The Infrahelvetic complex is a
tectonic
Tectonics ( via Latin ) are the processes that result in the structure and properties of the Earth's crust and its evolution through time. The field of ''planetary tectonics'' extends the concept to other planets and moons.
These processes ...
unit in the
Swiss Alps
The Alps, Alpine region of Switzerland, conventionally referred to as the Swiss Alps, represents a major natural feature of the country and is, along with the Swiss Plateau and the Swiss portion of the Jura Mountains, one of its three main Physica ...
. It consists of
autochthonous
Autochthon, autochthons or autochthonous may refer to:
Nature
* Autochthon (geology), a sediment or rock that can be found at its site of formation or deposition
* Autochthon (nature), or landrace, an indigenous animal or plant
* Autochthonou ...
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, 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 Infrahelvetic complex consists of
Mesozoic
The Mesozoic Era is the Era (geology), era of Earth's Geologic time scale, geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceous Period (geology), Periods. It is characterized by the dominance of archosaurian r ...
cover rocks, most notably massive
limestone
Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...
s from the European
continental shelf
A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an islan ...
. These limestones have a shallower marine
facies
In geology, a facies ( , ; same pronunciation and spelling in the plural) is a body of rock with distinctive characteristics. The characteristics can be any observable attribute of rocks (such as their overall appearance, composition, or con ...
than contemporary sediments from the Helvetic nappes since they were originally deposited north of those units. The
Triassic
The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...
and
Permian
The Permian ( ) is a geologic period and System (stratigraphy), 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 251.902 Mya. It is the s ...
consist of
dolomites,
marl
Marl is an earthy material rich in carbonate minerals, Clay minerals, clays, and silt. When Lithification, hardened into rock, this becomes marlstone. It is formed in marine or freshwater environments, often through the activities of algae.
M ...
s and
conglomerates. In contrast to the completely
detached
A single-family detached home, also called a single-detached dwelling, single-family residence (SFR) or separate house is a free-standing residential building. It is defined in opposition to a multi-family residential dwelling.
Definitions ...
Helvetic nappes, the Infrahelvetic complex is still lying conformably on top of a
Hercynian basement
A basement is any Storey, floor of a building that is not above the grade plane. Especially in residential buildings, it often is used as a utility space for a building, where such items as the Furnace (house heating), furnace, water heating, ...
which forms the
external massifs of the
Aar
The Aare () or Aar () is the main tributary of the High Rhine (its discharge even exceeds that of the latter at their confluence) and the longest river that both rises and ends entirely within Switzerland.
Its total length from its source to i ...
and
Gotthard nappes.
Geology of the Alps
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