Modified: 31.07.2009
Bedrock of Finland
Finland occupies the central part of the Precambrian Fennoscandian Shield. The Shield margin is exposed in the Finnish territory only in northwestern Lapland, where Caledonian allochthons (units in no.l in the legend) form the highest topographic region of Finland. To the south, the Shield margin is submarine, drowned by the shallow waters of the Gulf of Finland.
Archaean and Palaeoproterozoic rocks
Broadly, rocks of the Fennoscandian Shield are younger towards southwest. Finland occupies the main part of the transitional zone between dominantly Archaean and dominantly Palaeoproterozoic rocks.
Ancient continental margin and collisional tectonics
The deeply eroded Archaean crust (nos. 33-37), becomes increasingly covered westwards by earliest Palaeoproterozoic continental beds, c. 2000-2500 Ma in depositional age (nos. 28-32). What is often referred to as the Ladoga -Bay of Bothnia zone, or Raahe-Ladoga zone, represents an ancient continental margin, with accretionary growth of new crust westwards 1900-1800 Ma ago (nos. 11-27) and later. Roughly coevai with early crust-formation in the southwest was the collisional tectonics in northernmost Finland, where the Lapland granulite belt and adjacent lithologies (nos. 23-26) represent a major high grade thrust belt between two Archaean segments.
Formation of Finnish bedrock during 1400 million years
Owing to the rich variety of geological conditions leading to the formation of the bedrock of Finland, in a time span ranging from c. 3000 Ma (the oldest granitoids) to 1600 Ma (large rapakivi bodies), there are many different types of ore provinces, industrial mineral occurrences and useful rock materials.
Several Palaeoproterozoic ore provinces
The ophiolite-related ores of the Outokumpu region, chromite ores associated with 2440 Ma old layered intrusions, massive sulphide ores in the Ladoga -Bay of Bothnia zone, Ni-Cu ores associated with c. 1989 Ma old basic orogenic intrusions, etc. may be mentioned as examples.
Bedrock map of Finland during 1 : 1 million
The bedrock map 1 : 5 million has been prepared from the updated Bedrock map of Finland 1 : 1 million (see reference below). The contents of the
original map are much more detailed with respect to the division of lithology and stratigraphy, with special attention paid to the geological evolution of Finnish bedrock and topographic and tectonic palaeoenvironments in different times.
Broadly, rocks of the Fennoscandian Shield are younger towards southwest. Finland occupies the main part of the transitional zone between dominantly Archaean and dominantly Palaeoproterozoic rocks.
Ancient continental margin and collisional tectonics
The deeply eroded Archaean crust (nos. 33-37), becomes increasingly covered westwards by earliest Palaeoproterozoic continental beds, c. 2000-2500 Ma in depositional age (nos. 28-32). What is often referred to as the Ladoga -Bay of Bothnia zone, or Raahe-Ladoga zone, represents an ancient continental margin, with accretionary growth of new crust westwards 1900-1800 Ma ago (nos. 11-27) and later. Roughly coevai with early crust-formation in the southwest was the collisional tectonics in northernmost Finland, where the Lapland granulite belt and adjacent lithologies (nos. 23-26) represent a major high grade thrust belt between two Archaean segments.
Formation of Finnish bedrock during 1400 million years
Owing to the rich variety of geological conditions leading to the formation of the bedrock of Finland, in a time span ranging from c. 3000 Ma (the oldest granitoids) to 1600 Ma (large rapakivi bodies), there are many different types of ore provinces, industrial mineral occurrences and useful rock materials.
Several Palaeoproterozoic ore provinces
The ophiolite-related ores of the Outokumpu region, chromite ores associated with 2440 Ma old layered intrusions, massive sulphide ores in the Ladoga -Bay of Bothnia zone, Ni-Cu ores associated with c. 1989 Ma old basic orogenic intrusions, etc. may be mentioned as examples.
Bedrock map of Finland during 1 : 1 million
The bedrock map 1 : 5 million has been prepared from the updated Bedrock map of Finland 1 : 1 million (see reference below). The contents of the
original map are much more detailed with respect to the division of lithology and stratigraphy, with special attention paid to the geological evolution of Finnish bedrock and topographic and tectonic palaeoenvironments in different times.
The accessibility is excellent almost everywhere in Finland owing to a high quality road and railway network, and to fiat topography. The few places higher than 500 m are situated in northern Finland.
Reference: Suomen kallioperäkartta - Berggrundskarta över Finland -Bedrock map of Finland 1: 1 000 000. Korsman, K., Koistinen, T., Kohonen, J., Wennerström; M, Ekdahl, E., Honkamo, M, Idman, H. & Pekkala, Y. (editors) 1997. Geological Survey of Finland, Espoo, FINLAND. ISBN 951-690-691-5.
Bedrock Map of Finland 1 : 1
000 000 (JPG, 8 Mb)