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        Concerning early descriptions of pro-talus ramparts
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        Concerning early descriptions of pro-talus ramparts
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Sir

I should like to thank S.C. Porter (1987) and C.K. Ballantyne (1987) for their interesting letters concerning pro-talus ramparts, written in response to my previous comments (Butler, 1986). They make several points in their letters, and I should like to comment on some of these issues.

First, it was certainly not my intention to ignore or denigrate the contributions of geologists and geographers working in the British Isles, cited by Ballantyne (1987). I did not allude to those works because they do not describe pro-talus ramparts. Ballantyne cites three papers which he interprets as providing earlier written descriptions of protalus ramparts than that of Daly (1912). Ward (1873, p. 426) indeed did hypothesize a type of “moraine-like mound”, based on a suggestion from “Mr. Drew, late from Cashmere”, but did not actually provide any field description of such a feature in the Lake District. Furthermore, Ward’s descriptive mounds (note that he did not use the term ridge or rampart) could easily be interpreted as attributable to snow-avalanche impact (Corner, 1980). Ward’s brief comment cannot be construed as describing a pro-talus rampart.

The comments of Marr and Adie (1898) are also sufficiently vague as to preclude the establishment of primacy. Their statement that the angular blocks resting upon the sub-angular blocks of a moraine were “rather of the nature of snow-slope detritus” may again refer to avalanche-deposited materials. It is also clear that the feature in question was a moraine, which had undergone minor post-glacial modification.

The description of Gatty (1906) is, as Ballantyne states, “a remarkable account”. It is, however, a remarkable account of glacial moraines, not pro-talus ramparts. Both of Gatty’s (1906, p. 490, 491) photographs refer to the land forms in question as morainic dams (an item omitted in Ballantyne’s letter). A reading of Gatty’s description, as well as interpretations of the photographs, reveals that the ridges in question are weathered, stable glacial moraines. A veneer of some isolated, recently deposited clasts on the surface of a moraine does not make the moraine a pro-talus rampart.

The papers cited by Porter (1987) certainly do describe features later called pro-talus ramparts, and I thank him for calling them to my attention. I should be pleased to hear of other early descriptions of these land forms, and hope to hear from readers of the Journal.

Secondly, I have no dispute with Ballantyne or Porter concerning the entrenchment of the term “pro-talus rampart” in the literature. My advocacy of Daly’s (1912) term “winter-talus ridge” was based primarily on its primacy over the later terms “nivation ridge” and “pro-talus rampart”. In the light of Porter’s examples from the historical literature, this is no longer an issue. Ballantyne’s (in press) forthcoming paper, as well as the process studies cited by Porter, clearly shed doubt on the genetic accuracy of Daly’s term.

Finally, I completely agree with Ballantyne (1987) that the traditional definition of the term “pro-talus rampart” will eventually require revision and, in the light of Porter’s comments, that the term “pro-talus rampart” remains a viable and preferred one. The definition I presented (Butler, 1986) was simply a summary of currently utilized working definitions. The works of Harris (1986) and Ono and Watanabe (1986), works not published at the time my previous letter was written, indeed illustrate the problems with a morphogenetic definition based solely on one form of genesis. I am not, however, at this time prepared to adopt Ballantyne’s (1987) “more general definition”, particularly in the light of recent studies which attribute glacial origins to features previously described as owing their genesis to pro-talus processes (e.g. Gardner and others, 1983, p. 171). As pointed out by Madole (1972, p. 122), “the polygenetic origin of talus makes it both the most complex and ill-defined facies”, and as Porter states, much work obviously remains to be done before a thoroughly accurate definition will be available.

References

Ballantyne, C.K. 1987. Winter-talus ridges, nivation ridges and pro-talus ramparts. Journal of Glaciology, Vol. 33 No. 114, p. 24647.
Ballantyne, C.K. In press. Some observations on the morphology and sedimentology of two active protalus ramparts, Lyngen, northern Norway. Arctic and Alpine Research.
Butler, D.R. 1986. Winter-talus ridges, nivation ridges, and pro-talus ramparts. Journal of Glaciology, Vol. 32, No. 112, p. 543.
Corner, G.D. 1980. Avalanche impact landforms in Troms, north Norway. Geografiska Annaler, Vol. 62A, Nos. 12 p. 1-10.
Daly, R.A. 1912, Geology of the North American Cordillera at the forty-ninth parallel. Geological Survey of Canada. Memoir, No. 38.
Gardner, J.S., and others. 1983. The dynamic geomorphology of the Mt. Rae area: a high mountain region in southwestern Alberta, by Gardner, J.S. Smith, D.J., and Desloges, J.R. Waterloo, Ontario, University of Waterloo. Department of geography. (Publication Series No. 19.)
Gatty, V.H. 1906. The glacial aspect of Ben Nevis. Geographical Journal, Vol. 27, No. 5, p. 48792.
Harris, C. 1986. Some observations concerning the morphology and sedimentology of a protalus rampart, Okstindan, Norway. Earth Surface Processes and Landforms, Vol. 11, No. 6, p. 67376.
Madole, R.F. 1972. Neoglacial facies in the Colorado Front Range. Arctic and Alpine Research, Vol. 4, No. 2, p. 11930.
Marr, J.E., and Adie, R.H. 1898. The lakes of Snowdon. Geological Magazine, Decade 4, Vol. 5, p. 5161.
Ono, Y., and Watanabe, T. 1986. A protalus rampart related to alpine debris flows in the Kuranosuke cirque, northern Japanese alps. Geografiska Annaler, Vol. 68A, No. 3, p. 21323.
Peev, C.D. 1966. Geomorphic activity of snow avalanches. Union de Géodésie et Géophysique Internationale. Association Internationale d’Hydrologie Scientifique. Commission pour la Neige et la Glace. Division Neige Saisonnière et Avalanches. Symposium International sur les Aspects Scientifiques des Avalanches de Neige 5–10 avril 1965. Davos, Suisse, p. 35768. (Publication No. 69 de l’Association Internationale d’Hydrologie Scientifique.)
Porter, S.C. 1987. Early descriptions of pro-talus ramparts. Journal of Glaciology, Vol. 33, No. 114, p. 24748.
Ward, C. 1873. The glaciation of the northern part of the Lake District. Quarterly Journal of the Geological Society, Vol. 29, p. 42241.