Workreport 2012-15

Models of Bedrock Surface and Overburden Thickness Over Olkiluoto Island and Nearby Sea Area

Mönkkönen, H.

English

76

In this report, a model of bedrock surface and a model of overburden thickness over the Olkiluoto Island and the nearby sea area are presented. Also in purpose to produce material for biosphere and radionuclide transport modelling, stratigraphy models of different sediment layers were created at two priority areas north and south of the Olkiluoto Island.

The work concentrated on the collection and description of available data of bedrock surface and overburden thickness. Because the information on the bedrock surface and overburden is collected from different sources and is based on a number of types of data the quality and applicability of data sets varies. Consequently also the reliability in different parts of the models varies.

Input data for the bedrock surface and overburden thickness models include 2928 single points and additional outcrops observations (611 polygons) in the modelled area. In addition, the input data include 173 seismic refraction lines (6534 points) and acoustic-seismic sounding lines (26655 points from which 13721 points are located in model area) in the Olkiluoto offshore area.

The average elevation of bedrock surface in area is 2.1 metres above the sea level. The average thickness of overburden is 2.5 metres varying typically between 2 – 4 metres. Thickest overburden covers (approximately 16 m) of terrestrial area are located at the western end of the Olkiluoto Island and in sea basin south of the island.

Bedrock surface, overburden thickness, stratigraphy, Olkiluoto.

Models of Bedrock Surface and Overburden Thickness Over Olkiluoto Island and Nearby Sea Area (pdf) (1.2 MB)