| Summary: | Tomographic analysis of seismic surface waves can map upper mantle structure under the Antarctic plate with reliability and fairly good detail, making the best use of the relatively limited dataset currently available. The large-scale features of Antarctic upper mantle agree with global views of Earth structure under oceans and continents. Low seismic velocities map the hot thermal anomaly under mid-ocean ridges down to approximately 150 km, stronger and wider under faster-spreading ridges. Cold continental roots show as seismically fast material under the older part of the continent (East), while the West Antarctic Rift System has a clearly slow wave signature. The seismically imaged lithosphere has variable thickness under the craton. It appears rather regular and about 220 km thick under Dronning Maud Land, but it deepens in the region stretching below Enderby Land, Gamburtsev Mountains, to Wilkes Land, where it reaches its maximum thickness, in excess of 250 km. This variability in lithospheric thickness is analogous to what has been found under other continents. The high velocity anomaly imaging cratonic roots appears to spread out, as a cool halo, off the passive continental margins, but terminates sharply towards the West Antarctic Rift System. The fast/slow contact runs under the Transantarctic Mountains and it is particularly sharp in the Ross Embayment, where seismically slow material, imaged down to 250 km, can be interpreted as the deep-seated hot anomaly related to a mantle plume. Research supported by Programma Nazionale di Ricerche in Antartide. Published reserved
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