Interpretation of aeromagnetic data from the Ellsworth Mountains-Thiel Mountains ridge, West Antarctica

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Abstract
Over 12000 km of new aeromagnetic data, gathered during periods free from auroral disturbances, are presented for an area of 290 000 km 2 in West Antarctica, including the majority of the Ellsworth-Whitmore Mountain crustal block. Selection of an appropriate line spacing (20 km) and rigorous diurnal control allowed interpretation of isolated magnetic anomalies by two-dimensional modellìng. Anomalies of 50–500 nT amplitude extend for over 100 km, predominantly with an east-west orientation. They attain their greatest amplitudes over scattered exposures of Middle Jurassic granite, but the measured magnetizations of these rocks ( J 0.5 Am −1 ) beneath the granites. The intrusions probably form part of a widespread bimodal igneous suite created during early stages of continental fragmentation.