Mélange dell'Alpe Tamia-Campo

Représentation et statut

Couleur CMYK

(0%,0%,20%,4%)

Couleur RGB

R: 245 G: 245 B: 195

Rang

Formation lithostratigraphique

Usage

Ce terme est en usage.

Status

terme informel

Nomenclature

Deutsch

Alpe-Tamia-Campo-Melange

Français

Mélange de l'Alpe Tamia-Campo

Italiano

Mélange dell'Alpe Tamia-Campo

English

Alpe Tamia-Campo Mélange

Origine du nom

Alpe Tamia (Italia), WSW Pizzo Mèdola

Variantes historiques

Alpe Tamia–Campo wildflysch with blocks of marble (Matasci et al. 2011 p.266)

Hiérarchie et succession

Unités sus-jacentes

• Mélange di Tamier-Zött

Géographie

Extension géographique

Lepontin: Alpe Tamia, Basodino, Campo.

Références

Définition

Matasci Battista, Epard Jean-Luc, Masson Henri (2011) : The Teggiolo zone: a key to the Helvetic–Penninic connection (stratigraphy and tectonics in the Val Bavona, Ticino, Central Alps). Swiss J. Geosci. 104, 257–283

p.266: 3.5.2 The Alpe Tamia–Campo wildflysch with blocks of marble

This wildflysch forms the lower half of the Robièi formation in a zone that extends from Alpe Tamia (Italy, WSW of the P. Mèdola), through the steep southern and eastern slopes of the Basodino peak (Carreras and Jequier 2002), down to the surroundings of Campo. Most of the blocks are made of a white, pure calcitic marble, identical to the Sevinèra marble. More rarely they are yellowish or even brownish and made of more or less quartzic and micaceous limestone; in these cases the similarity is with the yellow member of the Sevinèra marble. The first blocks are small and appear a few meters or decameters above the top of the Mèdola quartzite. Their size can be as small as a few cm, like pebbles, but more frequently they are dm- to m-wide and have a lenticular shape (Fig. 4). In its lower part the calcschist can also contain cm-thick layers of yellow impure limestone that we interpret as calciturbidites. Higher up the blocks become progressively larger (Fig. 5). They commonly reach a decametric length and detailed observation in good outcrops convincingly shows that they are completely surrounded by the calcschists in three dimensions. Finally they pass to very elongated slices of hectometric length with a thickness of several meters or decameters. Some of the largest ones, well visible in the high cliffs SE and E of the Basodino, have been mapped by Burckhardt and Günthert (1957). The contact of this wildflysch upon the Mèdola quartzite is variable. At some places it looks sharp, at others transitional over a distance of several m. Taking account of the fact that an unconformity might exist at the base of the Mèdola quartzite (see above), we have to allow for the possibility that this unconformity would mark the true base of the fourth sedimentary cycle and that the Mèdola quartzite would represent a first stage of normal, well stratified sedimentation in this cycle before the onset of the Alpe Tamia–Campo wildflysch. This question requires more detailed studies.