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Sedimentary Rocks

Sedimentary Rocks . Sedimentary rocks form when weathered sediment is deposited and is lithified. Review. What is: Sediment Weathering Deposition Lithification. Formation of Sedimentary Rocks. Lithification? The process of cementing and/or compacting sediment together.

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Sedimentary Rocks

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  1. Sedimentary Rocks • Sedimentary rocks form when weathered sediment is deposited and is lithified. • Review. What is: • Sediment • Weathering • Deposition • Lithification

  2. Formation of Sedimentary Rocks • Lithification? • The process of cementing and/or compacting sediment together. • In the lab we did the other day (sand and food), which one represented compaction and which one represented cementation and why? • What is an evaporite? • Rocks that form after water has evaporated

  3. Subclasses of Sedimentary Rocks • What’s a subclass? • Sedimentary rocks are sub-classified by the processes by which the rocks form and by the composition of the rocks. • The three main sub-classes of sedimentary rocks are: • Clastic • Chemical • Organic

  4. Clastic Sedimentary Rock • Clastic is Latin for “broken.” • Clastic sedimentary rocksform when fragments of preexisting rocks are compacted or cemented together • Clastic sedimentary rocks are classified by the size and shape of the sediments they contain.

  5. Classification of Clastic Sedimentary Rocks

  6. Characteristics of Clastic Sediments • The physical characteristics of sediments are determined by the how much weathering took place before lithification. • Lots of weathering = smaller and rounded sediment • Little weathering = larger and more angular sediment

  7. Characteristics of Clastic Sediments • The tendency for currents of air or water to separate sediments according to size is called sorting. • Happens during weathering and erosion • Well-sorted sediments, all of the grains are roughly the same size and shape. • Poorly sorted sediment consists of grains that are many different sizes.

  8. Chemical Sedimentary Rocks • chemical sedimentary rocks form when minerals precipitate (solid out of liquid) when water evaporates. • When water evaporates, the minerals that were dissolved in the water are left behind. • What lab was this like? • Rocks that form through evaporation are called evaporites. Rock gypsum and rock salt are common evaporites.

  9. Organic Sedimentary Rocks • organic sedimentary rocks form from the remains of plants or animals • Coal and some limestones are examples of organic rocks (shell limestone, coquina, and chemical limestone). • Organisms such as clams and coral make their shells from minerals. When the organism dies, their shells settle to the bottom of the ocean, accumulate, and are compacted and/or cemented to form limestone.

  10. Organic Sedimentary Rocks The diagram below shows the formation of organic limestone.

  11. Sedimentary Rock Summary

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