Origin of lipid biomarkers in mud volcanoes from the Alboran Sea, western Mediterranean
López-Rodríguez, C.; Stadnitskaia, A.; De Lange, G.J.; Martínez-Ruíz, F; Comas, M.; Sinninghe Damsté, J.S. (2014). Origin of lipid biomarkers in mud volcanoes from the Alboran Sea, western Mediterranean. Biogeosciences 11: 3187-3204. http://dx.doi.org/10.5194/bg-11-3187-2014
In: Gattuso, J.P.; Kesselmeier, J. (Ed.) Biogeosciences. Copernicus Publications: Göttingen. ISSN 1726-4170; e-ISSN 1726-4189, more
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| Authors | | Top |
- López-Rodríguez, C.
- Stadnitskaia, A., more
- De Lange, G.J.
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- Martínez-Ruíz, F
- Comas, M.
- Sinninghe Damsté, J.S., more
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| Abstract |
Mud volcanoes (MVs) are the most prominentindicators of active methane/hydrocarbon venting at theseafloor on both passive and active continental margins.Their occurrence in the western Mediterranean is patent attheWest Alboran Basin, where numerous MVs develop overlayinga major sedimentary depocentre containing overpressuredshales. Although some of these MVs have been studied,the detailed biogeochemistry of expelled mud so farhas not been examined in detail. This work provides thefirst results on the composition and origin of organic matter,anaerobic oxidation of methane (AOM) processes and generalcharacteristics on MV dynamics using lipid biomarkersas the main tool. Lipid biomarker analysis was performedon MV expelled material (mud breccias) and interbeddedhemipelagic sediments from Perejil, Kalinin and Schneider’sHeart MVs located in the northwest margin of the AlboranSea. The n alkane distributions and n alkane-derived indices(CPI and ACL), in combination with the epimerization degreeof hopanes (22S/(22S+22R)) indicate that all studiedmud breccia have a similar biomarker composition consistingof mainly thermally immature organic matter with an admixtureof petroleum-derived compounds. This concordantcomposition indicates that common source strata must feedall three studied MVs.The past or present AOM activity was established usinglipid biomarkers specific for anaerobic methanotrophic archaea(irregular isoprenoids and dialkyl glycerol diethers)and the depleted carbon isotope composition (?13C) of crocetane/phytane. The presence of these lipid biomarkers, togetherwith the low amounts of detected glycerol dialkylglycerol tetraethers, is consistent with the dominance ofanaerobic methanotrophs of the ANME-2 over ANME-1, atleast in mud breccia from PerejilMVs. In contrast, the scarcepresence or lack of these AOM-related lipid biomarkers insediments from Kalinin and Schneider’s Heart MVs, suggeststhat no recent active methane seepage has occurred atthese sites. Moreover, the observed methane concentrationssupport the current activity of Perejil MV, and the very lowmethane seepage activity in Kalinin and Schneider’s HeartMVs. |
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