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Alain Godard on the NW Highlands of Scotland: present relevance for long-term landscape evolution studies

Alain Godard sur les hautes terres de l’Écosse du Nord-Ouest : pertinence actuelle des études d’évolution du relief à long terme
David Jarman
p. 177-203

Résumés

La thèse magistrale d’Alain Godard (1965) est examinée ici en tant que mine d’informations et matrice conceptuelle pour les études de géomorphologie régionale tant sur l’Écosse que sur les massifs anciens en général. Cette thèse sert aussi de matériau pour dresser un portrait des capacités exceptionnelles d’observation de son auteur, sa maîtrise de la géomorphologie structurale et climatique, et son art pour la synthèse des facteurs qui ont donné forme au paysage. Face à un tel monument, le présent article se limite à l’examen des Hautes Terres du nord-ouest de l’Écosse, et donc exclut cet autre vaste domaine de l’ouvrage relatif aux côtes et aux îles Hébrides et Orcades. On s’interroge sur les raisons qui ont entravé la notoriété des travaux de Godard au sein de la géomorphologie anglophone. Il s’agit des différences de culture scientifique évidentes mais fondamentales, notamment la préférence française pour les synthèses régionales contre l’accent mis sur les processus et études thématiques en Grande-Bretagne, à une époque charnière (1965) où s’opérait un changement de paradigme historique vers la process geomorphology au détriment de la denudation chronology davisienne. On évoquera aussi des barrières culturelles plus subtiles, comme le statut d’étranger sinon d’intrus dans la patrie de Hutton et Lyell, l’absence de traduction en anglais de l’ouvrage, et un style d’écriture et d’argumentation quelque peu désuet aux yeux de la nouvelle géographie « scientifique ». Ces barrières stylistiques, linguistiques et éditoriales soulignent des problèmes récurrents dans la diffusion transnationale d’idées scientifiques. Bien qu’on puisse rester critique à l’égard d’un certain manque d’originalité méthodologique chez Godard, son sens du paysage, sa compréhension de la géologie, et sa passion pour interpréter leurs interactions n’ont fait que peu d’émules parmi ses homologues britanniques. Lorsqu’il est mentionné dans la littérature, le magnum opus de Godard demeure essentiellement célébré pour ses levés topographiques extrêmement détaillés des surfaces d’érosion, exhumées ou non. Il est toutefois instructif que l’étude de l’évolution du paysage à long terme subisse actuellement une renaissance en Grande-Bretagne. Dans cette perspective et dans le contexte d’une bibliographie actualisée sur l’Écosse, on réévalue ici la qualité des analyses de Godard et leur rôle de ferment pour des recherches futures sur quelques thèmes devenus récemment à la mode en géomorphologie britannique comme l’efficacité à long terme de l’érosion glaciaire ; les conséquences morphologiques des processus d’altération ; les réseaux hydrographiques et la migration des lignes de partage des eaux ; la tectonique des marges continentales passives, et les traces de paléoreliefs hérités de l’orogenèse calédonienne.

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Errata

Article soumis le 28 mai 2006, accepté le 26 mars 2007.

Notes de la rédaction

Acknowledgements
I am immensely indebted to John Gordon, for his continuing encouragement and for lending me a copy of Godard for several years; to Yanni Gunnell for hand-holding this conversion of the original hommage; and to Adrian Hall for valuable discussions, for an extremely thorough review, and for resisting the temptation to rewrite it as magisterially as the subject deserves. I have not sought to interview Professor Godard, as the epistemological purpose here is to revisit the work as published and as available to British readers, and so this effort is not “tainted by his eclectic hindsight” Godard, 2006). Translations are by Fionn Petch and Yanni Gunnell, and graphics are by Susan Graham Design.

Texte intégral

Texte intégral en libre accès disponible depuis le 01 juillet 2009.

Aims and approach

1Alain Godard’s thesis, published in 1965, is perhaps the most substantial solo attempt at a comprehensive landscape evolution study of a large region in Britain, grounded in wide-ranging original fieldwork and observations, but achieving a broad synthesis of factors from ancient geology through Tertiary erosion to Quaternary glaciation and its aftermath. This reappraisal focuses on the mountainous core of his study area — the NW Highlands of Scotland — and skips over his work on the coasts, the Orkney and Hebridean archipelagoes, and the Tertiary Volcanic Province, as well as his climatic, hydrographic, petrological, and sedimentological analyses. Since his findings have never been published in summary form (apart from a few precursor papers on specific aspects), those unfamiliar with the tome itself will find a partial introduction to it in what follows.

2In revisiting a work over 40 years old, it would be egregious to criticise it as though it were published yesterday. It was not notably innovative in method or concept; its strength was to apply the entire armoury of available techniques and thinking to a given area, with the insight of a great structural geomorphologist possessed of a remarkable eye for landscape at all scales. From today’s perspective, it stands as a landmark broadly free of gross error or crass misinterpretations.

3The aims of this revisit are thus: (i) to identify Godard’s principal lasting achievements in upland geomorphology (drawn together in the concluding evaluation); (ii) to examine five of his main upland themes for their present relevance, as a spur to a renaissance in landscape evolution studies in Britain, and in the light of subsequent ideas or more recently acquired data [bracketed]: Tertiary planation surfaces [etch-planation], origins of the paleic relief [tectonics], glacial inefficacity [offshore deposits], watershed reconstruction and glacial breaching, and ice limits [trimlines, cosmogenic nuclide dating]; (iii) to convey the distinctive flavour of his thesis, with examples of his ability to unite geology and landscape, of his powers of landform observation, of his occasional blindspots and minor lapses, and of his hyperbolic and combative style; (iv) to explore the effects of style and language as both bridges and barriers in comprehending and communicating seminal geoscience; (v) to suggest that Godard’s initial reception and present standing in Britain have been inhibited by numerous factors, not only stylistic and linguistic, but including paradigm change, and fundamental differences in purpose between anglophone and continental geomorphology; (vi) to regret the lack of pursuit of Godard’s findings, and in the five themes to explore how he might have refined them had a challenging peer-group milieu existed; (vii) to discuss the rarity of ‘exogenous’ research by foreign geomorphologists in Britain, and to argue for greater cross-fertilisation between national schools, for re-exploration of well-studied areas as a test bed for new thinking, and for a return to ‘real geomorphology’ seeking to comprehend whole landscapes and disseminate findings to wider audiences. Since this revisit is the fruit of a belated encounter with the actual work, and has evolved from an amazed personal hommage à Godard, the story unfolds more readily if these post-rationalised aims are taken in approximately the reverse order.

Context: exogenous research in Britain

4Godard’s thesis is rare as a major exogenous (non-British based) contribution to the study of Scottish, and indeed British, geomorphology. Why should this be, and what do we lose thereby? There seem to be both scientific and cultural barriers to foreign research: echoing differences in fields as diverse as philosophy, literary studies, and energy policy. The political geography of geomorphological research has certain territorial and colonial tendencies, which allied to national differences in mindset and language can both sharpen its focus and inhibit dissemination and cross-fertilisation. In Europe, countries with strong schools of geomorphology such as Britain, France, Germany, Poland, or Sweden seem to monopolise their home territories. Conversely, some countries with abundant geomorphic (and other) interest can attract researchers from many quarters, as in Spain, Greece, Norway, and Iceland. And where a geomorphic entity is politically sub-divided, there can be a lack of synthetic spatial overview in the corpus of research, notably in the Alps, where mappings of ice limits (e.g., school of Schlüchter, Bern) or mass movements (e.g., schools of Crosta in Milan; Brückl in Vienna) tend to stay within national boundaries; in the Scandes, where studies of pre-glacial land surfaces deal mainly with the Swedish side of the border (Stockholm school) and would benefit from extending over the whole range (A. Stroeven, pers. comm., 2006); and indeed in the British Isles, where efforts such as Clayton and Shamoon (1999) viewing Great Britain as a whole impress by their rarity, and still omit Ireland.

5International research programmes tend to seek charismatic locations where processes are active, change is measurable, and results from exemplary sites and studies can be scaled up across broad zones. Geomorphologically, the British Isles are small, inactive and rather trivial, comprising a messy collage of landscape types in a transitional climatic context (neither sub-tropical nor arctic). Lacking wider relevance, they are thus generally the preserve of local-interest workers, although the French school (notably Battiau-Queney) has taken a valuable neighbourly interest in the SW peninsula and southern Ireland, integrating the Variscan fragments of Armorica (Godard et al., 1994, 2001).

6Within Scotland, the paucity of exogenous research can be illustrated from one comprehensive bibliography (Gordon and Sutherland, 1993), which for Quaternary geomorphology cites only six authors of non-UK origins and research base (including Godard). Of these, Agassiz (1841) was exceptional as an invited paradigm-changer, whose findings were assiduously published and promoted in English by his hosts. By contrast, Louis (1934) and Sölch (1936) were the first to identify wholesale glacial breaching of the main watersheds; published only in German, they were known to Linton and thence Godard, although not cited in this bibliography. Since then, only Godard’s might have been a seminal exogenous contribution, had it been more thoroughly read and widely disseminated over here. Had we enjoyed a stronger infusion of the French approach to geomorphology, we might now have a better appreciation of Scotland’s landscape evolution, which currently lags far behind the state of knowledge of Scotland’s geology, paleogeography, glacial and eustatic history, and process geomorphology (Trewin, 2002).

7And as to why Godard chose this particular region for his exogenous research, his own career review (Godard, 2006) simply acknowledges his mentor at Nancy, Guilcher, for steering him to the British Isles. He describes Scotland affectionately as his école de terrain even above the Massif Central [p. 14], but neither in the original work nor in subsequent publications does he place it in the context of comparator regions or develop its relevance for crystalline basements or passive continental margins.

Godard (1965): reception and present standing in Britain

8The published PhD is an extraordinary achievement, compiled over ten years (Rapp, 1960), and tackling a wide range of geomorphological issues over an extensive (25,000 km2) and diverse area covering the NW Highlands, Hebrides, and Orkney (fig. 1). It is difficult to grasp the depth of this commitment, when British PhDs have always been much shorter in timescale and more restricted in area or subject matter.

Fig. 1 Northwest Scotland, showing locations, features, and lithologies referred to in the text.
Fig. 1 Le Nord-Ouest de l’Écosse, avec toponymes, sites et lithologies mentionnés dans le texte.

Fig. 1 – Northwest Scotland, showing locations, features, and lithologies referred to in the text.Fig. 1 – Le Nord-Ouest de l’Écosse, avec toponymes, sites et lithologies mentionnés dans le texte.

The NW Highlands lie to the north of the Great Glen. 1: internal (etch?) basins; 2: Tertiary Volcanic Province; 3: Old Red Sandstone; 4: Moine thrust; 5: Strahconon fault; 6: Quoich line; 7: Kyle-Dingwall railway; 8: preserved meanders (KL: Kyle Rhea–Loch Long; LH: Loch Hourn; OY: river Oykell). LD: Loch Duich; SC: strath Croe.
1 : bassin interne (alvéole d’altération différentielle ?) ; 2 : Province volcanique tertiaire ; 3 : Vieux grès rouge ; 4 : chevauchement de Moine ; 5 :faille de Strathconon ; 6 : Quoich line ; 7 : voie ferrée de Kyle à Dingwall ; 8 : méandres conservés (K : Kyle Rhea–Loch Long ; LH : Loch Hourn ; O : rivière Oykell). LD : Loch Duich ; SC : strath Croe.

9However, it seems likely that the value of this magnum opus to British workers was diminished because: (i) it was unashamedly a classic regional physical geography in the French tradition, even though it went well beyond mere description and cataloguing, with a carefully-integrated synthesis; (ii) it had the misfortune to appear after the heyday of British physical geographies, just as the quantitative and methodological revolutions were transforming geomorphology; (iii) it was constructed out of reams of relatively anecdotal material, organised on a Guide Michelin basis rather than thematically as his Table des Matières proclaims and apparently collected as opportunities arose rather than to meet pre-specified research objectives (such simple honesty being out of fashion here); (iv) much of the data on which maps and conclusions were based was not presented, and many interesting points lacked illustration (e.g., the surviving rock-cut meanders, the géoflexure transversale, and the steep belt–flat belt transition instanced below); (v) the index was confined to main themes, making it impossible to track down specific observations; (vi) his style was verbose, declamatory, enthusiastic, and egotistical, all capital offences to the younger generation who wanted to leave behind the self-indulgent travelogue manner and make geomorphology a respectable science; even a paragon of the new virtue admits to being mocked for including the unscientific term “remarkable” in a title (Sissons, 1976b; Sissons, pers. comm.); (vii) he took a confrontational stance, robustly challenging leading workers in the area; yet he demanded observable facts when it suited him, while making sweeping assertions (e.g., “it cannot be denied”, “it is beyond all reasonable doubt”) whenever he lacked them; (viii) above all, his work was only available in French, and to read it properly required a great commitment of time, and much wrestling with his (or that language’s) wondrously elaborate syntax and rich vocabulary.

10A litmus test of its initial penetration is offered by Sissons (1976a), who cites Godard in respect of the pre-Devonian land surface, Tertiary planation surfaces and their warping, the supposed offshore drowned river network, and the distribution of cirque elevations. It may be significant that these are all subjects of Godard’s principal figures; however, his mapping of a preglacial drainage system and watershed displacements is omitted. Since then, the lack of follow-up research to test and expand upon his ideas has prevented the emergence of an informed critical debate. Indeed only one of his eighteen full-doctorate students has addressed Scotland: Le Cœur (1994) applies updated approaches including an etch-basin typology to the Inner Hebrides, but again most of this work remains unpublished.

11Today, in speaking to Scottish geomorphologists one generally finds Godard regarded as little more than a vast footnote to history, if not as grotesque an outpouring as Charlesworth’s 2300 pages (1957); they might agree that it had some interesting material and ideas, but regret that these were mostly lost in non-translation; they would only refer to it fleetingly if at all for any contemporary relevance. In geological circles, Godard is neither cited in Trewin (2002) nor even mentioned in a well-referenced wider-audience book on the geohistory of his study area (Rider, 2005). A current study modelling the Caledonian erosion surface and comparing it with present day topography across Highland Scotland was not aware of Godard’s mapping of it (D. Macdonald, pers. comm. 2006).

12Nevertheless, the most recent overview of Scotland’s landscape evolution (Hall and Bishop, 2002) still refers to Godard (including three of his precursor papers) to evidence some fundamentals: three Neogene stages of uplift, including warping of erosion surfaces (also citing Le Cœur, 1988); exhumed sub-Torridonian, sub-Devonian and sub-Triassic surfaces; the importance of deep (chemical) weathering in pre-Quaternary relief development; the existence of inselbergs of position (as against those of resistance or exhumation). And Ballantyne (2007) still attributes to Godard the first detailed and substantially sound descriptions of the massive landslips along the Tertiary Volcanic Province escarpments (even citing his splendid description of The Storr as cette topographie anarchique).

13Since Godard’s career in geomorphology is founded on this epic work, the reasons why he never published his findings in English (conscious decision, lack of time, translation difficulties, or inability to find a publisher?) would be of interest. Even his ten satellite papers on Scotland are all but one in French journals (Godard 1957, 1961). In retrospect (Godard, 2006) he extols the scenery of Scotland, but is silent as to the reception of his thesis in Britain, and its lasting value or influence; perhaps it is difficult to maintain enthusiasm for an area when there is virtually no ‘feedback’ from it on one’s findings.

Comprehending Godard: communicating geoscience

14These questions of style and language are not trivial, because they mediate the transmission of scientific information. First impressions count for a great deal, and obstacles to ready comprehension deter pursuit.

15Since a survey of those who have read Godard is impractical, a personal account must illustrate the vicissitudes. After long awareness of Godard as an exotic reference to do with planation surfaces, the writer borrowed a copy in 2002, out of idle curiosity. With a typically basic command of French, it took several weeks to become acquainted with even that half of Godard dealing with the more mountainous areas; many revisits were required to digest it and explore further. Few can afford such quixotic dedication, which was sustained largely by the verve with which Godard writes. Even so, the writer’s initial scribbled reactions were mixed: “persevering through the flowery prose morasse... self-indulgent regional descriptive tradition... an absorbing wealth of detailed observation and insight” albeit this was “frustrating as he hardly touches the main mountain areas, which he admits were too difficult of access”. But reactions such as “language delightful, refreshing enthusiasm, wonderful selection of words” attest to his compelling style and rich vocabulary (see Appendix 1, and samples of his phraseology in the original French throughout the paper). Had the same issues been written up in the arid, anonymous, condensed manner of present-day mid-Atlantic geoscience, it would quite probably have deterred such diligence.

16This is neither an attribute unique to Godard, nor the last gasp of a former, more expansive era. One might say his style is very French, except that Linton and his predecessors also cultivated an eloquent and magisterial manner. But in recent years, and with respect to crisply entertaining authors such as Stoddart or Goudie, France may have become a last bastion of the principle that original science can be written as literature, with a personal stamp and conviction, with a passion to engage, communicate, and persuade. For the present writer to take delight as well as profit from reading (also in French) a thesis on a subject as esoteric as Les versants du Spitsberg (André, 1993) attests to a continuing tradition. Even in translation, sparks of creative language can still fly (Lageat and Gunnell, 2001).

17A further great merit of Godard is that his entire corpus of research on NW Scotland is comprised in a single work. For the general customer, this is invaluable, by contrast with the present absurdity of splitting PhD findings into multiple papers, with all the drawbacks of access, duplication, inconsistency, and lack of a unifying train of thought that this entails. By contrast, in History and Archaeology it is still quite common to write a single book based on the thesis. It would help geoscience disseminate its endeavours and reach a wider audience if authors were encouraged to take time to collect their thoughts, to hone their communication skills, and even to deploy language as imaginative as that anthologised in Appendix 1. Indeed, an updated Godard with its grand sweep, vivid examples, and pungent style would make a valuable quarry for a programme on the scenery of Scotland.

18In now proceeding to explore the thesis, references in square brackets thus [145], [fig. 42], etc. are to pages and illustrations in Godard (1965); locations mentioned are shown on fig. 1.

