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

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doi: 10.1144/0016-764901061
Authors:Dempster, T. J.; Rogers, G.; Tanner, P. W. G.; Bluck, B. J.; Muir, R. J.; Redwood, S. D.; Ireland, T. R.; Paterson, B. A.
Author Affiliations:Primary:
University of Glasgow, Division of Earth Sciences, Glasgow, United Kingdom
Scottish Universities Environmental Research Centre, United Kingdom
British Geological Survey, United Kingdom
Stanford University, United States
Volume Title:Journal of the Geological Society of London
Source:Journal of the Geological Society of London, Vol.159(Part 1), p.83-94. Publisher: Geological Society of London, London, United Kingdom. ISSN: 0016-7649
Publication Date:2002
Note:In English. 127 refs.; illus., incl. strat. col., 2 tables, geol. sketch map
Summary: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 ± 4 Ma), and on the late Grampian "Newer Gabbros" (470 ± 9 Ma) of Insch and Morven-Cabrach in Aberdeenshire. These age data, together with the existing 590 ± 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.
Subjects:Absolute age; Clastic rocks; Dalradian; Dates; Deposition; Depositional environment; Gabbros; Glaciation; Igneous rocks; Lithostratigraphy; Neoproterozoic; Nesosilicates; Orogeny; Orthosilicates; Plutonic rocks; Precambrian; Proterozoic; Sedimentary rocks; Silicates; Tillite; U/Pb; Upper Precambrian; Zircon; Zircon group; Europe; Great Britain; Scotland; Scottish Highlands; United Kingdom; Western Europe; Newer Gabbros; Tayvallich Volcanics
Coordinates:N560000 N560000 W0054500 W0054500
N570000 N570000 W0030000 W0030000
Abstract Numbers:02M/2026
Record ID:2002021136
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from The Geological Society, London, London, United Kingdom
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