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Representation and status

Color CMYK
Color RGB
R: 250 G: 220 B: 130
lithostratigraphic Member (Subformation)
Unit is in Use
valid formal name


Membre de Therwil
Membro di Therwil
Therwil Member
Origin of the Name

Therwil (BL)

Historical Variants

Horizont / Bank mit Ostrea cyathula (Gutzwiller 1914, Herzog 1956, Bitterli-Brunner & Fischer 1988), Cyathulabank (Koch 1923, Bitterli 1945, Fischer 1965a, Naef et al. 1985, Picot 2002, Becker 2003, Grimm 2005, Picot et al. 2008), Therwil Member (Pirkenseer et al. 2018)

Nomenclatorial Remarks

Un horizon à Crassostrea cyathula existe également dans le bassin de Delémont, mais dans des niveaux plus anciens (Membre des Près Roses de la Formation de Lörrach).


Généralement 2 m dans la région bâloise (Pirkenseer et al. 2018).

Hierarchy and sequence

Superordinate unit
Units at roof
Units at floor


Geographical extent
Partie méridionale du fossé du Haut-Rhin dans la région bâloise (Therwil, Ettingen) et extrême nord du bassin de Laufon (Brislach).
Type area
Région bâloise (BL)

Palaenography and tectonic

Rhine Graben
Tectonic unit (resp. main category)
Kind of protolith
  • sedimentary


Pirkenseer Claudius, Rauber Gaëtan, Roussé Stéphane (2018) : A revised Palaeogene lithostratigraphic framework for the Northern Swiss Jura and the Southern Upper Rhine Graben and its relationship to the North Alpine Foreland Basin. Riv. Italiana Pal. Strat. 124/1, 163–246

p.214: The Therwil Mb is dominated by disarticulated valves of Crassostrea cyathula, which either form a densely packed, sometimes sandy coquina or are distributed in a matrix of mainly bluish grey, massive marls. In the area of Basel the member seems to be developed as a relatively continuous bed of maximal 2 (possibly to 5) m thickness that pinches out near Brislach (30 cm; Koch 1923) in the Laufen subbasin.
Gutzwiller (1893) indicates a continuous occurrence of the coquina bed between the villages Therwil and Ettingen (at least 4 km). Towards the north and the west the bed dissolves into oyster patch “reefs”, isolated valves in massive marls or is entirely absent (e.g. drilling Hirtzbach; Vonderschmitt 1942).

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