«Membre argilitique»

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Representation and status

Color CMYK
(0%,0%,0%,100%)
Rank
lithostratigraphic Member (Subformation)
Validity
Unit is in Use
Status
informal term

Nomenclature

Deutsch
«Toniges Member»
Français
«Membre argilitique»
Italiano
«Membro argiloso»
English
«Argillite Member»
Origin of the Name

argile - Ton

Historical Variants

Schistes argilo-ferrugineux rouge et vert (Favre in: Gerlach 1871), Schistes rouges et verts (de Loys 1928), argilites gréseuses et multicolores (Amberger 1960), Membre argilitique (Epard 1989 p.307), Argilites versicolores (Pairis et al. 1992), argillite member = fine-grained unit of thin-bedded sandstone and shale (Klein et al. 2016), argiolites inférieurs

Description

Thickness
2-6 m (Epard 1989), 5-10 m (de Loys 1928)

Hierarchy and sequence

Superordinate unit

Age

Age at top
  • Anisian
Age at base
  • Anisian
Dating Method

Niveau à empreintes à la transition avec le membre sous-jacent (Klein et al. 2016).

Palaenography and tectonic

  • Triassic of the Helvetics
Tectonic unit (resp. main category)
Kind of protolith
  • sedimentary
Conditions of formation

Le membre argilitique correspond à des sédiments de baie protégée (Epard 1989).

References

Definition
Epard Jean-Luc (1989) : Stratigraphie du Trias et du Lias dauphinois entre Belledonne, Aiguilles-Rouges et Mont-Blanc. Bull. Soc. vaud. Sci. nat. 79/4, 301-338

p.307: La Formation du Vieux Emosson est une série détritique que nous divisons en deux membres (fig. 4 et 5). Elle comprend à la base un membre gréseux composé de conglomérats, arkoses et grès, passant progressivement vers le haut à un membre argilitique, formé de pélites vertes, noires, jaunes ou rouges. La Formation du Vieux Emosson correspond à la série décrite comme grès conglomératique, grès calcaires et quartzitiques, grès fins et argilites vert-jaune, et argilites rouges de la fig. 3, p. 727 de Demathieu et Weidmann (1982). Ces sédiments montrent des figures sédimentaires telles que rides d'oscillation, stratifications entrecroisées et polygones de dessication.

Definition
Klein Hendrik, Wizevich Michael C., Thüring Basil, Marty Daniel, Thüring Silvan, Falkingham Peter, Meyer Christian A. (2016) : Triassic chirotheriid footprints from the Swiss Alps: ichnotaxonomy and depositional environment (Cantons Wallis & Glarus). Swiss J. Palaeontol. 135, 295–314

p.300: The fine-grained unit is a generally fining- and thinning-upward sequence of interbedded thin, rippled sandstone and mudstone beds, up to 7 m thick. Rippled sandstones are thin-bedded (cm- to dm-scale), coarse to fine-grained, and contain abundant current and wave ripple marks, small-scale cross stratification, mudcracks, mudstone rip-up clasts, and rare load casts.

The mudstones consist of red and green laminated mudstone with very thin (\cm) fine- to medium-grained sandstone layers. Where well exposed, the mudstone and very thin sandstone beds comprise 20–50 cm thick fining- and thinning-upward sequences nested within the fine-grained unit. Microscopic examination of the mudstones that appear to be devoid of sandstone reveals mm-scale, erosionally based, fining-upward (very fine sand to clay) lamina. Mudcracks and starved ripples are common. Palaeosols defined by texturally mottled and crinkly laminations (bioturbation?) and dolomitic nodules are rare.

Dolomite beds, up to 5 cm thick, are very fine-grained, weakly laminated, and are interbedded with the mudstones at the top of the fine-grained unit. In some areas, the dolomite beds contain extensive desiccation fractures.

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