Sveconorwegian and Caledonian foreland basins in the Baltic Shield revealed by fission-track thermochronology

Fission-track thermochronology has been applied to apatite, zircon and tita nite from various depths of the Baltic Shield. Burial due to Sveconorwegian (Grenville) and Caledonian foreland sedimentation is revealed. Titanite and zircon fission-track ages from surface samples (from eastern S weden) do not vary significantly and average similar to 850 Myr. It is sugg ested that Sveconorwegian sediments reached a thickness of at least 8 km in eastern Sweden. Exhumation of these sediments was succeeded by deposition of Lower Palaeozoic cover rocks. Apatite fission-track ages along a transec t from SW to NE across the shield, increase from similar to 300 Myr to simi lar to 900 Myr and yield the Phanerozoic history of subsidence and exhumati on. Apatite fission tracks, in the basement of the thickest parts of the fo reland basin, were totally annealed. These results suggest a > 600 km wide Caledonian foreland basin filled by Devonian sediments that were > 2.5 km t hick in southern and western Sweden, thinning to the east (in Finland).