Timing of deposition, orogenesis and glaciation within the Dalradian rocks of Scotland: constraints from U-Pb zircon ages

Dempster, T.J. , Rogerson, G., Tanner, P.W.G., Bluck, B.J., Muir, R.J., Redwood, S.D., Ireland, T.R. and Paterson, B.A. (2002) Timing of deposition, orogenesis and glaciation within the Dalradian rocks of Scotland: constraints from U-Pb zircon ages. Journal of the Geological Society, 159(1), pp. 83-94.

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Abstract

The stratigraphical and structural continuity of the Late Proterozoic Dalradian rocks of the Scottish Highlands is re-examined in the light of new U-Pb zircon ages on the tuffs belonging to the Tayvallich Volcanic Formation (601 ñ 4 Ma), and on the late Grampian 'Newer Gabbros' (470 ñ 9 Ma) of Insch and Morven-Cabrach in Aberdeenshire. These age data, together with the existing 590 ñ 2 Ma age for the Ben Vuirich Granite, provide key radiometric constraints on the evolution of the Dalradian block, and the implications arising from these ages are critically assessed. Three main conclusions are drawn. (1) The entire Caledonian orogeny, although short-lived, is unlikely to have affected sediments of Arenig age and a break probably occurs between those Dalradian sediments of late Proterozoic (<600 Ma) age and the Ordovician rocks of the Highland Border Complex. (2) A period of crustal thickening probably affected some Dalradian rocks prior to 590 Ma. Such an event is indicated by both the polymetamorphic histories of the lower parts of the Dalradian pile and the contact metamorphic assemblages within the aureole of the Ben Vuirich Granite, which are incompatible with sedimentary thicknesses. (3) Age constraints on global Late Proterozoic glacial activity also suggest that the Dalradian stratigraphy is broken into discrete smaller units. Models involving continuous deposition of Dalradian sediments from pre-750 Ma to 470 Ma are rejected.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Bluck, Professor Brian and Dempster, Dr Tim and Tanner, Dr Geoff and Rogerson, Prof Graham
Authors: Dempster, T.J., Rogerson, G., Tanner, P.W.G., Bluck, B.J., Muir, R.J., Redwood, S.D., Ireland, T.R., and Paterson, B.A.
Subjects:Q Science > QE Geology
College/School:College of Science and Engineering > School of Geographical and Earth Sciences
Journal Name:Journal of the Geological Society
Publisher:Geological Society of London
ISSN:0016-7649
Copyright Holders:Copyright © 2002 The Geological Society of London
First Published:First published in Journal of the Geological Society 159 (1) : 83 - 94
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher.

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
159231TEMPORAL AND SPATIAL CONTROLS ON THE EVOLUTION OF CRUSTAL GEOTHERMSTim DempsterNatural Environment Research Council (NERC)GR3/9689GES - GES ADMINISTRATION