Sedimentology and palaeoenvironmental significance of Late Devensian to Mid Holocene deposits in the Don Valley, north-east Scotland
The aim of this thesis was to produce models of the evolution of the Don Valley and its associated coastal lowland both during and following deglaciation, with the specific objective of identifying the pattern of deglaciation and to relate this to current theories of ice sheet and glacier decay in north-east Scotland, in particular the concept of 'Moraineless Buchan'. The specific problems addressed by the research were the valley floor morphology and sedimentary stratigraphy. Valley floor morphology was determined by air photo analysis, field mapping and surveying of terrace fragments, whilst the drift geology and stratigraphy were established from British Geological Survey and other borehole and trial pit records, field sediment analyses and by palynology and radiocarbon analyses of organic horizons. The models bring together the detailed stratigraphic, morphological, sedimentological and palaeoecological studies and rely heavily on a stratigraphy recognised in the principal exposures (predominantly gravel pits) together with data from B.G.S. maps, pre-existing boreholes, morphological mapping and temporary exposures. Detailed sedimentological investigations throughout the study area allowed the subdivision of the drift sequence into four broad groups, identified on the basis of their lithofacies associations:1) Braided outwash deposits2) Glaciolacustrine deposits3) Deltaic deposits4) Diamictons By correlating both temporally and spatially palaeogeographic models were constructed for the lower Don Valley (downstream of Kemnay) and the coastal lowlands. Farther upstream the scarcity of exposures and boreholes meant that correlation between widely dispersed sites proved difficult. Although both the concept of 'Moraineless Buchan' and the concept of an Early Devensian glaciation cannot be disproved, the evidence presented in this thesis provides further support for total glaciation of Buchan in the Late Devensian. Furthermore, it calls into question recently constructed ice limits in north-east Scotland.