Tom A. Jordan1, F. Ferraccioli1, P.C. Jones1, J.L. Smellie1, M. Ghidella2, H. Corr1, and A.F. Zakrajsek3. (1) Geological Sciences Division, British Antarctic Survey, High Cross, Madingley Road, Cambridge, CB3 0ET, United Kingdom, (2) VNIIOkeangeologia, St. Petersburg, Russia, (3) Instituto Antartico Argentino, Cerrito 1248, 1010 Buenos Aires, Argentina
James Ross Island (JRI) exposes a Miocene-Recent alkaline basaltic volcanic complex that developed in a back-arc region, east of the northern Antarctic Peninsula. JRI has been the focus of several recent geological studies because it provides a window on Neogene magmatic processes and paleoenvironments. However, little is known about the internal structure of JRI. Our study presents new airborne gravity data collected as part of the first high-resolution aerogeophysical survey flown over the island. The data unexpectedly revealed a prominent negative Bouguer gravity anomaly over Mt Haddington. This is intriguing as basaltic volcanoes are typically associated with positive Bouguer anomalies, linked to mafic intrusions beneath them. The negative Bouguer anomaly over JRI may be associated with a hitherto unrecognised low-density sub-surface body, such as a breccia-filled subglacial caldera, or even a partially molten magma chamber.
[Manuscript]
