Sediment Gravity
Flow Deposits
Sediment Gravity Flow Deposits
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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
Slumps
1. Bedding remains intact
2. Requires slopes of at least 3°
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
Debris Flows (matrix supported flow)
Debris Flows (Debrites) are matrix supported flows
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:
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t1+t2= (Pt-P) gh sin B
where: Pt-P is the density
difference between the two
fluids
h= the thickness of the
flow
g=acceleration due to
gravity
sin B= bottom slope
Submarine Canyons and Gullies
Turbidites
(Bouma Sequence
Grain Size of Turbidites is characterized by
fining upward successions
Sediment gravity flow transition
refers to the down-slope transition from slump to
debris flow to turbidite as the flow looses shear
strength through shearing an addition of water
Fan Models