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G.S.I. Seabed Survey G.S.I. Seabed Survey SeminarSeminar
Possible Carbonate Mound Possible Carbonate Mound DistributionDistribution
November 2001November 2001Thomas FureyThomas Furey
Presentation OverviewPresentation Overview
Introduction.Introduction. Overview of carbonate mound Overview of carbonate mound
distribution to date offshore distribution to date offshore Ireland.Ireland.
Mounds and their settings, data Mounds and their settings, data examples, data resolution.examples, data resolution.
Summary and conclusions.Summary and conclusions.
What Are Mounds?What Are Mounds? Topographic highs - circular & ridge morphologyTopographic highs - circular & ridge morphology
Of what importance are Of what importance are they?they?
Environmental – Associated coral Environmental – Associated coral ecosystemsecosystems
Hazards – trawling damage, shallow gasHazards – trawling damage, shallow gas
Line 140, Area 3A
30 m
500 m
Interested GroupsInterested 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 StudiesRecent Irish Studies•1996 AIRS survey - Gloria1996 AIRS survey - Gloria•Logachev 1997 - Seismic & Logachev 1997 - Seismic &
SidescanSidescan•Belgica 1997 - SeismicBelgica 1997 - Seismic
Mound Identification Mound Identification
•Trawling, sidescan sonar, seismic.Trawling, sidescan sonar, seismic.•Sub bottom profiler.Sub bottom profiler.•Multibeam – bathymetry & backscatter.Multibeam – bathymetry & backscatter.
Problems incurred:Problems incurred:
How are they How are they identified?identified?
•Multibeam Chart Resolution:Multibeam Chart Resolution:1 Pixel = 100 m1 Pixel = 100 m22
Contour Interval = 50 mContour Interval = 50 m
•Sub Bottom Profiles: 2D, Digital Sub Bottom Profiles: 2D, Digital InterpretationInterpretation
Mound CharacteristicsMound Characteristics
• Water Depth Ranges: 550-2500 mWater Depth Ranges: 550-2500 m• Size:Size:
– Height Range: 20 - 400 m Height Range: 20 - 400 m approximatelyapproximately
– Diameter: 250 metres - 1.5 kmDiameter: 250 metres - 1.5 km– Elongate Reefs (?) : Several Km’s Elongate Reefs (?) : Several Km’s
GEOMOUND Carbonate GEOMOUND Carbonate MoundsMounds
24ºW 20 ºW 16 ºW 12 ºW 8 ºW 4 ºW
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 GroupsMound Groups•South Porcupine Bite – SPBSouth Porcupine Bite – SPB•Main Porcupine Basin – MPBMain Porcupine Basin – MPB•South East Rockall Trough – South East Rockall Trough – SERTSERT•North West Rockall Trough – North West Rockall Trough – NWRTNWRT•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
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 Possible Mound Distribution 20012001
EB
FB
WRB
Bathymetric Mound Bathymetric Mound DistributionDistribution
23º W 18º W 13º W 8º W
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
23º W 18º W 13º W 8º W
57º N
52º N
57º N
52º N
PAD Structural Map & PAD Structural Map & MoundsMounds
NEXT SLIDE
West Rockall Bank MoundsWest Rockall Bank Mounds
PINCH MICKS IMAGE – add transects
Mounds
Ridge
0 20 km
N
West Rockall BankWest Rockall Bank Mound Example 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 153 - 156
• Ridge
• Isolated Mound• Contour Parallel Mounds
Raw Backscatter Data - Raw Backscatter Data - WRBWRB
5 km
50 km
WSW ENE
Raw Backscatter Data - Raw Backscatter Data - WRBWRB
Individual Individual MoundsMounds
Grouped MoundsGrouped Mounds Elongate:Elongate:
North-SouthNorth-SouthContour ParallelContour Parallel
Line 154
Line 153
5 km
10 km
Line 144, Area 3A 500 metres
40 metres
Small Mound - 250 x 20 metresSmall Mound - 250 x 20 metres
155
144
WRB
WRB WRB MoundsMounds
130 metres1 km
Line 155, Area 3A
Large Mound - 130 metres x 1.5 kmLarge Mound - 130 metres x 1.5 km
20 metres
Line 145, Area 3A500 metres
Acoustic Blanking
Acousting Blanking BeneathAcousting Blanking Beneath
Possible Gasified Mounds Possible Gasified Mounds
Conical Mound with Moat FeatureConical Mound with Moat Feature
500 metres AcousticBlanking
Line 150, Area 3A
40 metres
Moat
WRB WRB MoundsMounds
150 145
Fangorn BankFangorn Bank Bathymetry Map Sheet 28 Bathymetry Map Sheet 28
N
Mound features
0 25 km
Next Slide
N
0 25 km
Fangorn BankFangorn BankShaded Relief Map Sheet 28Shaded Relief Map Sheet 28
Fangorn BankFangorn Bank Sub bottom record - Line 1353Sub bottom record - Line 1353
seabed
40 metres
SE NW
500 metres
MPB & SPB MPB & SPB MoundsMounds
3D Surface 3D Surface
NorthNorth Area 3EArea 3E
40 km
Shaded Shaded
ReliefRelief
MBP
SPB
ConclusionsConclusions Additional Mound locations Additional Mound locations identified.identified. Relief useful Mound identification Relief useful Mound identification tool.tool. Raw Backscatter is good quality.Raw Backscatter is good quality. Small features require reprocessing. Small features require reprocessing. West Rockall Bank study proposed.West Rockall Bank study proposed. Ground truthing required.Ground truthing required. Large uninterpreted dataset Large uninterpreted dataset available.available.
Zone 3Zone 3
3A
W.P.
3E
3F
3H
Area 3E colour contoured map of area coveredArea 3E colour contoured map of area covered
N
Ship track lines
Depth Range200 m to 4500 m
0 150 km
Area 3E sun illuminated map of area coveredArea 3E sun illuminated map of area covered
Next slide
Gollum Channel Complex
0 150 km
Area 3E, Line 3564.Area 3E, Line 3564.Possible gas associated with Carbonate Mound.Possible gas associated with Carbonate Mound.
seabed
Gas bearing sediment
SW NE
500 metres
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