Three main Upper Jurassic–Cretaceous tectono-stratigraphic units recognized in Palmer Land and Alexander Island are comparable with assemblages formed (1) in an ensialic volcanic arc (Upper Jurassic Volcanic Group), (2) in a forearc or intra-arc marine basin (Fossil Bluff Formation), and (3) in a back-arc marine basin (Crabeater Point sediments and Latady Formation), possibly representing a proto–Weddell Sea.

A sequence of intensely sheared, polyphasally deformed turbidites and pillow lava rocks of possible late Paleozoic or Triassic age, exposed along western Alexander Island, is tentatively interpreted as a trench assemblage accreted during an early stage of subduction.

There is a close correlation between these units and the approximately coeval island-arc-marginal basin system of the southern Andes and South Georgia.

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