Marl is an earthy material rich incarbonate minerals,clays, andsilt. Whenhardened into rock, this becomesmarlstone. It is formed in marine or freshwater environments, often through the activities ofalgae.
Marl makes up the lower part of thecliffs of Dover, and theChannel Tunnel follows these marl layers between France and the United Kingdom. Marl is also a common sediment in post-glacial lakes, such as the marl ponds of the northeastern United States.
Marl has been used as asoil conditioner and neutralizing agent for acid soil and in the manufacture ofcement.
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 acarbonate-rich mud ormudstone which contains variable amounts ofclays andsilt. 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 andcalcium carbonate,[1] formed under freshwater conditions. These typically contain 35–65% clay and 65–35% carbonate.[2][3] The term is today often used to describeindurated marine deposits andlacustrine (lake)sediments which more accurately should be named 'marlstone'.[4]
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 impureargillaceouslimestone. It has a blockysubconchoidal fracture, and is lessfissile thanshale.[4] The dominant carbonate mineral in most marls iscalcite, but other carbonate minerals such asaragonite ordolomite may be present.[5]
Glauconitic marl is marl containing pellets ofglauconite, a clay mineral that gives the marl a green color.[6] Glauconite is characteristic of sediments deposited in marine conditions.[7]
Marl as lacustrine sediment is common in post-glacial lake-bed sediments.[12][13][14]Chara, a macroalga also known as stonewort, thrives in shallow lakes with highpH andalkalinity, where its stems and fruiting bodies become calcified. After the alga dies, the calcified stems and fruiting bodies break down into fine carbonate particles that mingle with silt and clay to produce marl.[15] Marl ponds of the northeastern United States are oftenkettle ponds in areas of limestone bedrock that become poor in nutrients (oligotrophic) due to precipitation of essentialphosphate. Normalpond life is unable to survive, and skeletons of freshwater molluscs such asSphaerium andPlanorbis accumulate as part of the bottom marl.[13]
In Hungary, Buda Marl is found that was formed in theUpper Eocene era. It lies between layers of rock and soil and may be defined it as both "weak rock and strong soil."[16]
Marl has been used as asoil conditioner and neutralizing agent for acid soil[13][17] and in the manufacture ofPortland cement.[18] Because some marls have a very lowpermeability, they have been exploited for construction of theChannel Tunnel between England and France and are being investigated for the storage ofnuclear waste.
Marl is one of the oldestsoil amendments used in agriculture. In addition to increasing available calcium, marl is valuable for improvingsoil structure and decreasing soil acidity[19] and thereby making other nutrients more available.[20] It was used sporadically in Britain beginning in prehistoric times[21] and its use was mentioned byPliny the Elder in the 1st century.[22] Its more widespread use from the 16th century on contributed to the early modern agricultural revolution.[21] However, the lack of a high-energy economy hindered its large-scale use until theIndustrial Revolution.[20]
Marl was used extensively in Britain, particularly inLancashire, during the 18th century. The marl was normally extracted close to its point of use, so that almost every field had a marl pit, but some marl was transported greater distances by railroad. However, marl was gradually replaced by lime and imported mineral fertilizers early in the 19th century.[23] A similar historical pattern was seen in Scotland.[21]
Marl was one of a few soil amendments available in limited quantities in the southern United States, where soils were generally poor in nutrients, prior to about 1840.[24] By the late 19th century, marl was being mined on an industrial scale inNew Jersey[25] and was increasingly being used on a more scientific basis, with marl being classified by grade[26][27] and the state geological survey publishing detailed chemical analyses.[28]
Marl continues to be used for agriculture into the 21st century, though less frequently.[29] The rate of application must be adjusted for the reduced content of calcium carbonate versus straight lime, expressed as the calcium carbonate equivalent. Because the carbonate in marl is predominantly calcium carbonate,magnesium deficiency may be seen in crops treated with marl if they are not also supplemented with magnesium.[17]
Marl has been used inPamlico Sound to provide a suitable artificial substrate foroysters in a reef-like environment.[29]
Marl has been used in the manufacture of Portland cement.[18] It is abundant and yields better physical and mechanical properties than metakaolin as a supplementary cementitious material[30] and can becalcined at a considerably lower temperature.[31][32]
The Channel Tunnel was constructed in the West Melbury Marly Chalk, ageological formation containing marl beds. This formation was chosen because of its very low permeability, absence ofchert, and lack of fissures found in overlying formations. The underlying Glauconitic Marl is easily recognizable in core samples and helped establish the right level for excavating the tunnel.[33]
Marl soil has poor engineering properties, particularly when alternately wetted and dried.[34] The soils can be stabilized by addingpozzolan (volcanic ash) to the soil.[35]
Some marl beds have a very low permeability and are under consideration for use in the storage ofnuclear waste. One such proposed storage site is the Wellenberg in central Switzerland.[36]
A marl lake is a lake whose bottom sediments include large deposits of marl.[18] They are most often found in areas of recent glaciation[37] and are characterized by alkaline water, rich in dissolved calcium carbonate, from which carbonate minerals are deposited.[38]
Marl lakes have frequently been dredged or mined for marl, often used for manufacturingPortland cement.[18] However, they are regarded as ecologically important,[39] and are vulnerable to damage bysilting,nutrient pollution,drainage, andinvasive species. In Britain, only the marl lakes of the more remote parts of northern Scotland are likely to remain pristine into the near future.[38]
Woll, F. W. (1896)."The Marls of Wisconsin".Thirteenth Annual Report of the Agricultural Experiment Station of the University of Wisconsin. Vol. 13. Madison, WI: Democrat Printing Company. p. 295. Retrieved2017-01-06.
