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Clastic Sedimentary Rocks

Clastic Sedimentary Rocks . Derived from the Mechanical Breakup and Redeposition of Older Rocks. Clastic Rocks. Classified by: Grain Size Grain Composition Texture . The Wentworth Scale. Phi ( φ ) = -log 2 (Diameter in mm) Best way to remember: 1mm: φ = 0

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Clastic Sedimentary Rocks

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  1. Clastic Sedimentary Rocks Derived from the Mechanical Breakup and Redeposition of Older Rocks

  2. Clastic Rocks Classified by: • Grain Size • Grain Composition • Texture

  3. The Wentworth Scale • Phi (φ) = -log2(Diameter in mm) • Best way to remember: • 1mm: φ = 0 • φincreases as diameter decreases • Every factor of 2change in diameter = one step in φ

  4. Particle Descriptions

  5. Sediment Sizes and Clastic Rock Types Sedimentary rocks made of silt- and clay-sized particles are collectively called mudrocks, and are the most abundant sedimentary rocks.

  6. Clastic Terms

  7. Super-Size Me • Blair and McPherson, J. Sed. Res., v. 69, no. 1, Jan. 1999, p. 6-19. • Block: 4-65 m (φ = -12 to -16) • Slab: 65-1000 m (1 km) (φ = -16 to -20) • Monolith: 1-33 km (φ = -20 to -25) • Megalith: 33-1000 km (φ = -25 to -30)

  8. Some Special Clastic Rock Types • Arkose Feldspar-Rich • Breccia Angular Fragments • Graywacke Angular, Immature Sandstone

  9. Sandstone Terminology

  10. Maturity • Stability of Minerals • Rock Fragments • Rounding or Angularity • Sorting Removal of Unstable Ingredients - Mechanical Working

  11. Diagenesis

  12. Diagenesis Compaction Cementing • Quartz • Calcite • Iron Oxide • Clay • Glauconite • Feldspar Alteration • Limestone - Dolomite • Plagioclase – Albite Recrystallization • Limestone

  13. Tectonic Settings and Sediment • Cratonic: Mature sandstone • Continental slope: Graywacke, turbidite • Trench: Wildflysch (contorted graywacke) • Post-orogenic basin: Molasse (red sandstone and conglomerate)

  14. Tectonic Settings and Sediment

  15. Lithic Sand, Washington

  16. Lithic Sandsone, Washington

  17. Molasse, Switzerland

  18. Molasse and the High Alps

  19. Conglomerates • Clast Supported vs. Matrix Supported • Polymictic (Outwash, alluvial fans, flood plains) • Oligomictic (Lag deposits) • Diamictic (Tills, Glacio-marine, Submarine Landslides)

  20. Diamictite, Ontario

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