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Late Carboniferous dextral transpressional reactivation of the crustal-scale Walls Boundary Fault, Shetland: the role of pre-existing structures and lithological heterogeneities

Armitage, Timothy B.; Watts, Lee M.; Holdsworth, Robert E.; Strachan, Robin A.

Late Carboniferous dextral transpressional reactivation of the crustal-scale Walls Boundary Fault, Shetland: the role of pre-existing structures and lithological heterogeneities Thumbnail


Authors

Lee M. Watts

Robin A. Strachan



Abstract

The Walls Boundary Fault (WBF) in Shetland, Scotland, formed during the Ordovician-Devonian Caledonian orogeny and underwent dextral reactivation in the Late Carboniferous. In a well-exposed section at Ollaberry, westerly verging, gently plunging regional folds in the Neoproterozoic Queyfirth Group on the western side of the WBF are overprinted by faults and steeply-plunging Z-shaped brittle-ductile folds that indicate contemporaneous right-lateral and top-to-the W reverse displacement. East of the WBF, the Early Silurian Graven granodiorite complex exhibits fault-parallel fractures with Riedel, P and conjugate shears indicating N-S striking dextral deformation and an additional contemporaneous component of E-W shortening. In the Queyfirth Group, the structures are arranged in geometrically and kinematically distinct fault-bounded domains that are interpreted to result from two superimposed tectonic events, the youngest of which displays evidence for bulk dextral transpressional strain partitioning into end-member wrench and contractional strain domains. During dextral transpressional deformation, strain was focussed into pelite horizons and favourably aligned pre-existing structures, leaving relics of older deformation in more competent lithologies. This study highlights the importance of pre-existing structures and lithological heterogeneity during reactivation and suggests the development of a regional transpressional tectonic environment during the Late Carboniferous on the Shetland Platform.

Citation

Armitage, T. B., Watts, L. M., Holdsworth, R. E., & Strachan, R. A. (2020). Late Carboniferous dextral transpressional reactivation of the crustal-scale Walls Boundary Fault, Shetland: the role of pre-existing structures and lithological heterogeneities. Journal of the Geological Society, jgs2020-078. https://doi.org/10.1144/jgs2020-078

Journal Article Type Article
Acceptance Date Sep 22, 2020
Online Publication Date Oct 23, 2020
Publication Date 2020
Deposit Date Sep 28, 2020
Publicly Available Date Mar 29, 2024
Journal Journal of the Geological Society
Print ISSN 0016-7649
Electronic ISSN 2041-479X
Publisher The Geological Society
Peer Reviewed Peer Reviewed
Article Number jgs2020-078
Pages jgs2020-078
DOI https://doi.org/10.1144/jgs2020-078

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