Mapping of Quaternary deposits
Information about the distribution, structure and properties of Quaternary deposits is needed in connection with land use decisions, infrastructure projects etc. SGU’s mapping of these deposits provides basic data relating to a range of issues, including:
- the bearing capacity, stability and excavability of the ground, for example at the pre-design stage of road-building and similar projects
- landslide risks
- assessments of groundwater resources and the design of protection zones
- the risk of dispersion of toxic and other harmful substances in soil and groundwater
- the nutrient status, water retention capacity and acid sensitivity of soils
- the siting and design of wastewater treatment plants and landfill sites
- the identification and valuation of gravel and peat resources
- soil uptake and emissions of greenhouse gases
- land use in general
- assessments of the nature conservation value of land
- landscape development and climate change
Major users of data on Quaternary deposits include local authorities, county administrative boards, central government agencies, consultants, companies in the construction, aggregate, mineral and peat industries, the Swedish armed forces and higher education establishments.
Data on Quaternary geology are presented in the form of maps (printed and map databases), which provide a comprehensive picture of the distribution of Quaternary deposits and bedrock at or near the ground surface. Information about the thickness and depth characteristics of deposits is also presented in the form of point observations. In addition, the maps provide information about the appearance of the deposits.
Map sheet descriptions and basic databases contain additional information, for example the results of analyses, drilling and probes, and also information on striations and, in some cases, on features of particular geological interest. The descriptions also provide explanations relating to the maps and concise accounts of the geological development of the areas covered. Some of the maps do not include descriptions.
Mapping is mainly based on aerial photo interpretation and field reconnaissance. For the purposes of detailed mapping, reconnaissance takes place on foot in the terrain, while field reconnaissance for overview maps is mainly carried out by car. Quaternary deposits are identified visually at regular intervals with the help of a spade, auger or spiral. Visual identification is verified by means of samples taken for grain size analysis. Machine probes, machine excavation and seismic studies are carried out in certain places to investigate the three-dimensional structure of deposits.
The level of detail and content of the maps are geared to different user groups and applications. SGU is currently working on a series of regional overview maps that will cover large parts of the country by 2008 (scale: 1:100,000–1:250,000) and on more detailed maps of selected densely populated areas and areas that are potential ore environments (scale: 1:50,000).