Platta-Decke

Representation and status

Historical Variants: rhätische Decke des Oberhalbstein (Spitz 1917), Plattaserie (Ott 1922), Platta-Decke (Cornelius 1932, Staub 1946), Plattadecke (Stöcklin 1949), nappe du (Piz) Platta (Trümpy 1970), Interner Piemont-Trog = Platta (Büchi & Trümpy 1976), nappe du Piatta (Mayerat Demarne 1994), Platta-Decke = cuverta da la Platta (Manatschal 1995), Platta nappe (Manatschal & Nivergelt 1997), Platta Nappe (TK500 / Gouffon et al. 2024)

Description: Diese Einheit bildet keine kohärente Überschiebungsdecke, sondern zeigt eine Gliederung in einzelne Schuppen, welche z.T. auch nicht-ophiolithisches Material (Kristallin, triassische und frühjurassische Sedimente) enthalten. Ophiolithen und ozeanischen Sedimenten, sowie eingeschuppte ostalpine mesozoische Elemente. Stellt ein südliches Äquivalent der Arosa-Decke dar. Pegmatite und "Casannaschiefer"

Subordinate units

Stratigraphic discussion: Keilt im Oberengadin zwischen der Sella- und der Corvatsch-Teildecke.

Paleogeography

Piemont Basin

Tectonic unit (resp. main category)

Kind of protolith

Definition: Gouffon Yves (Editor) (2024) : Tectonic Map of Switzerland 1:500000, Explanatory notes. Federal Office of Topography swisstopo, Wabern

p.78: The Platta Nappe consists mainly of an ophiolitic basement, including metabasalts, serpentinites and some metagabbros, covered by a thin Late Jurassic to Cretaceous oceanic sedimentary cover, beginning with radiolarian cherts. The mafic rocks have undergone an Alpine greenschist-facies metamorphism. In contrast to the Arosa Zone, the Platta Nappe does not have the character of a mélange (Dietrich 1970); however, its upper part contains slivers of continental lithologies and shows characteristics of an ocean-continent transition (Handy et al. 1996, Manatschal & Nievergelt 1997, Epin et al. 2019). In the south (Upper Engadine), it is separated from the underlying Malenco-Forno-Lizun Nappe by the insertion of the Margna and Sella nappes that are considered part of the Salassic domain (see chapter 6).