Sedimentary rocks

Coal is a combustible black or brownish-black sedimentary rock, formed as layers called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. It is a fossil fuel, formed when plants decay into peat which is converted into coal by the heat and pressure of deep burial over millions of years. Vast deposits formed from wetlands called coal forests that covered much of the tropics during the late Carboniferous and early Permian.

right|thumb|A piece of flint long, weighing 171 grams

Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, drywall and blackboard or sidewalk chalk. Gypsum also crystallizes as translucent crystals of selenite. It forms as an evaporite mineral and as a hydration product of anhydrite. The Mohs scale of mineral hardness defines gypsum as hardness value 2 based on scratch hardness comparison.

rock formed by the deposition of material

thumb|Reddish-brown bauxite thumb|Bauxite with Penny (United States coin)|US penny for comparison thumb|QEMSCAN mineral maps of bauxite ore-forming [[pisoliths]]

carbonate mineral – CaMg(CO₃)₂

a rock that is composed of smaller rounded rocks cemented together

alt=|thumb|Marl thumb|Scala dei Turchi coastal marl formation, southern [[Sicily]]

thumb|Loess in Vicksburg, Mississippi, United States

organic-rich fine-grained sedimentary rock containing kerogen

often greasy, shiny, combustible organic sedimentary rock that consists of more than 75 per cent carbon by weight

Sedimentology encompasses the study of modern sediments such as sand, silt, and clay, and the processes that result in their formation (erosion and weathering), transport, deposition and diagenesis. Sedimentologists apply their understanding of modern processes to interpret geologic history through observations of sedimentary rocks and sedimentary structures. Sedimentology is a subdiscipline of geology.

thumb|Fossilized stromatolite in Strelley Pool [[chert, about 3.4 billion years old, from Pilbara Craton, Western Australia]] thumb|Modern stromatolites in Shark Bay, Western Australia|Shark Bay, Western Australia

sheet of rock formed in a fracture in a pre-existing rock body

Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility.

thumb|A cobble (geology)|cobble encrusted with [[halite precipitated from the Dead Sea, Israel (with Israeli ₪1 coin [diameter 18mm] for scale)]]

thumb|Eolianite carbonate facies (Holocene) on [[Long Island, Bahamas]]

thumb|upright=1.02|Steeply-tilted layers of flysch on the coast of Bay of Biscay, at [[Zumaia, Basque Country, Spain]] Flysch () is a sequence of sedimentary rock layers that progress from deep-water and turbidity flow deposits to shallow-water shales and sandstones. It is deposited when a deep basin forms rapidly on the continental side of a mountain building episode. Examples are found near the North American Cordillera, the Alps, the Pyrenees and the Carpathians.

thumb|right|Closeup of glacial till. Note that the larger grains (pebbles and gravel) in the till are completely surrounded by the matrix of finer material (silt and sand), and this characteristic, known as matrix support, is diagnostic of till. thumb|right|Glacial till with tufts of grass thumb|Till after avalanche, Norway Till, or glacial till, is unsorted glacial sediment.

thumb|Peloidal phosphorite, Phosphoria Formation, Simplot Mine, Idaho. 4.6 cm wide. thumb|Fossiliferous peloidal phosphorite, (4.7 cm across), Yunnan, [[China. ]] Phosphorite, phosphate rock or rock phosphate is a non-detrital sedimentary rock that contains high amounts of phosphate minerals. The phosphate content of phosphorite (or grade of phosphate rock) varies greatly, from 4% to 20% phosphorus pentoxide (P2O5). Marketed phosphate rock is enriched ("beneficiated") to at least 28%, often more than 30% P2O5. This occurs through washing, screening, deliming, magnetic separation or flotation.

thumb|Concretions in Torysh, Western [[Kazakhstan]] thumb|Concretions with lens shape from island in Vltava river, Prague, Czech Republic thumb|Marlstone aggregate concretion, [[Sault Ste. Marie, Michigan, United States]] A concretion is a hard and compact mass formed by the precipitation of mineral cement within the spaces between particles, and is found in sedimentary rock or soil. Concretions are often ovoid or spherical in shape, although irregular shapes also occur. The word concretion is borrowed from Latin , itself derived from concrescere , from con- and crescere .

