1. Sedimentary Rocks

2. Sedimentary Rocks
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

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. ***
CLASTIC SEDIMENTARY ROCKS are formed by compaction or cementation.
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)

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

6. Clastic Sedimentary Rock Examples
Sandstone (larger sediments)

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

8. Clastic Sedimentary Rock Examples
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.
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)

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.
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

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

14. Example: Organic Sedimentary Rock
Limestone

15. Example: Organic Sedimentary Rock
Coal

16. Example: Organic Sedimentary Rock
Coal

17. Example: Organic Sedimentary Rock
Coal Formation

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