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Sedimentary Rocks. What is a sedimentary rock?. Sedimentary rocks are products of mechanical and chemical weathering They account for about 5 percent (by volume) of Earth’s outer 10 kilometers Contain evidence of past environments Provide information about sediment transport

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what is a sedimentary rock
What is a sedimentary rock?
  • Sedimentary rocks are products of mechanical and chemical weathering
  • They account for about 5 percent (by volume) of Earth’s outer 10 kilometers
  • Contain evidence of past environments
      • Provide information about sediment transport
      • Often contain fossils
what is a sedimentary rock1
What is a sedimentary rock?
  • Sedimentary rocks are important for economic considerations because they may contain
      • Coal
      • Petroleum and natural gas
      • Sources of iron, aluminum, and manganese
Fossil Fish - 50 Million Year Old Lakes in southern Wyoming

These fish tell us the Wyoming climate

50 million years ago.

Sedimentary Rock made of fine-grained mudstone.

sedimentary rocks1
Sedimentary Rocks
  • Sedimentary – form in water
      • Generally formed by the deposition, burial, compaction, and cementation of sediments (pieces of other rocks)
  • 3 Types
      • Clastic
      • Chemical (crystalline)
      • Organic (Bioclastic)
3 types of sedimentary rocks
3 Types of Sedimentary Rocks:
  • Clastic (also called Detrial)—made of broken pieces of other rocks
3 types of sedimentary rocks1
3 Types of Sedimentary Rocks:

Organic—remains of plants and animals are deposited in thick layers

  • Examples
  • Fossil rich limestone is made from the shells of ocean animals; used to make chalk
3 types of sedimentary rocks2
3 Types of Sedimentary Rocks:
  • Chemical—minerals dissolved in lakes, seas, or underground water

Mineral crystals are made as the shallow water that has flooded the bottom of Death Valley evaporates. Click on image for full size (66K JPG)Courtesy of Martin Miller, University of Oregon

detrital sedimentary rocks
Detrital sedimentary rocks
  • The chief constituents of detrital rocks include
      • Clay minerals
      • Quartz
      • Feldspars
      • Micas
  • Particle size is used to distinguish among the various types of detrital rocks
classification of sedimentary rocks
Classification of sedimentary rocks
  • Two major textures are used in the classification of sedimentary rocks
      • Clastic
        • Discrete fragments and particles
        • All detrital rocks have a clastic texture
      • Nonclastic
        • Pattern of interlocking crystals
        • May resemble an igneous rock
detrital sedimentary rocks2
Detrital sedimentary rocks
  • Common detrital sedimentary rocks (in order of increasing particle size)
    • Shale
      • Mud-sized particles in thin layers that are commonly referred to as laminea
      • Most common sedimentary rock
detrital sedimentary rocks3
Detrital sedimentary rocks
  • Sandstone
    • Composed of sand-sized particles
    • Forms in a variety of environments
    • Sorting, shape, and composition of the grains can be used to interpret the rock’s history
    • Quartz is the predominant mineral
B. Descriptions of individual clastic rocks



Quartz Sandstone

world s biggest rock
World’s Biggest Rock
  • The Ayers Rock is made up of arkose, a course-grained sandstone rich in feldspar at least 2.5 km thick. Uplifting and folding between 400-300 mya turned the sedimentary layers nearly 90 degrees to their present position. The surface has then been eroded.
detrital sedimentary rocks4
Detrital sedimentary rocks
  • Alternating sequences of shale and sandstone exposed in the Grand Canyon. Shale cannot support steep cliffs or form erosion
detrital sedimentary rocks5
Detrital sedimentary rocks
  • Conglomerate and breccia
    • Both are composed of particles greater than 2mm in diameter
    • Conglomerate consists largely of rounded gravels
    • Breccia is composed mainly of large angular particles
characteristics of sedimentary rocks
Characteristics of sedimentary rocks
  • Sorting – the distribution of grain sizes in a rock

Sorting depends on properties of the depositing agent


Glacier deposit – poorly sorted

Sand dune – well sorted

3 types of sedimentary rock
3 Types of Sedimentary Rock


  • Clastic
    • Formed from the deposition, burial, compaction, and cementation of sediments (fragments of other rock)

