Palaeogeography, Palaeoclimatology, Palaeoecology 438 (2015) 245–255
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Palaeogeography, Palaeoclimatology, Palaeoecology
j ourna l homepage: www.e lsev ie r .com/ locate /pa laeoEcological and biogeochemical change in an early Paleogene
peat-forming environment: Linking biomarkers and palynologyGordon N. Inglis a,b,⁎, Margaret E. Collinson c, Walter Riegel d,e, Volker Wilde e, Brittany E. Robson c,
Olaf K. Lenz f, Richard D. Pancost a,b
a Organic Geochemistry Unit, School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK
b Cabot Institute, University of Bristol, Bristol BS8 1UJ, UK
c Department of Earth Sciences, Royal Holloway University of London, Egham, Surrey TW20 0EX, UK
d Geowissenschaftliches Zentrum Göttingen, Geobiologie, Goldschmidtstrasse 3, D-37077 Göttingen, Germany
e Senckenberg Forschungsinstitut und Naturmuseum, Senckenberganlage 25, D-60325 Frankfurt am Main, Germany
f TU Darmstadt, Institut für Angewandte Geowissenschaften, Angewandte Sedimentgeologie, Schnittspahnstrasse 9, Germany⁎ Corresponding author at: Organic Geochemistry Unit,
of Bristol, Cantock's Close, Bristol BS8 1TS, UK. Tel.: +44 1
E-mail address: gordon.inglis@bristol.ac.uk (G.N. Ingli
http://dx.doi.org/10.1016/j.palaeo.2015.08.001
0031-0182/© 2015 The Authors. Published by Elsevier B.Va b s t r a c ta r t i c l e i n f oArticle history:
Received 28 January 2015
Received in revised form 27 July 2015
Accepted 1 August 2015
Available online 8 August 2015
Editor: T. Correge
Keywords:
Paleocene
Eocene
bryophyte
Sphagnum bogSphagnummoss is the dominant plant type inmodern boreal and (sub)arctic ombrotrophic bogs and is of particular
interest due to its sensitivity to climate and its important role in wetland biogeochemistry. Here we reconstruct the
occurrence of Sphagnum moss – and associated biogeochemical change – within a thermally immature,
early Paleogene (~55 Ma) lignite from Schöningen, NW Germany using a high-resolution, multi-proxy
approach. Changes in the abundance of Sphagnum-type spores and the C23/C31 n-alkane ratio indicate the
expansion of Sphagnum moss within the top of the lignite seam. This Sphagnum moss expansion is associated
with the development of waterlogged conditions, analogous to what has been observed within modern
ombrotrophic bogs. The similarity between biomarkers and palynology also indicates that the C23/C31 n-alkane
ratio may be a reliable chemotaxonomic indicator for Sphagnum during the early Paleogene. The δ13C value of
bacterial hopanes and mid-chain n-alkanes indicates that a rise in water table is not associated with a substantial
increase in aerobic methanotrophy. The absence of very low δ13C values within the top of the seam could reflect
either less methanogenesis or less efficient methane oxidation under waterlogged sulphate-rich conditions.
© 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
The early Paleogene (66–34 Ma) is characterised by high atmo-
spheric carbon dioxide (pCO2) concentrations (Pearson and Palmer,
2000; Pagani et al., 2005; Lowenstein and Demicco, 2006; Pearson
et al., 2009), high sea surface temperatures (SST) (Pearson et al.,
2007; Bijl et al., 2009; Hollis et al., 2012), high land temperatures
(Huber and Caballero, 2011; Pancost et al., 2013) and intensification
of the hydrological cycle (Pierrehumbert, 2002; Pagani et al., 2006;
Krishnan et al., 2014). As a result, early Paleogene wetland environments
may have been up to ~3 times more abundant than today (Sloan et al.,
1992; DeConto et al., 2012).
Modernwetlands are the largest natural source of atmospheric meth-
ane (CH4) with estimates ranging between 80 and 280 Tg CH4 yr−1
(Bridgham et al., 2013). As a result, the ecology and biogeochemistry of
wetlands are increasingly recognised as central to understanding Paleo-
gene biogeochemical feedbacks. Although there are no proxy methodsSchool of Chemistry, University
17 9546395.
s).
. This is an open access article underfor reconstructing ancient CH4 emissions, the carbon isotope value of
bacterial hopanes has been used to infer relative changes in terrestri-
al methane cycling (e.g., Pancost et al., 2007). For example, a de-
crease in the carbon isotope value of bacterial hopanes during the
onset of the Paleocene-Eocene Thermal Maximum (PETM; ~56 Ma)
indicates enhanced CH4 production within an ancient peat-forming
environment (Pancost et al., 2007). Over longer timescales, modelling
studies suggest a ~6- to 7-fold increase inwetland CH4 emissions during
the early Paleogene (Beerling et al., 2011). Enhanced CH4 emissions and
changes in other biogenic trace gases (i.e., N2O and O3) may have acted
to increase global temperature by 2.7 °C during the early Paleogene
(Beerling et al., 2011) and could have been an important mechanism
for maintaining high-latitude warmth (Sloan et al., 1992).
A particularly important topic of interest in palaeoclimate investiga-
tions has been tracing the occurrence and distribution of Sphagnum
moss in wetland environments. Sphagnummoss is the dominant plant
type inmodern ombrotrophic bogs (Clymo, 1984) andplays an important
role in terrestrial methane cycling (Raghoebarsing et al., 2005; Kip et al.,
2010). Under anoxic, waterlogged conditions, anaerobic degradation of
Sphagnum produces significant quantities of CH4 that contribute to the
total atmospheric CH4 flux (Clymo, 1984). However, Sphagnum can alsothe CC BY license (http://creativecommons.org/licenses/by/4.0/).
246 G.N. Inglis et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 438 (2015) 245–255limit CH4 emissions by consuming CH4 symbiotically with aerobic
methane-oxidising bacteria (Raghoebarsing et al., 2005; Kip et al., 2010).
A variety of organic geochemical proxies can be used to track changes
in peat-forming vegetation, specifically the input of Sphagnum moss
(Nott et al., 2000; Pancost et al., 2002; Xie et al., 2004; Bingham et al.,
2010). Sphagnum species are typically dominated by mid-chain C23 and
C25 n-alkanes (Baas et al., 2000; Nott et al., 2000), whereas terrestrial,
peat-forming higher-plants, such as Ericaceae or Carex, are dominated
by long-chain C29 and C31 n-alkanes (Eglinton and Hamilton, 1967).
As such, the C23/C31 n-alkane ratio has been proposed as a tracer for
Sphagnum input into ancient peat deposits (Nott et al., 2000; Bingham
et al., 2010). A number of studies have shown the close correspondence
between the C23/C31 n-alkane ratio and the relative abundance of
Sphagnum leaves in a variety of modern ombrotrophic bogs (Nott
et al., 2000; Pancost et al., 2002, 2003; Xie et al., 2004). While this has
been used to reconstruct vegetation and hydrological change during
the Holocene (e.g., Nott et al., 2000), it has not been applied to older
peat-forming environments.
