Val-Gliems-Formation

Rappresentazione e statuto

Index

P-Gl

Colore CMYK

(23%,0%,13%,39%)

Colore RGB

R: 120 G: 155 B: 135

Rango

Formazione litostratigrafica

Uso

Unità in uso.

Status

termine informale

Nomenclatura

Deutsch

Val-Gliems-Formation

Français

Formation du Val Gliems

Italiano

Formazione della Val Gliems

English

Val Gliems Formation

Origine del nome

Val Gliems (GR), Sumvitg

Varianti storiche

Vals Gliems Metasediments (Franks 1968), Val-Gliems-Formation (Böhm 1986, Gisler 2018), Val Gliems Formation (Berger et al. 2017)

Nota sul nome

Knotenschiefer, Konglomeratgneis

Gerarchia e successione

Unità di rango superiore

• Streifengneis-Komplex

Unità di rango inferiore

• Metapelitische Abfolge (Val-Gliems-Fm.)
• Metavulkaniklastische Abfolge (Val-Gliems-Fm.)

Unità sovrastante

• Sandpass-Formation

Limite superiore

Sandpass-Formation bzw. Mesozoische Sedimente des Autochtons

Limite inferiore

Altkristallin im Norden, Südlicher Aaregranit im Süden.

Età

Geomorfologia

• Primo Carbonifero

Età alla base

• Primo Paleozoico

Metodo di datazione

Prä-Viséen (intrudiert durch der Tödi-Granit).

Geografia

Estensione geografica

Chrüzlital, oberes Val Strem/Calmut, Val Cavardiras, Val Russein, Val Gliems.

Referenze

Definizione

Böhm C. (1988) : Vulkanoklastite im östlichen Aarmassiv (Val Russein, Graubünden). Schweiz. mineral. petrogr. Mitt. 68/3, 501–508

Revisione

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.34: BÖHM (1988) defined the Val Gliems Formation. He was the first to recognise the volcanic and volcaniclastic character and described in detail the internal stratigraphic relationships. The Val Gliems Formation can be subdivided into two sequences: a volcaniclastic sequence, and a metasedimentary (metapelitic) sequence (BÖHM 1988). The metapelitic sequence is identical to the “phyllite unit” of EUGSTER (1951), whereas the “banded psammitic schists and black pelitic schists” of EUGSTER (1951), as well as the “upper and the lower conglomerate layer” of FRANKS(1968 b) all correspond to the volcaniclastic sequence of BÖHM (1988). The volcanic rocks vary in composition from dacitic to rhyodactic and show a calc-alkaline affinity (BÖHM 1988). On the base of its stratigraphic reconstruction, BÖHM (1988) interpreted the structural organisation of the Val Gliems Formation as a large fold with a steeply plunging fold axis. The upper age limit of the Val Gliems Formation is defined by the age of the granite intruding along its northwestern margin. This granite is the western continuation of the Visean Tödi Granite (pers. comm.C.Gisler) and not the eastern end of the Asselian Central Aar Granite, as proposed by EUGSTER (1951) and VÖGELI (1988). Thus, the situation in the Val Gliems is the same as in the Bifertenfirn area where the granitoids of the Tödi Granite Complex intrude the metasedimentary and volcaniclastic rocks of the Bifertenfirn Formation. Besides lithological and structural similarity of the Bifertenfirn Formation and Val Gliems Formation (FRANKS 1968 b, BÖHM 1988), these intrusive relationships confirm the pre-Visean age of the Val Gliems Formation and justify the attribution of the two formations to the Cavardiras Group.