Plattenberg-Brekzie

Retour à nappe de l'Adula

Représentation et statut

Couleur CMYK
(0%,22%,41%,27%)
Couleur RGB
R: 185 G: 145 B: 110
Rang
Formation lithostratigraphique
Usage
Ce terme est en usage.

Nomenclature

Deutsch
Plattenberg-Brekzie
Français
Brèche du Plattenberg
English
Plattenberg Breccia
Origine du nom

Plattenberg (GR)/(TI)

Variantes historiques
Plattenberg Formation = Plattenberg Breccia = Brèche du Plattenberg (Cavargna-Sani et al. 2010, Cavargna-Sani 2013)

Hiérarchie et succession

Limite inférieure
"Dolomie bicolori"

Âge

Âge au sommet
  • Jurassique Tardif
Âge à la base
  • Jurassique Moyen

Références

Définition
Cavargna-Sani Mattia, Epard Jean-Luc, Masson Henri (2010) : Discovery of fossils in the Adula nappe, new stratigraphic data and tectonic consequences (Central Alps). Bull. Soc. vaud. Sci. nat. 92/2, 77-84

p. 78: These dolomites are overlain with a sharp contact by a coarse detrital formation mainly made of dolomitic breccias (figure 3). The dolomite clasts are reworked from the Triassic and they can be so closely packed that the rock looks at first sight like a genuine Triassic dolomite (“reconstituted Triassic”). The matrix is quartzitic to dolarenitic, sometimes also containing mica or calcite. At the base the quartzitic matrix can form a dm-thick layer of pure quartzite (not to be confused with the basal Triassic quartzite). Further upwards the matrix of the breccia becomes dominant and the rock gradually passes to a dolo-quartzarenite. Near the top it may contain a few cm- to dm-thick layers of pure limestone. All these rocks form a well-characterized lithostratigraphic unit that we call the Plattenberg Formation, or Plattenberg Breccia. Discontinuous intercalations or pockets of a reddish rock rich in iron oxides and white mica occur in and at the base of the breccia. We interpret this rock as a (more or less reworked) siderolitic deposit. It provides evidence of post-Triassic emersion and continental erosion before the deposition of the breccia. Three m above the base of the breccia we found in a fine-grained calco-dolarenitic intercalation numerous plates of crinoids (with well preserved details such as the central canal; figure 4). They prove that the deposition of the breccia occurred in a marine environment, under high-energy conditions.

Révision
Cavargna-Sani Mattia (2013) : The Adula nappe: stratigraphy, structure and kinematics of an exhumed high-pressure nappe. Thèse de doctorat, Université de Lausanne, 153 p.

p.117: Plattenberg Formation: dolomitic breccia with quartzitic to dolarenitic matrix. The Breccia contains siderolithic pebbles and presents several dolarenitic to calcarenitic intercalations. One of this intercalations is studded with crinoidal plates. The uppermost part of the breccias contains some intercalations of pure limestone bed. - Coarse-grained micaceous quartzite, only locally present.

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