Palaeomagnetism and U – Pb geochronology of c. 1570 Ma intrusives from Åland archipelago, SW Finland – implications for Nuna

Johanna M. Salminen, Robert Klein, Satu Mertanen, Lauri J. Pesonen, Sören Fröjdö, Irmeli Mänttäri, Olav Eklund

Research output: Contribution to journalArticleScientificpeer-review


We report new palaeomagnetic and isotope age data of Early Mesoproterozoic (i.e. Subjotnian) intrusions from the Åland archipelago, SW Finland. The palaeomagnetic results reveal dual-polarity magnetizations with a pronounced reversal asymmetry occurring in dykes. We explain the asymmetry by an unremoved secondary component, which is affecting more N-polarity dykes. Other explanations, such as the age difference of magnetization between normal and reversed polarity dykes, are discussed. The primary nature of magnetization in dykes for both normal (N) and reversed (R) groups is verified by positive baked contact tests. A dyke showing reversed polarity from Korsö is dated 1575.9±3.0 Ma (U–Pb) in this study. This and previous U–Pb data tighten the magmatic activity in Åland to 1580–1570 Ma. We combined new palaeomagnetic data with those from earlier studies to provide a new key-palaeomagnetic pole for Baltica. Our data positions Baltica on equatorial latitudes, supporting the NENA (North Europe–North America) connection between Baltica and Laurentia at 1.59–1.58 Ga. Palaeomagnetic data support that NENA was valid at 1.75, 1.58, 1.46, and 1.26 Ga, forming the core of Mesoproterozoic Nuna (a.k.a. Columbia) supercontinent.
Original languageUndefined/Unknown
Pages (from-to)
JournalGeological Society Special Publications
Publication statusPublished - 2015
MoE publication typeA1 Journal article-refereed

Cite this