann et al., 2003), and thus the base of the microbialite can be correlated with the bed 25 in Meishan GSSP section. Some microbes (Fig. DR2b) in the microbialite are supposed to be cyanobacteria (Wang et al., 2005). Material and Methods Large (~2 kg), fresh samples were collected from the Taiping and Zuodeng sections. Weathered surfaces and large veins were trimmed off and each sample was cut into small pieces in the laboratory. Fresh chips were chosen, washed with deionized water, and crushed to less than 100 mesh. The samples were decalcified in 6 M HCl until all the carbonate was dissolved. The residue was rinsed with deionized water, centrifuged until neutral ph was achieved, and freeze dried for 24 hours. 13 C org was analyzed offline. About g of the residue, mixed with CuO, and Cu and one piece of Pt wire, was loaded into a quartz tube. The tube was then evacuated, sealed and combusted at 850 for 4 hours. The produced CO 2 was transferred cryogenically to another tube through a vacuum line. The CO 2 was analyzed using a MAT 253 isotope-ratio mass spectrometer. The data were reported relative to the Vienna Pee Dee belemnite (V-PDB) standard with a precision better than ±0.1 based on duplicate analyses. 15 N org was analyzed online using

2 an auto-sampler FlashEA 1112 HT interfaced with the MAT 253 with a precision better than ±0.3. About mg of the residue mixed with 2 mg V 2 O 5 was loaded into a clean tin cup. Every two samples were separated by a blank, and every three samples were followed by a standard (Glycine Standard from SIGMA, 15 N = ). CO 2 was removed by using Carbosorb, and water was extracted with anhydrous magnesium perchlorate. Isotopic data are reported as per mil ( ) relative to atmospheric N 2. Nitrogen Isotopes Nitrogen stable isotopes comprise 14 N and 15 N, accounting 99.6% and 0.4%, respectively. Nitrogen isotopic compositions are conventionally defined using standard delta notation, 15 N = 1000 * (R sample /R standard -1) where R represents the ratio of 15 N to 14 N in the sample and standard. The standard for nitrogen isotopic composition is atmospheric dinitrogen gas. Oceanic nitrogen isotopic compositions are controlled by the flux and isotopic compositions of nitrogen entering the ocean and the flux and isotopic compositions of nitrogen leaving the ocean. The principal inputs of nitrogen to the marine basin are by rain, rivers, lighting strikes and direct fixation of atmospheric N 2 by diazotrophic organisms, such as cyanobacteria. In the modern ocean, N 2 fixation is the primary source of fixed nitrogen (Garvin et al., 2009). The main sinks of oceanic nitrogen include denitrification, anaerobic ammonium oxidation (anammox) and burial of organic matter. The denitrification reduces NO - 3, or NO - 2 stepwisely to NO, N 2 O, and finally N 2, and the anammox reduces NO - 2 to N 2 through NH + 4 oxidation in anoxic environments. Because many processes during the transformations of nitrogen species have unique isotopic fractionations, the oceanic nitrogen isotopic compositions recorded in well-preserved ancient sediments can provide information about the evolution of the ancient N cycle. It is notable that isotopic fractionation during N 2 -fixation is very small, which is about 2 (Wada and Hattori, 1991). In the modern ocean, dissolved dinitrogen in seawater has quite constant isotopic composition around 0.5, so that the cellular nitrogen assimilated through the N 2 -fixation is located in a narrow and characteristic isotopic range from -2 to 0 (Minagawa and Wada, 1986). Contrast to N 2 -fixation, isotopic effect of denitrification and anammox is very large, with denitrification =+20 to +30 (Sigman and Casciotti, 2001). Theses result in a residual NO - 3 pool substantially enriched in 15 N. These residual fixed N upwelled into the surface ocean are always completely consumed by primary producers (Altabet, 1988). Although there is a large isotopic effect during the assimilation of nitrate (Wada and Hattori, 1991), completely utilization under most conditions excludes this effect. The relatively high positive 15 N, about +5, of organic matter in modern ocean is ascribed to these processes. However, when all the NO - 3 in the deep ocean are reduced to N 2 or the residual deep ocean NO - 3 can not be upwelled into the surface ocean, the 15 N of the organic matter will be characterized by nitrogen fixation, about -2 to 0. Hopanoids in the Microbialite Lipids compositions of the microbialite present after the end-permian mass extinction have been analyzed in three sections in South China. Abundant hopanoids were detected in these microbialites, including 18α(H)-22,29,30-trisnorhopane (Ts), 17α(H)-22,29,30-trisnorhopane (Tm),

3 C 29 to C 34 17α(H),21β(H)-hopanes (29-H to 34-H) and C 29 and C 30 17β(H),21α(H)-moretanes (βα-hopanes, 29-M and 30-M) (Fig. 5a). These hopanoids might be originated from cyanobacteria. However, 2-methylhopanes were below detection limit in all the microbialite samples analyzed until now (Fig. 5b). Figure DR1. Reconstructed Early Triassic paleogeographic map of the Nanpanjiang Basin, a deep-water basin containing several isolated carbonate platforms. The Taiping (TP) and the Zuodeng (ZD) sections were located on the Pingguo and Debao platforms, respectively. The conodont zones were from Lehrmann et al. (2003). The insert figure represents the Yangtze Block, and the location of the Meishan section referred in this paper is denoted by the star. Figure DR2. A) The fusulinids in the thin sections of Late Permian skeletal limestone which contains high abundance of fossils. B) Thin section of the microbialite presents lots of microbes

