«Unità del Lucomagno»

Representation and status

Color CMYK
N/A
Color RGB
R: 241 G: 239 B: 237
Rank
nappe
Validity
Unit is in Use
Status
informal term
Status discussion

Nomenclature

Deutsch
«Lucomagno-Einheit»
Français
«Unité du Lukmanier»
Italiano
«Unità del Lucomagno»
English
«Lucomagno Unit»
Origin of the Name

Passo del Lucomagno (TI)

Historical Variants

Lucomagnomassiv (Jenny et al. 1923), Lucomagnodecke (Bosshard 1925), Lucomagno-Decke (Gansser & Dal Vesco 1964), Ricoprimento Lucomagno (Bianconi 1971), Lucomagno-Masse (Büchi & Trümpy 1976), falda del Lucomagno, Lucomagno unit (Böhm et al. 1996), Lucomagno Nappe (Berger et al. 2017)

Description

Description

Involucro paragneissico a misto della falda Leventina-Lucomagno (metapelitischer Paragneis, gebänderter Gneis, Augengneis).

Hierarchy and sequence

Subordinate units

Age

Age at top
  • Mesozoic
Age at base
  • Precambrian

Palaenography and tectonic

Paleogeography
European continental plate
Tectonic unit (resp. main category)

References

Definition
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.

  • zona del (Pizzo) Molare

    Name Origin

    Pizzo Molare (TI)

    Rank
    tectonic zone
    Status
    informal term
    Nomenclatorial Remarks
    <p>Jeannet ----, Alb. Heim 1922</p>
    In short

    Mesozoische Sedimentbedeckung der Lukmanier-Decke: Trias, Bündnerschiefer.

    Age
    Triassic
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  • Cristallino di Prato-Cornone

    Name Origin

    Prato-Leventina (TI)

    Rank
    tectonically bounded lithostratigraphic unit
    Status
    informal term
    In short

    Cristallino della falda Lucomagno: paragneiss scistoso leuco-mesocratico a grana fine, ricco di quarzo, a plagioclasio, due miche, o a biotite, e granato, con marcata tessitura planare-tabulare.

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