Deep sea fans occur at the base of continental shelves and are associated with shelf canyons. They are dominated by two facies associations: channel cut-and-fill deposits with well-developed levees in the upper to mid fan and channelized turbidite deposits in the distal fan. Turbidites are density/gravity flows that move sediment down the continental slope via turbidity currents, depositing it in layers described by the Bouma sequence. Dish structures, convoluted bedding, and other sedimentary structures provide evidence of rapid deposition by turbidity currents in deep sea fan environments.

1. Deep Sea Fan Systems

2. Deep-sea Fan Setting
Deep-sea fans occur primarily at the base of continental shelves and
are often associated with shelf canyons.

3. Deep-sea fans are dominated by two facies associations: channel cut-
and-fill deposits with well-developed levees in the upper to mid fan
and channelized turbidite deposits in the distal fan.
Facies Models

6. Shanmugam 2000

7. Feeder Channels

9. Turbidites (density/gravity flows)

10. Bouma Sequence

13. Photo by W. W. Little

15. Photo by W. W. Little
Flute Casts

16. Photo by W. W. Little

17. Photo by W. W. Little
Tool Marks

19. Photo by W. W. Little
Bioturbation

20. Photo by W. W. Little

21. Photo by W. W. Little

22. Dish Strucures
Dish structures are subaqueous water-escape features formed during
rapid deposition of sand.

23. Convoluted Bedding

25. Photo by W. W. Little
Laminated/Massive/Bioturbated Mud

26. Photo by W. W. Little

27. Photo by W. W. Little

28. Chert

31. Delta-front Turbidites
Because of the large quantity of sediment deposited by rivers as they
enter the sea and its stacking to produce a relatively steeply-sided
platform, turbidites are common features associated with deltas.

32. Bouma Sequence Variations

33. Figures 6 & 7: Sandstone Depositional
Environments, Memoir 31 AAPG

34. Figure 4: Idealized facies model. http://www.eu-seased.net/services/issue2/img9.gif

35. Shanmugam 2000

36. Geostrophic (density) Currents

37. Grand Banks Turbidite

38. • Triggered by a magnitude 7.2 earthquake
• Snapped 12 transatlantic telegraph cables
• Lines began snapping at 59 minutes and continued through 797
minutes
• Velocity is estimated to be 20 m/sec
• Flow thickness of several hundred meters
• Minimum volume of175 cubic kilometers
Grand Banks Turbidite