Arkose () or arkosic sandstone is a detrital sedimentary rock, specifically a type of sandstone containing at least 25% feldspar.

soft diatomite variety

thumb|right|Photomicrographs of feldspathic (L) and lithic (R) greywacke. The top images are in Plane polarized light|plane-polarized light; the bottom images are in [[cross-polarized light. Cements fill the pore spaces.]] thumb|Closeup of Pharaoh Menkaure's greywacke statue, 25th century BCE, from the [[Egyptian Museum in Cairo]]

thumb|Grey chunks of Graptolite|graptolitic argillite on [[Pakri Peninsula, Estonia; yellowish and white chunks are limestone]] Argillite () is a fine-grained sedimentary rock composed predominantly of indurated clay particles. Argillaceous rocks are basically lithified muds and oozes. They contain variable amounts of silt-sized particles. The argillites grade into shale when the fissile layering typical of shale is developed. Another name for poorly lithified argillites is mudstone. These rocks, although variable in composition, are typically high in aluminium and silica with variable alkali

thumb|upright=1.35|Pleistocene glacial lake varves at Sandend Bay in Scotland A varve is an annual layer of sediment or sedimentary rock.

thumb|Modern ooids from a beach on Joulter Cays, The Bahamas, with 0.5 mm scale thumb|right|Ooids on the surface of a limestone; Carmel Formation (Middle Jurassic) of southern Utah thumb|right|Thin-section of calcitic ooids from an oolite within the Carmel Formation (Middle [[Jurassic) of southern Utah]]

Chert () is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide (SiO2). Chert is characteristically of biological origin, but may also occur inorganically as a chemical precipitate or a diagenetic replacement, as in petrified wood. Where chert occurs in chalk or marl, it is usually called flint.

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Lithification (from the Ancient Greek word lithos meaning 'rock' and the Latin-derived suffix -ific) is the process in which sediments compact under pressure, expel connate fluids, and gradually become solid rock. Essentially, lithification is a process of porosity destruction through compaction and cementation. Lithification includes all the processes which convert unconsolidated sediments into sedimentary rocks. Petrifaction, though often used as a synonym, is more specifically used to describe the replacement of organic material by silica in the formation of fossils.

diameter of individual grains of sediment, or of lithified particles in clastic rocks

thumb|An example of impactite on Earth (from Monturaqui impact crater, Chile) Impactite is rock created or modified by one or more impacts of a meteorite. Impactites are considered metamorphic rock, because their source materials were modified by the heat and pressure of the impact. On Earth, impactites consist primarily of modified terrestrial material, sometimes with pieces of the original meteorite.

distinctive layered units of iron-rich sedimentary rock that are almost always of Precambrian age

thumb|upright=1.25|petrified wood|Tree remains that have undergone petrifaction, as seen in [[Petrified Forest National Park]]

thumb|Turbidites are deposited in the deep ocean troughs below the continental shelf, or similar structures in deep lakes, by underwater avalanches which slide down the steep slopes of the continental shelf edge. When the material comes to rest in the ocean trough, it is the sand and other coarse material which settles first followed by mud and eventually the very fine particulate matter. It is this sequence of deposition that creates the Bouma sequences that characterize these rocks.

thumb|Pisoids in the Conococheague limestone (Upper Cambrian) of eastern Pennsylvania thumb|right|Pisolitic limestone; Itaboraí, Rio de Janeiro, Brazil; pisolith diameters average 1.0 cm thumb|right|QEMSCAN mineral map of bauxite forming pisoids

sediment from marine waters

thumb|Sylvinite from Perm Krai, Russia thumb|Close-up view of sylvinite from Perm, Russia Sylvinite is a sedimentary rock made of a mechanical mixture of the minerals sylvite (KCl, or potassium chloride) and halite (NaCl, or sodium chloride). Sylvinite is the most important source for the production of potash in North America, Russia and the UK. Most Canadian operations mine sylvinite with proportions of approximately 31% KCl and 66% NaCl with the balance being insoluble clays, anhydrite and in some locations carnallite. Other deposits of sylvinite are located in Belarus, Brazil, France, Germa

class of sedimentary rock

thumb|Modern ooids from a beach on Joulter Cays, The Bahamas. thumb|Ooids on the surface of limestone; Carmel Formation (Middle [[Jurassic) of southern Utah, USA.]] thumb|A thin slice of calcitic ooids from the Carmel Formation, Middle Jurassic, of southern Utah, USA.

