Aeromagnetic anomaly map of West Antarctica (Weddell Sea sector) 1:2 500 000

This report describes the map, which has a 50 nT contour interval covering 1 980 000 km² of West Antarctica. The map has been compiled from the results of eight reconnaissance aeromagnetic surveys. Because of filtering, the map is restricted to showing the major regional anomalies, thus imaging gross crustal structure rather than local, shallow sources. The dominant feature of the map is the Pacific Margin Anomaly (PMA) which extends without a break along the Pacific margin of the Antarctic Peninsula and Ellsworth Land. A distinctive region of high amplitude (up to 1000 nT) anomalies, covering an area of around 100 000 km², surrounds Haag Nunataks. It suggests that Precambrian rocks exposed there extend beneath parts of the Ellsworth Mountains, Ronne Ice Shelf and Siple trough. The Ronne Ice Shelf is characterized by long wavelength (200 km), 100-200 nT anomalies that cover an area of almost 600 km × 600km and represent a deep sedimentary basin. Berkner Island has a large 400 nT anomaly caused by considerably shallower magnetic basement. Quiet magnetic conditions characterize the southern part of the map, with local anomalies caused by plutons associated with continental fragmentation. -after Authors