Lecture 7 - Chapter 7 Sedimentary Rocks What is a...

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Chapter 7  Sedimentary Rocks What is a sedimentary rock? Sedimentary rocks are products of mechanical and chemical weathering Solid material setting out of a fluid (water or air) – is a sedimentary rock They account for about 5% (by volume) of Earth’s outer 10 miles, but make up more than 75% of all rock outcrops The rock layers of sediments contain evidence of past events and environments that occurred at the surface Provide information about sediment transport Often contain fossils Coal, Oil and Gas – are associated with sedimentary rocks ! Sedimentary rocks are important for economic considerations because they may contain Sources of iron, aluminum, and manganese Fertilizer (organic and inorganic) Gravel, Sand and Clay – materials essential to the construction industry and glass production Often form a trap for the heavy and rare metals Turning sediment into sedimentary rock Sedimentation is never-ending process Sediment is found almost EVERYWHERE Many changes occur to sediment after it is deposited Diagenesis = chemical, physical, and biological changes that take place after sediments are deposited Occurs within the upper few kilometers of Earth’s crust at temperatures usually less than 200 o C Diagenesis includes : Recrystallization development of more stable minerals from less stable ones. Aragonite (CaCO3) from shells and corals to calcite (CaCO3) of the limestones (sedimentary rock) Lithification process by which unconsolidated sediments are transformed into solid rock Compaction considerable reduction in pore space between the grains of sediment. Compaction is most significant as a lithification process in fine grained sedimentary rocks (clay, silts) Cementation the precipitation of minerals among the individual sediment grains. It is a chemical process. Natural cements include : calcite, silica, and iron oxide Types of sedimentary rocks : detrital and chemical Sediment - originates from mechanical and/or chemical products of weathering which were transported and deposited (or precipitated) in the bottom of lakes, rivers, seas, oceans etc. Sedimentary rock
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This note was uploaded on 04/26/2009 for the course GEOL 101 taught by Professor Olinsky during the Spring '08 term at Texas A&M.

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Lecture 7 - Chapter 7 Sedimentary Rocks What is a...

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