The Caledonian Orogeny redefined

Recent advances in our understanding of Palaeozoic tectonics, and in the pr ecise dating of tectonic events require exact definitions of terminology. T he Caledonian Orogeny is here redefined to include all the Cambrian, Ordovi cian, Silurian and Devonian tectonic events associated with the development and closure of those parts of the Iapetus Ocean, which were situated betwe en Laurentia (lo the NW) and Baltica and Avalonia (to the SE and east). We suggest that the term 'Caledonian Orogeny' be restricted in this geographic sense, but that (as in modern usage) it continues to encompass a series of tectonic, or orogenic, phases (related to are-are, arc-continent and conti nent-continent collisions as Iapetus was closing). Many of these phases hav e been named; these and many more unnamed events are defined as orogenic ph ases (local components) of the Caledonian Orogeny. Some of these phases wer e synchronous over long distances, whereas others were diachronous. The who le Caledonian Orogeny occupied a time interval of around 200 Ma. Thus the t erm Caledonian should not be used to indicate age.