In order to investigate ecological, hydrological and biogeochemical
change within an early Paleogene peat-forming setting, we reconstruct
downcore variations in Sphagnum moss within a lignite seam using a
high-resolution, multi-proxy approach. Samples are derived from
Seam 1, a thermally immature lignite from the Schöningen Südfeld
mine, northern Germany (~41 °N palaeolatitude). We use the C23/C31 n-
alkane ratio and the abundance of Sphagnum-type spores to reconstruct
the occurrence of Sphagnum moss. Using this, and other palynological
and petrological indicators, we elucidate hydrological change within an
early Paleogene peat-forming environment. We then use bacterially-
derived hopane distributions and compound-specific carbon isotopes to
characterise the biogeochemical response associated with these hydro-
logical changes in a warmer climate.
2. Methods
2.1. Site description
Samples were collected from the Schöningen Südfeld mine in north-
ern Germany, NW Europe (Fig. 1) where the sediments were deposited
in a low lying coastal setting (Riegel et al., 2012). Samples are derived
from a ~2.7 m thick lignite seam (Seam 1) overlain and underlain by
brackish to shallow marine, clastic sedimentary deposits (Riegel et al.,
2012). Given the thickness of the seam, we focussed our high-resolutionNORTH SEA BASIN
ARMORICAN
     MASSIF
H
km
S
RHENISH MASSIF 
BOHEM
IAN MA
SSIF
POLISH ANTICLINORIU
FENNO-SCANDIAN HIGH
RH
IN
E 
GR
AB
EN
BRISTOL
Fig. 1. Palaeogeography of NW Europe during the earl
Modified from Riegel et al., 2012.study on the lower and upper part of Seam 1. Samples were collected
(c. every 5 cm) from the lower (267 to 200 cm) and upper part of Seam
1 (57 to 0 cm) as well as the overlying brackish to shallow marine inter-
beds (0 to 36 cm above the seam top). Peat accumulation rates in tropical
and subtropical climates are 2 mm/year and 0.8 mm/year, respectively
(Collinson et al., 2009 and references therein). Assuming a median peat-
to-lignite compaction ratio (7:1) (Ryer and Langer, 1980), Seam 1 spans
between 9.5 and 23.6 kyr. The full range, taking thematerial into account
(i.e., woody dominated material vs parenchymatous tissues; Collinson
et al., 2009) is 2.7 to 101.2 kyr.
The dinocyst zone D 5nb was recognised above Main Seam in the
nearby Emmerstedt area by Ahrendt et al. (1995). If the Main seam is
coeval at both sites this would indicate that Seam 1 at Schöningen is
earliest Eocene.Within Interbed 2, above Seam 1, there is an abundance
of the dinocyst Apectodinium (Riegel et al., 2012) which may represent
the Paleocene-Eocene Thermal Maximum (PETM) as it does at other
sites (Crouch et al., 2003; Sluijs et al., 2007; Sluijs and Brinkhuis, 2009).
If so then Seam 1 could be latest Paleocene. However, it should
be noted that there are other Apectodinium acmes in northern mid-
latitude settings during the early Paleogene (see discussion in Collinson
et al., 2009, p. 45–51). In summary, we conclude that Seam 1 is of latest
Paleocene or earliest Eocene age. Palaeogeographically, Schöningen
was located between the Harz Mountains and the Flechtingen Rise at
the southern shore of the North Sea during this time interval (Riegel
et al., 2012; Fig. 1) at a palaeolatitute of ~41 °N (van Hinsbergen et al.,
2015).
2.2. Elemental and bulk δ13C analyses
Total carbon (TC), total nitrogen (TN) and total hydrogen (TH)
analyses were performed using a Carlo Erba EA1108 Elemental
Analyser. Total sulphur (TS) analysis was performed in a similar
method using a Eurovector EA3000 Analyser. Inorganic carbon (IC)
analysis was performed using a Modified Coulomat 702 Analyser with
a coulometric cell. Total organic carbon (TOC) content was determined
by subtracting IC from TC. Bulk δ13C analysis was undertaken at Royal
Holloway following the methods used by Pancost et al. (2007).
2.3. Organic geochemistry
Approximately 1–10 g of sediment was extracted via Soxhlet
apparatus for 24 h using dichloromethane (DCM):methanol (MeOH)0 100 200 300
Land surface
Terrestrial facies
Marine facies with
shallow water carbonates
Marine facies with clays
and sands
direction of
sediment input
Tethyan  current 
Boreal current
Study site: Schöningen
Marine-terrestrial facies 
with clays 
Marine-terrestrial facies 
with shallow water carbonates
M
HS
Marine facies with clay
y Paleogene showing the location of Schöningen.
 240
260
280
220
200
40
20
0
-20
Silt
Clay 
Lignite
Silt lenses
D
ep
th
 b
el
ow
 o
ve
rly
in
g 
m
ar
in
e 
in
te
rb
ed
s 
(cm
) 
0 40 80 120
0 20 40 60 0 2 4 6 8
TOC (%) Sulphur (%)
C:N ratio
a) b) c)
Fig. 2. a) Total organic carbon (%), b) carbon-to-nitrogen (C:N) ratio and c) total sulphur (%)
within Seam1, Schöningen. Zero depthmarks the top of Seam1 and thebase of the overlying
interbed 2.
247G.N. Inglis et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 438 (2015) 245–255(2:1 vol/vol) as the organic solvent. The total lipid extract (TLE) was
initially separated over silica into neutral and fatty acid fractions
using chloroform-saturated ammonia and chloroform:acetic acid
(100:1 vol/vol), respectively (Dickson et al., 2009). The neutral fraction
was subsequently fractionated over alumina into apolar and polar
fractions using hexane:DCM (9:1 vol/vol) and DCM:MeOH (1:2 vol/vol),
respectively. All fractions were analysed via gas chromatography–mass
spectrometry (GC–MS) using a Thermoquest Finnigan Trace GC
interfaced with a Thermoquest Finnigan Trace MS. The electron
ionisation source was set at 70 eV. Scanning occurred between m/z
ranges of 50 to 650 Da. The GC was fitted with a fused silica capillary
column (50 m × 0.32 mm i.d.) coated with a ZB1 stationary phase
(dimethylpolysiloxane equivalent, 0.12 μm film thickness). Compound
specific carbon isotope analysis was performed on selected apolar frac-
tions using a Trace GC Ultra gas chromatograph coupled to a Finnigan
MAT DeltaplusVmass spectrometer via a FinniganMAT Conflo IV inter-
face. GC Conditions were as for GC–MS. Each value was measured in
duplicate and is reported in standard per mil notation (‰) relative to
Vienna PeeDee Belemnite (VPDB).
