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Lab 6. Sedimentary, my dear Watson. Weather and Sediment. Chemical weathering – chemical decomposition or dissolution of a material (into a solution). Physical weathering – physical decomposition of a material (into grains or clasts). Weather and Sediment.
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Lab 6 Sedimentary, my dear Watson
Weather and Sediment • Chemical weathering – chemical decomposition or dissolution of a material (into a solution). • Physical weathering – physical decomposition of a material (into grains or clasts).
Weather and Sediment • Sediment – loose grains/chemical residues or rocks, minerals, plants & animals • Erosion – transport of weathered sediments
Sedimentary Rocks • Form when: • Sediments collect, compact & harden: • Lithification • Mineral crystals precipitate from an aqueous solution • Sedimentary rocks are classified by: • Composition • Texture
Sedimentary Composition • Detrital (siliciclastic) – • Rock or mineral fragments • Quartz, feldspar, clay, or lithic fragments • Chemical – • Precipitated from aqueous solution • Calcite, dolomite, halite, gypsum, iron bearing minerals, chert • Biochemical (bioclasts) – • Grains are remains of organisms • See page 116 in lab manual
Sedimentary Textures • Grain size: • Deposits • Gravel size > sand sized > silt sized > clay sized • Precipitates • Crystalline > microcrystalline
Sedimentary Textures • Grain shape: • Describes the smoothness of the edges of grains • Well rounded to angular
Sedimentary Textures • Grain arrangement: • Describes sorting of the grains • Poorly sorted, moderately sorted, well sorted • See page 111 in lab manual
Depositional environment?? • Detrital? • Precipitates? • Biochemical/bioclasts?