Olten-Member

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Representation and status

Index
i6K
Color CMYK
siehe Balsthal-Formation
Color RGB
R: 170 G: 195 B: 215
Rank
lithostratigraphic Member (Subformation)
Validity
Unit is in Use
Status
valid formal name

Nomenclature

Deutsch
Olten-Member
Français
Membre d'Olten
Italiano
Membro d'Olten
English
Olten Member
Origin of the Name

Hardflue bei Olten (SO)

Historical Variants
Oltener Korallenkalk (Gygi 1969), Olten-Member (Gygi 2000b/c), Olten-Korallenkalk = Olten-Member (Bitterli et al. 2011)

Description

Description

Das Olten-Member besteht aus dickgebankten bis massiven Kalksteinen, 10 bis 20% bestehen aus plattigen Korallen (Dimorphoseris und Stylina), die Zwischenräume des Bioherms sind mit biodetritischem Mikrit gefüllt. Kiesel-Konkretionen kommen im mittleren Teil vor.

Thickness
26 m an der Typlokalität (Gygi 1969, Gygi 2000c); ca. 20 m (Bitterli et al. 2011)

Components

Fossil Content
  • sponges
  • corals
Dimorphoscris, Stylina, Microsolenidae

Hierarchy and sequence

Superordinate unit
Units at roof
Units at floor
Upper boundary
Letzte hermatypische Koralle
Lower boundary
Erste hermatypische Koralle.

Age

Age at top
  • late Oxfordian
Age at base
  • late Oxfordian
Dating Method
Implizite Datierung durch Liegendes und Hangendes

Geography

Geographical extent
3 bis 4 km breiter Streifen in südwestlicher-nordöstlicher Ausdehnung von einigen Kilometern
Type area
Olten und Umgebung
Type locality
  • Steinbruch Born (SO)
    Site particularities
    • Obergrenze
    • Untergrenze
    • typische Fazies
    Site accessibility
    • Steinbruch, Tongrube
    Coordinates
    • (2633900 / 1242280)
    Note
    • Gygi 2000c (nach Gygi 1969 Pl.18, Profil RG-21, Bänke 29-36 im Steinbruch 2.5 km südwestlich von Olten)
Type profile
  • Steinbruch Born (SO)
    Site particularities
    • Obergrenze
    • Untergrenze
    • typische Fazies
    Site accessibility
    • Steinbruch, Tongrube
    Coordinates
    • (2633900 / 1242280)
    Note
    • Gygi 2000c (nach Gygi 1969 Pl.18, Profil RG-21, Bänke 29-36 im Steinbruch 2.5 km südwestlich von Olten)

Palaenography and tectonic

  • Malm of the Jura Mountains
Paleogeography
Northern Tethyan Carbonate Platform :
Plateforme de Bourgogne, ... = Northern Tethyan Carbonate Platform (NTCP)
Tectonic unit (resp. main category)
Kind of protolith
  • sedimentary
Conditions of formation
Riffgürtel am Rand der raurazischen Plattform. Im späten Oxfordien wird der Plattformrand schliesslich durch das Korallenriff von Olten markiert.
Metamorphism
non metamorphic

References

Definition
Gygi R. A. (1969) : Zur Stratigraphie der Oxford-Stufe (oberes Jura-System) der Nordschweiz und des süddeutschen Grenzgebietes. Beitr. geol. Karte Schweiz N.F. 136, 143 Seiten

S.94: Korallenkalk
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.136: The Olten Member ("Oltener Korallenkalk") was named by Gygi (1969, p. 94). The name is derived from the city of Olten. LK 1088 Hauenstein, where the member forms a cliff on the northwestern slope of Hardflue hill above the railway goods yard of Olten (unpublished section RG 22, coordinates 635.550/244.980). Gygi (1969) did not designate a type locality.A complete section of the member is in the limestone quarry of the former cement works on the north slope of Mt. Born 2.5 km southwest of Olten that was measured by Gygi (1969. Pl. 18. section RG 21, coordinates 633.900/242.280). This quarry can serve as type locality. Beds 29-36 of section RG 21 are as signed to the Olten Member. The thickness of the Olten Member is 26 m in the type section. The lower part of the member is thick-bedded, whereas the upper part is massive. The matrix of the limestone is pure micrite below with varying admixtures of fine-grained biogenic detritus in the upper part. Chert nodules occur in the middle. 10-20% of the rock volume are mostly dish-shaped coral colonies of the genera Dimorphoscris and Stylina as well as undifferentiated microsolenids (Gygi 2000b. Fig. 12). The base of the member is where the first hermatypic corals appear, and the top where corals disappear. The geometry of the member is progradational (Gygi & Persoz 1986. PI. 1A). The most proximal individual patch reefs appear in the distal time equivalent of the Steinebach Member in the gorge 1 km northwest of Wangen near Olten. At the time of maximum development the coral limestone belt must have grown to a width of 3-4 km and may have been a bank reef. Gygi (1969. p. 95) pointed out that the reef front and the fore-reef ramp must have had a very subdued relief. Growth of the coral bank ceased during deposition of the upper Holzflue Member and the upper Letzi Member.
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