Sedimentary Rocks.pptx

Sedimentary Rock
Formation of sedimentary rock
Classification pf sedimentary rock

1. Applied geology Name:Muhammad Umar shaikh

2. Contents Sedimentary Rock Formation of sedimentary Rock it’s Classification

3. Sedimentary Rock What is Sediment? Sediments are loose material such as rock fragments, mineral grains, and remains of some organisms. Sedimentary Rock: Sedimentary rock are derived from the Latin word “Sedimentum” means “Settle Down”. A rock that has been derived through pre-existing rock by the process of Erosion,Transportation and Deposition by natural ageries such as wind water. Sedimentary rock forming the earth crust cover about 75% of the continental area nearly 100% of the oceanic floor..

4. Formation of sedimentary Rock Sedimentary rock account for approximately 5% of the crust. The upper 16Km of Earth. Regardless of this low percentage, approximately 75% of all rocks exposed at the surface is Sedimentary rock . Factors leading to the formation of sedimentary rocks include; Erosion and Weathering Transportation Deposition Transformation of the deposited material.

5. Erosion and Weathering In reference to the Rock Cycle, the origin of sedimentary rock begins with the processes of Weathering and Erosion. Pre-existing rocks can be broken down both mechanically or chemically to produce Sediment. Mechanical Weathering: Mechanical Weathering happens when a Material is broken into smaller pieces still retain the characteristics of original material. Example: freeze – thaw action

6. Chemical Weathering Chemical Weathering happens when a material is altered by chemical action and a new material is produced which is chemically different than the original material. Examples: Statues and headstones

7. Transportation of Sediment Erosional agents (such as; wind, water & Ice,) influenced by gravity, transport the Sediment to new locations where it is deposited. Sediment is broken down during the Transport phase. This process is called Abrasion. Three main agents tend to transport the Sediment, these being; Water (Rivers and groundwater) Ice (Glaciers) Wind

8. Deposition of the Material The eroded material which is transported by the transporting agents is deposited sooner or later depending upon the circumstances. These Sediments continue to accumulate in suitable basins of sedimentation.

9. Transformation of the deposited material After Sometime when the accumulation is sufficient, the loose rock particles are subjected to compaction (sometime due to overlaying Sediments or earth movements) And finally conversion into sedimentary rocks, under favourable circumstances. The process pf transformation of loose rock particle into hard and massive sedimentary rock is achieved through the the following two ways: ( i ) Welding (ii) Cementation

10. Welding & Cementation Welding: Sometimes the Sediments are compacted under the Influence of pressure. As a result of the compaction, the water present in the Sediment is squezed out. This process invariably result in a very dense packing of the sediments, which are firmly held together; as if they are subjected to welding. Cementation: Sometimes the sediments are Held together by a foreign binding or cementing material (as the stone chip are held together by the cement mortor ). This cementing material is generally supplied by the percolating waters.The most common cementing materials are carbonates pf calcuim and magnesium as well as oxides of iron and silicon.

11. Classification of sedimentary rocks The sedimentary rock have been classified by different scientists on different bases. But there is no definite classification, which may be accepted universally. The following two classification are important from the subject point of view: Classification based on the grain-Size of the sediments of the rocks. Classification based on the mode of formation or origin of the rocks.

12. Classification based on the grain-Size of the sediments of the rocks. Sedimentary rocks may be classified on the basis of grain-size of their sediments into the following three groups: Argillaceous Arenaceous Rudaceous

13. Argillaceous: Argillaceous (Latin, arigilla =clay) are those sedimentary rocks which are made up from the finest clay particles. Arenaceous : Arenaceous (Latin, Arena=Sand) are those sedimentary rock which are made of particles, having grain size between 1/10 mm and 2 mm in diameter. Rudaceous : Rudaceous (Latin, Rudnus =rubble) are those sedimentary rock which are made of particles, having grain size more than 2 mm in diameter.

14. Classification based on the mode of formation or origin of the rocks. Sedimentary rocks may be classified on the basis of their mode of origin into the following three groups: Mechanical Origin Chemical Origin Organic Origin

15. Mechanical Origin: All those sedimentary rocks, which are derived from the pre existing rocks by the mechanical action (disintegration i.e ; fraction and abrasion, Transportation , Deposition amd consolidation) of the denuding agents, without any change in their chemical composition, are called sedimentary rocks of Mechanical Origin. Chemical Origin: All those sedimentary rocks, which are derived from the pre existing rocks by the chemical action (decomposition, precipitation crystallization, etc ) of the denuding agents, are called Sedimentary rocks of Chemical Origin. Organic Origin: All these sedimentary rocks, which are derived from the pre existing rocks by the activities of the organisms (Both plants and animals) are called sedimentary rocks of Organic Origin.