beach to canyon head sedimentary processes...2012/06/22 · beach to canyon head sedimentary...
TRANSCRIPT
2012-12-06
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Beach to Canyon Head Sedimentary Processes
João Duarte, Rui Taborda & Equipa Beach to Canyon
Beach to Canyon Head Sedimentary Processes
Portuguese Science Foundation (FCT)
PTDC/MAR/114674/2009
• Scientific Background
• Project Objectives
• Management and Tasks
• Activities
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World submarine canyons
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• Total mapped: 5849; based on ETOPO bathymetry (Harris & Whiteway, 2011)
Monterey Canyon - GeoMapApp
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Long submarine valleys with a prominent
shape: abrupt walls and exceptional depth
120km
Submarine canyons with coastal signature
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Initial erosional sector and terminal
agradational channel and fan
Submarine canyons with coastal signature
Monterey Canyon - GeoMapApp
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Marked unique axial incision and linked to
a coastline orientation anomaly
Submarine canyons with coastal signature
Monterey Canyon - GeoMapApp
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Canhões submarinos: Canhão de Monterey
Congo (Zaire) canyon
CoMargE - IFREMER
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Congo (Zaire) canyon
800 km Babonneau. N., et al, 2002
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Capbreton canyon
IFREMER 2007
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Capbreton canyon
Gaudin, M., et al, 2006
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Capbreton canyon head
Gaudin, M., et al, 2006
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Monterey canyon head
Smith Douglas P., et al, 2007
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500 m
La Jolla canyon head
Ross Overstreet 2005
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Submarine canyons with coastal signature
Sediment conduits
• Sometimes linked with rivers but mostly they’re not
• Major sediment transport system
• Large coarse sediment catastrophic events (sand, gravel, pebles and blocs
• Examples:
• Congo canyon: 60 submarine cable cuts in 100 years (Khripounouff, A., et al, 2003)
• Var Canyon: landfill colapse on canyon head originated a tsunamy, bulldozer transported to 1400 m depth, 2 cable cuts more than 100 km and 2600 m depth (Mulder, et al, 2000)
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Nazare Canyon
5 Km
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Nazare Canyon Head
Nazaré
Peniche
Pedrógão
Figueira da Foz
9 30'0"W
9 30'0"W
9 0'0"W
9 0'0"W
39 30'0"N 39 30'0"N
40 0'0"N 40 0'0"N
0 10 20 30 40 5 km
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2 km
Canyon heads & B2C Project
• The erosional power seems to be mostly injected on the canyon head
• Coarse sediment and axial incision are linked
• Precursors:
• Project SECNA - Instituto Hidrográfico 1999/2000
• EUROSTRATAFORM, HERMES, MONICAN & SIMOC PROJECTS
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Issues to address
• Coastal sink of unknown magnitude (sediment budget);
• Nature and scale of the canyon-head processes influence on the coastline evolution
• Can we identify a positive retroactive process of nearshore incision and sand injection processes?
• Distal contribution (terminal fan sedimentation)
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Objectives
• Understand the sedimentary injection/capture process into the canyon head
• Recognize the most important forcing mechanisms
• Identify sediment paths, geomorphological constrains and morphodynamics
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Task Structure
Previous results (2000)
Kongsberg EM950 survey
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Resultados Imagem de Sondador Multifeixe
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Resultados
• Ampliação da cabeceira
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Previous results (2000)
0 10.5 Kilometers
±Legend
Slope (degrees)
0 - 3
3 - 8
8 - 15
15 - 20
20 - 25
25 - 35
35 - 45
45. - 55
55 -
High resolution slope chart
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Longshore Drift
Inner shelf transport
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Sediment supply
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Agitação predominante
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System dynamics
Longshore Drift
Longshore drift jet produced on Norte beach projected from Nazare cape (08.06.2012)
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Canyons 2003 – RV Pelagia
Medium sized sands at 800 m depth on the Nazare canyon axis
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Monterey canyon head
Smith, Douglas P., et al, 2007
500 m
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B2C task status
• Multibeam survey of the canyon head using a EM3002 Kongsberg system combined with a EM710 (NRP Almirante Gago Coutinho)
• EM710 multibeam survey of Tributário de Vitória head
• Vibrocores samples of the direct sink sand spots inside the canyon head (aprox. 100 m)
• Beach topography and sediment sampling
• Video monitoring of Norte beach, wave swelling area and Baía da Nazaré beach
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Canyon Multibeam DTM 2
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Vibrocore samples
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Video monitoring 2
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• Sítio da Nazaré
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• Sítio da Nazaré
Video monitoring
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• Norte beach and wave swelling area
Video monitoring