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| Sedimentary rocks | |
|---|---|
| Name | Sedimentary rocks |
| Type | Rock |
| Composition | Clastic, chemical, organic |
| Formation | Weathering, erosion, deposition, lithification |
Sedimentary rocks are a class of rocks formed by the accumulation and consolidation of sediments derived from the erosion and alteration of preexisting materials. They record surface processes and environments across geologic time and host important reservoirs of natural resources, archives of past climates, and stratigraphic markers used in regional and global correlations. Sedimentary successions are central to studies that involve field investigations, mapping, and basin analysis conducted by institutions and researchers worldwide.
Sedimentary accumulations develop in settings studied by practitioners affiliated with United States Geological Survey, British Geological Survey, Geological Society of America, International Union of Geological Sciences, and university departments at Harvard University, University of Cambridge, Stanford University, University of Oxford, and ETH Zurich. Prominent field areas include the Grand Canyon, Burgess Shale, Navajo Sandstone, Karoo Basin, and Morrison Formation, which have informed models advanced by scientists from the Smithsonian Institution and the National Oceanic and Atmospheric Administration. Research on layered deposits often integrates methods developed at laboratories such as the Max Planck Society and instruments deployed on projects by NASA and the European Space Agency.
Standard classification schemes distinguish clastic, chemical, and organic varieties, a taxonomy used by the International Commission on Stratigraphy and outlined in textbooks from presses like Cambridge University Press and Springer. Clastic types include conglomerate, breccia, sandstone, siltstone, and shale, categories applied in regional studies of the Appalachian Mountains, Himalayas, Andes, and Rocky Mountains. Chemical types include evaporites (halite, gypsum) found in basins such as the Dead Sea and Great Salt Lake and carbonate rocks (limestone, dolostone) prevalent in platforms like the Bahamas Banks and Permian Basin. Organic types include coal and hydrocarbon-bearing mudstones documented in provinces such as the Powder River Basin and North Sea Basin.
Sediment production begins with weathering and erosion processes documented in landscapes like the Sierra Nevada, Alps, and Atlas Mountains, transported by rivers such as the Amazon River, Mississippi River, Yangtze River, and deposited in environments including deltas (example: Nile Delta), continental shelves (e.g., Atlantic Ocean margins), deep marine basins (e.g., Mariana Trench settings), lacustrine basins (e.g., Lake Baikal), and aeolian dune fields (e.g., Sahara Desert). Fluvial, glacial, tidal, and turbidity current processes studied in associations with projects from the United States Army Corps of Engineers and the International Union for Quaternary Research create diagnostic stratification and facies tracts used in basin modeling by firms such as Schlumberger and Halliburton.
Recognized structures include bedding, cross-bedding, ripple marks, graded bedding, mud cracks, bioturbation, and sole marks, features described from classic localities like the Chesapeake Bay, White Cliffs of Dover, and the Bonneville Salt Flats. Textural parameters—grain size, sorting, roundness, and fabric—are measured with standards from organizations such as the American Society for Testing and Materials and applied in provenance studies using methods developed at institutions including the California Institute of Technology and ETH Zurich. Fossil assemblages preserved in units like the Burgess Shale and Green River Formation provide biostratigraphic control used by the Paleontological Society and the Society for Sedimentary Geology.
Diagenetic alteration—compaction, cementation, recrystallization, authigenesis, and mineral replacement—is studied in cores from wells drilled by energy companies including ExxonMobil, BP, and Chevron and in academic drilling programs such as the Integrated Ocean Drilling Program and the International Continental Scientific Drilling Program. Diagenetic pathways influence porosity and permeability relevant to reservoirs in plays like the Permian Basin and the Gulf of Mexico and are constrained using analytical facilities at Lawrence Berkeley National Laboratory and Oak Ridge National Laboratory.
Sedimentary sequences host resources exploited by industries and regulated by laws and agencies such as the U.S. Environmental Protection Agency and the European Commission. They contain petroleum and natural gas in reservoirs of the North Sea, Gulf of Mexico, and Persian Gulf, coal seams in the Appalachian Basin and South Wales Coalfield, evaporites and industrial minerals in the Dead Sea region and Salar de Uyuni, and groundwater aquifers tapped across regions including the Central Valley (California) and Great Artesian Basin. Building stones, cement feedstocks, and aggregate are quarried from formations like the Portland Stone and Bath Stone and processed by companies such as LafargeHolcim.
Sedimentary rocks form stratigraphic archives preserved in basins from cratons like the Canadian Shield to orogenic forelands such as the Andean Foreland Basin. They record major Earth history events including the Cambrian explosion, mass extinctions noted at boundaries like the Cretaceous–Paleogene boundary, and transgressive–regressive cycles tied to paleoclimate studies involving researchers at Woods Hole Oceanographic Institution and Scripps Institution of Oceanography. Correlation frameworks developed by the International Commission on Stratigraphy and chronostratigraphic charts integrate sedimentary records with radiometric constraints from laboratories such as Argonne National Laboratory.
Category:Sedimentary geology