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What happens during sediment transport?
Grain shape changes:rounding
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What is the most obvious feature of sedimentary rocks?
layering or stratification is the most obvious feature
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What can sediment be transported by?
Water, wind, and ice
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How much of detrital sediment is deposited into the world's oceans annualy?
10 billion tons
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When sediment is transported the grains become what?
Rounded
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How are the grains at the transport site?
Angular
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What is sorting?
Grains separated by size, shape,or density
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When transported by wind how are the sediment grains sorted?
The grains are well sorted sand- least viscous means thinner
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When transported by water how are grains sorted?
transports gravel- intermediate viscosity
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When transported by ice how are the grains sorted?
Typically poorly sorted- high viscosity means thicker
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Grain size is also related to ENERGY. More energy=
Bigger grains
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More viscosity of an agent means
less sorting
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What can you tell about sediment transportation from
grain shape?
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What can you tell about sediment transportation from
grain sorting?
Sorting = agent doing the transporting
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What can you tell about sediment transportation from
grain size?
Size = energy
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Agents of sediment transportation
- Water, wind, ice
- ! ! ALL are driven by GRAVITY
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Where do sediments end up?
Depositional environments
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How do sediments become rocks (lithification)?
- Compaction
- Cementation
- Recrystallization
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What is compaction?
Reduces the volume of sediment
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What is Cementation?
Precipitation of cement
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What is recyrstalization?
- growth of minerals under higher temperature and pressure
- *no new minerals are formed*
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What are the sediment types?
- Clastic sediment
- Chemical sediment
- Biochemical sediment
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What is clastic sediment?
-made of chunks of other rocks
- Name based on grain size (clay, silt, sand, pebble)
- Pebbles: Conglomerates, breccias
- Sand: Sandstone
- Silt: Siltstone
- Clay: Claystone, Mudstone, or shale if fissile
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What is chemical sediment?
rocks come from precipitation of dissolved minerals
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What is biochemical sediments?
-plant and animal shells or skeletons
- Limestone: either, comes from precipitated calcite,
- maybe in form of shells or shell fragments
- Chert: either biogenic or non-biogenic precipitated quartz
- Coal: biogenic, from compaction of plant material
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Rocks created by organisms are
Biogenic
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What is bioclastic?
Rocks that are composed of shells or shell pieces
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Sedimentary structures reveal the history of the Earth's surface by what things
- 1.Bedding
- 2.Graded bedding (turbidites)
- 3.Cross-bedding
- 4.Ripple marks
- 5.Mudcracks
- 6.Fossils (Paleontology)
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What is bedding or stratification?
- -the single most characteristic feature of sediments
- -can originate in a river, floodplain, or in any basin
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What is graded bedding?
forms when moving water suddenly slows down, dropping its sediment load (more energy=bigger grains)
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What are turbidites?
piles of sediment that accumulate on the continental shelf- triggered by earthquakes
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What is cross-bedding?
- forms when currents are present (wind or water)
- -windward slide=shallow side
- -leeward slide=steep side
- *wind changes direction
- *water has constant direction
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What are ripple marks?
- small ridges with intervening troughs, giving them somewhat of a corrugated appearance.
- Some ripple marks are symmetric and some are asymmetric
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What are mudcracks?
clay-rich sediment that dries and shrinks and develops intersecting fractures called mudcracks
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What is sediment?
Products of physical and chemical weathering
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What does the condition of the sediment tell you?
Tells you something about where it came from and how it got there
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What is a sedimentary rock?
formed when sediment is lithified
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