British Organic Geochemistry Meeting 2012, Leeds University, Oral Presentation


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British Organic Geochemistry Meeting 2012, Leeds University, Oral Presentation

  1. 1. Multidisciplinary Characterization of fluidseepage features in Irish WatersShane O’ ReillyDr. Andre Simpson, Dr. Christopher Allen, Dr. Brian Kelleher
  2. 2. Seabed fluid seepageWhat?Subseabed migration of:• Methane• Higher hydrocarbons• Pore water• GroundwaterImportance?• Global warming• Unique biodiversity• Petroleum & gas prospecting• Marine industrial safety• Formation of dramatic geological featuresBayon, 2009i1mii. Methane-derived authigenic carbonate(MDAC) nodules and moundsi. Pockmarks- Seafloor depressions- Most are dormant/low activityiiSeepage features
  3. 3. Seepage features in Irish WatersRecent discoveries:• Malin Sea pockmarks – 2003(Monteys, 2008, Szpak, 2012)• Dunmanus Bay pockmarks – 2007(CE07_02, CV09_23, CE11_017)• Irish Sea– Lambay Deep mud diapir -1998– Codling Fault MDAC mounds -2001– Irish Sea pockmarks - 2009(Croker, 2005, Judd 2007CV09_26, CV10_28)Malin Sea pockmarksCodling FaultMDAC moundsIrish Sea pockmarksDunmanus Bay pockmarksN40kmLambay Deep mud diapir
  4. 4. Malin Shelf pockmark• Large composite pockmark, 180m water depth• Located in isolated fine grained muddy sediments• Located in region of gas and petroleum resource interest• Seismic data indicates gas pocket at 20mbsf• Geophysics and underwater video indicates currently dormant orlow activity feature• Previous work (Szpak, 2012) lateral migration of gas aroundcrater and decreased activity within
  5. 5. Malin Pockmark Archaeal Diversity-Mixed community present-Known anaerobicmethanotrophic (ANME)groups not dominant- Suggests processes otherthan AOM occuring
  6. 6. Malin Clone Libraries dominated byhydrocarbon-degrading bacteriaPsychrobactersp.Sulfitobactersp.Alcanivoraxborkumensis SK2Uncultured actinobacteriumclone ANTXXIII_706-4_Bac69Pseudoalteromonas sp. P29Uncultured propane-utilizingbacterium (SIP20-4-09)Colwelliasp.Oil contaminated polar & Arabian marine settings(Deppe, 2005, Giudice 2010, Radwan, 2007, 2010)Oil contaminated polar sediments & beach sands(Kostka, 2011 Guibert, 2012)Hydrocarbon-degrader, often dominant in oil spills(Yakimov, 1998)Cold Seep, Weddell Sea, Antarctica (Niemann, 2009)Crude oil contaminated Arctic sediments(Deppe, 2005, Lin, 2009)Hydrocarbon seeps, off Santa Barbara (Redmond, 2010)Deepwater Horizon oil spill (Redmond, 2011, Baelum, 2012)SettingClosest OrganismLibrary40 – 59%18 – 37%0-7%2 – 5%3 – 4%1.5 - 2%0 – 2%
  7. 7. Codling Fault MDAC mounds• 23 mounds along the Codling Fault Zone• 250m long, 80m wide and 5-10m in relief• Dynamic erosional setting• Extensive areas covered by sand wavesXavier Monteys, Geological Survey of Ireland
  8. 8. Codling Fault MDAC mounds25cm 2cmActively seeping mound Pavement stacking Anoxic surface sedimentCarbonate & pyrite encrusted quartz grain Microbial structures Fluid flow pores
  9. 9. Codling Fault MDAC Moundsm/z 205MAGEPLFA16:016:114:0i-15:017:0 18:018:116:016:1ω714:0ai15:015:018:1ω918:218:0Archaeal DGGE15:017:010Me16:0ai-15:0i15:0br16:0• Diagnostic PLFA’s and mono-alkyl glyceryl ethers(MAGE) for AOM-associated sulphate reducingbacteria abundant.(Hinrichs, 2000, Pancost, 2001, Elvert, 2003, Niemann, 2008)• DGGE indicates distinct archaeal community present16:1ω5
  10. 10. Western Irish Sea pockmarks• >15 pockmarks mapped in 40 – 50m water depth• Extensive regional sub-seabed gas signatures evident, not isolated at pockmarks• Water column eco-facies indicate widespread but minor seepage to water column• Video investigation - no MDAC, bacterial mats, seep-associated macrofaunaNew pockmarksXavier Monteys, Geological Survey of Ireland
  11. 11. Acoustic turbidity2009 sampling2011 samplingAcoustic turbidityNDunmanus Bay pockmarks6m vibrocores30m
  12. 12. Dunmanus Bay pockmarksVicinityCraterControlPO43- (μM)NH4+ (mM)H2S(mM)SO42- (mM)Particle Size CH4(μM)• Elevated CH4, H2S, PO43- and NH4+ at and in vicinity of pockmark• Evident lithological control on geochemical processes• Greater activity in vicinity of craters suggests divergence of flow after formationSandSandy MudMudGravel
  13. 13. Conclusions & Future WorkExtensive seepage features within Irish waters.- Malin pockmark: Subsurface gas present but no water columnseepage recorded. Microbial populations indicate hydrocarbons otherthan methane are significant.- Irish Sea mudbelts: Subsurface gas present throughout region,pockmarks currently low activity settings- Codling Fault Mounds: An active seepage setting, distinct microbialcommunities and evidence of anaerobic oxidation of methane.- Dunmanus Bay pockmarks: Active but minor seepage. Lithologicalcontrols on seepage and microbial processes evident.Future workArchaeal lipid biomarkersPyrosequencing (Dunmanus& Codling Fault)Pore water and solid phaseNMR(Dunmanus)
  14. 14. AcknowledgementsXavier Monteys (GSI)Paul Flanagan (QUB)Anna Kulakov (QUB)Michal Szpak (DCU)INFOMARMarine InstituteIRCSETGeological Survey of Ireland