Seismic imaging of the crust beneath Dronning Maud Land, East Antarctica

Abstract

SUMMARY With calculations of receiver functions and modelling of a seismic refraction profile we map the depth to the Moho discontinuity beneath Dronning Maud Land (DML), East Antarctica. The crustal converted signal (Ps) is clearly observable for all stations, suggesting that the crust is separated from the mantle by a sharp Moho. We reveal spatial variations in the crustal thickness and for some places the ratio of crustal P -t oS-wave velocity. The crust beneath station Novolazarevskaja in central DML approaches a thickness of about 42 km and is characterized by low V p/V s ratio of about 1.67. This crustal thickness agrees well with previous wide-angle experiments. Further south, the Wohlthat Massif shows thickened crust with depths to Moho between 47 and 51 km indicative of an orogenic root. At station Weigel in the Kottas Mountains in western DML we determine a Moho depth of 44 km using the Ps traveltime. This depth corresponds well with the crustal model retrieved from a seismic refraction experiment across the Kottas Mountains. Moho depths approach values between 44 and 52 km beneath the profile. Underneath the middle of the profile, a remarkable Moho offset of approximately 7 km is observed. It appears to mark a suture between the Mesoproterozoic (1.2–1.0 Ga) Maudheim Province and the Kibarian (1.1–1.0 Ga) arc-related Kottas Mountains. The crustal thicknesses of mobile belts and undeformed areas in southern Africa and DML are remarkably similar. For station SNAA, situated on the Archean Grunehogna Craton, a fragment of the Kalahari–Kaapvaal–Craton, we obtained an ambiguous result that indicates a complex crustal structure. We determined a crustal thickness underneath SNAA of 39 km and a V p/V s ratio of 1.82. The latter higher value corresponds to a gabbroic crust, which was also deduced by former rock investigations. In addition, the presence of Jurassic basaltic intrusions into the predominantly gabbroic crust may contribute to the value.