«Unità della Leventina»

Représentation et statut

Index

Le / Lev

Couleur CMYK

N/A

Couleur RGB

R: 241 G: 239 B: 237

Rang

nappe

Usage

Ce terme est en usage.

Status

valide

Nomenclature

Deutsch

«Leventina-Einheit»

Français

«Unité de la Léventine»

Italiano

«Unità della Leventina»

English

«Leventina Unit»

Origine du nom

Valle Leventina (TI)

Variantes historiques

Leventinadecke (Bosshard 1925, Kündig 1926a, Bossard 1936), Falda Leventina (Godenzi 1963), Ricoprimento Leventina = Cristallino di Leventina = cristallino antico di Leventina (Bianconi 1971), nappe de la Leventina (Mayerat Demarne 1994), Leventina nappe (Steck et al. 2013), unità della Leventina (Schenker, Bl. Osogna)

Description

Description

Nucleo ortogneissico della Falda Leventina-Lucomagno (heller, flasriger, porphyrischer Zweiglimmergneis).

Steck et al. 2013 p.430: The Leventina nappe is formed of a leucocratic, two micas granite gneiss (Casasopra 1939). It occupies the hinge zone of the NW-striking Ticino dome between Claro and Rodi-Fiesso in the Leventina valley. It is separated from the higher Simano nappe by a quartzitic and mylonitic shear zone that passes at Chiggiogna in a zone of Triassic quartzite and dolomite (Fig. 2; Ru¨tti et al. 2005; Berger et al. 2005).

Hiérarchie et succession

Unités hiérarchiquement subordonnées

• «Quarzite del tetto»
• Gneiss della Leventina

Paléogéographie et tectonique

Termes génériques

• Leventina

Type de protolithe

• tectonique

Références

Définition

Bosshard L. (1925) : Der Bau der Tessinerkulmination. Eclogae geol. Helv. 19/2, 504-521

S.505: Als zweites Glied, folgt ein bis in die Gegend der Dazio Grande vorstossender Granitgneis-Körper. Er bildet die beidseitigen Hänge der Valle Leventina. Seine Bezeichnung als Leventinadecke, die ich dafür gewählt habe, erscheint somit gerechtfertigt. Es ist ein im allgemeinen porphyrarliger, kieselsäure-reicher Zweiglimmergneis von flasrigem Aussehen, wobei die Grösse der Einsprengunge oder Porphyroblasten ziemlich konstant bleibt. Nur die Randfazies zeigt gröberes Korn.

Révision

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

p.50: The Leventina-Lucomagno Nappe is the lowest unit of the Ticino Culmination. The lower part of the nappe (“Leventina Unit”) is made up of several orthogneisses forming a deformed Late Variscan magmatic edifice composed of several magmatic pulses. Along the northeastern flank of the Valle Leventina, the Leventina orthogneisses are covered by a thick stack of paragneisses and micaschists (“Lucomagno Unit”). Along this boundary, sparse quartzitic gneisses (“roof quartzites”) were interpreted as being Mesozoic in age by several authors and hence used to discriminate between a “Leventina Nappe” and a “Lucomagno Nappe”. However, these quartz-rich horizons above the orthogneisses form metasomatically altered zones – in places sheared – and cannot be considered as Mesozoic metasediments (Rütti et al. 2005; see Fig. 7). The “Lucomagno Unit” can therefore be regarded as a pre-Alpine sedimentary shell of the Leventina magmatic edifice deformed during the Alpine orogeny. Quartzitic horizons, similar to those mentioned above, also occur where the Simano Nappe directly overlies the Leventina orthogneisses. The northern part of this nappe contact is often characterized by a mylonitic band (Rütti et al. 2005 and ref. therein). To the south, this mylonitic shear zone dissipates within the Leventina orthogneisses in an anastomosing network of shear bands (Fig. 7). There, the upper limit of the Leventina-Lucomagno Nappe is difficult to trace since paragneiss and calcsilicate lenses – traditionally used to trace the tectonic contact – are in fact deformed xenoliths within the Leventina orthogneisses.
Remnants of Triassic rocks crop out around the frontal part of the Leventina-Lucomagno Nappe, although for some of them it is not clear whether they belong to the Leventina-Lucomagno Nappe or to the adjacent units. Permo-Triassic metasediments crop out also within the Leventina-Lucomagno Nappe, likely as pinched synclines (e.g., Molare Syncline; see Fig. 7) or as intranappe slices.