Discovery of Cenozoic magmatic ridges and tectonics off northern Victoria Land provides new insights into the geodynamics of the Antarctic margin.

The remote Pacific side of northern Victoria Land (NVL) lies at the boundary between East and West Antarctica and represents the area where the final continental breakup between the Antarctic and Australian conjugate margins occurred, leading to the opening of the Tasman Gateway since the Eocene-Oligocene boundary. Understanding the tectonic evolution of this area is crucial for the geodynamics of the Australian-Antarctic separation and the formation of the independent Antarctic plate in the Late Mesozoic-Cenozoic. This study, based on new multibeam data and multichannel seismic profiles combined with aeromagnetic data, presents an updated picture of the structural architecture of the NVL offshore area. The main novelties of this picture include the discovery of two large active submarine magmatic ridges in the southern sector and an isolated rifted crustal block in the north. The tectonic interpretation supports a NW-oriented, intraplate right-lateral megashear zone with associated magmatism that was active in the Pliocene-Quaternary and was accompanied by thinning of the continental crust. This deformation zone likely represents the intraplate continuation of the Balleny Fracture Zone off NVL and developed along the previous transform plate boundary between the Antarctic and Australian margins, characterized by left-lateral kinematics in the late Eocene-early Oligocene.