The shape of the land: uniting geology and physical geography

19More than any other work known to the writer, Godard’s thesis addresses the question “why is this land shaped like this?” perhaps reflecting his early architectural enthusiasm for la géométrie des formes (Godard, 2006). He tackles the question with unflagging passion, while stopping just short of the sentimentality of the mere topographer. He operates on two levels simultaneously, always looking for the big picture, the grand generalisation or verdict, but always alert to the reality of specific sites, whether they support the overview or stand out as exceptions to be accounted for. He is aware of processes, but his fieldwork rarely attempts to measure them; he is interested in the issue of rates of erosion, but in the absence of data of his own or in the literature he is reduced to airy speculation. Given his diligence in quantifying many elements (pebble shape and size, corrie elevation, clay minerals) it is intriguing to imagine how he might have utilised the techniques that have since become available.

20Above all, Godard brings to this question the training of a geologist combined with the perspective of a physical geographer. This parallels a British tradition going back to the Geikies and manifest in textbooks such as Holmes and Sparks. Sadly, this has fallen victim to specialisation. There has been no leading landscape geomorphologist in Scotland in recent times with strong geological roots, and vice versa. Thus there is no standard work which integrates the two: Sissons (1967) published his still-unsurpassed Evolution of Scotland’s Scenery at too early a stage in his career; while packed with insights into aspects of the landscape, it is not grounded in geology, his opening chapter on Rocks and Relief being derivative; Sissons (1976a) is updated but slimmer; and unlike Godard, he factorises rather than integrates the landscape. The Geology of Scotland over its several editions (Trewin, 2002) makes no pretence of considering the surface expression of bedrock and structure. A recent work on Geology and Landscapes of Scotland aimed at a wider audience (Gillen, 2003) is excellent on individual features, as befits a geologist, but covers the shaping of the entire Grampian mountain range in a paragraph.

21Godard’s instinct for geology and landscape is omnivorous, for example: (i) the shapes of the Assynt-Coigach inselbergs are interpreted with exceptional closeness, not least to disprove their glacial origin. Intriguingly, he attributes the larger extent of Quinag (as an inselgebirge) to a lower frequency than usual of faults and dykes in the Lewisian basement on which it stands, plus its position above a hollow in the pre-Torridonian surface [145]; (ii) Seana Bhraigh and the Freevater group are recognised as montagnes massives… succèdent brusquement vers le Nord … des plateaux assez réguliers d’altitude médiocre [116]. He interprets this bold step of 400 m in identical Moine lithology as a géoflexure transversale from Ullapool to Dornoch. It fronts a 20-km gap between the Beinn Dearg and Ben More Assynt massifs which is the most substantial doorway (Rudberg, 1992) in the main mountain axis of the Highlands. Yet although noticed by Peach et al. (1912) it has attracted little attention, and is hard to explain by fluvial or glacial breaching; (iii) he asks why the mountains of North Harris and the low plateau of South Lewis are cut in the same gneiss, finds no petrological differences, and infers a tectonic role [226]; (iv) the Inchbae internal basin is conventionally associated with differential erosion in the Inchbae augen-gneiss, and Hall (1991) proposes similar lithological explanations for the basins of NE Scotland. But Godard points out that the basin englobe the igneous intrusion [317], and is etched equally across Moinian psammites and the weaker Old Red Sandstone (ORS) deposits. Even so, he notes that the augen-gneiss is especially resistant to linear incision, yet vulnerable to chemical weathering, thus favouring etching and inverted topography; however his tectonic and erosion-surface explanations for the adjacent Carn Chuinneag augen-gneiss forming distinctive summits are less convincing; (v) the marked contrast between the high, dissected mountains of the Western Highlands and the lower-key terrain separating them from the Great Glen is conventionally attributed to the steep-dipping–flat-lying transition within the Moine schists (the Quoich Line). Godard notes this, but observes that the steep-belt nevertheless has traces of an undulating highest surface bevelled across it, while the flat-belt terrain rises appreciably to the main watershed where it zig-zags west-east across the Great Glen. He suggests that the more subdued relief in the flat-belt must be attributed to an intermediate planation advancing more readily but incompletely across it [324], geological factors and time-constrained geomorphological processes both contributing to the current landscape.

Godard’s powers of geomorphological observation and relevance today

22Godard is exceptional in his ability to characterise the different mountain groups; for example, to describe Ben Hope and its geologically disparate neighbours as les témoins d’un ancien rempart bien démantelé facing the north coast [109] brings them into refreshing perspective. Countless landscape insights, large and small, are buried in Godard’s text. Some are exhumed in the great final synthesis, but many are all too easily missed: (i) he discerns le relief appalachien in present landscapes as disparate as volcanic Ardnamurchan, the environs of Gairloch, and isolated Eday in Orkney; he applies it with more interpretative force to the ORS-buried quartzite ridges of Caithness. This unexpected analogue does not appear in Sissons (1967) or Gillen (2003), but may not be original [178, 550, 566]; (ii) he is able to portray what we are accustomed to regard as some of the most rugged wild land in Britain (coastal Knoydart, Morar, Ardgour) as a paysage plus aéré et moins sauvage than the high and deeply dissected mountains just inland. He attributes this to advancing planation creating an intermediate plateau landscape, which was then subjected to differential glacial erosion [300]. It takes Godard to show us a possible wood for the trees; (iii) he draws attention to sequences of rock-cut meanders in the Oykell valley [293], on a grander scale at Loch Long–Kyle Rhea [355], and more doubtfully in the course of Loch Hourn [612], which he suggests must predate glaciation. These may be isolated survivals, or not even mature river products, but they still demand explanation: for example, above sinuous Loch Long there is in fact a straight-sided glacial trough at 200 m asl (above sea level); (iv) he identifies nunataks above the ice sheet such as An Teallach and Ben More Assynt from their pointed, frost-shattered summits, contrasting with the surfaces plus lourdes rabotées par les glaciers elsewhere [604].

23While large swathes of Godard might now be passed over as Victorian in their eclectic observations and opportunistic measurements, including countless petrological and fabric analyses, there is a core, which addresses major issues that are still relevant and far from being resolved. It might be thought that Scotland, as a small country where geoscience originated and with a strong research capacity in geomorphology, has been studied to death, but this very familiarity makes Scotland an excellent test bed for new ideas. Regrettably the direction of effort by funding bodies to exotic locations in recent decades leaves many of the challenges raised by Godard still to be pursued. There are some signs of reawakening interest in the landscape evolution of Scotland after long neglect (Bishop et al., 2005), and five themes from Godard are here explored as a prompt to reappraisal with the benefit of contemporary techniques and mindsets.

Theme 1: Tertiary planation surfaces

24Godard is most often cited for his identification of a sequence of five Tertiary planation surfaces (Gordon and Sutherland, 1993; Hall and Bishop, 2002). This may be his best-known contribution because it is prominent on a fold-out map [his Carte VI], and is accessibly summarised in the text [572–587]. It is a readily-grasped concept: in today’s media-speak, it has sound-bite quality. The validity of Godard’s system of surfaces is today generally accepted, even though his and subsequent interpretations of their origins remain unconvincing (A. Hall, pers. comm., 2006); this is still one of the most vexed issues in Scottish geomorphology.

25To place Godard in his context, two kinds of surface must be distinguished: the erosional bench, most apparent from mapwork especially when miles wide and fragmented, and the summit accordances best seen by eye, although the almost exactly equal altitudinal heights of some groups of peaks can dangerously reinforce such impressions. While the rival marine and sub-aerial theories could apply to both kinds, presumably only the latter is amenable to interpretation as late-stage Davisian peneplanation.

26It now seems remarkable that as late as 1966, leading workers such as George and Jardine could still advocate extensive marine planation to explain the summit surface. Godard finds their Achille’s heel in the requirement for absolute horizontality. Thus he lampoons Hollingworth’s statistical correlations as requiring to postulate l’absence de tout gauchissement des niveaux [572]; while Godard is thinking mainly of regional warping, we can add local tectonic displacements and differential glacio-isostatic recovery as negating numerical accordances (affection for which still lingers: e.g., “the elevated surfaces... represented by plateaux and coincident summits” Trewin and Rollin, 2002).

27Godard emphasises that his surfaces are not level, locally or regionally, although he is not the first to avoid this trap, following with scant acknowledgement Geikie, Peach and Horne, and Fleet (Sissons, 1967): (i) his fragmentary surface supérieure is traced across the highest plateaux and just below residual peaks such as Foinaven. It is allowed to undulate considerably, providing it remains calme (fig. 2).

Fig. 2Sgurr nan Conbhairean (1105 m), one of the higher peaks in the Scottish NW Highlands, a pyramide résiduelle assez lourde [325].
Fig. 2 Sgurr nan Conbhairean (1105 m), une pyramide résiduelle assez lourde [325] et l’un des plus hauts sommets dans les Hautes Terres de l’Écosse du Nord-Ouest.

Fig. 2 – Sgurr nan Conbhairean (1105 m), one of the higher peaks in the Scottish NW Highlands, a pyramide résiduelle assez lourde [325].Fig. 2 – Sgurr nan Conbhairean (1105 m), une pyramide résiduelle assez lourde [325] et l’un des plus hauts sommets dans les Hautes Terres de l’Écosse du Nord-Ouest.

Note the tip of its smooth cone, which probably rose higher before truncation by the deep cirque behind the left shoulder. The paleic surface comprises a distinct monadnock swelling steeply from the broad bench at 950–1000 m well seen to its right. The summit and shoulders are probably below the main periglacial trimline, but appear only lightly glaciated. Godard did not map his surface supérieure in this area. View east from A’ Chràlaig (1120 m), a similar monadnock with scantier traces of paleic relief. Photograph: D. Jarman.
Noter la pointe émoussée de son sommet, qui s’élevait probablement plus haut avant d’être réduite par la morsure profonde du cirque en arrière de l’épaulement situé sur la gauche. La surface paléique comporte un monadnock qui se dresse nettement au-dessus de la large banquette à 950–1000 m, visible sur la droite. Le sommet et les épaulements se situent probablement au-dessous de la limite glaciaire, mais ne semblent avoir subi que de légères modifications par l’érosion glaciaire. Godard n’a pas effectué le levé topographique de sa surface supérieure dans cette région. Vers l’est, on observe d’A’ Chràlaig (1120 m) un monadnock semblable avec des vestiges plus réduits du relief paleique. Photo : D. Jarman.

28West of Inverness it displays a bombement to attain 800–1000 m asl; it declines to 600 m in the far north, but southwards it is lost to extreme dissection; (ii) his not-quite-a-surface hauts paliers d’érosion et fragments perchés de haute surface comprise sparsely scattered interfluves and benches at 650–750 m asl (fig. 3); (iii) his magnificently conserved surface intermédiaire is best displayed on Tertiary Volcanic Province and Caledonian granite plateau fragments. It rises from 400 m asl to a central 600 m, suggesting domed uplift; (iv) his well-known surface écossaise is characterised by le knick brutal at its inland limits. It slopes gently (3–4° is cited at one point), and lies within a band of 200–300 m asl, which in a disconcerting nod to the flat-earth tendency he finds echoed all round the British Isles [581]. Endearingly, he admits to so terming it to avoid having to assign any age or mode of origin to it [579]; confusingly he also calls it the aplanissement écossais; (v) his lowest niveau pliocène around the coasts and up valley benches is the most extensive, embracing a heterogenous collection of features between 90–180 m asl, and can often slope by that height range [584].

Fig. 3 Extensive upland erosion surfaces in Easter Ross partly mapped by Godard. Viewed from Diebidale Ridge (691 m) looking west to Beinn Dearg, the northernmost summit in Scotland over 1050 m asl (A).
Fig. 3 Hautes surfaces d’érosion de grande étendue en Easter Ross, partiellement cartographiées par Godard. A : vue vers l’ouest depuis Diebidale Ridge (691 m) on aperçoit Beinn Dearg, le sommet (à 1050 m d’altitude) le plus septentrional de l’Écosse.

Fig. 3 – Extensive upland erosion surfaces in Easter Ross partly mapped by Godard. Viewed from Diebidale Ridge (691 m) looking west to Beinn Dearg, the northernmost summit in Scotland over 1050 m asl (A).Fig. 3 – Hautes surfaces d’érosion de grande étendue en Easter Ross, partiellement cartographiées par Godard. A : vue vers l’ouest depuis Diebidale Ridge (691 m) on aperçoit Beinn Dearg, le sommet (à 1050 m d’altitude) le plus septentrional de l’Écosse.

Foreground: not identified by Godard as a surface, but identical to hauts paliers. Middle ground: mapped as hauts paliers d’érosion; beyond them, slightly lower uplands (not well seen) are mapped as surface intermédiaire. Right skyline: Carn Bàn plateau 4x10 km, boldly swelling summits 845-822 m mapped as surface supérieure, other selected benches and outliers as hauts paliers;. Left skyline: mountains of the Beinn Dearg massif, eight fragments mapped as surface supérieure despite summits ranging between 927 and 1084 m (most fragments sub-kilometric, but Am Faochagach partly seen extreme left is one of Godard’s three largest at 3x2 km). The entire ensemble forms a coherent, smoothly hilly preglacial landscape, the three mapped surfaces merging with few pronounced breaks other than glacial troughs (the narrow axial trough of Gleann Mor–Gleann Beag is unseen beyond the middle ground, and is ~300 m deep). Photography: D. Jarman.
Le premier plan, quoique non identifié par Godard comme une surface, est identique au second plan, identifié comme un haut palier d’érosion. Derrière ces niveaux, les terrains à peine en contrebas sont signalés par Godard comme surface intermédiaire, bien que la distinction soit peu perceptible. Sur l’horizon, à droite, plateau de Carn Bàn (4 x 10 km), sommets proéminents à 845-822 m attribués par Godard à la surface supérieure, et autres banquettes et pics isolés identifiés comme hauts paliers. Sur l’horizon, à gauche, montagnes du massif de Beinn Dearg, huit fragments identifiés comme surface supérieure malgré l’altitude des sommets entre 927 et 1084 m (la plupart des fragments font moins d’un kilomètre carré, sauf Am Faochagach, visible à l’extrême gauche, l’un des trois plus grands : 3 x 2 km). L’ensemble forme un paysage pré-glaciaire lisse et vallonné, mais cohérent. Les trois surfaces identifiées se recoupent sans ruptures topographiques marquées en dehors des brèches formées par le creusement glaciaire (l’étroite dépression linéaire de Gleann Mor–Gleann Beag, qui n’est pas visible au-delà du second plan, est profonde de ~300 m). Photo : D. Jarman

Fig. 3 Extensive upland erosion surfaces in Easter Ross partly mapped by Godard. Viewed from Dunan Liath (691 m) looking north to Bodach Beag (822 m) and Càrn Alladale (B)
Fig. 3 Hautes surfaces d’érosion de grande étendue en Easter Ross, partiellement cartographiées par Godard. B : vue vers le nord depuis Dunan Liath (691 m) en direction de Bodach Beag (822 m) et Càrn Alladale.

Fig. 3 – Extensive upland erosion surfaces in Easter Ross partly mapped by Godard. Viewed from Dunan Liath (691 m) looking north to Bodach Beag (822 m) and Càrn Alladale (B)Fig. 3 – Hautes surfaces d’érosion de grande étendue en Easter Ross, partiellement cartographiées par Godard. B : vue vers le nord depuis Dunan Liath (691 m) en direction de Bodach Beag (822 m) et Càrn Alladale.

Foreground: hauts paliers above Gleann Mòr glacial trough; middle ground: broad ridge descending gently eastward, mapped as small fragments of hauts paliers (left) and surface intermédiaire (right edge), but with no obvious distinction; skyline: small widely separated fragments of surface supérieure, hauts paliers, and surface intermédiaire from left to right. Most of skyline not assigned to any surface. Photography: D. Jarman.
Au premier plan, hauts paliers au-dessus de la dépression glaciaire de Gleann Mòr. Au second plan, large crête descendant vers l’est, identifiée comme un ensemble de petits fragments des hauts paliers (gauche) et de surface intermédiaire (bord droit), mais sans critère de distinction très nets. Sur l’horizon, de droite à gauche, petits fragments espacés de la surface supérieure, de hauts paliers et de la surface intermédiaire. La majeure partie de la ligne d’horizon n’est attribuée à aucune surface. Photo : D. Jarman

29Godard is excellent in conveying the character of these surfaces as they are encountered, and their relations to lithology and structure, post-formational tectonics, and correlative deposits. He perceptively infers climatic environments and processes, and estimates their descending ages from these inferences and from cross-cutting relations, all with very little hard or datable evidence to go on. Unfortunately, he gives neither the criteria employed in his identification and mapping of these surfaces, nor worked examples of how they are to be distinguished in any sequence. This would have been especially important given that their absolute height ranges merge (Sissons, 1976a). His method relies on une très large mesure au patient travail de reconnaissance sur le terrain [572], with mapwork, sections, and air photos only utilised secondarily. We have to take on trust that les grands plans inclinés can be seen in the field, but not on even the best maps. Yet when his Carte VI is taken into hills such as Easter Ross where broad surfaces seem well-developed (fig. 3), admiration of his perceptiveness is tempered by bewilderment. Especially at the upper levels, countless rather uniformly distributed fragments have been selected when much larger areas would seem equally qualified; in the not atypical area of fig. 3, only 10% of the terrain is assigned to the upper three surfaces, and entire interfluves are overlooked while adjacent ones are embraced.

30Godard assigns all these surfaces to the Cenozoic. The hauts paliers, for example, cut the Paleogene Volcanics, but quite how they can be traced with confidence to a single base-level event effective from Skye to the east coast is unclear. Contrarily, although the surface intermédiaire best displays deformation [573], he cannot reconstruct its isohypses in the Volcanics or adjacent West coast because of later tectonic movements.

