25th International Meeting on Organic Geochemistry IMOG 2011

O-57
Exploring mass extinction events (Triassic/Jurassic and
Permian/Triassic): Association with global warming events
Kliti Grice 1 , Birgit Nabbefeld 1 , Richard Twitchett 2 , Lindsay Hays 3 , Kenneth Williford 1 , Alex
Holman 1 , Roger Summons 3 , Jennifer McElwain 4 , Michael Böttcher 5
1 Curtin University, Perth, Australia, 2 Plymouth University, Plymouth, United Kingdom, 3 Massachusetts
Institute of Technology, Cambridge, United States of America, 4 University College Dublin, Dublin, Ireland,
5 Leibniz Institute for Baltic Sea Research, Warnemünde, Germany (corresponding
author:K.Grice@curtin.edu.au)
The Late Permian mass extinction event was the
most profound extinctions of the entire Phanerozoic.
Biomarker evidence for photic zone euxinic (PZE)
conditions within Permian/Triassic (P/Tr) setions,
where concentrations of sulfide, are sufficient to
support anoxygenic photosynthesis, come from
components derived from pigments of Chlorobi (Grice
et al., 2005; Hays et al., 2007; Nabbefeld et al., 2010).
Evidence for such conditions occurs at 6 localities
globally. Perturbations in the marine sulfur cycle and
thus the redox-state of the ancient seas are also
reflected in � 34 S of pyrite (e.g. from China, Italy, Iran,
Western Australia, East Greenland, Western Canada
and Spitsbergen) supporting widespread euxinic
conditions in both Palaeotethys and Panthalassa
oceans (e.g. Grice et al., 2005; Hays et al., 2007).
The aromatic biomarkers, dibenzothiophene,
dibenzofuran and biphenyl have been detected in
high abundances in samples prior to the marine
ecosystem collapse in East Greenland, Spitsbergen,
South China and Western Canada (e.g. Nabbefeld et
al., 2010). We have proposed that lignin derived from
land plants, present during the Late Permian is their
likely source. We provide sedimentological data,
biomarker abundances and compound specific
isotopic data (� 13 C and �D) along with bulk isotopes
(� 34 Spyrite, � 13 Ccarbonate, � 13 Corg) for several Late
Permian sections. At two localities sedimentological
and geochemical data supports a marine
transgression and collapse of the marine ecosystem
occurring in the Late Permian (Nabbefeld et al.,
2010). δ 13 C data of algal and land-plant derived
biomarkers, δ 13 C carbonate & organic matter support
synchronous changes in δ 13 C of marine and
atmospheric CO2, attributed to a 13 C-depleted source
( 13 C depleted methane and/or CO2 derived from
degradation of organic matter due to the marine
ecosystem collapse- Nabbefeld et al., 2010).
Evidence for waxing and waning of PZE throughout
the Late Permian is provided by Chlorobi derived
biomarkers and � 34 S pyrite implying multiple phases
of H2S outgassing and potentially several prolonged
pulses of extinction at several global localities. We
suggest that high levels of CO2 and H2S were the
drivers of the extinction. The Triassic/Jurassic (Tr/J)
extinction is regarded as being the fourth most acute
extinction event of the Phanerozoic in terms of
ecological impact. A number of mechanisms have
been proposed to account for the mass extinction,
including the release of CO2 associated with
emplacement of the Central Atlantic Magmatic
Province (CAMP). A negative carbon isotope
excursion has been detected in many sections, also
supporting a perturbation in the global carbon cycle. It
is clear that major and abrupt ecological change
including 80% extinction among terrestrial plant
species coincides with increased atmospheric CO2
concentration (CO2atm, based on stomatal analysis of
fossil Ginkoales leaves) and a negative excursion in
� 13 C of fossil wood from a Tr/J section at Astartekløft,
East Greenland. We have evidence for carbon cycle
perturbation, extreme heat stress and fire in the form
of molecular and compound specific stable isotopic
compositions of biomarkers from the boundary
section. Decreasing � 13 C and increasing �D of
terrestrial plant wax lipids together with increases in
combustion ascribed polycyclic aromatic
hydrocarbons, charcoal and gymnosperm resin
derivatives co-occur with ecosystem decline (Williford
et al., 2011).
References
Grice K, Cao C, Love GD, Bottcher ME, Twitchett R,
Grosjean E, Summons R, Turgeon S, Dunning W,
Jin Y 2005. Photic Zone Euxinia During the
Permian-Triassic Superanoxic Event. Science 307,
706-709.
Nabbefeld B, Grice K, Twitchett RJ, Summons RE,
Hays L, Böttcher ME, Muhammad A 2010. An
integrated biomarker, isotopic and
palaeoenvironmental study through the Late
Permian event at Lusitaniadalen, Spitsbergen. Earth
and Planetary Science Letters 291, 84-96.
Williford KH, Grice K, Holman A, McElwain JC.
Molecular and stable isotopic signatures of extreme
heat stress at the Triassic/Jurassic Boundary Nature
Geoscience Submitted Jan 2011.
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