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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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Sedimentary Rocks

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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



















Sedimentary rocks

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


    Sedimentary rocks

    B. Descriptions of individual clastic rocks

    Arkose

    Graywacke

    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



    Sorting
    Sorting

    Glacier deposit – poorly sorted

    Sand dune – well sorted


    3 types of sedimentary rock
    3 Types of Sedimentary Rock

    Examples

    • Clastic

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

    Grain Size

    Composition


    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


    Sedimentary rocks




    Sedimentary rocks


    Sedimentary rocks

    Limestones

    Chalk

    Coquina

    Fossiliferous




    Sedimentary rocks


    Sedimentary rocks

    Sinkhole: a circular depression in a karst area, commonly funnel-shaped.



    Examples of sedimentary features and landforms
    Examples of Sedimentary Features and Landforms standing on air!

    Narracoorte Caves, southeastern SA

    The Queen’s Throne- Utah

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

    http://www.uh.edu/~jbutler/physical/chapter7.html





    Chemical sedimentary rocks4
    Chemical sedimentary rocks caves.

    • 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 rocks
    coal caves.


    Sedimentary environments
    Sedimentary environments caves.

    • A geographic setting where sediment is accumulating

    • Determines the nature of the sediments that accumulate (grain size, grain shape, etc.)


    Sedimentary environments1
    Sedimentary environments caves.

    • 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 caves.

    • Types of sedimentary environments

      • Transitional (shoreline)

        • Tidal flats

        • Lagoons

        • Deltas



    Sedimentary environments3
    Sedimentary environments 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


    Sedimentary facies
    Sedimentary facies environments


    Characteristics of sedimentary rocks1
    Characteristics of Sedimentary Rocks environments

    • 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.

    http://www.geog.ouc.bc.ca/physgeog/contents/10f.html


    Sedimentary structures
    Sedimentary structures environments

    • 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 environments

    • 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 environments

    • 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 environments

    • Stratification (bedding) is when layers of sedimentary rocks form stacked on top of each other


    Features of sedimentary rocks1
    Features of Sedimentary Rocks environments

    • Ripple Marks are sand patterns formed by the action of winds, streams, waves, or currents


    Features of sedimentary rocks2
    Features of Sedimentary Rocks environments

    • Mud Cracks develop in clay when it dries out and hardens into rock.


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