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Letter to the Editors DISTRIBUTION AND DEVELOPMENT OF THE MAIN ROCK PLATFORM, WESTERN ! COMMENT

SIRS—Dawson (1988), in his study of the Main Rock Platform in and has discussed more general aspects of the distribution and develop­ ment of the shoreline throughout western Scotland. I wish to add to this discussion since it seems to me that the distribution and development of the Main Rock Platform are rather more complex than Dawson suggests.

1. Dawson (p. 167) suggests that the excellent development of the platform fragments in areas of limited fetch in (Fig. 1), in areas where glacial erosion was formerly intense, indicates that the fragments are unlikely to have been overridden by ice. Later (p. 170), he uses the presence of these fragments and others in Loch Moidart to suggest that neither loch was occupied by glacier ice during the Loch Lomond Stadial. However, elsewhere in western Scotland well developed fragments of the Main Rock Platform occur in similar locations inside the generally agreed limits of the Loch Lomond Stadial. The locations include Corran, in Loch Linnhe (Peacock 1975) and Loch Spelve on Mull (Gray 1978). Thus care must be taken in implying the absence of Loch Lomond Stadial glaciers from the presence of well-developed Main Rock Platform fragments. 2. Dawson (pp. 161-63) also discusses the problem of the pronounced contrast in the clarity of the shoreline between the SW and NW Highlands, first pointed out by Bailey et al. (1924), who drew a line to mark the boundary between the two areas (Fig. 1). Dawson states (p. 171) that "The observed distribution of stretches of the Main Rock Platform bears no apparent relationship to rock lithology. . . there are relativity few platforms in the schist bedrock areas of Moidart yet where platforms do occur. . . they are often spectacular features. By contrast, the schists of the SW Highlands (e.g. , and northern Arran) are often associated with exceptionally well-developed areas of Main Rock Platform". Two points can be made about these statements. First, in the western Highlands, the and Moinian metamorphic successions are more complex than "schist" and schist itself is not a uniform rock type in mineralogy, texture or metamorphic structure. Thus any differences in development of the shoreline that do occur in two areas of metamorphic rocks could be the result of differences in the resistances of the rocks. Secondly, however, the contrast in development of the shoreline in these two metamorphic areas is not as marked as Dawson suggests. There are long stretches of the coastlines of mid-, Knapdale and Kintyre where the Main Rock Platform is absent or poorly developed. For example, on the mainland coast Scott. J. Geol. 25, (2), 227-231, 1989 Downloaded from http://sjg.lyellcollection.org/ by guest on October 6, 2021

228 LETTERS TO THE EDITORS

between Loch Melfort and West Loch (Fig. 1) the Main Rock Platform is only patchily developed. In a survey of this coastline (Gray 1978), the only fragments considered sufficiently well-developed to level occurred at Croaibh Haven, Castle, Keillmore and around Kilberry. Only along the eastern coast of Kintyre south of does the shoreline begin to approach continuity along the coast. Thus the pattern of distribution and development of the Main Rock Platform in the Dalradian rocks of the SW Highlands south of Loch Melfort has much in common with that in Ardnamurchan and Moidart where "although it is often exceptionally well-developed in the areas in which it occurs, it is absent from extensive stretches of coastline" (Dawson 1988, p. 171). Although complicated by several factors, the real contrast in the development and distribution of the Main Rock Platform is between the Oban/ area (Gray 1974) and more peripheral locations. As" Bailey et al. (1924, p. 409) pointed out "It is only after experience has shown that the deterioration is definitely regional that one is driven to propound a regional explanation". 3. Dawson (p. 172) also discussed Peacock et al. 's (1978) suggestion that the Main Rock Platform may have resulted from the retrimming of an earlier platform. (Note that the wrong paper was referenced as Peacock et al., 1978, in Dawson's paper). He speculated that the contrast described above results from the absence of this earlier formed platform to the north of Bailey et al.'s line due the presence of an ice mass "whose southern margin was located close to the line. . . ". Such a glacial limit, if real, would have had a rather tortuous southern ice margin (Fig. 1). In fact the explanation for the shape of Bailey et al. 's line is much simpler. First, the contortions of the line over are readily explained by contrasts in rock resistance. The shoreline was not eroded in the massively jointed microgranite that outcrops to the south-east of Loch AUne on the southern tip of Morvern, but does occur in the Tertiary basalt of the Sound of Mull to the north-west (Wain-Hobson 1981). Secondly, the disappearance westwards across Mull is the combined result of a gradual deterioration in development (as described above) together with the glacio-isostatic tilt of the shoreline carrying it out of sight below sea-level in west Mull. In this area it is probably represented by the intertidal platforms around Gribun and Inch Kenneth, by McKinnon's Cave at Gribun and by Fingal's and other caves on Staffa (Walker et al. 1985). Thus Bailey et al. 's) line is very questionable as a glacial limit. 4. As well as the Morvern example quoted above, rock lithology is a significant factor in explaining many other contrasts in the distribution and development of the Main Rock Platform in western Scotland. A good example occurs on the Isle of Seil, south of Oban. In the south-west of the island black slate outcrops and the platform is in excess of 100 m wide with cliffs up to 25 m high over a continuous distance of 2-5 km. This contrasts sharply with the very poor development of the shoreline both to the north in the andesite around Easdale and to the south in epidiorite on the southern tip of the island. Thus Dawson's statement that the Downloaded from http://sjg.lyellcollection.org/ by guest on October 6, 2021

