Avers-Decke
Back to Avers nappeRepresentation and status
- Color CMYK
- N/A
- Color RGB
- R: 241 G: 239 B: 237
- Rank
- tectonic
- Validity
- Unit is in Use
- Status
- valid
Nomenclature
- Deutsch
- Avers-Decke
- Français
- Nappe de l'Avers
- Italiano
- Falda dell'Avers
- English
- Avers Nappe
- Origin of the Name
- Historical Variants
-
«synclinal» de l'Avers (Trümpy 1970), Externer Piemont-Trog = Avers (Büchi & Trümpy 1976), Avers-Zone, Avers Nappe (TK500 / Gouffon et al. 2024)
Description
- Description
-
... bestehend aus kalkigem Glimmerschiefer.
Inhomogene, sandig-tonig-kalkige Metasedimente, meta-ophiolithisches Material (Metaggabros, Prasinite, Serpentinite), sowie Radiolarit, Aptychenkalk und Palombini-Schiefer (Montrasio 1984, Liniger & Nivergelt 1990, Liniger 1992, Spillmann 1993 S.14)
Hierarchy and sequence
- Lower boundary
-
Suretta-Decke: "Im Avers und im Valmalenco folgen darüber Kalkschiefer, welche ohne genaue lithologische und tektonische Trennung übergehen in inhomogene, sandig-tonig-kalkige Metasedimente, welche meta-ophiolithisches Material (Metaggabros, Prasinite, Serpentinite) und zugehörige südpenninische Sedimente (Radiolarit, Aptychenkalk, Palombini) enthalten (Montrasio 1984, Liniger & Nivergelt 1990, Liniger 1992)." (Spillmann 1993 S.14)
Age
- Age at top
-
- Cretaceous
- Age at base
-
- Jurassic
Geography
- Geographical extent
- Avers und Val Malenco (Lanzada-Fenster).
Palaenography and tectonic
- Paleogeography
- Piemont Basin
- Tectonic unit (resp. main category)
- Kind of protolith
-
- tectonic
References
- Definition
-
(2024) :
Tectonic Map of Switzerland 1:500000, Explanatory notes. Federal Office of Topography swisstopo, Wabern
p.77: The Avers Nappe is made up of shaly-calcareous-sandy marine sediments and ophiolitic rocks originating from the Piemonte-Liguria Ocean. This nappe represents an accretionary wedge at the base of an upper plate consisting of the other Upper Penninic and overlying Austroalpine nappes. This wedge directly overlies the Mesozoic cover of the Middle Penninic Suretta Nappe and probably formed in the Early Paleocene (Schmid et al. 1996 b). The basal thrust of the Avers Nappe was deformed congruently with the Suretta Nappe, and both units were later back-folded together in the upper limb of the huge Niemet-Beverin Backfold (Milnes & Schmutz 1978, Schmid et al. 1996 b, Scheiber et al. 2012). A backthrust that formed during this same phase brought part of the Middle Penninic Schams Nappe Complex back towards SE over the Avers Nappe. In its southernmost part, a large normal fault (Turba Mylonite Zone) separates the Avers Nappe and the backthrust Schams and Tomül nappes in the footwall from the Platta and Malenco-Forno-Lizun nappes in the hangingwall (Nievergelt et al. 1996).
Next to the sediments of the Suretta Nappe, the larger of the two Lanzada Windows in Val Malenco (§ 6.3.2.1) exposes some small occurrences of metagabbro and ultramafics that are correlated with the Avers Nappe, hosting a recently detected eclogite (Droop & Chavrit 2014). This, together with the occurrence of blueschists in the Avers Nappe (Oberhänsl i 1978), documents the existence of a probably Paleocene major subduction zone at the base of the other Upper Penninic units (Schmid et al. 1997 b). Note, however, that the accretion of these other Upper Penninic nappes (described hereafter) below the Austroalpine nappe pile occurred earlier, i. e., during the Late Cretaceous (Handy et al. 1996).