Sedimentary affiliations and stratigraphic correlation of the Dalradian rocks in the South-west Highlands of Scotland

Abstract

SYNOPSISThe concept of sedimentary affiliations (cf. the sedimentary associations of Knill 1959) is introduced, and three such affiliations (the black slate, the graded quartzite, and the greywacke affiliations) are described from the Dalradian metasediments younger than the Easdale Slates. The stratigraphic distribution of these affiliations is the basis for the proposed stratigraphic correlations.

The Dalradian rocks of Scotland: an introduction

“…Hence, their basin architecture, sedimentological environment and depositional processes have been deduced with some confidence (e.g. Roberts, 1966a;Hickman, 1975;Anderton, 1976Anderton, , 1979Litherland, 1980;Burt, 2002).…”

“…In the South-west Grampian Highlands this facies is represented by three major formations, separated geographically and cropping out on different limbs of major folds but all broadly equivalent stratigraphically (Roberts, 1966a).…”

“…The Crinan Grit Formation, and its local equivalent the Ardmore Formation on the south-east coast of Islay, constitute the whole subgroup on both limbs of the Loch Awe Syncline (Knill, 1959;Roberts, 1966a;Borradaile, 1973Borradaile, , 1979.…”

“…In south Knapdale the lower part of the subgroup is represented by the Upper Erins Quartzite Formation, which lenses out to the northeast. Grey-green, phyllitic pelites and semipelites occur locally and pebbly quartzites, usually graded, become prevalent towards the top of the formation (Roberts, 1966a Around Tyndrum, the Ben Challum Quartzite Formation marks the base of the subgroup locally. It consists of up to 500 m of quartzite and micaceous semipelite with minor amphibolite of possible volcaniclastic origin and two bands of low-grade stratabound pyrite-chalcopyrite-sphalerite mineralization.…”

“…To the south-east of the Ardrishaig Anticline the subgroup is represented by the Loch Tay Limestone which maintains a thickness of around 100 m along strike from Campbeltown to Glen Doll (Bailey, 1925;Elles, 1926;Johnstone and Smith, 1965;McCallien, 1929;Roberts, 1966a;Crane et al, 2002). Thinner developments are also present to the south-east of the main outcrop, at the base of structural outliers of Ben Lui Schist in the inverted limb of the Tay Nappe around Lochearnhead (Johnstone and Smith, 1965;Mendum and Fettes, 1985;Watkins, 1984).…”