Fig. 4: Geophysical data, modelling and interpretation.
a Airy isostatic gravity anomaly from data compilation. Grey line shows modelled flight line. Pale shading marks ice shelves where the gravity corrections for topography/bathymetry are considered less robust. Approximate interpreted geological boundaries include: Previously interpreted Cretaceous mafic intrusive body (solid green line) and un-dated subglacial granite (solid pink line)2. From this study a 3–8 Ma mafic body (blue), southern edge of 3–8 Ma subglacial volcanics (V pattern and white line), northward extension of ~175 Ma granite (pink/white dashed line), and extent of Sif Island granite (pink/black dashed line). b Total field magnetic anomaly continued to an altitude of 2500 m. Boundaries same as (a). c Ice velocity along modelled N to S profile located in (a, b). d Profile magnetic anomalies. Observed data continued to an altitude of 2000 m and modelled assuming the same observation altitude. e Airy isostatic gravity anomaly. Blue line is profile data from 2004 continued to 2000 m. Yellow line is the gravity anomaly sampled from the compilation created for this study, dominated by more recent data. Black line shows modelled gravity anomaly at 2000 m observation altitude. f Joint upper crustal model. Note coloured bodies have density and susceptibility distinct from background values. Grey bodies only have susceptibility variations. Interpreted lithologies include: volcanics (V1-4), mafic Intrusive rocks (M. Int 1 and 2), and granites (H. Hudson Mountains, PIG Pine Island Glacier). BG indicates background. Modelled density and susceptibility values in Table 2.
