Lab 4 notes

Lab 4 notes - Lab.4 Sedimentary Rocks, Processes, and...

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Lab.4 Sedimentary Rocks, Processes, and Environments 1. Sedimentary Rock : formed from sediments, the products of mechanical and chemical weathering. Importance: 75% of earth’s surface outcrop; contain fossils and energy resources. 2. Weathering : Chemical: decomposition or dissolution of earth materials; Mechanical: crushing, abrasion and other physical disintergration of earth materials. 3. Sedimentary process : the products of weathering (sediments) are transport by wind, water or ice and eventually rest in an environment of deposition where they accumulate or precipitate to form a sedimentary deposit. Then they are compressed and lithified (hardened) into sedimentary rock. Compaction : the process of pressure-hardening; Cementation : gluing together by tiny crystals or chemical residues. 4. Texture : size, shape and arrangement of sedimentary grains. Weathering, transportation and deposition all contribute to the texture of a sedimentary rock. Shape : Angular, sub-angular, rounded, well-rounded; the longer the sediments have been transported, the more roundness they have; Size : Wentworth classes: gravel (>2mm), sand (1/16-2mm), Mud (<1/16mm); Sort : Due to different velocities of wind and/or water current, the different sizes of sediments are separated naturally; poorly sorted sediments are composed of many different sizes of grains, which are usually caused by short transportation, well sorted sediments are composed of similar grain size and are usually accompanied with well-rounded grains because of long transportation. 5.
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Lab 4 notes - Lab.4 Sedimentary Rocks, Processes, and...

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