Sedimentary Rocks And Fossils

Front 1

Clastic Transport and Fluid Flow

Back 1

1. MASS WASTING
2. FLUID FLOW
3. ENTRAINMENT, TRANSPORT, DEPOSITION OF CLASTS IN FLUID FLOW
4. SEDIMENT GRAVITY FLOWS

Front 2

Types of Transportation

Back 2

1. MASS WASTING
A. Gravity dominates
B. Fluids insignificant
2. FLUID FLOW
A. Clasts not abundant
3. SEDIMENT GRAVITY FLOW
A. Fluid (water or air) significant
B. Gravity significant
C. Clasts very abundant

Front 3

MASS WASTING

Back 3

1. Dry and Freefall
A. Rock falls
- Through air
B. Avalanches
- Along ground
- Grain flow

Front 4

Rockfall from vertical cliff

Back 4

Front 5

Talus cone: Montana

Back 5

Front 6

FLUID FLOW OR HYDRAULICS

Back 6

1. Fluids
A. Gases
B. liquids
2. Change shape
3. Resist change in volume

Front 7

Ability of Fluid to Erode and Transport Sediment

Back 7

1. Density
A. MASS/VOLUME
- Sea Water 1.03 g/cm3
- Water 1g/cm3
- Ice 0.9 g/cm3
2. Viscosity
A. Resistance to flow or shearing
3. Velocity
A. Distance/Time

Front 8

Style of Fluid Flow

Back 8

1. Laminar
2. Turbulent

Front 9

Laminar Flow

Back 9

1. Parallel or subparallel to underlying boundary surface
2. Parallel or subparallel to other molecules in the fluid
3. Can only move down current or down wind
4. Generally ineffective at erosion and transportation
5. Transportation may be effective IF viscosity prevents deposition
6. Present in very slow moving fluids
A. Slow tidal currents
B. Sheet flows
7. Present in very viscous fluids
A. Ice
B. Mud-supported gravity flows
8. Unusual in most stream and eolian environments

Front 10

Turbulent Flow

Back 10

1. Flow is random
2. Flow direction may be up, down, down current, or up current
3. Common in most natural environments
4. Effective in erosion
A. Flow direction upward
5. Effective in transportation
A. flow direction upward

Front 11

Channelized flow

Back 11

Turbulent flow dominates

Front 12

Froude Number: Description

Back 12

1. Ratio Fr = V÷√gD
2. Inertial forces
A. velocity (V)
3. Gravitational forces
A. Gravitational force (g)
B. Depth (D)

Front 13

Froude Number: Meaning

Back 13

1. Fr more than or equal to 1 = rapid flow
2. Fr equal to 1 = threshold
3. Fr less than or equal to 1 = tranquil flow
This controls the bedform – ripples, dunes, laminar bedding, etc.

Front 14

Hydraulic Jump

Back 14

1. Sudden decrease in Froude #
2. Turbulence
3. Common cause is increase in depth

Front 15

Entrainment

Back 15

1. Lift Force (vertical)
2. Drag Force (horizontal)
3. Gravitational Force (no lift or drag)

Front 16

Entrainment Lift Force = Bernoulli’s Principle

Back 16

Front 17

Entrainment

Back 17

Front 18

Erosion, Transportation, and Deposition

Back 18

Front 19

“?” Floculate

Back 19

1. Clay and Silt particles clump together
A. cohesive
B. Edge charges
C. As clumps act of larger grains
D. Require velocity adequate to erode “clump”

Front 20

Transportation in a Stream

Back 20

Front 21

Settling Velocity: Stokes Law

Back 21

1. Depends on
A. Viscosity of fluid (Indirectly proportional)
- Warm water less viscous
- Cool water more viscous
B. Density of grain (directly proportional)
2. Assumes Perfect spheres
A. No velocity

Front 22

Hydraulic Equivalency

Back 22

1. Clasts that settle at SAME velocity
A. Size
B. Shape
C. Angularity
D. Density

Front 23

Sediment Gravity Flows

Back 23

1. Movement principally by gravity, NOT fluid motion
A. Properties of solid flows
B. Properties of fluid flows
- Some fluid (water or air) is required

Front 24

Four Types Sediment Gravity Flows

Back 24

1. Grain Flow
2. Fluidized Flow
3. Debris Flow
4. Turbidity Current

Front 25

Grain Flow

Back 25

1. Cohesionless sediment
2. Air or water
A. No directed pressure
B. Just a buffer between grains

Front 26

Debris Avalanche – Fast, Dry

Back 26

Front 27

City in the path of an avalanche

Back 27

Front 28

Fluidized Sediment Flow: Liquefaction (Quick sand)

Back 28

1. With no pore pressure – solid saturated sand and gravel confined in at least 3 directions
2. Pore water under pressure
A. Weight of overlying sediment
B. Shock waves
- Earthquakes
- Explosions
3. Pore water moves upward = directed pressure
4. Grains supported by pore water
5. Pressure is reduced – becomes solid again

Front 29

Liquefied Sand – New Madrid Earthquakes

Back 29

Front 30

Ground failure due to liquefaction of sand during earthquake

Back 30

Front 31

Debris Flow

Back 31

1. Dense fluid of sediment (clay-gravel) + water
2. Can transport LARGE grains
3. Viscous

Front 32

Diamicton

Back 32

1. Any very poorly sorted deposit without regard to origin
A. Debris flow
B. Till

Front 33

Flow

Back 33

Fluids are important and internal deformation is significant

Front 34

Debris Flow

Back 34

Front 35

Debris Flow and Lahars – Fast, Wet

Back 35

Front 36

Mudflow

Back 36

Front 37

Debris flows

Back 37

1. Poorly sorted
2. Poorly rounded
3. Poor bedding

Front 38

Volcanic Mudflow

Back 38

Front 39

Turbidity Current - subaqueous

Back 39

1. With no pore pressure – solid saturated sediment on slope
2. Pore water under pressure
A. Earthquake Shock waves
3. Pore water moves turbulently
4. Grains (sand and gravel) supported by pore water
5. More dense than surrounding water
6. Flows downslope
7. Alternates with normal marine/lacustrine shales

Front 40

Environments of Deposition

Back 40