The average chain length (ACL) is defined for n-alkanes using the
following equation (Eglinton and Hamilton, 1967);
ACL ¼ ð25 nC25ð Þ þ 27 nC27ð Þ þ 29 nC29ð Þ þ 31 nC31ð Þ þ 33 nC33ð Þ
nC25 þ nC27 þ nC29 þ nC31 þ nC33ð Þ
while the carbon preference index (CPI) is defined using the following
equation (Bray and Evans, 1961);
CPI ¼ 0:5  nC25 þ nC27 þ nC29 þ nC31
nC26 þ nC28 þ nC30 þ nC32 þ
nC27 þ nC29 þ nC31 þ nC33
nC26 þ nC28 þ nC30 þ nC32

 
:
The pAq ratio is defined for n-alkanes using the following equation
(Ficken et al., 2000);
pAq ¼ nC23 þ nC25
nC23 þ nC25 þ nC29 þ nC31 :
2.4. Palynology
Approximately 1–2 g of lignite was boiled with 15% hydrogen
peroxide (H2O2) followed by treatment with 2% potassium hydroxide
(KOH). Samples fromunconsolidated clastic interbedswere briefly boiled
with 15% H2O2 and ultrasonicated to separate the organic and mineral
matter. In some instances, 2% KOH was added to organic-matter rich
clastic samples. Cold hydrofluoric acid was applied for several days in
order to remove silica and silicate material from each sample. Samples
were then sieved through a 10 μm mesh screen, retaining the coarser
fraction. A sub-sample was mounted in glycerine jelly to produce slides
subsequently studied by light microscopy. The identification of pollen
and spore taxa is based upon previous work (Hammer-Schiemann,
1998). Slides and residues will finally be stored in the palaeobotanical
collections of the Senckenberg Forschungsinstitut und Naturmuseum,
Frankfurt am Main, Germany.
2.5. Petrology
Petrological study was undertaken only on the lignites of Seam 1 (not
on the overlying or underlying siliclastic interbeds). Polished blocks of
crushed lignite were prepared to industry standard by Jim Hower and
colleagues at the Centre for Applied Energy Research, University of
Kentucky using approximately 1–5 g of lignite. Where possible samples
were crushed to the standard 20 mesh size, ≤840 μm, using a grinder.
Soft samples were crushed manually to a top particle size of c. 1000 μm.A subsample was embedded in epoxy resin. Once dry, the block was
polished using 60-, 240-, 400-, and 600-grit SiC papers followed by
0.3-micron alumina on Buehler Texmet paper and 0.05-micron alumina
on silk. The finished polished blocks were viewed in reflected light
under immersion oil (Cargille type A, density 0.923 g/cc at 23 °C, RI of
1.514) using a Leica reflected light microscope and a ×20 oil immersion
objective. Lignite components (maceral groups), huminite, liptinite and
inertinite, were classified according to the International Committee for
Coal and Organic Petrology (ICCP) standard. Inertinite, recognised by
its high reflectance and cellular preservation (ICCP, 2001), is a product
of wildfire (Scott, 2002). Huminite, characterised by low reflectance
and varied cellular preservation (Sýkorová et al., 2005) indicates how
wet or dry the conditions of peat formationwere. The huminitemaceral
ulminite is defined by highly gelified plant material (with homogenous
plant cell walls, no visible internal structures and obscured cell lumina)
that indicates formation under wet conditions (Sýkorová et al., 2005).
Non-gelified huminite macerals attrinite (cemented detrital material)
and textinite (cell walls not gelified, open or open but infilled cell lumina)
indicate drier conditions during peat formation (Sýkorová et al., 2005).
Macerals were quantified following the method outlined in Robson
et al. (2015).
3. Results
3.1. Elemental analysis
Total organic carbon (TOC) content within Seam 1 is generally high
(N50–60wt.%; Fig. 2a)with a gradual decrease in the bioturbated upper
~15 cm (15–40 wt.%). TOC values in the overlying marine interbeds
are relatively low (3–9 wt.%). C/N ratios are high throughout Seam
1 (50–95; Fig. 2b) with lower values in the overlying marine inter-
beds (21–37). This is consistent with a terrestrial organic matter
source throughout (Boutton, 1991). Total sulphur (TS) content is
high throughout Seam 1 (3.9–7.6 wt.%) with lowest values in the
overlyingmarine interbeds (2.1–4.1 wt.%; Fig. 2c). High sulphur con-
tents (e.g., N3 wt.% S) in peat horizons are generally attributed to the
incorporation of seawater sulphate into the peat-forming environment
(Chou, 2012).
248 G.N. Inglis et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 438 (2015) 245–2553.2. Bulk δ13Corg
Bulk δ13Corg values (Fig. 9a, diamonds) were determined for the top
of Seam 1 (57–0 cm) and the overlying marine interbeds (0–36 cm).
Within the lignite, values range from−25.9‰ to−27.9‰. Within the
marine interbeds, values range from−26.5‰ to−27.0‰. Between 57
and 0 cm in Seam 1, bulk δ13Corg values exhibit a gradual upwards
decrease in δ13C by ~1‰.3.3. Plant-derived biomarkers
Plant biomarkers, including a range of n-alkyl and terpenoid
components, dominate all of the lipid fractions analysed. The apolar
fraction is characterised by a homologous series of n-alkanes with a
strong odd-over-even predominance (Figs. 3, 4a). Long-chain (C27–C31)
homologues, typically derived from the epicuticular wax of higher
plants, are the most abundant (2 to 65 μg/g dry sediment). A terrestrial
plant origin is confirmed by the n-alkane carbon preference index
(CPI), which on average is 5.9 (Bray and Evans, 1961; Eglinton and
Hamilton, 1967). The average n-alkane chain length (ACL) ranges from
26.8 to 29.8 within Seam 1 and is typical for modern tree species
(Diefendorf et al., 2011). Mid-chain homologues (C23–C25), derived
from submerged and floating macrophytes (Ficken et al., 2000) and/or
Sphagnummoss (Baas et al., 2000; Nott et al., 2000), are also relatively
abundant (1 to 32 μg/g dry sediment; Figs. 3–4). The C23/C31 n-alkane
ratio (Fig. 7a), which is commonly used to trace the input of Sphagnum
moss to Holocene peat (e.g., Nott et al., 2000), ranges from 0.1 to 6.6
within Seam 1. Short-chain (C17–C21) homologues, typically derived17 18
19
20 21 22
23
24
25
I.S
I  
n-alkanes
Isoprenoids
Hopanes
Retention tim
R
el
at
ive
 in
te
ns
ity
a) TIC
b) m/z 57
n-alkanes
Isoprenoids
PMI
Fig. 3. Partial gas chromatogramof a typical, lignite-derived apolar fraction. a) TIC. Roman numera
and III: Unknown Ring-A monoaromatic triterpenoid, IV: Dinor-oleana(ursa)-1,3,5(10
Dinor-oleana(ursa)-1,3,5(10),12-tetraene, IX: Lanosta(eupha)pentaene, X: Dinor-olea
Tetranor-oleana(ursa)-1,3,5(10),6,8,11,13-heptaene, XIII: Tetranor-oleana(ursa)-1,3,5(
accompaniedwithGreek letters signify the carbonnumber and theC-17 andC-21 stereochemistry
circles).from marine algae, are of low abundance throughout (b1 to 14 μg/g
dry sediment; Figs. 3–4).
