Conglomérat du Vouan

Torna a falda dei Voirons

Rappresentazione e statuto

Colore CMYK
(0%,13%,50%,22%)
Colore RGB
R: 200 G: 175 B: 100
Rango
Formazione litostratigrafica
Uso
Unità in uso.
Status
termine informale
Discussione del statuto

Nomenclatura

Deutsch
Vouan-Konglomerat
Français
Conglomérat du Vouan
Italiano
Conglomerato del Vouan
English
Vouan Conglomerate
Origine del nome

Mont de Vouan (France)

Varianti storiche

Conglomérats du Vouan (Lombard 1940), série des grès et conglomérats du Vouan (Rutsch et al. 1966), Flysch du Vouan (Karnay 1980), Vouan Conglomerates (Ospina-Ostios et al. 2013), Conglomérat du Vouan (Cogulu 1961, Charollais et al. 1998), Formation des Conglomérats du Vouan (Ragusa 2015)

Descrizione

Descrizione

galets à blocs métriques: fragments cristallins "sudalpins" (Sarasin 1894) et sédimentaires briançonnais (Frébourg 2006)

Geomorfologia
Falaises.
Potenza
300-400 m (Coppo 1999).

Gerarchia e successione

Unità sovrastante
Limite inferiore

Limite biostratigraphique [???] avec les Grès des Voirons, visible au torrent de Cruseilles et au nant de Manant.

Età

Geomorfologia
  • primo Rupeliano
Età alla base
  • tardo Eocene
Metodo di datazione

Lutétien tardif à Priabonien (Vial 1975) ; Eocène tardif à Oligocène précoce (P16-P20 ; Frébourg 2006).

Geografia

Estensione geografica
Mont Vouan, flanc oriental des Voirons et col de Saxel. Probablement encore présent au nord de la Grande Combe et de la Tête de Char, voire jusqu'aux collines d'Allinges.
Regione-tipo
Les Voirons (France)
Sezione-tipo
  • meulière de Grande Gueule (France)
    Caratteristiche del sito
    • typische Fazies
    Agibilità del sito
    • geschützter Geotop
    Coordinate
    • (2518000 / 1114325)
    Nota
    • <p>Ragusa 2015 (6,380586 E / 46,168069 N)</p>

Paleogeografia e tettonica

Termini generici
Tipo di origine
  • sedimentaria
Condizioni di formazione

Faciès proximaux de séquences turbiditiques (Frébourg 2006, Ospina-Ostios et al. 2013).

Referenze

Revisione
Ospina-Ostios Lina M., Ragusa Jérémy, Wernli Roland, Kindler Pascal (2013) : Planktonic foraminifer biostratigraphy as a tool in constraining the timing of flysch deposition: Gurnigel flysch, Voirons massif (Haute-Savoie, France). Sedimentology 60, 225–238

Between 300 m and 400 m thick, the Vouan Conglomerates occur along the eastern flank of the Voirons ridge, but are best exposed in the western cliffs of the Mont Vouan along the Menoge River (Figs 2 and 5C), where they have been mined for millstone. These cliffs consist of plurimetric beds of matrix-supported conglomerates (cobbly and pebbly sandstones) that are occasionally highly weathered and friable, probably due to poor cementation (Frebourg, 2006). Shaly intervals are extremely rare in this formation. The conglomerate matrix is a feldspar-rich arkose (Fig. 3). The centimetre-sized to metre-sized lithoclasts are angular to well-rounded and derive from sedimentary, metamorphic and igneous rocks. The former include Triassic dolostones, crinoidal-rich, bryozoan-rich and oolite-rich limestones of possible Late Jurassic age (Frébourg, 2006), and orbitolinid limestone dating to the Aptian (Cogulu, 1961). Metamorphic blocks comprise dark schists, sandstones and conglomerates, possibly derived from Carboniferous-age strata from the Zone Houillere (Lombard, 1940) which are generally absent in the Voirons Sandstones. In contrast, the pink granite clasts, so typical of the coarse-grained lithologies observed in the Voirons Sandstones, are missing in the Vouan Conglomerates. Preliminary analyses (Table 2; Ragusa, 2009) show that the heavy-mineral assemblage is dominated by garnet. The thick cobbly/pebbly sandstone beds are massive and commonly show erosional bases and load casts. Normal and inverse grading occur, but clasts are, in general, randomly distributed within beds. Facies F1 to F7 of Mutti (1992) have been observed in the Vouan Conglomerates, Facies F1, F2 (Fig. 5D) and F5 being the most frequent ones. As mentioned above, shaly intervals are scarce in the Vouan Conglomerates and only one sample from the Curseilles creek has so far yielded a sizeable planktonic foraminiferal assemblage. It includes Acarinina sp., A. cf. bullbrooki (reworked), Globigerina cf. officinalis, Globoturborotalita ouachitaensis s.s., Globigerina cf. praebulloides, Globoturborotalita cf. ciperoensis (Fig. 6L) and Globoturborotalita ouachitaensis gnaucki indicating a Late Eocene to Early Oligocene age (planktonic foraminiferal zones P15 to P19).
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