Robson, B. E., Collinson, M. E., Riegel, W., Wilde, V., Scott, A. C., & Pancost, R. D. (2015). Early Paleogene wildfires in peat-forming environments at Schöningen, Germany. Palaeogeography, Palaeoclimatology, Palaeoecology, 437, 53-62. https://doi.org/10.1016/j.palaeo.2015.07.016 Publisher's PDF, also known as Version of record License (if available): CC BY Link to published version (if available): 10.1016/j.palaeo.2015.07.016 Link to publication record in Explore Bristol Research PDF-document This is the final published version of the article (version of record). It first appeared online via Elsevier at http://www.sciencedirect.com/science/article/pii/S0031018215003764. Please refer to any applicable terms of use of the publisher. University of Bristol - Explore Bristol Research General rights This document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/red/research-policy/pure/user-guides/ebr-terms/ Palaeogeography, Palaeoclimatology, Palaeoecology 437 (2015) 53–62 Contents lists available at ScienceDirect Palaeogeography, Palaeoclimatology, Palaeoecology journal homepage: www.elsevier.com/locate/palaeo Early Paleogene wildfires in peat-forming environments at Schöningen, Germany Brittany E. Robson a,⁎, Margaret E. Collinson a, Walter Riegel b,VolkerWildec, Andrew C. Scott a, Richard D. Pancost d a Department of Earth Sciences, Royal Holloway University of London, Egham, Surrey, TW20 0EX, UK b Geowissenschaftliches Zentrum Göttingen, Geobiologie, Goldschmidtstrasse 3, D-37077, Göttingen, Germany c Sektion Palaeobotanik, Senckenberg Forschungsinstitut und Naturmuseum, Senckenberganlage 25, 60325 Frankfurt am Main, Germany d The Cabot Institute and the Organic Geochemistry Unit, School of Chemistry, University of Bristol, Cantocks Close, Bristol, BS8 1TS, UK article info abstract Article history: Wildfire activity in early Paleogene greenhouse conditions can be used as an analogue to gauge the effect of fu- Received 31 March 2015 ture warming trends on wildfire in the current climate system. Inertinite (fossil charcoal in coal) from 11 autoch- Received in revised form 7 July 2015 thonous early Paleogene lignite seams from the Schöningen mine (Germany) was quantified using macerations, Accepted 10 July 2015 in situ pillars and industry standard crushed samples. A new three transect method was developed to quantify in Available online 19 July 2015 situ charcoal. The combination of in situ pillars and crushed samples accounts for temporal and spatial variation in charcoal through a stratigraphically oriented pillar, whilst maintaining comparability with industry standards Keywords: fi Inertinite and previous work. Charcoal occurs as a range of randomly distributed particle sizes, indicating that res were Charcoal burning locally in the Schöningen peat-forming environment and in the surrounding areas, but according to pet- Coal rological data, not in an episodic or periodic pattern. Although charcoal abundance is low (relative to previous Lignite high fire worlds such as the Cretaceous), three quantitative and semi-quantitative methods show increased wild- Eocene fire activity (relative to the modern world) in the warmest parts of the early Paleogene. As atmospheric oxygen EECO levels stabilised to modern values and precipitation and humidity became the main control on wildfire, increased rainfall followed by drier intervals would have created an environment rich in dry fuel in which wildfires could easily propagate if humidity was low enough. In the later part of the Early Eocene (Ypresian) charcoal abundance fell to levels similar to those found in modern peats. This indicates that the transition to the modern low fire world occurred within the Early Eocene, earlier than previous records suggest. © 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). 1. Introduction warm climates (e.g. the Early Eocene Climatic Optimum, EECO) are not direct analogues for future warming trends in the current climate Wildfire has always been an important part of the natural environ- system because they occur during a time when global temperatures ment (Bowman et al., 2009; Pausas and Keeley, 2009; Scott et al., were significantly warmer than now. However, improved temporal res- 2014), but the role of wildfire in the early Paleogene ecosystems is not olution of early Paleogene wildfire activity can lead to better under- yet fully understood (Scott, 2000; Belcher et al., 2013). One of the key standing of the modern fire world and contribute to better predictions sources of evidence for ancient wildfires is the presence of charcoal of wildfire activity in future warm climates. (Potonié, 