FOREGS | Stream sediments summary information

Synopsis

As its contribution to the IUGS/IAGC Global Geochemical Baselines Programme, the Forum of European Geological Surveys (FOREGS, now EuroGeoSurveys), through its component surveys, collected various environmental materials (including stream sediments) to create geochemical baseline maps for Europe.

For the drainage samples and soils this was done at a scale that averages out to about one sample per 4700 km2.

A two-part geochemical atlas of Europe has been published (Salminen et al., 2005; De Vos et al., 2006) and databases, maps and atlases are freely available from web pages hosted by the Geological Survey of Finland (GTK).

Sample site selection was based on the Global Reference Network (GRN) grid cells developed for the purpose of Global Geochemical Baseline Mapping (Darnley et al., 1995), each cell being 160 x 160 km. The soil sampling procedure is described in detail in Salminen et al. (1998) and summarised below. The target was to collect from five 'random' sites within each cell.

The British Geological Survey collected a total of 60 stream sediment samples for FOREGS in the UK between August and October 1998.

Stream sediment sampling and analytical methodology

At selected drainage sites stream sediment and water was collected. Active stream sediment was collected from the small, second order drainage basins (catchment areas <100 km2).

Each sample was a composite of sample taken from 5–10 points over a stretch of 250–500 m along the stream.

The sediment is wet sieved, firstly through a 2 mm nylon screen, then a 150 µm nylon sieve, and the resulting fine sediment collected in a wooden gold pan.

The fine stream sediment is collected in a KraftTM paper bag. A minimum of 500 g of sediment (dry weight) was collected at each site.

The stream sediments were determined at a number of laboratories across Europe by a variety of analytical techniques: XRFS-WD, ICP-MS (following mixed acid extraction), ICP-AES (following aqua regia extraction), Hg analyser and a granulometric method for total organic carbon (TOC).

Data availability

Geochemical results and maps are freely available from FOREGS Geochemical Atlas of Europe hosted by the Finnish Geological Survey (GTK).

Data files take the form of a collection of zipped MS Excel files from which individual country subsets can be extracted using the country code field.

Excess sample powders were transferred in 2009 to the National Geoscience Data Centre (NGDC), British Geological Survey, Keyworth, Nottingham, UK.

References and links

Darnley, A G, Bjorklund, A, Bolviken, B, et al,   1995.  A Global Geochemical Database for Environmental and Resource Management.  Earth Science Series No. 19, UNESCO Publishing, Paris, 122 pp.

De Vos, W, and Tarvainen, T, (ed.) et al,  2006.  Geochemical Atlas of Europe. Part 2 - Interpretation of Geochemical Maps, Additional tables, Figures, Maps, and Related Publications. Geological Survey of Finland, Otamedia Oy, Espoo, 692 pp.

Salminen, R., Tarvainen, T., Demetriades, A, et al.  1998.  FOREGS Geochemical Mapping Field Manual. Geological Survey of Finland, Guide 47.

Salminen, R. (chief ed.) et al.  2005.   Geochemical Atlas of Europe. Part 1 - Background Information, Methodology and Maps. Geological Survey of Finland, Otamedia Oy, Espoo, 525 pp.