Paleomagnetic and geochemical studies of the Mesoproterozoic Satakunta dyke swarms, Finland, with implications for a Northern Europe – North America (NENA) connection within Nuna supercontinent

•A new high quality Subjotnian paleomagnetic data for Baltica is defined.•The proposed NENA configuration is valid during the 1.8 and 1.2 Ga.•Pb-isotope geochemistry defines two different Subjotnian dyke swarms in Satakunta area in Finland.

The existence of the Paleoproterozoic supercontinent Nuna (Columbia, Hudsonland) has been proposed by several authors. Many recent reconstructions of this supercontinent are based on the assumption that Baltica and Laurentia form part of its core in a Northern Europe – North America (NENA) configuration. The E–W, N–S and NE–SW trending Early Mesoproterozoic diabase dyke swarms in Satakunta, SW Finland, provide new paleomagnetic data to test the NENA configuration. A high-inclination, secondary remanence component carried by maghemite was isolated from some sites, and is interpreted to record hydrothermal alteration during the initial Mesozoic breakup of Pangea. A dual-polarity, high-stability remanence component was found in about half of the studied sites, and confirmed to be primary by several positive baked-contact tests. A suite of rock-magnetic analyses demonstrates that pseudo-single domain magnetite is the remanence carrier. The combined mean direction for N–S (1565 Ma; Lehtonen et al., 2003) and NE–SW trending dykes, showing both polarities, is D = 11.5°, I = 3.3° (α95 = 8.8°), yielding a key paleomagnetic pole (SK1) for Baltica at 29.3° N, 188.1° E (A95 = 6.6°). It fulfills the first six of seven Van der Voo's (1990) reliability criteria for paleomagnetic poles. The new Satakunta SK1 pole, when compared to the nearly coeval Western Channel Diabase pole (1590 ± 4 Ma) from Laurentia, allows the NENA fit at 1.57–1.59 Ga. Based on geological evidence E–W dykes have been proposed to belong a swarm that is ca. 100 million years older than the N–S dykes. E–W trending dykes show a dual polarity direction of D = 356.9°, I = 8.3° (α95 = 15.9°), yielding a paleomagnetic pole (SK2) for Baltica at 32.6° N, 205.5° E (A95 = 14.3°). Based on coeval paleomagnetic data and correlations of geochronology and basement geology of Baltica and Laurentia, the NENA fit is validated at 1.77–1.75 Ga, 1.59–1.57 Ga, 1.46 Ga, and 1.27 Ga, and by comparing single virtual geomagnetic poles at 1.63 Ga. However, the mean 1.63 Ga data from Laurentia (Melville Bugt dykes, Greenland; Halls et al., 2011) and Baltica (Sipoo dykes, Finland) are offset by about 30°. Validation of NENA for both older and younger times suggests to us that a variety of factors, such as less than highest-quality or not coeval paleomagnetic data, possible unrecognized tilting of the continental blocks, or a non-symmetric geomagnetic field, other than cratonic reconstruction, can explain the minor 1.63 Ga mean pole discordance.