Caledonian orogeny Caledonian orogeny The Caledonian orogeny was a mountain-building era recorded in the northern parts of Ireland and Britain, the Scandinavian Mountains, Svalbard, eastern Greenland and parts of north-central Europe. The Caledonian orogeny encompasses events that occurred from the Ordovician to Early Devonian, roughly 490–390 million years ago (Ma). It was caused by the closure of the Iapetus Ocean when the continents and terranes of Laurentia, Baltica and Avalonia collided. The Caledonian orogeny is named for Caledonia, the Latin name for Scotland. The name was first used in 1885 by Austrian geologist Eduard Suess for an episode of mountain building in
Grenville orogeny of Laurentia, and likely collided with a different continent than that involved in the eastern collision. The Zapotecan Orogeny of Mexico is coeval with the later stages of the Grenville orogeny, and they are generally considered to be one and the same. Mesoproterozoic igneous protoliths (metamorphosed to granulite facies during the orogeny) fall into two age groups in Mexico; c. 1235–1115 Ma and c. 1035–1010 Ma. Rocks of the former group bear geochemical signatures implying island arc and back-arc basin provenance. The latter group represents AMCG magmatism. These AMCG rocks are somewhat anomalous throughout the Grenville orogen, there is no