Chapter 6 Flashcards
Sedimentary rocks: transportation of soil
Deposition (ch. 6)
Sediment transported by erosion or mass wasting accumulates in a sedimentary environment. Continental (glacial deposits, streams (alluvial fans), wind (sand dunes), salt lakes), transitional (tidal flats, beaches, spits lagoons, deltas), marine (continental shelf (shallow up to 200 m includes reefs) and continental slope (Deeper greater than 200m includes turbidity))
Diagenesis
Change in rock composition between 150–200 °C. Incudes lithification.
Lithification (ch. 6)
2 main steps, compaction and cementation.
Compaction
Volume of a deposit of sediment decreases as the weight of overlying sediment causes a reduction in pore space as particles pack more closely together.
Cementation
Particles are glued together into rocks.
Gravel
Particles 2-256mm
Sand
Particles 0.062-2mm
Mud
Fine particles 0.004-0.062mm
Detrital/clastic Rocks
Classified via grain size, mineralogy and shape of clasts.
Chemical rocks
Comprised of 2 mechanisms:
Inorganic (evaporation, dripping, chemical processes) and organic (aquatic organisms)
Evaporites
Formed By Evaporation Of Sea or Lake Water. As Concentration Of Salt Increases, crystals precipitate in sequence:
1. Carbonates
2. Sulfates
3. Halite
4. Potassium Salts (sylvite, halite)
Strata
Formed as sediments are deposited flat in water.
Cross bedding
Preserves layers deposited at an angle.
Characteristics of sand dunes, river deltas etc.
Graded bedding
Particle size changes from coarse to fine in upward direction. Often formed by rapid deposition of turbidity current.
Depositional environment: Submarine fans on an ancient shelf margin .
Mud cracks
Flat beds that appear crackled.
