The Dalradian rocks of the central Grampian Highlands of Scotland

Treagus, Jack E.; Tanner, P.W. Geoff; Thomas, Peter R.; Scott, Robert A.; Stephenson, David. 2013 The Dalradian rocks of the central Grampian Highlands of Scotland. Proceedings of the Geologists' Association, 124 (1-2). 148-214.

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The central Grampian Highlands, as defined here, are bounded to the north-west by the Great Glen Fault, to the south-west by Loch Etive and the Pass of Brander Fault and to the south-east by the main outcrop of the Loch Tay Limestone Formation. The more arbitrary northern boundary runs north-west along the A9 road and westwards to Fort William. The detailed stratigraphy of the Dalradian Supergroup ranges from the uppermost Grampian Group through to the top of the Argyll Group, most notably seen in the two classic areas of Loch Leven–Appin and Schiehallion–Loch Tay; Southern Highland Group strata are preserved only in a small structural inlier south of Glen Lyon. Major F1 and F2 folds are complicated by co-axial northeast-trending F3 and F4 folding, as well as by locally important north- or NW-trending folds. In the Loch Leven area, nappe-like F1 folds verge to the north-west, whereas to the south-east the major recumbent F1/F2 Tay Nappe verges to the south-east. The trace of the upright Loch Awe Syncline lies between the opposing nappes, but in this region a large mass of late-Caledonian granitic rocks obscures their mutual relationship. Three tectonic ‘slides’ are identified that are certainly zones of high strain but which in part could be obscuring stratigraphical variations. The regional metamorphism ranges from greenschist facies on the western seaboard of Argyll to amphibolite facies in most of the remainder of the region. The study of garnets, together with kyanite and staurolite in the Schiehallion area, has enabled a detailed history of the metamorphism and structure to be unravelled. Stratabound mineralization occurs in the Easdale Subgroup, where there is also evidence of changes of sedimentary environment associated with volcanicity and lithospheric stretching. The region is dissected by a series of NE-trending, dominantly left-lateral, faults, subparallel to the Great Glen Fault, whose movement history is illustrated here by that of the Tyndrum Fault.

Item Type: Publication - Article
Digital Object Identifier (DOI):
ISSN: 00167878
Date made live: 15 May 2013 16:00 +0 (UTC)

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