Skip to Main Content
GEOREF RECORD

The Dalradian rocks of Shetland and their implications for the plate tectonics of the northern Iapetus

Derek Flinn
The Dalradian rocks of Shetland and their implications for the plate tectonics of the northern Iapetus
Scottish Journal of Geology (2007) 43, Part 2: 125-142

Abstract

The Dalradian succession in Shetland is shown to have experienced an extensional tectonic and metamorphic episode prior to the Caledonian orogeny. Sedimentary deposition ended with a major basic and ultrabasic volcanic episode following a long period of extensional basin deposition involving both basic volcanics and turbidites. The ending of deposition was marked by the emplacement of a spinifex-textured komatiite indicating instantaneous rifting of the crust and the underlying Laurentian plate, and the formation of a Laurentian passive continental margin, probably during the opening of Iapetus. The entire contents of the Dalradian depositional basin were rotated bodily 90 degrees to face the rift and to form a 12 km wide vertical belt in the middle of Shetland. A continued rotation in the same sense formed a 25 km wide recumbent inverted limb to form a mega-monocline. The formation of this monocline is considered to have occurred during the extensional phase accompanying rifting because the absence of subsidiary buckle folds of any and every size precludes compressional folding. The metamorphism of the rocks shows a gradual increase from bottom to top of the stratigraphic succession, predating the formation of the monocline, and probably owes its existence to crustal thinning and heating from below the deposition basin during extension. Much of the tectonic and metamorphic history shown by the Dalradian of Shetland may have been overprinted and masked in Scotland by the Caledonian orogeny. In the Dalradian of Shetland the Caledonian orogeny is represented only by the emplacement of the Shetland Ophiolite.


ISSN: 0036-9276
EISSN: 2041-4951
Coden: SJGEAX
Serial Title: Scottish Journal of Geology
Serial Volume: 43, Part 2
Title: The Dalradian rocks of Shetland and their implications for the plate tectonics of the northern Iapetus
Author(s): Flinn, Derek
Affiliation: University of Liverpool, Jane Herdman Laboratories, Liverpool, United Kingdom
Pages: 125-142
Published: 2007
Text Language: English
Publisher: Scottish Academic Press, Edinburgh, United Kingdom
References: 45
Accession Number: 2008-032580
Categories: Igneous and metamorphic petrologyStratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. geol. sketch maps
N59°49'60" - N61°00'00", W01°45'00" - W00°45'00"
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute. Reference includes data from The Geological Society, London, London, United Kingdom
Update Code: 200810
Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal