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Terminology revision of AlKaPeCa and Mesomediterranean Microplate

06/02/2020 / Leave a comment

The use of terms strictly related to the original formulation of different models caused, in some cases, inaccuracies in the univocal identification of some main palaeogeographic elements.

Bouillin et al. (1986) introduced the acronym AlKaPeCa for a lithospherical block formed by Alboran-Kabylian-Peloritan-Calabrian Internal Zones, Alpine units. According to them the relationships between AlKaPeCa and the Maghrebian Flysch Basin  may be synthesized as follows:‘ the only possible oceanic zone known between Western Europe and Africa, at the Jurassic time, corresponds to the basement of the Flyschs which was located southward of AlKaPeCa’ .

 Many palaeogeographic interpretations of the Jurassic-Cretaceous evolution of the Betic, Maghrebian and Apennine Chains have been roughly grouped into two main general families: (1) Type A  models: they state the presence of a single oceanic area (i.e., the Tethys) located between the African and European Plates; (2) Type B  models: they consider the occurrence of two oceanic branches of the Tethys surrounding one or more microcontinents located between the African and European Plates. Both classes of models imply a different evolution during the Pangea breakup and during the Cretaceous-Cenozoic convergence. According to Type A  models the Pangea broke with a single oceanic branch located between Europe and Africa, meanwhile according to Type B  models the fragmentation was more complex leading to two oceanic branches with several microplates located between Europe and Africa.

Reproduction of some original figures from literature concerning Type B models (A to D boxes) showing some inappropriate use of terms. The figures presented show Type B models which use the term AlKaPeCa instead of Mesomediterranean Microplate (MM). (a). Palaeogeographic sketch map (at Jurassic times) and evolutionary cross sections from Late Jurassic to Middle Miocene (after Michard et al. 2002); (b). Evolutionary palaeogeographic cross sections from Eocene to Oligocene (after Viti et al. 2009); (c). Evolutionary palaeogeographic sketch maps from 55 to 45 My (after Schmid et al. 2017); (d). Palaeogeographic sketch map at Early Miocene times (after Leprêtre et al. 2018).

According to Guerrera et al. (2019)  the original meaning of AlKaPeCa should be reserved to indicate a detached piece of the European Margin while the Mesomediterranean Microplate  should be used exclusively for the independent microplate even though during the Maghrebian- Apennine orogeny these elements actually coincide to form the Internal Zones of these chains. For this reason, the use of this acronym is not appropriate for models which consider the occurrence of an independent microplate surrounded by different oceanic branches of the Tethys since Mesozoic. A more common name used in literature for this microplate is the Mesomediterranean Microplate.

Cite as: Guerrera, F., Martín-Martín, M., and Tramontana, M. (2019): Evolutionary geological models of the central-western peri-Mediterranean chains: a review. International Geology Reviews. 1-22. doi: 10.1080/00206814.2019.1706056