Homomyenmergel

Representation and status

Index

i2H

Color CMYK

siehe Hauptrogenstein

Color RGB

R: 190 G: 165 B: 115

Rank

lithostratigraphic Member (Subformation)

Validity

Unit is in Use

Status

incorrect name (though informally used)

Scs Note

Bei Gonzalez (1993) als Formationsglied = Member definiert.

Nomenclature

Deutsch

Homomyenmergel

Français

Marne à Homomyes

Italiano

Marna da Homomya

English

Homomya Marl

Origin of the Name

Namengebendes Fossil (Bivalvia): Homomya gibbosa Agassiz (Gruppe der Pholadomyen).

Historical Variants

Homomyenmergel (Gressly 1855, Desor & Gressly 1859, Greppin 1870, Mühlberg 1900, Baltzer 1906, Buxtorf & Troesch 1917, Disler 1941), Marnes à Homomyes (Aufranc et al. 2017), Homomyen-Mergel (Gonzalez 1993), Homomya Marls (Gonzalez & Wetzel 1996)

Description

Description

Wechsellagerung von intensiv rotbraun verwitterndem Mergel und spätigem Kalk, die in einzelnen Lagen massenhaft die kleine Auster Ostrea acuminata neben anderen Muscheln (insbesondere Pholadomyen) und Brachiopoden (darunter Terebratula furcilensis und T. movelierensis (CHAUVE & BAILLY 1985)), sowie Belemniten und Parkinso-nia sp. enthält.

Geomorphology

Zurückwitternde Balme oder Terrasse. Oft schlecht aufgeschlossen.

Thickness

5 – 15 m (Gonzalez & Wetzel 1996)

Components

• ammonites
• ostreids
• bivalves

Homomya gibbosa Agassiz (Pholadomyen), Ostrea acuminata, Parkinsonia acris Wetzel, Parkinsonia subarietis Wetzel

Hierarchy and sequence

Superordinate unit

• Hauptrogenstein [CH]

Units at roof

• «Obere Oolithische Serie» (Grande Oolithe s.s.)
• Oberer Teil des Hauptrogensteins

Units at floor

• Mittlerer Hauptrogenstein (sensu Schmassmann 1945)
• Unterer Teil des Hauptrogensteins
• «Maeandrina-Schichten»

Upper boundary

Allmähliche Zunahme der oolithische und spätige Kalkbänke.

Age

Age at top

• late Bajocian

Age at base

• late Bajocian

Dating Method

Biostratigraphie: Ammoniten der Acris Subzone (frühe Parkinsoni Zone ; Gonzalez & Wetzel 1996); früheste Parkinsoni-Zone (Gruner et al. 2013)

Geography

Geographical extent

Westlicher Jura (Westlich der Linie Challpass – Erschwil – Passwang – Oberbipp).

Type profile

• Tunnel des Loges (JU)
  Coordinates
  • (2556760 / 1214490)
  Note
  • <p>Tunnel des Loges (am Mont Perreux, bei La Chaux-de-Fonds), nahe Ventilationsschacht No.5 (Gonzalez 1993)</p>

Palaenography and tectonic

Paleogeography

Northern Tethyan Carbonate Platform :
Plateforme de Bourgogne, ... = Northern Tethyan Carbonate Platform (NTCP)

Tectonic unit (resp. main category)

• Jura :
  Juragebirge

Kind of protolith

• sedimentary

Conditions of formation

Offenmarines, epikontinentales Meer, Beckensedimentation.

Metamorphism

non metamorphic

References

Definition

Gonzalez R., Wetzel A. (1996) : Stratigraphy and paleogeography of the Hauptrogenstein and Klingnau Formations (middle Bajocian to late Bathonian), northern Switzerland Eclogae geol. Helv. 89/2, 695-720

p.708: The Homomya Marls separate the Lower from the Upper Oolitic Series in the western Jura, forming the base of the second shallowing-upward succession (Fig. 4). Their thickness varies between 5 and 15 m (values included in Fig. 5b). They consist of alternations of cm to m thick marls with bioclastic. sometimes oolitic and oncolitic limestones. Characteristic are large bivalves, such as Homomya and Pholadomya.