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Edit Comment Close Premium member Presentation Transcript Physical Geology: Sedimentary Rocks David Sallee Physical GeologyRocks: Materials of the Solid Earth: Rocks: Materials of the Solid EarthRock Cycle : Rock Cycle Shows the interrelationships among the three rock types Earth as a system: the rock cycle Magma Crystallization Igneous rock Weathering, transportation, and deposition Rock Cycle : Earth as a system: the rock cycle Sediment Lithification Sedimentary rock Metamorphism Metamorphic rock Melting Magma Rock Cycle Rock Cycle : Earth as a system: the rock cycle Full cycle does not always take place due to "shortcuts" or interruptions e.g., Sedimentary rock melts e.g., Igneous rock is metamorphosed e.g., Sedimentary rock is weathered e.g., Metamorphic rock weathers Rock Cycle Rock Cycle: Rock CycleWeathering, Sediment, and Sedimentary Rocks: Weathering, Sediment, and Sedimentary Rocks Sediment Mechanical and chemical weathering produces the raw materials for soil and sedimentary rock Sediment may be detrital or chemical, and sedimentary rocks may form by the deposition of particles or by biologic activity Detrital sedimentary particles and the rocks they form are classified according to size Gravel - >2mm in diameter Sand - 1/16mm to 2 mm Silt - 1/256mm to 1/16mm Clay - <1/256mmSedimentary Rocks : Sedimentary Rocks Form from sediment (weathered products) About 75% of all rock outcrops on the continents Used to reconstruct much of Earth's history Clues to past environments Provide information about sediment transport Rocks often contain fossils Weathering, Sediment, and Sedimentary Rocks: Weathering, Sediment, and Sedimentary Rocks Sediment Transport and Deposition Ice, water, and wind can all transport particles of various sizes to another location Abrasion and rounding SortingWeathering, Sediment, and Sedimentary Rocks: Weathering, Sediment, and Sedimentary Rocks Sediment Transport and Deposition Sediment can be carried a considerable distance from its source, eventually coming to rest in a depositional environment Continental Transitional MarineSedimentary Rocks : Sedimentary Rocks Sedimentary rocks are produced through lithification Loose sediments are transformed into solid rock Lithification processes Compaction Cementation by Calcite Silica Iron OxideWeathering, Sediment, and Sedimentary Rocks: Weathering, Sediment, and Sedimentary Rocks Lithification--Transforming Sediment into Sedimentary Rock Compaction reduction in pore space and volume Cementation reduction in pore space, increase in mechanical strength common cementing agents include: calcite, silica, iron oxideWhat Kinds of Sedimentary Rocks do Geologists Recognize?: What Kinds of Sedimentary Rocks do Geologists Recognize? Detrital Sedimentary Rocks Clastic texture, classified by size and shape Conglomerate, breccia, sandstone, siltstone, shale are commonWhat Kinds of Sedimentary Rocks do Geologists Recognize?: Chemical and Biochemical Sedimentary Rocks Consist of ions and compounds released by chemical weathering and precipitated by chemical reactions or by the metabolism of organisms Carbonates Limestones, dolostones Evaporites Halite, gypsum Coal What Kinds of Sedimentary Rocks do Geologists Recognize?Sedimentary Facies: Sedimentary Facies Deposits of sediment that have distinctive physical, chemical, or biological attributes Coarse-grained deposits in a high-energy depositional environment are adjacent to finer-grained sediments that are deposited in quieter water Facies are typically recognized by grain size Sedimentary Facies: Sedimentary Facies Transgression Rise in sea level relative to land, results in offshore facies being deposited over nearshore facies Regressions Fall in sea level relative to land, results in nearshore facies being deposited over offshore facies.Reading the Story in Sedimentary Rocks: Reading the Story in Sedimentary Rocks Determining the Environment of Deposition Geologists attempt to make interpretations about ancient environments based on analyses of rocks, fossils, and sedimentary structures and comparison with modern day processes Sedimentary Rocks : Sedimentary Rocks Features of sedimentary rocks Strata, or beds (most characteristic) Bedding planes separate strata Fossils Traces or remains of prehistoric life Are the most important inclusions Help determine past environments Used as time indicators Used for matching rocks from different places Reading the Story in Sedimentary Rocks: Reading the Story in Sedimentary Rocks Sedimentary Structures Strata or beds Graded bedding Cross-bedding Ripple marks MudcracksReading the Story in Sedimentary Rocks: Reading the Story in Sedimentary Rocks Fossils--Remains and Traces of Ancient Life Most organisms are uniquely adapted to their habitat, and the structure of fossil organisms and comparison to any living relatives is useful in determining ancient depositional environmentsSedimentary Rocks : Sedimentary Rocks Economic importance Coal Petroleum and natural gas Sources of iron and aluminum Are There More Important Resources in Sedimentary Rocks?: Are There More Important Resources in Sedimentary Rocks? Petroleum and Natural Gas Hydrocarbons that originate from the microscopic remains of marine organisms They migrate upward through porous rock until they encounter a structural or stratigraphic trapAre There More Important Resources in Sedimentary Rocks?: Uranium Most uranium used in North American nuclear reactors comes from carnotite, a mineral found in sedimentary rocks Banded Iron Formation Alternating layers of chert and iron oxide account for most of the iron mined today Are There More Important Resources in Sedimentary Rocks?Sedimentary Rocks : Sedimentary Rocks Classifying sedimentary rocks Two groups based on the source of the material Detrital rocks Material is solid particles Classified by particle size Common rocks include Shale (most abundant) Sandstone Conglomerate Classification of sedimentary rocks: Classification of sedimentary rocksShale with plant fossils: Shale with plant fossilsSandstone: SandstoneConglomerate: ConglomerateSedimentary Rocks : Sedimentary Rocks Classifying sedimentary rocks Two groups based on the source of the material Chemical rocks Derived from material that was once in solution and precipitates to form sediment Directly precipitated as the result of physical processes, or Through life processes (biochemical origin) Sedimentary Rocks : Sedimentary Rocks Classifying sedimentary rocks Two groups based on the source of the material Chemical rocks Common sedimentary rocks Limestone – the most abundant chemical rock Microcrystalline quartz (precipitated quartz) known as chert, flint, jasper, or agate Evaporites such as rock salt or gypsum CoalFossiliferous limestone: Fossiliferous limestoneRock Salt: Rock Salt You do not have the permission to view this presentation. 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