The apolar fraction also contains a variety of di- and triterpenoids.
Diterpanes of the abietane and pimarane class are abundant within
Seam 1 between 57 and 43 cm, especially fichtelite, norisopimarane
and retene. These compounds are non-specific conifer biomarkers
(Otto and Simoneit, 2001). Tetracyclic triterpanes, which are derived
from angiosperms and/or gymnosperms (Diefendorf et al., 2014), were
identified but are in low abundance. Pentacyclic triterpenoids derived
from angiosperms (Simoneit et al., 1986; Otto et al., 2005) are abundant
throughout, especially ring-A monoaromatic triterpenoids (Jacob et al.,
2007; Fig. 3).
The polar fraction contains mid- and long-chain n-alkanols (C20–C32)
with a strong even-over-odd predominance (Fig. 4b). The average chain
length ranges from 24.7 to 27.1 and the dominant n-alkanol is C26 or
C28. This is consistent with a mixed contribution from Sphagnummoss
and peat-forming plants such as Ericaceae (Ficken et al., 2000; Pancost
et al., 2002). This presence of peat-forming plants other than Sphagnum
is consistent with the identification of amyrenone, a triterpenoid ketone
frequently found in angiosperms. An unknown compound with
M+ 438 and m/z 203 was identified and is also likely derived from
angiosperms (Stefanova et al., 2008). The fatty acid fraction contains
mid- and long-chain n-alkanoic acids (C24–C32) with a strong even-
over-odd predominance (Fig. 4c). The average chain length ranges
from 25.6 to 28.0 and the dominant n-alkanoic acid is C28. This is
consistent with terrestrial plant source (Eglinton and Hamilton, 1967).
The fatty acid fraction contains trace quantities of short-chain n-alkanoic
acids (C16–C18) which can have a bacterial or plant-derived source (Baas
et al., 2000).*
26
27 
28 29
X
IX
VIII
VII
IV XI
XII
XIII
XIV
II
III
VI
V
C32
ββ
C31
ββ
C30
ββ
C31
αβ
e
Sq.
ls denote plant-derived diterpenane and triterpene derivatives (Jacob et al., 2007). I: Retene, II
),13(18)-tetraene, V, VI and VII: Unknown Ring-A monoaromatic triterpenoid, VIII
na(ursa)-1,3,5(10)-triene, XI: Dinor-oleana(ursa)-1,3,5(10),13(18)-tetraene, XII:
10),6,8,11,13-heptaene, XIV: Tetranor-lupa-1,3,5(10),6,8,11,13-heptaene. Numbers
of bacterial hopanes. b)m/z57 trace showing isoprenoids (open circles) andn-alkanes (closed
0.0
0.1
0.2
0.3
0.4
0.0
0.1
0.2
0.3
0.4
0.5
0.0
0.1
0.2
0.3
C21 C23 C25 C27 C29 C31 C33 C20 C22 C24 C26 C28 C30 C32 C20 C22 C24 C26 C28 C30 C32 C34
% %%
n =30 n =30n =30
n-alkanes n-alkanols n-alkanoic acids
a) c)b)
Fig. 4. The average fractional abundance of a) n-alkanes, b) n-alkanols and c) n-alkanoic acids within Seam 1 (n = 30). Error bars reflect one standard deviation.
249G.N. Inglis et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 438 (2015) 245–255Compound specific carbon isotope (δ13C) analysis was performed
upon a selection of apolar, plant-derived biomarkers from the top of
Seam 1 and the overlying marine interbeds (n= 18). In some samples,
co-elution of other compounds prevents the determination of δ13C
values. The δ13C value of long-chain (C27–C29) n-alkanes within Seam
1 (Figs. 5 and 9a) ranges from−29.4 to−32.5‰, consistent with a C3
higher-plant origin (Collister et al., 1994) and values typically observed
in ombrotrophic bogs (Pancost et al., 2000). The δ13C value ofmid-chain
(C23–C25) n-alkanes (Figs. 5 and 9a) is slightly heavier, ranging from
−27.9 to−30.5‰ and is consistent with a contribution from a partially
submerged source (Ficken et al., 2000). The δ13C values are summarised
in Fig. 5.3.4. Bacterial-derived biomarkers
The apolar fraction contains abundant C27–C32 hopanes (Fig. 3).
C33–C35 hopanes were also identified but were a relatively minor
constituent. Both are derived from the cell membrane of prokaryotes
(Ourisson and Albrecht, 1992; Sinninghe Damsté et al., 1995). Total
hopane ββ/(ββ+ αβ+ βα) ratios are relatively high (0.46–0.81), indi-
cating that the samples are relatively immature. C31 homohopane
ββ/(ββ+ αβ+ βα) ratios exhibit the same temporal trends as the
total hopanes but are significantly lower (0.15–0.53). This does not
reflect thermal maturity but rather the production of high amounts
of C31 αβ homohopane, the dominant hopane in recent (b10 ka),
thermally immature, ombrotrophic peat bogs (Quirk et al., 1984;
Dehmer, 1993, 1995; Pancost and Sinninghe Damsté, 2003).-24
-26
-28
-30
-32
-34
δ1
3 C
 (‰
)
Diterpenoids Mid-chain
n-alkanes
Long-
chain
n-alkanes
C31 αβ
homo-
hopane
C31 ββ
homo-
hopane
C31 ββ
hopane
Key: Maximum
Upper quartile
Median
Lower quartile
Minimum
Fig. 5. δ13C value of plant-derived (dark grey) andmicrobial-derived (light grey) biomarkers
within the top of Seam 1 (0–54 cm) and the overlying marine interbeds (0–36 cm).Compound specific carbon isotope (δ13C) analysis was performed on
a selection of apolar, bacterial-derived biomarkers from the top of Seam
1 (n=18). In some samples, co-elution of other compounds prevents the
determination of δ13C values. The δ13C values of the C31 ββ homohopane
range from−29.1 to−33.1‰. Values of the C30 ββ hopane are similar,
ranging from −29.1 to −31.2‰. The C31 αβ homohopane is
13C-enriched relative to both the C31 ββ homohopane and the C30 ββ
hopane and ranges from −24.9 to −30.4‰. The δ13C values are
summarised in Fig. 5.
