Letzi-Member

Torna a «Knollen-Bank»

Rappresentazione e statuto

Colore CMYK
siehe Villigen-Formation
Colore RGB
R: 185 G: 195 B: 215
Rango
Membro litostratigrafico (Sotto-formazione)
Uso
Unità in uso.
Status
termine formale valido

Nomenclatura

Deutsch
Letzi-Member
Français
Membre du Letzi
Italiano
Membro del Letzi
English
Letzi Member
Origine del nome

Hügel Letzi (AG) nord-östlich Effingen

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

Links

Synonymi
Wohlgeschichtete Kalke

Descrizione

Descrizione
Das Letzi-Member besteht aus gutgeschichteten, mikritischen Kalksteinen mit wenigen Bivalven und Ammoniten im oberen Teil der Villigen-Formation.
Potenza
10-15 m (de Tribolet 1872), ca. 20 m (Gygi 1969, Gygi 2000c)

Componenti

Fossili
  • ammoniti
  • bivalvi
Pholadomya

Gerarchia e successione

Unità di rango superiore
Unità sovrastante
Unità sottostante
Limite superiore
glaukonitisches Baden-Mb.
Limite inferiore
glaukonitische Knollen-Bank

Età

Geomorfologia
  • Primo Kimmeridgiano
Osservazioni sul tetto
Subnebrodites laxevolutus (Fontannes) (Gygi 2000b) und Sutneria galar (Oppel) (Gygi 1969)
Età alla base
  • Primo Kimmeridgiano
Osservazioni sulla base
Subnebrodites schroederi (Wegele) (Gygi 2000b)
Metodo di datazione
Biostratigraphie: Ammoniten der Planula-Zone bis Galar-Zone

Geografia

Estensione geografica
Aargauer Jura
Regione-tipo
Aargauer Jura
Località-tipo
  • Letzi (AG)
    Caratteristiche del sito
    • typische Fazies
    Agibilità del sito
    • verschwundener Aufschluss
    • Steinbruch, Tongrube
    Coordinate
    • (2652040 / 1262200)
    Nota
    • Hügel nord-östlich von Effingen (Gygi 2000c)
Sezione di riferimento
  • Mellikon (AG)
    Caratteristiche del sito
    • Obergrenze
    • Untergrenze
    • typische Fazies
    Agibilità del sito
    • Steinbruch, Tongrube
    Coordinate
    • (2668000 / 1268650)
    Nota
    • Gygi 1969 Pl.17 Profil RG70 Schichten 63-119

Paleogeografia e tettonica

  • Malm (Jura)
Paleogeografia
Swabian Basin
Termini generici
Tipo di origine
  • sedimentaria
Condizioni di formazione
"séquanien"
Metamorfismo
non metamorfo

Referenze

Definizione
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
Revisione
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).
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