Formation du Pralet

Rappresentazione e statuto

Colore CMYK

(0%,29%,55%,4%)

Colore RGB

R: 245 G: 175 B: 110

Rango

Formazione litostratigrafica

Uso

Unità in uso.

SCS nota

Ratifié par le SKS.

SCS data

27.04.2017

Nomenclatura

Deutsch

Pralet-Formation

Français

Formation du Pralet

Italiano

Formazione del Pralet

English

Pralet Formation

Origine del nome

Creux du Pralet (VD), au nord du Rocher Plat

Varianti storiche

Cycle III = Pralet Formation (Baud et al. 2016)

Nota sul nome

Bereich der spätigen Lumachellen und überlagernden Dolomite, gelben Schiefer und Dolomitbreccien (Genge 1958), Cycle IV + Cycle V (Baud & Mégard-Galli 1975), Cycle III

Descrizione

Potenza

150 m am Seehorn (Genge 1958), 90 m à la localité-type (Baud et al. 2016).

Componenti

• Conodonta

Sephardiella truempy (Hirsch)

Gerarchia e successione

Unità di rango inferiore

• «Obere Rauhwacke» (des Penninikums)
• Membre des Erpilles
• Membre du Balmi (-grabe/-wald)

Unità sovrastante

• Formation de Clôt la Cime

Limite superiore

Surface érosive (Rocher Plat, Seehorn) ou contact tectonique. La Fm. de Clot-la-Cime sus-jacente n'est présente que dans la région de Briançon (France).

Limite inferiore

Contact transgressif sur les dolomies claires du sommet de la Fm. du Wiriehorn.

Età

Geomorfologia

• Ladinico tardo

Età alla base

• Ladinico iniziale

Metodo di datazione

Conodontes (Sephardiella truempy) et comparaisons de faciès (Baud et al. 2016)

Geografia

Estensione geografica

Ecailles du Rocher Plat (SE Château-d'Oex) et du Seehorn (Diemtigtal).

Regione-tipo

Pays d'Enhaut (VD), écaille du Rocher Plat

Località-tipo

• Rocher Plat - Rocher Pourri (VD)
  Caratteristiche del sito
  • Obergrenze
  • Untergrenze
  • typische Fazies
  Agibilità del sito
  • Grat
  Coordinate
  • (2581000 / 1145370)
  Nota
  • Baud et al. 2016 ; base dolomitisée

Sezione-tipo

• Rocher Plat - Rocher Pourri (VD)
  Caratteristiche del sito
  • Obergrenze
  • Untergrenze
  • typische Fazies
  Agibilità del sito
  • Grat
  Coordinate
  • (2581000 / 1145370)
  Nota
  • Baud et al. 2016 Suppl. Mat. Fig. f3/g ; base dolomitisée

Punti d'interesse

• Röti am Seehore (BE)
  Caratteristiche del sito
  • typische Fazies
  Agibilità del sito
  • Grat
  Coordinate
  • (2602060 / 1157480)
  Nota
  • Genge 1958: 150 m, avec base calcaire non dolomitisée

Paleogeografia e tettonica

• Triassico del Briançonnais

Paleogeografia

terrane brianzonese :

microcontinent briançonnais

Termini generici

• Médianes rigides :
  nappe des Préalpes Médianes rigides

Tipo di origine

• sedimentaria

Sequenza

Base = transgression majeure de la limite Anisien/Ladinien (Baud et al. 2016).

Referenze

Definizione

Baud Aymon, Plasencia Pablo, Hirsch Francis, Richoz Sylvain (2016) : Revised middle Triassic stratigraphy of the Swiss Prealps based on conodonts and correlation to the Brianc¸onnais (Western Alps). Swiss J. Geosc. 109/2, 365-377

p. 368: 2.3 Cycle CIII: ‘‘Formation du Pralet ‘‘ (Online Resources 1 and 3)

Mégard-Galli and Baud (1977) having not provided a formation name for this cycle, we propose herein the Pralet Formation for the Prealps. This ‘‘Formation du Pralet’’

overlies conformably the Wiriehorn Formation.

It encompasses two members: the new Balmi and Erpilles Members. Transgressive from the bottom, the Balmi Member (Online Resources 1 and 3) starts with light

coloured dolo-grainstone, followed by the large transgressive unit of the ‘‘Couches à Costatoria goldfussi’’ that represents the peak of the transgression (MFS). It ends with the sudden appearance of crinoidal limestone, with a brown dolomite at its top.

The second member, the Erpillles Member, starts with terrigenous yellowish clay (mudstone). This sudden terrigenous input was previously interpreted as the base of a new cycle (Cycle IVa, Mégard-Galli and Baud 1977). But it is at present interpreted as the continuation of the high-stand deposit of Cycle III that consists of the thick, partly brecciated, dolomite of the Erpilles Member. We propose a Ladinian age for the Pralet Formation time interval, with the Balmi Member being Early Ladinian (Fig. 3 and Online Resources 1, 2 and 3 for further details).

Materiale e vario

15203277