Avalonia, Armorica, Perunica: terranes, microcontinents, microplates or palaeobiogeographical provinces?
Thomas Servais, Manuel Sintubin, 2009. "Avalonia, Armorica, Perunica: terranes, microcontinents, microplates or palaeobiogeographical provinces?", Early Palaeozoic Peri-Gondwana Terranes: New Insights from Tectonics and Biogeography, M. G. Bassett
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In recent decades various research studies have focused on the reconstruction of Palaeozoic Europe, reflecting the complex geodynamic history related to the formation of the supercontinent Pangaea. It has been demonstrated that Palaeozoic Europe comprises a series of tectonostratigraphical units, or ‘terranes’, located between the remnants of three major palaeocontinents, Gondwana, Laurentia and Baltica. Some of these ‘terranes’ have been referred to as ‘microcontinents’, a typical (palaeo-)geographical term, and as ‘microplates’, a typical plate-tectonic term, giving rise to misunderstandings and a continuing scientific debate. This confusion is based primarily on an inconsistent use of different palaeogeographical terms by specialists from different scientific disciplines. Whereas large palaeocontinents such as Baltica and Siberia have been named as terranes by some workers, several peri-Gondwanan ‘terranes’ have been attributed to microcontinents or microplates, without conclusive reasoning. This paper is a critical review of the terminology used for three European peri-Gondwanan palaeogeographical entities: ‘Avalonia’, ‘Armorica’ and ‘Perunica’. The review indicates that only Avalonia should be considered as a separate (micro-)continent on a separate (micro-)plate. Armorica has many different definitions and is commonly considered to be composed of several terranes. It is, however, not at all evident if Armorica was a separate (micro-)continent and/or an independent (micro-)plate. For Perunica, defined originally as a separate microplate, current evidence demonstrates that it can probably be considered only as a palaeobiogeographical province.
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Following the late Neoproterozoic – early Cambrian breakup of the supercontinent Rodinia, Gondwana evolved as one of the principal continental masses on Earth, embracing most of South America, Africa, Australasia, Antarctica, much of western Europe and parts of Asia. Around its margins were various other terranes that had varying tectonic and biogeographical affinities with the main continental block. This book incorporates a series of reviews and multidisciplinary research papers that together explore the tectonic, palaeogeographical and palaeobiogeographical evolution of the elements that made up the peri-Gondwanan collage. The stratigraphical scope of the coverage embraces the late Precambrian through early Devonian, providing a comprehensive overview of structural, stratigraphical and biological evolution through this significant interval of Earth history. Integration of these various processes throughout the volume will be of broad-based interest to a wide range of geoscientists.