Submarine canyons and fans submarine canyons major conduits
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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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Submarine Canyons and Fans Submarine canyons: major conduits

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Submarine canyons and fans submarine canyons major conduits

  • 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


Submarine canyons and fans submarine canyons major conduits

  • 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


Submarine canyons and fans submarine canyons major conduits

  • The whole process is initiated as an underwater landslide.

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


Submarine canyons and fans submarine canyons major conduits

  • 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


Submarine canyons and fans submarine canyons major conduits

  • 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/


Submarine canyons and fans submarine canyons major conduits

  • 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


Submarine canyons and fans submarine canyons major conduits

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

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

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


Submarine canyons and fans submarine canyons major conduits

  • 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


Submarine canyons and fans submarine canyons major conduits

  • This is the best (and simplest) model we have of a submarine fan depositional facies


Vertical column

Vertical Column

  • And this is the best vertical section.


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