Strong heat flow variability in an active shallow gas environment, Dnepr palaeo-delta, Black Sea |
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| Authors: | J Poort R I Kutas J Klerkx S E Beaubien S Lombardi L Dimitrov A Vassilev L Naudts |
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| Institution: | (1) Renard Centre of Marine Geology (RCMG), Universiteit Gent, Krijgslaan 281 s8, 9000 Gent, Belgium;(2) Institute of Geophysics, National Academy of Science of Ukraine, 32 Palladin Ave., 03680, Kiev, 142, Ukraine;(3) International Bureau for Environmental Studies (IBES), Audrey Hepburnstraat 9/13, 1090 Brussels, Belgium;(4) Dipartimento di Scienze della Terra, Università di Roma “La Sapienza”, Piazzale Aldo Moro 5, 00185 Roma, Italy;(5) Institute of Oceanology (IOS), Bulgarian Academy of Sciences, P.O. Box 152, Varna, 9000, Bulgaria |
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| Abstract: | The Dnepr palaeo-delta on the north-western continental slope of the Black Sea is a prolific seepage zone characterised by
a highly variable heat flow ranging from 24 to 88 mW/m2. New thermal data were collected at 33 closely spaced stations in order to better understand the apparent relation between
heat flow variability and seepage features. Strong relief gradients and associated landslide shaping may explain first-order
heat flow variability but, locally, thermal parameters appear to be controlled by fluid and gas migrations. High heat flow
anomalies are found at sites where faults and diapirs offer pathways for warm fluid flow from deeper sedimentary levels. Low
heat flow is most strongly expressed at ridge crests near seepage sites but is also found where seeps are absent. Reduced
heat flow and nonlinear temperature-depth variations are interpreted to result from natural or induced gas ebullition of saturated
shallow gas covered by a thin, relatively impermeable sedimentary seal. The presence of sealed gas pockets, in particular
at ridge crests, is supported by methane pore-water analysis and a shallow gas front widely observed in the study area. |
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