Continental growth by accretion: A tectonostratigraphic terrane analysis of the evolution of the western and central Baltic Shield

Tectonostratigraphic terrane analysis of the western and central Baltic Shield defines a framework for continental growth through the period 2.50-1,75 Ga, Eight discrete terrenes can he defined in this part of the Svecokarelian orogen: the older cratonic Kuhmo and HsaJmi terranes, the hybrid Lapland and Savo province allochthonous ler-ranes, the juvenile island-arc-I ike Skeltefte-Savonlinna and south Finland-central Sweden terranes. (he back-arc or arc-tike Outokumpu nappe, and the ophiolitic (oceanic?) Jormua nappe. Stitching events can also he recngnized. These include the ca- 1.88-1.87 Ca Svionian magmalic arc, the ca. 2.44 Ca Koillismaa intrusions, the Kalevian flysch basin, and the Bolhnian basin. Constraining the age of these stitching events permits the construction of an accretion history in which the "Svecok3relian orogeny" can be resolved as a number of accretion events, deformation episodes related to accretion or mjgmato-tectonic episodes. These events, defined here, include the pre-2.44 Ca Pohjolan accretion of the component parts of the Lapland hybrid terrane. the ca. 1.95 Ca Kyllikian accretion of the Karelian collage, Ihc ca. 1.90 Ga Karelian orogeny marked by the development of the Savo thrust bell in response to the accretion of the Skellefte-Savonlinna terrane to the Karelian collage, and (he ca. 1.88-1.87 Ga Svionian magmalic arc. The whole Svecokaretian collage had assembled by ca. 1.85 Ca, an amalgamation succeeded and stitched by a diverse collection of igneous and thermal events through the period 1.85-1.75 Ca.