3.5. Palynology
Within Seam 1, the dominant plant types represented by
palynomorphs are Sphagnum moss as indicated by the abundance
of Sphagnum-type spores (Fig. 6) (especially Tripunctisporis, originally
used as a subgenus of the widely used but invalid genus Stereisporites),
ferns (e.g., Laevigatosporites — Fig. 7b), swamp-dwelling conifers (e.g.,
Inaperturopollenites — Fig. 7a) and mixed mesopytic forest vegetation
(e.g., Tricolporopollenites cingulum). Seam 1 is traceable over a few
kilometres and the relative abundance of Sphagnum-type spores
exhibits a similar change in relative abundance through the seam in
all three sections studied (Hammer-Schiemann, 1998). In this section,
consistently low values occur in the lower part of the seam between
200 and 267 cm (0–10%) with a large increase in abundance in the
upper part between 0 and 57 cm (7–48%) (Fig. 7b). During the latter
interval, Sphagnum-type spores comprise, on average, ~21% of the
entire palynological assemblage. Sphagnum-type spores are absent or
in very low abundance within the overlying marine interbeds (b0.3%).
Ferns, specifically Laevigatosporites (Fig. 8b) are abundant between 57
and 43 cm (~10.6%) while Inaperturopollenites (Fig. 8a) proliferates
within the overlying interbeds (~32%).
The dinoflagellate cyst Apectodinium (Fig. 8f) tentatively identi-
fied as A. homomorphum (Riegel et al., 2012), is abundant just
above the base of marine interbed 2 where it comprises 13–45% of
the entire palynomorph assemblage. Within Seam 1, small quantities of
Apectodinium occur between 12 and 2 cm (b2%), likely as a result of bio-
turbation penetrating down into the seam from the overlying interbed.
Resting cysts of the freshwater green-algal family Zygnemataceae
(Fig. 8f) are present between 21 and 2 cm (b2%), but absent within the
overlying marine interbeds and the rest of Seam 1.
3.6. Petrology
Lignite is composed of macerals that are microscopically recognisable
fragments of organic matter. Of the three mainmaceral groups, huminite
was themost abundant groupwithin Seam 1 (69.3%), ranging from 53 to
87%. Liptinite was the secondmost abundant (20.9%), ranging from 9.9 to
30.8% while inertinite (Fig. 8d) was the least abundant (9.8%), ranging
from 0.8 to 23.8%. Within the huminite maceral group, three macerals
were quantified; attrinite, textinite and ulminite. Attrinite was the most
abundant (33.7%), ranging from 15.4 to 48.8%. Textinite was the second
most abundant (27.1%), ranging from 12.5 to 60.7% while ulminite
Fig. 6. Sphagnum-type spores from Seam 1. 1) Tripunctisporis sp. (a—proximal, b—distal), 2) Distancoraesporis sp. (a—proximal, b—distal), 3) Transitional form between Tripunctisporis and
Distancoraesporis (a—proximal, b—distal), 4) Sphagnumsporites sp. (a—proximal, b—distal).
250 G.N. Inglis et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 438 (2015) 245–255(Fig. 7c) was the least abundant (8.3%), ranging from 0.8 to 21.4%. On a
macroscopic scale, lignites in both the upper and lower parts of Seam 1
are composed of a mix of matrix and tissue lithotypes, but recognisable
plant tissue (uncharred) is more common in the lower part of the
sequence and charcoal is more common in the upper part. Lithotypes in
which charcoal was visible in the field contain higher inertinite
percentages in the related polished block containing a crushed sample,
in comparison to samples in which no field charcoal was visible.0 20
240
260
280
220
200
40
20
0
-20
Silt
Clay 
Lignite
Silt lenses
D
ep
th
 b
el
ow
 o
ve
rly
in
g 
m
ar
in
e 
in
te
rb
ed
s 
(cm
) 
0 2 4 6 8
Sphagnum-ty
a) b)
C23/C31 n-alkane
Fig. 7. Sphagnummoss occurrence andhydrological changewithin Seam1, Schöningen. a) C23/C
c) the relative abundance of ulminite and d) the pAq ratio (the relative abundance of mid-chain
Petrology data (ulminite) has only been obtained for lignite.4. Discussion
4.1. Evidence for the occurrence of Sphagnum in Seam 1, Schöningen
The C23/C31 n-alkane ratio is used as a chemotaxonomic proxy for
Sphagnum input in modern peat-forming environments (Baas et al.,
2000; Nott et al., 2000; Pancost et al., 2002; Bingham et al., 2010) and is
often supplemented with other proxies (e.g., pollen or leaf assemblages)40 0.0 0.4 0.8
0 10 20
pAqpe spores (%)
Ulminite (%)
c) d)
31 n-alkane ratio, b) the relative abundance (total palynomorphs) of Sphagnum-type spores,
n-alkanes). Zero depth marks the top of Seam 1 and the base of the overlying interbed 2.
0 10 20
Inertinite (%)
 
240
260
280
220
200
40
20
0
-20
Silt
Clay 
Lignite
Silt lenses
D
ep
th
 b
el
ow
 
ov
e
rly
in
g 
m
a
rin
e 
in
te
rb
ed
s 
(cm
)
0 1 2
Zygnemataceae (%)Inaperaturopollenites (%)
0 20 40
Apectodinium 
spp. (%)
0 20 40
 
0 10 20 
Laevigatosporites (%)
0 5 10
 
Fichtelite 
(µg/g dry sediment)
2927
ACL27-33
a) e) f)d)c)b)
Fig. 8. Key plant groups, hydrology and sea level inundation within Seam 1, Schöningen. The relative abundance (total palynomorphs) of a) Inaperaturopollenites (swamp conifer pollen) and
b) Laevigatosporites (fern spores), c) Fichtelite (conifer biomarker), d) Inertinite (fossil charcoal), e) C27–C33 n-alkane average chain length (ACL) and f) the relative abundance (total
palynomorphs) of the dinoflagellate Apectodinium (grey) and freshwater green algal cysts of the family Zygnemataceae (blue). Zero depthmarks the top of Seam1 and the base of the overlying
interbed 2. Petrology data (inertinite) has only been obtained for lignite.
251G.N. Inglis et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 438 (2015) 245–255to reconstruct vegetation change during the Holocene (e.g., Nott et al.,
2000). Here we compare biomarker and palynological downcore trends
in order to investigate the distribution and occurrence of Sphagnum
moss within an early Paleogene, peat-forming environment.
