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We present here the results of detailed mapping, lithofacies analysis and stratigraphy of the Neogene James RossIsland Volcanic Group (Antarctic Peninsula) in the Cerro Santa Marta area (northwest of James Ross Island), inorder to give constraints on the evolution of a glaciated volcanic island. Our field results included recognitionand interpretation of seventeen volcanic and glacial lithofacies, together with their vertical and lateral arrangements,supported by four new unspiked K?Ar ages. This allowed us to conclude that the construction of the volcanicpile in this area took place during two main eruptive stages (Eruptive Stages 1 and 2), separated from theCretaceous bedrock and fromeach other by two major glacial unconformities (U1 and U2). The U1 unconformityis related to Antarctic Peninsula Ice sheet expansion during the late Miocene (before 6.2 Ma) and deposition ofglacial lithofacies in a glaciomarine setting. Following this glacial advance, Eruptive Stage 1 (6.2?4.6 Ma) volcanismstarted with subaerial extrusion of lava flows froman unrecognized vent north of the study area,with eruptionslater fed from vent/s centered at Cerro Santa Marta volcano, where cinder cone deposits and a volcanicconduit/lava lake are preserved. These lava flows fed an extensive (N7 km long) hyaloclastite delta system thatwas probably emplaced in a shallowmarine environment. A second unconformity (U2)was related to expansionof a local ice cap, centered on James Ross Island, which truncated all the eruptive units of Eruptive Stage 1. Concomitantwith glacier advance, renewed volcanic activity (Eruptive Stage 2) started after 4.6 Ma and volcanicproducts were fed again by Cerro Santa Marta vents. We infer that glaciovolcanic eruptions occurred under amoderately thin (~300 m) glacier, in good agreement with previous estimates of paleo-ice thickness for theJames Ross Island area during the Pliocene.