The role of thrust tectonic models in understanding structural evolution in NW Scotland

Abstract

The NW Highlands of Scotland have been an important test-bed for concepts in thrust tectonics. Here, research following the breakthrough publication of the 1907 memoir is reviewed, especially that relating to structural evolution in the Moine Thrust Belt. This belt was WNW-directed, involving cover sediments and thin sheets of crystalline basement. Displacements total 50–100 km within a branching array of thrusts. There are significant lateral variations in imbricate thrust geometry and localization behaviour. Following the application of linked thrust tectonic models in the 1980s significant attention has been directed at deducing thrust sequences, patterns of strain localization, folding styles and the significance of extensional tectonics as part of the structural evolution. The key has lain in deducing the kinematic linkages between thrusts and other structures, tracing displacements and examining the consequences of structural interpretations through geometric restoration. Thrusting models have been up-scaled to the crust. However, these linked kinematic approaches have been applied only hesitantly to the ductile structures of the Moine Thrust Sheet where structural research has focused on outcrop-scale deformation, especially of folds. Consequently, the larger-scale significance for Caledonian tectonics of thrust systems in the NW Highlands of Scotland has yet to be developed fully.

Mechanisms of margin inversion in the external Western Alps: Implications for crustal rheology

“…Similar geometries have been mapped out in the Caledonide Moine Thrust Belt (Barber, 1965cited in Butler et al, 2006band Butler, 2010. It is noteworthy that these shear zones are located in the footwall of the Moine Thrust and thus experienced significant tectonic burial (lower greenschist facies).…”

“…It is noteworthy that these shear zones are located in the footwall of the Moine Thrust and thus experienced significant tectonic burial (lower greenschist facies). In the southern part of this belt, where those thick shear zones are observed, large-scale folding of the basement-cover interface is witnessed by recumbent structures (Stewart, 2002;Butler, 2010). Moreover, it is suggested that those distributed basement shear zones have evolved as major basement thrusts (Butler et al, 2006b).…”

Mylonites: lessons from Eriboll

“…But unlike Nicol, Callaway and Lapworth who quickly came to the conclusion that the NW Highlands were the ancient equivalent to a modern Alpine mountain belt, Peach and Horne did not do so, in publications, until 1930 (Peach & Horne 1930). Butler (2010) demonstrates the important role that good geological knowledge and solid theory played in their fieldwork and its interpretation. Murchison and Geikie, on the other hand, appear to have used a preconceived hypothesis to guide their field studies and its subsequent interpretation.…”

Caledonian and Knoydartian overprinting of a Grenvillian inlier and the enclosing Morar Group rocks: structural evolution of the Precambrian Proto-Moine Nappe, Glenelg, NW Scotland

“…The undeformed Foreland of the Caledonides to the NW comprises Archaean-Palaeoproterozoic Lewisian gneiss, overlain by early Neoproterozoic Torridon Group sandstone, in turn unconformably overlain by a Cambro-Ordovician shelf sequence. The Moine Thrust Zone is a fold-andthrust belt that imbricates this distinctive succession, and is capped by the brittle-ductile Moine thrust (e.g., Peach et al 1907;Elliott & Johnson 1980;Coward 1983;Butler 2010;Thigpen et al 2010).…”