Goms-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

Goms-Zone

Français

Zone du Goms

Italiano

Zona del Goms

English

Goms Zone

Origin of the Name

Goms (VS)

Historical Variants

Goms-Massiv, Gomser Zwischenmassive (Oberholzer 1955), Westliches Gomser Zwischemassiv (Oberholzer 1986), Gomser Zwischenmassiv (Labhart 2005), Goms-Decke, Goms Zone (Berger et al. 2017)

Hierarchy and sequence

Subordinate units

• Goms-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.67: A narrow (max. apparent thickness < 1 km) band of polycyclic gneisses outcrops discontinuously from Fiesch to the area northeast of Unterwasser. OBERHOLZER (1955) mapped this region and defined the tectonic unit “Gomser Zwischenmassive”. He distinguished an eastern and a western “Zwischenmassiv”. The southern border of the “Gomser Zwischemassive” is unclear. Found only in the region of Fiesch (“Westliches Gomser Zwischenmassiv” of OBERHOLZER 1955), a psephitic to psammitic metasedimentary sequence of Carboniferous to Permian age of the Urseren-Garvera Zone (h-pU) delimits the gneisses of the “Westliches Gomser Zwischenmassiv”. The southern branch of these metasedimentary rocks thins out eastwards so that the southern boundary of the “Westliches Gomser Zwischenmassiv” disappears as well. The thinning-out of the Urseren-Garvera Zone marks the northern boundary of the “Östliches Gomser Zwischenmassiv” (northeast of Unterwasser), while at the southern boundary, a psephitic to psammitic metasedimentary sequence is wedged into the polycyclic gneisses. Finally, a clear individualisation of the “Gomser Zwischenmassiv” is questionable when comparing the lithologies of the “Gomser Zwischenmassive” and the Gotthard Nappe (OBERHOLZER 1955). Based on these arguments, already listed by OBERHOLZER (1955), the Goms Zone was defined on the present map sheet (equivalent to the “Gomser Zwischenmassive” of OBERHOLZER 1955) and grouped this together with the polycyclic metamorphic basement of the Gotthard Nappe.
It is important to note that the northeastern end of the Goms Zone is in contact with the southwestern end of the more-or-less complete stratigraphic sequence of the Urseren-Garvera Zone (Carboniferous–Jurassic). From Oberwald southwestward, only a discontinuous band (without outcrops between Blitzingen and Ulrichen) of Carboniferous– Permian metasedimentary rocks connects the Urseren-Garvera Zone with the units of the Termen-Nufenen Zone. Between Unterwasser and the Oberalppass, the Goms Zone disappears and the Urseren-Garvera Zone separates the Ausserberg-Avat Zone (Aar Massif) from the polycyclic gneisses of the Gotthard Nappe.