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)]]