Low-Level Shore Platforms in the South-West Scottish Highlands

A well-developed erosional shoreline in the south-west Highlands of Scotland has often been correlated with an inter-glacial platform in east Ireland, but recently correlation with a late-glacial shoreline in south-east Scotland has been suggested. These two hypotheses are tested by analysing altitude data collected in the south-west Highlands and it is argued that the more recent correlation is the more probable. Points favouring the correlation are discussed and it is suggested that objections to it are not as formidable as often supposed. Isobases for the platform, which is termed the Main Late-glacial Shoreline, are computed by trend surface analysis and suggest an ellipsoid of isostatic uplift with major axis aligned approximately north-south over the western Highlands. Residuals from the regression suggest spatial irregularities of uplift and very effective marine excavation of the slates on the islands of Seil and Luing. In east Kintyre there is clear evidence that the intertidal platforms are old features that have been reoccupied by the sea. AT low levels on the coasts of the south-west Highlands pronounced rock platforms and cliffs are almost continuously developed, and even where these classic features are absent there is usually a very distinct erosional notch in the coastal profile. Originally (e.g. Peach et al., 1909, 1911; Wright, 1914, 1928; Bailey et al., 1924) the platforms were believed to be post-glacial in age for they correspond in altitude with the post-glacial raised shorelines. McCallien (i937), however, believed the post-glacial period was too short to allow the necessary erosion and instead proposed a preor inter-glacial age, a suggestion that has subsequently become generally accepted (McCann, 1966a, 1968; Synge, 1966; Synge and Stephens, 1966; Sissons, 1967; Gray, 1974). Striae and ice moulding have been reported from low-level platforms in the Firth of Lorn area (Fig. i) and there are descriptions of till associated with platforms and cliffs in Arran and Kintyre (Chambers, 1855; Sinclair, 1913) as well as in east Ireland where Stephens (1957) has studied a raised shore platform that has been regarded as the correlative of the platforms in the south-west Highlands (Stephens, 1957; Synge, 1966; Sissons, 1967; Gray, 1974). In the Firth of Lorn area it has been shown (Gray, 1974) that there is one major erosional shoreline present, termed the Main Rock Platform. Regression analysis of 304 altitude measurements on 106 shoreline fragments demonstrated that the shoreline is tilted in a westerly direction from about io-i i m O.D. north of Oban to 4-5 m O.D. in mid-Mull. There was also evidence of a decline in altitude to the south, although the general trends are complicated by a number of bends and one possible fault. If the Main Rock Platform is inter-glacial in age, the fact that it is tilted poses problems; for if it was formed when there was no ice on Scotland it should now have returned to horizontality or possibly be slightly tilted down to the east if isostatic recovery from the weight of ice is not quite complete. It has been suggested (Gray, 1974) that the tilting may be due to tectonic subsidence off the west coast of Scotland. Recently, however, Sissons (1974a and b, 1976a and b) has suggested that the Main Rock Platform correlates not with the east Ireland platform but with a late-glacial erosional shoreline

Altitude (triangle · Geography · Physical geography · Sea level · Shore · Cryospheric studies and observations · Geological formations and processes · Geology · Geology and Paleoclimatology Research · Mathematics · Oceanography

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  Open Access•Stephen Carter, Richard Tipping•Glasgow Archaeological Journal•1991

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  J B Sissons•Transactions of the Institute of…•1982

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  J M Gray, John Gray•Transactions of the Institute of…•1974

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  F M Synge, Nicholas Stephens•Transactions of the Institute of…•1966

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