Post-Caledonian brittle deformation in the Bergen area,West Norway: results from K–Ar illite fault gouge dating
Post-Caledonian extension during orogenic collapse and Mesozoic rifting in the West Norway–northern North Sea region was accommodated by the formation and repeated reactivation of ductile shear zones and brittle faults. Offshore, the Late Palaeozoic–Mesozoic rift history is relatively well known; ex...
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ftsubgoettingen:oai:goescholar:1/14300 2023-05-15T17:35:59+02:00 Post-Caledonian brittle deformation in the Bergen area,West Norway: results from K–Ar illite fault gouge dating Ksienzyk, Anna K. Wemmer, Klaus Jacobs, Joachim Fossen, Haakon Schomberg, Anna C. Süssenberger, Annette Lünsdorf, N. Keno Bastesen, Eivind 2016 http://resolver.sub.uni-goettingen.de/purl?gs-1/14300 https://doi.org/10.17850/njg96-3-06 eng eng 0029-196X http://resolver.sub.uni-goettingen.de/purl?gs-1/14300 doi:10.17850/njg96-3-06 openAccess https://creativecommons.org/licenses/by/4.0/ CC-BY fault gouge illite K–Ar dating geochronology rifting journalArticle publishedVersion 2016 ftsubgoettingen https://doi.org/10.17850/njg96-3-06 2022-11-02T09:28:54Z Post-Caledonian extension during orogenic collapse and Mesozoic rifting in the West Norway–northern North Sea region was accommodated by the formation and repeated reactivation of ductile shear zones and brittle faults. Offshore, the Late Palaeozoic–Mesozoic rift history is relatively well known; extension occurred mainly during two rift phases in the Permo–Triassic (Phase 1) and Mid–Late Jurassic (Phase 2). Normal faults in the northern North Sea, e.g., on the Horda Platform, in the East Shetland Basin and in the Viking Graben, were initiated or reactivated during both rift phases. Onshore, on the other hand, information on periods of tectonic activity is sparse as faults in crystalline basement rocks are difficult to date. K– Ar dating of illite that grows synkinematically in fine-grained fault rocks (gouge) can greatly help to determine the time of fault activity, and we apply the method to nine faults from the Bergen area. The K–Ar ages are complemented with X-ray diffraction analyses to determine the mineralogy, illite crystallinity and polytype composition of the samples. Based on these new data, four periods of onshore fault activity could be defined: (1) the earliest growth of fault-related illite in the Late Devonian–Early Carboniferous (>340 Ma) marks the waning stages of orogenic collapse; (2) widespread latest Carboniferous–Mid Permian (305–270 Ma) fault activity is interpreted as the onset of Phase 1 rifting, contemporaneous with rift-related volcanism in the central North Sea and Oslo Rift; (3) a Late Triassic–Early Jurassic (215–180 Ma) period of onshore fault activity postdates Phase 1 rifting and predates Phase 2 rifting and is currently poorly documented in offshore areas; and (4) Early Cretaceous (120–110 Ma) fault reactivation can be linked either to late Phase 2 North Sea rifting or to North Atlantic rifting. peerReviewed Article in Journal/Newspaper North Atlantic Georg-August-Universität Göttingen: GoeScholar Bergen Norway Norwegian Journal of Geology |
institution |
Open Polar |
collection |
Georg-August-Universität Göttingen: GoeScholar |
op_collection_id |
ftsubgoettingen |
language |
English |
topic |
fault gouge illite K–Ar dating geochronology rifting |
spellingShingle |
fault gouge illite K–Ar dating geochronology rifting Ksienzyk, Anna K. Wemmer, Klaus Jacobs, Joachim Fossen, Haakon Schomberg, Anna C. Süssenberger, Annette Lünsdorf, N. Keno Bastesen, Eivind Post-Caledonian brittle deformation in the Bergen area,West Norway: results from K–Ar illite fault gouge dating |
topic_facet |
fault gouge illite K–Ar dating geochronology rifting |
description |
Post-Caledonian extension during orogenic collapse and Mesozoic rifting in the West Norway–northern North Sea region was accommodated by the formation and repeated reactivation of ductile shear zones and brittle faults. Offshore, the Late Palaeozoic–Mesozoic rift history is relatively well known; extension occurred mainly during two rift phases in the Permo–Triassic (Phase 1) and Mid–Late Jurassic (Phase 2). Normal faults in the northern North Sea, e.g., on the Horda Platform, in the East Shetland Basin and in the Viking Graben, were initiated or reactivated during both rift phases. Onshore, on the other hand, information on periods of tectonic activity is sparse as faults in crystalline basement rocks are difficult to date. K– Ar dating of illite that grows synkinematically in fine-grained fault rocks (gouge) can greatly help to determine the time of fault activity, and we apply the method to nine faults from the Bergen area. The K–Ar ages are complemented with X-ray diffraction analyses to determine the mineralogy, illite crystallinity and polytype composition of the samples. Based on these new data, four periods of onshore fault activity could be defined: (1) the earliest growth of fault-related illite in the Late Devonian–Early Carboniferous (>340 Ma) marks the waning stages of orogenic collapse; (2) widespread latest Carboniferous–Mid Permian (305–270 Ma) fault activity is interpreted as the onset of Phase 1 rifting, contemporaneous with rift-related volcanism in the central North Sea and Oslo Rift; (3) a Late Triassic–Early Jurassic (215–180 Ma) period of onshore fault activity postdates Phase 1 rifting and predates Phase 2 rifting and is currently poorly documented in offshore areas; and (4) Early Cretaceous (120–110 Ma) fault reactivation can be linked either to late Phase 2 North Sea rifting or to North Atlantic rifting. peerReviewed |
format |
Article in Journal/Newspaper |
author |
Ksienzyk, Anna K. Wemmer, Klaus Jacobs, Joachim Fossen, Haakon Schomberg, Anna C. Süssenberger, Annette Lünsdorf, N. Keno Bastesen, Eivind |
author_facet |
Ksienzyk, Anna K. Wemmer, Klaus Jacobs, Joachim Fossen, Haakon Schomberg, Anna C. Süssenberger, Annette Lünsdorf, N. Keno Bastesen, Eivind |
author_sort |
Ksienzyk, Anna K. |
title |
Post-Caledonian brittle deformation in the Bergen area,West Norway: results from K–Ar illite fault gouge dating |
title_short |
Post-Caledonian brittle deformation in the Bergen area,West Norway: results from K–Ar illite fault gouge dating |
title_full |
Post-Caledonian brittle deformation in the Bergen area,West Norway: results from K–Ar illite fault gouge dating |
title_fullStr |
Post-Caledonian brittle deformation in the Bergen area,West Norway: results from K–Ar illite fault gouge dating |
title_full_unstemmed |
Post-Caledonian brittle deformation in the Bergen area,West Norway: results from K–Ar illite fault gouge dating |
title_sort |
post-caledonian brittle deformation in the bergen area,west norway: results from k–ar illite fault gouge dating |
publishDate |
2016 |
url |
http://resolver.sub.uni-goettingen.de/purl?gs-1/14300 https://doi.org/10.17850/njg96-3-06 |
geographic |
Bergen Norway |
geographic_facet |
Bergen Norway |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_relation |
0029-196X http://resolver.sub.uni-goettingen.de/purl?gs-1/14300 doi:10.17850/njg96-3-06 |
op_rights |
openAccess https://creativecommons.org/licenses/by/4.0/ |
op_rightsnorm |
CC-BY |
op_doi |
https://doi.org/10.17850/njg96-3-06 |
container_title |
Norwegian Journal of Geology |
_version_ |
1766135323584102400 |