strati.ch - Lexique lithostratigraphique de la Suisse

Représentation et statut

Variantes historiques: Mergelhorizont III (Merki 1961), Dünnlenberg Bed (Pietsch et al. 2016)

Unité hiérarchiquement supérieure

Âge au sommet

Note sur le sommet

Illyrien, Compressus- bis Evolutus-Zone

Âge à la base

Note sur la base

Illyrien, Compressus- bis Evolutus-Zone

Méthode de datation: Ceratiten-Biostratigraphie: Compressus- bis Evolutus-Zone (Pietsch et al. 2016).

Extension géographique: Baselbieter und Aargauer Tafeljura, Faltenjura westlich Schinznach, Wutachgebiet.

Paléogéographie

plateforme carbonatée nord-téthysienne :
Plateforme de Bourgogne, ... = Northern Tethyan Carbonate Platform (NTCP)

Termes génériques

Type de protolithe

Définition: Pietsch Johannes S., Wetzel Andreas, Jordan Peter (2016) : A new lithostratigraphic scheme for the Schinznach Formation (upper part of the Muschelkalk Group of northern Switzerland). Swiss J. Geosc. 109/2, 285-307

The Dünnlenberg Bed consists of grey or brownish marl, which can be dolomitic or calcareous. It lies within the upper part of the strata rich in crinoid and shell detritus, where macrofossil-poor mud- and wackestones and intervals only rich in shell detritus gradually and diachronously replace this facies. Therefore, it may belong to either the Kienberg Member or the Liedertswil Member. Although many outcrops show several marly horizons, only the lowermost horizon, which is thicker than about 5 cm is defined as Dünnlenberg Bed (Figs. 10, 11). In northern Switzerland ceratites were only found in the Dünnlenberg Bed and in the overlying marl of the uppermost part of the Kienberg Member (see biostratigraphic discussion). In gamma-logs the Dünnlenberg Bed is characterised by a positive peak (Figs. 10, 11). While the Leutschenberg Member and the Kienberg Member are characterised by decreasing clay content (Figs. 10, 15) the Dünnlenberg Bed often represents the first significant peak. Locally mostly less pronounced peaks may occur further up (e.g. Schafisheim; Fig. 15), which may correspond to the marl- and glauconite-bearing strata overlying the Dünnlenberg Bed.

Révision: Jordan Peter (2016) : Reorganisation of the Triassic stratigraphic nomenclature of northern Switzerland: overview and the new Dinkelberg, Kaiseraugst and Zeglingen formations. Swiss J. Geosci. 109/2, 241-255

The Mergelhorizont (marl bed) III suggested by Merki (1961) as the limit between Oberer Trochitenkalk and Plattenkalk is believed by Pietsch et al. (2016) to be a time marker crossing the heterochronous, petrographically defined boundary between the Kienberg and Liedertswil Members. However, this horizon, often the lowermost in a succession of many thin shale intervals, is an excellent geophysical marker producing a distinct positive gamma-log peak. Recently named the Dünnleberg Bed (Pietsch et al. 2016), the occurrence of this marker is proved throughout Northern Switzerland.

Principales publications: Pietsch Johannes S., Wetzel Andreas, Jordan Peter (2016) : A new lithostratigraphic scheme for the Schinznach Formation (upper part of the Muschelkalk Group of northern Switzerland). Swiss J. Geosc. 109/2, 285-307