Sedimentary Rocks
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Sedimentary Rocks. Sedimentary Rocks. Made up of different types of sediments Loose fragments of rock, minerals & organic material . Characteristics. Determined by: Source of sediment Way the sediment was moved Deposition conditions. Formation.

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Sedimentary Rocks

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Sedimentary rocks

Sedimentary Rocks


Sedimentary rocks

Sedimentary Rocks

  • Made up of different types of sediments

    • Loose fragments of rock, minerals & organic material


Characteristics

Characteristics

  • Determined by:

    • Source of sediment

    • Way the sediment was moved

    • Deposition conditions


Formation

Formation

  • Sediments are transported by: wind, water or ice

  • Source determines the composition

  • Once sediment is deposited: (2 main processes)

    • Compaction

    • Cementation


Classification

Classification

  • Classified according to:

    • Processes by which they form

    • Composition of the rock

  • 3 main classes:

    • Chemical

    • Organic

    • Clastic

      *Each class can contain their own groups


Chemical sedimentary rocks

Chemical Sedimentary Rocks

  • Forms from minerals that were once dissolved in water

  • 2 ways:

    • Minerals precipitate out of the water

    • Water evaporates leaving minerals behind, evaporites


Organic sedimentary rocks

Organic Sedimentary Rocks

  • Forms from the remains of living things

  • Calcium Carbonates (CaCo3)


Clastic sedimentary rocks

Clastic Sedimentary Rocks

  • Rock fragments that are compacted & cemented together

  • Classified by the size of their sediments

    • Conglomerate-2mm to boulders

    • Breccia-angular & sharp edges

    • Sandstones-sand-sized grains cemented together

    • Shales-clay-size particles that are compacted & cemented together


Sedimentary rocks

Sedimentary Rocks:

Part 2


Characteristics of clastic sediments

Characteristics of Clastic Sediments

  • Physical characteristics are determined by:

    • Distance the particles move

    • Agent that moves the particles

  • 2 characteristics that are affected by transport:

    • Sorting

    • Angularity


Sorting

Sorting

  • Tendency for currents of air or water to separate sediments according to size

    • Well sorted—all grains are about the same size

    • Poorly sorted—grains are all different sizes

    • In between


Angularity

Angularity

  • How round & smooth or angular & uneven a sediment is can tell about the distance the sediment has traveled

  • The farther sediment travels from its source, the smoother the particles of sediment become


Sedimentary rock features

Sedimentary Rock Features

  • Depositional environments—setting in which sediment was deposited

  • Common environments:

    • Rivers, lakes, deltas, beaches & oceans

  • Have different characteristics that create specific structures


7 sedimentary rock features

7 Sedimentary Rock Features

  • Stratification

  • Cross-beds

  • Graded Bedding

  • Ripple Marks

  • Mud Cracks

  • Fossils

  • Concretions


Stratification

Stratification

  • Layering of rock

  • Shows when the conditions of sediment deposition change


Cross beds

Cross Beds

  • Slanting layers that form within beds

  • Generally form in sand dunes or river beds


Graded bedding

Graded Bedding

  • Occurs when different sizes & shapes of sediment settle to different levels.

  • Usually largest grains are on bottom & smaller on top

  • Reverse-grading can happen


Ripple marks

Ripple Marks

  • Caused by the action of wind or water on sand.

  • Indicate that a beach or river was once present


Mud cracks

Mud Cracks

  • Form when muddy deposits dry & shrink

  • Found on dry lake beds or flood plains


Fossils

Fossils

  • Remains or traces of ancient plants & animals


Concretions

Concretions

  • Form when minerals precipitate from fluids build up around a nucleus


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