Membre de la May
Back to Membre de PorrentruyRepresentation and status
- Color CMYK
- cf. Formation de Courgenay
- Color RGB
- R: 155 G: 195 B: 215
- Rank
- lithostratigraphic Member (Subformation)
- Validity
- Unit is in Use
- Status
- valid formal name
Nomenclature
- Deutsch
- La-May-Member
- Français
- Membre de la May
- Italiano
- Membro della May
- English
- La May Member
- Origin of the Name
-
Petite vallée de La May, 2.5 km NE de St-Ursanne (JU)
- Historical Variants
-
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
- Thickness
- 20-30 m (Aufranc et al. 2016), 31 m à Courgenay (Gygi 2000c)
Components
- brachiopods
Hierarchy and sequence
- Superordinate unit
- Units at roof
- Units at floor
- Upper boundary
-
Calcaire massifs du Mb. de Porrentruy. Limite supérieure difficile à repérer (év. lumachelle d'huîtres perforées, ecroûtées et teinteées de rouge).
- Lower boundary
-
Marnes du Mb. de Bure (masqué)
Age
- Age at top
-
- Early Kimmeridgian
- Age at base
-
- late Oxfordian
- Dating Method
-
Coulée de débris
Geography
- Geographical extent
- Nord de la suisse
- Type area
- Canton du Jura
- Type locality
-
-
La May (JU)
Site particularities- typische Fazies
- (2580750 / 1247500)
- Petite vallée 2.5 km NE de St-Ursanne (Gygi 2000b/c Profil RG337)
-
La May (JU)
- Reference profiles
-
-
Forage de La Coperie (JU)
Site particularities- Obergrenze
- Untergrenze
- typische Fazies
- Bohrkern
- (2580900 / 1246230)
- <p>Forage d'exploration de la Transjurane (Gygi 2000b Pl.20 Profil RG443)</p>
-
Forage de La Coperie (JU)
Palaenography and tectonic
- Tectonic unit (resp. main category)
-
-
Jura
:
Juragebirge
-
Jura
:
- Kind of protolith
-
- sedimentary
- Metamorphism
- non metamorphic
References
- Definition
-
(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.