Falda Orobica superiore

Représentation et statut

Index

OO

Couleur CMYK

N/A

Couleur RGB

R: 241 G: 239 B: 237

Rang

nappe

Usage

Ce terme est en usage.

Status

valide

Nomenclature

Deutsch

Obere Orobische Decke

Français

Nappe Orobique supérieure

Italiano

Falda Orobica superiore

English

Upper Orobic Nappe

Origine du nom

Alpi Orobie = Bergamasker Alpen

Variantes historiques

Obere Orobische Decke = Upper Orobic Nappe (TK500 / Gouffon et al. 2024)

Hiérarchie et succession

Unités sous-jacentes

• Scaglie Orobiche inferiori

Géographie

Extension géographique

Alpi Bergamasche.

Paléogéographie et tectonique

Paléogéographie

marge continentale adriatique :

southern continental margin / platform

Termes génériques

• South Alpine
• Upper Orobic

Type de protolithe

• tectonique

Références

Révision

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

p.103: The uppermost and oldest thrust sheets, the Upper Orobic Nappe, consists of an around 5 to 7 km thick basement sheet, arranged in a series of en-échelon anticlines, first interpreted by Laubscher (1985) as ramp anticlines. The thrusts associated with the Upper Orobic Nappe ramped into the sedimentary cover, creating several duplexes that occur in a belt of klippen. The distribution of these erosional remnants reflects the later deformation by the basement ramps of the underlying younger local thrust sheets and imbricates, namely the Lower Orobic Imbricates.

p.107: The Upper Orobic Nappe can be followed from the Bergamasc Alps across Lago di Como to the area north of Lugano (Bertotti 1991, Real et al. 2018). However, there is no clear-cut Alpine-tectonic boundary in the basement northwest and west of Lugano. Indications suggest that the change from thin-skinned thrust sheets in the east (see Pl. II, eastern cross-section) to thick-skinned ones to the west (see western cross-section) occurs over a broad zone, probably defined by pre-Alpine faults. Because the surface of the Variscan basement was much higher in the area west of the Mesozoic Lugano Fault, the basement involved in thrusting appears to be much thicker west of Lugano than in the east and the tectonic style changes drastically.
To the north, the Upper Orobic Nappe is limited by the Tonale Fault, along which slivers of Triassic dolomites occur, possibly relics of Mesozoic extensional allochthons (Real et al. 2018). East of Lugano, backthrust sediments of the Lower Orobic Imbricates mark the southern boundary of the nappe (Bertotti 1991). West of Lugano, the steeply dipping Permian volcanics and Triassic dolomites along the Tresa Valley mark the boundary with the Varesotto Imbricates (Bernoulli et al. 1976). The contact may be tentatively interpreted as a verticalized thrust or, along a segment northwest of M. Caslano, as a transfer fault. The steeply dipping “Schlingen”-structures of the basement are dissected by a network of S-vergent thrusts connected by transfer faults (Reinhard 1964, Schumacher 1997). The occurrence of small relics of non-metamorphic Permian cover rocks along these faults indicates a post-Variscan age for these structures.