Sedimentary Rock Classification
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This document provides an overview of sedimentary rocks and the processes involved in their formation. Sedimentary rocks are formed from the deposition of materials at the Earth's surface or within bodies of water. They provide information about past environmental conditions and geological history. The key processes involved in sedimentary rock formation are weathering, erosion, transportation, deposition, and diagenesis, which is the chemical and physical changes that occur after deposition. Sedimentary rocks can be divided into clastic sediments like sandstone, chemical sediments like limestone formed by precipitation from solution, and biochemical sediments like coal formed from organic material.
Sedimentary Rock Classification
- 1. Lecture #1
- 2. studying sediments derive information on the depositional conditions; rock unit relation of the individual rock units in a basin into a coherent understanding of the evolution of the sedimentary sequences and basins Earth's geological history as a whole
- 3. Sedimentary rocks are formed in places where there has been water at one time. Dead animals, plants, and pieces of rocks or minerals are carried to these places by wind, water, ice, or even gravity.
- 4. Rock Process
- 5. Types of rock that are formed by the deposition of material at the Earth's surface and within bodies of water Indicators of geological processes, environment (tectonic event), and geological history. Contain of mineral resources such as coal, petroleum, natural gas, iron, gold, aluminum, uranium, diamond etc.
- 6. Weathering Erosion Transportation Deposition Diagenesis
- 7. All of the chemical, physical and biological changes that take place after sediments are deposited. Occurs within the upper few kilometers of earth’s crust Consist of: Lithification : unconsolidated sediments are transformed into solid sedimentary rocks by compaction and cementation Natural cements include calcite, silica and iron oxide.
- 8. Sediment originates from mechanical and/or chemical weathering. Based on the source of material: i. Detrital (Siliciclastic) sediments: sediment transported as solid particles ii. Chemical Sediments : sediment that was once in solution iii. Biogenic, Biochemical and Organic sediments iv. Volcanoclastic sediments. coal
- 9. The chief constituents of detrital rocks include: Clay minerals Quartz Feldspars Micas Chert Breccia: The angular clasts in this breccia are chert fragments. The matrix is an iron-stained mix of clay through sand-size particles. The specimen is about two inches (five centimeters) across. Particle size is used to distinguish among the various types of detrital rocks.
- 10. Size Range (mm) Particle Name Sediment >256 64-256 4-64 2-4 Boulder Cobble Pebble Granule Gravel 1/16 - 2 Sand Sand 1/256 – 1/16 <1/256 Silt Clay Mud
- 11. Consist of precipitated material that was once in solution Precipitation of material occurs in two ways: Inorganic processes Organic processes (biochemical origin)
- 12. Limestone Most abundant chemical rock Majority composed by mineral calcite Marine biochemical limestone form as coral reefs, coquina (broken shells), and chalk (microscopic organisms) Inorganic limestones include travetine (limestone dissolves in place and is redeposited in another) and oolitic (small rounded particles or grains & look like fish eggs)
- 13. Example for inorganic processes: Chert Made of microcyrstalline quartz Varieties include flint and jasper (banded form is called agate) Evaporites Evaporation triggers deposition of chemical precipitates Ex: rock salt and rock gypsum
- 14. Clastic 60% Chemical Biogenic 50% 60%
- 18. Cross Bedding
- 19. Siliciclastic rocks Chemical rocks Biochemical rocks Boulders Cobbles Oolitic rocks Pebbles Intraclast rocks Granules Sand Dolomite (Dolostone) Silt Clay Micrites Fossilliferous rocks Pelletal rocks Chalk Chert Rock Salt (Halite) Gypsum Peat and Coal Gravel: Breccia / Conglomerate Carbonate Rocks Other chemical Rocks Other Biochemical Rocks
- 26. Rock streaked by oil. Ventura County, CA. USGS photo