Scotland–Finland Precambrian correlations

Abstract

Isotopic age determinations indicate the generally co-eval nature of major episodes of earth history shown by the Precambrian rocks of Scotland and Finland, viz. (1) the c. 2 800—2 600 m.y. Scourian and Presvecokarelidic episodes, (2) the c. 2 200 m.y. Inverian episode and the c. 2 300 m.y. episode in Finland, (3) the c. 2.1 b.y. deposition of the Loch Maree Group in Scotland and the Jatulian quartzite, Karelian schists and related geosynclinal deposits in Finland, and (4) the c. 1 975—1 700 m.y. Laxfordian and Svecokarelian episodes. The existence of spatially connected belts in Precambrian times is suggested by the correspondence in both the sequence of development and the orientations of structural elements resulting from polyphase deformation in the successively formed Precambrian orogenic belts. This matching of complex structural frameworks implies that, before the initiation of the British-Scandinavian Caledonides, the Baltic Shield extended westward to include northwestern Britain and the continental shelf of the eastern North Atlantic Ocean. The Caledonian belt would then have developed on a plate of continental crust, or between the separated parts of a rifted continental crustal segment.