Deep Sea Environments
Deep Sea Fan Depositional Systems

Deep Sea Fans form in the moderate to deep ocean, down-dip of submarine canyons and, often, deltas.

They have large sediment flux, high sedimentation rate and, usually, large areas.

Gravity is the dominant flow transport and deposition mechanism.

  • turbidity currents (forming turbidites).
  • subaqueous debris flows.
  • suspension fall-out.

Lobes and lobe-switching are important.

Both coarse and fine grained sediment are present.

Sand-bodies are often well-sorted and normally graded.

Characteristics of Deepwater Systems

Sediments fine upward from marine fans.

Sand bodies form lobes perpendicular to basin margin.

Formed by a mix of fluvial input, and turbidite currents.

Facies: Sub-divided erosion surfaces formed during:

  • Migrating fan lobe fill.
  • Dropping in base level (local channels).
  • Rising in base level.

Poor to well-sorted litharenites are common.

Sedimentary structures:

  • Fining-upward cycles that coarsen up as the depocenter of lobes migrate.
  • Up-dip channel cut and fill.
  • Gently seaward dipping thin parallel lobate sheets.

Geometries:

  • Confined incised channels.
  • Open lobate sheets perpendicular and occasionally parallel to shore.

Fauna & flora Restricted Marine fauna, often in over-bank shales


Schematic Deep Sea Fan Morphology  

 

Processes and Deposits

 

 

Outcrop Photos