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271.
Okenane, a biomarker for purple sulfur bacteria (Chromatiaceae), and other new carotenoid derivatives from the 1640 Ma Barney Creek Formation 总被引:1,自引:0,他引:1
Carbonates of the 1640 million years (Ma) old Barney Creek Formation (BCF), McArthur Basin, Australia, contain more than 22 different C40 carotenoid derivatives including lycopane, γ-carotane, β-carotane, chlorobactane, isorenieratane, β-isorenieratane, renieratane, β-renierapurpurane, renierapurpurane and the monoaromatic carotenoid okenane. These biomarkers extend the geological record of carotenoid derivatives by more than 1000 million years. Okenane is potentially derived from the red-colored aromatic carotenoid okenone. Based on a detailed review of the ecology and physiology of all extant species that are known to contain okenone, we interpret fossil okenane as a biomarker for planktonic purple sulfur bacteria of the family Chromatiaceae. Okenane is strictly a biomarker for anoxic and sulfidic conditions in the presence of light (photic zone euxinia) and indicates an anoxic/oxic transition (temporarily) located at less than 25 m depth and, with a high probability, less than 12 m depth.For the BCF, we also interpret renierapurpurane, renieratane and β-renierapurpurane as biomarkers for Chromatiaceae with a possible contribution of cyanobacterial synechoxanthin to the renierapurpurane pool. Although isorenieratane may, in principle, be derived from actinobacteria, in the BCF these biomarkers almost certainly derive from sulfide-oxidizing phototrophic green sulfur bacteria (Chlorobiaceae). Biological precursors of γ-carotane, β-carotane and lycopane are found among numerous autotrophic and almost all phototrophic organisms in the three domains of life. In the BCF, a paucity of diagnostic eukaryotic steroids suggests that algae were rare and, therefore, that cyanobacterial carotenoids such as β-carotene, echinenone, canthaxanthin and zeaxanthin are the most likely source of observed β-carotane. γ-Carotane may be derived from cyanobacteria, Chlorobiaceae and green non-sulfur bacteria (Chloroflexi), while the most likely biological sources for lycopane in the BCF are carotenoids of the lycopene, rhodopin and spirilloxanthin series abundant in purple sulfur bacteria. 相似文献
272.
Jochen Knies 《Geochimica et cosmochimica acta》2005,69(19):4631-4647
With this study, I suggest that changes in biogeochemical processes in northern Norwegian fjords during the last glacial/interglacial transition (14.3 to 6.3 ka B.P.) are predominantly climate induced. Variable strength in Atlantic water inflow, intrusion of Arctic waters and sea-ice coverage, various nutrient supply, as well as several re-advances of continental ice-sheets are recorded by both bulk organic and selected biomarkers in sediments of the Andfjord. Stable isotope (δ13Corg, δ15N) and Rock-Eval pyrolysis data indicate a strong supply of terrestrial organic matter during stadials (e.g., Younger Dryas, Older Dryas) whereas enhanced input of marine organic matter prevailed during the interstadials (Bølling/Allerød). Profiles of selected biomarkers of marine origin show a characteristic climate-induced variation during the whole time interval, where relatively low concentrations of dinosterols and C37 alkenones may indicate—similar to today—a minor contribution of their respective plankton groups (coccolithophorids, dinoflagellates). The prevalence of Arctic waters and seasonal sea-ice coverage during the Younger Dryas is indicated by a single maximum of 24-methylenecholesterol probably indicating the dominance of sea-ice diatoms and/or the prevalence of diatoms of Thalassiosiraceae in surface waters. The sediments of the Allerød, in contrast, show a pronounced maximum in dinosterols, indicating a better adaptation of dinoflagellates to an oceanic regime that is characterized by incipient intrusion of Atlantic water, highly variable sea surface temperatures, and well stratified water masses. The concentration of higher-molecular-weight n-alkanes, however, follows the deglacial-early Holocene trend of climate amelioration from the last deglaciation to the middle Holocene, with maxima during ice advances (stadials) and minima during the middle Holocene warm period.These new results significantly improve the understanding of climate-induced response on organic matter supply in fjords and provide a better knowledge of past variations of biogeochemical processes in high-latitude coastal environments. 相似文献