Infrahelvetic Complex

The Infrahelvetic complex is a

tectonic Tectonics (; ) are the processes that control the structure and properties of the Earth's crust and its evolution through time. These include the processes of mountain building, the growth and behavior of the strong, old cores of continents ...

unit in the

Swiss Alps The Alpine region of Switzerland, conventionally referred to as the Swiss Alps (german: Schweizer Alpen, french: Alpes suisses, it, Alpi svizzere, rm, Alps svizras), represents a major natural feature of the country and is, along with the Sw ...

. It consists of

autochthonous Autochthon, autochthons or autochthonous may refer to: Fiction * Autochthon (Atlantis), a character in Plato's myth of Atlantis * Autochthons, characters in the novel ''The Divine Invasion'' by Philip K. Dick * Autochthon, a Primordial in the ' ...

rocks of the former southern

continental margin A continental margin is the outer edge of continental crust abutting oceanic crust under coastal waters. It is one of the three major zones of the ocean floor, the other two being deep-ocean basins and mid-ocean ridges. The continental marg ...

of the European Plate. The Infrahelvetic complex has been overthrusted by the

Helvetic nappes {{Unreferenced, date=June 2019, bot=noref (GreenC bot) The Helvetic nappes (german: Helvetische Decken) are a series of nappes in the Northern part of the Alps and part of the Helvetic zone. They consist of Mesozoic limestones, shales and marls tha ...

, that partly contain similar rocks. It crops out in the northern part of the canton of Graubünden, generally south and below the Helvetic nappes and north of the

Penninic nappes The Penninic nappes or the Penninicum, commonly abbreviated as Penninic, are one of three nappe stacks and geological zones in which the Alps can be divided. In the western Alps the Penninic nappes are more obviously present than in the eastern ...

. The Infrahelvetic complex consists of

Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Creta ...

cover rocks, most notably massive

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms wh ...

s from the European continental shelf. These limestones have a shallower marine

facies In geology, a facies ( , ; same pronunciation and spelling in the plural) is a body of rock with specified characteristics, which can be any observable attribute of rocks (such as their overall appearance, composition, or condition of formatio ...

than contemporary sediments from the Helvetic nappes since they were originally deposited north of those units. The

Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago (Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...

and

Permian The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Pale ...

consist of dolomites, marls and conglomerates. In contrast to the completely

detached A stand-alone house (also called a single-detached dwelling, detached residence or detached house) is a free-standing residential building. It is sometimes referred to as a single-family home, as opposed to a multi-family residential dwelling ...

Helvetic nappes, the Infrahelvetic complex is still lying conformably on top of a

Hercynian The Variscan or Hercynian orogeny was a geologic mountain-building event caused by Late Paleozoic continental collision between Euramerica (Laurussia) and Gondwana to form the supercontinent of Pangaea. Nomenclature The name ''Variscan'', comes f ...

basement A basement or cellar is one or more Storey, floors of a building that are completely or partly below the storey, ground floor. It generally is used as a utility space for a building, where such items as the Furnace (house heating), furnace, ...

which forms the external massifs of the

Aar AAR or Aar may refer to: Geography *Aar, a river in Switzerland, tributary of the Rhine * Aar (Lahn), a tributary of Lahn river in Germany, descending from the Taunus mountains *Aar (Dill), a tributary of Dill river in Germany, also in the basi ...

and

Gotthard nappe The Gotthard nappe (german: Gotthard-Decke, in older literature called the Gotthard Massif) is, in the geology of the Alps a nappe in the Helvetic zone of Switzerland. It consists of crystalline rocks that were, before the formation of the Alps, pa ...

s. Geology of the Alps {{regional-geology-stub