Grain Size


3 types of sedimentary rock1
3 Types of Sedimentary Rock
  • Chemical (crystalline)
    • Precipitates – minerals fall out of solution when the water chemistry changes
    • Evaporates – minerals left behind when water evaporates
chemical sedimentary rocks
Chemical sedimentary rocks
  • Consist of precipitated material that was once in solution
  • Precipitation of material occurs in two ways
      • Inorganic processes
      • Organic processes (biochemical origin)
chemical sedimentary rocks1
Chemical sedimentary rocks
  • Common chemical sedimentary rocks
      • Limestone (calcareous deposits)
        • Most abundant chemical rock
        • Composed chiefly of the mineral calcite
        • Marine biochemical limestones form as coquina (broken shells), and chalk
chemical sedimentary rocks2
Chemical sedimentary rocks
  • Common chemical sedimentary rocks
      • Dolostone (siliceous deposits)
        • Typically formed secondarily from limestone
      • Chert (siliceous deposits)
        • Made of microcrystalline quartz
        • Varieties include flint and jasper (banded form is called agate)
sedimentary rocks2
Sedimentary Rocks
  • Quartz (SiO2)

“flint”, “chert”

chemical sedimentary rocks3
Chemical sedimentary rocks
  • Common chemical sedimentary rocks
      • Evaporites (saline deposits)
        • Evaporation triggers deposition of chemical precipitates
        • Examples include rock salt and rock gypsum
Chemical and Biochemical Rocks

Evaporites (Halite and Gypsum)

Chemical and Biochemical Rocks








Chemical and Biochemical Rocks



examples of sedimentary features and landforms
Examples of Sedimentary Features and Landforms

Narracoorte Caves, southeastern SA

The Queen’s Throne- Utah

Stalactites (of mineral calcite). Biochemical and inorganic sedimentary limestone rocks.

chemical sedimentary rocks4
Chemical sedimentary rocks
  • Common chemical sedimentary rocks
      • Coal (Carbonaceous deposits)
        • Different from other rocks because it is composed of organic material
        • Stages in coal formation (in order)
          • 1. Plant material
          • 2. Peat
          • 3. Lignite
          • 4. Bituminous
sedimentary environments
Sedimentary environments
  • A geographic setting where sediment is accumulating
  • Determines the nature of the sediments that accumulate (grain size, grain shape, etc.)
sedimentary environments1
Sedimentary environments
  • Types of sedimentary environments
      • Continental
        • Dominated by erosion and deposition associated with streams
        • Glacial
        • Wind (eolian)
      • Marine
        • Shallow (to about 200 meters)
        • Deep (seaward of continental shelves)
sedimentary environments2
Sedimentary environments
  • Types of sedimentary environments
      • Transitional (shoreline)
        • Tidal flats
        • Lagoons
        • Deltas
sedimentary environments3
Sedimentary environments
  • Sedimentary facies
      • Different sediments often accumulate adjacent to one another at the same time
      • Each unit (called a facies) possesses a distinctive set of characteristics reflecting the conditions in a particular environment
      • The merging of adjacent facies tends to be a gradual transition
characteristics of sedimentary rocks1
Characteristics of Sedimentary Rocks
  • May stratified because the sediments are laid down in horizontal layers called strata. ( one layer is called stratum)
  • May also contain fossil i.e: remains, prints or other indications of plants & animals found buried in rocks

Dipping sedimentary layers of rock, Rocky Mountains, Canada.

sedimentary structures
Sedimentary structures
  • Provide information useful in the interpretation of Earth history
  • Types of sedimentary structures
      • Strata, or beds (most characteristic of sedimentary rocks)
      • Bedding planes that separate strata
fossils evidence of past life
Fossils: Evidence of past life
  • By definition, fossils are the traces or remains of prehistoric life now preserved in rock
  • Fossils are generally found in sediment or sedimentary rock (rarely in metamorphic and never in igneous rock)
fossils evidence of past life1
Fossils: Evidence of past life
  • Geologically fossils are important for several reasons
      • Aid in interpretation of the geologic past
      • Serve as important time indicators
      • Allow for correlation of rocks from different places
features of sedimentary rocks
Features of Sedimentary Rocks
  • Stratification (bedding) is when layers of sedimentary rocks form stacked on top of each other
features of sedimentary rocks1
Features of Sedimentary Rocks
  • Ripple Marks are sand patterns formed by the action of winds, streams, waves, or currents
features of sedimentary rocks2
Features of Sedimentary Rocks
  • Mud Cracks develop in clay when it dries out and hardens into rock.