Sir

I should like to thank Reference PorterS.C. Porter (1987) and Reference BallantyneC.K. Ballantyne (1987) for their interesting letters concerning pro-talus ramparts, written in response to my previous comments Reference Butler(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 Reference BallantyneBallantyne (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 Reference DalyDaly (1912). Reference WardWard (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 Reference Corner(Corner, 1980). Ward’s brief comment cannot be construed as describing a pro-talus rampart.

The comments of Reference Marr and AdieMarr 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 Reference GattyGatty (1906) is, as Ballantyne states, “a remarkable account”. It is, however, a remarkable account of glacial moraines, not pro-talus ramparts. Both of Reference GattyGatty’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 Reference PorterPorter (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 Reference DalyDaly’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 Reference BallantyneBallantyne (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 Reference Butler(Butler, 1986) was simply a summary of currently utilized working definitions. The works of Reference HarrisHarris (1986) and Reference Ono and WatanabeOno 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 Reference BallantyneBallantyne’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. Reference Gardner, Gardner, Smith and DeslogesGardner and others, 1983, p. 171). As pointed out by Reference MadoleMadole (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.