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Submarine Canyons and Fans Submarine canyons: major conduits of siliciclastic sediment from the continental shelf to the abyssal plain Submarine fans: accumulations of siliciclastic sediment from the shelf break onto the base of the continental slope.

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Presentation Transcript
slide2
Submarine Canyons and Fans
    • Submarine canyons: major conduits
      • of siliciclastic sediment from the continental shelf to the abyssal plain
    • Submarine fans: accumulations of
      • siliciclastic sediment from the shelf break onto the base of the continental slope

http://www.dkimages.com/discover/previews/851/20117924.JPG

submarine canyons basic info
Submarine Canyons (Basic Info)
  • Submarine canyons cut across continental shelves and slopes
  • Carry sediment to the deep ocean basins.
  • Many small submarine canyons and few large ones.
  • Large canyons associated with large coastal rivers.
  • Text from http://www.ocean.uni-bremen.de/EInfo/materialien/elemOc/top12-17/topic13.html

http://www.geol.umd.edu/~jmerck/

submarine canyons basic info1
Submarine Canyons (Basic Info)
  • Submarine canyons formed, in part, by downcutting of coastal rivers during low sea level.
  • Later continued flow of water and sediment might lead to their further development
  • and extension into the deep sea.

Text from http://www.ocean.uni-bremen.de/EInfo/materialien/elemOc/top12-17/topic13.html

submarine fans
Submarine Fans
  • Submarine fans are found at mouths of canyons around the world.

http://faculty.gg.uwyo.edu/heller/Sed%

http://www.indiana.edu/~g105lab/images/gaia_chapter_13/sfs026.gif

submarine fans basic info
Submarine Fans (Basic Info)
  • Submarine fans divided into 3 zones
    • Proximal (upper)
    • Middle
    • Distal (lower)

http://www.geol.umd.edu/~jmerck/geol100/lectures/31.html

slide7
Like alluvial fans fans are fan shaped
  • And “fine” in a proximal to distal direction
submarine fans transport mechanisms
Submarine Fans: Transport Mechanisms
  • Sediment transport, in general can occur in one of 5 modes:
  • Traction
    • 1. Rolling
    • 2. Sliding
    • 3. Bouncing (saltation)
  • 4. Suspension
  • 5. Mass movement
slide9
The whole process is initiated as an underwater landslide.

http://instruct.uwo.ca/earth-sci/200a-001/07turbidity.jpg

slide10
On the proximal fan, the slide has a low water:sediment ratio

Debris flow facies

http://instruct.uwo.ca/earth-sci/200a-001/07turbidity.jpg

slide11
On the distal fan, the flow has a high water:sediment ratio
  • and moves as a density current.

http://instruct.uwo.ca/earth-sci/200a-001/07turbidity.jpg

http://serc.carleton.edu/

slide12
Density Currents
  • Our first quantitative experience with density currents was in
  • 1929 following the M 7.2 Grand Banks Earthquake

Estimated tsunami travel times (in

hours) for waves generated by the 1929

Grand Banks earthquake.

http://www.benfieldhrc.org/activities/hrsr/h&rsr_2005

http://earthquakescanada.nrcan.gc.ca/historic_eq/20th/1929/1929_e.php

grand banks earthquake
Grand Banks Earthquake
  • Density Currents
  • The earthquake triggered an underwater landslide/ density current as evidenced by a series of underwater telephone cable breaks. The last cable, 600 km south, broke 13 hours after the earthquake. Twenty-five years later, south of the earthquake site, a layer of sand was discovered on the sea floor, covering an area the size of the province of Quebec (shown above in light blue). And evidence of vast underwater landslides was found near the epicentre

http://earthnet-geonet.ca/images/communities/earthquakemap.gif

turbidites
Turbidites
  • Turbidites are formed
  • as a result of waning
  • flow.
  • A classic Bouma sequence

http://faculty.gg.uwyo.edu/heller/Sed%20Strat%20Class/SedStrat%208/bouma.jpg

slide15

Upper Carboniferous (Namurian), Ireland. Note bed tabularity.

  • Turbidite sequences can consist of 1000’s of individual beds

http://www.geoclastica.com/images/MisoaFm.jpg

slide16
Turbidites are primarily
  • distinguished on the basis of
  • their graded nature.
turbidites1
Turbidites
  • The character of turbidites (e.g., the thickness and number of Bouma units varies with distance down the fan).

http://csmres.jmu.edu/geollab/fichter/SedRx/subfan.html

knowledge of submarine fans
Knowledge of Submarine Fans
  • Almost all of our knowledge of submarine fans comes from ancient environments and geophysics.

http://strata.geol.sc.edu/images/PosmentierKolla-elementsFan.gif

knowledge of submarine fans1
Knowledge of Submarine Fans
  • Fan environments are 1000’s of meters below
  • ocean, they
  • apparently have features
  • that look very much like
  • those produced by
  • surface processes.

http://strata.geol.sc.edu/images/PosmentierKolla-elementsFan.gif

vertical column
Vertical Column
  • And this is the best vertical section.
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