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| Titel |
Mesozoic authigenic carbonate deposition in the Arctic: Do glendonites record gas hydrate destabilization during the Jurassic? |
| VerfasserIn |
Chloé Morales, Guillaume Suan, Hubert Wierzbowski, Mikhail Rogov, Barbara Teichert, Michiel V. M. Kienhuis, Lubos Polerecky, Jack B. M. Middelburg, Gert-Jan Reichart, Bas van de Schootbrugge |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250114209
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| Publikation (Nr.) |
 EGU/EGU2015-14517.pdf |
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| Zusammenfassung |
| Glendonites are calcite pseudomorphs after ikaite, an unstable hydrated calcium carbonate
mineral. Because present-day ikaite occurs predominantly in sub-polar environments and
is unstable at warm temperatures, glendonites have been used as an indicator of
near-freezing conditions throughout Earth history. Ikaite has also been observed in
cold deep-sea environments like the Gulf of Mexico, the Japan Trench, and the
Zaire Fan where their formation is possibly governed by other parameters. The
description of glendonites in Paleocene-Eocene sediments of Svalbard, and Early Jurassic
(Pliensbachian) deposits of northern Germany, however questions the role of temperature on
ikaite precipitation (Spielhagen and Tripati, 2009; Teichert and Luppold, 2013).
Anomalously low carbon isotope values of Jurassic glendonites point to the involvement of
methane as a possible carbon source for ikaite/glendonite formation. Terrestrial organic
matter degradation is also frequently evoked as a potential source of carbon. The
involved bio- and geochemical processes remains thus not well constrained. Here we
present new geochemical data of a large number of glendonites specimens from the
Lower and Middle Jurassic of northern Siberia and the Lena river middle flows
(Bajocian, Bathonian, Pliensbachian). Carbon and oxygen isotopic values show
comparable trends between the different sections. Bulk glendonites δ13C and δ18O
values vary from 0.0 to -44.5oÂand -15.0 to -0.8 respectively and show a negative
correlation. Some samples display similar low δ13C values as the Pliensbachian
glendonites of Germany (Teichert and Luppold, 2013), suggesting thermogenic and/or
biogenic methane sources. The range of carbon isotope values is comparable to those
observed at other methane seeps deposits. Further investigations are needed to better
constrain the carbon cycle in these particular environmental conditions. The role of
microbial communities into ikaite/glendonite formation equally needs to be considered.
These results however caution the use of glendonites as a proxy for near-freezing
conditions.
References:
Spielhagen, R.F., Tripati, A., 2009. Evidence from Svalbard for near-freezing
temperatures and climate oscillations in the Arctic during the Paleocene and Eocene.
Palaeogeography, Palaeoclimatology, Palaeoecology 278, 48-56. Teichert, B.M.A.,
Luppold, F.W., 2013. Glendonites from an Early Jurassic methane seep—Climate
or methane indicators? Palaeogeography, Palaeoclimatology, Palaeoecology 390,
81-93. |
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