Spores assigned to Sphagnummoss are present in most seams of the
early Eocene Schöningen Formation (Riegel et al., 2012). They are most
commonly represented by Tripunctisporis, a former subgenus of the
invalid genus Stereisporites; however, at least three to four morphotaxa
of Sphagnum-type spores can be distinguished (i.e., Tripunctisporis and
Distancoraesporis plus a number of forms more closely resembling
modern Sphagnum spores; Fig. 6). Tripunctisporis differs slightly from
spores of modern Sphagnum, but its co-occurrence with charred
remains of Sphagnum-leaves in a thin lignite seam within interbed 4
(Riegel et al., 2012) confirms a likely Sphagnum origin as originally
suggested by Döring et al. (1966). The proportion in which Sphagnum-
type spores contribute to the frequency curve (Fig. 7) varies without
any obvious pattern to it. However, Tripunctisporis andDistancoraesporis
dominate in most of the samples. Sphagnum-type spores are low or
absent within the base of Seam 1 (200–267 cm; b10%). This is consistent
with low C23/C31 n-alkane values (~0.4) which indicate that Sphagnum
moss was probably not an important component of the peat-forming
vegetation within this interval (Fig. 7). The pAq ratio (Fig. 7d), which
can also be used to infer changes in Sphagnum occurrence and local
hydrology (Nichols et al., 2006), averages 0.27 and ranges from 0.13 to
0.50 within the base of Seam 1 (200–267 cm). This suggests mixed
input from terrestrial higher plants, dominated by C29 and C31
n-alkanes, and Sphagnum moss, dominated by C23 and C25 n-alkanes.
Submerged and/or floating freshwater aquatic macrophytes can also
producemid-chain n-alkanes andmay contribute towards the observed
pAq values (Ficken et al., 2000).
Within the top of Seam 1 (0–57 cm), Sphagnum-type spores increase
significantly and comprise 20 to 50% of the entire palynological
assemblage. During the same interval, the C23/C31 n-alkane ratio
increases (~1.6) and yields values that are typical of a modern,
Sphagnum-dominated bog (Nott et al., 2000; Pancost et al., 2002; Xie
et al., 2004; Bingham et al., 2010). The similarity between biomarkers
and palynology (Fig. 7) provides compelling evidence that Sphagnummoss was an important peat-forming plant within the top of Seam 1
(0–57 cm) and that the C23/C31 n-alkane ratio is a reliable chemotaxo-
nomic indicator for Sphagnum input during the early Paleogene.
Sphagnum expansion coincides with an increase in the pAq ratio (0.52
to 0.79; Fig. 7d) and a decrease in the n-alkane average chain length
(ACL; Fig. 8e). The latter is consistent with modern studies which exhibit
a similar decrease during the transition from Ericaceae to Sphagnum-
dominated peat (Pancost et al., 2003).
Sphagnum-type spores are typically absent (Collinson et al., 2009) or
rare (Wilson and Webster, 1946; Nichols and Traverse, 1971; Jardine
and Harrington, 2008) within early Paleogene peat-forming environ-
ments. However, the similarity between Sphagnum biomarkers and
Sphagnum-type spores within Seam 1, suggests a deeper evolutionary
origin for Sphagnum moss. This is supported by the identification of
Sphagnum leaves and/or spores in other Cenozoic (Jie and Xiuyi, 1986)
and Mesozoic (Lacey, 1969) terrestrial settings.4.2. Environmental controls on Sphagnum occurrence within Seam 1,
Schöningen
In modern settings, Sphagnum is adapted to acidic, waterlogged and
nutrient-limited environments and its occurrence is largely controlled by
changes in local hydrology (van Breemen, 1995). To assess the role of
hydrological change upon ancient Sphagnum occurrence, we use bio-
markers, palynology and petrological evidence to constrain hydrological
and environmental change within Seam 1.
While the low abundance of Sphagnum-type spores and biomarkers
within the base of Seam 1 (200–267 cm; Fig. 7) suggests relatively dry
conditions (Clymo, 1984), lignite macerals can provide further insights
into local hydrological change. Attrinite, which forms in relatively dry
conditions at the mire surface (Sýkorová et al., 2005), is the most abun-
dant maceral within the base of Seam 1 (~34%) and suggests relatively
dry conditions. Textinite, which also forms in relatively dry, possibly
low pH environments within forested peatlands and/or raised bogs
(Sýkorová et al., 2005), is similarly abundant within the base of Seam
1 (~27%) and indicates a relatively dry environment.
m)
 
b.
-36 -32 -28 -24
δ13C 
hopanes (‰)
252 G.N. Inglis et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 438 (2015) 245–255Within the top of Seam1, between 57 and 46 cm, there is a transient
increase in conifer biomarkers (e.g., fichtelite: Fig. 8c) and fern spores
(e.g., Laevigatosporites spp.; Fig. 8b), likely indicating the expansion of
conifer forestswith a fern understory. This is associatedwith an increase
in the relative abundance of inertinite (i.e., fossil charcoal), suggesting
increased wildfire activity. Between 46 and 20 cm, there is an increase
in the relative abundance of Sphagnum-type spores (N20%) and
C23/C31 n-alkane ratios (N1) (Fig. 7a, b) indicating the development
of waterlogged, nutrient-limited conditions. This is consistent with
other early Paleogene, peat-forming environments where Sphagnum-
type spores proliferate following changes in basin subsidence and
drainage (Pocknall, 1987). Ulminite, which forms in wet, low pH condi-
tions within forested peatlands or raised bogs (Sýkorová et al., 2005),
correlates with the relative abundance of Sphagnum-type spores
throughout the top of Seam 1 (Fig. 7b,c) and provides additional
evidence that Sphagnum occurrence was driven by the expansion of
waterlogged conditions. Although some Sphagnum taxa can thrive in
more mesotrophic, low-lying swamps (e.g., Sphagnum russowii or
Sphagnum riparium), the abundance of ulminite and the distribution
of bacterial hopanoids is more consistent with an acidic, oligotrophic
peat-forming environment (see later). Inertinite relative abundance
remains high throughout this upper part of the seam (Fig. 8d). This sug-
gests that fire activity may have played a role in maintaining Sphagnum
relative abundance by impeding the spread of taller, hence more vul-
nerable, vascular plants across the bog surface.
