Magnetotelluric Study in James Ross Island, Antarctic Peninsula

Abstract

Three MT soundings were carried out on the James Ross island, next to the Antarctic Peninsula (Trinity Peninsula) during the Antarctic Summer campaign 1991–1992. The region is at about 150 km in the SE direction from a rift (Bransfield strait). The sounding sites are almost free of glacier cover. The James Ross island had volcanic origin during the Pliocene period. The equipment used for these soundings was battery powered, using Cu-CuSO4 electrodes, induction coils and a Flux-gate magnetometer. The results of the MT soundings show that the region of Seymour and James Ross islands is affected by the above mentioned rift. From Seymour island, the permafrost becomes thinner and the sub-permafrost has more conductance, while the James Ross island and the Antarctic Peninsula is approached, suggesting a possible increase of geothermic gradient and heat flow from Seymour to James Ross island. MT soundings also suggest the presence of an intercalated conductive layer at 55–60 km depth, probably in the Upper Mantle, cosindering the possible lithospheric attenuation produced by the rift. This conductive layer could be the asthenosphere. However, the scarce information obtained over 1000 sec of period do not permit to assure its presence.