#sediment

• Ammonite — A fossil marine cephalopod mollusk from the Ammonoidea subclass, characterized by an external, planospiral, and chambered calcareous shell, which lived from the Devonian period until the end of the Cretaceous. The fossils of these organisms are widely used in stratigraphical geology as index fossils for the precise dating of sedimentary rock layers from the Mesozoic era.
• Anadiagenesis — An intermediate or deep stage within the general process of diagenesis, characterized by intense structural physicochemical transformations of sediments buried at great depths under increased temperatures and pressures, without reaching metamorphism. This phenomenon involves the recrystallization of clay minerals, massive compaction, deep dehydration, and cementation of interstitial fluids, leading to the definitive lithification of sedimentary rocks.
• Anchimetamorphism — A geological process of incipient, very low-grade metamorphism that marks the transition between diagenesis (sediment consolidation) and regional metamorphism proper (greenschist facies); it occurs at relatively low temperatures and pressures, causing partial recrystallization of clay minerals without completely destroying the original sedimentary structures.
• Anemoclastics — Clastic rocks, mineral fragments, or sedimentary deposits fragmented, crushed, and structurally shaped by the mechanical action of erosion, abrasion, or transport carried out by the wind (aeolian processes). As an adjective, it describes geological structures or debris formed via wind deflation and corrasion.
• Anemogenous — Produced, generated, shaped, or structurally determined by the action of wind or air currents (such as aeolian landforms or surface sea waves). In rare or adapted medical imaging contexts, it can describe dynamic acoustic phenomena simulating air-like fluid turbulences.
• Anisian — A geological stage or substage located at the base of the Middle Triassic epoch, chronologically spanning from approximately 247 to 242 million years ago. As an adjective, the term refers to rocks, sediments, or fossils formed during this time interval, internationally defined by the appearance of specific ammonite and conodont assemblages within reference Alpine geological sections.
• Ankerite — A mineral from the carbonate class, with a crystalline structure similar to that of dolomite, consisting of a calcium, magnesium, iron, and manganese carbonate. This structural mineral is frequently found in metamorphosed sedimentary rocks, in hydrothermal veins, and in association with iron ores, presenting shades from yellowish-white to reddish-brown due to the oxidation of iron exposed to air.
• Antholite — A mineral formation or underground sedimentary concretion, formed through the gradual precipitation and accumulation of mineral salts within specific karst cavities or geological layers. This structural crystalline aggregate often develops in the form of stalactites or branched crusts, having a chemical composition dictated by the cave's microclimate and the purity of hydrothermal solutions circulating through the rock mass.
• Anthracolitic — Belonging to, referring to, or specific to anthracolite or the geological period of formation of massive superior coal deposits combined with calcareous structures; a sedimentary rock or crystalline formation characterized by intercalations of calcium carbonate and organic fossil inclusions rich in fixed carbon. In a stratigraphic sense, it describes structural elements or petrographic layers that preserve physical and chemical properties from the Paleozoic era.
• Antras — An archaic or regional technical term used to describe an inferior variety of friable bituminous coal or fine coal dust sedimented in old extraction galleries, featuring a high content of mineral impurities and ash. In petrography, it can refer to microscopic fragments of carbonized organic matter dispersed in argillaceous sedimentary rocks, used as indicators of thermal metamorphism grade.
• Anthropolit — A fossilized human remain or a human body petrified through incrustation with mineral substances (lime, silica) inside cave sediments or ancient geological layers. This rare technical term is used in fossil studies to denote prehistoric skeletal specimens that have undergone a complete process of diagenesis and structural mineralization.
• Aptian — An upper geological stage of the Lower Cretaceous, chronologically situated between the Barremian and the Albian, structurally characterized by massive sedimentary deposits rich in ammonites and the expansion of specific marine faunas; as an adjective, it describes the rocks, formations, or fossils that formed during this period of Earth's history.
• Arkose — A coarse-grained detrital sedimentary rock, similar to sandstone, structurally formed by the disintegration of granite or other plutonic rocks and composed of a high percentage of feldspar (over 25%) alongside quartz and mica. Geologically, the presence of arkose in a terrestrial stratum indicates rapid mechanical weathering and short-distance transport in an arid or semi-arid climate, where chemical alteration was minimized.
• Arenaceous — Having the nature, appearance, or composition of sand; rich in sand grains or structurally formed from fine detrital quartz deposits. In a geological and mineralogical sense, it describes sedimentary rocks (such as sandstones or fine conglomerates) or soils whose primary textural matrix features a sandy granulometry according to lithological classification standards.
• Sand expanse — An extensive accumulation of sand, a sandy beach, or a desert area covered with dunes; an unconsolidated granular sedimentary deposit formed by rock disintegration under climatic actions. In an international geographical and tourism context (originating from Spanish), the term designates coastal regions, seaside resorts, or volcanic areas structurally characterized by the massive presence of sand fields or fine volcanic ash.
• Arenarie — An extremely rare term or obsolete variant previously used in sedimentology to designate a consolidated detrital sedimentary rock formed from cemented sand grains, currently known as sandstone. Its structural meaning stems from the Latin root relating to sand, indicating the coarse granulometric composition of the rock.
• Areniferous — Containing or producing sand; a rock, geological stratum, or detrital sedimentary deposit rich in silica grains or fine quartz. In a structural sense, it describes a lithological formation or terrestrial matrix built through massive clastic and sedimentary accumulations over geological eras, directly influencing the porosity and permeability of underlying aquifer layers.
• Arenite — A clastic or detrital sedimentary rock composed of medium-grained mineral particles, with diameters structurally ranging from 0.0625 to 2 millimeters (sand-sized particles), cemented within a fine matrix. Unlike wacke, an arenite contains less than 15% interstitial clay matrix, being strictly classified based on grain composition into quartz, feldspathic, or lithic arenite.
• Arenogenesis — The structural geological process of sand formation and accumulation through the mechanical disintegration, chemical weathering, and erosion of preexisting rocks (especially those rich in quartz, such as granite), followed by the transport and deposition of granular particles by external agents (wind, water, waves). Arenogenesis represents a fundamental stage in the lithogenetic cycle, determining the creation of detrital deposits that, through subsequent diagenesis, can structurally evolve into sandstones or other psammitic sedimentary rocks.
• Arenogenic — Generating, producing, or favoring the formation of sand or sandy detrital deposits; relating to geological or morphological processes that lead to the fragmentation of siliceous rocks and the accumulation of quartz grains. In a structural-geological sense, an arenogenic factor directly determines the sedimentary dynamics of continental or coastal basins, influencing the granulometry of forming clastic layers.