O'Reilly, SS, Hryniewicz, K, Little, CTS et al. (6 more authors) (2014) Shallow water methane-derived authigenic carbonate mounds at the Codling Fault Zone, western Irish Sea. Marine Geology, 357. 139 - 150. ISSN 0025-3227
Abstract
Methane-derived authigenic carbonate (MDAC) mound features at the Codling Fault Zone (CFZ), located in shallow waters (50–120 m) of the western Irish Sea were investigated and provide a comparison to deep sea MDAC settings. Carbonates consisted of aragonite as the major mineral phase, with δ13C depletion to −50‰ and δ18O enrichment to ~ 2‰. These isotope signatures, together with the co-precipitation of framboidal pyrite confirm that anaerobic oxidation of methane (AOM) is an important process mediating methane release to thewater column and the atmosphere in this region. 18O-enrichment could be a result ofMDAC precipitation with seawater in colder than present day conditions, or precipitation with 18O-enriched water transported from deep petroleum sources. The 13C depletion of bulk carbonate and sampled gas(−70‰) suggests a biogenic source, but significant mixing of thermogenic gas and depletion of the original isotope signature cannot be ruled out. Active seepage was recorded from one mound and together with extensive areas of reduced sediment, confirms that seepage is ongoing. The mounds appear to be composed of stacked pavements that are largely covered by sand and extensively eroded. The CFZ mounds are colonized by abundant Sabellaria polychaetes and possible Nemertesia hydroids, which benefit indirectly from available hard substrate. In contrast to deep sea MDAC settings where seep-related macrofauna are commonly reported, seep-specialist fauna appear to be lacking at the CFZ. In addition, unlike MDAC in deep waters where organic carbon input from photosynthesis is limited, lipid biomarkers and isotope signatures related to marine planktonic production (e.g. sterols, alkanols) were most abundant. Evidence for microbes involved in AOM was limited from samples taken; possibly due to this dilution effect from organic matter derived from the photic zone, and will require further investigation.
Metadata
Item Type: | Article |
---|---|
Authors/Creators: |
|
Copyright, Publisher and Additional Information: | © 2014 Elsevier B.V. NOTICE: this is the author’s version of a work that was accepted for publication in Marine Geology. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Marine Geology, 357, (2014) DOI 10.1016/j.margeo.2014.08.007 Uploaded in accordance with the publisher's self-archiving policy |
Keywords: | Methane-derived authigenic carbonate; gas seepage; Codling Fault; Irish Sea |
Dates: |
|
Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 12 Jan 2015 16:41 |
Last Modified: | 20 Apr 2015 23:07 |
Published Version: | http://dx.doi.org/10.1016/j.margeo.2014.08.007 |
Status: | Published |
Publisher: | Elsevier |
Identification Number: | 10.1016/j.margeo.2014.08.007 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:82704 |