31The five surfaces have essential if unacknowledged differences of character. One (intermédiaire) is mainly a bevelled plateau. One (écossaise) is a broad pediment below a degraded scarp with its characteristic knick. Two (pliocène; hauts paliers) include both plateau fragments and benches, but without mention of knicks backing them. And the surface supérieure is a rolling landscape with occasional monadnocks. But Godard does not consider different geneses (e.g., plateaux from downwearing, benches from base-levelling) nor indeed whether the upper two or even three plateau surfaces could be related. Above about 600 m asl, they share similar smooth signatures in air photos, and could all be integrated into a single preglacial land surface of greater overall relief (fig. 3; fig. 4); indeed Gjessing (1967) made such a suggestion, with contemporaneous development of paleic forms at all elevations adjusting to local base level (p. 109). Interestingly, Le Cœur is also a ‘lumper’ rather than a ‘splitter’ of erosion surfaces.

32With hindsight, Godard’s key concept is a staircase of Cenozoic surfaces, a previsioning of the multi-storeyed landscapes in passive margins (Godard et al., 2001). But although the treads of this staircase occupy about half the terrain (at least at lower levels), it is not clear what status is assigned to the other half: the white spaces on Carte VI. These intervening strips are too pervasive to be simply the risers between sub-tropical pediments, and they can hardly be attributed to blurring by glaciation. The risers illustrated by Peulvast in Norway and Lageat in South Africa (in Godard et al., 2001) appear relatively abrupt: crucially, Godard does not give any cross-sections relating his surfaces (fig. 4A). Have these strips evolved coevally with the surfaces at their feet, or do they represent degradation of original scarp-like risers, encroaching into the surfaces above, and if so over what timescales?

33The survival of plateau fragments and mountain tops can be understood within the framework of selective glacial erosion, but it is less obvious how staircase elements might survive, especially at lower levels. Indeed Godard anticipates that le véritable knick, found where the surface écossaise terminates brutalement against slopes as steep as 25°, is vulnerable to the criticism how has it survived glaciation? and responds with a teasingly seductive straw man: so it must be an early Quaternary marine planation cliff line then [582]. This proposition is then sledgehammered on six counts, all didactically compelling, but the original question still begs more discussion (see glacial inefficacity below).

Etch planation?

34Indeed Godard leaves the processes by which his surfaces extend rather vague, a longstanding criticism of the sub-aerialists (Sissons, 1976a). His researches just precede the advent of etch-planation, which Hall (1991) identifies as the key process in humid sub-tropical Tertiary erosion in the Highlands, and much of what he describes anticipates this model. Thus he recognises internal basins (cuvettes, for which he later coined the term alvéoles) as part of erosion surfaces, with evacuation of weathered debris via main rivers; he frequently notes the adjustment of relief to geology, which is fundamental to etching, although he observes bevelling across the grain just as often; and he sees his surface écossaise in particular as best explained by des processus de planation latérale dans un materiel inégalement altéré... sous climat de savane ou semi-aride [582]. Of course, earlier planation surfaces are likely to become progressively more modified, but it is unclear whether his identification procedures allow for this.

35The opportunity is not taken in Godard et al. (2001) to retro-apply the etch-planation concept to Scotland, although a not entirely convincing small example in similar glaciated schistose terrain in Labrador is illustrated in its fig. 3.3. One problem is that Godard’s simple notion of un soulèvement saccadé or staged uplift [573], triggering successive erosion-surface ramifications, requires all surface elements to be attributable to a specific marine base-level stillstand. But since planation can presumably propagate from any resistant rock barrier or tectonic break creating a local base-level, there must in practice be an increasingly anarchic overlapping of locally and regionally originated surfaces over time. Thus Godard’s cuvettes cannot be assumed to have similar dates and modes of origin; basins such as Atholl, Spean, Naver [279], or Shin [283] (fig. 1) are at different elevations, drain to four structurally separate sea areas, and have differing geological enclosures. It would be intriguing to have a Godardian structural geomorphologist analyse a basin with several possible controls such as Monar (fig. 4) with the benefit of etch-theory.

Fig. 4 The Monar internal basin, Wester Ross, immediately east of the main Highland watershed, a testing ground for etch processes and erosion surfaces. For location see fig. 1.
Fig. 4 Le bassin intérieur de Monar, Wester Ross, juste à l’est de la ligne principale de partage des eaux : un laboratoire naturel pour mettre en regard processus d’altération différentielle et surfaces d’érosion (localisation : fig. 1)

Fig. 4 – The Monar internal basin, Wester Ross, immediately east of the main Highland watershed, a testing ground for etch processes and erosion surfaces. For location see fig. 1.Fig. 4 – Le bassin intérieur de Monar, Wester Ross, juste à l’est de la ligne principale de partage des eaux : un laboratoire naturel pour mettre en regard processus d’altération différentielle et surfaces d’érosion (localisation : fig. 1)

A: form of Monar basin with surrounding fragments of Godard’s three highest surfaces and additional paleic relief. 1: Monar basin outlined by the 457 m (1500 feet) contour; 2: main Highlands watershed; 3: inferred pre-glacial watershed; 4: glacial breaches; 5: glacio-fluvial incision; 6: Monar gorge; 7: Strathconon fault; 8: gulls-wing upland drainage. The sections confirm Godard’s identification of multi-storey relief surrounding the basin, which displays marked asymmetry in section A1. Note that valley widths at the 457 m contour, just 10 km east of the watershed, are 1.5 km for the Meig and the Orrin, 2 km for the Cannich and the Affric, and 4 km for the Monar.
A : le bassin de Monar avec les fragments des trois surfaces les plus élevées de Godard et l’ajout du relief paléique. 1 : bassin de Monar souligné par l’isohypse 457 m (1500 pieds) ; 2 : ligne de partage des eaux des Highlands ; 3 : ligne de partage des eaux hypothétique pré-glaciaire ; 4 : trouées glaciaires ; 5 : incision (fluvio-)glaciaire ; 6 : gorge de Monar ; 7 : gorge de Strathconon ; 8 : réseau de vallées dendritique. Les coupes confirment l’identification effectuée par Godard de relief à niveaux multiples autour du bassin, avec une asymétrie marquée illustrée sur la coupe A1. Noter que les largeurs des vallées au niveau de l’isohypse 457 m, à peine 10 km à l’est de la ligne de partage des eaux, sont de 1.5 km pour la Meig et l’Orrin, 2 km pour la Cannich et l’Affric, et 4 km pour la Monar.

Fig. 4 The Monar internal basin, Wester Ross.
Fig. 4 Le bassin intérieur de Monar, Wester Ross.

Fig. 4 – The Monar internal basin, Wester Ross.Fig. 4 – Le bassin intérieur de Monar, Wester Ross.

B: view NNE approximately along line of section A1 from below point 1089 to Maoile Lunndaidh plateau (point 1007), showing the surface supérieure (SS) grading smoothly into the hauts paliers (HP), and more pronounced surface intermédiaire (SI) bench in middle ground.
B : vue vers le NNE à peu près dans l’alignement de la coupe A1, du point 1089 jusqu’au plateau de Maoile Lunndaidh (point 1007). Cette vue montre la surface supérieure se raccordant aux hauts paliers, et un témoin net de la surface intermédiaire au second plan.

36Based on clues provided by figure 4, possible factors in basin development in these headwaters of the east-flowing River Farrar might include any combination of structural factors: the basin could be (i) a vestige of an ancient NE–SW intramontane basin, (ii) behind a more durable band in steep Moinian metasediments, although most of the basin is in uniform psammites except for pelites north of the Ling and Monar gorges, or (iii) behind a barrier either tectonically uplifted or (more feasibly, because this would also explain the anomalous far-eastern position of the Strathfarrar Range) laterally displaced along the Strathconon Fault (a major Caledonian lineament). To these structural factors we may add (iv) the erosional exploitation of any enhanced etch-weathering within the basin by fluvial dissection by the Farrar drainage system behind the barrier created by (i)–(iii); (v) a rejuvenation of the west coast drainage promoting a fluvial breach of the main watershed and a transient capture of part or all of the basin by the short and steep River Ling; and/or (vi) glacial breaching at several points across the main watershed, which enabled a broad ice-stream to flow west (notably through the broad Ling doorway) and glacial reduction of already narrowed or lowered interfluves. Overdeepening of the Monar trough by 50 m could have been achieved by east and/or west-flowing ice. Note that the narrow Monar Gorge is situated in unusually complex topography, and only ~1 km wide (fig. 4, section B1). It is not obviously a glacial breach in origin as are the adjacent gaps and the narrow passes to the west. It may be a pre-glacial incision maintaining the continuity of the Monar-Farrar river, as drainage orientations confirm, perhaps accentuated by glacifluvial action. Erosion surfaces mapped at small scale by Godard and considerably extended from field, map, and air photo evidence suggest a hilly paleic relief, with smooth spurs down to 700 m asl. The sections imply incision of the Monar Gorge into a ridge as young as the surface intermédiaire facets, and elaboration of the Monar Basin at its expense. The floor of the Monar basin is at the 250–300 m asl level as recognised by Godard in the mountain interior for the surface écossaise, but curiously is not mapped as such, whereas extensive areas in the Ling basin to the west and in east-flowing basins further north are.

37It is still not very clear how etch-planation is supposed to operate in the roots of a passive-margin mountain range. Indeed Thomas (1989) treats the etched plain as merely one expression of relief differentiation and elimination by dynamic etch processes when he writes: “it remains a problem to reconcile this long-term trend towards a more differentiated land surface with the claim for both regional and local planation levels”. The processes by which extensive low-relief etch-surfaces are elaborated in the Highlands are difficult to envisage given: (i) long-term tectonic buoyancy continually tending to decouple the terrain from marine base level, with reincisions/rebevellings destroying earlier surfaces and operating across terrain which has had little time for etch-weathering; (ii) sod-forming vegetation cover (evolved in the early Tertiary) and a generally warm, moist climate greatly inhibiting wash processes and thus pediment formation; and, as a corollary, (iii) fluvial export of deep-weathered material being restricted to narrow corridors of incision plus limited zones of significant lowering by solution, leaving wide interfluves of inactive relief across successive phases of uplift.

38Godard et al. (2001) give examples of etch-planation ranging in scale from kilometric alveolate relief in the Massif central to continental on ancient cratons, but the processes capable of eroding extensive surfaces in post-orogenic timescales in locations such as Scotland remain elusive; etching is not invoked by Peulvast (1987) in the Scandes, although Lidmar-Bergström and Näslund (2002) identify it around their fringes and possibly in the lowest level of the paleic relief. With justifiable exasperation, A. Hall (pers. comm., 2006) remarks that “The Scottish Highlands are not a good location in which to study erosion surfaces because glaciation and recent uplift have removed correlative deposits on land. The serious student of long-term landform development should perhaps go elsewhere”. Perhaps in pursuit of suitable analogues for Scotland?

Planation surfaces become paleosurfaces

39When it comes to Les problèmes d’ensemble, one senses that Godard’s heart lies in geological influences on scenery rather than in the planation issue, and that he may have been directed to pursue it by others (possibly his mentor, Guilcher). Yet Godard et al. (2001) celebrate a re-enchantment with the erosion cycle, and the Scottish Highlands are cited for Godard’s “ample and compelling evidence... for the development of step-like erosion surfaces” (p. 62). They might also have noted that his surface supérieure bevels across lithologically-variable and uptilted metasediments, in contrast to the selectively preserved/eroded Cambrian quartzite peaks, thus spanning one of the concluding issues set out by Lageat and Gunnell (2001) in their siliciclastic weathering problem of climate versus geology.

40Within Scotland, erosion surfaces remain rather passé. Sissons (1967) endorsed planation for the new geomorphology, recognising Godard’s map as “by far the most detailed work on erosion surfaces in Scotland”. However, it has never been critically evaluated (figs 3 and 4), and has lain dormant, no doubt because it is unconducive to precise measurement, process verification, and objective proof. The advent of techniques such as Digital Elevation Models and LiDAR imagery ought to assist identification, although the effort of Ringrose and Migon (1997) in a transect across the Central Highlands lacks conviction in the absence of Godardian groundtruthing.

41By contrast, paleosurface studies in Scandinavia are well advanced: interestingly, Lidmar-Bergström and Näslund (2002) describe “characteristic landscape types formed by etching and planation” which vary in their hilliness and mode of evolution in much the same way as Godard failed to distinguish. The tectonics provoking these paleosurfaces remain contentious, with some contributors to Doré et al. (2002) rejecting Godardian soulèvement saccadé after an initial Paleocene uplift, instead interpreting Tertiary base-level changes as climatic/eustatic; elsewhere in the Caledonides, doubt is now even being cast on any major Paleocene uplift event, as against long-persisting post-orogenic buoyancy (Nielsen et al., 2007). Scotland might bear comparable re-evaluation, although its smaller size and lower elevation should make it rather less susceptible to tectonic/isostatic effects (S. Nielsen, pers. comm., 2006).

42Godard’s analysis is, of course, predicated on a substantial and pulsed Tertiary uplift from low relief (Hall, 1991). Even if this is challenged, the terrain patterns which Godard sought to map do exist (fig. 3), and beg explanations which must surely be more generic than site-by-site geological adaptations, tectonic variations, or drainage evolutions. The intervening white spaces between Godard’s surface fragments, including some extensive planar versants (fig. 4A), remind us that it is the totality of the ensemble of slopes that has to be understood, not just the most readily extracted elements.

Theme 2: origins of the paleic relief

43It is now generally recognised that the present main elements of the Highlands are the eroded roots of the Caledonian orogeny (Hall, 1991), but the trajectory is poorly-understood and contentious. Thus perhaps the most challenging of Godard’s surfaces in landscape evolution terms as the ‘paleic relief’ and parent form for all that follows, is his surface supérieure. This is not a new perception (Geikie recognised a summit tableland) but Godard is the first to examine it minutely. Yet he is uncharacteristically deprecatory about it, for although he maps scores of widespread fragments, he considers it would be aléatoire de les raccorder entre eux [300], especially south of the Kyle–Dingwall railway line where they become réduits et plus douteux [Carte VI]. They range in elevation from 750 m to 1150 m asl, with considerable local variations. This surface should repay thorough remapping and testing with new techniques, not least since it is the most likely to have survived glacial modification; a sample area around Monar suggests it could be considerably extended (fig. 4). In his reluctance to comprehend this surface as a whole, and in bracketing it with the multi-storeyed Tertiary planation stages, Godard misses the possibility of tracing an evolution, however exiguous, from the original shaping of the Highlands.

Exhumed erosion surface comparators

44Yet Godard provides a splendid explication of two ancient surfaces now being exhumed east and west of the Moine Thrust respectively, interpreting them as real buried landscapes with significant slopes and corrugations, although he maps them very conservatively as lambeaux (tatters) along their outcrops [carte V]: prédévonienne, which he notes was identified by Bremner (1942); and infratorridonienne, which he accepts has long been known to unspecified géographes (in fact at least as far back as Geikie in 1888), with the classic hilly unconformity exposed on Slioch being sans doute la plus belle d’Écosse [168].

45Godard observes that the basal breccias and conglomerates burying the sub-Torridonian surface fossilisaient une topographie irrégulière sculptée dans le gneiss lewisien [564] without even noticing canyons 150–350 m deep around Stoer (Stewart, 1972; Rider, 2005). Likewise, he recognises that the pre-Devonian surface on which the Old Red Sandstone (ORS) accumulated was hilly, evidencing valleys cut in Moine schists as deep as 300 m in the Inchbae area [566 ] (fig. 5). He is well aware that the ORS is the produit de la destruction des chaînes calédoniennes, but he does not convey its essential difference from the Torridonian sandstone: this was deposited on an ancient planation surface, latterly uplifted and dissected, whereas the ORS comprises “the molasse deposits of the emerging Caledonian mountains” whose extant basal members were variously “alluvial fans at the foot of actively moving fault scarps” and “deposited on a mountainous landscape” (Mykura, 1991). It is curious that Godard seems unable to visualise a diachronous sub-Devonian surface encapsulating a moving moment in the shaping of the Caledonian mountains, as the products of their rapid erosion lapped steadily higher up their still-rising slopes.

Fig. 5 Ben Wyvis and Inchbae, Central Ross-shire. For locations see fig. 1.
Fig. 5 Ben Wyvis et la cuvette d’Inchbae, Ross-shire central (voir fig. 1 pour la localisation).

Fig. 5 – Ben Wyvis and Inchbae, Central Ross-shire. For locations see fig. 1.Fig. 5 – Ben Wyvis et la cuvette d’Inchbae, Ross-shire central (voir fig. 1 pour la localisation).

