Sediment Gravity Flow Deposits

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Sediment Gravity Flow Deposits
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Sediment Gravity Flow Deposits

• Slides and Slumps-mass movement
• Debris flows-matrix supported flows
• Grain flows-grain interaction
• Fluidized flows-fluid escape
• Turbidity currents-density currents with high
  sediment concentrations

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Slumps1. Bedding remains intact2. Requires
slopes of at least 3
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For slumping to occur, the shear strength of the
sediment must be overcome by gravity S(Shear
strength) c o tan ø c
cohesion o effective pressure (N-n) N
normal load n pore water pressure ø
angle of internal friction
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Debris Flows (matrix supported flow)
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Debris Flows (Debrites) are matrix supported
flows
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Before a turbidity current will begin to flow, it
must first overcome both bottom shear stress (t1)
and the shear stress excerpted by the surrounding
fluid (t2). Stated differently, for movement to
occur, the gravitational forces caused by the
density differences of the two fluids operating
on the slope must exceed the combined bottom
shear stress and surfaces shear stress. We can
express this relationship using the following
equation

• t1t2 (Pt-P) gh sin B
• where Pt-P is the density difference between
  the two fluids
• h the thickness of the flow
• gacceleration due to gravity
• sin B bottom slope

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Submarine Canyons and Gullies
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Turbidites (Bouma Sequence
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Grain Size of Turbidites is characterized by
fining upward successions
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Sediment gravity flow transitionrefers to the
down-slope transition from slump to debris flow
to turbidite as the flow looses shear strength
through shearing an addition of water
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Fan Models