1. Chapter 3.3
Sedimentary Rocks

2. Sedimentary Rocks
The word sedimentary comes from the latin word sedimentum, which means “settling”.
Sedimentary rocks form when sediments settle out and are deposited, usually from water, but occasionally from wind or glaciers.

3. Weathering, Erosion, and Deposition
The first three processes involved in the formation of Sedimentary Rocks are Weathering, Erosion, and Deposition.
Weathering means to break rock down into smaller parts called sediment.
Erosion is when the broken rock fragments are carried away by water, wind, or ice (glaciers).
Deposition is when the water, wind, or ice slows down enough to deposit the sediment.

4. Weathering, Erosion and Deposition
This River is Eroding away the
Sediments of this Canyon
Example of Weathering
Sediment is being Deposited
By this River Delta
Environments of Deposition
Summary of the Process

5. Deposition and Sorting
Because gravity plays a factor when sediments are transported by water, wind, and ice, the heaviest and largest sediments settle out first and the smallest settle out last. This causes a process in geology known as sorting.

6. Compaction and Cementation
After the sediments become deposited, they must first get compacted or squeezed by the pressure and weight of more sediment on top.
Compaction squeezes the water out, leaving behind minerals in the spaces left behind.
Those dissolved minerals act like a glue to cement the sediments together.

7. Compaction and Cementation

8. Classification of Sedimentary Rocks
Sedimentary Rocks are grouped by Geologists into two different groups based on the way they were formed.
Clastic Sedimentary Rocks are made up of broken rock fragments called clastics.
Chemical Sedimentary Rocks are usually formed when dissolved minerals separate out of water. But they can also be formed by biological processes.

9. Clastic Sedimentary Rocks
Clastic Sedimentary Rocks can further be classified based on grain size.
Clastic Sedimentary Rocks, classified by grain size can also be subdivided by grain composition, maturity and sorting.

10. Classification of Clastics by Grain Size, Maturity, Composition and Sorting

11. Classification of Clastics

12. Clastic Sedimentary Rocks
Breccia
Quartz Sandstone
Conglomerate
Arkose Sandstone – sand grains mixed with feldspar
Siltstone – Feels like fine sandpaper
Shale – Very fine sandpaper with the consistency of flour

13. Chemical Sedimentary Rocks
Chemical Sedimentary Rocks are a little more complicated than the clastics.
Chemical Sedimentary Rocks with the mineral calcite can be further classified by texture.
Crystalline Limestone and Travertine have a coarse crystalline texture.
Coquina, Fossiliferous Limestone, and Chalk all have seashell of various sizes mixed in them.

14. Chemical Sedimentary Rocks made of the mineral Calcite
Coquina – Loosely Compacted shells cemented together
Crystalline Limestone
Travertine
The nice thing about all of these rocks is that all of them react with acid, because they are made of the mineral calcite.
Fossiliferous Limestone
Chalk

15. Other Chemical Sedimentary Rocks
Flint and Chert are both made of Quartz so they are very hard and can scratch glass.
Conchoidal fracture is also a property that can help identify both Flint and Chert.
Gypsum and Rock Salt both have a crystalline texture, but only rock salt has a salty taste, and neither one of these reacts with acid.
Bituminous Coal has a dark black color.

16. Other Chemical Sedimentary Rocks
Chert
Chert and Flint Arrowheads
Gypsum
Rock Salt
Bituminous Coal
Coal Seams in Alaska