The Inchbae cuvette or internal basin is not confined to the augen-gneiss outcrop, but englobe three lithologies. Ben Wyvis is the only high massif framed by Old Red Sandstones (ORS) outcrops. The cross-section suggests how they might assist in reconstructing its scale soon after the close of the Caledonian orogeny (geology interpolated from British Geological Survey sections in vicinity). Key to symbols: 1: Old Red Sandstone (on basal unconformity), with M (Middle) and L (Lower; the contact at SE flank is Emsian); 2: breccia and conglomerate; 3: breccia and conglomerate along fringes; 4: sources of conglomerate after Peach et al. (1912), with figures indicating maximum clast dimension in metres; 5: augengneiss (AG) with unroofing domes (IB: Inchbae; CC: Carn Chuineag, occurs north of section); 6: Moinian schist (SCH), with psammite (top) and pelite (bottom); 7: Torridonian and Cambrian pebbles (T+C), occurring only in Middle ORS and in outrcops currently 50 km to the west; 8: preglacial land surface including maximum relief (dashed lines) NE of section (Ben Wyvis range only; 772 may also be a preglacial remnant); 9: Meall a’ Ghrianain outlier (772) and Meall nam Mullach (SCH:AG); 10: faults, thrusts; 11: Caledonide major sinistral strike-slip fault (SC: Strathconon fault; SG: Strathglass fault). The theoretical maximum elevation envelopes apply strength equilibrium slopes of 20 (the lowest residual friction angle generally found in schists, allowing for significant erosion of the orogenic pile towards conditional stability), and 30 (a median figure attainable during the period of rapid upbuilding). The peak friction angle of 40 in schists would theoretically yield a summit of 6800 m above present sea level, but while locally sustainable, syn-orogenic erosion would prevent literal attainment. The notional profile of the Wyvis range is centred above the reconstructed preglacial whaleback mountain, which in turn reflects the greater resistance of the Glenfinnan Group pelites. The high SE face is adopted from Trewin and Thirlwall (2002, fig. 8.14 therein), which indicates high mountains with deeply incised valleys (and) alluvial fans.
La cuvette d’Inchbae n’est pas confinée à l’affleurement de gneiss œillé, et met en jeu trois lithologies différentes. Le massif de Ben Wyvis est le seul qui soit encadré par des affleurements de Vieux grès rouge. La coupe suggère comment ces grès peuvent servir à la reconstruction de l’étendue du massif après la fin de l’orogenèse calédonienne (géologie interpolée des coupes voisines levées par le British Geological Survey). 1 : Vieux grès rouge (sur discordance basale), avec distinction entre étages M (Moyen) et L (Inférieur; le contact au flanc SE est Emsien) ; 2 : brèches et conglomérats ; 3 : brèches et conglomérats sur les bordures ; 4 : sources des conglomérats selon Peach et al. (1912), avec chiffres indiquant la dimension maximale des clastes en mètres ; 5 : gneiss œillé (AG) affleurant en dôme (IB: Inchbae; CC: Carn Chuineag localisé au nord de la coupe) ; 6 : schiste moinien (SCH), avec psammite (demi-caisson du haut) et pélite (demi-caisson du bas) ; 7 : galets Torridoniens et Cambriens (T+C), présents seulement dans le Vieux grès rouge moyen et dans des affleurements actuellement présents 50 km plus à l’ouest ; 8 : surface topographique pré-glaciaire avec enveloppe topographique maximum (lignes tiretées) au NE de la coupe (seul le massif du Ben Wyvis est représenté ; la cote 772 est peut-être un résidu pré-glaciaire ; 9 : buttes de Meall a’ Ghrianain (772) et Meall nam Mullach (SCH:AG) ; 10 : failles, chevauchements ; 11 : failles calédoniennes majeures à jeu décrochant sénestre (SC: faille de Strathconon; SG: faille de Strathglass). Les enveloppes d’altitude maximum théorique de la chaîne calédonienne impliquent des pentes d’équilibre critiques de 20 (plus faible angle de friction résiduelle généralement rencontré dans les schistes, tenant compte de l’érosion considérable du prisme orogénique en équilibre stationnaire) à 30 (valeur médiane réalisable durant la période de construction rapide de l’orogène). Une valeur maximale de 40 sur schistes fournirait un sommet théorique de 6800 m au-dessus du niveau actuel de la mer, mais cette éventualité serait en réalité inatteignable en raison de l’érosion syn-orogénique. Le profil hypothétique de la chaîne de Wyvis est centré sur la montagne pré-glaciaire reconstruite en forme de dos de baleine, qui reflète la forte résistance des métapélites du Groupe de Glenfinnan. La haute façade vers le sud-est est adoptée de Trewin et Thirlwall (2002, leur fig. 8.14), qui décrivent de hautes montagnes avec des vallées profondément incisées et des cônes alluviaux.

46The landscape evolution significance of this sub-Devonian surface, or Caledonian unconformity, is intriguing. By definition the ORS deposits can never have covered the summits or higher ridges (fig. 5), and the subsequent stripping of ORS only reveals the final form of specific lower parts of the mountains at snapshot moments in the orogeny. Thus no trace of the final form of the summit relief at the end of the orogeny can have been preserved. The possibility of continuous sub-aerial evolution from emergent Caledonide mountainscape to present paleic relief appears not to have occurred to Godard or earlier workers.

Evolutionary descent from the sub-Devonian surface to the present summit surface

47It had long been thought that the proto-range had been reduced to low relief, submerged, planated, buried in Mesozoic deposits, and rejuvenated in the early Tertiary as a tabula rasa on which a new drainage system was inscribed. The notion of a complete chalk cover (Linton, 1951) was under attack by George and others as Godard wrote, paving the way for his devastating coup de grâce (see below). Even so, the Godard–Sissons generation still built their accounts from Tertiary foundations, and the shaping of the range remains contentious. On the one hand, N. Trewin (pers. comm., 2006) considers that submergence during the late-Cretaceous eustatic high may have been very extensive; apatite fission-track analyses (AFTA) suggest deep burial to many geologists (A. Hall, pers. comm., 2006), although these results have been challenged; and thick sediment sequences in offshore basins suggest pulses of uplift and erosion, but their association with upland relief elimination is not proven. On the other hand, the paleogeographies in Trewin (2002) indicate substantial Highland land-masses since the Devonian and especially throughout the Cretaceous (Harker, 2002, Figs. 12.4–12.9 therein), a consensus reflected in a wider-audience work on Scottish mountainscapes (Goodenough, 2006). Even if Cretaceous marine transgressions were very extensive, their local planations and thin deposits would only have been superficial interruptions, soon erased, with the underlying hydrography quickly reasserting itself. Tectonic events not fully known to Godard have had considerably greater influence on the shape of the landmass, notably the end-Variscan opening of The Minch, and the Paleogene opening of the Atlantic, with its associated vulcanism briefly burying proximal upland areas. However, the structural controls on the north-western seaboard and the extent of post-rifting uplift and possible tilting remain speculative.

48Bearing in mind that the landward ORS is a terrestrial system of deposits, it is thus arguable that the extant Caledonide metamorphic basement has never been submarinated since its Ordovician/Silurian emergence; and that the present paleic relief is the end-state of a near-continuous process of sub-aerial erosion, albeit of varying modes and paces, from the Devonian until now. Godard’s summit surface fragments suggest evolution from a mountain range of alpine character to a rolling upland, with fluvial encroachments after successive or sustained uplift never eliminating their cores. Deep weathering mantles, and the longevity of the Grampian divide, suggest that this dissected upland may well have become rather stable in general form, if not of course in absolute height and shape. Even in the present plateau country of the eastern Grampians, there are few areas which could be called flat in the peneplain/pediplain sense, with Sugden’s (1968) summit surface having a local amplitude of 150 m. Smooth gulls-wing fluvial valleys unrelated to present local base levels can be found in the upper reaches both here and in the glacially-dissected western Highlands (fig. 4), where tiny pre-Quaternary surface remnants display quite pronounced relief (fig. 2).

49What Godard does not quite do is to make the evolutionary connection between the Devonian relief of the buried mountain footslopes (the exhumed lambeaux) and his surface supérieure, which he relates entirely to Tertiary upwarping, in all probability éogène (= Paleogene or later) [573], although he does concede that since it has no datable deposits on it and bevels no Tertiary Volcanics, this remains open to debate [576]. Godard may have blinkered himself in his anxiety to rebut Bremner’s attempts to trace surviving Devonian surfaces with minimal Tertiary modification [567]. Thus Bremner instances the sharp ridge of Scaraben buried in ORS, which Godard belittles as a special case of resistant quartzite lithology, but might well be a freshly-eroded minor Caledonide crest overwhelmed by deposits from surrounding higher ridges, now outstanding by topographic inversion. Bremner also suggests that the puzzling tract of intermediate relief between the Great Glen and the Western Highlands (the flat belt mentioned above) is an exhumed Devonian surface, which emerges from beneath ORS fringes at The Aird and Meallfuarvonie. It seems not unreasonable to detect a ghost of a mountain foreland in the structure here, but Godard dismisses it because he finds two Tertiary planation surfaces inscribed on it.

50Ben Wyvis provides an exceptionally well-constrained opportunity for reconstruction (fig. 5). Bremner recognises it as a Caledonian mountain ridge separating two basins of extant ORS deposition, Inchbae and Cromarty. Given the alignment of this range parallel to the Moine and Sgurr Beag Thrusts, and further ORS outliers on the same alignment extending NE for 100 km (fig. 1), it is intriguing to envisage here a vestige of the fold-parallel ridges and intramontane valleys typical of alpine ranges. But Godard dismisses the idea that the present steep planar NW slope of Ben Wyvis is literally an exhumed Devonian mountain side on narrow technical grounds, missing the larger point. Yet surely his own lambeaux on either side of Ben Wyvis [Planche V] must scope its original height as an alpine massif with at least 3000 m relief, assuming minimal subsequent tectonic movements (see section on fig. 5). The notional subdivision of the range reflects the present relief, and the tendency of valley spacing in the Highlands and metasedimentary Alps to be around 8 km rather than 15 km. A summit height of around 3300 m (i.e., 1300 m above the present summit) turns out to be broadly compatible with latest estimates inferring average removal of 1.5 km of overburden in the last 300 Ma (A. Hall, pers. comm.). Sources of conglomerate are from Peach et al. (1912) as acknowledged by Godard. They record abundant augen-gneiss in the Strath Rannoch outliers, but none SE of Wyvis. They inferred that the intrusions had been buried in ORS before deposition of extant conglomerates on the SE, but since both flanks are now dated as Lower ORS, a simpler reason would be that the intrusion roofs were lower than the proto-Wyvis crest (as sketched). Remarkably, they found frequent pebbles of Torridonian and Cambrian provenance (nearest present outcrops ~50 km west, beyond the Moine Thrust) but only in the Middle ORS SE of Wyvis, suggesting consequent southeasterly trunk drainage with early incision of major gorges across Caledonide axes, as commonly seen in young orogens. They described the basal unconformity as very uneven with local cliffs. Godard shows [fig. 112] the Strath Rannoch outlier as filling/capping two valleys/interfluves with sub-Devonian relief of 300 m. Clearly this reconstruction would be flawed if significant vertical tectonic displacements had occurred post-ORS deposition, but this seems unlikely. The major Caledonide (NE–SW) fault movements framing this area have been predominantly lateral. Ben Wyvis is anomalously high for the eastern side of the NW Highlands, but this may be not unrelated to the anomalous preservation of the ORS Strath Rannoch outliers adjacent to it; as with the Strathfarrar Range (fig. 4) it could result from ancient lateral displacement along transcurrent faults.

51In Scandinavia the ‘paleic relief’ has been recognised for over a century, with pre-Tertiary pedigree (Gjessing, 1967). Lidmar-Bergström and Näslund (2002) can distinguish a heavily-dissected summit surface in the northern Scandes, developed on a Paleogene tilted uplift, from a stepped sequence in southern Norway where uplift and doming has continued, all with inferred Mesozoic origins. They conclude that “genetically interpreted landforms are important datasets in morphotectonic analyses, complementary to studies of the sedimentary record and thermotectonic evolution of the bedrock”. It is high time to extend similar, comparative investigations to Scotland, in which Godard’s pioneering mapping of summit surface remnants, so cautiously underplayed by him, merits revisit, testing the probability that they are rather more extensive, and the possibility of considerably earlier ancestry.

Theme 3: glacial inefficacity

52After a century of enthusiastic post-Agassiz pursuit of the new paradigm of Ice Age Scotland and its wholesale remodelling by glaciers, Godard (1961) is possibly the first to seriously question their role (in Scotland if not in Scandinavia) : leur efficacité globale a été trop souvent surestimée because glacial action has been applied to a relief already profondément marqué par le dispositif structural [7]. He intuits this at every scale: (i) a roadcut in the supposedly scoured gneiss of NW Sutherland reveals 4.5 m of deeply rotted bedrock [134]; where solid rock is exposed, the ice has “contented itself with polishing it”, although he recognises that the gneiss lacks crush zones and faults to exploit [138]; (ii) even in the mountains, the cirques of Foinaven are found weak by comparison with those of the Lake District [138, here acknowledging Thompson]; (iii) the extreme relief of Torridon is contrasted with that just inland, and attributed to greater preglacial dissection of the coastal mountains, exploited by glaciers where it suits their direction of discharge [183]; (iv) the survival of incised meanders in Strath Oykell is an exemple plus démonstratif de l’efficacité limitée du travail glaciaire [293].

53In the core mountain area of the Western Highlands, under le travail glaciaire [332] he catalogues the evidence for incomplete glacial remodelling of a preglacial valley system, with gentle slopes (10–15° in Garry and Arkaig), lack of truncated spurs or hanging valleys, the raccordement of tributaries, and oversteepening occurring only locally at the slope foot even in the most extreme 1000 m relief at the head of Loch Duich. Here on the west coast les formes typiquement préglaciaires n’ont guère été modifiées par les passages répétés de la glace [356].

54In a masterly summary of les retouches… quaternaires [603, a splendidly dismissive phrase], Godard stresses that although the Highlands exemplify glaciated relief, this does not mean a radical transformation by ice. Even the impact of cirque erosion must not be exaggerated: there are few arêtes resulting from cirques adossés [609]. Glacial troughs are most pronounced where preglacial valleys were already most deeply incised, on the short descent to the West coast. Faults such as Strathconon are more influential than ice outflow direction in shaping glacial troughs. The Great Glen gabarit (template) is glacial, but the valley is Tertiary, with glaciers merely exaggerating plateau vs. valley contrasts [611]. He approves of Tarr’s analogy with Alaska, with glaciers losing their erosive powers when they leave the valleys and spread over lower ground, where preglacial features survive widely. Le Cœur (1994) endorses the predominance of structural and preglacial signatures over Quaternary processes, in the igneous Inner Hebrides at least.

55This iconoclasm has scarcely been noticed, e.g. not by Sissons (1976a), possibly because once again Godard does not illustrate it. It was a necessary corrective at the time, but perhaps overegged. Linton (1959) had grasped the extreme contrasts between west and east in the dissection of a once-uniform upland, which must reflect a significant glacial contribution, while Haynes (1983) demonstrates the limited area of preglacial land surface surviving at higher elevations in most of the Highlands. With the abundant data on offshore glacial deposits now available (Clayton and Shamoon, 1999; Stoker and Bradwell, 2005), it would be interesting to see how Godard might reappraise the total effect of this volume of glacial erosion in reshaping the Highlands landscape. It is also notable that Lageat and Gunnell (2001) contrast Godardian glacial cosmetics in Scotland with Peulvast’s wholesale adaptation to ice in Norway, albeit in a more arctic climate.

56Two contrasting modes of glacial erosion have been invoked in the Highlands. Sugden (1968) recognised selective linear erosion in the eastern Grampian plateaux, while areal scouring is seen in the degraded ridges and knock-and-lochan terrain of the west. It is the latter which Godard is really challenging, whereas the former might be a powerful hidden agent in the western mountains (fig. 6), as Godard never quite spelled out (possibly because he scarcely penetrated to observe the surprising selectivity there). The extent to which gross lowering of the highly-dissected west is attributable to (i) areal glaciation, (ii) intensive selective linear erosion under the thickest ice, and (iii) pre-Quaternary fluvial incursions from a rejuvenated west coast merits investigation with Godard’s rhetorical question about the survival of véritables knicks in mind.

Fig. 6 A case for selective linear erosion by glaciers in the dissected Western Highlands, as suggested by schematic profiles along main watersheds.
Fig. 6 Le cas de l’érosion linéaire sélective par les glaces dans les Hautes Terres de l’ouest, suggérée par les profils schématiques des principales lignes de partage des eaux.

Fig. 6 – A case for selective linear erosion by glaciers in the dissected Western Highlands, as suggested by schematic profiles along main watersheds.Fig. 6 – Le cas de l’érosion linéaire sélective par les glaces dans les Hautes Terres de l’ouest, suggérée par les profils schématiques des principales lignes de partage des eaux.

Profile (a) shows its classic effects in the Eastern Highlands, with simple cirques, troughs and occasional sharply-incised breaches. Profile (b) suggests that the scoured relief of the Western Highlands is merely a surface roughening of essentially similar selective erosion of deeper troughs, many of them breached and cross-breached, but with much of the preglacial topography surviving with increasing intactness at higher levels. 1: preglacial land surface remnants; 2: superficially scoured glacial topography; 3: background relief, including cross-breaches between main valleys (4).
Le profil (a) montre ses effets classiques dans les Hautes Terres de l’est, avec des cirques simples, des auges, et d’occasionnelles brèches profondément incisées. Le profil (b) suggère que le relief récuré des Hautes Terres de l’ouest n’est que la version plus accidentée d’un paysage fondamentalement semblable à (a), avec des entailles d’érosion sélective plus profondes. La plupart des interfluves encadrants sont troués par des brèches de transfluence, mais les survivances de topographies pré-glaciaires demeurent plus intactes vers les niveaux plus élevés du paysage..1 : topographies pré-glaciaires résiduelles ; 2 : topographie glaciaire ayant subi un râclage superficiel ; 3 : topographie d’arrière-plan avec trouées de transfluences entre les vallées (4).

Theme 4: watershed reconstruction and glacial breaching

57Godard’s approach is at its most dated when he embarks on a meticulous, if poorly evidenced, analysis of the réseau hydrographique [105]. He observes that the present main watershed of NW Scotland ne coïncide pas avec la ligne des plus hauts sommets mais qu’elle zigzague de part et d’autre [107]. His Planche II identifies 14 pockets between Cape Wrath and Mull where drainage network shape suggests capture by the short west-flowing rivers, all displacing the divide east by a few miles (fig. 7), but he offers no criteria for their selection.

Fig. 7 The main watershed of the NW Highlands, showing displacements from preglacial positions inferred by Godard (1965) and Jarman (2006).
Fig. 7 La ligne principale de partage des eaux des Hautes Terres du Nord-Ouest, montrant les déplacements des positions pré-glaciaires déduites par Godard (1965) et Jarman (2006).

Fig. 7 – The main watershed of the NW Highlands, showing displacements from preglacial positions inferred by Godard (1965) and Jarman (2006).Fig. 7 – La ligne principale de partage des eaux des Hautes Terres du Nord-Ouest, montrant les déplacements des positions pré-glaciaires déduites par Godard (1965) et Jarman (2006).

Note how the catchment area of the River Ness is almost entirely intercepted by Loch Ness, rendering the fan-delta at Inverness (see fig. 8) patently anomalous. 1: present main watersheds; 2: inferred pre-Quaternary watersheds (Jarman, 2005); 3a: watershed displacements according to Godard and author; 3b: displacements according to author; 3c: displacements according to Godard, doubtful; 4: Loch Linnhe river (Godard, doubtful); 5: steep belt/flat belt (SB/FB, Quoiche line); 6: mountains in flat belt (750–950 m asl); 7: river Ness catchment.
Noter la manière dont le bassin hydrographique de la Ness est presque complètement intercepté par le Loch Ness, rendant de ce fait anormal le fan-delta d’Inverness (fig. 8). 1 : principales lignes de partage des eaux actuelles ; 2 : lignes de partage des eaux pré-quaternaires hypothétiques (Jarman, 2005) ; 3a : déplacement de ligne de partage des eaux selon Godard et l’auteur ; 3b : déplacement selon l’auteur ; 3c : déplacement (discutable) selon Godard ; 4 : Loch Linnhe river (selon Godard, mais discutable) ; 5 : steep belt/flat belt (SB/FB, Quoiche line) ; 6 : reliefs montagneux de la flat belt (750–950 m d’altitude) ; 7 : bassin versant de la rivière Ness.

