The North Penninic Bündnerschiefer and Flysch of the Prättigau (Swiss Alps) revisited
Abstract During the re-mapping of the area for the Geological Atlas of Switzerland, a significant stratigraphic unconformity was discovered in the North Penninic (Valais) Bündnerschiefer and the Flysch series of the northern Prättigau. It separates different units of the Cretaceous Bündnerschiefer f...
| Main Author: | |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
SpringerOpen
2024-03-01
|
| Series: | Swiss Journal of Geosciences |
| Subjects: | |
| Online Access: | https://doi.org/10.1186/s00015-024-00454-7 |
| _version_ | 1797233422564851712 |
|---|---|
| author | Wilfried Winkler |
| author_facet | Wilfried Winkler |
| author_sort | Wilfried Winkler |
| collection | DOAJ |
| description | Abstract During the re-mapping of the area for the Geological Atlas of Switzerland, a significant stratigraphic unconformity was discovered in the North Penninic (Valais) Bündnerschiefer and the Flysch series of the northern Prättigau. It separates different units of the Cretaceous Bündnerschiefer from the Palaeogene Flysch. We explain this observation by a basin conversion from extension to compression, which caused the initial deformation of the Bündnerschiefer in an accretionary wedge. Interlinked return-flow has created a new heterogeneous substrate for the flysch sediments and explains the different types of unconformities. The basin conversion coincided with high-grade metamorphism in the vicinity of the the South Penninic suture and the Austroalpine units, and the increased exhumation in the Austroalpine nappe stack. Detrital zircon dating confirms also a change from European to Austroalpine detrital sources in the flysch sandstones. We discuss a palaeotectonic model leading to hP/lT metamorphism of the Bündnerschiefer in the Late Eocene (c. 42 Ma). It appears that the flysch formations were also involved, but to a lesser degree by tectonic deformation from the late Early Eocene onwards, as the pervasive folding characteristic of the Bündnerschiefer is absent. This has been followed by a phase of S-directed backfolding. During the Oligocene and Miocene, more extensive deformation occurred by SE to NW compression and finally by probable westward thrusting and folding. Our main theme is the transition from passive to active continental margins, which in Alpine plate tectonic framework corresponds to the transition to flysch sedimentation by basin conversion. Our results show that the simultaneity of the transition from extension to compression, as indicated by the accumulation of flysch, shifted in time from south to north in the Alpine Tethys. |
| first_indexed | 2024-04-24T16:15:55Z |
| format | Article |
| id | doaj.art-d66ed36ce29046869c0f8dcfe6856539 |
| institution | Directory Open Access Journal |
| issn | 1661-8726 1661-8734 |
| language | English |
| last_indexed | 2024-04-24T16:15:55Z |
| publishDate | 2024-03-01 |
| publisher | SpringerOpen |
| record_format | Article |
| series | Swiss Journal of Geosciences |
| spelling | doaj.art-d66ed36ce29046869c0f8dcfe68565392024-03-31T11:27:34ZengSpringerOpenSwiss Journal of Geosciences1661-87261661-87342024-03-01117113010.1186/s00015-024-00454-7The North Penninic Bündnerschiefer and Flysch of the Prättigau (Swiss Alps) revisitedWilfried Winkler0Geological Institute, Department of Earth Sciences, ETH ZurichAbstract During the re-mapping of the area for the Geological Atlas of Switzerland, a significant stratigraphic unconformity was discovered in the North Penninic (Valais) Bündnerschiefer and the Flysch series of the northern Prättigau. It separates different units of the Cretaceous Bündnerschiefer from the Palaeogene Flysch. We explain this observation by a basin conversion from extension to compression, which caused the initial deformation of the Bündnerschiefer in an accretionary wedge. Interlinked return-flow has created a new heterogeneous substrate for the flysch sediments and explains the different types of unconformities. The basin conversion coincided with high-grade metamorphism in the vicinity of the the South Penninic suture and the Austroalpine units, and the increased exhumation in the Austroalpine nappe stack. Detrital zircon dating confirms also a change from European to Austroalpine detrital sources in the flysch sandstones. We discuss a palaeotectonic model leading to hP/lT metamorphism of the Bündnerschiefer in the Late Eocene (c. 42 Ma). It appears that the flysch formations were also involved, but to a lesser degree by tectonic deformation from the late Early Eocene onwards, as the pervasive folding characteristic of the Bündnerschiefer is absent. This has been followed by a phase of S-directed backfolding. During the Oligocene and Miocene, more extensive deformation occurred by SE to NW compression and finally by probable westward thrusting and folding. Our main theme is the transition from passive to active continental margins, which in Alpine plate tectonic framework corresponds to the transition to flysch sedimentation by basin conversion. Our results show that the simultaneity of the transition from extension to compression, as indicated by the accumulation of flysch, shifted in time from south to north in the Alpine Tethys.https://doi.org/10.1186/s00015-024-00454-7Prättigau half-windowCretaceous-PalaeogeneStratigraphyPalaeogeographyBasin conversionTectonics |
| spellingShingle | Wilfried Winkler The North Penninic Bündnerschiefer and Flysch of the Prättigau (Swiss Alps) revisited Swiss Journal of Geosciences Prättigau half-window Cretaceous-Palaeogene Stratigraphy Palaeogeography Basin conversion Tectonics |
| title | The North Penninic Bündnerschiefer and Flysch of the Prättigau (Swiss Alps) revisited |
| title_full | The North Penninic Bündnerschiefer and Flysch of the Prättigau (Swiss Alps) revisited |
| title_fullStr | The North Penninic Bündnerschiefer and Flysch of the Prättigau (Swiss Alps) revisited |
| title_full_unstemmed | The North Penninic Bündnerschiefer and Flysch of the Prättigau (Swiss Alps) revisited |
| title_short | The North Penninic Bündnerschiefer and Flysch of the Prättigau (Swiss Alps) revisited |
| title_sort | north penninic bundnerschiefer and flysch of the prattigau swiss alps revisited |
| topic | Prättigau half-window Cretaceous-Palaeogene Stratigraphy Palaeogeography Basin conversion Tectonics |
| url | https://doi.org/10.1186/s00015-024-00454-7 |
| work_keys_str_mv | AT wilfriedwinkler thenorthpenninicbundnerschieferandflyschoftheprattigauswissalpsrevisited AT wilfriedwinkler northpenninicbundnerschieferandflyschoftheprattigauswissalpsrevisited |