Graphitische Einheit (der Camosci-Decke)

Representation and status

Color CMYK

(0%,0%,0%,100%)

Rank

lithostratigraphic Formation

Validity

Unit is in Use

Nomenclature

Deutsch

Graphitische Einheit (der Camosci-Decke)

Français

Unité graphitique (de la nappe des Camosci)

Italiano

Unità grafitica (della falda dei Camosci)

English

Graphitic unit (of the Camosci nappe)

Historical Variants

black phyllitic schists + calcschists complex (Bianchi et al. 1998), Graphitic unit = Toarcian-Aalenian (Carrupt 2003)

Description

Thickness

Environ 75 m (Carrupt 2003 Fig.2.4)

Hierarchy and sequence

Subordinate units

• Detritische Einheit (der Camosci-Decke)

Age

Age at top

• Aalenian

Age at base

• Toarcian

Dating Method

Ennoyement de la plateforme / black shales au Toarcien-Aalénien (Carrupt 2003).

References

Definition

Carrupt Elisabeth (2003) : New stratigraphic, structural and geochemical data from the Val Formazza - Binntal area (Central Alps). Mémoires de Géologie (Lausanne) 41, 103 p.

p.17: Graphitic unit: is characterized by important lateral variations of facies (Fig.10.2). The clearest succession is found in the western part of the nappe. A black graphitic micaschists (metashale, see microscopic description in paragraph III.4) containing porphyroblasts of garnets, immediately follows the Calcareous unit; the contact is clear-cut. It may contain rare thin levels of a calcareous graphitic micaschist (metamarls). Bianchi et al. (1998) found various heavily recristallized bioclasts in the black micaschist. The eastern part is more complex. A calcareous graphitic micaschist (metamarls, see microscopic description in paragraph III.4) containing porphyroblasts of plagioclase or epidote overlies the Calcareous unit. The contact is gradual: thin levels (3 cm) of calcareous micaschist alternate with the calcitic marble; the latter becomes thinner upsection, whereas the calcareous micaschist thickens. Some graded bedding can be observed, indicating the local polarity (Fig.2.4). Up sequence, thin levels of black micaschist are interbedded within the calcareous micaschist. The lateral transition between the western and the eastern part of the Graphitic unit is made over less than 2 m. A very hard and dark 50 cm-thick rock composed of graphite (50%), carbonate (29%), muscovite (12%), opaque (8%) and some accessory minerals, represents the transitional stage between the calcareous micaschist and the black micaschist.