Exhumed hydrocarbon-seep authigenic carbonates from Zakynthos island (Greece): Concretions not archaeological remains

Andrews, Julian, Stamatakis, Michael, Marca-Bell, Alina, Stewart, Carlyn and Millar, Ian (2016) Exhumed hydrocarbon-seep authigenic carbonates from Zakynthos island (Greece): Concretions not archaeological remains. Marine and Petroleum Geology, 76. 16–25. ISSN 0264-8172

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Abstract

In Zakynthos Island (Greece), authigenic cementation of marine sediment has formed pipelike, disc and doughnut-shaped concretions. The concretions are mostly composed of authigenic ferroan dolomite accompanied by pyrite. Samples with >80% dolomite, have stable isotope compositions in two groups. The more indurated concretions have δ 18O around +4‰ and δ 13C values between -8 and -29‰ indicating dolomite forming from anaerobic oxidation of thermogenic methane (hydrocarbon seep), in the sulphate-methane transition zone. The outer surfaces of some concretions, and the less-cemented concretions, typically have slightly heavier isotopic compositions and may indicate that concretion growth progressed from the outer margin in the ambient microbially-modified marine pore fluids, inward toward the central conduit where the isotopic compositions were more heavily influenced by the seep fluid. Sr isotope data suggest the concretions are fossil features, possibly of Pliocene age and represent an exhumed hydrocarbon seep plumbing system. Exposure on the modern seabed in the shallow subtidal zone has caused confusion, as concretion morphology resembles archaeological stonework of the Hellenic period.

Item Type: Article
Uncontrolled Keywords: dolomite,concretions,stable isotopes,hydrocarbon-seep,marine archaeology,zakynthos
Faculty \ School: Faculty of Science > School of Environmental Sciences
Depositing User: Pure Connector
Date Deposited: 23 May 2016 10:00
Last Modified: 25 Jun 2020 00:01
URI: https://ueaeprints.uea.ac.uk/id/eprint/58962
DOI: 10.1016/j.marpetgeo.2016.05.022

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