Membre de Sornetan

Back to Formation du Pichoux

Representation and status

Index
i4-5S
Color CMYK
cf. Formation de Bärschwil
Color RGB
R: 170 G: 175 B: 120
Rank
lithostratigraphic Member (Subformation)
Validity
Unit is in Use
Status
valid formal name
Status discussion

Nomenclature

Deutsch
Sornetan-Member
Français
Membre de Sornetan
Italiano
Membro di Sornetan
English
Sornetan Member
Origin of the Name

Gorges du Pichoux au nord-ouest de Sornetan (BE)

Historical Variants

«Terrain à chailles» auct., Sornetan Member (Gygi 2000b, Gygi 2000c), Membre de Sornetan (Aufranc et al. 2017)

Description

Description

Grauer, mergeliger Ton mit Lagen von Kalkkonkretionen, die nach oben häufiger werden, führt Ammoniten, Bivalven, Echiniden, Crinoiden.

Thickness
46 m bei Liesberg, 37,5 m in Anwil.

Components

Fossil Content
  • ammonites
  • crinoids
  • belemnites
  • echinoids
  • bivalves

Pholadomyen

Hierarchy and sequence

Superordinate unit
Units at roof
Units at floor
Upper boundary

L'apparition des premiers coraux définit la base du Mb. de Liesberg sus-jacent.

Lower boundary

Passage progressif.

Age

Age at top
  • middle Oxfordian
Age at base
  • middle Oxfordian
Dating Method

Ammonites: Zones à Cordatum et à Transversarium-Zone (Gygi & Marchand 1993, Gygi 1995)

Geography

Geographical extent
NW-Schweiz, siehe Karte Gygi 1990c, Fig. 2 - 4
Type area
NW Schweiz
Type profile
Reference profiles
  • Hinter Chestel (BL)
    Site particularities
    • Obergrenze
    • Untergrenze
    • typische Fazies
    Site accessibility
    • Steinbruch, Tongrube
    Coordinates
    • (2599550 / 1249500)
    Note
    • Gygi 2000b, Profil RG-306, Pl.21
Point of interest

Palaenography and tectonic

  • Malm
Tectonic unit (resp. main category)
Kind of protolith
  • sedimentary
Sequence

Within this interval, the content in fossil debris slightly increases up to the so-called “fossil-rich bed”, which is located roughly in the middle of the Terrain à Chailles. [...] In the mud-dominated

Terrain à Chailles, maximum quartz content as well as

abundant serpulids appear to characterize SB Ox3. Levels

rich in ferroan calcite cement and glauconite indicating slow

sedimentation are interpreted as flooding or maximum-flooding

surfaces. (Wetzel & Strasser 2001)

Metamorphism
non metamorphic

References

Definition
Gygi R. A. (2000) : Integrated stratigraphy of the Oxfordian and Kimmeridgian (Late Jurassic) in northern Switzerland and adjacent southern Germany. Denkschriften der Schweizerischen Akademie der Naturwissenschaften 104, 152 S.

p.53

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.127: The Sornetan Member in the middle is a gray marl with ellipsoidal carbonate nodules, ammonites and bivalves, about 45 m thick.

p.140

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