Chapter+5+-+Sedimentation - Grotzinger • Jordan...

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Unformatted text preview: Grotzinger • Jordan Understanding Earth Sixth Edition Chapter 5: SEDIMENTATION: Rocks Formed by Surface Processes © 2011 by W. H. Freeman and Company Chapter 5 Chapter Sedimentation: Sedimentation: Rocks Formed by Rocks Surface Processes Surface 1. Surface Processes and the Rock Cycle Weathering Physical weathering Chemical weathering 1. Surface Processes and the Rock Cycle Surface Processes forming sedimentary rock: Weathering Erosion Transportation Deposition (sedimentation) Burial and compaction Diagenesis 1. Surface Processes and the Rock Cycle Surface Classification of sediments Siliciclastic sediments Chemical sediments - Biological sediments Biological 1. Surface Processes and the Rock Cycle Surface Current strength and distance of Current transport affect: transport Size of clastic particles Sorting of clastic particles Rounding of clastic particles Thought questions for this chapter Thought A geologist is heard to say that a particular sandstone geologist was derived from a granite. What information could she have gleaned from the sandstone to support this? The presence of quartz + weathering components of the feldspar feldspar Describe the beach sands that you would expect to be Describe produced by the beating of waves on a coastal mountain range consisting largely of basalt. Sands will be dark range 2. Sedimentary Basins 2. Sedimentary Sediments tend to accumulate in Sediments depressions in the Earth’s crust. depressions Sedimentary basins are depressions Sedimentary filled with thick accumulations of sediment. They are sinks for sediment. sediment. Sedimentary Sedimentary Environments 3. Sedimentary Environments 3. Sedimentary Thought questions for this chapter Thought How can you use size and sorting of sediments to How distinguish between sediments deposited in a glacial environment and those deposited in a desert? Desert particles will be smaller and better sorted because wind only transports small particles only Where are reefs likely to be found? Marine lagoon Where environment environment 4. Sedimentary Structures 4. Sedimentary structures – all kinds Sedimentary of features in sediments formed at the time of deposition. the Bedding (stratification) Cross-bedding Graded bedding Ripples Bioturbation structures CrossCrossbedding Example of a Bedding Sequence Example Thought questions for this chapter Thought You are looking at a cross section of rippled sandstone. You What sedimentary structure would tell you the direction of current that deposited the sand? The steeper slope of the ripple is downstream/downwind. ripple 5. Burial and Diagenesis 5. Burial is the preservation of Burial sediments within a sedimentary basin. Diagenesis is the physical and chemical change that converts sediments to sedimentary rocks. sediments Thought questions for this chapter Thought If you drilled one oil well into the bottom of a sedimentary If basin that is 1 km deep and another that is 5 km deep, which would have the higher pressures and temperatures? Oil turns into natural gas at high basin temperatures. In which well would you expect to find more natural gas? more The one that is 5 km deep would have higher T and P due The to geothermal gradient and would contain more natural gas. gas. 6. Classification of Siliciclastic Sediments 6. and Sedimentary Rocks 7. Classification of Chemical and Biological Sediments, Sedimentary Rocks Sedimentary Biological sedimentary rocks Limestone Chert Organics 7. Classification of Chemical and Biological Sediments, Sedimentary rocks Sedimentary Chemical sedimentary rocks Dolostone Iron formation Evaporite Organic Reef Development Organic Thought questions for this chapter Thought What role do organisms play in the origin of some types What of limestone? Their shell formation leads to “bioclastic” sediment formation formation How are chert and limestone similar in origin? Discuss How the roles of biological versus chemical processes. the The precipitation of both tend to be catalyzed by The biological processes..chert by diatoms and limestone by Foraminifera and mollusks. Foraminifera and Key terms and concepts Arkose Arkose Bedding sequence Bioclastic sediment Biological sediment Bioturbation Carbonate rock Carbonate sediment Cementation Chemical sediment Chemical weathering Chert Coal Compaction Key terms and concepts Conglomerate Conglomerate Continental shelf Cross-bedding Diagenesis Dolostone Evaporite rock Evaporite sediment Foraminifera Graded bedding Gravel Iron formation Limestone Key terms and concepts Lithic sandstone Lithic Lithification Natural gas Oil Organic sedimentary rock Peat Physical weathering Porosity Reef Ripple Key terms and concepts Salinity Salinity Sand Sandstone Sedimentary basin Sedimentary environment Sedimentary structure Shale Siliclastic sediments Silt Silt Siltstone Siltstone Sorting ...
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