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| Titel |
Insights into peatland expansion and methane cycling on the East Antarctic continent in the early Eocene |
| VerfasserIn |
J. L. Toney, J. A. Bendle, O. Seki, S. Krishnan, M. Pagani, G. Inglis, R. Pancost, P. K. Bijl, S. Bohaty, S. Schouten, J. Pross, H. Brinkhuis, U. Roehl, S. Jamieson |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250065982
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| Zusammenfassung |
| The high temperature, high pCO2 world of the early Eocene (~55 to 49 Ma) greenhouse may
be an analogue for the future response of the biosphere and global carbon cycle to recent
anthropogenic, atmospheric CO2 forcing. Here we present an early Eocene record
showing that the expansion of peatlands and methanogenesis in coastal wetlands on
Antarctica was an important part of the carbon cycle in this greenhouse world.
Terrestrial biomarkers were analyzed from IODP Expedition 318 - Site U1356A,
situated along the Wilkes Land margin of East Antarctica. Bacterial-derived, C31
(17α,21β) homohopane within a relatively immature hopane assemblage from
Site U1356A suggests that wetland environments were present on the Antarctica
continent in the early Eocene. Fluctuations in the concentrations and the molecular
structure – the ββ/(αβ + ββ) ratio – indicate that the extent of these wetlands
fluctuated in a coherent way, suggestive of an external forcing, presumably orbital. The
compound-specific carbon isotope values (δ13C) of hopanes are consistently 5 to 10 permil
lower than those of the higher plant n-alkanes, which suggest that the bacterial precursor
organisms were likely a mixture of heterotrophs and methanotrophs. The long-term
trends in these biomarker parameters are consistent with changes in the sea-surface
temperatures recorded by the TEX86H proxy and suggest an important role for
methanogenesis in wetlands on the early Eocene, Antarctic continent. We compare the
hopane biomarker results with compound-specific, hydrogen-isotope measurements on
higher plant n-alkanes and conclude that these wetland changes indicate an enhanced
hydrological cycle in the southern high latitudes. We are currently exploring new
biomarker data from other Southern Ocean, early Eocene sites proximal to the
Antarctic margin to determine if the orbitally-driven expansion of peatlands along the
Wilkes Land margin, East Antarctica applies to the whole of the Antarctic coastal
environment, or if the peatland dynamics were specific to the Wilkes Land margin. |
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