Autochthonous vs. accreted terrane development of continental margins: a revised in situ tectonic history of the Antarctic Peninsula

The allochthonous terrane accretion model previously proposed for the geological development of the Antarctic Peninsula continental margin arc is reviewed in light of recent data and the geology is reinterpreted as having evolved as an in situ continental arc. This is based upon the following factors: (1) the presence of Early Palaeozoic basement and stratigraphic correlation of sequences between the autochthonous and previously proposed allochthonous terranes; (2) isotopic evidence for similar deep crustal structure across the different terranes; (3) ocean island basalt magmas and deep marine sedimentary rocks formed during continental margin extension within the previously proposed accretionary wedge sequence (i.e. not formed against an active oceanic arc); (4) the distribution of magnetic susceptibility measurements and aeromagnetic data locating the palaeo-subduction zone along the west of the Peninsula; (5) a lack of clear palaeomagnetic distinction between the terranes. The following alternative tectonic history is proposed: (1) amalgamation and persistence of Gondwana; (2) subsequent silicic large igneous province magmatism and extension; (3) development and history of Andean subduction until its cessation in the Cenozoic. A number of features in the Antarctic Peninsula correlate with those of other circum-Pacific margins, supporting a global evaluation of allochthonous v. autochthonous margin development to aid our understanding of crustal growth mechanisms.

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