Short Paper: The extent of Grampian orogenic activity in the Scottish Highlands

Publisher Website
Google Scholar
Abstract
Structures in Atholl nappe Grampian Division rocks in the Tayside Region can be traced NW into the supposedly older Central Highland Division in Speyside and Strath Nairn where they are the earliest fabrics present. Grampian Division/Central Highland Division contrasts appear to involve a gradational metamorphic change, and the existence of the Grampian slide supposed, by previous workers to separate the two units has not been confirmed. Atholl nappe fabrics have been shown to be coeval with those of Grampian orogenesis in the Tay nappe where their age is constrained by the 590 ± 2 Ma Ben Vuirich granite. Grampian orogenic structures can thus be traced, as the earliest structures present, as far as the Great Glen fault, a conclusion which may have a bearing on the significance of the fault as a terrane boundary. Central Highlands. The metamorphic rocks of the Scottish Central Highlands (Fig. 1) comprise units referred to the Southern Highland (youngest), Argyll, Appin and Grampian (oldest) groups. While Harris et al. 1978 regarded the Grampian Group as the oldest Dalradian group, it is broadly equivalent to the Grampian Division (Moine) (GD) of Piasecki (1980) who also identified the Central Highland Division (Moine) (CHD) which occupies several hundred square kilometres of Inverness-shire east and south of Inverness and which forms three other small inliers in Speyside, not distinguished on Fig. 1. Working largely in Speyside and adjacent areas, Piasecki & van Breemen (1983) regarded the CHD as lithostratigraphically broadly equivalent to Moine rocks of the N Highlands and