Record of a dense succession of drowning phases in the Alpstein mountains, northeastern Switzerland: Part II—the Lower Cretaceous Schrattenkalk Formation (late Barremian)

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Etat: Public
Version: de l'auteur⸱e
Licence: CC BY 4.0
ID Serval
serval:BIB_A68A5EF6C7A4
Type
Article: article d'un périodique ou d'un magazine.
Collection
Publications
Institution
Titre
Record of a dense succession of drowning phases in the Alpstein mountains, northeastern Switzerland: Part II—the Lower Cretaceous Schrattenkalk Formation (late Barremian)
Périodique
Swiss Journal of Geosciences
Auteur⸱e⸱s
Pictet Antoine, Tschanz Karl, Kürsteiner Peter
ISSN
1661-8726
1661-8734
Statut éditorial
Publié
Date de publication
12/2023
Peer-reviewed
Oui
Volume
116
Numéro
1
Langue
anglais
Résumé
The Schrattenkalk Formation represents a complete succession of Lower Cretaceous shallow-water carbonate platform series cropping out in the Alpstein massif of north-eastern Switzerland. The Schrattenkalk Formation is traditionally divided into two sedimentary units, the “Lower” and the “Upper” Schrattenkalk, separated by the more marly Rawil Member. The “Lower” Schrattenkalk is habitually dated to the late Barremian, while the Rawil Member and the “Upper” Schrattenkalk are dated to the early Aptian. New field observations, however, call the lithostratigraphic dichotomy of the Schrattenkalk into question, as the neritic carbonates are disrupted by several key surfaces associated with karstic episodes and/or transgressive sediments, corresponding to ammonite-rich hemipelagic deposits on the distal shelf. A large number of ammonites were collected in the Drusberg Member as well as rare ammonites from the Schrattenkalk Formation. These ammonites as well as the neritic macrofauna from the Schrattenkalk Formation allow a precise dating of the onset of the Schrattenkalk Formation across the Alpstein massif and its successive phases of progradation. Three successive carbonate bodies and a fourth sedimentary intermediate rock body at the top of the Schrattenkalk platform are defined, based on new biostratigraphic data and updated interpretations of the sequence stratigraphy and geochemical data. The data shows a progressive onset of the Schrattenkalk carbonate platform along the studied transect, following a SE progradation over time. The oldest deposits refer to the upper Barremian T. vandenheckii Zone and the youngest carbonates to the uppermost Barremian M. sarasini Subzone. The new dating of the discontinuity surfaces and key-beds highlight three successive flooding events. The first drowning phase, which correlates with the "Sartousiana" event, dates from the middle late Barremian (upper T. vandenheckii—lower G. sartousiana Zone). The second phase, represented by the Rawil Member, is an incipient drowning, which seems to coincide with the latest Barremian Taxy event (usually reported to the I. giraudi and lowermost M. sarasini zones) according to rare ammonite discoveries. The final demise of the Schrattenkalk platform, situated close to the Barremian-Aptian boundary, is related to an exposure and consecutive drowning event.
Mots-clé
Helvetic domain, Säntis nappe, Biostratigraphy, Sedimentology, Schrattenkalk, Barremian
Open Access
Oui
Financement(s)
Autre
Création de la notice
15/02/2023 9:19
Dernière modification de la notice
06/12/2023 8:28
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