Deep Sea Fan Systems

Deep-sea Fan Setting

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

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

Shanmugam 2000

Feeder Channels

Turbidites (density/gravity flows)

Bouma Sequence

Photo by W. W. Little

Photo by W. W. Little

Flute Casts

Photo by W. W. Little

Photo by W. W. Little

Tool Marks

Photo by W. W. Little

Bioturbation

Photo by W. W. Little

Photo by W. W. Little

Dish Strucures

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

Convoluted Bedding

Photo by W. W. Little

Laminated/Massive/Bioturbated Mud

Photo by W. W. Little

Photo by W. W. Little

Chert

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.

Bouma Sequence Variations

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

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

Shanmugam 2000

Geostrophic (density) Currents

Grand Banks Turbidite

• 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