thumb|Outcrop of Franciscan Assemblage|Franciscan radiolarian chert in [[San Francisco, California ]] thumb|Radiolarian chert outcrop near Cambria, California. Individual beds range from about 2 to 5 cm thick thumb|Radiolarite (Jurassic) from the [[Alps.]] Radiolarite is a siliceous, comparatively hard, fine-grained, chert-like, and homogeneous sedimentary rock that is composed predominantly of the microscopic remains of radiolarians. This term is also used for indurated radiolarian oozes and sometimes as a synonym of radiolarian earth. However, radiolarian earth is typically regarded by Earth

range of stepped travertine terraces and springs in Sari County, Iran

300px|thumb|right|The Salt Cellar, a gritstone Tor (rock formation)|tor on [[Derwent Edge in the Peak District, England]]

sediments derived from the erosion of rocks on land

In geology, cross-bedding, also known as cross-stratification, is layering within a stratum and at an angle to the main bedding plane. The sedimentary structures which result are roughly horizontal units composed of inclined layers. The original depositional layering is tilted, such tilting not being the result of post-depositional deformation. Cross-beds or "sets" are the groups of inclined layers, which are known as cross-strata.

fine-grained sediment that accumulates on the floor of the open ocean

upright=1.35|thumb|right|Stylolites in limestone

Psephite (Greek: psephos, "pebble") is either a sediment or sedimentary rock composed of fragments that are coarser than sand and which are enclosed in a matrix that varies in kind and amount. It is equivalent to a rudite. Shingle, gravel, breccia, and especially conglomerate, would all be considered psephites. It is equivalent to the Latin-derived term rudite. Psephite is more commonly used for a metamorphosed rudite.

thumb | right Psammite (Greek: psammitēs "(made) from sand", from psammos "sand") is a general term for sandstone. It is equivalent to the Latin-derived term arenite and is commonly used in various publications to describe a metamorphosed sedimentary rock with a dominantly sandstone protolith. In Europe, this term was formerly used for a fine-grained, fissile, clayey sandstone. Pettijohn gives the following descriptive terms based on grain size, avoiding the use of terms such as "clay" or "argillaceous", which carry an implication of chemical composition:

thumb|The melting of plastic waste from campfires or high temperatures on beaches (1) is resulting in the formation of a new type of rock known as plastiglomerate (2). Formed plastiglomerate merges with surrounding sediment to create a compositionally different sediment layer (3).The emergence of this new layer is being used as physical evidence of a marker horizon for an Anthropocene Epoch (4). Plastiglomerate is a rock made of a mixture of sedimentary grains, and other natural debris (e.g. shells, wood) that is held together by plastic. It has been considered a potential marker of the Anthro

knot, mass, or lump of a mineral or mineral aggregate with a contrasting composition

thumb|Geyserite from Iceland

thumb|Oncolites from the upper Burgsvik beds (Silurian), with shell fragments as nuclei. The large flower is 2 cm in diameter. thumb|Oncolites formed around the Middle Jurassic [[gastropod Bactroptyxis trachaea (Normandy, France).]] Oncolites are sedimentary structures composed of oncoids, which are layered structures formed by the growth of one or more species of microorganisms, usually containing cyanobacteria. Oncolites are very similar to stromatolites, but, instead of forming columns, they form approximately spherical structures. The oncoids often form around a central nucleus, such

Taconite () is a variety of banded iron formation, an iron-bearing (over 15% iron) sedimentary rock, in which the iron minerals are interlayered with quartz, chert, or carbonate. The name taconyte was coined in the 19th century by Horace Vaughn Winchell – son of Newton Horace Winchell, the Minnesota state geologist – during their pioneering investigations of the Precambrian Biwabik Iron Formation of northeastern Minnesota within the Mesabi Range. He believed the sedimentary rock sequence hosting the iron-formation was correlative with the Taconic orogeny of New England and referred to the unfa

thumb|Roadside cross-section of a large olistolith in the ophiolithic melange, Vardar|Western Vardar Ophiolithic Unit of [[Serbia]]

colorful conglomerate rock

thumb|A photograph of a slab of Itacolumite Itacolumite is a naturally occurring sandstone that is flexible when cut into relatively thin slabs. It occurs at Itacolomi, its eponym, in the southern portion of Minas Gerais, Brazil. The stone is porous, and often yellow in color. It is also found in Kaliana village (Charkhi Dadri district, Haryana, India), the U.S. state of Georgia, and Stokes and McDowell counties of North Carolina. It is the best and most widely known example of a flexible sandstone, and is a source of diamonds found in the Minas Gerais area of Brazil.

thumb|Arenite

thumb|Peperite at Puy de Crouel in Auvergne, France thumb|Peperite from Cumbria, England. This example was formed during the [[Ordovician Period and it is of andesitic composition.]] A peperite is a type of volcaniclastic rock consisting of sedimentary rock that contains fragments of younger igneous material and is formed when magma comes into contact with wet sediments. The term was originally used to describe rocks from the Limagne region of France, from the similarity in appearance of the granules of dark basalt in the light-coloured limestone to black pepper. Typically the igneous fragment

classification system for carbonate sedimentary rocks