The Cenozoic development of the Scotia Sea and opening of Drake Passage led to the dispersal of crustal blocks of the North and South Scotia ridges that today have a strong influence on the pathway of the Antarctic circumpolar current. The pre-translation positions of the crustal fragments of the Scotia ridges are uncertain, with correlations to both the Antarctic and South American plates. We present direct geochronology (40Ar/39Ar) from Bruce and Jane banks of the South Scotia Ridge that yield Late Cretaceous – Paleogene ages indicating a pre-translation magmatic history. Basaltic magmatism from Bruce Bank is calc-alkaline, akin to Cenozoic magmatism of the South Orkney microcontinent and the South Shetlands Islands, and in agreement with pre-translation tectonic models that place the crustal blocks of the South Scotia Ridge adjacent to the northern Antarctic Peninsula arc. The intra-oceanic arc magmatism at Jane Bank is Late Cretaceous in age (97.2 ± 1.1 Ma), and is not consistent with models suggesting a Miocene origin as part of the ancestral South Sandwich arc. The development of westward-directed subduction adjacent to Jane Bank is predicted in some tectonic models as a consequence of Late Cretaceous plate dynamics that developed prior to the Oligocene – Miocene ancestral arc.

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