Whiticar, Michael J. (2002) Diagenetic relationships of methanogenesis, nutrients, acoustic turbidity, pockmarks and freshwater seepages in Eckernförde Bay. Marine Geology, 182 (1-2). pp. 29-53. DOI 10.1016/S0025-3227(01)00227-4.

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Abstract

High organic loading (4-5 wt%) and sedimentation rates (1.4 mm yr(-1)) in Eckernforde Bay sediments lead to anaerobic conditions within the uppermost 15 cm. Intense bacteria] sulphate reduction (0.011-0.15 mM SO4red2- yr(-1)) exhausts dissolved sulphate around 150 cm sediment depth, resulting in methanogenesis at greater sediment depth by carbonate reduction (1.8-8.5 muM CH4 yr(-1)). Extensive regions of Eckernforde Bay are characterized by acoustically turbid sediments (> 300 cm sediment depth), resulting from deeper sediments supersaturated in methane, forming free gas accumulation zones. Methane migrating upward into the sulphate reduction zone is effectively consumed by sulphate reducing bacteria at rates 3-10 times greater than methanogenesis, i.e. 46-95 muM CH4 (ox) yr(-1). The pathways of methane formation and anaerobic oxidation are confirmed by stable carbon and hydrogen isotope evidence. Pockmarks, i.e. shallow surface depressions in some Eckernforde Bay sediments, are not associated with gas ebullition; rather, these physical features result from the expulsion of freshwater. These episodic springs or seepages of groundwater from the underlying, Holocene glacial lags and sands into the basin at pockmark sites have characteristic low chloride and methane concentrations. The geochemical evidence indicates that the commercial accumulation of petroleum in the lower Cretaceous, Dogger-Beta-Hauptsandstein Schwedeneck field in Eckernforde Bay (1500 mbsf) has no surface manifestation and does not influence either the occurrence of acoustic turbidity or pockmarks

Document Type:	Article
Refereed:	Yes
Open Access Journal?:	No
Publisher:	Elsevier
Projects:	Boknis Eck
Date Deposited:	17 Jul 2013 11:15
Last Modified:	17 Jul 2013 11:15
URI:	https://oceanrep.geomar.de/id/eprint/21594

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