The provenance and setting of the Mesoproterozoic Dala Sandstone, western Sweden, and paleogeographic implications for southwestern Fennoscandia

• Zircon SIMS provenance data on the Jotnian Dala Sandstone, Sweden, are presented.
• A <1.58 Ga maximum deposition age supports link to the Hallandian-Danopolonian event.
• Detritus derive from adjacent basement, and the Gothian orogen to the south-west.
• Few zircons from immediate basement support a sag basin, not a faultbounded rift.
• The new data constrain the Mesoproterozoic paleogeography of SW Fennoscandia.

The Mesoproterozoic (Jotnian) Dala Sandstone, western Sweden, is investigated using zircon U-Pb SIMS. The Dala Sandstone was deposited in a gentle sag basin and underwent post-depositional downfaulting and local deformation along the Sveconorwegian Frontal Deformation Zone. The maximum depositional age is lowered to 1.58 Ga, lending support to a suggested 1.5 Ga maximum age from regional basement age considerations. Associated 1.46 Ga volcanism (Öje basalt) indicates that the 1.5–1.4 Ga Hallandian-Danopolonian event triggered basin formation; in addition, repeated local magmatism and deformation over several 100 m.y. hint at the presence of a crustal weak zone. Provenance data indicate sediment sources in surrounding Svecofennian, Transscandinavian Igneous Belt and Gothian domains; age peaks coinciding with early Gothian phases suggest that older inboard parts of the orogen shielded the Dala region from the younger outboard parts. Decreasing input from the Gothian orogen after 1.46 Ga suggests changing regional drainage patterns. Archaean/Paleoproterozoic zircon in pre-Sveconorwegian sediments in southern Norway is proposed to reflect sediment routing from the north, or significant sinistral Sveconorwegian displacement of southern Norway along the Fennoscandian margin. The latter would potentially juxtapose the Dala basin and the Rjukan rift in southern Norway, however, these formed two distinct and separate basins.