Abstract

Previous views based on the paleomagnetic history of Baltica compared with that of Laurentia indicate a period of independent movement between ∼1200 and 950 Ma, during which Baltica appears to have rotated ∼80° clockwise relative to Laurentia; at ∼950 Ma, there was a rapid reversal from southward to northward motion. Movement directions on major shear zones in the 1100-1000 Ma Sveconorwegian belt of Baltica indicate oblique sinistral convergence during the main Sveconorwegian collision event, whereas shear zones in the Grenville belt indicate convergence orthogonal to the belt. A model for the drift history of Baltica suggests that the ∼80° rotation away from Laurentia at ∼1200 Ma was followed by collision ∼1050 Ma with a third continent (South America?) that may have already docked with Laurentia along the main Grenville suture. Subsequent movement of Baltica toward Laurentia ended with docking along the northern Britain and eastern Greenland margin at ∼1000 Ma. At ∼950 Ma, sinistral transform motion took place along the Laurentian margin and may have been responsible for early (pre-750 Ma) orogen-parallel movement directions in the Caledonides of Scotland and Norway, linked with a regional thermal event producing widespread granites and pegmatites at 800-750 Ma.

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