TY - JOUR
T1 - Lipid biomarker patterns of methane-seep microbialites from the Mesozoic convergent margin of California
AU - Birgel, Daniel
AU - Thiel, Volker
AU - Hinrichs, Kai Uwe
AU - Elvert, Marcus
AU - Campbell, Kathleen A.
AU - Reitner, Joachim
AU - Farmer, Jack
AU - Peckmann, Jörn
N1 - Funding Information:
We thank Michael Böttcher and Steven Bouillon for editorial work and Richard Pancost (Bristol) as well as an anonymous reviewer for helpful comments on the manuscript. Financial support was provided by the ‘Deutsche Forschungsgemeinschaft’ through the DFG-Research Center for Ocean Margins, Bremen (RCOM Contribution 0362) and Grant PE 847/4. KAC collected materials during a US National Research Council Associateship, administered through NASA Ames Research Center; drafting support by L. Cotterall, University of Auckland, Geology Department.
PY - 2006/10
Y1 - 2006/10
N2 - In order to reconstruct biogeochemical pathways at Mesozoic methane-seeps, a set of Late Jurassic (Tithonian) to Early Cretaceous (Aptian/Albian), 13C-depleted seep-limestones from forearc strata in western California were subjected to detailed molecular-isotopic biomarker analyses. Two of the microbial carbonate deposits are turbidite-hosted/fault-related, whereas one is hosted in serpentinite in a diapir-related setting. The limestones contain 13C-depleted archaeal lipid biomarkers such as crocetane (δ13C ∼ -80‰) and PMI (∼ -100‰), indicative of an involvement of anaerobic oxidation of methane (AOM) in carbonate precipitation. Isotopically depleted crocetane in the Tithonian sample represents the oldest reported occurrence of this compound at methane-seeps. In the set of samples, a series of strongly 13C-depleted, regular C21 to C24 isoprenoids possibly results from diagenetic alteration of archaeal sesterterpanylglycerol diethers as suggested by the presence of the putative intermediate 3,7,11,15,19-pentamethylicosanoic acid. 13C-depleted 17α(H),21β(H) and 17β(H),21α(H)-hopanes (C30-C34) with 22S- and 22R- isomer couplets (>C31) are present in all samples in distributions indicative of a moderate thermal maturity. Low δ13C values (-78‰ to -60‰) suggest that these are derived from anaerobic bacteria involved in AOM. Notably, 22S-isomers are consistently enriched in 13C relative to their 22R-counterparts. Our samples represent 70 myr of seepage activity and AOM along the Mesozoic margin of western California, filling the gap between the currently oldest methane-seep biomarker record from the Oxfordian (Late Jurassic) and the more widely recognised Cenozoic examples.
AB - In order to reconstruct biogeochemical pathways at Mesozoic methane-seeps, a set of Late Jurassic (Tithonian) to Early Cretaceous (Aptian/Albian), 13C-depleted seep-limestones from forearc strata in western California were subjected to detailed molecular-isotopic biomarker analyses. Two of the microbial carbonate deposits are turbidite-hosted/fault-related, whereas one is hosted in serpentinite in a diapir-related setting. The limestones contain 13C-depleted archaeal lipid biomarkers such as crocetane (δ13C ∼ -80‰) and PMI (∼ -100‰), indicative of an involvement of anaerobic oxidation of methane (AOM) in carbonate precipitation. Isotopically depleted crocetane in the Tithonian sample represents the oldest reported occurrence of this compound at methane-seeps. In the set of samples, a series of strongly 13C-depleted, regular C21 to C24 isoprenoids possibly results from diagenetic alteration of archaeal sesterterpanylglycerol diethers as suggested by the presence of the putative intermediate 3,7,11,15,19-pentamethylicosanoic acid. 13C-depleted 17α(H),21β(H) and 17β(H),21α(H)-hopanes (C30-C34) with 22S- and 22R- isomer couplets (>C31) are present in all samples in distributions indicative of a moderate thermal maturity. Low δ13C values (-78‰ to -60‰) suggest that these are derived from anaerobic bacteria involved in AOM. Notably, 22S-isomers are consistently enriched in 13C relative to their 22R-counterparts. Our samples represent 70 myr of seepage activity and AOM along the Mesozoic margin of western California, filling the gap between the currently oldest methane-seep biomarker record from the Oxfordian (Late Jurassic) and the more widely recognised Cenozoic examples.
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U2 - 10.1016/j.orggeochem.2006.02.004
DO - 10.1016/j.orggeochem.2006.02.004
M3 - Article
AN - SCOPUS:33748917516
SN - 0146-6380
VL - 37
SP - 1289
EP - 1302
JO - Organic Geochemistry
JF - Organic Geochemistry
IS - 10
ER -