LETTERS TO THE EDITORS 229

FIG. 1. Locations mentioned in the text. Isobases (in m O.D.) for the Main Rock Platform (after Gray, 1978; Dawson, 1988) are shown by dashed lines. The solid line depicts the "N.W. limit of pronounced marine erosion" identified by Bailey et al. (1924). Downloaded from http://sjg.lyellcollection.org/ by guest on October 6, 2021

230 LETTERS TO THE EDITORS distribution of the shoreline "bears no relationship to rock lithology" could be misleading. 5. Dawson (p. 172) also discusses the possibility that the regional contrast in platform development "may be attributable to Lateglacial neotectonic activity" related to "renewed downwarping" or "dislocation" associated with the Loch Lomond Stadial limits. It is difficult to discuss this point since Dawson does not make it clear why this factor should have resulted in the contrasts observed in the field. 6. Another important factor in understanding the variations in development of the shoreline is degree of exposure. The shoreline is remarkably well developed in some very sheltered locations, yet on almost every island in the Firth of Lorn area the shoreline is significantly better developed on west facing (exposed) coasts compared with the (sheltered) east coasts. This is true, for example of , Seil, Luing, , Jura and numerous smaller isles. 7. Finally, there are some aspects of the distribution of the platform that are very difficult to explain. One of the most problematic occurs at Scarisdale on the southern shore of Loch na Keal on the . Here the isobases for the Main Rock Platform (Fig. 1) show that the shoreline should occur at c. 3 m O.D. Indeed there is a platform fragment at about this altitude between Dhiseig and Rubha na Moine (NM 507 367). However, immediately north-east of this site all the coastal rocks are heavily abraded and covered by p-forms (Gray 1981). If the Main Rock Platform were formed during the Loch Lomond Stadial why was coastal erosion so spectacularly differential? A possible solution lies in the word "if above. There is some evidence that a significant proportion of the erosion of the Main Rock Platform may have occurred prior to the Loch Lomond Stadial (Gray and Ivanovich, 1988). It is suggested that a complex history would explain many of the complexities in the distribution and development of the Main Rock Platform. In these circumstances perhaps the chronological term "Main Lateglacial Shoreline" used in the title of Dawson's paper is best avoided for the present. Thus, it is clear that there are several interacting factors involved in explaining the complex distribution and development of the Main Rock Platform. Most of the above discussion, however, involves qualitative assessments. A useful next step would be a quantitative multivariate analysis of the morphometry of the shoreline fragments, and the lithological and marine characteristics likely to have been involved in its formation.

REFERENCES BAILEY, E. B. et al. 1924. The Tertiary and Post-Tertiary geology of Mull, and Oban. Mem. Geol. Surv. Gt. Br. DAWSON, A. G. 1988. The Main Rock Platform (Main Lateglacial Shoreline) in Ardnamurchan and Moidart, western Scotland. Scott. J. Geol., 24, 163-74. Downloaded from http://sjg.lyellcollection.org/ by guest on October 6, 2021

