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Deep biosphere in terrestrial systems (DEBITS): The New Zealand coal band [Abstract]

Horsfield, B., Sykes, R., Parkes, Ronald John, Mangelsdorf, K., Kallmeyer, J., Dieckmann, V. and Edbrook, S. 2004. Deep biosphere in terrestrial systems (DEBITS): The New Zealand coal band [Abstract]. Geochimica Et Cosmochimica Acta 68 (11(S1)) , A407. 10.1016/j.gca.2004.05.009

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Bacterial gas is known from isotopic and chemical considerations to occur to thousands of metres depth. How methanogenic bacteria can be active in such deep and ancient formations, where substrates and nutrients should have been long ago removed, is puzzling. However, the thermal maturation of terrigenous organic matter can produce substances which are known to be substrates for methanogens, namely carbon dioxide, acetate and methanol. In addition, aromatisation of organic compounds may produce molecular hydrogen enabling autotrophic reactions to occur, including H2/CO2 methanogenesis and acetogenesis. This temperature activation of buried organic matter could stimulate bacterial activity at depth and at the same time result in reactions and products, previously thought to be abiotic. We have drilled a continuous core (170 metres; 6” diameter) in New Zealand under strictly controlled conditions to sample the deep biosphere in a terrestrial setting. The Cenozoic sedimentary section of the Taranaki Basin (New Zealand) contains potential “feeders” in the form of coals and coaly shales and closely juxtaposed coarse grained sediments, which may act as a habitat for microorganisms. The sediments have experienced significant burial and uplift resulting in a rank range that is consistent with significant generation, expulsion and migration of potential substrates. Additionally, surrounding localities display a wide range of coalification encompassing peats, brown coal and sub-bituminous coal. We are delineating living microbial populations in coarse grained lithologies using “Life Markers” such as the intact phospholipids. Genetic diversity within the microbial ecosystem is being determined using nucleic acid probes. The role of abiotic diagenetic reactions in generating potential substrates is being addressed from the organic geochemistry of macromolecules and the composition and occurrence of low molecular weight functionalised compounds. Changes in the chemical composition of the sediment due to microbial activity is also being examined using laboratory incubation experiments. In this communication we present initial results from the drilling and research programme.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Earth and Ocean Sciences
Subjects: Q Science > QE Geology
Q Science > QR Microbiology
Additional Information: Abstract n. 4.4.33
Publisher: Elsevier
ISSN: 0016-7037
Last Modified: 04 Jun 2017 02:05

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