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Post‐tectonic clastic dykes in the Dalradian of Scotland and Ireland: implications for delayed lithification and deformation of sediments
Author(s) -
Phillips C. A.,
Alsop G. I.
Publication year - 2000
Publication title -
geological journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.721
H-Index - 54
eISSN - 1099-1034
pISSN - 0072-1050
DOI - 10.1002/1099-1034(200004/06)35:2<99::aid-gj844>3.0.co;2-x
Subject(s) - dalradian , geology , clastic rock , lithification , tectonics , geochemistry , sedimentary rock , paleontology , geomorphology , petrology , metamorphic rock
Structures associated with soft‐sediment deformation are preserved in the Neoproterozoic Dalradian Supergroup of SW Scotland and NW Ireland. Clastic dykes display a range of age relationships to regional Caledonian D 1 folds and fabrics from pre‐tectonic to hitherto unrecognized post‐tectonic. Evidence for the post‐D 1 timing of some dykes includes the emplacement of centimetre‐scale injections along regional S 1 cleavage, the disorientation and transport of cleaved wall‐rock clasts within larger dykes, and clastic dykes which markedly cross‐cut and transect F 1 fold hinges and axial planes. Collectively, these observations are compatible with the earliest regional (D 1 ) structures deforming a sequence which contained locally overpressured and unlithified pockets of sediment. These critical relationships indicate that overpressured pockets of unlithified sediment were possibly retained within the Dalradian for significant periods of time spanning at least 120 Ma given existing isotopic constraints. Copyright © 2000 John Wiley & Sons, Ltd.