Marl 46196 212461572 2008-05-14T22:16:29Z Jo Weber 5754437 [[WP:UNDO|Undid]] revision 212282961 by [[Special:Contributions/71.249.50.183|71.249.50.183]] ([[User talk:71.249.50.183|talk]]) {{dablink|For other uses see [[Marl (disambiguation)]].}} [[Image:Mineraly.sk - slien.jpg|right|thumb|A sample of marlstone]] '''Marl''' or '''Marlstone''' is a [[calcium carbonate]] or ''lime''-rich mud or [[mudstone]] which contains variable amounts of [[clay]]s and [[aragonite]]. Marl is originally an old term 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, formed under freshwater conditions; specifically an earthy substance containing 35-65% clay and 65-35% carbonate<ref>Sedimentary Rocks. Pettijohn, F. J., Harper& Brothers New York 1957, p. 410</ref>. The term is today often used to describe indurated marine deposits and [[lacustrine]] (lake) [[sediment]]s which more accurately should be named [[marlstone]]s. Marlstone is an indurated rock of about the same composition as marl, more correctly called an earthy or impure [[argillaceous minerals|argillaceous limestone]]. It has a blocky subconchoidal fracture, and is less fissile than shale. The term ''marl'' is widely used in English-language geology, while the terms ''Mergel'' and ''Seekreide'' (German for "sea chalk") are used in European references. The lower [[stratigraphy|stratigraphic]] units of the [[chalk]] [[White cliffs of Dover|cliffs of Dover]] consist of a sequence of [[glauconite|glauconitic]] marls followed by rhythmically-banded [[limestone]] and marl layers. Similar upper [[Cretaceous]] cyclic sequences in [[Germany]] have been correlated with [[Milankovitch cycle|Milankovitch]] orbital forcing. Marl as lacustrine sediment is common in post-[[glacial lake]] bed sediments, often found underlying [[peat bogs]]. It has been utilized as a soil conditioner and acid soil neutralizing agent. It is a soft, loose, earthy, material that consists of varying amounts of calcium carbonate, clay, and silt size material and is formed primarily in freshwater conditions (Hubbard and Herman, 1990). ==References== * Schurrenberger, D., Russell, J. and Kerry Kelts. 2003. ''Classification of lacustrine sediments based on sedimentary components.'' Journal of Paleolimnology 29: 141-154. * [http://www.geologyshop.co.uk/chalk1.htm Chalk of Kent by C. S. Harris] Accessed 11/06/2005 * [http://geolmag.geoscienceworld.org/cgi/content/abstract/142/1/31 Geochemistry and time-series analyses of orbitally forced Upper Cretaceous marl–limestone rhythmites, abstract] Accessed 11/06/2005 * [http://www.the-conference.com/JConfAbs/5/782.pdf Palaeoenvironmental Interpretation of the Early Postglacial Sedimentary Record of a Marl Lake] Accessed 11/06/2005 {{Reflist}} ==See also== {{wiktionarypar|marl}} * [[Agricultural lime]] [[Category:Limestone]] [[Category:Sedimentary rocks]] [[an:Salagón]] [[ca:Marga]] [[cs:Slín]] [[da:Mergel]] [[de:Mergel]] [[et:Mergel]] [[es:Marga]] [[eo:Marno]] [[eu:Tupa]] [[fr:Marne (roche)]] [[io:Marno]] [[it:Marna (roccia)]] [[he:חוואר]] [[lt:Mergelis]] [[li:Mergel]] [[hu:Márga]] [[nl:Mergel]] [[pl:Margiel]] [[pt:Marga]] [[ru:Мергель]] [[sk:Slieň]] [[tr:Marn]] [[uk:Мергель]] [[wa:Måle (tere)]]