Sedimentary Rocks/EPCC/LM5 B
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Sedimentary Rocks/EPCC/LM5 B Sedimentary Rocks/EPCC/LM5 B Presentation Transcript

  • Chapter 7: Sediments andChapter 7: Sediments and Sedimentary RocksSedimentary Rocks
  • Sedimentary RocksSedimentary Rocks Two Categories:Two Categories: Clastic(Detrital) and ChemicalClastic(Detrital) and Chemical
  • Sedimentary RocksSedimentary Rocks • Clastic ( or detrital) sedimentary rocks reflect several processes. – Weathering – Generation of detritus via rock disintegration. – Erosion – Removal of sediment grains from rock. – Transportation – Dispersal by wind, water and ice. – Deposition – Accumulation after cessation of transport. – Lithification – Transformation into solid rock. • Burial – Continued deposition buries sediments. • Compaction – Squeezing by the weight overlying material. • Cementation – Grains “glued” by pore-filling minerals.
  • Sediments In The Rock CycleSediments In The Rock Cycle • Sediments are transported by: – Water. – Ice. – Wind. – Gravity. • The transport and deposition of sediments are initial phases of the rock cycle. • The ultimate fate of most sediment is burial and conversion to sedimentary rock.
  • Sediments Types AndSediments Types And CharacteristicsCharacteristics • Three broad classes: – Clastic sediment is loose fragments of rock debris produced by physical weathering. – Chemical sediment precipitates from solution in water. – Biochemical/Biogenic/Bioclastic sediment is composed of the fossilized remains of plants or animals.
  • Characteristics of ClasticCharacteristics of Clastic Sediment (1)Sediment (1) • Clastic sediment is divided into four main size classes: – Gravel and larger ( 2mm and larger) – Sand (0.0625 to 2 mm) – Silt (0.0625 to 0.0039 mm) – Clay (less than 0.0039 mm)
  • Characteristics of ClasticCharacteristics of Clastic Sediment (2)Sediment (2) • Gravel is subdivided into: – Boulder gravel. – Cobble gravel. – Pebble gravel.
  • SortingSorting • Sorting identifies sediment in terms of the variability in the size of its particles. – Poorly sorted (wide range of particle size), – Well sorted (range is small). • Changes of grain size typically result from fluctuations in the velocity of the transporting agent, such as water or wind.
  • Figure 7.2 Sorting in Sediments
  • Figure 7.4 Sorting, rounding and sphericity
  • SortingSorting • The greater the speed and energy involved, the larger or heavier are the particles that can be transported.
  • SortingSorting • Nonsorted sediment is a mixture of different sizes arranged chaotically. – Till is a nonsorted sediment of glacial origin. • Smooth and rounded particles are transported by water or air.
  • TransportTransport • Sediments move by air, wind, rain, water, organisms - With increasing transport, average grain size decreases.
  • Sedimentary RocksSedimentary Rocks Chemical/BiochemicalChemical/Biochemical
  • Characteristics of ChemicalCharacteristics of Chemical SedimentsSediments • Chemical sediments are formed by precipitation of minerals from solution in water. • They form in two principal ways: – Through biochemical reactions resulting from the activity of plants and animals in the water. – Inorganic reactions in the water. • When water from a hot spring cools, it may precipitate opal (a hydrated silicate) or calcite (calcium carbonate).
  • Some Chemical SedimentarySome Chemical Sedimentary RocksRocks
  • SaltsSalts • Evaporation of sea water or lake water forms salts. • Lake waters precipitate sodium carbonate (Na2CO3), sodium sulfate Na2SO4), borax (Na2B4O7.10H2O),and trona (Na2CO3.NaHCO3.2H2O).
  • Biochemical/BiogenicBiochemical/Biogenic SedimentsSediments • Biogenic sediments contain fossils. • If the remains are broken and scattered it is bioclastic sediment.
  • Depositional EnvironmentsDepositional Environments
  • Sedimentary or DepostionalSedimentary or Depostional EnvironmentsEnvironments • Each environment will have distinctive physical, chemical, and biological characteristics.
  • Figure 7.14
  • Sediments to RocksSediments to Rocks How do we do this?How do we do this?
  • How Sediment Becomes RockHow Sediment Becomes Rock • Lithification is the overall process of creating sedimentary rock.
  • How Sediment Becomes RockHow Sediment Becomes Rock • Processes involved include: – Compaction. • As the weight of an accumulating sediment forces the grains together. The pore space is reduced. – Cementation. • Substances dissolved in water precipitate to form a cement that binds the sediment grains together.
  • What do we call theseWhat do we call these rocks?rocks?
  • Clastic Sedimentary RocksClastic Sedimentary Rocks • The four basic classes of clastic sedimentary rocks are: – Conglomerate/Breccia, a lithified gravel. – Sandstone, consisting mainly of sand grains. – Siltstone, composed mainly of silt-size mineral fragments, commonly quartz and feldspar. – Mudstone, still-finer grain size.
  • Figure 7.24A
  • Figure 7.24B
  • Figure 7.24C
  • Chemical Sedimentary RocksChemical Sedimentary Rocks • Chemical sedimentary rocks result from Lithification of organic or inorganic chemical precipitates.
  • Figure 7.27B
  • Figure 7.27C
  • Rock Salt Rock Gypsum
  • Figure 7.27D Chert
  • Sedimentary StructuresSedimentary Structures Clues to the EarthClues to the Earth
  • Environmental clues inEnvironmental clues in sedimentary rockssedimentary rocks • Sedimentary rocks reflect the environment in which they were formed. • Clues from bedding planes. – Ripples marks preserved in sandstones and siltstones. – Footprints, trails, and raindrop impressions.
  • Clues in the RocksClues in the Rocks • Clues from fossils. – Some animals and plants are restricted to warm, moist climates, whereas others are associated only with cold, dry climates.
  • Figure 7.30 Ripples
  • Figure 7.31 Mud cracks
  • Crossbedding
  • Layering and fining upward
  • Tilted Bedding or strata
  • Trace Fossil Trace Fossil from Mt Cristo Rey
  • Where do we go next?Where do we go next? • Metamorphic Rocks