4 which are supposed to be cyanobacteria. These two thin sections are from the Zuodeng section. The two scale bars represent 0.1 mm. Figure DR3. Cross-plots showing the correlation of carbon isotope composition between carbonate ( 13 C carb ) and organic matter ( 13 C org ) in the Zuodeng and Taiping sections. The blue diamonds represent the samples from the underlying skeletal limestone and the overlying thinly bedded limestone. The red squares represent the samples from the microbialite layer. Strong positive correlations between 13 C carb and 13 C org indicate the dominant input of marine organics, which is consistent with other indicators. In the Zuodeng section, the microbialite samples are offset from the regression line defined by the underlying and overlying samples, supposed to be caused by some special microbes with different carbon isotope fractionation. Figure DR4. Profiles of carbonate content during the P-Tr transition in the Taiping and Zuodeng sections. The two samples with low carbonate content are cherty skeletal limestone.

5 Figure DR5. a: Mass chromatography with m/z=191 shows the distribution pattern of the hopanoids in earliest Triassic microbialite. b: Mass chromatography with m/z=205, indicating the abundance of 2-methylhopanes are below detection limit. Please see the text for abbreviation of the compounds. Table DR1. 15 N, 13 C carb, 13 C org, difference of carbon isotope composition ( 13 C carb - 13 C org ) and carbonate content in the Zuodeng and Taiping sections. 15 N 13 b C carb 13 C org Sample Thickness a Carbonate ( ) ( ) ( ) ( ) No. (cm) (wt %) Zuodeng section Zu Zu Zu Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z

6 Z Z Z Z Z Z Z Z Z Z Zd Zd Zd Zd Zd Zd Zd Zd Taiping section UT UT UT UT UT UT T T T T T T T T T T T T T T T T T T

7 T T TD TD TD TD TD TD TD TD TD a: minus means the samples are from the Late Permian skeletal limestone underlying the base of the microbialite; b: - means the samples are not analyzed. References Cited Altabet, M.A., 1988, Variations in nitrogen isotopic composition between sinking and suspended particles: implications for nitrogen cycling and particle transformation in the open ocean: Deep Sea Research Part A. Oceanographic Research Papers, v. 35, p , doi: / (88) Garvin, J., Buick, R., Anbar, A.D., Arnold, G.L., and Kaufman, A.J., 2009, Isotopic evidence for an aerobic nitrogen cycle in the Latest Archean: Science, v. 323, p , doi: /science Lehrmann, D.J., Payne, J.L., Felix, S.V., Dillett, P.M., Wang, H.M., Yu, Y.Y., and Wei, J.Y., 2003, Permian-Triassic boundary sections from shallow-marine carbonate platforms of the Nanpanjiang Basin, South China: Implications for oceanic conditions associated with the End-Permian extinction and its aftermath: Palaios, v. 18, p , doi: / (2003)18<138:PBSFSC>2.0.CO;2. Luo, G.M., Wang, Y.B., Yang, H., Algeo, T.J., Kump, L.R., Huang, J.H., and Xie, S.C., 2010, Stepwise and large-magnitude negative shift in d13ccarb preceded the main marine mass extinction of the Permian-Triassic interval: Palaeogeography Palaeoclimatology Palaeoecology, v. 299, p ,, doi: /j.palaeo Minagawa, M., and Wada, E., 1986, Nitrogen isotope ratios of red tide organisms in the East China Sea: a characterization of biological nitrogen fixation: Marine Chemistry, v. 19, p , doi: / (86) Sigman, D.M., and Casciotti, K.L., 2001, Nitrogen isotopes in the ocean: In, Steele, J.H., Turekian, K.K., and Thorpe, S.A., Eds., Encyclopedia of Ocean Sciences, London, Academic Press, pp Wada, E., and Hattori, A., 1991, Nitrogen in the sea: forms, abundances, and rate processes: Boca Raton, CRC Press. Wang, Y.B., Tong, J.N., Wang, J.S., and Zhou, X.G., 2005, Calcimicrobialite after end-permian mass extinction in South China and its palaeoenvironmental significance: Chinese Science Bulletin, v. 50, p , doi: /

8 Wang, X., Hao, W., Yang, S., and Liu, J., 1999, Stratigraphy and fusulinid fossils of the Upper Permian in Pingguo area, Guangxi, in Yao, A., Ezaki, Y., Hao, W., and Wang, X., eds., Biotic and Geological Developments in the Paleo-Tethys in China: Beijing, Peking University press, p Yang, H., Chen, Z.Q., Wang, Y., Tong, J., Song, H., Chen, J., Composition and structure of microbialite ecosystems following the end-permian mass extinction in South China: Palaeogeography, Palaeoclimatology, Palaeoecology, in press, doi: /j.palaeo