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UI EES 1030 - Sedimentary Rocks

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EES 1030 1st Edition Lecture 6Sedimentary Rocks• Come from physical and chemical weathering• 75% of earth’s surface is sedimentary rocks. Importance of sedimentary rocks:• They are economically important because they have oil, natural gas, uranium, iron, aluminum, magnesium, ans phosphate fertilizer. • Provides cement and aggregate for construction.• Sedimentary rocks can contain fossils, which preserve earth’s history.• Sediments and sedimentary rock also provide a place for groundwater to be held. Sediment: collection of loose solid partSedimentary rocks: particles bound together to form a firm coherent rock.Types of sedimentary rocksDetrital sedimentary:• Materials that are derived from mechanical or chemical weathering and was transported as solidparticles• Common materials are clay, quartz, feldspars, and micas.• Particles > 2mm in diameter• Shale- silt and clay sized particles. Well over half of sedimentary rocks. • Shale has the ability to into thin layers along well developed, closely spaced planes. Called fissility.• Sandstone predominantly sand grain sized particles, most abundant after shale. • Conglomerate: consists largely of gravel. Can range in size from boulders to garden pees. • Breccia: large particles that are more angular than rounded Chemical Sedimentary Rock:• Ions that are carried in solution to lakes and seas • Most abundant chemical rock. Forms limestone, chert, and rock salt.• Oolithic limestone – inorganic • Organic Limestone’s: coral reefs, shell fragments, microorganisms. • Biochemical origin: organic processes of water dwelling organisms also form chemical sediments • Chalk: soft porous rock made up of hard parts of microscopic marine organisms.• Dolostone: made of calcium-magnesium. • Evaporites- waters of bay become saturated with salt from evaporation. Marine environment.Organic Sedimentary Rocks:• Coal is made of organic matter • Formed from the accumulation and lithification of organic debris (leaves roots, and plant/animal weather) • Organic rocks usually contain carbon and are black, soft, and fossiliferous.Sedimentary Structures: • Provide important information about the process of sedimentation• Cross-bedding: horizontal units that are internally composed of inclined layers• Current ripples: shows where water flow was.• Graded beds: vertical change in particle size. Deposited from turbidity current • Mudcracks: (desiccation) when muddy sediment dries and contracts leaving cracks in the ground.Sedimentary environments:• Transitional: shoreline, beaches, deltas, tidal flat, barrier island.• Marine: deep sea, continental shelf, organic reefs.• Continental: glacial, deserts, lakes, rivers.Sedimentary facies:• Different types of sediments can accumulate adjacent to one another at the same time.• Sediments can lie undisturbed for many years in sedimentary basins.Clastic: rocks that are composed of broken parts of other rocksNon-clastic: rocks formed from chemical reactions, mostly in the ocean.Diagenesis: process where sediments are lithified into sedimentary rocks. Cementation: the binding of particles or other things by cement.Compaction: part of the lithification process where sediments are pressed more tightly


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