Gordon, J.E. and Sutherland, D.G. GCR Editor: W.A. Wimbledon. 1993. Quaternary of Scotland. Geological Conservation Review Series No. 6. JNCC, Peterborough, ISBN 0 412 48840 X.
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L.J. McEwen
The gorge at Corrieshalloch is an excellent example of a gorge formed by glacial meltwaters; its form closely reflects the effects of bedrock controls.
Corrieshalloch Gorge
Corrieshalloch Gorge is exceptional in its length (c. 1.25 km), depth (60 m) and width (as narrow as 10 m at the lip). It is cut in undifferentiated Moine schists (psammite). Its form is determined by steeply dipping or vertical joints trending NW–SE and NE–SW (Peacock, unpublished data). The gorge can be subdivided into at least two parts, separated by the major waterfalls at Falls of Measach. In addition, there are several minor falls, for example, near Braemore junction. The modern channel is thus characterized by a stepped profile over these falls, which are interspaced with deep, boulder-filled pools. Ferguson (1981) observed that these are being progressively extended upstream by waterfall recession, at rates enhanced by the rock jointing.
The present form of Corrieshalloch Gorge can only be explained by a past period of extreme erosive activity. Although Whittow (1977) cites an earlier theory that the gorge reflects post-glacial entrenchment, he emphasizes that the scale of the feature makes this explanation unviable as a complete explanation. The currently favoured hypothesis is that the gorge was cut by meltwaters from the direction of Dirrie More (Peach et al, 1913a; Kirk et al., 1966; Sutherland, 1987b), although it is not established whether these were subglacial or proglacial. However, since the valley was probably a major meltwater discharge route during both ice-sheet deglaciation and the Loch Lomond Readvance, both may have contributed to the formation of the gorge (Sutherland, 1987b). Although there is no evidence that the gorge was ever re-occupied by ice after its incision, it would not be surpising if the gorge was a polycyclic feature, and that a significant channel was already cut into the valley shoulder at this locality prior to the onset of the last glaciation. Due to its glacial legacy, the present River Droma thus undergoes a dramatic change in controls (increased slope, increased confinement, and reduced sediment supply) as it enters the gorge.
Corrieshalloch Gorge is the most impressive of a number of gorges in this area (see, for example, the gorge along the lower Abhainn Cuileig), the form of which is determined by bedrock controls in the flaggy Moine schists (Peach et al., 1913a). It is a classic landform and is recognized as the best-known example of a steep-sided slot gorge in Scotland. The gorge was cut by meltwaters during the last phases of glaciation of the area as well as, probably, during earlier glacial events. The scale of the feature is particularly impressive, and in terms of its size and the presence of waterfalls, it is a more striking and varied feature than the other gorges in the area and also the dramatic, but less well-known gorge at Black Rock of Novar in Easter Ross (Miller, 1887; Peach et al., 1912).
Corrieshalloch Gorge is a classic example of a gorge formed by glacial meltwaters. It is notable for its length and depth and for showing, particularly well, the effects of geological controls on gorge formation. Its development probably reflects erosion by meltwaters during several glacial episodes.