Editing Marl (section)

==Description==

[[Image:Marl vs clay & lime EN.PNG|300px|right|thumb|Scheme of the transitional lithotypes from mud (or mudstone) to lime (or limestone), illustrating the definition of marl (marlstone) as a mix of calcium carbonate and clay]]

Marl or marlstone is  a [[carbonate mineral|carbonate]]-rich mud or [[mudstone]] which contains variable amounts of [[Clay minerals|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]],{{sfn|Boggs|2006|p=172}} formed under freshwater conditions. These typically contain 35–65% clay and 65–35% carbonate.{{sfnp|Pettijohn|1957|pp=368–369}}{{sfn|Blatt|Tracy|1996|p=217}} The term is today often used to describe [[Friability|indurated]] marine deposits and [[Lake|lacustrine]] (lake) [[sediment]]s which are more accurately named 'marlstone'.{{sfnp|Pettijohn|1957|pp=410–411}}

Marlstone is an indurated (resists crumbling or powdering) rock of about the same composition as marl. This is more correctly described as an earthy or impure [[argillaceous minerals|argillaceous]] [[limestone]]. It has a blocky [[conchoidal|subconchoidal]] fracture, and is less [[Fissility (geology)|fissile]] than [[shale]].{{sfnp|Pettijohn|1957|pp=410–411}}  The dominant carbonate mineral in most marls is [[calcite]], but other carbonate minerals such as [[aragonite]] or [[Dolomite (mineral)|dolomite]] may be present.{{sfnp|Perri|Dominici|Critelli|2015}}

''Glauconitic marl'' is marl containing pellets of [[glauconite]], a clay mineral that gives the marl a green color.{{sfn|Nourmohamadi |Abdula |Albeyati |Sharezwri |2020|pp=29–38}} Glauconite is characteristic of sediments deposited in marine conditions.{{sfn|Nesse|2000|p=249}}