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Metamorphic Basement, Eastern Graham Land

Description1

Amphibolite-grade orthogneisses, metabasites (amphibolites), migmatites and paragneisses resulting from Ordovician, Permian and Triassic metamorphism of Ordovician and younger protoliths in southern and eastern Graham Land23. One small, irregular locality (the c.10 km long Target Hill) in eastern Graham Land records Carboniferous metamorphism of a Devonian igneous protolith with no evidence for later metamorphism24, despite being < 15 km from similar outcrops that do. This may be related to the Carboniferous metamorphism of the Deseado Massif in Patagonia5 and is often viewed as the ‘classic’ locality for the Peninsula’s basement6, although it is clearly anomalous and misrepresentative.

Age

Middle Cretaceous

Map Reference

Riley, T. R., Flowerdew, M. J. & Haselwimmer, C. E. Geological Map of Eastern Graham Land, Antarctic Peninsula (1:625 000 scale). Sheet 1, (British Antarctic Survey, 2011). Available here.

References

  1. Burton-Johnson, A. & Riley, T. R. Autochthonous v. accreted terrane development of continental margins: a revised in situ tectonic history of the Antarctic Peninsula. J. Geol. Soc. 2014–110 (2015). ↩

  2. Riley, T. R., Flowerdew, M. J. & Whitehouse, M. J. U-Pb ion-microprobe zircon geochronology from the basement inliers of eastern Graham Land, Antarctic Peninsula. J. Geol. Soc. 169, 381–393 (2012). ↩ ↩2

  3. Wendt, A. S., Vaughan, A. P. M. & Tate, A. Metamorphic rocks in the Antarctic Peninsula region. Geol. Mag. 145, 655–676 (2008). ↩

  4. Millar, I. L., Pankhurst, R. J. & Fanning, C. M. Basement chronology of the Antarctic Peninsula: recurrent magmatism and anatexis in the Palaeozoic Gondwana Margin. J. Geol. Soc. 159, 145–157 (2002). ↩

  5. Pankhurst, R. J., Rapela, C. W., Fanning, C. M. & Márquez, M. Gondwanide continental collision and the origin of Patagonia. Earth-Sci. Rev. 76, 235–257 (2006). ↩

  6. Milne, A. J. & Millar, I. L. Short paper: the significance of mid-palaeozoic basement in Graham Land, Antarctic Peninsula. J. Geol. Soc. 146, 207–210 (1989). ↩