LETTERS TO THE EDITORS 231

GRAY, J. M. 1974. The Main Rock Platform of the Firth of Lorn, western Scotland. Trans. Inst. Br. Geogr., 61, 81-99. . 1978. Low-level shore platforms in the south-west : altitude, age and correlation. Trans. Inst. Br. Geogr., New Series, 4, 151-64. . 1981. p-forms from the Isle of Mull. Scott, f. Geol., 17, 39-47. and IVANOVICH, M. 1988. Age of the Main Rock Platform, western Scotland. Palaeogeogr., Palaeoecol., Palaeoclimatol., 68, 337-45. PEACOCK, J. D. 1975. Quaternary of Scotland—Discussion. Scott. J. Geol. 11, 174-75. , GRAHAM, D. K. and WILKINSON, I. P. 1978. Late-glacial and post-Glacial marine environments at Ardyne, Scotland, and their significance in the interpretation of the history of the Clyde sea area. Rep. Inst. Geol. Sci., No. 78/17, 25pp. WAIN-HOBSON, T. 1981. Aspects of the glacial and post-glacial history of north-west Argyll. Univ. Edin. Ph.D. thesis (unpubl). WALKER, M. J. C, GRAY, J. M. and LOWE, J. J. Island of Mull, Scottish . Quaternary Research Association Field Guide, Cambridge.

J. M. GRAY Department of Geography, Queen Mary College, University of London, Mile End Road, London El 4NS

MS. accepted for publication 14th March 1989 Downloaded from http://sjg.lyellcollection.org/ by guest on October 6, 2021

Letter to the Editors

DISTRIBUTION AND DEVELOPMENT OF THE MAIN ROCK PLATFORM: REPLY

SIRS—The reply by Gray raises some interesting issues concerning the age and origin of the Main Rock Platform in western Scotland. The problem is of international importance owing to the suggestion in recent years that coastal erosion of bedrock is a particularly effective process in cold climate environments. This idea was developed by several Scottish workers (Sissons 1974; Gray 1978; Dawson 1980) and later applied both in Scandinavia and North America (Grant 1980; Rasmussen 1981). Recently Gray and Ivanovich (1988) have attempted to gain further information on the amount of bedrock erosion that may have occurred on the Isle of Lismore during the Younger Dry as. A speleothem from a cave associated with a limestone platform on Lismore provided a uranium-series date of 103 ka and hence casts doubt on the notion that the platform was principally eroded during the Younger Dry as. Gray develops these views further in his reply where he seeks to explain the sporadic development of the Main Rock Platform in Ardnamurchan and Moidart. I wish to discuss here four issues raised by Gray in order to clarify present views on the status of the Main Rock Platform and the The Main Lateglacial Shoreline.

THE STATUS OF THE MAIN LATEGLACIAL SHORELINE Gray (1974, p. 86) concluded that the Main Rock Platform is interglacial in age and considered that its regional tilting is attributable to long-term tectonic movements. However, Sissons (1974), in a now classic paper, argued that the Main Rock Platform may have been produced during the Lateglacial, mainly during the cold climate of the Loch Lomond Stadial. Sissons (1974) proposed that the Main Rock Platform was correlated with a Buried Gravel Shoreline in South East Scotland and argued that these features represented a single shoreline that he named the "Main Late-glacial Shoreline". Later, Gray (1978) rejected the conclusions of Gray (1974) and instead supported the view of Sissons (1974). Gray (1978, p. 162) concluded that the ". . . bulk of the erosion of the Main Rock Platform occurred during the Late-glacial". Recently, Gray and Ivanovich (1988), largely on the basis of the speleothem data described above, have rejected many of the arguments used by Gray (1978) in advocating a Younger Dryas age for the feature and have reverted to a model in which a polycyclic origin is favoured. The uplift isobases for the Main Lateglacial Shoreline in the SW Highlands are based on extremely detailed altitude measurements of cliff-platform junctions. Individual platform fragments are particularly easy to correlate with each other Scott. J. Geol. 25, (2), 233-238, 1989 Downloaded from http://sjg.lyellcollection.org/ by guest on October 6, 2021

234 LETTERS TO THE EDITORS due to the virtually continuous nature of the platform over many kilometres of coastline. The pattern of the shoreline uplift isobases in conjunction with the degree of glacio-isostatic tilting is consistent with shoreline formation during the Younger Dryas (Loch Lomond Stadial). Sissons (1974) argued that this pattern was attributable to bedrock erosion during the cold climate of the Younger Dryas. It is possible, as Gray suggests, that such rock erosion took place upon a pre-existing rock platform in parts of the SW Highlands. This may indeed prove to be the case (we do not know) but it does not alter the fact that shore erosion of bedrock during the Younger Dryas was sufficiently effective to produce a distinctive shoreline and it is this that has been measured in the field. How else can one satisfactorily account for the pattern of altitudes of the shoreline, which is in very good agreement with the sequence of glacio-isostatically deformed shorelines in western Scotland? For these reasons, I would argue most strongly that the term "Main Lateglacial Shoreline" should be retained. However, it is also clear that a potential problem exists in correlating widely-separated platform fragments with the Main Lateglacial Shoreline.

