G.S.I. Seabed Survey Seminar Possible Carbonate Mound Distribution November 2001 Thomas Furey
Presentation Overview n Introduction. n Overview of carbonate mound distribution to date offshore Ireland. n Mounds and their settings, data examples, data resolution. n Summary and conclusions.
What Are Mounds? n Topographic highs - circular & ridge morphology Of what importance are they? n Environmental – Associated coral ecosystems n Hazards – trawling damage, shallow gas Line 140, Area 3A 30 m 500 m
Interested Groups GEOMOUND – htttp://geomound.ucd.ieGEOMOUND – htttp://geomound.ucd.ie ECOMOUNDECOMOUND ACES - Atlantic Coral Ecosystem StudyACES - Atlantic Coral Ecosystem Study CORSAIRESCORSAIRES ENAM-2ENAM-2 Recent Irish Studies 1996 AIRS survey - Gloria1996 AIRS survey - Gloria Logachev Seismic & SidescanLogachev Seismic & Sidescan Belgica SeismicBelgica Seismic
Mound Identification Trawling, sidescan sonar, seismic.Trawling, sidescan sonar, seismic. Sub bottom profiler.Sub bottom profiler. Multibeam – bathymetry & backscatter.Multibeam – bathymetry & backscatter. Problems incurred: How are they identified? Multibeam Chart Resolution: 1 Pixel = 100 m 2Multibeam Chart Resolution: 1 Pixel = 100 m 2 Contour Interval = 50 m Sub Bottom Profiles: 2D, Digital InterpretationSub Bottom Profiles: 2D, Digital Interpretation
Mound Characteristics Water Depth Ranges: mWater Depth Ranges: m Size:Size: –Height Range: m approximately –Diameter: 250 metres km –Elongate Reefs (?) : Several Km’s
GEOMOUND Carbonate Mounds 24ºW 20 ºW 16 ºW 12 ºW 8 ºW 4 ºW 56 ºN 54ºN 52 ºN 50 ºN 48 ºN 56 ºN 54ºN 52 ºN 50 ºN 48 ºN NWRT SERT MPB SPB
Mound Groups South Porcupine Bite – SPBSouth Porcupine Bite – SPB Main Porcupine Basin – MPBMain Porcupine Basin – MPB South East Rockall Trough – SERTSouth East Rockall Trough – SERT North West Rockall Trough – NWRTNorth West Rockall Trough – NWRT West Rockall Bank – WRBWest Rockall Bank – WRB Edoras Bank - EBEdoras Bank - EB Fangorn Bank - FBFangorn Bank - FB
24ºW 20 ºW 16 ºW 12 ºW 8 ºW 4 ºW 56 ºN 54ºN 52 ºN 50 ºN 48 ºN 56 ºN 54ºN 52 ºN 50 ºN 48 ºN Possible Mound Distribution 2001 EB FB WRB
Bathymetric Mound Distribution Bathymetric Mound Distribution 23º W 18º W 13º W 8º W 57º N 52º N 57º N 52º N 500 m 1000 m 1500 m 2000 m
23º W 18º W 13º W 8º W 57º N 52º N 57º N 52º N PAD Structural Map & Mounds NEXT SLIDE
West Rockall Bank Mounds PINCH MICKS IMAGE – add transects Mounds Ridge 020 km N
West Rockall Bank Mound Example Mound Location 30 metres 500 metres Acoustic Blanking Sub Bottom Profile – Line 144 WSW ENE
Shaded Relief with Bathymetric Contours. WRB Mounds N Line 156 Line 155 Line 154 Line 153 Tracklines Ridge Isolated Mound Contour Parallel Mounds
Raw Backscatter Data - WRB 5 km 50 km WSW ENE
Raw Backscatter Data - WRB n Individual Mounds n Grouped Mounds n Elongate: North-South Contour Parallel Line 154 Line km 10 km
Line 144, Area 3A 500 metres 40 metres Small Mound x 20 metres WRB WRB Mounds 130 metres 1 km Line 155, Area 3A Large Mound metres x 1.5 km
20 metres Line 145, Area 3A 500 metres Acoustic Blanking Acousting Blanking Beneath Possible Gasified Mounds Conical Mound with Moat Feature 500 metres Acoustic Blanking Line 150, Area 3A 40 metres Moat WRB Mounds
Fangorn Bank Bathymetry Map Sheet 28 N Mound features 025 km
Next Slide N 025 km Fangorn Bank Shaded Relief Map Sheet 28
Fangorn Bank Sub bottom record - Line 1353 seabed 40 metres SENW 500 metres
MPB & SPB Mounds 3D Surface North Area 3E 40 km ShadedRelief MBP SPB
Conclusions n Additional Mound locations identified. n Relief useful Mound identification tool. n Raw Backscatter is good quality. n Small features require reprocessing. n West Rockall Bank study proposed. n Ground truthing required. n Large uninterpreted dataset available.
Zone 3 3A W.P. 3E 3F 3H
Area 3E colour contoured map of area covered N Ship track lines Depth Range 200 m to 4500 m 0150 km
Area 3E sun illuminated map of area covered Next slide Gollum Channel Complex 0150 km
Area 3E, Line Possible gas associated with Carbonate Mound. seabed Gas bearing sediment SW NE 500 metres