Chrono- and lithostratigraphy of a Mesozoic–Tertiary fore- to intra-arc basin: Adelaide Island, Antarctic Peninsula

• Published in: Geological Magazine
• Main Authors: Riley, Teal R., Flowerdew, Michael J., Whitehouse, Martin J.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2012
• Subjects: Earth Sciences; Antarctic; The Antarctic; Antarctic Peninsula; Alexander Island; Adelaide Island; Buttress; Fossil Bluff; Himalia Ridge; Reptile Ridge; Pluto Glacier; Bond Nunatak; Buchia Buttress; Liotard; Milestone Bluff; Mount Liotard; Antarc*
• Online Access: http://nora.nerc.ac.uk/id/eprint/19567/; https://nora.nerc.ac.uk/id/eprint/19567/1/displayFulltext.pdf; http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=8647543&fulltextType=RA&fileId=S0016756811001002

The Mesozoic fore-arc of the Antarctic Peninsula is exposed along its west coast. On Adelaide Island, a 2–3 km succession of turbiditic coarse sandstones and volcanic rocks is exposed. Four U–Pb (zircon) ages are presented here that, in combination with a new stratigraphy, have permitted a robust chrono- and lithostratigraphy to be constructed, which in turn has allowed tentative correlations to be made with the Fossil Bluff Group of Alexander Island, where the ‘type’ fore-arc sequences are described. The lithostratigraphy of Adelaide Island includes the definition of five volcanic/sedimentary formations. The oldest formation is the Buchia Buttress Formation (149.5 ± 1.6 Ma) and is correlated with the Himalia Ridge Formation of Alexander Island. The sandstone–conglomerate dominated succession of the Milestone Bluff Formation (113.9 ± 1.2 Ma) is tentatively correlated with the Pluto Glacier Formation of Alexander Island. Three dominantly volcanic formations are recognized on Adelaide Island, akin to the volcanic rocks of the Alexander Island Volcanic Group; the Mount Liotard Formation is formed of 2 km of basaltic andesite lavas, whilst the Bond Nunatak Formation is also dominated by basaltic andesite lavas, but interbedded with volcaniclastic rocks. The Reptile Ridge Formation has been dated at 67.6 ± 0.7 Ma and is characterized by hydrothermally altered rhyolitic crystal-lithic tuffs. Tentative correlations between Adelaide Island and Alexander Island preclude the two areas forming part of distinct terranes as has been suggested previously, and a proximal source for volcaniclastic sediments also indicates an exotic terrane origin is unlikely.