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Marl(märl), city (1994 pop. 92,590), North Rhine–Westphalia, W Germany. It is an industrial and mining (coal, lead, and zinc) center, and also supports a number of chemical factories. Now a modern city, Marl was first mentioned in the 9th cent. and was chartered in 1936.
bog lime,soil, essentially clay mixed with carbonate of lime, highly valued as a dressing or fertilizer. It crumbles rapidly and easily. Marl in which the lime is in the form of invertebrate shells is called shell marl. The term is loosely used for a variety of soils, some of which are low in lime content, e.g., the greensand marl of New Jersey. Marling of soil tends to lighten it, correct acidity, and promote nitrification.
a city in the Federal Republic of Germany in the Land of North Rhine-Westphalia, in the Ruhr. Population, 77,000 (1970). Marl is an important center for the production of synthetic rubber, plastics, synthetic resins, chemical fibers, soda, and chlorine. Coal and lead and zinc ores are mined in the area.
a sedimentary rock composed of calcite or dolomite and clay minerals. The ratio of carbonaceous to clay components may vary. Generally marl is identified as rock containing from 30 to 90 percent CaCO3 or MgCO3 and, correspondingly, from 70 to 10 percent clay particles. There are clay, calcareous, chalky, and dolomite marls and, depending on admixtures, there are siliceous, glauconite, sandy, micaceous, bituminous, and carbonaceous marls. Color varies, most often being light. Marl is widespread in nature and is found in all systems beginning with the Proterozoic. In the USSR marl is universally developed in carbonaceous and clay strata. It is used as a raw material in the production of certain kinds of cement. Natural cement marl containing 75–80 percent CaCOa is the most important. In the USSR the most well-known deposits of cement marl are in the vicinity of Novorossiisk, Amvrosievka (Donetsk Oblast), and the village of Podgornoe (Voronezh Oblast).
Marl deposits are worked by open-cut mining. Processing is done in powerful rotary furnaces working on mixtures of different types of marl and chalk.
G. I. BUSHINSKII