This paper uses the elevation-relief ratio to constrain the horizontal and vertical extent of sub-horizontal denudation surfaces in Wales, United Kingdom.
Key words: sub-horizontal denudation surfaces, elevation-relief ratio, SRTM data, ESRI ArcMap, Wales.
Many such studies are underpinned by the identification and correlation of sub-horizontal denudation surfaces, despite numerous controversies surrounding this field of research (e.g.
The overall aim of the present paper is to demonstrate the value of the elevation-relief ratio as a geomorphological tool, which is able to analytically identify sub-horizontal denudation surfaces within heavily dissected landscapes; therefore, the elevation-relief ratio may be applied in a diverse range of geological and tectonic settings beyond the passive continental margin of northwest Europe.
Elevation-relief ratio values generally range between 0.15 and 0.85, with clustering between 0.40 and 0.60 (Pike & Wilson 1971); therefore, in this paper it is considered that elevation-relief ratio values between 0.00-0.40 and 0.60-1.00 both represent sub-horizontal surfaces, but that only those values between 0.60-1.00 represent sub-horizontal denudation surfaces as it is these that are characterized by a generally convex morphology.
those areas with elevation-relief ratio values of d"0.40 and e"0.60), whilst the maps presented in column (ii) depict only the areas defined as sub-horizontal denudation surfaces through the application of the elevation-relief ratio (i.e.
In order to constrain the vertical extent of any sub-horizontal denudation surfaces, altitude-frequency histograms have been constructed (Figure 7).
Despite the differences in horizontal surface area described in the previous section, changing the size of the circular neighbourhood does not have a marked influence on the altitudinal range occupied by sub-horizontal denudation surfaces; however, such surfaces do become progressively more pronounced as the size of the circular neighbourhood increases.
In this study four sub-horizontal denudation surfaces are shown at lower elevations in the altitude-frequency histograms; the prominence of these surfaces decreases with elevation.
The overall aim of this paper was to demonstrate the value of the elevation-relief ratio as a geomorphological tool, which is able to analytically identify sub-horizontal denudation surfaces within the heavily dissected landscape of Wales.
It is very difficult to reconcile the results described here with the tripartite classification of Brown (1960); in that study, evidence was presented for the existence of three widespread sub-horizontal denudation surfaces at between 210-330 m asl, 365-485 m asl, and 515-575 m asl.