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Sedimentary Rocks. Rocks that form from an accumulation of sediments from pre-existing rocks and/or organic materials Rocks that form from an accumulation.

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Presentation on theme: "Sedimentary Rocks. Rocks that form from an accumulation of sediments from pre-existing rocks and/or organic materials Rocks that form from an accumulation."— Presentation transcript:

1 Sedimentary Rocks

2 Rocks that form from an accumulation of sediments from pre-existing rocks and/or organic materials Rocks that form from an accumulation of sediments from pre-existing rocks and/or organic materials Most sedimentary rocks are formed under large bodies of water (lakes, seas, oceans…) where sediments are usually deposited in horizontal layers Most sedimentary rocks are formed under large bodies of water (lakes, seas, oceans…) where sediments are usually deposited in horizontal layers

3 Methods of Formation Compaction and Cementation – When sand, silt, pebbles, etc… are cemented together by minerals that “glue” solid sediments together. Sediments can also be compacted or compressed together. *** CLASTIC sedimentary rocks are formed due to these two methods. *** Compaction and Cementation – When sand, silt, pebbles, etc… are cemented together by minerals that “glue” solid sediments together. Sediments can also be compacted or compressed together. *** CLASTIC sedimentary rocks are formed due to these two methods. *** CLASTIC SEDIMENTARY ROCKS are formed by compaction or cementation. CLASTIC SEDIMENTARY ROCKS are formed by compaction or cementation. Clastic sedimentary rocks are sorted by the sizes of the sediment that compose the rock Clastic sedimentary rocks are sorted by the sizes of the sediment that compose the rock

4 Clastic Sedimentary Rock Examples (see ESRT for exact sediment sizes) Conglomerate (cemented pebbles) Conglomerate (cemented pebbles)

5 Clastic Sedimentary Rock Examples Breccia (cemented jagged pebbles) Breccia (cemented jagged pebbles)

6 Clastic Sedimentary Rock Examples Sandstone (larger sediments) Sandstone (larger sediments)

7 Clastic Sedimentary Rock Examples Sandstone (BANDED sandstone example) Sandstone (BANDED sandstone example)

8 Clastic Sedimentary Rock Examples Siltstone (finer sediments) and shale (finest sediments) Siltstone (finer sediments) and shale (finest sediments)

9 Methods of Formation Chemical Action –When water evaporates, mineral crystals precipitate out of the water, forming chemical sedimentary rock. These “rocks” are often composed of just one mineral. Chemical Action –When water evaporates, mineral crystals precipitate out of the water, forming chemical sedimentary rock. These “rocks” are often composed of just one mineral. Examples: rock salt (composed of halite), rock gypsum (composed of gypsum), dolostone (composed of dolomite). Examples: rock salt (composed of halite), rock gypsum (composed of gypsum), dolostone (composed of dolomite).

10 Example: Chemically Formed Sedimentary Rock Rock Salt (formed from Halite) Rock Salt (formed from Halite)

11 Methods of Formation Organic Processes – Any rock made by living organisms or mostly composed of materials from life forms is an organic or BIO-CLASTIC sedimentary rock. Organic Processes – Any rock made by living organisms or mostly composed of materials from life forms is an organic or BIO-CLASTIC sedimentary rock. Examples: Limestone (cemented shell fragments by calcite) and Coal (from plant remains, composed of carbon) Examples: Limestone (cemented shell fragments by calcite) and Coal (from plant remains, composed of carbon)

12 Example: Organic Sedimentary Rock Limestone from Calcite with Fossils Limestone from Calcite with Fossils

13 Example: Organic Sedimentary Rock Limestone from Calcite with Fossils Limestone from Calcite with Fossils

14 Example: Organic Sedimentary Rock Limestone Limestone

15 Example: Organic Sedimentary Rock Coal Coal

16 Example: Organic Sedimentary Rock Coal Coal

17 Example: Organic Sedimentary Rock Coal Formation Coal Formation

18 Characteristics of Sedimentary Rocks Most are Clastic Most are Clastic Contain horizontal sorting or layering… beds or strata Contain horizontal sorting or layering… beds or strata Some may contain mud cracks, raindrop impressions, ripple marks… Some may contain mud cracks, raindrop impressions, ripple marks… Some organic sedimentary rocks contain fossils Some organic sedimentary rocks contain fossils


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