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Preview of Lab 4. Classification of sediments Reading a ternary diagramFinding Clay : Silt RatioFinding Mud : Sand Ratio. Objectives of Lab 5. Principle axes of sedimentary particlesGrain shapeRoundness SphericityForm. Principle Axes of Sedimentary Particles . Each sedimentary particle has three main axes: L (a): Long axis I (b): Intermediate axis S (c): Short axis .
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1. Sedimentary PetrologyGEO 333 Lab (5)
Grain Morphology (Grain Shape)
2009
3. Objectives of Lab 5 Principle axes of sedimentary particles
Grain shape
Roundness
Sphericity
Form
5. Principle Axes of Sedimentary Particles
8. Grain Shape (2) Grain shape depends on:
1) The original shape of the particle.
Mica particles are usually flat, whereas quartz grains are rounded.
2) The internal structure and hardness.
3) The length of transportation (distance of source area).
The longer a grain is transported, the more round it becomes.
9. Roundness (angularity) A description of the degree of sharpness of the corners and edges of grains.
Gives information about the distance of transport, the energy of transporting mechanisms, and the cycles of erosion and redeposition.
The simplest way to determine the roundness is by visual comparison with standard forms.
The most widely used chart for roundness is Powers chart.
15. Sneed and Folk Sphericity (?P) Also known as maximum projection sphericity (MPS).
The most widely-used expression of sphericity.
17. Riley Sphericity (?R) Riley sphericity relies on measurements that can be taken from the two-dimensional view of a sand grain as seen through a microscope.
19. Corey Shape Factor (S.F.) Very similar to MPS.
Widely used by engineers to describe the overall shape of grains
23. Figure by MIT OCW
25. Sneed and Folk classification of grain form (1958)
26. Illenberger Form Diagram 1991
27. Summary Chart
28. Quiz Find the form, MPS, and CSF for the following grains
Grain 1: L= 56, I= 49.5, S=39 (mm)
Grain 2: L= 46, I= 36, S= 13 (mm)
29. Assignment 5 (1) Determine the roundness and Riley sphericity of the given grain.
30. Assignment 5 (2) Using a caliper, measure the L, I, and S axes of the given grains then complete the above table.
32. The End