Submarine canyons cut across continental shelves and slopes, carrying sediment from rivers and coastal areas to deep ocean basins. Submarine fans form at the mouths of canyons, accumulating sediment across the continental slope in a fan-shaped pattern. Sediment transport within submarine fans occurs through various mechanisms like debris flows, density currents, and turbidity currents, resulting in deposition of turbidite sequences that can be studied to understand ancient submarine fan environments.

2. • 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

3. 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/

4. 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.ht

5. Submarine Fans
• Submarine fans are
found at mouths of
canyons around the
world.
http://www.indiana.edu/~g105lab/images/gaia_chapter_13/sfs026.gif
http://faculty.gg.uwyo.edu/heller/Sed%

6. 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

7. • Like alluvial fans fans
are fan shaped
• And “fine” in a
proximal to distal
direction

8. 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

9. • The whole process is
initiated as an
underwater landslide.
http://instruct.uwo.ca/earth-sci/200a-001/07turbidity.jpg

10. • 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

11. • On the distal fan, the
flow has a high
water:sediment ratio
• and moves as a
density current.
http://serc.carleton.edu/
http://instruct.uwo.ca/earth-sci/200a-001/07turbidity.jpg

12. • Density Currents
• Our first quantitative
experience with density
currents was in
• 1929 following the M 7.2
Grand Banks Earthquake
http://earthquakescanada.nrcan.gc.ca/historic_eq/20th/1929/1929_e.php http://www.benfieldhrc.org/activities/hrsr/h&rsr_2005
Estimated tsunami travel times (in
hours) for waves generated by the 1929
Grand Banks earthquake.

13. 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

14. 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

15. • Turbidite sequences
can consist of 1000’s
of individual beds
Upper Carboniferous (Namurian), Ireland. Note bed tabularity.
http://www.geoclastica.com/images/MisoaFm.jpg

16. • Turbidites are
primarily
• distinguished on the
basis of
• their graded nature.

17. 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

18. 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

19. 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

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

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