Quaternary geomorphology of the Assynt area, N.W.Scotland

• Main Author: Lawson, Timothy John
• Format: Doctoral or Postdoctoral Thesis
• Language: unknown
• Published: The University of Edinburgh 1983
• Subjects: Loch Lomond; Ice Sheet
• Online Access: http://hdl.handle.net/1842/28409

The main factors influencing the distribution of geomorphic features in the Assynt area are geology and the location of Loch Lomond Advance glaciers. A study of glacial striae and erratics has enabled the construction of a model for the development of the last ice sheet. Glaciers developed in the corries on the N and E side of the Assynt mountains, coalesced and thickened until an ice divide was established, ice overtopping the mountain ridge to flow both eastwards and westwards; the ice divide was always situated to the E side of the mountains. Even the highest parts of the study area were covered by ice to a considerable depth. An early deglaciation of the area is suggested by a radiocarbon date of 18,040 240 years B.P. from fragments of reindeer antlers. Reconstruction of the seven Loch Lomond Advance glaciers that subsequently formed in the area has shown that the main snow -bearing airstreams came from the south and that the blowing of snow onto glaciers surfaces was a major factor in their development. Glacial friction cracks are widespread in the Assynt area. A revision of nomenclature and a simplified classification is suggested. Attempts have been made to characterise certain Assynt friction crack forms, and orientation studies suggest that they are useful ways of establishing the former ice flow direction when striae or ice -moulded bedrock are absent, as long as a large number of them are measured. Their orientation is sometimes affected by weakenesses in the bedrock. A study of the caves in the Cambrian dolomite of the area indicates that they originated phreatically, but subsequent lowering of the local water-table has tended to result in high-level, abandoned passages, often choked with clastic deposits, and lower - level passages containing the active streamways. Clastic cave sediments are largely allochthonous, being derived from local glacial deposits. The dating of certain calcite speleothems has shown that many of the main elements of the subterranean drainage network were in existence ...