The geology of Åland includes Jotnian age sediments from the Proterozoic, such as sandstone, siltstone, arkose, conglomerate, rapakivi granite and shale.
[1][2] The rapakivi granite on Åland was formed during the Archaean around 1640–1540 Mya by anorogenic tectonic settings.
Jotnian sediments are usually assigned to the Riphean Stage of the Mesoproterozoic Era.
Baltica formed at c. 2000–1700 Mya by the collision of three Archaean-Proterozoic continental blocks: Fennoscandia (including the exposed Baltic Shield), Sarmatia (Ukrainian Shield and Voronezh Massif), and Volgo-Uralia (covered by younger deposits).
Between Pleistocene sediments and crushed rapakivi granite bedrock there is a layer of Paleozoic limestones.