Membre de la May

Retour à Membre de Bure

Représentation et statut

Couleur CMYK
cf. Formation de Courgenay
Couleur RGB
R: 155 G: 195 B: 215
Rang
Membre lithostratigraphique (Sous-formation)
Usage
Ce terme est en usage.
Status
terme formel valide

Nomenclature

Deutsch
La-May-Member
Français
Membre de la May
Italiano
Membro della May
English
La May Member
Origine du nom

Petite vallée de La May, 2.5 km NE de St-Ursanne (JU)

Variantes historiques

Humeralis-Kalke auct., La May-Schichten (Gygi 1995 S.12), La May Member (Gygi 2000c)

Description

Description

Calcaire micritique, bien lité, pas d’ammonites mais des bivalves (Pholadomya). yellow, "spary-oolithic" limestone

Épaisseur
20-30 m (Aufranc et al. 2016), 31 m à Courgenay (Gygi 2000c)

Composants

Fossiles
  • brachiopodes

Hiérarchie et succession

Unité hiérarchiquement supérieure
Unités sus-jacentes
Unités sous-jacentes
Limite supérieure

Calcaire massifs du Mb. de Porrentruy. Limite supérieure difficile à repérer (év. lumachelle d'huîtres perforées, ecroûtées et teinteées de rouge).

Limite inférieure

Marnes du Mb. de Bure (masqué)

Âge

Âge au sommet
  • Kimméridgien précoce
Âge à la base
  • Oxfordien tardif
Méthode de datation

Coulée de débris

Géographie

Extension géographique
Nord de la suisse
Région-type
Canton du Jura
Localité-type
  • La May (JU)
    Particularités du site
    • typische Fazies
    Coordonnées
    • (2580750 / 1247500)
    Note
    • Petite vallée 2.5 km NE de St-Ursanne (Gygi 2000b/c Profil RG337)
Coupes de référence
  • La Coperie (JU)
    Particularités du site
    • Obergrenze
    • Untergrenze
    • typische Fazies
    Accessibilité du site
    • Bohrkern
    Coordonnées
    • (2580900 / 1246230)
    Note
    • forage d'exploration de la Transjurane (Gygi 2000b Pl.20 Profil RG443)

Paléogéographie et tectonique

Termes génériques
Type de protolithe
  • sédimentaire
Métamorphisme
non métamorphique

Références

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

S.12
Révision
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: 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.

p.134: La May Member (Gygi 1995) ; Previously "Humeralis-Kalke". Member of the Courgenay Formation ; Synonymy: Gygi (2000b, p. 61)

The La May Member was named by Gygi (1995. p. 12). The name refers to the small valley called La May 2.5 km northeast of St-Ursanne in Canton Jura. LK 1085 St-Ursanne. where part of the member crops out at coordinates ca. 580.750/247.500 in the unpublished section RG 337. Below is the marl of the Bure Member which is covered, and above is a good outcrop of the massive Porrentruy Member. The only complete section of the La May Member was provided by the exploration well for the Transjurane superhighway near La Coperie farm 2 km east of St-Ursanne. This is section RG 443 which is represented as plate 20 in Gygi (2000b). The limestone of the La May Member is mostly micritic, well-cemented and well-bedded. Rounded lithoclasts of micrite grow to a diameter of 10 mm and are not rare. Macrofossils are Cycloserpula socialis (Goldfuss) and the bivalve Pholadomya. The thickness of the member is about 30 m in the borehole near La Coperie that Gygi (2000b p. 61) proposed to be the type section for lack of a complete outcrop at the surface. No ammonites have been found in the La May Member to date. The clay mineral stratigraphy by Gygi & Persoz (1986. Pl. 1A) indicates that the age of the La May Member ranges from the Hauffianum Subchron ofthe Bimammatum Chron to the lower Planula Chron (Gygi. 1995. Fig. 2). The La May Member occurs only in Canton Jura. The boundaries of the member with the Laufen and Verena Members are transitional.
haute de page