Book Reviews

At the outset, I should declare an interest in this work. In 1993, I teamed up with Graham Leslie to study the Ben Vuirich Granite after we had met at a Tectonic Studies Group meeting and found that we were working on the same ground. Graham had come striding up from Glen Shee to examine Ben Vuirich, which is outwith Sheet 56W but so crucial to understanding the timing of events in the Dalradian that he could not resist mapping a part of it. I was an intruder, outside my usual territory, but also looking to establish a sound structural framework for the U-Pb (zircon) age on the granite of 590 ± 2 Ma published a few years previously. We have since worked together on other projects, so my review cannot be considered as entirely impartial. This Memoir is an excellent example of what can be achieved through whole-hearted collaboration between BGS and an experienced team of university staff, funded by an NERC academic mapping contract. The result is a comprehensive analysis of the geology of a structurally complex area of Dalradian and other rocks, for which there is no previously published account. The volume is dedicated to the memory of Steve Robertson, a BGS member of the team, who was tragically killed in a road accident in 2000. This work is primarily concerned with the stratigraphy, structure, and metamorphism of the Dalradian rocks in an area that straddles the boundary between the Highlands and the Lowlands. The emphasis is on bedrock geology, but the applied and geophysical aspects are given due prominence. Presentation of the results is enhanced by in-text maps, cross-sections and diagrams, in which a single colour is used very effectively. Even the limitations imposed by the map format have been overcome by providing thematic maps that have been extended in the NW corner to capture part of the Ben Vuirich pluton. The Dalradian rocks generally dip to the north and are inverted on the lower limb of the 'Tay Nappe'. They range in age from the Ballachulish Subgroup (Appin Group) in the north, to the upper part of the Southern Highland Group at the Highland Boundary Fault Zone, in the south. Rocks of Silurian to Lower Devonian age are found SE of the fault zone. The structural setting is typical of the Highland Border: four phases of ductile deformation are recognized (D1-D4), with structural complexity increasing from south to north. Dl is dominant in a narrow zone adjacent to the Highland Boundary Fault, but is progressively overprinted by D2 and D3 northwards. A point to note is that the interpretation of some S1/S2 interference patterns as C-S fabrics (p. 56) is incorrect: to be classified thus, the S and C elements had to have formed simultaneously. The prograde regional metamorphism is interpreted as a single, progressive event that peaked in preto syn-D2 times: it increased in grade northwards from the chlorite zone adjacent to the Highland Boundary Fault, to the kyanite zone (with two episodes of migmatization) in the area east of Ben Vuirich. Previous work indicating that there was an early low-P event in the Tummel Steep Belt (i.e. Dempster & Harte 1986) is not referenced, although it is implicitly rejected. Two generations of sill-like metamafic bodies, emplaced pre-D2 and post-D2 respectively, are particularly common in the upper part of the Argyll Group and the lower part of the Southern Highland Group. There are two kilometrescale, post-orogenic, undated intrusions of granodiorite, and a variety of dykes and. minor intrusions ranging in composition from aplite to lamprophyre. The landscape was sculpted into its present form during the late Devensian glaciation.