Clastic Sedimentary Rocks Derived from the Mechanical Breakup and Redeposition of Older Rocks.
-
Upload
derick-gambrill -
Category
Documents
-
view
224 -
download
6
Transcript of Clastic Sedimentary Rocks Derived from the Mechanical Breakup and Redeposition of Older 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) = -log2(Diameter in mm)
• Best way to remember:–1mm: φ = 0–φ increases as diameter decreases– Every factor of 2 change in diameter = one
step in φ
Particle Descriptions
Name Phi Diameter mmBoulder < -8 256 +Cobble -6 to -8 64 - 256Pebble -2 to -6 4 - 64Granule -1 to -2 2 - 4Sand -2 to 4 1/16 - 2Silt 4 - 8 1/256 - 1/16Clay > 8 < 1/256
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.
Rock Type Sediment Grain Size
Shale Clay less than 0.001 mm
Siltstone Silt .001-0.1 mm
Sandstone Sand .01-1 mm
Conglomerate Gravel 1mm +
Clastic Terms
Latin Greek
Gravel Rudite Psephite
Sand Arenite Psammite
Silt Lutite Pelite
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)
Some Special Clastic Rock Types
• Arkose Feldspar-Rich • Breccia Angular Fragments • Graywacke Angular, Immature
Sandstone
Sandstone Terminology
Maturity
• Stability of Minerals • Rock Fragments • Rounding or Angularity • Sorting
Removal of Unstable Ingredients - Mechanical Working
Diagenesis
Diagenesis
CompactionCementing• Quartz • Calcite • Iron Oxide • Clay • Glauconite • Feldspar
Alteration• Limestone - Dolomite • Plagioclase – AlbiteRecrystallization• Limestone
Tectonic Settings and Sediment
• Cratonic: Mature sandstone• Continental slope: Graywacke, turbidite• Trench: Wildflysch (contorted graywacke)• Post-orogenic basin: Molasse (red sandstone
and conglomerate)
Tectonic Settings and Sediment
Lithic Sand, Washington
Lithic Sandsone, Washington
Molasse, Switzerland
Molasse and the High Alps
Conglomerates
• Clast Supported vs. Matrix Supported• Polymictic (Outwash, alluvial fans, flood
plains)• Oligomictic (Lag deposits)• Diamictic (Tills, Glacio-marine, Submarine
Landslides)
Diamictite, Ontario