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New Rb-Sr whole-rock data are presented which confirm a Grenvillian age for widespread, early, regional metamorphism of the Moine in the SW Highlands of Scotland. It further suggests that Caledonian metamorphic activity occurred between c.470 and 410 Ma ago. Previous isotopic analyses of mineral separates from schists, gneissose pelites and pegmatites are reviewed in the light of the new data, and the work of Purdy & Jaeger (1976). This suggests a cooling history, following the Caledonian metamorphism, which involved sequential uplift of crustal segments.

A 14 point Rb/Sr whole rock isochron obtained from the Morar Pelite in the Morar area of the Northern Highlands suggests an age of 1024± 96 Ma for the main metamorphism of the Morar Moines. Within error this age overlaps that recently given for the Ardgour Gneiss and thus confirms the existence of Grenvillian elements within the Northern Highland Block. It suggests that the tectono-metamorphic history of the southwestern Moines is more complex than hitherto thought.

Malay Basin, a northward-trending pull-apart extensional rift basin, formed during the late Eocene-early Oligocene and then underwent thermal subsidence and sedimentation during the early Miocene. Reorientation of regional stress fields during the mid-Miocene caused structural inversion resulting in east-west anticlines and half grabens.

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