Ferden–Guttannen-Zone

Representation and status

Color CMYK

N/A

Color RGB

R: 241 G: 239 B: 237

Rank

tectonic zone

Validity

Unit is in Use

Status

valid

Nomenclature

Deutsch

Ferden–Guttannen-Zone

Français

zone de Ferden–Guttannen

Italiano

zona di Ferden–Guttannen

English

Ferden–Guttannen zone

Historical Variants

Zone der Sericitschiefer und Sericitgneisse (Baltzer 1888), Guttannen Unit (von Raumer et al. 1993a), Grenzmylonit (Kammer 1985), Ferden-Guttannen Zone (Berger et al. 2017)

Hierarchy and sequence

Subordinate units

• Guttannen-Gneiskomplex
• Lötschental-Gneiskomplex

References

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.27: In the Ferden-Guttannen Zone, the gneiss complexes that suffered a stronger retrograde alteration than the adjacent gneiss complexes were grouped together. Already BALTZER (1888) recognised this characteristic and named this zone as “Zone der Sericitschiefer und Sericitgneisse”. Unfortunately, due to the variation in the intensity of the alteration, it is not easy to use this observation as a field criterion for defining a boundary on a map, and consequently, there remains uncertainty in locating exact zone boundaries. ABRECHT (1994) reported descriptions of sericite- and chlorite-rich gneiss and schist along the southern boundary of the Erstfeld Zone, ranging from the Lötschental in the west to the Maderanertal in the east. Recent mapping in the Amsteg region indicates that the retrograde-altered rocks in the Maderanertal constitute a set of bands, only a few tens of metres thick, mainly bordering slices of Carboniferous rocks (pers. comm.C.Gisler). Therefore, the Ferden-Guttannen Zone ends in the area west of the Sustenhorn. Local strong deformation associated with the retrograde alteration was proposed as a boundary criterion between the Erstfeld Zone and the adjacent “Guttannen Zone” and was called “Grenzmylonit” by KAMMER (1985). In the Ferden-Guttannen Zone, numerous intercalations of Late Carboniferous metasedimentary and volcaniclastic rocks of the Lötschental-Maderanertal Zone (described by LOTZE 1914) occur. This close association with the surface sequences of the Lötschental-Maderanertal Zone suggests that at least an important part of the greenschist-facies alteration occurred already during the Variscan orogeny.