Bahadori, Hadi; Hasheminezhad, Araz; Taghizadeh, Farshad (February 2019). "Experimental Study on Marl Soil Stabilization Using Natural Pozzolans".Journal of Materials in Civil Engineering.31 (2): 04018363.doi:10.1061/(ASCE)MT.1943-5533.0002577.S2CID139402321.
Blatt, Harvey; Tracy, Robert J. (1996).Petrology : igneous, sedimentary, and metamorphic (2nd ed.). New York: W.H. Freeman.ISBN0716724383.
Boggs, Sam (2006).Principles of sedimentology and stratigraphy (4th ed.). Upper Saddle River, N.J.: Pearson Prentice Hall. p. 172.ISBN0131547283.
Bristow, Roger; Mortimore, Rory; Wood, Christopher (January 1997). "Lithostratigraphy for mapping the Chalk of southern England".Proceedings of the Geologists' Association.108 (4):293–315.Bibcode:1997PrGA..108..293B.doi:10.1016/S0016-7878(97)80014-4.
Dodgshon, Robert A. (1978). "Land Improvement in Scottish Farming: Marl and Lime in Roxburghshire and Berwickshire in the Eighteenth Century".The Agricultural History Review.26 (1):1–14.CiteSeerX10.1.1.682.5686.JSTOR40273909.
Duston, Nina M.; Owen, Robert M.; Wilkinson, Bruce H. (December 1986). "Water chemistry and sedimentological observations in littlefield lake, michigan: Implications for lacustrine marl deposition".Environmental Geology and Water Sciences.8 (4):229–236.Bibcode:1986EnGeo...8..229D.doi:10.1007/BF02524950.S2CID128421594.
Harris, C.S.; et al., eds. (1996).Engineering Geology of the Channel Tunnel. London: Thomas Telford. p. 57.ISBN0-7277-2045-7.
Lauridsen, B.W.; Surlyk, F. (November 2008). "Benthic faunal response to late Maastrichtian chalk–marl cyclicity at Rørdal, Denmark".Palaeogeography, Palaeoclimatology, Palaeoecology.269 (1–2):38–53.Bibcode:2008PPP...269...38L.doi:10.1016/j.palaeo.2008.07.001.
Leeder, M. R. (2011).Sedimentology and sedimentary basins : from turbulence to tectonics (2nd ed.). Chichester, West Sussex, UK: Wiley-Blackwell.ISBN9781405177832.
Mathew, W. M. (1993). "Marling in British Agriculture: A Case of Partial Identity".The Agricultural History Review.41 (2):97–110.JSTOR40274955.
Pentecost, Allan (December 2009). "The Marl Lakes of the British Isles".Freshwater Reviews.2 (2):167–197.doi:10.1608/FRJ-2.2.4.S2CID86157620.
Perri, Francesco; Dominici, Rocco; Critelli, Salvatore (March 2015). "Stratigraphy, composition and provenance of argillaceous marls from the Calcare di Base Formation, Rossano Basin (northeastern Calabria)".Geological Magazine.152 (2):193–209.Bibcode:2015GeoM..152..193P.doi:10.1017/S0016756814000089.S2CID129302757.
Rakhimov, Ravil Z.; Rakhimova, Nailia R.; Gaifullin, Albert R.; Morozov, Vladimir P. (May 2017). "Properties of Portland cement pastes enriched with addition of calcined marl".Journal of Building Engineering.11:30–36.doi:10.1016/j.jobe.2017.03.007.
Rakhimova, Nailia R.; Rakhimov, Ravil Z.; Morozov, Vladimir P.; Gaifullin, Albert R.; Potapova, Ludmila I.; Gubaidullina, Alfiya M.; Osin, Yury N. (July 2018). "Marl-based geopolymers incorporated with limestone: A feasibility study".Journal of Non-Crystalline Solids.492:1–10.Bibcode:2018JNCS..492....1R.doi:10.1016/j.jnoncrysol.2018.04.015.S2CID102945891.
Rankin, Bill; Williams, Ron (2012)."Channel Tunnel".The Geological Society. The Geological Society of London. Retrieved1 February 2022.
Winiwarter, Verena; Blum, Winfried E. H. (June 2008). "From marl to rock powder: On the history of soil fertility management by rock materials".Journal of Plant Nutrition and Soil Science.171 (3):316–324.doi:10.1002/jpln.200625070.
Schurrenberger, D., Russell, J. and Kerry Kelts. 2003.Classification of lacustrine sediments based on sedimentary components. Journal of Paleolimnology 29: 141–154.
