Abstract The Moine Thrust zone of NW Scotland marks the Caledonian orogenic front and in the Assynt region consists of several west-vergent major thrust sheets (Moine, Ben More, Glencoul and Sole Thrust sheets) that place allochthonous rocks onto the Lewisian basement and Torridon Group cover in the west. Here we present two new balanced and restored sections across the Moine Thrust zone in the region of the Loch Ailsh and Loch Borralan alkali intrusions. Syenites and alkaline pyroxenites intrude up to Durness Group carbonates. Syenites are interpreted as cut by the Moine and Ben More Thrusts and therefore their intrusion age ( c . 430 Ma) provides a maximum age constraint on cessation of motion along the Moine Thrust. We review and discuss several controversies, notably: (1) relationships between folding in the Ben More Thrust sheet (Sgonnan Mor folds) and fabric development associated with intrusion of the Loch Ailsh pluton and initiation of the Moine and Ben More Thrusts; (2) structural relationships around the Borralan intrusion, particularly the nature of its basal and lateral margins (intrusive or thrust-ramp); (3) the structural relationships of the Cam Loch and Benn Fhuarain klippen; and (4) the timing of motion of all thrust sheets in the southern Assynt culmination.

Abstract Lateglacial–Holocene fjord sediments in Little Loch Broom preserve evidence of extensive slope instability. The major area of reworking is in the outer loch and mid-loch sill region where ice-contact/ice-proximal deposits of the Lateglacial Assynt Glaciogenic Formation have been disrupted by sliding and mass-flow processes linked to the Little Loch Broom Slide Complex and the adjacent Badcaul Slide. Mass failure was instigated about 14–13 ka BP, and is probably the response of the landscape to deglaciation immediately following the removal of ice support during glacial retreat. An initial phase of translational sliding was followed by rotational sliding, as revealed by the superimposition of scallop-shaped slumps on a larger-scale rectilinear pattern of failure. Paraglacial landscape readjustment may also have been enhanced by episodic seismic activity linked to glacio-isostatic unloading. In the inner fjord, evidence of Holocene mass failure includes the Ardessie debris lobe and a discrete intact slide block preserved within the postglacial basinal deposits. The former is a localized accumulation linked to a fluvial catchment on the adjacent An Teallach massif. These mass-transport deposits may represent an ongoing response to paraglacial processes, albeit much reduced (relative to the major slides) in terms of sediment supply to the fjord.

Abstract The fragmentary nature of the outcrop of least modified Scourian rocks limits any attempt at interpretation of their tectonic history. However, the three main areas where such rocks can be studied (Loch Braigh Horrisdale, Creag Mhor Thollaidh and Ard Ialltaig) all show certain common features. The rocks are all orthogneisses, dominantly granodioritic in the SW (Braigh Horrisdale), but quartz-dioritic to dioritic with abundant mafic inclusions at Creag Mhor Thollaidh and Ard Ialltaig. Structurally, there is considerable uniformity; the early gneissose banding/foliation is generally steeply dipping with a NEerly to northerly trend. This structure (S2) has been produced by the D2 deformation of the igneous protoliths of the gneisses, which also locally contain a previous foliation, Sj. A similar structural pattern is found to the south of the Gairloch area, at Ruadh Mheallan in the Torridon district, and also to the north, at Gruinard Bay. Thus, all the areas throughout the Southern Region of the Lewisian complex where the Scourian structure can be recognized in a relatively unmodified state, involving an outcrop width of around 35 km, appear to present a common structural style. This has obvious implications for any collisional model for the Palaeoproterozoic, suggesting that the Archaean blocks on either side of the Loch Maree Group outcrop may have had a common origin, or may originally have been contiguous (see Section 7.3 ). The intense deformation, gently-dipping foliation and high pressure granulite-facies metamorphism that characterize the Scourian of the type area in Scourie and Assynt are not matched