Constraints on carbon accumulation rate and net primary production in the Lopingian (Late Permian) tropical peatland in SW China Hao Wang a,b , Longyi Shao a, ⁎, David J. Large c , Paul B. Wignall b a State Key Laboratory of Coal Resources and Safe Mining, College of Geosciences and Survey Engineering, China University of Mining and Technology (Beijing), China, 100083 b School of Earth and Environment, University of Leeds, UK, LS2 9JT c Faculty of Engineering, University of Nottingham, UK, NG7 2RD abstract article info Article history: Received 4 March 2010 Received in revised form 17 December 2010 Accepted 17 December 2010 Available online 23 December 2010 Keywords: Late Permian Lopingian peatland Southwestern China Milankovitch periodicity Carbon accumulation Net primary production (NPP) During the Permian, peatland, as represented in extensive coal deposits, was a major component of the global carbon cycle. Carbon storage in peatland is a balance between decay and net primary production (NPP), which in turn are sensitive to variations in the concentration of atmospheric CO 2 and O 2 . To evaluate peatland carbon storage and NPP during the Lopingian, a period thought to be characterised by higher atmospheric O 2 and CO 2 than modern levels, spectral analyses of geophysical data from a 15.1 m thick Lopingian (Upper Permian) coal in southwestern China were conducted to define the time frame of temporal carbon accumulation in tropical peatland. The result shows that the mineral matter content (ash yield) of the coal was possibly influenced by 123 ka (eccentricity), 35.6 ka (obliquity) and 21.2 ka (precession) Milankovitch periodicities. Using this timeframe and an understanding of carbon loss during coalification, the Lopingian tropical peatland carbon accumulation rate is calculated to be 61.1–73.0 g C/m 2 /yr which is expected to correspond to a NPP of 611– 1460 g C/m 2 /yr respectively. A comparison between the predicted Pennsylvanian (Late Carboniferous) NPP and modern values indicates that the Permian NPP calculated is consistent with geochemical and paleobotanical models, supporting a proposal that productivity was mainly controlled by temporal atmospheric O 2 and CO 2 levels. © 2010 Elsevier B.V. All rights reserved. 1. Introduction With the exception of the Early Triassic ‘coal gap’ (Retallack et al., 1996), peat deposits and peatland ecosystems have been important components of the global carbon cycle since the Late Devonian (Greb et al., 2006; Han and Yang, 1980); during this interval peat has accumulated under a wide range of atmospheric compositions (Berner, 2006). Differences in atmospheric chemistry, in particular the concentration of O 2 and CO 2 are predicted to influence the rate at which peatland accumulates carbon and will, in turn, influence the significance of the peatland carbon reservoir in the global carbon cycle (Beerling and Woodward, 2001). As we move towards a warmer, CO 2 rich state of the Earth's climate, understanding the response of peatland to a wide range of atmospheric conditions becomes ever more important, and it is the aim of this paper to evaluate the carbon accumulation pattern and its controls in the Lopingian tropical peatland developed under markedly different atmosphere, which contained ca. 25% O 2 and 0.1% CO 2 according to recent model outputs (Berner, 2006, 2009). Although efforts have been made to understand carbon accumu- lation rates in Cenozoic lignite and coal deposits (e.g. Large, 2007; Large et al., 2003, 2004), carbon accumulation in pre-Cenozoic peatland has not been well investigated because estimates of carbon accumulation rates require a method of constraining time. In conjunction with associated uncertainties, methods like radiogenic dating may lack the precision required to constrain time in even relatively thick coal seams (Allègre, 2008); alternative methods are required. If the coal is sufficiently thick, one feasible way to tackle this problem is to identify Milankovitch cycles in geochemical or geophysical data (Schwarzacher, 1993; Weedon, 2003), and this has been applied to Cenozoic coal and lignite (Briggs et al., 2007; Large, 2007; Large et al., 2003; 2004). An additional and complementary approach to the application of orbital cycles is to use the Holocene peat record to estimate reasonable upper and lower limits of peat accumulation rate to help further define the likely range of carbon accumulation rates (Large, 2007). However, this method assumes a degree of uniformitarianism and requires understanding of carbon loss during coalification. Although these approaches have distinct drawbacks, in combination they have the potential to provide reasonable constraints that can be considered in the context of expected trends in productivity and decay. Ultimately they are one of the few, perhaps the only means to evaluate this type of information prior to the Cenozoic. Palaeogeography, Palaeoclimatology, Palaeoecology 300 (2011) 152–157 ⁎ Corresponding author. Tel./fax: + 86 10 62331248x8523. E-mail address: ShaoL@cumtb.edu.cn (L. Shao). 0031-0182/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.palaeo.2010.12.019 Contents lists available at ScienceDirect Palaeogeography, Palaeoclimatology, Palaeoecology journal homepage: www.elsevier.com/locate/palaeo