PROCESSES OF PERIGLACIAL SHORE EROSION OF BEDROCK In recent years, detailed investigations of rock platforms in selected lake areas of has provided valuable information on rates and processes of shore erosion of bedrock in present periglacial environments (Dawson et al. 1987). At one site, several rock platforms up to 5-3 m wide and eroded in gneiss could be demonstrated to have been produced along the margin of a former ice-dammed lake known to have existed for between 75 and 125 years during the Little Ice Age. It was concluded that the average rate of cliff retreat during this period was between 2-6 and 4-4 cm/year (Dawson et al. 1987). As a result of these and later studies, I have argued that it seems most likely that rock platforms are produced through the influence of annual freeze-thaw cycles in the intertidal zone which, through the promotion of segregation ice growth in bedrock beneath nearshore pack ice, may cause the loosening and eventual removal of large slabs of rock. Dionne (1988) has shown how effective this process is in removing bedrock slabs from rock platforms in the St Lawrence estuary and eastern Hudson Bay. If this process were responsible for the production of rock platforms during the Loch Lomond Stadial, then estimates of average cliff retreat rates for the Stadial assume a quite different meaning. For example, the removal of a large slab of bedrock by sea-ice during a single event may be followed by many centuries of negligible rock erosion. In this regard, I have observed evidence at several locations in Scotland, of large rock slabs associated with the Main Lateglacial Shoreline that demonstrate transportation to their present positions by sea ice during the Loch Lomond Stadial. Frost shattering on coastal cliffs during the Stadial was probably also of considerable importance in loosening blocks but its significance is difficult to quantify. Downloaded from http://sjg.lyellcollection.org/ by guest on October 6, 2021

LETTERS TO THE EDITORS 235

I have little doubt that the processes described above were operative on the coastline of western Scotland during the Younger Dryas and almost certainly enhanced due to pronounced seasonality caused by the occurrence of aphelion during winter (Vernekar 1972). However, the Norwegian research that has so far been conducted, although producing values for cliff retreat that are comparable with those estimated for the Loch Lomond Stadial (Dawson et al. 1987), has also indicated that the values of rock volume removal per year that have been calculated for a Main Rock Platform of Loch Lomond Stadial age are very high indeed. This is one of the principal reasons why I suspect that there may have been a pre-existing rock platform in many areas of the SW Highlands, yet not north of the Bailey et al. line.

THE CONTRAST IN PLATFORM DEVELOPMENT BETWEEN THE NW AND SW HIGHLANDS The principal purpose of the field research in Ardnamurchan and Moidart was to firstly test the model of Gray (1978; Figure 5C) who had published a map showing the uplift isobases for the SW Scottish Highlands. The map shows quite clearly that the Main Rock Platform should be present as a raised feature on the Scottish mainland north of Mull. However, the line published by Bailey et al. (1924) and the observations of McCann (1968) suggested to the author that the Main Rock Platform was either poorly developed or absent in this area. In the course of field mapping in Ardnamurchan and Moidart it soon became clear that the Main Rock Platform is absent from most areas of coastline yet in some areas it is often spectacularly developed. The research indicated that it was indeed valid to accept the notion of Bailey et al. (1924) that the strikingly developed rock platforms and cliffs in the SW Highlands contrast markedly with those in Arnamurchan, Moidart and . However, it was also clear that the platform fragments in Ardnamurchan and Moidart are glacio-isostatically tilted in a manner entirely consistent with the field evidence from the SW Highlands. Gray (Point 3) has suggested that the contrast is principally due to variations in rock lithology. I am well aware of this possibility. I believe it to be an incomplete explanation, however, because the regional difference in platform development between the two areas is too great. I agree with his citation of Bailey et al. (1924) that, "It is only after experience has shown that the deterioration is definitely regional that one is driven to propound a regional explanation". I am in no doubt that the regional contrast described by Bailey et al. (1924) is a real one and that it is not principally due to variations in rock lithology as proposed by Gray. Gray suggests that Bailey et al.'s line may simply be explained by contrasts in rock resistance between the massively jointed Strontian microgranite of southern Morvern and the Tertiary basalts of the Sound of Mull to the North West. Of course this is so but it does not solve the main problem. Bailey et al. sought to distinguish between two contrasting regions and it is on the explanation for this contrast between regions that we should focus our attention. In my view, the line Downloaded from http://sjg.lyellcollection.org/ by guest on October 6, 2021

