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Pyritic and baritic burrows and microbial filaments in postglacial lacustrine clays in the northern Baltic Sea
Stockholm University, Faculty of Science, Department of Geological Sciences. (Marine Geology)
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2010 (English)In: Journal of the Geological Society, ISSN 0016-7649, E-ISSN 2041-479X, Vol. 167, no 6, 1185-1198 p.Article in journal (Refereed) Published
Abstract [en]

Holocene postglacial lacustrine clays in the northern Baltic Sea were studied for ichnofossils,petrography, and microscale elemental and 34S/32S composition to understand the impact of benthos-producedorganic matrices on the early diagenesis of sediments. X-radiographs of these clays display intense burrowmottling with discrete Palaeophycus, ‘Mycellia’ and rare Arenicolites. Small burrow-like and irregularlyshaped concretions were separated from these clays. The burrow-like concretions are composed of framboidalpyrite and poorly crystalline FeS2 cement. They formed within worm-produced burrows by the decompositionof mucous coatings on the burrow walls by sulphate reduction. 34SCDT composition of the framboidsindicates saline inflows from the North Sea as the sulphate source. The irregular concretions are microcrystallinepyritic masses that formed in pore spaces with less reactive organic compounds. Their 34SCDT valuesreflect precipitation from the ambient porewater sulphate by sulphate reduction. The burrow-like and irregularconcretions are microcrystalline barite in the lower parts of the clays. ‘Mycellia’ are mineral-replacedfilaments produced by large sulphur-oxidizing bacteria or mycelial fungi. They concentrate in monosulphidebands in the lower substrate levels, but are associated with organic patches upward. This study demonstratesthat substantial amounts of pyrite formed within organic matrices close to the sediment–water interface. Thisdiffers from previous studies that proposed a deeper-burial origin and allochthonous sulphur source.

Place, publisher, year, edition, pages
2010. Vol. 167, no 6, 1185-1198 p.
Keyword [en]
Trace fossils
National Category
Earth and Related Environmental Sciences
Research subject
URN: urn:nbn:se:su:diva-47341DOI: 10.1144/0016-76492010-017ISI: 000283124300009OAI: diva2:373690
Available from: 2010-12-07 Created: 2010-12-01 Last updated: 2011-11-23Bibliographically approved

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Löwemark, Ludvig
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