TheMuschelkalk (German for "shell-bearing limestone";French:calcaire coquillier) is a sequence ofsedimentaryrock strata (alithostratigraphic unit) in thegeology of central and western Europe. It has aMiddle Triassic (240 to 230 million years) age and forms the middle part of the three-partGermanic Trias (that gives theTriassic its name) lying above the olderBuntsandstein and below the youngerKeuper. The Muschelkalk ("mussel-chalk") consists of a sequence oflimestone anddolomitebeds.

In the past, the time span in which the Muschelkalk was deposited could also be called "Muschelkalk". In modernstratigraphy, however, the name only applies to the layers of rock.

The nameMuschelkalk was first used by German geologistGeorg Christian Füchsel (1722-1773). In 1834,Friedrich August von Alberti included it into the Triassicsystem. The name indicates a characteristic feature of the unit, namely the frequent occurrence of lenticular banks composed offossil shells. The Muschelkalk is restricted to thesubsurface in most of Germany and adjacent regions as theLow Countries, theNorth Sea and parts ofSilesia,Poland andDenmark.Outcrops are found inThuringia, theHarz,Franconia,Hesse,Swabia, and theSaarland and inAlsace.

The Muschelkalk was deposited in a land-locked sea which, in the earlier part of its existence, had only imperfect communications with the more open waters of theTethys Ocean to the south. Thebasin in which the Muschelkalk was deposited is called theGermanic Basin.

Sometimes stratigraphic units with the same age from theAlps, southern Europe and evenAsia are called Muschelkalk too. Of course these rocks have little history in common with the central European Muschelkalk except for similarities in fossil content. Closer at hand, theAlpine Muschelkalk differs in many respects from that of Central Europe, and in its characteristic fossil fauna has a closer affinity with the TriassicTethys realm.

The Muschelkalk can be up to 100 meters thick; it is divisible into three subdivisions, of which the upper and lower are pale thin-beddedlimestones with greenish-greymarls, the middle group being composed ofgypsiferous andsaliniferous marls with dolomite.Stylolites are common in all the Muschelkalk limestones.

The lithostratigraphic status of the Muschelkalk differs regionally. In Germany it is considered agroup, in theNetherlands aformation.

The German Muschelkalk Group is subdivided into three subgroups: Upper, Middle and Lower Muschelkalk. The Lower Muschelkalk consists mainly of limestone, calcareous marls and clayey marls. Some beds are composed of porous cellular limestone, the so-calledSchaumkalk, there are alsooolite beds. The Lower Muschelkalk is divided into six formations:Jena Formation,Rüdersdorf Formation,Udelfangen Formation,Freudenstadt Formation andEschenbach Formation. The Lower Muschelkalk is sometimes calledWellenkalk,German:Welle the "wave" chalk, so called on account of the buckledwavy character thebedding has received. In the Saarland and Alsace and northernEifel, the Lower Muschelkalk has more sandy beds, theMuschelsandstein., "mussel sandstone"

The Middle Muschelkalk orAnbydnite Group consists mainly ofevaporites (gypsum,anhydrite andhalite) and is divided into three formations:Karlstadt Formation,Heilbronn Formation andDiemel Formation. Thesedimentary facies at the margins of the Germanic Basin is different and these deposits are classified as a separate formation, theGrafenwöhr Formation, which continues into the Upper Muschelkalk. In the Middle Muschelkalk, weathering can form characteristic cellular dolomite (Zellendolomit).

The Upper Muschelkalk (Hauptmuschelkalk) is similar to the Lower Muschelkalk and consists of regular beds of shelly limestone, marl and dolomite. It is divided into six formations:Trochitenkalk,Meißner Formation,Irrel Formation,Gilsdorf Formation andWarburg Formation. The lower portion or Trochitenkalk is often composed entirely of the fragmentary stems of the crinoidEncrinus liliiformis; higher up come beds with a series ofammonites,Ceratites compressus,Ceratites nodosus, andCeratites semipartitus in ascending order. In Swabia and Franconia the highest beds are platy dolomites withTringonodus sandergensis and thecrustaceanBairdia.

In addition to the fossils mentioned above, the following are Muschelkalk forms:Coenothyris vulgaris, Mentzelia mentzeli andSpiriferina hirsuta, Myophoria vulgaris, Rhynchotites hirundo, Ceratites munsteri, Ptychites studeri, Balatonites balatonicus, Aspidura scutellata,Daonella lommeli, and in the Alpine region several rock-formingalgae (for example,Baciryllium, Gyroporella, andDiplopora).

The salt beds are worked atHalle (Saale),Bad Friedrichshall,Heilbronn,Szczecin andErfurt. It is from this division that many of the mineral springs ofThuringia and south Germany obtain their saline contents.

• Teufelshöhle (near Steinau)

•  This article incorporates text from a publication now in thepublic domain: Chisholm, Hugh, ed. (1911). "Muschelkalk".Encyclopædia Britannica (11th ed.). Cambridge University Press.

• Triassic System of Europe
• Lithostratigraphy
• Geology of Germany
• Lithostratigraphy of Germany
• Stratigraphy of Europe
• Limestone

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