U-Pb baddeleyite age for the Ottfjället Dyke Swarm, central Scandinavian Caledonides: new constraints on Ediacaran opening of the Iapetus Ocean and glaciations on Baltica

The Ottfjället Dyke Swarm (ODS) is a prominent component of the Ediacaran mafic magmatism associated with opening Iapetus ocean, and hosted in Särv Nappe, Middle Allochthon Scandinavian Caledonides. A U-Pb baddeleyite age 596.3 ± 1.5 Ma for thick, well preserved, plagioclase-phyric dolerite dyke Härjedalen, Sweden, dates emplacement swarm. represents robust, inheritance-free reference variably deformed metamorphosed tholeiitic dykes sandstone-dominated sequences lower part Allochthon, representing proximal, rifted Baltoscandian margin preceding Iapetus. new within narrow time span between 610 595 defined by most reliable estimates structurally higher nappes (upper Allochthon), distal during cuts Tossåsfjället Group succession, which includes sabkha-related carbonate platform diamictite couples, one several correlated Neoproterozoic glaciogenic successions Scandinavia. intrusion ca. 596 therefore sets minimum successions. It implies that glaciations Scandinavia predate 580 Gaskiers glaciation event are probably 635 Marinoan “Snowball-Earth”-type glaciation.