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Banded meta-sedimentary rock with alternating sandy (light) and shaly (darker) layers on the island Fjärdlång in the southern archipelago of Stockholm. Photo: Åke Johansson.

Fennoscandian evolution and the position of Baltica in earlier supercontinents

An overarching theme for my research has been the formation and evolution of the Fennoscandian shield during the Proterozoic. For this purpose, U-Pb dating of different rocks is combined with geochemical and isotope studies in order to understand their origin and tectonic setting.

A related question is how the geological evolution of Fennoscandia and Baltica (the northeastern, Precambrian part of Europe) fits into the larger plate tectonic pattern of earlier supercontinents (Columbia/Nuna, Rodinia).

Forskningsområden: Geovetenskap

Forskningsämnen: Geologiska och förhistoriska händelser

Project overview

Project period: 2001 – Ongoing

Participating departments from the museum: Department of Geosciences, GEO

Since around the year 2000 my research has been focused on the Precambrian bedrock of southern and central Sweden, with a subdivision on several subprojects, and an overarching goal of clarifying the age relations among the different rock units and understand their origin, using the isotope geochemical methods that are available at the Department of Geosciences at the Swedish Museum of Natural History. Some of these studies have also dealt with the concealed Precambrian crust in Poland and Lithuania, in cooperation with geologists from those countries. A wider goal is to find what place our part of the world, Fennoscandia and Baltica (northeast Europe), has had in the global plate tectonic puzzle of continents and supercontinents in Precambrian time. While most of the subprojects listed below have been finished and reported, research is still ongoing concerning the bedrock in the southern Stockholm archipelago.

Project description

Two of the more recent subprojects that have been finished and published concerned the Hedesunda granite massif on the border between Uppland and Gästrikland and the mafic Herräng dykes in Roslagen, both in east-central Sweden. The latter one was a continuation of similar studies of other Svecofennian mafic intrusive rocks in the same area in east-central Sweden (The Roslagen gabbros, Mafic intrusives of the Avesta-Östhammar belt, Mafic dykes in the Dannemora mine area), giving information on the tectonic environment in the area when these rocks formed some 1900 to 1850 million years ago, as well as information about the composition of the underlying mantle at that time.

Under the heading "Cleaning up the record", I redid some of my own earlier U-Pb age determinations from southern Sweden with new and improved techniques (ion microprobe), leading to revision of earlier ages. Previous, now finished projects have dealt with the bedrock in Blekinge in southeastern Sweden and the Danish island of Bornholm in the southern Baltic Sea, as well as the timing of metamorphism and migmatization in east-central Sweden.

In addition, I have studied rocks in drill cores penetrating the Precambrian basement beneath the younger sedimentary cover in Poland and Lithuania, in cooperation with geologists from those countries, in order to understand how this concealed Precambrian crust is connected to its exposed counterparts in southeastern Sweden.

My current project deals with the bedrock in the southern Stockholm archipelago, more specifically at Ornöhuvud and Fjärdlång and adjacent islands and skerries, in cooperation with Andreas Karlsson and Stefan Claesson from the Swedish Museum of Natural History and Karin Högdahl from Uppsala University.

When it comes to reconstructing former Precambrian supercontinents, I have written about the possible relationship of Baltica with Amazonia and West Africa during the Proterozoic (so called SAMBA model) in several publications, both on my own and in cooperation with multiple other geologists from different countries and continents.

Banded meta-sedimentary rock with alternating sandy (light) and shaly (darker) layers on the island Fjärdlång in the southern archipelago of Stockholm. Photo: Åke Johansson.


Selected publications

Plate tectonic reconstructions (SAMBA model)

  • Johansson, Å., 2009: Baltica, Amazonia and the SAMBA connection—1000 million years of neighbourhood during the Proterozoic? Precambrian Research 175, 221-234. External link.
  • Johansson, Å., 2011: När Sverige var granne med Amazonas. Geologiskt forum no. 72, p. 12-19.
  • Johansson, Å., 2014: From Rodinia to Gondwana with the ‘SAMBA’ model – A distant view from Baltica towards Amazonia and beyond. Precambrian Research 244, 226-235. External link.
  • Johansson, Å., Bingen, B., Huhma, H., Waight, T., Vestergaard, R., Soesoo, A., Skridlaite, G., Krzeminska, E., Shumlyanskyy, L., Holland, M.E., Holm-Denoma, C., Teixeira, W., Faleiros, F.M., Ribeiro, B.V., Jacobs, J., Wang, C.-C., Thomas, R.B., Macey, P.M., Kirkland, C.L., Hartnady, M.I.H., Eglington, B.M., Puetz, S.J., Condie, K.C., 2022: A geochronological review of magmatism along the external margin of Columbia and in the Grenville-age orogens forming the core of Rodinia. Precambrian Research 371, 106463, 43 pp. External link..

Project manager

Åke Johansson | Associated researcher

Project members

Only for the current subproject in the Stockholm archipelago, not for earlier subprojects.

Andreas Karlsson | Curator

Manager SEM and Raman spectroscope

Stefan Claesson | Professor emeritus

External participants

Resarch Areas: Geosciences

Research Subjects: Historical and Geological Events, Isotopes

Page manager: Andreas Karlsson