Falda Orobica superiore
Back to South AlpineRepresentation and status
- Index
- OO
- Color CMYK
- N/A
- Color RGB
- R: 241 G: 239 B: 237
- Rank
- nappe
- Validity
- Unit is in Use
- Status
- valid
Nomenclature
- Deutsch
- Obere Orobische Decke
- Français
- Nappe Orobique supérieure
- Italiano
- Falda Orobica superiore
- English
- Upper Orobic Nappe
- Origin of the Name
-
Alpi Orobie = Bergamasker Alpen
- Historical Variants
-
Obere Orobische Decke = Upper Orobic Nappe (TK500 / Gouffon et al. 2024)
Hierarchy and sequence
- Units at floor
Geography
- Geographical extent
- Alpi Bergamasche.
Palaenography and tectonic
- Paleogeography
-
Adriatic continental margin
:
southern, passive continental margin / platform
- 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.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.