Geophysical models of Drake passage and Bransfield strait crustal structure

Abstract

The 2004 (9th) and 2006 (11th) Ukrainian Antarctic expeditions acquired new geoelectrical data (‘short-impulse electromagnetic field formation’ – FSPEF, and ‘vertical electric-resonance sounding’ – VERS) along profiles across Drake Passage and along Bransfield Strait, Antarctic Peninsula, with the aim of studying the crustal structure of these features down to depths of >30 km. The electromagnetic experiments yielded new data set with unique information about the inner structure of Drake Passage and West Antarctica crust. New values of Moho discontinuity for these structures were obtained. Results of geophysical researches allow investigating the deep structure of the earth's crust in the region where mantle diapirs have introduced to the ancient continental complexes of Bransfield Strait. Beneath the Drake Passage, Moho is interpreted at extremely shallow depths of 8–12 km; the origin of a deeper anomalous layer at 14–20 km is unknown at this stage. Both Moho and the deeper layer show strong relief in the vicinity of the Shackleton Fracture Zone. Moho in the Bransfield Strait profile is interpreted at depths of 12–28 km, while the lower crustal layers and crust–mantle transition zone show radical variations in depth and thickness. Geoelectrical data confirm possible crustal extension and existence of mantle material at depth of 12-16 km. Similar results obtained by three different methods (gravity and magnetic surveys, vertical electric-resonance sounding) during Ukrainian Antarctic expeditions in 2004-2006 years assure the notable magmatic dynamism of Bransfield Trough that forms in the conditions of structural transformations and rifting processes migrating NE-SW along Bransfield Strait.