strati.ch - Lithostratigraphic Lexicon of Switzerland

Representation and status

Historical Variants: Intschi-Zone (Guntli et al. 2016), Maderanertal-Intschi Zone, Intschi Formation (Berger et al. 2017), Intschi-Formation (Gisler 2018)

Age at top

Age at base

Paleogeography

European Continent

Tectonic unit (resp. main category)

Definition: Berger Alfons, Mercolli Ivan, Herwegh Marco, Gnos Edwin (2017) : Geological Map of the Aar Massif, Tavetsch and Gotthard Nappes. Geological Special Map 1:100'000, Explanatory Notes 129

p.48: More to the east, in the Urner Reusstal and in the Maderanertal, a series of discontinuous outcrops of Carboniferous rocks occurs that was grouped into the Intschi Formation. Lithostratigraphically, these rocks are very similar to the Windgällen and Trift Formations. OBERHÄNSLI et al.(1988) mentioned that at least one mylonitic contact separates the Late Carboniferous rocks from the surrounding units of the polycyclic metamorphic basement.
The Late Carboniferous rocks, assigned in previous literature to the Färnigen Zone, were considered here as the southwestern continuation of the Intschi Formation. The Färnigen Zone of the present map contains strictly only Mesozoic sedimentary rocks (ALB.HEIM & ARN.HEIM 1916) and therefore belongs to the parautochthonous and autochthonous cover. In the Färnigen area, the Late Carboniferous rocks of the Intschi Formation define the boundary between two blocks of polycyclic metamorphic basement: the Erstfeld Zone in the northwest and the Sustenhorn Zone in the southeast. East of the Intschialp, the Intschi Formation no longer delimits two different zones but is wedged into the Sustenhorn Zone. This geometrical change is most probably due to the interference of Variscan and Alpine thrust faults.