Citadel Bastion
Citadel Bastion (72°0′S 68°32′W / 72.000°S 68.533°WCoordinates: 72°0′S 68°32′W / 72.000°S 68.533°W) is a rocky, flat-topped, rocky elevation at the south side of the terminus of Saturn Glacier, facing towards George VI Sound and the Rymill Coast, situated on the east side of Alexander Island, Antarctica. Its maximum elevation is about 645 m. Citadel Bastion lies next to Hodgson Lake. This mountain was mapped from trimetrogon air photography taken by the Ronne Antarctic Research Expedition, 1947–48, and from survey by the Falkland Islands Dependencies Survey, 1948–50. The name applied by the UK Antarctic Place-Names Committee because it resembles a fortified structure with a watchtower at the end of a wall.
Citadel Bastion is one of a series of nunataks that provide outcrops of Cretaceous (Aptian–Albian) sedimentary rocks that comprise part of the 6.8 kilometer-thick Fossil Bluff Group, which underlies easternmost Alexander Island. These sedimentary rocks accumulated in shallow marine and terrestrial environments. The sedimentary rocks, which are exposed in Citadel Bastion and adjacent nunataks, consist of a 700 meter-thick sequence of laterally persistent beds of very fine to very coarse, rarely gravelly interbedded with occasional beds of sandstone (volcanic lithic arenite), mudstone, and conglomerate. At two horizons within these strata, beds of lithic and vitric tuff occur. well developed paleosols, leaf fossils, fossil wood, and fossil forests are widespread within this unit. The plant fossils consists mainly of coniferous plants (mainly podocarps). Fossils of Bennettitales, pteridophytes and liverworts, and to a lesser extent the angiosperms, are also common. Citadel Bastion is notable for bedrock outcrops that expose multiple fossil forests, which consist of upright standing trunks buried in place, and their associated paleosols.
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