58Nevertheless, this is the first comprehensive attempt at pre-Quaternary Highland watershed reconstruction, although Dury (1953) had spotted local displacements. Yet once again Godard is conservative as to the scale of landscape change, constraining himself to extant relief by contrast with hazardous interpretations such as Bremner’s, which attributed the wide through valleys of the northern Highlands to an ancestral divide out in The Minch since lost to a parodied catastrophe engloutissant les parties supérieures des bassins [108]. Given his lack of any better explanation, and his later adoption of concepts from Cloos and Fourmarier which envisage the foundering of the Minch and subsequent upwarping of the NW mainland coast [563] (Hall, 1991), it might even be worth revisiting Bremner here.

59Godard acknowledges the role of glacial breaching by regional ice transfluent from the east in effecting some captures, attributing its first recognition to German workers (Louis, 1934; Sölch, 1936) prior to Linton (1949), while overlooking Cadell (1886) around Loch Lomond which was admittedly beyond his study area. Godard makes one unusually bold leap in mapping Loch Shiel as a great fault-exploiting breach in the watershed capturing the Glenfinnan basin, which is preferable to Dury’s (1953) limited diversion (fig. 7); he proposes a half-hearted restitution at the head of Loch Broom which is not adopted by Hall (1991), and an implausible reversal of Loch More in NW Sutherland. However, he often underestimates the scale of breach capture, and overlooks several major possibilities. As a result, Godard’s reconstructed line zigzags even more frenetically between Loch Monar and Beinn Dearg, when Glen Carron, Glen Torridon, and even upper Loch Maree could all reasonably be construed as major breaches of the same ilk as Loch Shiel (fig. 7). Indeed his discussion of Torridon as a dome of radial drainage [183], borrowing from Linton (1957), unduly limits his thinking here, and is at odds with his dismissal of this model in the summation [610].

60Godard’s cautious appraisal of the main mountain watershed gives way to sweeping reconstructions across Sutherland and the half-drowned undulations of Orkney (fig. 7). He has an uncharacteristic blind spot with the geography of the Pentland Firth, which is nowhere discussed. Planche II shows the divide crossing it from near John o’ Groats to South Ronaldsay, up the east side of Scapa Flow and looping across Mainland to the low islands of Eday and Sanday. A more plausible westerly line might be invoked from Dunnet Head across to the hills of Hoy and thence to the hillier islands of Rousay and Westray. Remarkably, Godard is able to see the Westray–Stronsay firth, which is not structural like Scapa Flow, as a glacial lowering of a col [552], a submerged breach in fact, without equally suggesting such a possible origin for the Pentland Firth, as marine charts hint. And at the other end of his study area, Godard inexplicably shows the Sound of Mull as the preglacial route to the sea for his putative Loch Linnhe river, rather than the seaward Great Glen Fault, whereas Sissons (1967) more sensibly has the Sound as a glacial breach (while likewise overlooking the Pentland Firth).

61At the outset, Godard shrewdly questions whether all these breaches are entirely glacial [107], some of them may well capitalise on fluvial incisions from the west coast, dating back to Paleogene rejuvenation if not the Permo-Triassic opening of the Minch. But for Godard et al. (2001) to suggest that such expanding seaward-facing drainage basins were affected by glacial transfluence after their main arteries had breached major divides (p. 202, paraphrased and emphasised) may take this too far. Extreme divide zig-zags associated with breach-captures, whether locally in the Highlands (Hall and Jarman, 2004) or regionally in the Torngat Mts (tracked by the Quebec–Labrador boundary) must surely have regional ice transfluence as the main driver. Godard’s synthesis rather avoids the role of glacial transfluence and breaching, and this seems to be a surprising lacuna in the French school generally, given its interest in glaciated passive margins.

Theme 5: ice limits

62A remarkable feature of Godard’s view of geomorphology is his almost total disdain for glacial deposits. This aligns him with most geologists in Scotland who until recently have taken little interest in superficial cover, although for them it is a concealing irritant whereas for him it is simply a distraction from the solid relief. He is not unaware of the efforts of Donner or Charlesworth in identifying Perth or Highland Readvances [618], and he alludes to the earliest work of Sissons on meltwater channels and raised beaches, but he feels no compulsion to enter the lists. Indeed it is rare to find any mention of a glacial epoch, and then only in a dismissive context: la “Scottish Readvance” qui n’est pourtant qu’un stade tardif du Würm [604].

63This disdain is refreshing, given the energy since devoted to mapping ice limits and retreat patterns and shorelines, notably those of the Loch Lomond Stadial (Younger Dryas) by Sissons and his school. Taking the Plio-Pleistocene glacial era as a whole, the Loch Lomond Stadial is in fact rather insignificant in its erosive effects, mainly redistributing deposits already in the system. Indeed, Godard goes on to dismiss the évolution postglaciaire of the Highlands as tout cela ne représente qu’un aménagement de détail [357], an observation worth pondering when setting research priorities.

64Godard becomes briefly animated by glacial limits at just one point, when he identifies 15 nunataks in Sutherland, the Inner and Outer Hebrides, and Hoy, from the presence of blockfields, which he argues (after Dahl in Norway) cannot have developed postglacially [604]. From their peripheral distribution he generates a fairly tentative and incomplete map of ice-cap contours [fig. 177]; he observes that its rapid decline northwards is consistent with the lesser glacio-isostatic recovery observed there.

65This may be the first attempt to visualise a main ice-cap configuration for the Scottish mainland, Geikie (1873, 1878) having identified a trimline on the Outer Hebrides; it was evidently overlooked by Sissons (1967; 1976a) and Boulton et al. (1977), who envisaged total submersion by ice. Ballantyne et al. (1998) impressively map a consistent trimline pattern across the northern Highlands and Inner Hebrides by cosmogenic nuclide dating. They acknowledge Godard’s conceptual achievement, but dismiss his mapping as erroneous. In fact, Godard’s shape is essentially that of Ballantyne et al., but ~100 m higher. This is not a grave error, and Ballantyne et al. are a little uncharitable in faulting a pioneering insight which occupies a mere two pages and draws on observations from a small sample of summits visited not with this prime aim in mind. Ballantyne et al. also confine their interpretation to the last ice sheet whereas Godard assigns his configuration simply to the maximum glaciaire, which embraces the whole epoch. Trimlines have moved up and down over the various glacials, and Godard is simply looking at actual summits, which appear never to have been affected by active ice. In fact, both are probably observing the upper limit of obvious glacial erosion, rather than ice sheet upper limits (A. Hall, pers. comm., 2006).

66A commendable ability to see the Pleistocene epoch as a whole pervades Godard’s work. Thus he takes Linton’s (1959) observation that cirque floor levels rise steadily from west to east, and analyses two transects to identify no less than five generations of cirque development [fig. 179]. Perhaps wisely, he then restricts his interpretation to older and younger cirques, following an observation by Louis (1934) in the Loch Maree area [Planche VII]. This prefigures work on old cirques in Scotland (Sugden, 1970) and Sweden (Holmlund, 1991), and on palimpsest landscapes generally (Kleman, 1992).

Some blind spots: the River Ness fan and rock slope failure

67It is instructive to learn from blind spots such as the Pentland Firth in an otherwise outstanding eye for terrain. One prominent example that long escaped notice is the large deltaic fan at the mouth of the River Ness, which has facilitated the growth of Inverness as a regional capital, and the Kessock Bridge across the Moray–Beauly Firth narrows (fig. 8).

Fig. 8 The anomalous large ‘fan-delta’ at the mouth of the 7 km-long River Ness is attributed to the Glen Roy jökulhlaup.
Fig. 8 Le fan-delta anormalement vaste au débouché de la Ness (7 km de long), attribué à la jökulhlaup du Glen Roy.

Fig. 8 – The anomalous large ‘fan-delta’ at the mouth of the 7 km-long River Ness is attributed to the Glen Roy jökulhlaup.Fig. 8 – Le fan-delta anormalement vaste au débouché de la Ness (7 km de long), attribué à la jökulhlaup du Glen Roy.

It creates the site for the city of Inverness, and narrows the Moray-Beauly Firth sufficiently to permit its bridging at Kessock. The deltaic form is defined by the Caledonian Canal (left), River Ness (centre) and a former cliffline (centre right), with wooded islands of Quaternary deposits surviving within the paleo-flood channel. View looking NE. Photograph by kind permission of The Highlands Council.
Ce fan-delta a déterminé le site de la ville d’Inverness, et suffisamment rétrécit le Moray-Beauly Firth pour avoir permis la construction du pont de Kessock. La forme deltaïque est délimitée par le Caledonian Canal (à gauche), la rivière Ness (au centre) et une ancienne falaise (au centre droit), avec des îlots boisés constitués de dépôts quaternaires qui ont survécu dans le paléochenal d’inondation. Vue vers le nord-est. Cliché reproduit avec l’aimable autorisation du Highlands Council.

68British rivers invariably indent the coastline, yet this unique protrusion is on Britain’s shortest effective major river, only 10 km long from the foot of Loch Ness, the depths of which must have trapped all the Holocene sediment from its large catchment (fig. 7). This double anomaly passed unpondered by geomorphologists until boreholes for the Bridge enabled Peacock and thence Sissons (1981) to adduce a catastrophic flood (jökulhlaup) from the Glen Roy proglacial lake overtopping the foot of Loch Ness and remobilising Quaternary deposits in the valley. Godard must often have travelled through Inverness, and describes quite minor glacifluvial features on these shores; Agassiz (1841) had verified the Glen Roy parallel roads.

69A more surprising blind spot is with rock slope failure (RSF). Godard recognises the extensive RSF activity on the cliffs of Skye, Eigg, Mull, and Morvern, but associates it exclusively with Tertiary volcanic lithology [629], while finding little to say about the process or its significance other than attributing it to decompression after deglaciation. But he does not perceive the 200 or more RSFs, which occur all over the mainland part of his area on Precambrian schists and most other lithologies, despite some being very large (reaching 3 km2 with 8 m-high antiscarps on Beinn Fhada) and some being conspicuous (Beinn Alligin; slopes of Glen Shiel). RSF in all its manifestations had been recognised in the Alps (Heim, 1932) if not yet published for NW Scotland, although G. Johnstone of the British Geological Survey was recording them in the Western Highlands in the 1960s, and Bailey and Maufe (1916) had described them as endemic in the Ben Nevis area. Had he been aware of it as an upland phenomenon, Godard would doubtless have been quick to appreciate the significance of RSF as a contributor to gross erosion over repeated glacial-paraglacial cycles, as well as its direct influence on mountain shaping (Jarman, 2002; 2006).

70As it is, Godard makes a delightful error in misinterpreting the headscarp and slip trench of the Ben Hee RSF as a bourrelet morainique laissé par un petit glacier perché, tardiglaciaire [Photo 17]. Unfortunately he cites this as his best example for the extraordinary freshness of fragile forms of accumulation at high levels [603]; Haynes (1977) rectified this detail without extending her critique to the rest of his œuvre (fig. 9; Jarman and Lukas, 2007).

Fig. 9 The Ben Hee paraglacial rock slope failure (RSF).
Fig. 9 L’écroulement paraglaciaire du versant rocheux de Ben Hee.

Fig. 9 – The Ben Hee paraglacial rock slope failure (RSF).Fig. 9 – L’écroulement paraglaciaire du versant rocheux de Ben Hee.

View across upper part from the NE, with the 5–15 m source scarp and trench (right centre, continuing up to skyline above snowpatch) misinterpreted by Godard as a perched moraine at 800 m asl. This is one of the largest RSFs in Scotland within a cirque, affecting 0.4 km2. Photograph D. Jarman.
Vue sur la partie supérieure depuis le NE, montrant l’escarpement de la couronne d’écroulement d’une hauteur de 5 à 15 m ainsi que la gouttière (au centre droit, continuant jusqu’à la ligne d’horizon au-dessus de la plaque de neige), interprété par erreur par Godard comme une moraine perchée à 800 m d’altitude. Il s’agit d’un des plus grands éboulements d’Écosse, ayant eu lieu à l’intérieur d’un cirque, qui affecte une superficie de 0,4 km2. Cliché D. Jarman.

71More seriously, he misattributes gully erosion in Strath Croe to human activity [335], failing to spot the bulging landslip toe of Sgurr nan Airgid (fig. 10); and he alludes to the gorge in Glen Shiel [335, 613] without appreciating the association of breaching, deepening, and narrowing with the large (1.25 km2) and fairly prominent RSF of Sgurr nan Ciste Duibhe (Fenton, 1991; Jarman, 2003, in press).

Fig. 10 The Sgurr nan Airgid RSF, Kintail, with its prominent slip bulge into Strath Croe.
Fig. 10 Le glissement de Sgurr nan Airgid, Kintail, avec le bombement proéminent de la masse déplacée vers Strath Croe.

Fig. 10 – The Sgurr nan Airgid RSF, Kintail, with its prominent slip bulge into Strath Croe.Fig. 10 – Le glissement de Sgurr nan Airgid, Kintail, avec le bombement proéminent de la masse déplacée vers Strath Croe.

View from the SE. At 1.5 km2 it is one of the six largest RSFs in the mainland Highlands. The failure splits the skyline ridge at 600–800 m asl, and descends almost to sea level. A slightly-deflected natural stream course down the right-hand side undercuts the steep and uncohesive toe, promoting extensive gully erosion misconstrued by Godard as anthropogenic. Photograph: D. Jarman.
Vue du sud-est. Avec une étendue de 1,5 km2, il s’agit d’un des six plus grands glissements rocheux des Hautes Terres d’Écosse continentale. La masse glissée interrompt la crête sur la ligne d’horizon à 600–800 m d’altitude, et descend presque au niveau de la mer. Le cours d’un ruisseau se trouve légèrement dévié sur le côté droit et sape le lobe escarpé taillé dans le matériau peu cohésif de la masse glissée. Ceci provoque une érosion ravinante que Godard avait interprétée par erreur comme étant d’origine anthropique. Cliché D. Jarman.

Geomorphological combat

Godard and the British geomorphological establishment

72Godard delights in taking on the British geomorphological establishment and in spearing any weaknesses mercilessly, an entertaining sport, but with risks. Thus he contrasts his own cautious mapping of sub-Devonian surface traces with l’ébauche globale du relief extrapolated à la manière de Bremner [569]. He taunts Bremner with three grave objections, including monadnocks carved in the ORS, which should not exist above an exhumed pre-Devonian surface, and, circonstance aggravante, have similar forms to those cut in the basement rocks [567]. He admits in introducing his problèmes d’ensemble to an unresolved one: how do we identify the respective roles of exhumed topographies and Tertiary planations in the present relief? He ridicules some attempts as assez fantaisistes et bien éloignées des réalités [563]; yet while minimising Bremner’s predevonian surface in favour of his Tertiary planations, he is happy to extend his niveau pliocène over large swathes of knock-and-lochan terrain where in effect it is exhuming his own pretorridonian landscape.

73In similar quixotic vein, he tilts at Wilson’s ambitious notion of an ancient watershed extending from Lewis to the Faeroes, with its beheaded river valley remnants crossing Orkney [laissons à l’auteur la responsabilité de ses affirmations, 552 – sic!] yet his own wayward alignment across the archipelago (above; fig. 7) might equally be described as assez fantaisiste. Indeed, Godard reconstructs entire drainage networks extending well out onto the Continental Shelf [Planche II], linking up submarine basins which may be tectonic in origin, or carved by major ice streams (Stoker and Bradwell, 2005). The lack of field evidence or solid argument for his hydrographic reconstructions takes us back into a more primitive era of armchair physical geography.

74But it is when he comes to David Linton that he dons the mantle of giant-killer, most notably in the affair of la surface infracénomanienne [570]. Godard is rightly sceptical of the notion of a continuous chalk cover over the Highlands, which Linton (1951) and many others advocated to explain the superimposed easterly drainage pattern, and which even Sissons (1967) reluctantly endorses. He admits he cannot refute it, but paleogeography hardly pleads in its favour. His destruction of the Lintonian hypothesis deserves to be celebrated for its ruthless logic. It unfolds as follows: if the sub-Cretaceous base was irregular, then we must renounce the idea that today’s very smooth high level elements are fragments of a great initial surface of uplift. So this is probably why Linton does regard the Cairngorm and Grampian plateau fragments as traces of a sub-cenomanian surface très regulière, bombée asymétriquement durant le Tertiaire. But if the basement surface is very regular, Linton does not need to invoke another very regular chalk surface on top of it. This is un luxe couteux et inutile in Godard’s own raised eyebrows, cheekily prefaced nous sommes tentés de dire, because elle ajoute à une première hypothèse une seconde tout aussi invérifiable. We might also ask if the period between the upper Jurassic and the upper Cretaceous was long enough to inscribe on the basement as perfect an erosion surface as Linton wishes: Godard suggests we need the whole of the Cretaceous and the Eocene, with (semi-)arid climate periods, to achieve this. Moreover, Linton argues for complete chalk cover from thin deposits followed for long distances (Ireland-Hebrides): C’est allez un peu plus vite en besogne semble-t-il, an over-hasty interpolation. Une telle assertion demande à être confrontée avec les faits. Swingeing criticism from an upstart for a doyen. And Godard cannot resist a final stab: le brillant mais fragile échafaudage (scaffolding) imaginé par Linton runs into too many structural and stratigraphical difficulties, and the grand name of L.C. King is deployed to underline this [572].

