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Mudstone. 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 (parallel layering). [1][2] The term mudstone is also used to describe carbonate rocks (limestone or dolomite) that are composed predominantly of carbonate mud. [3]
A mudstone is a siliciclastic sedimentary rock that contains a mixture of silt- and clay-sized particles (at least 1/3 of each). [4] The terminology of "mudstone" is not to be confused with the Dunham classification scheme for limestones. In Dunham's classification, a mudstone is any limestone containing less than ten percent carbonate grains.
Argillite ( / ˈɑːrdʒɪlaɪt /) 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.
Thin section photomicrograph of a carbonate mudstone in plane polarised light. The Dunham classification system for carbonate sedimentary rocks was originally devised by Robert J. Dunham (1924–1994) [1] in 1962, [2] and subsequently modified by Embry and Klovan in 1971 [3] to include coarse-grained limestones and sediments that had been ...
The term was earlier used by geologists to describe a clay-rich, fine-grained clastic sediment or sedimentary rock, i.e. mud or a mudstone, the metamorphosed version of which would technically have been a metapelite. It was equivalent to the now little-used Latin -derived term lutite. [4][5][6] A semipelite is defined in part as having similar ...
Marl or marlstone is a carbonate -rich mud or mudstone which contains variable amounts of clays and silt. The term was originally loosely applied to a variety of materials, most of which occur as loose, earthy deposits consisting chiefly of an intimate mixture of clay and calcium carbonate, [1] formed under freshwater conditions.
In clastic sedimentary rocks, grain size is the diameter of the grains and/or clasts that constitute the rock. These are used to determine which rock naming system to use (e.g., a conglomerate , sandstone , or mudstone ).
One definition is that siltstone is mudrock (clastic sedimentary rock containing at least 50% clay and silt) in which at least 2/3 of the clay and silt fraction is composed of silt-sized particles. Silt is defined as grains 2–62 μm in diameter, or 4 to 8 on the Krumbein phi (φ) scale. [7] An alternate definition is that siltstone is any ...