Abstract The Moine Thrust Zone and overlying Moine Nappe represent classic ground in Scottish geology in which Neoproterozoic Moine metasedimentary rocks were translated towards the WNW over the Laurentian foreland comprising Lewisian basement gneisses and a Cambrian cover succession during Caledonian orogenesis at c. 430 Ma. Systematic mapping of both the Moine Nappe and underlying Moine Thrust Zone in the Loch Hope to Whiten Head region of Sutherland extends the tectonic stratigraphy developed in other parts of the thrust zone to the little-studied north coast section. An apparent continuum of deformation is recognized from the Moine Nappe down into the underlying thrust zone with a consistent gently ESE-dipping foliation associated with down-dip mineral and extension lineations. The polyphase fold history present within the Moine Nappe and the thrust zone results from progressive deformation during thrusting. Thrust-related fold axes and bedding-cleavage intersections are typically subparallel to the transport direction in high-strain zones, whereas gently north- or south-plunging attitudes are common in lower strain portions of the thrust zone. Thrusts are commonly deformed by folds developed within their footwalls, consistent with a foreland-propagating sequence of deformation. The newly defined Lochan Riabhach Thrust is interpreted as an ‘out-of-sequence’ structure that sliced at low angles across the thrust zone and toward the WNW after initial thrust stacking. Comparison with the downfaulted segment of the Moine Nappe and thrust zone exposed on the foreland at Faraid Head demonstrates cross-strike continuity of the thrust sheet template and structural history for at least 15 km to the NW.

Abstract The Moine Thrust zone (MTZ) marks the Caledonian foreland-to-hinterland transition zone at the base of the Scandian ( c . 430 Ma) orogenic wedge. In the Loch Eriboll region, the upper ductile part of the MTZ is composed in ascending order of two regionally extensive thrust sheets (Upper Arnaboll-Creag na Faoilin and Creagan) and is overlain by the Moine Nappe. Quartz crystal fabrics, kinematic vorticity (W m ), and strain estimates from the ductile thrust sheets in this region are used to determine how pure and simple shear components of deformation are partitioned, and indicate that these processes may be thermally, structurally, and lithologically dependent. At the lowest structural levels, quartzite and gneiss in the Upper Arnaboll-Creag na Faoilin (UA-CNF) thrust sheet yield rigid grain-based arithmetic mean minimum (W m min) and mean maximum (W m max) vorticity estimates of 0.57 and 0.67, respectively (60–53% pure shear). Creagan thrust sheet mylonites yield W m min and W m max estimates of 0.59 and 0.72 (59–48% pure shear). At the highest structural levels, Moine Nappe mylonites yield W m min and W m max estimates of 0.59 and 0.71 (59–49% pure shear). Quartz c - and a -axis fabrics qualitatively indicate an increase in non-coaxial deformation (top-to-the-west) traced towards structurally higher levels, which is accompanied by increases in deformation temperature ( c . 370 °C to c . 550 °C). Integrated strain and vorticity estimates indicate that significant sub-vertical foliation normal shortening has occurred as nappe stacking progressed.

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.

Abstract In this paper we review microstructural and petrofabric work carried out on the Moine Thrust zone and overlying thrust nappes. Our review is primarily historical, and starts with contributions made by both ‘amateur’ and ‘professional’ geologists from the 1880s through to the early 1920s during, and immediately following, the original field-mapping of the Moine Thrust zone by the Geological Survey. From the 1920s to the early 1950s contributions were first dominated by Geological Survey work on the microstructural and metamorphic transition between the thrust zone mylonites and the overlying Moine metasedimentary rocks. Subsequent university-based quartz petrofabric work, primarily focused on the Moines, would ultimately lead to the ‘Moine Petrofabric Controversy’ that ran from the late 1940s to the early 1960s. The later stages of this controversy overlapped, from the early 1950s–mid 1960s, with a phase of microstructural and quartz petrofabric work that concentrated on the thrust zone mylonites and immediately overlying Moine Schists. Our review concludes with an overview of microstructural, petrofabric and related strain analyses undertaken since the early 1970s, both within the Moine Thrust zone and its immediate foreland and in the overlying higher grade thrust sheets. Throughout our review we emphasize and track the changing tectonic interpretations that have been placed on available microstructural and petrofabric data.