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A Note on the Distribution of Drumlins in Great Britain

Published online by Cambridge University Press:  20 January 2017

J. Boardman
J. Boardman*
Affiliation:
Humanities Department, Brighton Polytechnic, Falmer, Brighton, East Sussex BN19PH, England
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Abstract

Comparison of recent maps of the distribution of drumlins in Great Britain reveals considerable discrepancies. Morphometric analysis and speculation regarding drumlin genesis require accurate maps.

Une note sur la distribution des drumlins dans la Grande Bretagne. Comparaison entre des cartes récentes pour la distribution des drumlins dans la Grande Bretagne révéle des inconsistances significatives. L’analyse morphométrique et spéculations concernant l’origine des drumlins demandent des cartes précises.

Zusammenfassung

Zusammenfassung

Eine Bemerkung zur Verteilung von Drumlins in Grossbritannien. Der Vergleich neuerer Kartierungen der Drumlin-Verteilung in Grossbritannien zeigt erhebliche Unstimmigkeiten. Die morphometrische Analyse und die Überlegungen zur Drumlinentstehung erfordern zuverlässige Kartierungen.

Type
Short Note
Information
Journal of Glaciology , Volume 28 , Issue 100 , 1982 , pp. 499 - 501
Copyright
Copyright © International Glaciological Society 1982

Reference Rose and LetzerRose and Letzer (1975) emphasize the importance of reliable maps in order to obtain meaningful morphometric data from individual drumlins. Equally necessary is accurate representation of regional distributions. For example, current speculation concerning drumlin genesis requires such information. Criticism of the model proposed by Reference Smalley and UnwinSmalley and Unwin (1968) includes comment on the distribution of drumlins in relation to ice margins (Reference Boulton, Boulton, Jones, Clayton, Kenning and ShottonBoulton and others, 1977). But there exists no map of drumlin distributions in Great Britain suitable for discussion of theories of drumlin formation.

Four recent attempts to record drumlin distributions in Great Britain are shown in Figure 1. A number of points concerning the sources for this figure should be noted.

Many published maps are based on one of the four sources used to draw Figure 1. For example, Reference Boulton, Boulton, Jones, Clayton, Kenning and ShottonBoulton and others (1977) used, and Reference Sugden and JohnSugden and John (1976) use a.

Detailed analysis of the differences between the maps is unnecessary. There is consensus on the fact that small areas around Glasgow, Carlisle, Morecambe Bay and the Tweed Basin possess drumlins. There are profound disagreements over areas such as Galloway, Kirkcudbright, West Cumberland Lowland. East Lothian, Fylde, Vale of York, Wensleydale, parts of Denbigh, and the Newtown area of Wales. A clear difference of opinion concerns Anglesey and Lleyn where perceptions vary from total cover to no drumlins. The exclusion of drumlins from south-west Scotland in Figure 1d contrasts with the other maps.

Objective assessment of the maps is difficult since the problem partly concerns the definition or “drumlin” and “major held”. Opinions vary as to the merits of detailed field mapping as against air photographs in the compilation of drumlin maps and no published assessment of the relative reliability of these techniques is known to the author. In the absence of such data, reliance on a combination of field mapping and air photographs would seem desirable.

Information provided with the originals of the Figure 1 maps does not include details of the methods of compilation. Use of either field mapping or air photographs must in some cases be doubted. For example, the widely reproduced photograph of drumlins at New Galloway, Kirkcudbright (e.g. Reference Curtis, Curtis, Courtney and TrudgillCurtis and others, 1976, p. 41; Reference SissonsSissons, 1967. plate IX) is taken in an area in which, according to Figure Id, no drumlins exist. It is also worth noting that Figure Id is derived from the largest-scale map of the four: increase in scale does not appear to guarantee an increase in accuracy.

In the four maps here considered, it could he claimed in mitigation that what is being mapped is, in each case, subtly different. However, future attempts to map drumlin distributions should be mindful of the need for clear definitions of what is being recorded (Reference Evans and CoxEvans and Cox, 1976) as well as adequate and clearly described mapping techniques (Reference Rose and LetzerRose and Letzer, 1975). Lack of precise definition will hamper progress on drumlin genesis and their significance as glacier bedforms (Reference Rose and LetzerRose and Letzer, 1977).

Acknowledgements

The author wishes to thank Mr J. Rose and Dr J. T. Andrews for critical appraisal of the manuscript. Mr S. Frampton drew Figure 1.

References

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Figure 0

Fig. 1. Distribution of drumlins in Great Britain according to four recent sources: (a) Embleton and King (1975), (b) Derbyshire (1978), (c) I.G.S. (1977), (d) Brown (1976), Waters (1976), Cullingford (1976).