The Satakunta dyke swarms are a series of dyke swarm of Mesoproterozoic age in the Bothnian Sea and western and central Finland.
Satakunta-Ulvö dyke swarm
The dyke swarm has been though as a result of a failed rift in the Bothnian Sea that developed as part of an extensional tectonic setting within the supercontinent of Columbia. At various location dykes of the swarm cut across Jotnian sediments indicating a Postjotnian age for the dyke swarm. Viewed in a map the dyke swarm has the form of a 90-degrees fan radiating open to the east from a point in the Bothnian Sea.
References
Satakunta dyke swarms Wikipedia(Text) CC BY-SA