236 LETTERS TO THE EDITORS drawn by Bailey et al. (1924), is principally related to the presence of a pre-existing rock platform throughout many areas of the SW Highlands that was subject to substantial erosion by periglacial coastal processes during the cold climate of the Loch Lomond Stadial. Gray (Point 2) suggests that the real contrast is between the Oban/Firth of Lorn area and more peripheral locations. However, the Oban/Firth of Lorn area is not the only area in which the Main Rock Platform is well developed. One example to demonstrate the incorrectness of this view is provided from Arran where some of the finest examples of the Main Rock Platform (even better than Mull!) are to be found. Indeed, the Main Rock Platform is excellently developed along many other stretches of the coastline (e.g. Bute, Cumbrae, Ayrshire). A very important factor, additional to those described by Gray, is the strike and dip of the foliation that is developed in the Dalradian quartzites, phyllites and schists of the SW Highlands. In areas where the dip is offshore (e.g. eastern Jura and eastern Knapdale) the platform is poorly developed. By contrast, platforms are better developed on western coasts where the dip is generally inland. The reason for this contrast is not clear apart from the possible relationships with the ways in which coastal rock platforms are physically produced. In my opinion, the key question is why in Ardnamurchan, Moidart and Knoydart there was no such platform available for re-trimming as there was in Mull, the Firth of Lorn, Kintyre, Arran and elsewhere along the Firth of Clyde. There are two possible explanations that deserve consideration and both are virtually impossible to prove. One reason for the difference might be the former occurrence of an ice mass part of which covered most of the , Moidart, Knoydart and Ardnamurchan yet which did not cover most coastal areas of the SW Highlands. Under such circumstances, it is possible that periglacial shore erosion could have produced rock platforms in one area and not in another. A former ice cap that covered the NW Highlands yet left large areas of the SW Highlands unglaciated would not have been greatly dissimilar in geography to that envisaged to have developed over the western Highlands during the Loch Lomond Stadial. Such an explanation does not preclude the presence of ice masses in the SW Highlands (e.g. on Mull). The critical requirement is that most coastal areas in the SW Highlands were not ice-covered. Gray considers that this explanation implies a tortuous ice margin but this is not so, particularly when one considers that some of rock platforms in the Sound of Mull may have been produced during the Loch Lomond Stadial and not during some earlier stadial. A second explanation is to invoke a model in which the rate of relative sea level rise in Moidart during the Loch Lomond Stadial was greater than in areas to the south. This type of explanation has been used before to explain why the suggested age equivalent of the Main Rock Platform in western Norway (the Main Line) is not such a well-developed feature as it is in Western Scotland. In the case of the Downloaded from http://sjg.lyellcollection.org/ by guest on October 6, 2021

LETTERS TO THE EDITORS 237

Moidart region, one way in which this could have occurred is through renewed crustal downwarping caused by the build-up of a Younger Dryas ice cap. Such an explanation is not so remarkable, particularly since Firth (1986) has provided evidence that the was subject to renewed crustal downwarping during the Loch Lomond Stadial due to ice build-up. At present, it is not possible to evaluate whether this process took place or not. It is known, however, that certain areas in Scotland have been subject to crustal deformation and even faulting during the Stadial. Indeed Gray (1978) and Ringrose (1987) have provided some of the most exciting information in this regard.

