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Discussion |
Scott Wilson Kirkpatrick & Partners, Hong Kong.
P. WHITESIDE writes: Holmes & Jarvis have inferred that the obsequent scarplets on Ben Attow have formed as a result of movement of the jointed rock mass, yet they present no evidence that movement has occurred. In fact they go so far as to say that there are no signs of recent movement on the slope.
It would undoubtedly be difficult to find such evidence since these Moine Psammites are likely to present a fairly monotonous sequence in which displaced lithologies would not be apparent.
However, one may reasonably expect the scarplets to show some slickensiding, the orientation and sense of which could perhaps preclude its having been formed during some other, earlier joint movement.
In the absence of any actual evidence of movement it is necessary to discuss alternative explanations and in particular to give reasons for assuming that the scarplets have not just simply formed by erosion. Such erosion could, for instance, have occurred during glaciation by plucking of rock blocks by ice.
If the evidence for toppling movement is simply based on the present morphology of the hillside then I would suggest that the erosion explanation is perhaps more likely.
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