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.
[1][2] 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.
[3][4] 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.
This alluvial fan built seaward along the edge of a Cretaceous volcanic arc into marine waters occupying a forearc basin.
The floodplains between channels were stable enough, despite periodic deposition of coarse and fine sediment during floods, to allow the formation of soils and development of forests.
Fossil plants found in these sedimentary rocks indicate that the palaeoclimate was warm and humid throughout the period of deposition despite their polar position.