| Sedimentary particle rock |
A rock fragment, in sedimentary geology, is a sand-sized particle or sand grain that is made up of multiple grains that are connected on the grain scale. These can include grains which are sand-sized themselves (a granitic rock fragment), or finer-grained materials (shale fragments). [1] This definition is used for QFR ternary diagrams, provenance analysis, and in the Folk classification scheme, mainly in sandstones.
Sandstone is a clastic sedimentary rock composed mainly of sand-sized silicate grains. Sandstones make up about 20 to 25 percent of all sedimentary rocks.
Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at the Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles to settle in place. The particles that form a sedimentary rock are called sediment, and may be composed of geological detritus (minerals) or biological detritus. The geological detritus originated from weathering and erosion of existing rocks, or from the solidification of molten lava blobs erupted by volcanoes. The geological detritus is transported to the place of deposition by water, wind, ice or mass movement, which are called agents of denudation. Biological detritus was formed by bodies and parts of dead aquatic organisms, as well as their fecal mass, suspended in water and slowly piling up on the floor of water bodies. Sedimentation may also occur as dissolved minerals precipitate from water solution.
The lithology of a rock unit is a description of its physical characteristics visible at outcrop, in hand or core samples, or with low magnification microscopy. Physical characteristics include colour, texture, grain size, and composition. Lithology may refer to either a detailed description of these characteristics, or a summary of the gross physical character of a rock. Examples of lithologies in the second sense include sandstone, slate, basalt, or limestone.
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.
Conglomerate is a clastic sedimentary rock that is composed of a substantial fraction of rounded to subangular gravel-size clasts. A conglomerate typically contain a matrix of finer grained sediments, such as sand, silt, or clay, which fills the interstices between the clasts. The clasts and matrix are typically cemented by calcium carbonate, iron oxide, silica, or hardened clay.
Greywacke or graywacke is a variety of sandstone generally characterized by its hardness, dark color, and poorly sorted angular grains of quartz, feldspar, and small rock fragments or lithic fragments set in a compact, clay-fine matrix. It is a texturally immature sedimentary rock generally found in Paleozoic strata. The larger grains can be sand- to gravel-sized, and matrix materials generally constitute more than 15% of the rock by volume. The term "greywacke" can be confusing, since it can refer to either the immature aspect of the rock or its fine-grained (clay) component.
Arkose is a detrital sedimentary rock, specifically a type of sandstone containing at least 25% feldspar. Arkosic sand is sand that is similarly rich in feldspar, and thus the potential precursor of arkose.
Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from shale by its lack of fissility.
A quartz arenite or quartzarenite is a sandstone composed of greater than 90% detrital quartz, with limited amounts of other framework grains and matrix. It can have higher-than-average amounts of resistant grains, like chert and minerals in the ZTR index.
Arenite is a sedimentary clastic rock with sand grain size between 0.0625 mm (0.00246 in) and 2 mm (0.08 in) and contain less than 15% matrix. The related adjective is arenaceous. The equivalent Greek-derived term is psammite, though this is more commonly used for metamorphosed sediments.
The Folk classification is a technical descriptive classification of sedimentary rocks devised by Robert L. Folk, an influential sedimentary petrologist and Professor Emeritus at the University of Texas.
Clastic rocks are composed of fragments, or clasts, of pre-existing minerals and rock. A clast is a fragment of geological detritus, chunks and smaller grains of rock broken off other rocks by physical weathering. Geologists use the term clastic with reference to sedimentary rocks as well as to particles in sediment transport whether in suspension or as bed load, and in sediment deposits.
Lithic may refer to:
Calcarenite is a type of limestone that is composed predominantly, more than 50 percent, of detrital (transported) sand-size, carbonate grains. The grains consist of sand-size grains of either corals, shells, ooids, intraclasts, pellets, fragments of older limestones and dolomites, other carbonate grains, or some combination of these. Calcarenite is the carbonate equivalent of a sandstone. The term calcarenite was originally proposed in 1903 by Grabau as a part of his calcilutite, calcarenite and calcirudite carbonate classification system based upon the size of the detrital grains composing a limestone. Calcarenites can accumulate in a wide variety of marine and non-marine environments. They can consist of grains of carbonate that have accumulated either as coastal sand dunes (eolianites), beaches, offshore bars and shoals, turbidites, or other depositional settings.
This glossary of geology is a list of definitions of terms and concepts relevant to geology, its sub-disciplines, and related fields. For other terms related to the Earth sciences, see Glossary of geography terms.
Cementation involves ions carried in groundwater chemically precipitating to form new crystalline material between sedimentary grains. The new pore-filling minerals forms "bridges" between original sediment grains, thereby binding them together. In this way sand becomes "sandstone", and gravel becomes "conglomerate" or "breccia". Cementation occurs as part of the diagenesis or lithification of sediments. Cementation occurs primarily below the water table regardless of sedimentary grain sizes present. Large volumes of pore water must pass through sediment pores for new mineral cements to crystallize and so millions of years are generally required to complete the cementation process. Common mineral cements include calcite, quartz or silica phases like cristobalite, iron oxides, and clay minerals, but other mineral cements also occur.
Lithic fragments, or lithics, are pieces of other rocks that have been eroded down to sand size and now are sand grains in a sedimentary rock. They were first described and named by Bill Dickinson in 1970. Lithic fragments can be derived from sedimentary, igneous or metamorphic rocks. A lithic fragment is defined using the Gazzi-Dickinson point-counting method and being in the sand-size fraction. Sand grains in sedimentary rocks that are fragments of larger rocks that are not identified using the Gazzi-Dickinson method are usually called rock fragments instead of lithic fragments. Sandstones rich in lithic fragments are called lithic sandstones.
The Gazzi-Dickinson method is a point-counting technique used in geology to statistically measure the components of a sedimentary rock, chiefly sandstone. The main focus part of the technique is counting all sand-sized components as separate grains, regardless of what they are connected to. Gazzi-Dickinson point counting is used in the creation of ternary diagrams, such as QFL diagrams.
The geology of Bosnia & Herzegovina is the study of rocks, minerals, water, landforms and geologic history in the country. The oldest rocks exposed at or near the surface date to the Paleozoic and the Precambrian geologic history of the region remains poorly understood. Complex assemblages of flysch, ophiolite, mélange and igneous plutons together with thick sedimentary units are a defining characteristic of the Dinaric Alps, also known as the Dinaride Mountains, which dominate much of the country's landscape.
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