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Outcrop-scale manifestations of reactivation during multiple superimposed rifting and basin inversion events: the Devonian Orcadian Basin, northern Scotland

Dichiarante, A.M.; Holdsworth, R.E.; Dempsey, E.D.; McCaffrey, K.J.W.; Utley, T.A.G.

Outcrop-scale manifestations of reactivation during multiple superimposed rifting and basin inversion events: the Devonian Orcadian Basin, northern Scotland Thumbnail


Authors

A.M. Dichiarante

E.D. Dempsey

T.A.G. Utley



Abstract

The Devonian Orcadian Basin in Scotland hosts extensional fault systems assumed to be related to the initial formation of the basin, with only limited post-Devonian inversion and reactivation. However, a recent detailed structural study across Caithness, underpinned by published Re–Os geochronology, shows that three phases of deformation are present. North–south- and NW–SE-trending Group 1 faults are related to Devonian ENE–WSW transtension associated with sinistral shear along the Great Glen Fault during the formation of the Orcadian Basin. Metre- to kilometre-scale north–south-trending Group 2 folds and thrusts are developed close to earlier sub-basin-bounding faults and reflect late Carboniferous–early Permian east–west inversion associated with dextral reactivation of the Great Glen Fault. The dominant Group 3 structures are dextral oblique NE–SW-trending and sinistral east–west-trending faults with widespread syndeformational carbonate mineralization (± pyrite and bitumen) and are dated using Re–Os geochronology as Permian (c. 267 Ma). Regional Permian NW–SE extension related to the development of the offshore West Orkney Basin was superimposed over pre-existing fault networks, leading to local oblique reactivation of Group 1 faults in complex localized zones of transtensional folding, faulting and inversion. The structural complexity in surface outcrops onshore therefore reflects both the local reactivation of pre-existing faults and the superimposition of obliquely oriented rifting episodes during basin development in the adjacent offshore areas.

Citation

Dichiarante, A., Holdsworth, R., Dempsey, E., McCaffrey, K., & Utley, T. (2020). Outcrop-scale manifestations of reactivation during multiple superimposed rifting and basin inversion events: the Devonian Orcadian Basin, northern Scotland. Journal of the Geological Society, 178(1), https://doi.org/10.1144/jgs2020-089

Journal Article Type Article
Acceptance Date Sep 7, 2020
Online Publication Date Sep 16, 2020
Publication Date 2020
Deposit Date Nov 27, 2020
Publicly Available Date Mar 28, 2024
Journal Journal of the Geological Society
Print ISSN 0016-7649
Electronic ISSN 2041-479X
Publisher The Geological Society
Peer Reviewed Peer Reviewed
Volume 178
Issue 1
DOI https://doi.org/10.1144/jgs2020-089

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