Unterer Teil des Helvetischen Kieselkalkes (s.l.)

Rappresentazione e statuto

Colore CMYK

N/A

Colore RGB

R: 125 G: 125 B: 125

Rango

unità litostratigrafia

Uso

Unità non usata

Status

termine scoretto (abbandonato)

Nomenclatura

Deutsch

Unterer Teil des Helvetischen Kieselkalkes (s.l.)

Français

Partie inférieure du Kieselkalk Helvétique (s.l.)

English

Lower part of the Helvetic Kieselkalk (s.l.)

Varianti storiche

Untere Kieselkalkgruppe, Unterer Kieselkalk (Schindler 1959, Spörli 1966, Mojon 1982), Lower Kieselkalk (Föllmi et al. 2007)

Descrizione

Potenza

2-100 m (Mojon 1982); bis 500 m (Föllmi et al. 2007

Gerarchia e successione

Unità di rango inferiore

• Echinodermenbrekzie des Unteren Kieselkalkes
• Gebankte Abteilung des Unteren Kieselkalkes
• «Basisschiefer» des unteren Helvetischen Kieselkalkes

Età

Geomorfologia

• Primo Hauteriviano

Età alla base

• Valanginiano

Metodo di datazione

Ammoniten-Biostratigraphie der umrahmenden Einheiten (loryi-Zone und unterer Teil der nodosoplicatum-Zone (Föllmi et al. 2007)

Paleogeografia e tettonica

Termini generici

• Helvetic

Tipo di origine

• sedimentaria

Referenze

Revisione

Föllmi Karl B., Bodin Stephane, Godet Alexis, Linder Pascal, van de Schootbrugge B. (2007) : Unlocking paleo- environmental information from Early Cretaceous shelf sediments in the Helvetic Alps: stratigraphy is the key! Swiss J. Geosci. 100, 349-369

p.8: The lower Kieselkalk consists of an up to 500 m thick sandy, siliceous grain- to packstone dominated by crinoidal and bryozoan remains in proximal areas and by sponge spicules in distal areas. Sediments of this unit are typically heterozoan and rather coarse in proximal areas, whereas in distal areas fine-grained sediments dominate – especially at the base, where marls and/or micritic carbonates similar to the Diphyoides Formation prevail (Funk 1971; Felber and Wyssling 1979; Wyssling 1986; Kuhn 1996). The presence of channel structures and tempestite deposits is suggestive of a highly dynamic depositional environment in platform and platform slope areas. This is probably also indicated in the eastern, Vorarlberg part of the Helvetic zone, where sediments of the Helvetic Kieselkalk Formation are absent near the platform margin (Wyssling 1986).
The platform carbonate body of the lower Kieselkalk prograding on top of the Gemsmättli-Pygurus Complex probably represents a highstand systems tract, whereas in the outer shelf, the sediments correlated to this member may represent a more complete sequence.
The age of the lower Kieselkalk is well defined by the ages of the under- and overlying condensed and ammonite-rich beds and corresponds to the loryi and lower part of the nodosoplicatum zones.