Formation de Courgenay

Representation and status

Index

i6C

Color CMYK

40 / 10 / 10 / 0

Color RGB

R: 160 G: 200 B: 220

Rank

lithostratigraphic Formation

Validity

Unit is in Use

Status

valid formal name

Status discussion

Nomenclature

Deutsch

Courgenay-Formation

Français

Formation de Courgenay

Italiano

Formazione di Courgenay

English

Courgenay Formation

Origin of the Name

Courgenay (JU)

Historical Variants

Humeralis-Kalke auct., Courgenay-Formation (Gygi 1995 S.12), Courgenay Formation (Gygi 2000b, Gygi 2000c)

Links

Synonyms

Formation de Court

Description

Description

La formation est constituée d’une succession de calcaires micritiques lités (Membre de la May) et de calcaires massifs de couleur blanchâtre plus ou moins crayeux, parfois décrits comme calcaires massifs oolithiques (Membre de Ste-Vérène). Ils forment très souvent des parois ou des falaises.

Geomorphology

Forme très souvent des parois ou des falaises.

Thickness

30-40 m, max. 50 m à la transition avec la Fm. de Balsthal (Aufranc et al. 2016).

Hierarchy and sequence

Subordinate units

• Membre de Porrentruy
• Membre de la May

Units at roof

• Formation de Reuchenette

Units at floor

• Formation de Vellerat

Upper boundary

Formation de Reuchenette

Lower boundary

Marnes du Membre de Bure (Formation de Vellerat)

Age

Age at top

• Early Kimmeridgian

Age at base

• late Oxfordian

Note about base

Zone à Bimammatum: Sous-zone à Hauffianum

Dating Method

Minéralogie des argiles (Gygi & Persoz 1986 Pl.1a).

Geography

Geographical extent

Ajoie, Canton du Jura.

Type area

Ajoie (JU)

Type locality

• Courgenay/Iennsdorf (JU)
  Coordinates
  • (2576450 / 1250200)

Type profile

• Courgenay (JU)
  Site particularities
  • typische Fazies
  Site accessibility
  • Strassenanschnitt / Bahnanschnitt
  Coordinates
  • (2573790 / 1247100)
  Note
  • Chemin Paulin, 4 km SW Courgenay (Gygi 2000b Pl.19 Profil RG350, Gygi 2000c)

Palaenography and tectonic

• Malm

Tectonic unit (resp. main category)

• Jura :
  Juragebirge

Kind of protolith

• sedimentary

Conditions of formation

Plateforme interne, faciès lagunaire.

Metamorphism

non metamorphic

References

Definition

Gygi R. A. (1995) : Datierung von Seichtwassersedimenten des Späten Jura in der Nordwestschweiz mit Ammoniten Eclogae Geol. Helv. 88/1, 1-58

S.12

Definition

Gygi R. A. (2000) : Annotated index of lithostratigraphic units currently used in the Upper Jurassic of northern Switzerland. Eclogae geol. Helv. 93/1, 125-146

p.129: Courgenay Formation (Gygi 1995) ; Previously: "Humeralis-Kalke" ; Synonymy: Gygi (2000b, p. 60) Gygi (1995. p. 12) proposed the Courgenay Formation for the lagoonal limestones between the marly Vellerat Formation below and the Reuchenette Formation above. The name refers to the village of Courgenay in the southern Ajoie region of Canton Jura. The type section is RG 350 along the road called Chemin Paulin (name not indicated on the map) 4 km southwest of the village at coordinates 573.790/247.100. LK 1085 St-Ursanne. The section is represented as plate 19 in Gygi (2000b). The Courgenay Formation has two members. The La May Member below is a well-bedded micritic limestone with a thickness of 31 m in the section RG 350 at Chemin Paulin. Above follows the Porrentruy Member, an almost pure white, massive micritic limestone which is 13 m thick in the reference section that is RG 350. No ammonites were found to date in the Courgenay Formation. It is only with clay minerals that it can be shown that the Porrentruy Member is coeval with the Letzi Member in Canton Aargau (correlation K by Gygi & Persoz 1986. Pl. 1 A). The Letzi Member can be dated with ammonites as earliest Kimmeridgian. The Courgenay Formation grades distally, between St-Ursanne and Glovelier, Canton Jura, into the oolitic Balsthal Formation that includes the "Court Formation" of Bolliger & Burri (1970. p. 73). Gygi (2000b. p. 61 showed that the Court Formation is a junior synonym of the Balsthal Formation and is therefore a superfluous term.

Material and varia

15200003