75If Linton was aware of these attacks, he does not seem to have been sufficiently troubled to respond, and they have passed unremarked subsequently by even such pugnacious British workers as Sissons, as have Godard’s occasional lapses in applying the same rigorous logic to his own constructs. It would also have been helpful had he made it clearer when ideas were his own or where he was benefiting from previous workers; in places (for example in his elucidation of a sub-Torridonian surface) one gains the impression that the NW Highlands were previously unexplored, while to encounter a pellucid appreciation of his three main surfaces, and of the terrain anomaly manifesting as his Ullapool–Dornoch géoflexure transversale, in Peach et al. (1912) brings a distinct frisson of déjà vu.

Rapp and Godard: contrasts in reputation building

76By way of comparison, another major thesis published in the same era, also after a decade of fieldwork, is still widely cited as a landmark in studying erosional processes in a northern mountain environment. Rapp (1960) pioneered process quantification and might be judged far more influential internationally than Godard’s thesis, yet it dealt almost exclusively with a single, atypical side valley in northern Sweden, and its results have never been replicated. Indeed one of its findings, which is an inferred rate of scarp retreat during Holocene times, has been nullified by reattribution of most of the valley-floor giant boulder deposit to a single RSF source at the head (Jarman, 2002). The influence of Rapp’s methodologically-seminal thesis has arguably been assisted (in Darwinian terms) by his crafting a very readable, easily assimilated magnum opus, by his politesse in recognising all antecedents and avoiding combative language, by being anchored within the Swedish establishment, and by being published in English. By contrast, Godard failed to ensure publication in an accessibly condensed form in English, and to our eyes at least his themes disappeared into the impenetrable thickets of French geomorphology. Where “Godard (1965)” is cited today, it is more out of bibliographic diligence than because of what he actually has to say, merely registering that he once worked in NW Scotland. Rapp became a highly-successful, widely-known figure in the anglophone as well as the continental geo-community (and a good friend of Godard), publishing primarily in English, whereas Godard confined his managerial activities to France: the sole international congress featured in his CV is Paris 1984, while of his entire published œuvre of 86 items, only six are in English, of which only three are significant papers in translation or important contributions to edited volumes (Godard, 2006).

Concluding evaluation: Godard’s achievements in mountain landscape evolution

Summary of key insights and ideas of present relevance

77Godard (2006) describes himself today as a physical geographer (indeed he only mentions ‘geomorphology’ post-1965 in respect of crystalline basements), and as a generalist, concluding his career review with a plea for convergence over divergence in research, which should be heard in Britain too. In fact Godard is an exceptional structural geomorphologist and climatic geologist, and a great synthesiser. However silent he may have become on the significance of his original researches, he acknowledges his grounding in Scotland’s laboratory of contrastes morphostructuraux... marquées par une longue histoire paléoclimatique (2006).

78This reappraisal has focused on his researches into the evolution of the NW Highlands as a mountain landscape, neglecting his even more extensive work around the coasts and in the archipelagoes. In the uplands, his insights, ideas, and achievements of lasting value and contemporary relevance include: (i) a holistic approach to landscape evolution, firmly grounded in geology, but not inhibited by over-literal rock-strength preconceptions; aware of climate, hydrology, and process; but interested primarily in outcomes and the synthesis of contributory factors; (ii) his remarkable powers of geomorphological observation and interpretation, both in fine detail and over a broad canvas. Many of his worked examples remain almost unknown, and would benefit from exhumation when a new ‘Scenery of Scotland’ to succeed Sissons (1967) is written; (iii) a clear eye for the actual, often localised incidence of glacial erosion. Here he was and still is something of a lone voice. His systematic cutting down to size of the considerable but not wholesale effects of glaciation merits re-evaluation, in the light of more recent thinking on warm- and cold-based ice; (iv) a disdain for the relatively trivial landshaping role of glacial deposits and glacifluvial/paraglacial/Holocene processes. Their study, both spatially and quantitatively, has dominated Scottish geomorphology since the 1960s, to the neglect of the Godardian approach, (v) the first recognition of nunataks in the NW Highlands as potential indicators of the maximum extent and shape of former icecaps; (vi) his astute discernment of glacial features of different ages (cirques, valleys, breaches) building a picture of glaciation as a progressive and fluctuating process, rather than the conventional image of a single if interrupted event, in which the last glaciation stands as a proxy for all that went before. Here he anticipates by three decades work in Sweden on palimpsest landscapes; (vii) the most detailed and systematic attempt at reconstruction of a preglacial main watershed in the Highlands to date, recognising its consistent eastward displacement by some combination of glacial breaching and preglacial fluvial incision; (viii) the most meticulous elaboration of ancient landscapes revealed by exhumation across each of the major unconformities, and the fullest recognition of the extent to which they influence the present relief. He was also one of the first to challenge the orthodoxy of Mesozoic submergence and planation, and the Tertiary emergence of a uniform chalk surface on which the proto-drainage was held to be inscribed and become superimposed. (ix) His championing of the widespread survival of summit elements of considerable antiquity, not just in flat residuals, but in smooth yet sometimes quite steep hillforms, including inselbergs, monadnocks, and ramparts of varying relationship to geology and structure. Although he does not develop an integrated interpretation of these preglacial upland surface remnants, including their possible evolutionary descent from post-orogenic relief, he is clear that they are far from a Davisian peneplain let alone a cratonic ultiplain; (x) the fullest flowering in Scotland if not Britain of the erosion surface school of landscape interpretation; coherent, yet cautiously constrained by real observations. He identifies families of surface facets which might plausibly relate to former base levels (if perhaps as much local as regional) in a real landscape of complex history. He factors in geological controls in relief differentiation, although he pays less attention to slope development. He paves the way for etch-planation theory, which has yet to be applied in the western Highlands.

A nexus of issues for landscape evolution

79The most contentious and intriguing issues emerging from this review are in the field of long-term landscape evolution, which is finally returning to favour in Britain. They have only been touched upon in this review, and are drawn together here as an agenda for the integrated research espoused by Godard: (i) etch-planation: how it is supposed to work in complex, mid-latitude, passive margin, orogen-root crystalline basement terrain such as Scotland; (ii) multi-storeyed relief: the extent to which erosion surface fragments represent pulsed marine base-level changes, or relate to more local controls, or have evolved separately or coevally; (iii) geologically-controlled versus bevelled relief, and implications for the siliciclastic weathering problem; (iv) early Tertiary uplift: how and indeed whether a major Paleocene upwarping, with or without tilting, occurred in the Highlands; (v) Mesozoic submergence: the extent and influence of sediment cover and its subsequent removal, reassessing AFTA and offshore deposit indications; (vi) the present summit surface (paleic relief) as a direct descendant from the Caledonian unconformity; (vii) long-term drainage evolution and divide migration, including influence of tectonic events; (viii) present disposition, dissection, and absolute elevation of high ground relative contribution of Cenozoic (fluvial) and Quaternary (glacial) erosion including breaching of divides; (ix) effects of long-term isostatic buoyancy and incision in driving relief accentuation.

80It would be especially interesting to compare and contrast Scotland with other Caledonide ranges, notably the Scandes, where recent work in geophysics, offshore data, and terrain analysis has yielded significant insights into their landscape evolution, with the possibility of a paradigm shift if reappraisals of the tectonic driving factors prove valid (Nielsen et al., 2007).

81To conclude: it is high time to revisit the Highlands of Scotland as a microcosm of multi-storeyed and glaciated mid-latitude relief, harnessing the still-tangential concerns of British and French geomorphology to interpret the interactions of shifting climates and tectonics, and armed with the pioneering observations, insights and approaches of Alain Godard.

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Bibliographie

Agassiz L. (1841) – On glaciers, and the evidence of their having once existed in Scotland, Ireland, and England. Proceedings of the Geological Society, London, 3, 327-332.

André M.-F. (1993) Les Versants du Spitsberg. Presses Universitaires, Nancy, 361 p.

Bailey E.B., Maufe H.B. (1916) – Geology of Ben Nevis and Glencoe. Memoirs of the Geological Survey, Scotland, Edinburgh, 247 p.

Ballantyne C.K. (2007) Trotternish. In Cooper R. (Ed.) Mass Movement in Great Britain. Geological Conservation Review Series, 33, Joint Nature Conservation Committee, Peterborough (in press)

Ballantyne C.K., McCarroll D., Nesje A., Dahl S.O., Stone J.O. (1998) The last ice sheet in NW Scotland: reconstruction and implications. Quaternary Science Reviews, 17, 1149-1184.

Bishop P., Hoey T.B., Jansen J.D., Artza I.L. (2005) Knickpoint recession rates and catchment areas – the case of uplifted rivers in Eastern Scotland. Earth Surface Processes and Landforms, 30, 767-778.

Boulton G.S., Jones A.S., Clayton K.M., Kenning M.J. (1977) A British ice-sheet model and patterns of glacial erosion and deposition in Britain. In Shotton F.W. (Ed.) British Quaternary Studies, recent advances. Clarendon, Oxford, 231-246.

Bremner A. (1942) The origin of the Scottish river system – Part III. Scottish Geographical Magazine 58, 99-103.

Cadell H.M. (1886) The Dumbartonshire Highlands. Scottish Geographical Magazine 2, 337-347.

Charlesworth J.K. (1957) The Quaternary Era (2 vols.). Edward Arnold, London, 3200 p.

Clayton K.M., Shamoon N. (1999) A new approach to the relief of Great Britain III. Derivation of the contribution of neotectonic movements and exceptional regional denudation to the present relief. Geomorphology 27, 173-189.

Doré A.G., Cartwright J.A., Stoker M.S., Turner J.P., White N. (Eds.) (2002) Exhumation of the North Atlantic Margin: Timing, mechanisms, and implications for petroleum exploration. Geological Society of London, Special Publication 196, 498 p.

Dury G.H. (1953) A glacial breach in the north-western highlands. Scottish Geographical Magazine 69, 106-17.

Fenton C.H. (1991) Neotectonics and palaeoseismicity in NW Scotland. Unpublished PhD thesis. University of Glasgow, 403 p.

Geikie J. (1873, 1878) On the glacial phenomena of the Long Island or Outer Hebrides. Quarterly Journal of the Geological Society of London 29,532-545 and 34,819-870.

Gillen C. (2003) Geology and landscapes of Scotland. Terra, Harpenden, 245 p.

Gjessing J. (1967) Norway’s paleic surface. Norsk Geografisk Tidsskrift, 21, 69-132.

Godard A. (1957) La surface prétorridonienne en Écosse. Revue de Géographie Alpine, 45, 135-153.

Godard A. (1961) L'efficacité de l'érosion glaciaire en Écosse du Nord. Revue de Géomorphologie Dynamique, 12, 32-42.

Godard A. (1965) Recherches de Géomorphologie en Écosse du Nord-Ouest. Université de Strasbourg, Publications de la Faculté des Lettres, Fondation Baulig, 702 p.

Godard A. (2006) Les jalons d’un parcours teinté d’éclectisme. In André M-F., Étienne S., Lageat Y., Le Cœur C., Mercier D.: From continent to catchment. Theories and practices in Physical Geography. A tribute to Professor Alain Godard. Université Blaise-Pascal, Clermont-Ferrand, 9-15.

Godard A., Lagasquie J-J., Lageat Y. (eds.) (1994) Les régions de socle, apports d’une école géomorphologique française. Université Blaise-Pascal, Clermont-Ferrand, 324 p.

Godard A., Lagasquie J-J., Lageat Y. (2001) Basement Regions. Edited and translated by Y. Gunnell. Springer, Berlin, 330 p.

Goodenough, K. (2006) Geological foundations. In Kempe N. and Wrightham M. (Eds.) Hostile Habitats – Scotland’s mountain environment. Scottish Mountaineering Trust, 256 p.

Gordon J.E., Sutherland D.G. (eds.) (1993) Quaternary of Scotland. Geological Conservation Review Series, 6. Chapman and Hall, London, 695 p.

Hall A.M. (1991) – Pre-Quaternary landscape evolution in the Scottish Highlands. Transactions of the Royal Society of Edinburgh: Earth Sciences, 82, 1-26.

Hall A.M., Bishop P. (2002) – Scotland’s denudational history: an integrated view of erosion and sedimentation at an uplifted passive margin. In Doré A.G., Cartwright J.A., Stoker M.S., Turner J.P. and White N. (Eds.) Exhumation of the North Atlantic Margin: Timing, mechanisms, and implications for petroleum exploration. Geological Society of London, Special Publication, 196, 271-290.

Hall A.M., Jarman D. (2004) – Quaternary landscape evolution – plateau dissection by glacial breaching. In Lukas S., Merritt J.W. and Mitchell W. (Eds.) Quaternary of the Central Grampian Highlands – Field Guide. Quaternary Research Association. London, 26-40.

Harker S. (2002) – Cretaceous. In Trewin N.H. (Ed.) The Geology of Scotland (4th Ed.). The Geological Society, London, 351-360.

Haynes V.M. (1977) Landslip associated with glacier ice. Scottish Journal of Geology 13, 337-338.

Haynes V.M. (1983) Scotland’s landforms. In Clapperton C.M. (Ed.) Scotland: a new study. David and Charles, Newton Abbot, 28-63.

Heim A. (1932) Bergsturz und Menschenleben. Fretz und Wasmuth, Zurich, 218 p.

Holmlund P. (1991) Cirques at low levels need not have been cut by small glaciers. Geografiska Annaler 73A, 9-16.

Jarman D. (2002) Rock slope failure and landscape evolution in the Caledonian Mountains, as exemplified in the Abisko area, northern Sweden. Geografiska Annaler 84A, 213-224.

Jarman D. (2003) The Glen Shiel rock slope failure cluster. In Tipping R. (Ed.) Quaternary of Glen Affric and Kintail - Field Guide. Quaternary Research Association, London, 165-184.

Jarman D. (2006) Large rock slope failures in the Scottish Highlands: characterisation, causes and spatial distribution. Engineering Geology 83, 161-182.

Jarman D. (2007) Sgurr na Ciste Duibhe. In Cooper R. (Ed.) Mass Movement in Great Britain. Geological Conservation Review, 33, Joint Nature Conservation Committee, Peterborough (in press).

Jarman D., Lukas S. (2007) Ben Hee. In Cooper R. (ed.) Mass Movement in Great Britain. Geological Conservation Review, Vol. 33, Joint Nature Conservation Committee, Peterborough (in press).

Kleman J. (1992) The palimpsest glacial landscape in northwestern Sweden: Late Weichselian deglaciation landforms and traces of older west-centred ice sheet. Geografiska Annaler 74A, 305-325

Lageat Y., Gunnell Y. (2001) Structural predesign and scaling factors in geomorphology: lessons from the study of basement terrains. In Godard A., Lagasquie J-J. and Lageat Y. (Eds.) Basement Regions. Springer, Berlin, 259-272.

Le Cœur C. (1988) Late Tertiary warping and erosion in western Scotland. Geografiska Annaler 70A, 361-8.

Le Cœur C. (1994) Évolution géomorphologique et échelles d'analyse: l'exemple des Hébrides internes (Écosse). Thèse d'Etat de l’université Panthéon-Sorbonne (Paris 1), 757 p.

Lidmar-Bergström K., Näslund J.O. (2002) Landforms and uplift in Scandinavia. In Doré A.G. et al. (Eds.) Exhumation of the North Atlantic Margin: Timing, mechanisms, and implications for petroleum exploration. Geological Society of London, Special Publication, 196, 103-116.

Linton D.L. (1949) – Watershed breaching by ice in Scotland. Transactions of the Institute of British Geographers 15, 1-16.

Linton D.L. (1951) – Problems of Scottish scenery. Scottish Geographical Magazine 67, 65-85.

Linton D.L. (1957) – Radiating valleys in glaciated lands. Tijdschrift van het Koninklijk Nederlandsch Aaardrijkskundig Genootschap (Amsterdam), 74, 297-312.

Linton, D.L. (1959) – Morphological contrasts between eastern and western Scotland. In Miller R. and Watson J.W. (Eds.) Geographical essays in memory of Alan G. Ogilvie, Nelson, Edinburgh, 16-45.

Louis H. (1934) – Glazialmorphologische Studien in Gebirge Grossbritannien. Berlin Geographische Arbeite, Heft 6, 39 p.

Mykura W. (1991) Old Red Sandstone. In Craig G.Y. (ed.) Geology of Scotland (3rd ed.). The Geological Society, London, 297-345.

Nielsen S.B. and the CENMOVE Working Group (2007) Protracted erosion and climate change create an illusion of Cenozoic uplift for the Scandinavian Caledonides. Geophysical Research, Abstracts, vol. 9, 06270, European Geophysical Union. www.cosis.net/abstracts

Peach B., Gunn W., Clough C.T., Hinxman L.W., Crampton C.D., Anderson E.M. (1912) The Geology of Ben Wyvis, Carn Chuinneag, Inchbae, and the surrounding country (Explanation of Sheet 93). Memoirs of the Geological Survey, Scotland, Edinburgh.

Peulvast J.P. (1987) Surfaces d’aplanissement étagées dans les Scandes: principes et implications de l’étude des paléosurfaces dans une montagne de haute latitude. Revue de Géomorphologie Dynamique, 36, 1-83.

Rapp A. (1960) Recent development of mountain slopes in Kärkevagge and surroundings, northern Scandinavia. Geografiska Annaler 42, 71-200.

Ringrose P.S., Migon P. (1997) Analysis of digital elevation data for the Scottish Highlands and recognition of pre-Quaternary elevated surfaces. In Widdowson M. (ed.) Palaeosurfaces: recognition, reconstruction, and palaeoenvironmental interpretation. Geological Society of London, Special Publication, 120, 25-35.

Rider M. (2005) Hutton’s arse. Rider-French Consulting, Rogart, Sutherland, 241 p.

Rudberg S. (1992) Multiple glaciation in Scandinavia – seen in gross morphology or not? Geografiska Annaler 74A, 231-243.

Sissons J.B. (1967) The evolution of Scotland’s scenery. Oliver and Boyd, Edinburgh, 243 p.

Sissons J.B. (1976a) Scotland. The Geomorphology of the British Isles. General Editors E.H. Brown and K.M. Clayton. Methuen, London, 150 p.

Sissons J.B. (1976b) A remarkable protalus rampart complex in Wester Ross. Scottish Geographical Magazine 92, 182-190.