THE OCCURRENCE OF THE MAIN ROCK PLATFORM INSIDE THE LIMITS OF LOCH LOMOND STADIAL GLACIERS? The proposal by Gray (Point 1) that well developed fragments of the Main Rock Platform are present inside the generally agreed limits of the Loch Lomond Stadial is not so clear-cut as he seems to suggest. In support of his view he cites Peacock (1975) who provided field evidence from Corran, Loch Linnhe where the Main Rock Platform was reported to be present within the Loch Lomond Stadial ice limit. However, reference is not made by Gray to Sissons (1975) who maintained that Peacock's (1975) field interpretation was incorrect. Gray (Point 1) correctly states that care must be taken in implying the absence of Loch Lomond Stadial glaciers from the presence of well-developed Main Rock Platform fragments. Of course I agree and the Kinlochspelve evidence provides a good example of this point. Field mapping of glacigenic landforms and sediments which I have recently undertaken in the Loch Ailort/Loch Moidart region demonstrates that in this area, as in most other parts of the western Highlands, there are very few, if any, well-developed fragments of the Main Rock Platform located inside the limits of the Loch Lomond Advance. As far as I am aware, most, if not all, well-developed fragments of the Main Rock Platform in western Scotland occur outside the limits of the Loch Lomond Stadial glaciers. In conclusion, Gray has argued that the distribution and development of the Main Rock Platform is more complex than I suggest. I am fully aware of the complexity of platform evolution and am of the opinion that most of the examples used by Gray to demonstrate particular points can be countered by other examples that suggest different interpretations. I would argue most emphatically that the chronological term "Main Lateglacial Shoreline" should be retained. I am of the view that the evidence for significant coastal erosion of bedrock during the Loch Lomond Stadial is overwhelming. I can understand the logic in Gray's argument whereby he considers the role of rock lithology as crucial in the consideration of why there should be such a marked contrast in rock platform development in the regions north and south of Bailey et al. 's line. However, I would maintain that this hypothesis, on its own, cannot satisfactorily account for the regional contrast in platform development. I do certainly agree with Gray's suggestion that Downloaded from http://sjg.lyellcollection.org/ by guest on October 6, 2021

238 LETTERS TO THE EDITORS quantitative multivariate analysis of the morphometry of the shoreline fragments, and of the lithological and marine characteristics likely to have been involved in the formation of the Main Rock Platform would be a very useful step forward.

ACKNOWLEDGEMENTS

I am indebted to Professor D. E. Smith, Dr D. H. Keen and Mr D. I. Benn for comments on a draft of this letter.

ADDITIONAL REFERENCES

DAWSON, A. G. 1980. Shore erosion by frost: an example from the Scottish Lateglacial. In LOWE, J. J., GRAY, J. M. and ROBINSON, J. E. (eds.) Studies in the Lateglacial of North-West Europe. Pergamon Press, Oxford, 45—53. , MATTHEWS, J. A. and SHAKESBY, R. A. 1987. Rock platform erosion on periglacial shores: a modern analogue for Pleistocene rock platforms in Britain. In BOARDMAN, J. (ed.) Periglacial processes and landforms in Britain and Ireland. Cambridge University Press, 173-182. DIONNE, J.-C. 1988. Frost weathering and ice action in shore platform development with particular reference to Quebec, Canada. Zeit. Geomorph. N.F., Suppl.-Bd. 71, 117-130. FIRTH, C. R. 1986. Isostatic depression during the Loch Lomond Stadial: Preliminary evidence from the Great Glen, northern Scotland. Quaternary Newsl. No. 48, 1-9. GRANT, D. R. 1980. Quaternary sea-level change in Atlantic Canada as an indication of crustal delevelling. In MORNER, N.-A. (ed.) Earth Rheology, Isostasy and Eustasy. John Wiley and Sons, New York, 201-214. McCANN, S. B. 1968. Raised rock platforms in the western isles of Scotland. In BO WEN, E. G., CARTER, H. and TAYLOR, J. A. (eds.) Geography at Aberystwyth, University of Wales Press, 22-23. RASMUSSEN, A. 1981. The Deglaciation of the Coastal Area NW of Svartisen, Northern Norway. Nor. Geol. Unders. 369, 1-31. RINGROSE, P. S. 1987. Fault Activity and Palaeoseismicity during Quaternary time in Scotland. Univ. Strathclyde Ph.D. thesis (unpubl.). SISSONS, J. B. 1974. Late-glacial marine erosion in Scotland. Boreas, 3, 41-48. . 1975. Quaternary of Scotland1—Discussion. Scott. J. Geol., 11, 176—177. VERNEKAR, A. D. 1972. Long-period Global Variations of Incoming Solar Radiation. Meteor. Monograph 12(34), Amer. Meteor. Soc, 1-21.

A. G. DAWSON Department of Geography, Coventry, Polytechnic, Coventry, CV1 5FB

MS. accepted for publication 10th May 1989