1929; Harris, 1958; Komarek, 1972; Scott, 1989, 2000, 2010; Charcoal can accumulate in any depositional environment, but peat Glasspool and Scott, 2013; Scott et al., 2014), an inert substance with a deposits are particularly valuable archives of past wildfire activity. Peat high potential for survival in the fossil record (Scott, 1989, 2010; is an accumulation of partially decayed plant material which, after Figueiral, 1999). A 400 million year record of charcoal in coals peatification and burial diagenesis, may transform to lignite. Lignite is (Glasspool and Scott, 2010; also replotted by Bond, 2015)showeda less altered than more mature, higher rank, coals, preserving a record transition in the Cenozoic from moderate (17% in the Paleocene) to of the peat-forming environment and vegetation (Teichmüller, 1989; low (3.5% in the Middle to Late Eocene) charcoal percentages. However, Scott, 1991a,b; Wüst et al., 2001; Moore and Shearer, 2003)sometimes that study was limited by the use of 10 million year bins. Paleogene to the molecular level (Pancost et al., 2007; Fabbri et al., 2009). Charcoal in the peat-forming environment is likely to be preserved closer to its point of formation than in other settings, as it is not subjected to vari- ⁎ Corresponding author at. Earth Sciences, Queens Building, Royal Holloway University fl of London, Egham Hill, Surrey, TW20 0EX, UK. ables of uvial transport including differential saturation (Vaughan E-mail address: [email protected] (B.E. Robson). and Nichols, 1995; Nichols et al., 2000), concentration, floatation, size http://dx.doi.org/10.1016/j.palaeo.2015.07.016 0031-0182/© 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). 54 B.E. Robson et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 437 (2015) 53–62 Fig. 1. (A) Central European palaeofacies map showing the location of the Schöningen mine (white S in black circle), modern coastlines and Germany (see inset); modified from Riegel et al. (2015, Fig 1). (B) An overview of the Schöningen mine (Google Earth, accessed September 2013) with approximate collecting areas marked in the north and south. sorting and fragmentation (Nichols, 1999; Scott et al., 2000). Moreover, underlying interbeds, indicating autochthonous peat accumulation peat-forming environments require hydrological stability (Holden, (supplementary material herein; Riegel et al., 2012). Between each 2005), which mitigates the impact of different climate regimes when seam is an interbed composed of clastic sediments, these sediments comparing records of wildfire (Glasspool and Scott, 2010). Therefore, are crucial indicators of the depositional environment (Riegel et al., the charcoal record in lignites offers the best option for comparison of 2012). Characteristic features include bimodal cross bedding, coarsen- the wildfire record between past time intervals. ing and fining upward sequences, Ophiomorpha burrows and infilled Riegel et al. (2012) have undertaken a long term stratigraphic, sedi- burrows in tops of seams. Taken together these indicate a nearshore mentological and palaeoenvironmental study of the Schöningen mine coastal setting subjected to tidal influence, changes in energy regime (Fig. 1), the sole north German locality where early Paleogene lignites and episodic submergence or emergence (Riegel et al., 2012). Interbed can be studied in succession. Their field surveys document charcoal in 5 (above seam 4) also contains rooted seagrasses, which clearly indicate multiple seams in different quantities. The current work uses three marine influence (supplementary material herein; Riegel et al., 2012). methods to quantify charcoal in the Schöningen sequence of early Paleo- Thick, flat lying root branches immediately underlying seam 6 were gene peat-forming environments, enabling high resolution reconstruc- interpreted by Riegel et al. (2012) as indication of a tall mire forest tion of long term changes in early Paleogene wildfire and interpretation growing on a marine substrate. Interbed 9 (above seam 8) shows the of the timing of the transition to modern levels of fire activity. least marine influence at Schöningen as indicated by in situ palm stumps (supplementary Fig. 2.10.3; Riegel et al., 2012). 2. The Schöningen mine Combined evidence from lignite seams and interbeds at Schöningen reveals three main facies. Terrestrial peat-formation is obvious from the 2.1. Regional geology and palaeoenvironments many lignite seams, shore-line deposition is indicated by palm stumps and evidence of intertidal sedimentation is visible in most interbeds. It The Schöningen Südfeld open cast mine in Lower