Sissons J.B. (1981) Lateglacial marine erosion and a jökulhlaup deposit in the Beauly Firth. Scottish Journal of Geology 17, 7-19.

Sölch J. (1936) Geomorphologische probleme des schottische Höchlands. Mitteilungen der Geographischen Gesellschaft Wien, 79, 31-51.

Stewart A.D. (1972) Pre-Cambrian landscapes in northwest Scotland. Geological Journal 8, 111-124.

Sugden D.E. (1968) The selectivity of glacial erosion in the Cairngorm Mountains, Scotland. Transactions of the Institute of British Geographers 45, 79-92.

Sugden D.E. (1970) Landforms of deglaciation in the Cairngorm Mountains. Transactions of the Institute of British Geographers 51, 201-219.

Stoker M., Bradwell T. (2005) The Minch paleo-ice stream, NW sector of the British-Irish ice sheet. Journal of the Geological Society, London 163, 425-428.

Thomas, M. F. (1989) The role of etch processes in landform development. Zeitschrift für Geomorphologie, 33, 129-142, 257-274.

Trewin N.H. (Ed.) (2002) The Geology of Scotland (4th Edition). The Geological Society, London, 550 p.

Trewin N.H., Rollin K.E. (2002) Geological history and structure of Scotland. In Trewin N.H. (Ed.) The Geology of Scotland (4th Ed.). The Geological Society, London, 1-25.

Trewin N.H., Thirlwall M.F. (2002) The Old Red Sandstone. In Trewin N.H. (Ed.) The Geology of Scotland (4th Edition). The Geological Society, London, 213-249.

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Annexe

Version française abrégée

La thèse d’Alain Godard, publiée en 1965, est peut-être la tentative la plus monumentale jamais réalisée de produire en solitaire le tableau géomorphologique d’une vaste région des Îles britanniques (fig. 1). Elle est fondée sur des travaux de terrain et des observations de grande envergure, et elle aboutit à une ample synthèse de facteurs aussi diversifiés que la géologie ancienne, l’érosion tertiaire, les glaciations quaternaires et leurs conséquences. L’article se focalise sur l’évolution du paysage à long terme de la partie non insulaire des Hautes Terres du nord-ouest d’Écosse, c’est-à-dire les Highlands. On éludera donc le travail sur les côtes, sur les archipels des Orcades et des Hébrides, et sur la Province Volcanique Tertiaire, reprises depuis dans la thèse de Le Cœur (1994), ainsi que les vues d’ensemble climatiques et hydrographiques et les abondantes analyses pétrologiques et sédimentologiques.

Il est inhabituel pour des géomorphologues étrangers de mener des programmes de recherche en Grande-Bretagne, et on déplorera ici que l’absence de fertilisation croisée entre écoles de pensée nationales, ainsi que l’attrait pour la recherche dans des régions plus éloignées et plus prestigieuses, soient à terme nuisibles à la discipline et ses protagonistes. En dépit d’une large ignorance du détail des travaux de Godard par la communauté écossaise des sciences de la Terre, les aspects plus accessibles de son travail demeurent malgré tout reconnus en Écosse (Sissons, 1976a ; Hall, 1991 ; Hall et Bishop, 2002), notamment ses levés topographiques des surfaces d’érosion. Néanmoins, beaucoup de ses idées plus générales et la plupart de ses observations perspicaces sont restés dans l’ombre, et sans presque aucune postérité en Grande-Bretagne.

Certes, pour que la science reçoive quelque écho, elle doit se rendre compréhensible, doit être communiquée avec compétence, et compter sur une large diffusion. Les raisons pour lesquelles le travail de Godard n’est jamais entré au panthéon de la géomorphologie anglophone en général sont examinées ici. On relèvera certaines évidences, notamment l’absence d’une traduction en anglais, pas même de manière résumée, mais aussi son style littéraire et sa façon engagée et combative d’aborder les problèmes (l’écriture scientifique anglo-américaine étant censée être concise, neutre et impersonnelle). Plus fondamentalement, la thèse a été publiée à une époque marquée en géographie physique par un changement de paradigme scientifique majeur favorisant la géomorphologie dynamique. Au moment où la recherche anglophone entreprenait son aventure quantitative et sa focalisation sur les processus, Godard restait ancré dans une approche française régionaliste, employant des méthodes encore limitées aux observations visuelles, à l’interprétation des cartes, et aux analyses géologiques de routine. Affronter un si gros volume était donc une tâche décourageante, même si, comme ce fut le cas pour le présent auteur, les dividendes se sont avérées considérables à condition d’y consacrer une lecture attentive. Cet effort a permis de révéler l’intérêt de détenir toutes les conclusions d’une campagne de recherches contenues dans une seule source bibliographique, au lieu d’être éparpillées entre plusieurs articles comme c’est trop systématiquement le cas en Grande Bretagne.

L’actualité de Godard quarante ans après la parution de sa thèse est examinée sous cinq rubriques : les surfaces d’érosion (y compris l’altération différentielle) ; l’évolution du paysage à long terme (notamment les origines du relief paléique) ; l’inefficacité et la sélectivité de l’érosion glaciaire ; la migration des lignes de partage des eaux sous l’effet de l’englacement ; et les limites des glaces (y compris l’insignifiance des dépôts glaciaires et des processus post-glaciaires durant l’Holocène). On cite encore Godard aujourd’hui comme l’auteur le plus crédible en ce qui concerne l’analyse des surfaces d’érosion en Écosse, en grand partie en raison de ses levés topographiques remarquablement détaillés et généralement valides des surfaces d’érosion, exhumées ou non. Ses cinq surfaces tertiaires comprennent une surface dite écossaise étendue, avec son knick brutal caractéristique ; et une surface dite intermédiaire, plus ancienne, qui indique un soulèvement en dôme. La gamme d’altitudes varie d’une région à l’autre, mais des surfaces définissent dans l’ensemble un système en escalier avec des niveaux à 800-1000 m, 650-750 m, 400-600 m, 180-300 m et 90-180 m. Au-delà des simplistes sommets concordants davisiens, Godard utilise ces corrélations pour identifier des effets de déformation tectonique et des soulèvements saccadés. Ses levés topographiques n’ont toutefois pas encore été analysés par des techniques numériques modernes. Ils soulèvent encore des interrogations en ce qui concerne certains critères d’identification et de validation par des méthodes indépendantes. Il reste aussi à expliquer pourquoi certaines surfaces sont en forme de banquettes tandis que d’autres sont des vestiges de plateau, à justifier les étendues parfois vastes qui séparent les vestiges de ces surfaces fragmentées, et à identifier les processus impliqués (par ex. fig. 4). Hormis les travaux de Le Cœur (1994), essentiellement restreints à la province volcanique, les travaux français ultérieurs à la thèse de Godard sur l’altération différentielle n’ont pas encore fait l’objet d’une mise en application en Écosse continentale.

La plus haute surface, ou surface supérieure selon Godard, ne doit pas être confondue ou amalgamée avec les banquettes et plateaux intermédiaires. Elle comprend des vestiges d’une surface ancienne conservée sur les sommets onduleux de la topographie régionale. Godard omet de préciser cette distinction, et même s’il écarte la théorie de la submersion mésozoïque suivie d’une table rase au Tertiaire, il n’explore pas le potentiel offert pour retracer une évolution subaérienne ininterrompue du socle calédonien allant de l’orogénèse et sa surface infra-dévonienne à la surface actuelle des sommets (fig. 5). Godard est reconnu pour ses reconstructions de cette surface infra-dévonienne. Celles-ci divergent de celles proposées par Bremner (1942), et Godard la différencie d’autres topographies anciennes en voie d’exhumation par l’érosion dans la même région.

L’œil de Godard pour les palimpsestes paysagers est remarquable. Ce talent inclut le Quaternaire, où l’auteur préfigure des travaux britanniques ultérieurs en identifiant l’héritage des glaciations pré-dévensiennes, notamment les étages différents du développement des cirques. Le scepticisme de Godard en ce qui concerne l’efficacité de l’érosion glaciaire est passé en grande partie inaperçu. Il identifie en Écosse des situations très répandues qui infirment cette idée reçue, et ses arguments invitent à réexaminer les parts respectives des érosions glaciaire et fluviale dans le façonnement du relief actuel. Ses interprétations quelque peu hérétiques à l’époque ont suggéré, avant d’autres auteurs, que le concept d’érosion linéaire sélective (Sugden, 1968) pouvait être mis à l’épreuve même dans l’ouest très découpé (fig. 6).

Godard exprime également un certain dédain vis-à-vis des dépôts quaternaires, insignifiants par leur volume et leur prégnance visuelle, et des processus holocènes dans le paysage actuel. Il n’éprouve presque aucun intérêt à retracer les limites des dernières avancées, mineures, des glaciers dévensiens. Ceci s’inscrit en contrepoint de la focalisation sans doute excessive sur ces vestiges glaciaires et périglaciaires qu’affectionnent les géomorphologues britanniques. Ceci n’a pas empêché Godard d’avoir été le premier à détecter des paléo-nunataks dans les Hautes Terres d’Écosse continentale, et d’en déduire à partir de leur distribution la configuration générale de la calotte glaciaire durant son maximum d’extension. Cette observation pionnière n’a été exploitée que beaucoup plus tard, par Ballantyne et al. (1998).

Tour à tour audacieux et réservé, Godard est le premier à avoir effectué le levé topographique du déplacement vers l’est de la principale ligne de partage des eaux. Sauf à ses terminaisons extrêmes, il se limite prudemment aux sous-bassins dont la capture paraît la plus évidente (fig. 7). Il intègre les effets de l’effondrement tectonique du Minch, mais ne prend pas en considération ses conséquences sur l’évolution du réseau hydrographique régional. Il reconnaît (après Linton, 1949) l’ouverture de nombreuses brèches par les glaces, sans toutefois en aborder l’âge, l’étendue ou l’impact possible des cas principaux.

Deux lacunes chez Godard se rapportent au fan delta du Ness, qui est unique en Grande-Bretagne (Sissons, 1981), et à l’importance des volumineux éboulements paraglaciaires de versants rocheux (Jarman, 2006). Son penchant pour s’en prendre aux travaux des personnalités établies, telles que Bremner et Linton, plus par la force de l’argumentation logique que par des démonstrations appuyées par des faits de terrain, a peut-être aussi nui à sa crédibilité auprès de lecteurs anglophones. Plusieurs de ses propres idées géomorphologiques, aussi brillantes soient-elles, sont fondées davantage sur des intuitions et des extrapolations que sur les analyses méticuleuses du type de celles qui seront menées un peu plus tard par Sissons et son école. Les méthodes de Godard (notamment pour le levé topographique des surfaces d’érosion) et ses références aux travaux antérieurs sont de qualité inégale, et l’auteur se laisse parfois aller au débat d’opinion plus que ne l’autoriserait habituellement une démarche scientifique. Pour ces défaillances de démarche et de style, il est instructif de comparer l’accueil général dans le monde anglophone de la thèse de Godard à celui qu’a reçue celle de son collègue et ami Rapp (1960).

Le magnum opus de Godard gagne aussi à être examiné à travers les clés de relecture fournies par l’ouvrage sur Les régions de socle, récapitulation précieuse de l’école française dont Godard est devenu un chef de file (Godard et al., 1994, traduit en anglais en 2001). Cet ouvrage montre la grande influence de sa thèse sur le cours des recherches francophones ailleurs dans le monde, en particulier dans les plus vieilles chaînes de montagnes du monde. Cet ouvrage fait aussi ressortir la presque totale absence de mise à jour de ses idées sur les Hautes Terres d’Écosse. Le travail de Le Cœur (1988) demeure l’exception, bien que cet auteur n’ait que peu publié.

Pour résumer les réussites de Godard, on doit retenir qu’il a été parmi les premiers à identifier : les paléo-nunataks (et donc les anciennes limites supérieures de la calotte glaciaire écossaise) ; les paysages en palimpseste (quaternaires mais aussi beaucoup plus anciens) ; les vestiges d’une haute surface pré-glaciaire assez vallonnée, et enfin les déplacements systématiques des principales lignes de partages des eaux. Il est le premier à avoir défié les orthodoxies régnantes sur la prédominance de l’érosion glaciaire dans les massifs montagneux, et sur l’enfouissement des racines des montagnes calédoniennes sous une épaisse couverture de sédiments mésozoïques. Il a développé enfin une cartographie presque exhaustive des surfaces d’érosion tertiaires, devenue un modèle de référence pour ce qui se rapporte aux reliefs à multiples niveaux étagés. Sa démarche holiste et son art de la synthèse restent presque sans équivalent parmi les études régionales portant sur l’évolution du paysage, surtout dans les Îles britanniques. Ces qualités ont ouvert la voie à de nombreux travaux sur les interactions entre géologie, tectonique et climat en France sans toutefois que le prototype écossais ait bénéficié par la suite des progrès réalisés ailleurs.

Nous concluons sur un appel à revenir, grâce aux travaux méconnus de Godard, sur l’étude géomorphologique des Hautes Terres d’Écosse continentale en tant que microcosme de l’évolution du relief à long terme dans les régions de socle, voire des régions de marge passive aux latitudes moyennes. À partir de cette réévaluation, et dans la perspective de recherches futures, on peut dresser une liste de thèmes scientifiques à la fois stimulants et controversés, tous en germe dans la thèse de Godard mais restés sans réponse définitive : l’altération différentielle et ses conséquences sur le relief ; les surfaces d’érosion et leur façonnement en fonction de niveaux de base régionaux mais aussi locaux ; formes à contrôle structural et formes d’érosion ; soulèvement et basculement au début du Cénozoïque et la recherche de leurs causes géodynamiques ; la submersion mésozoïque, sa réalité, son étendue, et son rôle, à ré-évaluer grâce à des études de thermochronologie basse température ; les origines de l’actuelle surface des sommets, et sa dérivation à partir de la discordance calédonienne (Caledonian Unconformity) ; l’évolution des réseaux hydrographiques et la migration des lignes de partage sur le long terme (y compris le rôle de la tectonique) ; la disposition actuelle et l’altitude absolue des hautes surfaces ; les impacts relatifs de l’érosion cénozoïque (fluviale) et quaternaire (glaciaire), y compris dans les captures de drainage ; enfin les effets sur le long terme de l’isostasie.

