Formation du Meilleret

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Representation and status

Index
fM
Color CMYK
(0%,0%,40%,2%)
Color RGB
R: 250 G: 250 B: 150
Rank
lithostratigraphic Formation
Validity
Unit is in Use
Status
valid formal name

Nomenclature

Deutsch
Meilleret-Formation
Français
Formation du Meilleret
Italiano
Formazione del Meilleret
English
Meilleret Formation
Origin of the Name

Tête de Meilleret (VD), au sud-ouest de Vers l'Eglise (Ormont-Dessus)

Historical Variants

flysch (Plan au Savioz, Meilleret) (Schardt 1896), Flysch (Perches, Riondel, Meilleret) = Flysch du Riondel = Flysch de La Croix-Perche-Fond d'Orsay (Sarasin & Collet 1907), grès et brèches polygéniques du Meilleret = Flysch de l'Encrènes = Flysch de l'Encrénaz et du Meilleret (Sarasin 1915), Flysch nummulitique du Meilleret-Ochsenweid (Lugeon 1938), Flysch éocène du Meilleret (Badoux 1970), Flysch du Meilleret (Homewood 1974, Badoux et al. 1990), Orsay Flysch (Homewood & Caron 1983), Meilleret Formation (Menkveld-Gfeller et al. 2016)

Nomenclatorial Remarks

McConnel 1951

Description

Description

Brèche polygénique grossière hétéométrique à éléments de roches cristallines vertes, surmontée de schistes argileux verdâtres à intercalations calcaires (Lombard 1975).

Thickness
60-210 m

Age

Age at top
  • Priabonian
Age at base
  • Lutetian
Dating Method

Nummulites (Lugeon 1938, Homewood 1974) et nannofossiles (Homewood 1976).

Geography

Geographical extent
Massif du Chamossaire: Le Perrey, Argnaules, La Truche / Tête de Meilleret, La Chaux et Vers-l'Eglise.

Palaenography and tectonic

  • Flyschs
Tectonic unit (resp. main category)
Kind of protolith
  • sedimentary
Conditions of formation

Dépôts de fan sous-marin de la marge méridionale du domaine Helvétique (Homewood 1977), alimenté par des sources situées plus au sud.

Metamorphism
non metamorphic

References

Definition
Lugeon Maurice (1938) : Quelques faits nouveaux dans les Préalpes internes vaudoises (Pillon, Aigremont, Chamossaire). Eclogae geol. Helv. 31/1, 1-20

p.6: Sur cet Aalénien très épais repose, en transgression, une masse énorme de flysch que nous appellerons le Flysch du Meilleret ... L'ensemble de la dalle complexe du Chamossaire avec son Trias à sa base repose mécaniquement sur un flysch que j'ai désigné plus haut sous le terme de Flysch du Meilleret, du nom d'une montagne dominant Vers l'Eglise.

Definition
Menkveld-Gfeller Ursula, Kempf Oliver, Funk Hanspeter (2016) : Lithostratigraphic units of the Helvetic Palaeogene: review, new definition, new classification. Swiss J. Geosc. 109/2, 171-199

p.192: Lugeon (1938) described the flysch deposits of the Meilleret nappe as ‘‘Flysch du Meilleret’’ named after the Tête de Meilleret SW of the village Vers l’Eglise. For further descriptions see McConnell and de Raaf (1929), McConnell (1951), Homewood (1974, 1976, 1977), and Badoux and Gabus (1991). The ‘‘Flysch du Meilleret’’ corresponds with the ‘‘Flysch d’Aigremont’’ (Lugeon 1938), the ‘‘Flysch d’Ochsenweid’’ (Lugeon 1938; Homewood 1974), and the ‘‘Höchst Flysch’’ (Ferrazzini 1981). The latter contains thickly bedded coarse-grained arenite and conglomerate and, according to benthic and planktonic foraminifera as well as nannofossils, has an age of Middle to Late Eocene. Hsu¨ and Briegel (1991) also assigned the ‘‘Adelbodner Flysch’’ and the ‘‘Leissigen Flysch’’ (both of the Lake Thun region) to Ultrahelvetic flysch deposits of Middle Eocene or probably Late Eocene age. We here define the Meilleret Formation as lithostratigraphic unit in contrast to the ‘‘Flysch du Meilleret’’, which may be used in a tectonic sense as well, similarly to the term ‘‘Blattengrat Flysch’’ etc. (see above). Lithology: Badoux and Gabus (1991) divided four lithofacies in the type region; these are: 10–15 m basal conglomerate characterized by sedimentary clasts in a sitly-marly matrix, approx. 50 m medium- to coarsegrained arkose sandstone, 50–100 m biogenic-detritic limetone, and polygenic conglomerate with a crystalline and sedimentary clast composition and a silty-sandy matrix. Undifferentiated, the Meilleret Formation may accumulate to 60–100 m thickness. The Meilleret Formation formed as submarine fan deposits along the southern margin of the Helvetic realm (Homewood 1977) and was fed by channels from a source area further to the south. These fan deposits, characterised by highly immature terrigenous clastic and shallow marine carbonate clasts, were built up during Middle to probably Late Eocene times. Locally, the Meilleret Formation contains conglomerate layers, which comprise large boulders (‘‘blocs exotics’’), and abundantly also nummulites. Clasts of pre-Triassic basement showing a wide variety of cristalline and metamorphic rock types (similar to those of the North Penninic Niesen Flysch) as well as of Mesozoic sediments of Ultrahelvetic and North Penninic origin, and contemporaneous shallow carbonate-shelf material, form boulder-size conglomerate beds and coarse lithic arenites, which were emplaced by a wide variety of tractional turbidity current and mass-flow processes (Homewood 1976). The nummulites, orthophragmines and Corallinacean fragments of the Meilleret Formation (Lugeon 1938) thus mark an important difference to the Niesen Flysch, which, in addition, had been deposited earlier. Overlying strata: tectonic boundary; underlying strata: Aalenian deposits. Biostratigraphy: Age of the nummulites: Lutetian (Homewood 1974, Lugeon 1938), locally rare nannofossils give an age of Priabonian (Homewood 1976). Current geographical extent: Western Switzerland: Col des Mosses– Diablerets–Adelboden. Tectonic units: Western Switzerland: Ultrahelvetic.

  • Flysch d'Iserin

    Name Origin

    Pâturage d'Iserin (VD)/(BE)

    Rank
    lithostratigraphic unit
    Status
    informal term
    In short
    Flysch éocène homologue de celui du Meilleret, constitué de conglomérat polygénique grossier à prédominance de galets cristallins verts.
  • «Calcaires organo-détritiques» (de la Fm. du Meilleret)

    Rank
    lithostratigraphic Member (Subformation)
    Status
    incorrect name (though informally used)
    In short

    Calcarénites ou calcirudites à bioclastes roulés (foraminifères, algues, bryozoaires, coraux) de la Formation de Meilleret.

    Age
    Lutetian
  • «Arkoses» (de la Fm. du Meilleret)

    Rank
    lithostratigraphic Member (Subformation)
    Status
    incorrect term (disused)
    In short

    Arkoses massives de la Formation de Meilleret, passant localement à des quartzites ou à des greywackes lithiques.

  • «Conglomérat basal» (de la Fm. du Meilleret)

    Rank
    lithostratigraphic Member (Subformation)
    Status
    incorrect name (though informally used)
    In short

    Conglomérat de la base de la Formation de Meilleret, dont les galets de la taille d'un poing, plus ou moins anguleux, proviennent essentiellement du Trias. Matrice silteuse ou marneuse.

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