Lesson 2: Grain Size Flashcards
Logarithmic scale for sediment size
Kumbrein Phi Scale
Grade scale for expressing particle size that extends from 1/256 mm to >256mm
Udden-Wentworth Scale
Size of boulder in Phi (f)
-12.0 - -8.0
Size of cobble in Phi (f)
-8.0 - -6.0
Size of pebble in Phi (f)
-6.0 - -2.0
Size of granule in Phi (f)
-2.0 - -1.0
Size of very coarse sand in Phi (f)
-1.0 - 0.0
Size of coarse sand in Phi (f)
0.0 - 1.0
Size of medium sand in Phi (f)
1.0 - 2.0
Size of fine sand in Phi (f)
2.0 - 3.0
Size of very fine sand in Phi (f)
3.0 - 4.0
Size of coarse silt in Phi (f)
4.0 - 5.0
Size of medium silt in Phi (f)
5.0 - 6.0
Size of fine silt in Phi (f)
6.0 - 7.0
Size of very fine silt in Phi (f)
7.0 - 8.0
Size of clay in Phi (f)
8.0 - 14.0
What type of method of analysis is used for unconsolidated boulders, cobbles, and pebbles?
manual measurement of individual clasts
What type of method of analysis is used for unconsolidated granules and sand?
sieving, settling tube analysis, and image analysis
What type of method of analysis is used for unconsolidated silt and clay?
Pipette analysis, sedimentation balances, sedigraph, laser diffractometry, and electro-resistance size analysis
What type of method of analysis is used for lithified boulders, cobbles, and pebbles?
manual measurement of individual clasts
What type of method of analysis is used for lithified granules and sand?
Thin section measurement and image analysis
What type of method of analysis is used for lithified silt and clay?
Electron microscopy
Size of very well sorted in Phi
<0.35
Size of well sorted in Phi
0.35 - 0.50
Size of moderately well sorted in Phi
0.50 - 0.70
Size of moderately sorted in Phi
0.70 - 1.00
Size of very poorly sorted in Phi
2.00 - 4.00
Size of extremely poorly sorted in Phi
> 4.00
Grains cut marginally in a thin section have smaller diameters than sieve data. The data is commonly corrected to agree more closely to sieve data.
Corpuscle Effect
Analyze and measure grain particles in a thin section
Image Analysis
Sediments are slowly poured into an electrolyte solution, where sediments will pass through, where changes in the electrical field will produce pulses, translating into the grain size
Electro-resistance size analyzer
Particles that are settling will pass through a diffracted light, and the angle of the diffracted light increases with decreasing particle size. A detector senses the angular distribution of scattered light energy.
Laser Diffraction size analyzer
Petrographic microscope fitted with an ocular micrometer, difficulty with this is some randomly oriented sediments may be oriented in the short axis
Thin-section measurement
An automated version of thin-section measurement is through _________.
Image processing
Interpreting sediment source with these considerations:
• The source of the particles that makes the rocks
• The erosion and transportation mechanisms
• The depositional setting and processes
• Physical and chemical conditions of the burial environment
Provenance Studies
Post lithification and diagenesis, sedimentary rocks are used for fingerprinting paleoenvironments
Environmental Studies