The relative abundance of Sphagnum-type spores (b30%) and the
C23/C31 n-alkane ratio (b2) decreases within the very top of Seam 1
(20–0 cm). This interval coincides with a decrease in the n-alkane ACL
and the incursion of green algae (Zygnemataceae — Fig. 8f) associated
with standing freshwater environments. This suggests that freshwater
flooding restricted the growth of higher plants and, to a lesser extent,
mosses. Peat-deposition is eventually terminated by a brackish, shallow-
water incursion as indicated by the presence of Apectodinium — Fig. 8f, a
marine dinoflagellate cyst associated with shallow subtropical waters,
within interbed 2. Sea level inundation was either driven by changes in
local basin subsidence (i.e., an increase in accommodation space)
associated with regional passive salt withdrawal towards the
Helmstedt-Stassfurt Salt Wall during the early and middle Eocene
(Brandes et al., 2012), changes in terrestrial run-off associated with a
warmer climate (Slotnick et al., 2012) and/or eustatic sea level rise
(Riegel et al., 2012).Silt
Clay 
Lignite
Silt lenses
-20
0
20
40
10
30
50
-10
-30
D
ep
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in
g 
m
ar
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in
te
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ed
s 
(c C31 ββ
C31 αβ
-32 -30 -28 -26
δ13C (‰)
Fig. 9. Isotopic change within the top of Seam 1 (0–57 cm) and the overlying marine inter-
beds (0–36 cm). a) Bulk δ13CV-PDB values (Corg; black diamonds) and compound-specific
isotope δ13CV-PDB values formid- and long-chainn-alkanes (C23; green circles, C25; red circles,
C27; blue circles, C29; black circles). b) Compound-specific isotope δ13CV-PDB values for
bacterial-derived hopanes. Zero depth marks the top of Seam 1 and the base of the
overlying interbed 2.4.3. Insights into the biogeochemistry of Paleogene ombrotrophic bogs
Modern ombrotrophic bogs are characterised by a distinct microbial
assemblage that is associated with the unusual dominance of the C31
17α,21β(H) homohopane (Quirk et al., 1984; Dehmer, 1993, 1995;
Pancost and Sinninghe Damsté, 2003). This isomer is common in high
maturity sediments (Seifert andMoldowan, 1980) and, with the excep-
tion of the soil bacterium Frankia spp. (Rosa-Putra et al., 2001), is not
synthesised by living organisms. Its occurrence within modern peat
deposits has therefore been attributed to rapid isomeric catalysation at
the C-17 position as a result of acidic conditions (van Dorselaer et al.,
1975; Dehmer, 1993, 1995; Pancost et al., 2003), although a biological
origin remains possible. The ratio of the C31 17β,21β(H) homohopane to
total homohopanes (=ββ/αβ + ββ) in modern peats ranges from
b0.01 to 0.85 and averages ~0.1 (Pancost et al., 2003; Inglis, G. unpub-
lished). Within Seam 1, Schӧningen, the C31 17α,21β(H) homohopane
is the dominant hopane (Fig. 3) and the ββ/αβ+ ββ ratio ranges from
to 0.16 to 0.57, averaging 0.27. The C31 17α,21β(H) homohopane is also
a major constituent of other thermally immature Cenozoic lignites
(Dehmer, 1988; Pancost et al., 2007). This suggests that diagenetic
reactions and/or bacterial communities within Seam 1 and other
ancient peat-forming environments are similar to those of Holocene
wetlands. By extension, in relatively immature, marginal marinesediments, low ββ/αβ + ββ ratios could also serve as a useful new
proxy for the input of peat (or eroded lignite).
The δ13C values of bacterial hopanoids can also provide insights into
microbial methane cycling. The carbon isotopic composition (δ13C) of the
C31 17α,21β(H) homohopane in modern Sphagnum-dominated bogs is
typically enriched in 13C (−22 to−26‰) relative to bulk organic matter
and plant-derived n-alkanes (Pancost et al., 2000; Inglis, G. unpublished).
This likely indicates a heterotrophic bacterial population consuming
13C-enriched carbohydrates (Pancost et al., 2000; Xie et al., 2004). In the
same setting, the δ13C value of C32 17β,21β(H) bishomohopanol is
lower, ranging from−27‰ to−30‰, perhaps suggesting a mixed suite
of bacterial sources consuming both 13C-enriched carbohydrates and
13C-depleted, methane-derived CO2 (Pancost et al., 2000). In some
cases, however, the δ13C value of extended hopanoids can be depleted
in 13C; in particular, van Winden et al. (2010) reported δ13C values of
C32 ββ bishomohopanol in extant Sphagnum species ranging from
−34‰ to−37‰, suggesting that they partially derive from symbiotic
methanotrophs. The lowest modern δ13C values are derived from
diploptene (C30 17β, 21β (H)-hop-22(29)-ene) within a Carex-
dominated bog where δ13C values range between 31.6‰ and−50.3‰
(Zheng et al., 2014).
In another Paleogene wetland deposit, the Cobham Lignite (~56 Myr
ago), the δ13C values of the C29- and C31-17β(H),21β(H) hopane decrease
dramatically (to values as low as −76‰ and −42‰, respectively) in
response to freshwaterflooding and indicates the consumptionof isotopi-
cally lightmethane by aerobicmethanotrophs (Pancost et al., 2007). Such
values have yet to be observed in a modern or Holocene peat deposit,
but they are consistent with modelled wetland methane emissions,
which suggest a ~6- to 7-fold increase during Paleogene warm climates
(Beerling et al., 2011). To investigate this further, we generate hopane
δ13C values within the top of Seam 1 and use this to reconstruct the
relative amount of aerobic methanotrophy within an early Paleogene,
peat-forming environment.
Within the top of Seam1 the δ13C value of the C31 17α,21β(H) hopane
ranges between−24.9‰ and−28.3‰ (Fig. 9b). These values are similar
253G.N. Inglis et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 438 (2015) 245–255to those observed in modern ombrotrophic bogs (−22‰ to−26‰;
Pancost et al., 2000) and suggest a similar source organism and
ecology. The δ13C value of the C30- and C31-17β,21β(H) hopane
ranges between −28 and −32‰ (Figs. 5 and 9b). These values are
persistently 2–10‰ lighter than modern C31 17α,21β(H) hopane δ13C
values and are more consistent with modern C32 ββ bishomohopanol
δ13C values (−27‰ to−30‰; Pancost et al., 2000). This suggests that
the C30- and C31-17β,21β(H) hopanes are derived from a mixed
methanotrophic and heterotrophic bacterial population (van Winden
et al., 2012). Such relatively low values persist through the top 54 cm
of Seam 1 – likely reflecting 1.8 to 4.7 kyr – and could indicate a some-
what more intense methane cycling regime than observed in boreal
Holocene bogs (cf. Pancost et al., 2000). However, unlike the Cobham
Lignite (Pancost et al., 2007) or even some Holocene studies (Zheng
et al., 2014), very low δ13C hopane valueswere not observed suggesting
that the top of Seam 1 was not characterised by extensive aerobic
methanotrophy. Hopane δ13C values are relatively invariant throughout
the top of Seam 1, despite an increase in Sphagnum abundance and
waterlogged conditions (see Section 4.1). This could potentially be
attributed to the absence of symbiotic methane-oxidising bacteria
(Raghoebarsing et al., 2005; Kip et al., 2010). Alternatively, the
incursion of sulphate-rich marine waters may suppress the rate of
methanogenesis (Whiticar, 1999). This hypothesis is consistent
with the presence of Apectodinium within the overlying marine in-
terbeds and high elemental sulphur concentrations throughout the
seam (3.9–7.6 wt.%; Fig. 2c) (Chou, 2012). Recent work has also
shown that low δ13C hopane values are not necessarily associated
with an increase in waterlogged conditions (cf. Van Winden et al.,
2012). For example, Zheng et al. (2014) show that low δ13C hopane values
(−42‰ to−50‰) are associated with a pronounced dry interval during
the mid-Holocene. This likely reflects changes in methane flux pathways
and more efficient methane oxidation under drier conditions (Zheng
et al., 2014). By extension, the absence of very low δ13C hopane values
at Schöningen could reflect less efficientmethane oxidation underwetter
conditions (cf. Zheng et al., 2014).
