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| Titel |
Origin of lipid biomarkers in mud volcanoes from the Alboran Sea, western Mediterranean |
| VerfasserIn |
C. Lopez-Rodriguez, A. Stadnitskaia, G. J. De Lange, F. Martinez-Ruiz, M. Comas |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 11, no. 12 ; Nr. 11, no. 12 (2014-06-17), S.3187-3204 |
| Datensatznummer |
250117468
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| Publikation (Nr.) |
 copernicus.org/bg-11-3187-2014.pdf |
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| Zusammenfassung |
Mud volcanoes (MVs) are the most prominent indicators of active
methane/hydrocarbon venting at the seafloor on both passive and active
continental margins. Their occurrence in the western Mediterranean is patent
at the West Alboran Basin, where numerous MVs develop overlaying a major
sedimentary depocentre containing overpressured shales. Although some of
these MVs have been studied, the detailed biogeochemistry of expelled mud so
far has not been examined in detail. This work provides the first results on
the composition and origin of organic matter, anaerobic oxidation of methane
(AOM) processes and general characteristics on MV dynamics using lipid
biomarkers as the main tool. Lipid biomarker analysis was performed on MV
expelled material (mud breccias) and interbedded hemipelagic sediments from
Perejil, Kalinin and Schneider's Heart MVs located in the northwest margin of
the Alboran Sea. The n alkane distributions and n alkane-derived
indices (CPI and ACL), in combination with the epimerization degree of
hopanes (22S/(22S+22R)) indicate that all studied mud breccia have a
similar biomarker composition consisting of mainly thermally immature organic
matter with an admixture of petroleum-derived compounds. This concordant
composition indicates that common source strata must feed all three studied
MVs.
The past or present AOM activity was established using lipid biomarkers
specific for anaerobic methanotrophic archaea (irregular isoprenoids and
dialkyl glycerol diethers) and the depleted carbon isotope composition
(δ13C) of crocetane/phytane. The presence of these lipid
biomarkers, together with the low amounts of detected glycerol dialkyl
glycerol tetraethers, is consistent with the dominance of anaerobic
methanotrophs of the ANME-2 over ANME-1, at least in mud breccia from Perejil
MVs. In contrast, the scarce presence or lack of these AOM-related lipid
biomarkers in sediments from Kalinin and Schneider's Heart MVs, suggests that
no recent active methane seepage has occurred at these sites. Moreover, the
observed methane concentrations support the current activity of Perejil MV,
and the very low methane seepage activity in Kalinin and Schneider's Heart
MVs. |
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