Technical procedures for aeromagnetic surveys in Antarctica during the Italian expeditions (1988-1992)

Abstract

For most of Antarctica, the geophysical data now available are those of aeromagnetic surveys performed there from 1950 to 1960. Until 1984, the inaccurate positioning and insufficient monitoring of geomagnetic time variations allowed the investigation of the geomagnetic residual field only along profiles. The Ganovex IV aeromagnetic survey, performed by BGR-USGS over the Ross Sea and the Northern Victoria Land, and the geophysical investigations of BAS on the Southern Antarctic peninsula and the Ronne ice shelf region corresponds to the recent advancement of these techniques in Antarctica. The first experiments of aeromagnetic measurements, during the Italian expeditions in Antarctica were made during the 1988-1989 field season. Some geomagnetic helicopter borne profiles were accomplished with a Proton Precession Magnetometer (PPM) in the Terra Nova Bay-Gerlache Inlet area. In the 1989-1990 ItaliAntartide expedition some profiles were flown over the suture between the Wilson and Bower terranes, in Northern Victoria Land. During the 1991-1992 expedition, in cooperation with researchers of BGR (Bundesanstalt fur Geowissenschaften und Rohstoffe) of Hannover, the GITARA I (German ITalian Aeromagnetic Rescarch Antarctica) program, as part of the LIRA (Litospheric Investigation in the Ross Sea Area) project, was carried out. The investigated area lies between the latitudes 74°18' S and 75°18' S and the longitudes 160°30' E and 164°30'E and it corresponds to a portion of the North Victoria Land, located between the Eisenhower Range and the, DrygaIski Ice Tongue. The survey was made with a Cesium vapour magnetometer. The positioning system was of the “Range-Range” type, it consisted of three transmitters (beacons), installed inside the investigated area and located with GPS measurements. The line spacing was 4.4 km, with tie lines every 22 km. The survey covered an area of 6500 km2 . Four PPM base stations for the determination of the time variation corrections were installed. The aeromagnetic anomalies wilI allow the comparison with the ground geomagnetic surveys performed during the previous Antarctic expeditions, also in connection with the aeromagnetic maps of Ganovex IV, located at the northern and eastern boundaries of the GITARA area.