Sedimentary rocks
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Sedimentary Rocks. Bits and Pieces. Sedimentary rocks form as sediment is: l Deposited l Buried l Compacted l Cemented. Sedimentary rocks fall into 3 groups:. Clastic/inorganic Organic Chemical. Physical Weathering.

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Sedimentary Rocks

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Sedimentary Rocks

Bits and Pieces


Sedimentary rocks form as sediment is:

lDeposited

lBuried

lCompacted

lCemented


Sedimentary rocks fall into 3 groups:

  • Clastic/inorganic

  • Organic

  • Chemical


Physical Weathering

  • Clastic sediments are produced when rock physically weathers, which means it breaks apart.

  • Big rocks break into smaller rocks.

  • Weathering is an extremely slow process.


There are 6 sizes of clastic sediments.

  • Boulders

  • Cobbles

  • Pebbles

  • Sand

  • Silt

  • Clay


Particles are collected and transported by running water.

http://www.youtube.com/watch?v=fATA1SOLICo


Abrasion

  • Sediments become smoothed and rounded as they bounce along the bottom of the stream and hit against each other.


Deposition and Sorting

  • A stream loses velocity when entering quiet waters so its ability to transport sediment decreases. Particles drop to the bottom. This is deposition.

  • Large particles settle first. Other particles settle according to size. Smallest particles last. This is sorting.


Burial and Compaction

  • As more sediments accumulate, the bottom ones are buried.

  • This increased weight of the top sediments physically squeezes the lower sediments together which compacts them.

Heavy Weight

OUCH!


Cementation

  • All the waters of the Earth contain dissolved minerals. These dissolved minerals and sometimes clay fill up spaces between the rock fragments and bind them together. This is cementation.


Stratification

  • Sedimentary rocks often form in horizontal layers called strata.


Fossils

  • These layers or strata often contain fossils.

  • Only sedimentary rocks contain fossils.


Fossil Structures

  • Mud cracks and ripple marks give evidence of environment at formation.


Organic(Bioclastic)Sediments

  • The remains of plants and animals. The two most common are shells and plant material.


Chemical Sediments

  • Chemical sediments form when water evaporates and the materials dissolved in the water precipitate (settle).


Bonneville Salt Flats

  • Home of the land speed record.

Thrust SSC –

763 mph

http://www.youtube.com/watch?v=LKQ-xj5C2m8


Yucca Mountain

  • Nuclear waste depository

http://www.youtube.com/watch?v=tbq9a2oyMAo

http://www.youtube.com/watch?v=Q41vzLjwZqM


Characteristics of Sedimentary Rocks

  • Sedimentary rocks are the most common type of rocks on Earth’s surface.

  • Sedimentary rocks usually form underwater.

  • Sedimentary rocks may contain fossils.

  • Sedimentary rocks often form in layers or strata.

  • Sedimentary rocks are our keys to the past.


Nature’s Palette

Antelope Canyon


Bryce Canyon


Mexican Hat


Clastic Sedimentary Rocks

  • Breccia – angular

  • Conglomerate - rounded


Clastic Sedimentary Rocks

  • Sandstone – can be various size grains.


Clastic Sedimentary Rocks

  • Siltstone


Clastic Sedimentary Rocks

  • Shale – breaks along bedded planes.


Bioclastic Sedimentary Rocks

  • Bituminous coal – plant remains = carbon


Bioclastic Sedimentary Rocks

  • Limestone – cemented shell fragments or precipitates of biologic origin = calcite


Chemical Sedimentary Rocks

  • Rock salt - Crystalline texture composed of halite.


Chemical Sedimentary Rocks

  • Dolostone – Crystalline texture composed of dolomite.

Fossil


Chemical Sedimentary Rocks

  • Rock Gypsum – Crystalline texture composed of gypsum.


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