Abstract

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 terranes can be defined in this part of the Svecokarelian orogen: the older cratonic Kuhmo and Iisalmi terranes, the hybrid Lapland and Savo province allochthonous terranes, the juvenile island-arc-like Skellefte-Savonlinna and south Finland-central Sweden terranes, the back-arc or arc-like Outokumpu nappe, and the ophiolitic (oceanic?) Jormua nappe. Stitching events can also be recognized. These include the ca. 1.88-1.87 Ga Svionian magmatic arc, the ca. 2.44 Go Koillismaa intrusions, the Kalevian flysch basin, and the Bothnian basin. Constraining the age of these stitching events permits the construction of an accretion history in which the "Svecokarelian orogeny" can be resolved as a number of accretion events, deformation episodes related to accretion or magmato-tectonic episodes. These events, defined here, include the pre-2.44 Go Pohjolan accretion of the component parts of the Lapland hybrid terrane, the ca. 1.95 Ga Kyllikian accretion of the Karelian collage, the ca. 1.90 Ga Karelian orogeny marked by the development of the Savo thrust belt in response to the accretion of the Skellefte-Savonlinna terrane to the Karelian collage, and the ca. 1.88-1.87 Ga Svionian magmatic arc. The whole Svecokarelian collage had assembled by ca. 1.85 Ga, an amalgamation succeeded and stitched by a diverse collection of igneous and thermal events through the period 1.85-1.75 Ga.

First Page Preview

First page PDF preview
You do not currently have access to this article.