1. Sedimentary Rock
Section 3.3

2. Sedimentary Rocks
All sedimentary rocks begin to form when existing rocks are broken down into sediments through a process called weathering
Weathering is the process in which rocks are physically and chemically broken down by water, air, ice and gravity
Sediments are transported, by water, gravity, glaciers or wind, and eventually become compacted and cemented together, forming sedimentary rocks

3. Formation of Sedimentary Rocks
Sedimentary comes from the Latin word sedimentum, which means settling
There are several major processes that contribute to the formation of sedimentary rocks:
Weathering, Erosion and Deposition
Compaction and Cementation

4. Weathering, Erosion and Deposition
Weathering is any process that breaks rocks into sediments
Chemical weathering takes place when the minerals in rocks change into new substances
Erosion involves weathering and the transportation of sediments
Deposition is the process when water, wind, ice or gravity loses energy causing sediments to drop
Larger sediments are deposited first, smaller sediments are dropped later

5. Compaction and Cementation
Once sediments are deposited, they become lithified or turned into rock
Compaction is a process that squeezes, or compacts, sediments, pushing water out
Compaction is caused by the weight of sediments
Cementation takes place when dissolved minerals are deposited in the tiny spaces among the sediments

6. Classification of Sedimentary Rocks
Sedimentary Rocks can be classified into two main groups according to the way they form
Clastic – rocks that are made of weathered bits of rocks and minerals
Chemical – forms when dissolved minerals precipitate from water solutions

7. Clastic Sedimentary Rocks
Clastic sedimentary rocks are made of weathered bits of rocks and minerals
Clastic sedimentary rocks can be grouped according to the size of the sediments in the rocks
Conglomerate rocks are made up of rounded, gravel-size or larger particles
Breccia rocks have angular particles
Sandstone rocks have sediments that are sand-sized grains

8. Clastic Sedimentary Rocks
Breccia
Conglomerate
Clastic Sedimentary Rocks
Sandstone

9. Chemical and Biochemical Sedimentary Rocks
Chemical sedimentary rocks forms when dissolved minerals precipitate from water solutions
The precipitation generally occurs when water evaporates or boils off leaving a solid product
Examples include limestone, rock salt, chert, flint and rock gypsum
Biochemical sedimentary rocks contain shells and skeletal remains of organisms that settle to the ocean floor

10. Chemical Sedimentary Rocks
Chert
Rock Salt
Flint
Limestone

11. Biochemical Sedimentary Rocks

12. Features of some Sedimentary Rocks
Sedimentary rocks give clues to how, when and where the rocks formed
Layers of sedimentary rock records a period of sediment deposition. The oldest layers are found at the bottom
Ripple marks may indicate that the rock was formed along a beach or stream bed
Mud cracks are formed when wet mud or clay dried and shrank, leaving a record of a dry environment
Fossils found in sedimentary rocks can help answer questions about the rock

13. Mud cracks
Fossils
Layers of sedimentary rock
Ripple marks

14. Summary of Sedimentary Rocks
Sedimentary rocks form as the result of five major process
Weathering produces particles called sediments
Wind, water, ice and gravity erode and deposit sediments
Sediments are compacted and cemented to form sedimentary rocks
Sedimentary rocks can be classified according to how they form, by using rock formation, texture and composition

15. (Table 2 on page 79)