Letzi-Member

Representation and status

Color CMYK

siehe Villigen-Formation

Color RGB

R: 185 G: 195 B: 215

Rank

lithostratigraphic Member (Subformation)

Validity

Unit is in Use

Status

valid formal name

Nomenclature

Deutsch

Letzi-Member

Français

Membre du Letzi

Italiano

Membro del Letzi

English

Letzi Member

Origin of the Name

Hügel Letzi (AG) nord-östlich Effingen

Historical Variants

Letzischichten (Escher von der Linth in: Moesch 1863, Tobler 1905 Tab.3a/4a, Hantke 1967), couches de la Letzi (de Tribolet 1872), Letzi Schichten = Zone à Peltoceras bicristaum p.p. (Haug 1911), Letzi-Schichten, Letzi Member (Gygi 2000c)

Nomenclatorial Remarks

Anstelle der ursprünglichen, nicht mehr zugänglichen Typlokalität schlägt Gygi (1969) als neue Typlokalität den Steinbruch von Mellikon vor (Koordinaten: 668.415/268.600).

Links

Synonyms

Wohlgeschichtete Kalke

Description

Description

Das Letzi-Member besteht aus gutgeschichteten, mikritischen Kalksteinen mit wenigen Bivalven und Ammoniten im oberen Teil der Villigen-Formation.

Thickness

10-15 m (de Tribolet 1872), ca. 20 m (Gygi 1969, Gygi 2000c)

Components

• ammonites
• bivalves

Hierarchy and sequence

Superordinate unit

• Villigen-Formation

Units at roof

• Baden-Member
• Burghorn-Formation
• Formation de Reuchenette

Units at floor

• Wangen-Member (sensu Gygi 1969)

Upper boundary

glaukonitisches Baden-Mb.

Lower boundary

glaukonitische Knollen-Bank

Age

Age at top

• Early Kimmeridgian

Note about top

Subnebrodites laxevolutus (Fontannes) (Gygi 2000b) und Sutneria galar (Oppel) (Gygi 1969)

Age at base

• Early Kimmeridgian

Note about base

Subnebrodites schroederi (Wegele) (Gygi 2000b)

Dating Method

Biostratigraphie: Ammoniten der Planula-Zone bis Galar-Zone

Geography

Geographical extent

Aargauer Jura

Type area

Aargauer Jura

Type locality

• Letzi (AG)
  Site particularities
  • typische Fazies
  Site accessibility
  • verschwundener Aufschluss
  • Steinbruch, Tongrube
  Coordinates
  • (2652040 / 1262200)
  Note
  • Hügel nord-östlich von Effingen (Gygi 2000c)

Reference profiles

• Mellikon (AG)
  Site particularities
  • Obergrenze
  • Untergrenze
  • typische Fazies
  Site accessibility
  • Steinbruch, Tongrube
  Coordinates
  • (2668000 / 1268650)
  Note
  • Gygi 1969 Pl.17 Profil RG70 Schichten 63-119

Palaenography and tectonic

• Malm of the Jura Mountains

Paleogeography

Swabian Basin

Tectonic unit (resp. main category)

• Jura :
  Juragebirge

Kind of protolith

• sedimentary

Conditions of formation

"séquanien"

Metamorphism

non metamorphic

References

Definition

Moesch Casimir (1863) : Geologische Beschreibung des Aargauer-Jura und der nördlichen Gebiete des Kantons Zürich. Beitr. geol. Karte Schweiz 4, 349 Seiten

Escher von der Linth

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.135: Letzi Member (Moesch 1863) ; Member of the Villigen Formation According to Moesch (1863. p. 164/165). Escher von der Linth originally proposed the name Letzi Member (Letzischichten). The name refers to the hill called Letzi 2.5 km northeast of the village of Effingen. Canton Aargau. LK 1069 Frick. A small quarry was opened in the Letzi Member 100 m east of the now demolished farm Letzi in the 19th century in order to provide for lithographic limestone (coordinates 652.040/262.200) which is the type locality. The outcrop does not exist any more. The Letzi Member is a well-bedded, pure micritic limestone with a mean thickness of about 20 m (Gygi 1969. pl 17). Macrofossils are uncommon, but some bivalves (Pholadomya) and ammonites were found. The Letzi Member is underlain by the glauconitic Knollen Bed and overlain by the glauconitic Baden Member. The upper part of the Letzi Member could be dated with a Subnebrodites laxevolutus (Fontannes) in the large quarry at Mellikon. Canton Aargau (Gygi 2000b. Pl. 11, Fig. 4) at the Planula Chron ofthe early Kimmeridgian. Sutneria galar (Oppel) J 32809 occurs in the uppermost two meters of the Letzi Member (bed 114. Gygi 1969. Pl. 17. section RG 70). Thanks to the Knollen Bed marker, the Letzi Member can be exactly correlated lithostratigraphically with the Wangental Member in Canton Schaffhausen. Gygi (1969. Pl. 16, section RG 82) found Subnebrodites schroederi (Wegele) J 31714 in bed 134 of the section directly above the base of the Wangental Member. The specimen is figured in Gygi (2000b. Pl. 13 Fig. 4). Consequently, the age ofthe Letzi Member is the Planula Chron. A good reference section of the member are beds 63-119 of section RG 70 at Mellikon. Canton Aargau. which is figured by Gygi (1969. Pl. 17).