strati.ch - Lessico lithostratigrafico della Svizzera

Rappresentazione e statuto

Unità sovrastante

Geomorfologia

Età alla base

Metodo di datazione: 514.7 +2.6/-2.2 Ma, 517.1 +2.0/-3.7 Ma (Cavargna-Sani 2013)

Definizione: Cavargna-Sani Mattia (2013) : The Adula nappe: stratigraphy, structure and kinematics of an exhumed high-pressure nappe. Thèse de doctorat, Université de Lausanne, 153 p.

p.29: The Salahorn Formation is the largest paragneiss formation of the northern Adula basement. The highest peak, Adula (or Rheinwaldhorn, 3402 m), is composed of these rocks. The type locality is located near the Salahorn peak in the Zapport valley (Fig. 2), where this formation is completely exposed. The Salahorn Formation is principally composed of metamorphosed clastic sediments (Fig. 3b) varying from quartzitic arkose to metapelites. The transitional contacts between these different clastic rocks are clear in the field, leading to the conclusion that they have to be included in the same formation. The Salahorn Formation is rich in carbonates. Carbonates are generally present as centimetric lenses (Fig. 3b) of brown calcitic, ankeritic, or dolomitic marble. Metric lenses of these carbonates can be found locally (Fig. 3c). The Palaeozoic carbonates of the Salahorn Fm. are not to be confused with the abundant boudins of Mesozoic sediments folded into the Adula basement. In the Salahorn Fm., there is a close association of meta-igneous greenstone and gneiss with the felsic paragneisses. The metaigneous bodies are observable as decimetric to decametric lenses or boudins. Contacts with the clastic country rocks are generally sharp. A transitional contact is sometimes observed.