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Table des illustrations

Titre Fig. 1 – Northwest Scotland, showing locations, features, and lithologies referred to in the text.Fig. 1 Le Nord-Ouest de l’Écosse, avec toponymes, sites et lithologies mentionnés dans le texte.
Légende The NW Highlands lie to the north of the Great Glen. 1: internal (etch?) basins; 2: Tertiary Volcanic Province; 3: Old Red Sandstone; 4: Moine thrust; 5: Strahconon fault; 6: Quoich line; 7: Kyle-Dingwall railway; 8: preserved meanders (KL: Kyle Rhea–Loch Long; LH: Loch Hourn; OY: river Oykell). LD: Loch Duich; SC: strath Croe.1 : bassin interne (alvéole d’altération différentielle ?) ; 2 : Province volcanique tertiaire ; 3 : Vieux grès rouge ; 4 : chevauchement de Moine ; 5 :faille de Strathconon ; 6 : Quoich line ; 7 : voie ferrée de Kyle à Dingwall ; 8 : méandres conservés (K : Kyle Rhea–Loch Long ; LH : Loch Hourn ; O : rivière Oykell). LD : Loch Duich ; SC : strath Croe.
URL http://geomorphologie.revues.org/docannexe/image/1292/img-1.jpg
Fichier image/jpeg, 268k
Titre Fig. 2 – Sgurr nan Conbhairean (1105 m), one of the higher peaks in the Scottish NW Highlands, a pyramide résiduelle assez lourde [325].Fig. 2 Sgurr nan Conbhairean (1105 m), une pyramide résiduelle assez lourde [325] et l’un des plus hauts sommets dans les Hautes Terres de l’Écosse du Nord-Ouest.
Légende Note the tip of its smooth cone, which probably rose higher before truncation by the deep cirque behind the left shoulder. The paleic surface comprises a distinct monadnock swelling steeply from the broad bench at 950–1000 m well seen to its right. The summit and shoulders are probably below the main periglacial trimline, but appear only lightly glaciated. Godard did not map his surface supérieure in this area. View east from A’ Chràlaig (1120 m), a similar monadnock with scantier traces of paleic relief. Photograph: D. Jarman.Noter la pointe émoussée de son sommet, qui s’élevait probablement plus haut avant d’être réduite par la morsure profonde du cirque en arrière de l’épaulement situé sur la gauche. La surface paléique comporte un monadnock qui se dresse nettement au-dessus de la large banquette à 950–1000 m, visible sur la droite. Le sommet et les épaulements se situent probablement au-dessous de la limite glaciaire, mais ne semblent avoir subi que de légères modifications par l’érosion glaciaire. Godard n’a pas effectué le levé topographique de sa surface supérieure dans cette région. Vers l’est, on observe d’A’ Chràlaig (1120 m) un monadnock semblable avec des vestiges plus réduits du relief paleique. Photo : D. Jarman.
URL http://geomorphologie.revues.org/docannexe/image/1292/img-2.jpg
Fichier image/jpeg, 72k
Titre Fig. 3 – Extensive upland erosion surfaces in Easter Ross partly mapped by Godard. Viewed from Diebidale Ridge (691 m) looking west to Beinn Dearg, the northernmost summit in Scotland over 1050 m asl (A).Fig. 3 Hautes surfaces d’érosion de grande étendue en Easter Ross, partiellement cartographiées par Godard. A : vue vers l’ouest depuis Diebidale Ridge (691 m) on aperçoit Beinn Dearg, le sommet (à 1050 m d’altitude) le plus septentrional de l’Écosse.
Légende Foreground: not identified by Godard as a surface, but identical to hauts paliers. Middle ground: mapped as hauts paliers d’érosion; beyond them, slightly lower uplands (not well seen) are mapped as surface intermédiaire. Right skyline: Carn Bàn plateau 4x10 km, boldly swelling summits 845-822 m mapped as surface supérieure, other selected benches and outliers as hauts paliers;. Left skyline: mountains of the Beinn Dearg massif, eight fragments mapped as surface supérieure despite summits ranging between 927 and 1084 m (most fragments sub-kilometric, but Am Faochagach partly seen extreme left is one of Godard’s three largest at 3x2 km). The entire ensemble forms a coherent, smoothly hilly preglacial landscape, the three mapped surfaces merging with few pronounced breaks other than glacial troughs (the narrow axial trough of Gleann Mor–Gleann Beag is unseen beyond the middle ground, and is ~300 m deep). Photography: D. Jarman.Le premier plan, quoique non identifié par Godard comme une surface, est identique au second plan, identifié comme un haut palier d’érosion. Derrière ces niveaux, les terrains à peine en contrebas sont signalés par Godard comme surface intermédiaire, bien que la distinction soit peu perceptible. Sur l’horizon, à droite, plateau de Carn Bàn (4 x 10 km), sommets proéminents à 845-822 m attribués par Godard à la surface supérieure, et autres banquettes et pics isolés identifiés comme hauts paliers. Sur l’horizon, à gauche, montagnes du massif de Beinn Dearg, huit fragments identifiés comme surface supérieure malgré l’altitude des sommets entre 927 et 1084 m (la plupart des fragments font moins d’un kilomètre carré, sauf Am Faochagach, visible à l’extrême gauche, l’un des trois plus grands : 3 x 2 km). L’ensemble forme un paysage pré-glaciaire lisse et vallonné, mais cohérent. Les trois surfaces identifiées se recoupent sans ruptures topographiques marquées en dehors des brèches formées par le creusement glaciaire (l’étroite dépression linéaire de Gleann Mor–Gleann Beag, qui n’est pas visible au-delà du second plan, est profonde de ~300 m). Photo : D. Jarman
URL http://geomorphologie.revues.org/docannexe/image/1292/img-3.jpg
Fichier image/jpeg, 36k
Titre Fig. 3 – Extensive upland erosion surfaces in Easter Ross partly mapped by Godard. Viewed from Dunan Liath (691 m) looking north to Bodach Beag (822 m) and Càrn Alladale (B)Fig. 3 Hautes surfaces d’érosion de grande étendue en Easter Ross, partiellement cartographiées par Godard. B : vue vers le nord depuis Dunan Liath (691 m) en direction de Bodach Beag (822 m) et Càrn Alladale.
Légende Foreground: hauts paliers above Gleann Mòr glacial trough; middle ground: broad ridge descending gently eastward, mapped as small fragments of hauts paliers (left) and surface intermédiaire (right edge), but with no obvious distinction; skyline: small widely separated fragments of surface supérieure, hauts paliers, and surface intermédiaire from left to right. Most of skyline not assigned to any surface. Photography: D. Jarman.Au premier plan, hauts paliers au-dessus de la dépression glaciaire de Gleann Mòr. Au second plan, large crête descendant vers l’est, identifiée comme un ensemble de petits fragments des hauts paliers (gauche) et de surface intermédiaire (bord droit), mais sans critère de distinction très nets. Sur l’horizon, de droite à gauche, petits fragments espacés de la surface supérieure, de hauts paliers et de la surface intermédiaire. La majeure partie de la ligne d’horizon n’est attribuée à aucune surface. Photo : D. Jarman
URL http://geomorphologie.revues.org/docannexe/image/1292/img-4.jpg
Fichier image/jpeg, 40k
Titre Fig. 4 – The Monar internal basin, Wester Ross, immediately east of the main Highland watershed, a testing ground for etch processes and erosion surfaces. For location see fig. 1.Fig. 4 Le bassin intérieur de Monar, Wester Ross, juste à l’est de la ligne principale de partage des eaux : un laboratoire naturel pour mettre en regard processus d’altération différentielle et surfaces d’érosion (localisation : fig. 1)
Légende A: form of Monar basin with surrounding fragments of Godard’s three highest surfaces and additional paleic relief. 1: Monar basin outlined by the 457 m (1500 feet) contour; 2: main Highlands watershed; 3: inferred pre-glacial watershed; 4: glacial breaches; 5: glacio-fluvial incision; 6: Monar gorge; 7: Strathconon fault; 8: gulls-wing upland drainage. The sections confirm Godard’s identification of multi-storey relief surrounding the basin, which displays marked asymmetry in section A1. Note that valley widths at the 457 m contour, just 10 km east of the watershed, are 1.5 km for the Meig and the Orrin, 2 km for the Cannich and the Affric, and 4 km for the Monar. A : le bassin de Monar avec les fragments des trois surfaces les plus élevées de Godard et l’ajout du relief paléique. 1 : bassin de Monar souligné par l’isohypse 457 m (1500 pieds) ; 2 : ligne de partage des eaux des Highlands ; 3 : ligne de partage des eaux hypothétique pré-glaciaire ; 4 : trouées glaciaires ; 5 : incision (fluvio-)glaciaire ; 6 : gorge de Monar ; 7 : gorge de Strathconon ; 8 : réseau de vallées dendritique. Les coupes confirment l’identification effectuée par Godard de relief à niveaux multiples autour du bassin, avec une asymétrie marquée illustrée sur la coupe A1. Noter que les largeurs des vallées au niveau de l’isohypse 457 m, à peine 10 km à l’est de la ligne de partage des eaux, sont de 1.5 km pour la Meig et l’Orrin, 2 km pour la Cannich et l’Affric, et 4 km pour la Monar.
URL http://geomorphologie.revues.org/docannexe/image/1292/img-5.png
Fichier image/png, 272k
Titre Fig. 4 – The Monar internal basin, Wester Ross.Fig. 4 Le bassin intérieur de Monar, Wester Ross.
Légende B: view NNE approximately along line of section A1 from below point 1089 to Maoile Lunndaidh plateau (point 1007), showing the surface supérieure (SS) grading smoothly into the hauts paliers (HP), and more pronounced surface intermédiaire (SI) bench in middle ground. B : vue vers le NNE à peu près dans l’alignement de la coupe A1, du point 1089 jusqu’au plateau de Maoile Lunndaidh (point 1007). Cette vue montre la surface supérieure se raccordant aux hauts paliers, et un témoin net de la surface intermédiaire au second plan.
URL http://geomorphologie.revues.org/docannexe/image/1292/img-6.jpg
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Titre Fig. 5 – Ben Wyvis and Inchbae, Central Ross-shire. For locations see fig. 1.Fig. 5 Ben Wyvis et la cuvette d’Inchbae, Ross-shire central (voir fig. 1 pour la localisation).
Légende The Inchbae cuvette or internal basin is not confined to the augen-gneiss outcrop, but englobe three lithologies. Ben Wyvis is the only high massif framed by Old Red Sandstones (ORS) outcrops. The cross-section suggests how they might assist in reconstructing its scale soon after the close of the Caledonian orogeny (geology interpolated from British Geological Survey sections in vicinity). Key to symbols: 1: Old Red Sandstone (on basal unconformity), with M (Middle) and L (Lower; the contact at SE flank is Emsian); 2: breccia and conglomerate; 3: breccia and conglomerate along fringes; 4: sources of conglomerate after Peach et al. (1912), with figures indicating maximum clast dimension in metres; 5: augengneiss (AG) with unroofing domes (IB: Inchbae; CC: Carn Chuineag, occurs north of section); 6: Moinian schist (SCH), with psammite (top) and pelite (bottom); 7: Torridonian and Cambrian pebbles (T+C), occurring only in Middle ORS and in outrcops currently 50 km to the west; 8: preglacial land surface including maximum relief (dashed lines) NE of section (Ben Wyvis range only; 772 may also be a preglacial remnant); 9: Meall a’ Ghrianain outlier (772) and Meall nam Mullach (SCH:AG); 10: faults, thrusts; 11: Caledonide major sinistral strike-slip fault (SC: Strathconon fault; SG: Strathglass fault). The theoretical maximum elevation envelopes apply strength equilibrium slopes of 20 (the lowest residual friction angle generally found in schists, allowing for significant erosion of the orogenic pile towards conditional stability), and 30 (a median figure attainable during the period of rapid upbuilding). The peak friction angle of 40 in schists would theoretically yield a summit of 6800 m above present sea level, but while locally sustainable, syn-orogenic erosion would prevent literal attainment. The notional profile of the Wyvis range is centred above the reconstructed preglacial whaleback mountain, which in turn reflects the greater resistance of the Glenfinnan Group pelites. The high SE face is adopted from Trewin and Thirlwall (2002, fig. 8.14 therein), which indicates high mountains with deeply incised valleys (and) alluvial fans.La cuvette d’Inchbae n’est pas confinée à l’affleurement de gneiss œillé, et met en jeu trois lithologies différentes. Le massif de Ben Wyvis est le seul qui soit encadré par des affleurements de Vieux grès rouge. La coupe suggère comment ces grès peuvent servir à la reconstruction de l’étendue du massif après la fin de l’orogenèse calédonienne (géologie interpolée des coupes voisines levées par le British Geological Survey). 1 : Vieux grès rouge (sur discordance basale), avec distinction entre étages M (Moyen) et L (Inférieur; le contact au flanc SE est Emsien) ; 2 : brèches et conglomérats ; 3 : brèches et conglomérats sur les bordures ; 4 : sources des conglomérats selon Peach et al. (1912), avec chiffres indiquant la dimension maximale des clastes en mètres ; 5 : gneiss œillé (AG) affleurant en dôme (IB: Inchbae; CC: Carn Chuineag localisé au nord de la coupe) ; 6 : schiste moinien (SCH), avec psammite (demi-caisson du haut) et pélite (demi-caisson du bas) ; 7 : galets Torridoniens et Cambriens (T+C), présents seulement dans le Vieux grès rouge moyen et dans des affleurements actuellement présents 50 km plus à l’ouest ; 8 : surface topographique pré-glaciaire avec enveloppe topographique maximum (lignes tiretées) au NE de la coupe (seul le massif du Ben Wyvis est représenté ; la cote 772 est peut-être un résidu pré-glaciaire ; 9 : buttes de Meall a’ Ghrianain (772) et Meall nam Mullach (SCH:AG) ; 10 : failles, chevauchements ; 11 : failles calédoniennes majeures à jeu décrochant sénestre (SC: faille de Strathconon; SG: faille de Strathglass). Les enveloppes d’altitude maximum théorique de la chaîne calédonienne impliquent des pentes d’équilibre critiques de 20 (plus faible angle de friction résiduelle généralement rencontré dans les schistes, tenant compte de l’érosion considérable du prisme orogénique en équilibre stationnaire) à 30 (valeur médiane réalisable durant la période de construction rapide de l’orogène). Une valeur maximale de 40 sur schistes fournirait un sommet théorique de 6800 m au-dessus du niveau actuel de la mer, mais cette éventualité serait en réalité inatteignable en raison de l’érosion syn-orogénique. Le profil hypothétique de la chaîne de Wyvis est centré sur la montagne pré-glaciaire reconstruite en forme de dos de baleine, qui reflète la forte résistance des métapélites du Groupe de Glenfinnan. La haute façade vers le sud-est est adoptée de Trewin et Thirlwall (2002, leur fig. 8.14), qui décrivent de hautes montagnes avec des vallées profondément incisées et des cônes alluviaux.
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Titre Fig. 6 – A case for selective linear erosion by glaciers in the dissected Western Highlands, as suggested by schematic profiles along main watersheds.Fig. 6 Le cas de l’érosion linéaire sélective par les glaces dans les Hautes Terres de l’ouest, suggérée par les profils schématiques des principales lignes de partage des eaux.
Légende Profile (a) shows its classic effects in the Eastern Highlands, with simple cirques, troughs and occasional sharply-incised breaches. Profile (b) suggests that the scoured relief of the Western Highlands is merely a surface roughening of essentially similar selective erosion of deeper troughs, many of them breached and cross-breached, but with much of the preglacial topography surviving with increasing intactness at higher levels. 1: preglacial land surface remnants; 2: superficially scoured glacial topography; 3: background relief, including cross-breaches between main valleys (4).Le profil (a) montre ses effets classiques dans les Hautes Terres de l’est, avec des cirques simples, des auges, et d’occasionnelles brèches profondément incisées. Le profil (b) suggère que le relief récuré des Hautes Terres de l’ouest n’est que la version plus accidentée d’un paysage fondamentalement semblable à (a), avec des entailles d’érosion sélective plus profondes. La plupart des interfluves encadrants sont troués par des brèches de transfluence, mais les survivances de topographies pré-glaciaires demeurent plus intactes vers les niveaux plus élevés du paysage..1 : topographies pré-glaciaires résiduelles ; 2 : topographie glaciaire ayant subi un râclage superficiel ; 3 : topographie d’arrière-plan avec trouées de transfluences entre les vallées (4).
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Titre Fig. 7 – The main watershed of the NW Highlands, showing displacements from preglacial positions inferred by Godard (1965) and Jarman (2006).Fig. 7 La ligne principale de partage des eaux des Hautes Terres du Nord-Ouest, montrant les déplacements des positions pré-glaciaires déduites par Godard (1965) et Jarman (2006).
Légende Note how the catchment area of the River Ness is almost entirely intercepted by Loch Ness, rendering the fan-delta at Inverness (see fig. 8) patently anomalous. 1: present main watersheds; 2: inferred pre-Quaternary watersheds (Jarman, 2005); 3a: watershed displacements according to Godard and author; 3b: displacements according to author; 3c: displacements according to Godard, doubtful; 4: Loch Linnhe river (Godard, doubtful); 5: steep belt/flat belt (SB/FB, Quoiche line); 6: mountains in flat belt (750–950 m asl); 7: river Ness catchment.Noter la manière dont le bassin hydrographique de la Ness est presque complètement intercepté par le Loch Ness, rendant de ce fait anormal le fan-delta d’Inverness (fig. 8). 1 : principales lignes de partage des eaux actuelles ; 2 : lignes de partage des eaux pré-quaternaires hypothétiques (Jarman, 2005) ; 3a : déplacement de ligne de partage des eaux selon Godard et l’auteur ; 3b : déplacement selon l’auteur ; 3c : déplacement (discutable) selon Godard ; 4 : Loch Linnhe river (selon Godard, mais discutable) ; 5 : steep belt/flat belt (SB/FB, Quoiche line) ; 6 : reliefs montagneux de la flat belt (750–950 m d’altitude) ; 7 : bassin versant de la rivière Ness.
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Titre Fig. 8 – The anomalous large ‘fan-delta’ at the mouth of the 7 km-long River Ness is attributed to the Glen Roy jökulhlaup.Fig. 8 Le fan-delta anormalement vaste au débouché de la Ness (7 km de long), attribué à la jökulhlaup du Glen Roy.
Légende It creates the site for the city of Inverness, and narrows the Moray-Beauly Firth sufficiently to permit its bridging at Kessock. The deltaic form is defined by the Caledonian Canal (left), River Ness (centre) and a former cliffline (centre right), with wooded islands of Quaternary deposits surviving within the paleo-flood channel. View looking NE. Photograph by kind permission of The Highlands Council.Ce fan-delta a déterminé le site de la ville d’Inverness, et suffisamment rétrécit le Moray-Beauly Firth pour avoir permis la construction du pont de Kessock. La forme deltaïque est délimitée par le Caledonian Canal (à gauche), la rivière Ness (au centre) et une ancienne falaise (au centre droit), avec des îlots boisés constitués de dépôts quaternaires qui ont survécu dans le paléochenal d’inondation. Vue vers le nord-est. Cliché reproduit avec l’aimable autorisation du Highlands Council.
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Titre Fig. 9 – The Ben Hee paraglacial rock slope failure (RSF).Fig. 9 L’écroulement paraglaciaire du versant rocheux de Ben Hee.
Légende View across upper part from the NE, with the 5–15 m source scarp and trench (right centre, continuing up to skyline above snowpatch) misinterpreted by Godard as a perched moraine at 800 m asl. This is one of the largest RSFs in Scotland within a cirque, affecting 0.4 km2. Photograph D. Jarman.Vue sur la partie supérieure depuis le NE, montrant l’escarpement de la couronne d’écroulement d’une hauteur de 5 à 15 m ainsi que la gouttière (au centre droit, continuant jusqu’à la ligne d’horizon au-dessus de la plaque de neige), interprété par erreur par Godard comme une moraine perchée à 800 m d’altitude. Il s’agit d’un des plus grands éboulements d’Écosse, ayant eu lieu à l’intérieur d’un cirque, qui affecte une superficie de 0,4 km2. Cliché D. Jarman.
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Titre Fig. 10 – The Sgurr nan Airgid RSF, Kintail, with its prominent slip bulge into Strath Croe.Fig. 10 Le glissement de Sgurr nan Airgid, Kintail, avec le bombement proéminent de la masse déplacée vers Strath Croe.
Légende View from the SE. At 1.5 km2 it is one of the six largest RSFs in the mainland Highlands. The failure splits the skyline ridge at 600–800 m asl, and descends almost to sea level. A slightly-deflected natural stream course down the right-hand side undercuts the steep and uncohesive toe, promoting extensive gully erosion misconstrued by Godard as anthropogenic. Photograph: D. Jarman.Vue du sud-est. Avec une étendue de 1,5 km2, il s’agit d’un des six plus grands glissements rocheux des Hautes Terres d’Écosse continentale. La masse glissée interrompt la crête sur la ligne d’horizon à 600–800 m d’altitude, et descend presque au niveau de la mer. Le cours d’un ruisseau se trouve légèrement dévié sur le côté droit et sape le lobe escarpé taillé dans le matériau peu cohésif de la masse glissée. Ceci provoque une érosion ravinante que Godard avait interprétée par erreur comme étant d’origine anthropique. Cliché D. Jarman.
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David Jarman, « Alain Godard on the NW Highlands of Scotland: present relevance for long-term landscape evolution studies », Géomorphologie : relief, processus, environnement, 2/2007 | 2007, 177-203.

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David Jarman, « Alain Godard on the NW Highlands of Scotland: present relevance for long-term landscape evolution studies », Géomorphologie : relief, processus, environnement [En ligne], 2/2007 | 2007, mis en ligne le 01 juillet 2009, consulté le 18 septembre 2014. URL : http://geomorphologie.revues.org/1292 ; DOI : 10.4000/geomorphologie.1292

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