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

Abstract

-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.

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

“…However, Target Hill is clearly anomalous as extensive Permian and Triassic metamorphism is recorded in both the Central and Eastern domains Riley et al 2012a) and Permian metamorphism has been noted further along the Gondwanan margin in South America and West Antarctica (Pankhurst et al 1998;Herve et al 2010), supporting an authochthonous origin for the proposed domains.…”

“…Units for the Western Domain are as follows. Sed: LeMay Group, Sinnemurian-Albian (Thomson & Tranter 1986;Holdsworth & Nell 1992); Fossil Bluff Group, KimmeridgianAlbian (Butterworth et al 1988);Adelaide Is., c. 150-113.9 Ma (Thomson 1972;Riley et al 2012a). Vol: Alexander Is., 157-152 Ma (Macdonald et al 1999), 80-46 Ma (McCarron 1997 and 2.5-0.5 Ma (Hole 1988); Adelaide Is., 76-39.2 Ma (Griffiths & Oglethorpe 1998;Riley et al 2012a);South Shetland Is., 135-22.6 Ma (Smellie et al 1998;Haase et al 2012) and 2.4-0.1 Ma (Pankhurst & Smellie 1983).…”

“…Vol: Alexander Is., 157-152 Ma (Macdonald et al 1999), 80-46 Ma (McCarron 1997 and 2.5-0.5 Ma (Hole 1988); Adelaide Is., 76-39.2 Ma (Griffiths & Oglethorpe 1998;Riley et al 2012a);South Shetland Is., 135-22.6 Ma (Smellie et al 1998;Haase et al 2012) and 2.4-0.1 Ma (Pankhurst & Smellie 1983). Int: Alexander Is., 75-56 Ma (McCarron 1997); Adelaide Is., 60-44 Ma (Pankhurst 1982;Griffiths & Oglethorpe 1998;Riley et al 2012a). Units for the Central Domain are as follows.…”

“…Vaughan & Storey (2000) interpreted the Western Domain as either a subduction-accretion complex to the Central Domain arc or a separate exotic crustal fragment sutured to the Central Domain. In the original terrane model (Vaughan & Storey 2000) Adelaide Island was included in the Central Domain but, because of stratigraphic correlations between the Adelaide Island sediments and the Fossil Bluff Group as well as correlation of the magmatic units of the two islands, Adelaide Island has been reassigned to the Western Domain (Riley et al 2012a;Vaughan et al 2012a). Vaughan & Storey (2000) correlated this domain with the Eastern Province of New Zealand, where Permian to Cretaceous igneous and sedimentary units are interpreted as allochthonous arc complexes accreted during plate convergence (Wandres & Bradshaw 2005).…”

“…The terrane accretion model interprets the sedimentary sequences along the Antarctic Peninsula to be assigned to different domains: (1) (Riley et al 2012a) and have shown their affinity to the Fossil Bluff Group of the Western Domain rather than their original inclusion in the Central Domain.…”