Applied geology, introduction, Cainozoic of north-east Scotland
|Merritt, J W, Auton, C A, Connell, E R, Hall, A M, and Peacock, J D. 2003. Cainozoic geology and landscape evolution of north-east Scotland. Memoir of the British Geological Survey, sheets 66E, 67, 76E, 77, 86E, 87W, 87E, 95, 96W, 96E and 97 (Scotland).
Contributors: J F Aitken, D F Ball, D Gould, J D Hansom, R Holmes, R M W Musson and M A Paul.
The Quaternary sediments of north-east Scotland play a major role in the economic development of the district. Although these deposits are generally thin, they cover some 90 per cent of the land surface onshore and most of the sea bed in the surrounding offshore area. Quaternary strata form the foundations for most urban, and industrial buildings, as well as road and rail links. They are also the source of most of the aggregate used in their construction. Much of the district’s drinking water has passed through these sediments and its most fertile soils are developed upon them. Many nature reserves and Sites of Special Scientific Interest (SSSIs), especially those concerned with wetland and dune habitats, result from accumulations of peat and blown sand during post-glacial times. Domestic and industrial waste is disposed by landfill into former workings in Quaternary sands and gravels or tipped on top of undisturbed permeable Quaternary sediments. Knowledge of the extent and nature of these deposits and other types of made ground, and the engineering properties of in situ Quaternary strata and deeply weathered bedrock, is crucial in determining ground conditions for future urban and industrial developments and protecting groundwater resources.
Planning considerations and conservation issues
One of the most fascinating attributes of the landscape of north-east Scotland is the degree to which the topography reflects the interplay between rock type, structure and geomorphological processes, the latter largely driven by climate changes throughout the Cainozoic. As a consequence, the district contains many sites where geological sequences are preserved; these contain evidence critical to understanding the landscape evolution not only of north-east Scotland, but also northern Britain and north-west Europe during the Cainozoic. This latest part of Earth history is particularly important, as it provides the environmental setting within which the whole of human cultural and economic development has taken place. It is only during the last thirty years, however, that the importance of the Cainozoic geological record of the frequency and rate of naturally occurring environmental changes has been generally recognised. It provides base-line data against which anthropogenic degradation of the environment, such as temperature changes caused by increased CO2 emissions, elevated sea levels, or vegetation changes due to farming intensification, can be gauged.
Decisions as to which Cainozoic sites should be conserved are based upon guidelines that try to encapsulate the range of scientific interest at each site. Some are designated as SSSIs on geological and geomorphological grounds. Short descriptions of several of these SSSIs are given in Important localities. Most of the key Quaternary sites were included in the Geological Conservation Review (GCR), initiated by the Nature Conservancy Council in 1977 and are fully described in Gordon and Sutherland (1993).
Several important Quaternary sequences are also preserved within SSSIs, National Nature Reserves (NNRs), Royal Society for the Protection of Birds (RSPB) reserves and local nature reserves, which were originally designated mainly on the basis of their botanical and wildlife importance. An example is the NNR covering the Sands of Forvie, north of Newburgh; this covers an extensive area of active and stabilised dunes of blown sand up to 60 m in height (Ritchie, 1992). The reserve was first established in 1959. The area was designated a SSSI in 1971, for its coastal plant communities, colonies of sea birds (it is home to Britain’s largest population of Eider duck), as well as its coastal geomorphology. Holocene sediments on the banks of the Ythan estuary, within the SSSI, include a thin bed of grey sand, deposited by tsunami waves from the second Storegga slide. It occurs beneath blown sand, peat and clay, in boreholes at Waterside (NK 007 267) on the eastern side of the estuary (Smith, 1984; Smith, et al., 1983, 1999). This ‘tsunami deposit’, which was generated by a massive submarine landslide on the Norwegian continental margin, is analogous to that recorded from the cores taken in the Philorth valley near Fraserburgh, about 40 km farther north.
Important Quaternary biogenic sequences are sometimes recorded from waterlogged peat mosses and lake basins, which are primarily conserved for their modern flora and fauna. For example, the Loch of Park, northeast of Banchory, is a local nature reserve that was established to protect its population of breeding birds, its reed beds and Alder woodland. Pollen records and radiocarbon ages, determined from Holocene and Late-glacial peats and organic muds recovered in cores taken from the lake basin, have been critical in establishing climatic and vegetational changes in north-east Scotland since deglaciation (Vasari, 1977).
Knowledge of the nature and distribution of Quaternary sediments are fundamental to decisions made regarding the economic and environmental well being of the district. Planning in the hinterland of Aberdeen, for example, not only requires forecasts of demand for housing, infrastructure and industrial construction, but also needs to ensure that adequate supplies of aggregates are available and that new building developments are not sited on the most attractive remaining aggregate resources. It was partly to this end that the detailed assessments of sand and gravel resources were undertaken between 1979 and 1990.
Development planning also benefits from knowledge of ground stability and foundation conditions and seismic hazard, which are discussed below, and groundwater vulnerability, described in the preceding section on hydrogeology. These and other factors, such as coastline evolution were initially evaluated for the hinterlands of Aberdeen and Peterhead, in two projects funded by the Scottish Office. The results of these two studies are presented in Smith (1983) and Peacock (1983).