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Weathering (Def & types)
Process which breaks down rock at the earth's surface
Produces discrete sed. particles and dissolved solutes
Biological
Chemical
Physical
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Regolith
Physically disintegrated rock debris
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Soils
Complex material w/ physical, chemical, and biological products of disintegration from bedrock and plants
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Why study soils
origins of sed. materials
preservation of ancient soils (Paleosols) in rock record
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Forms of chemical weathering
Simple solutions
Hydration/Dehydration
Hydrolysis
Oxidation/Reduction
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Major classes of sediments (4)
Clastic
Carbonates
Other biogenic (chert, coal)
Other chemical (evaporites)
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Provenance
Placeand geological setting of a sediment's origin
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Reynold's number (  )
Inertial Forces/Viscous Forces
Laminar or turbulent
High number: more turbulent
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Froude number ( )
Describes how surface waves will pass through a fluid
Inertial Forces/Gravitational Forces
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Flow is shooting or supercritical
Plane beds
Antidunes
Chutes and pools (erosion)
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Flow is tranquil or subcritical
Plane beds
Ripples
Sand waves
Dunes (megaripples)
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Competence
Max. particle size a given flow can move
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Hydrodynamic Lift
Saltation
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Ways to move particles (3)
Traction (rolling and sliding)
Saltation
Suspension (viscosity)
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Bedforms
Mounds or troughs of loose sed on a mobile bed that form at the sed/fluid interface, produced by the flow acting on them
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Density Flows
Fluid moves b/c it is denser than surrounding fluid
Causes: temp, salinity, composition (rivers entering lakes), turbidity (suspended sediment)
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Causes of Turbidity Flows
Seasonal floods, storms, tsunamis, local earthquakes, landslides, oversteepened slopes
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Physical characteristics of Turbidity flows
Low viscosity, turbulent flows, high with no internal strength
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Turbidity Flow Head
Turbulent and erosive
Potentially very high velocities and runouts
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Turbidity Flow Body
Carries traction load at base
Transmits gravitational shear waves "upstream"
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Turbidity Flow Tail
Lower velocity and suspended sediment concentration
Passage often much delayed (days to months)
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Bouma Sequence (6, bottom to top)
Erosional surface
Graded gravel and sand
Planar bedded sands
Ripple bedded sands/silts
Planar bedded sands and silts
Mud drape from tail suspension
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Angle of repose
Angle at which materials naturally pile (27-34 degrees for sand)
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Sed Fabric
Internal organization of sed particles
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Permeability
Ease with which a fluid is transmitted through a rock
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Imbrication
Conglomerate pebbles dip away from direction of current
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Graded Bedding
Sed particles are finer at the top than at the base
Indicates declining flow
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Sed Structures associated with bedform migration
Planar and Trough cross bedding
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Sed Structures associated with episodic flow
Flaser bedding
Lenticular bedding
(ex. Lake deposits)
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Sturctures associated with unidirectional flow on slopes
Tool marks
Flute casts
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Bedforms associated with bidirectional flow
Oscillatory ripples
Herringbone cross strat
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Structures formed by fluid escape
Flame structures
Sedimentary dikes
Dish structures
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Structures formed during desiccation
Mudcracks
Raindrop imprints
Salt casts
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Biogenic Structures
Trace Fossils
Burrows, trails, borings, footprints, etc
Stromatolites
Bioturbation
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Unroofing in Alluvial Deposits
Progressive uplift of footwall
Puts older sediments on top of younger ones
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Sinuosity index
S= (Deepest part of channel)/(Length of Valley)
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Anastamosed River
Multiple stable channels
Prominent levees, extensive wetlands, vegetated islands
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Channel Migration causes...
Epsilon cross bedding
Lateral Accretion Surfaces
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Crevasse Splay Deposits
Broken levees
Rapid loss of flow competence - Climbing ripples
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Lake drainage types
External: has outlet
Internal: no outlet
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Walther's Law
Sediments usually deposited next to each other may be vertical to eachother when depositional environment changes
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