In modern, ombrotrophic, Sphagnum-dominated bogs, the carbon
isotopic composition of the C23 n-alkane can also provide insights
into the amount of aerobic methanotrophy. In modern bogs, the C23
n-alkane can be depleted in 13C (~5–10‰) relative to high molecular
weight (C29–C33) n-alkanes (Brader et al., 2010; van Winden et al.,
2010; Huang et al., 2014), suggesting incorporation of 13C-depleted,
CH4-derived CO2 associated with aerobic methanotrophy (Kip et al.,
2010; van Winden et al., 2010). However, in other ombrotrophic
bogs, the C23 n-alkane does not exhibit 13C-depleted values (−30‰
to −33‰; Pancost et al., 2003). In the same study, mid-chain n-
alkanols, which can also be derived from Sphagnum, did not exhibit
13C-depleted values, ranging from−30‰ to−33‰ (e.g., Pancost et al.,
2003).Within the top of Seam 1, the δ13C value of the C23 n-alkane ranges
from−28.7‰ to−30.6‰. These values are 13C-enriched (1–2‰) relative
to HMW n-alkanes (−30.1‰ to −32.5‰) and are consistent with a
partially submerged source (Ficken et al., 2000; Pancost et al., 2003).
This indicates relatively low rates of aerobic methanotrophy within
Seam 1 despite overall wetter conditions. Both mid- and long-chain
n-alkanes exhibit gradual 13C-depletion towards the top of Seam 1,
consistent with bulk δ13C values (Fig. 9a). During the same interval,
hopane δ13C values remain relatively invariant. This suggests that
mid- and long-chain n-alkane 13C-depletion cannot be attributed to
a rise in the water table but instead may be the consequence of
some other mechanism (e.g., changes in CO2, plant growth rate and/or
temperature). Collectively, both hopanes and mid-chain n-alkanes
do not indicate significantly enhancedmethanotrophy in this early Paleo-
gene, peat-forming environment, in contrast to the Cobham lignite
(Pancost et al., 2007). The reason for this remains unclear but may be
related to site-specific differences. For example, the top of Seam 1,
Schöningen suggests the presence of intermittent marine conditions.
This is based upon high elemental sulphur concentrations (N4% wt.)and the presence of silt and/or sand lenses (Figs. 2c and 7). In contrast,
the Cobham lignite sequence was deposited under a freshwater
environment as indicated by the absence of dinoflagellate cysts and
Ophiomorpha burrows and the presence of freshwater wetland flora
(Collinson et al., 2009). Despite this, the biogeochemical response
associated with flooding ancient peat-forming environments remains
poorly constrained and requires further investigation.
These results indicate the complexity of methane cycling within
ancient peat-forming environments; however, changes in methane
concentrations remain an important positive feedback mechanism
during the early Eocene. For example, earth system modelling simula-
tions indicate that early Eocene methane emissions may have been up
to 6× greater than the modern. This can account for up to ~6 °C of
high-latitude warming (Beerling et al., 2011) and has implications for
numerical model studies which often fail to replicate high-latitude,
proxy-derived temperature estimates (Huber and Sloan, 2001; Hollis
et al., 2012; Lunt et al., 2012). Enhanced methane emissions can also
promote the formation of thick, polar stratospheric clouds (Sloan and
Pollard, 1998) which may account for enhanced high-latitude warmth
during the early Eocene and other greenhouse intervals (Sloan et al.,
1992).
5. Conclusion
Using a high-resolution, multi-proxy approach, we reconstruct
the occurrence of Sphagnum moss within an early Paleogene peat-
forming environment (Seam 1, Schöningen Mine, Germany). C23/
C31 n-alkane ratios (b0.4) and the relative abundance of Sphagnum-
type spores (especially Tripunctisporis) are low within the base of
Seam 1 (200–267 cm), indicating that Sphagnumwas not an important
peat-forming plant during this interval. Within the top of Seam 1
(57–0 cm), C23/C31 n-alkane ratios increase and are comparable to, or
exceed, values from modern, Sphagnum-dominated ombrotrophic
bogs. This coincides with an increase in the relative abundance of
Sphagnum-type spores which comprise up to 45% of the entire palyno-
logical assemblage. Our results show a close association between
Sphagnum biomarkers and Sphagnum-type spores within an early Pa-
leogene peat-forming environment, analogous to what has been
observed during the Holocene, and suggest that the C23/C31 n-alkane
ratio may be a reliable chemotaxonomic indicator for Sphagnum input
during the early Paleogene. Changes in biomarkers, palynology and
petrology indicate that Sphagnum proliferation was driven by an
increase in waterlogged conditions within the top of Seam 1. Increased
fire activity may also have played a role by reducing re-colonisation by
vascular plants. In comparison to other early Paleogene peat-forming
environments, the δ13C value of bacterial hopanes and plant-derived
n-alkanes do not indicate significant aerobic methanotrophy. Nor do
they indicate a change in methanotrophy despite a rise in the water
table. The reason for this difference remains unclear but may be linked
to the incursion of sulphate-rich, marine waters which might inhibit
methanogenesis and/or reduce the efficiency of methane oxidation.
Acknowledgements
We thank the NERC Life Sciences Mass Spectrometry Facility (Bristol)
for analytical support and GNI thanks the NERC for supporting his PhD
studentship (NE/I005714/1). RDP acknowledges the Royal Society
Wolfson Research Merit Award. We gratefully acknowledge funding to
Collinson and Robson from the NERC grant NE/J008656/1 and to Pancost
from NERC grant NE/J008591/1. We thank Jim Hower (University of
Kentucky) for production of polished blocks of crushed lignite, Karin
Schmidt (Senckenberg Forschungsinstitut und Naturmuseum, Frankfurt)
for extensive logistical support, especially during field work, Nathalie
Grassineau (Earth Sciences, Royal Holloway) for running the bulk carbon
isotope samples and David Naafs and Marcus Badger for comments on
earlier versions of this manuscript. Finally, we also thank both reviewers
254 G.N. Inglis et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 438 (2015) 245–255for constructive comments which helped to improve the quality of this
manuscript.
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