Zona di Mergoscia

Representation and status

Color CMYK

N/A

Color RGB

R: 241 G: 239 B: 237

Rank

tectonic zone

Validity

Unit is in Use

Status

informal term

Status discussion

Nomenclature

Deutsch

Mergoscia-Zone

Français

Zone de Mergoscia

Italiano

Zona di Mergoscia

English

Mergoscia Zone

Origin of the Name

Valle di Mergoscia (TI)

Historical Variants

Zone von Mergoscia (Kobe 1954 und 1956), zona di Mergoscia, Mergoscia-Zone, Someo zone (Brouwer et al. 2005), Mergoscia zone, Mergoscia nappe, Mergoscia mélange, Mergoscia unit (Steck et al. 2013), --- (Bächlin et al. 1974, Spicher & Wenk 1981, Steck et al. 2013), Zona di Mergoscia (Della Torre & Maggini 2015)

Nomenclatorial Remarks

Arbedozone (Mittelholzer 1936)

Description

Description

eclogites-bearing mélange unit ; Le litologie più comuni sono costituite da micascisti con frequenti granati rossi e gneiss chiari a granulometria da media a fine, entrambi di origine sedimentaria.

Hierarchy and sequence

Subordinate units

• Scisti del Gaggio
• Gneiss di Mergoscia

Age

Age at top

• Mesozoic

Note about top

unsicher

Age at base

• Paleozoic

Note about base

unsicher

Geography

Geographical extent

Lepontin [kommt auf den GA25-Blättern 145_Bosco/Gurin und 159_Locarno vor]

References

Definition

Steck Albrecht, Della Torre F., Keller Franz, Pfeifer Hans-Rudolf, Hunziker Johannes, Masson Henri (2013) : Tectonics of the Lepontine Alps : ductile thrusting and folding in the deepest tetonic levels of the Central Alps. Swiss Journal of Geosciences, 106/3, 427-450

p.433: The eclogitic Mergoscia and Cima Lunga units and the amphibolite facies Bosco–Bombogno–Isorno–Orselina zone have a very similar lithology and occur in the same tectonic position on top of the Antigorio and below the Maggia nappes to the east and below the Osbarino unit and the Monte Leone nappe to the west, in the Wandfluhhorn–Alpe Bosa fold structure. The delimitation of the eclogitic Mergoscia unit from the Antigorio nappe is arbitrary and only based on the presence or absence of rare eclogite relicts. The very heterogeneous Mergoscia and Bosco–Bombogno–Isorno–Orselina units are composed of polycyclic basement rocks, granite gneiss, ophiolites and calcschists, the latter of a probable Mesozoic age. The heterogeneity of these units indicates a strong deformation by folding and boudinage of more competent layers. Only a detailed mapping can show if the term ‘‘tectonic mélange’’ used by Trommsdorff (1990) and Engi et al. (2001a, b) is justified. Berger et al. (2005) attribute these units to a Paleogene tectonic accretion channel. Contrary to them, we distinguish in this zone, (1) the Mergoscia and Cima Lunga units characterised by Paleogene eclogites and their relicts, later overprinted by the Oligocene amphibolite facies regional metamorphism, from

(2) the Bosco–Bombogno–Isorno–Orselina zone of the southern steep belt (...)