Hydrocarbon biomarkers from Ordovician sediments and the fossil alga Gloeocapsomorpha prisca Zalessky 1917 |
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| Institution: | 1. College of Fisheries and Life Science, Dalian Ocean University, No.52 Heishijiao Street, Shahekou district, 116023, Dalian, Liaoning, People’s Republic of China;1. Department of Infectious Disease, Cleveland Clinic Foundation, Cleveland, OH;2. Department of Laboratory Medicine, Infectious Disease Pathology & Clinical Microbiology, Cleveland Clinic Foundation, Cleveland, OH;3. Center for Pediatric Infectious Diseases, Cleveland Clinic Children''s Hospital, Cleveland, OH;4. Department of Emergency Management, Cleveland Clinic Foundation, Cleveland, OH;1. School of Ocean Sciences, College of Natural Sciences, Bangor University, Menai Bridge, Anglesey LL59 5AB, UK;2. Centre for Environmental Geochemistry, British Geological Survey (BGS), Nottingham NG12 5GG, UK;3. Edinburgh Ion Microprobe Facility (EIMF), School of Geosciences, Grant Institute, Edinburgh University, Edinburgh EH9 3FE, UK;4. Diamond Light Source, Diamond House, Harwell Science and Innovation Campus, Fermi Ave, Didcot OX11 0DE, UK;5. Centre for Environment, Fisheries and Aquaculture Science (CEFAS), Pakefield Road, Lowestoft, Suffolk NR33 0HT, UK;1. CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China;2. University of Chinese Academy of Sciences, Beijing 100049, China;3. Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, China |
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| Abstract: | Numerous Ordovician oils worldwide are known to show unusual and distinctive distributions of hydrocarbons which, it has been suggested, are derived from a “unique benthonic mat-forming non-photosynthetic prokaryotic organism”, Gloeocapsomorpha prisca Zalessky 1917, which is the major contributor of organic matter. Organic matter-rich sediments from the Canning and Amadeus Basins of Australia, known to contain G. prisca fossils and to have the characteristic predominance of odd carbon number (C13–C19) n-alkanes, were investigated to determine other hydrocarbon distributions. Sediments from both basins contained abundant n-alkylcyclohexanes with odd carbon number predominance (C13–C19) and methyl-n-alkylcyclohexanes (C14–C20) which, in immature sediments, showed an even carbon number predominance. The isomer distribution of these latter compounds was determined by direct comparison with synthetic standards. The sediments from both basins also contained very similar distributions of steranes and pentacyclic triterpanes and the derived kerogens had a characteristically light carbon isotope signature.Pyrolysis of a G. prisca-rich kerogen yielded a hydrocarbon mixture with a similar composition to the sediment extract, except that there was a marked increase in the relative abundance of pristane, phytane, alkylcyclohexanes, steranes and hopanes relative to n-alkanes. We argue on the basis of the geological, geochemical and palynological data that G. prisca was probably planktonic, photosynthetic and very possibly eukaryotic and that the striking character of Ordovician oils and sediments derive from bacterial and other diagenetic imprints superimposed on the primary signature of this organism. |
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