Bifertengrätli-Formation

Representation and status

Index

hB

Color CMYK

40 / 20 / 40 / 0

Color RGB

R: 160 G: 180 B: 160

Rank

lithostratigraphic Formation

Validity

Unit is in Use

Status

valid formal name

Status discussion

Nomenclature

Deutsch

Bifertengrätli-Formation

Français

Formation du Bifertengrätli

Italiano

Formazione del Bifertengrätli

English

Bifertengrätli Formation

Origin of the Name

Bifertengrätli (GL), am Tödi

Historical Variants

Quarzporphyr auct., Bifertengrätliserie = Bifertengrätlischichten (Widmer 1949), Bifertengrätli-Serie (Rutsch et al. 1966), Bifertengrätli Formation (Franks 1968 p.59, Berger et al. 2017), Karbon?sedimente = Oberkarbon = Bifertengrätliformation (Pfiffner 1972), Bifertengrätliformation (Böhm 1986)

Description

Description

Vulkanische und sedimentäre Gesteine. Details siehe einzelne Members. Conglomerates, breccias and coarse sandstones are the most abundant sediments and many of these coarse clastic rocks contain a large amount of volcanic debris…

Components

• plants : Plantae

Calamites suckowi Bgt., Annularia stellata Schl., Pecopteris aus der Gruppe der P. cyathea Schl., P. arborescens Schl., P. plumosa Artis, Linopteris münsteri Eichw., Neuropteris ovata Hoffm., Cyclopteris cf. trichomanoides Bct. (Jongmans 1950)

Hierarchy and sequence

Superordinate unit

• Spät- bis postvariszische Sedimente und Vulkanite des Aar-Massivs

Subordinate units

• Sandalp-Rhyolith
• «Lacustrine Member»
• «Estuarine Member»
• Grünhorn-Member
• «Basiskonglomerat» (Bifertengrätli-Fm.)

Age

Age at top

• Late Pennsylvanian

Note about top

frühestes Stephanien

Age at base

• Late Pennsylvanian

Note about base

Westphalien D

Dating Method

Pflanzen des Westphalien-D bis frühestes Stéphanien am Tödi (Escher 1911, Jongmans 1950 und 1960).

Geography

Geographical extent

Aarmassiv im Gebiet Sandalp-Bifertengrätli.

Type area

Tödi (GL/GR)

Palaenography and tectonic

Paleogeography

European continental plate

Tectonic unit (resp. main category)

• Aar

Kind of protolith

• sedimentary
• volcanic

References

Definition

Berger Alfons, Mercolli Ivan, Herwegh Marco, Gnos Edwin (2017) : Geological Map of the Aar Massif, Tavetsch and Gotthard Nappes. Geological Special Map 1:100'000, Explanatory Notes 129

p.48: The Bifertengrätli Formation represents a key unit for the understanding of the lithostratigraphic architecture of the Late Carboniferous sequences and the evolution of the late Variscan deformation history (Fig. 6, HÜGI 1941, WIDMER 1949, FRANKS 1966, 1968 a, b). In addition to a detailed description of the stratigraphic sequence and the reconstruction of the different volcanic and sedimentary facies, FRANKS (1966, 1968 a, b) elaborated the age relationships between the different units outcropping in the Tödi area. Based on this study it was concluded that the Bifertengrätli Formation is younger than the Tödi Granite Complex, that the Bifertenfirn Formation (p. 34) is older than the Tödi Granite Complex as indicated by intrusive contacts, and that the Bifertenfirn Formation was deformed and metamorphosed before the intrusion of the Tödi Granite Complex. At this locality, the Variscan chronology in the Central Alps was constrained: fossil plants, dated by JONGMANS (1960) as Pennsylvanian (Westphalian D–Stephanian), were found in the sandstone of the Bifertengrätli Formation.