Process of Formation of Sediments and Sedimentary Rocks
Process of Formation of Sediments and Sedimentary Rocks
- All these terms are part of syllabus.
- For weathering, erosion, transportation, please refer Geomorphology lectures.
Formation of Sedimentary rocks
It takes place in three stages:
- Weathering and erosion
- Sedimentation
- Lithification and Diagenesis
1. Weathering and erosion
- Pre-existing rocks are broken down into sediments.
- Sediments are transported and roughly sorted.
- Sorting order- large to small: bigger sediments like gravels à sand à clay
- Weathering: The solid rock is transformed into smaller fragments or dissolved ions by physical and chemical weathering.
- Erosion: Erosion is several processes which act together to lower the surface of the earth. Erosion overlaps with transportation.
- Transportation: Erosion begins the transportation process by moving the weathered products from their original location. This can take place by gravity, by running water, by wind, or by moving ice etc. The distance of transported sediment and the energy of the transporting medium gives an idea about the mode of transportation.
2. Sedimentation
- Sediments carried in solution precipitates and accumulates at deposition site.
- Deposition: Sediment is deposited when the energy of the transporting medium becomes too low to continue the transport process. The final sediment thus reflects the energy of the transporting medium.
3. Lithification and Diagenesis
- It includes processes like compaction, digenesis, and cementing etc.
- It is discussed below in details in next topic.