Preliminary results of geological and geophysical surveys in the Ross Sea and in the Dumont d'Urville Sea, off Antarctica

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Geological and geophysical surveys in the Ross Sea and in the Dumont d'Urville Sea were carried out in the 1982-1983 Antarctic summer season. The presence of two large basins, namely the Eastern Basin lying to the east of the 180°meridian and the Central Basin trending north-south along 175°E, in the Ross Sea region was confirmed and the maximum sedimentary thickness in the two basins was estimated at approximately 6km. The six-fold seismic reflection profiles indicate seven depositional sequences, which consist mainly of deltaic sediments with admixed glacial sediments in the Eastern Basin. Similar sediments were deposited in a graben structure in the Central Basin. The seismic reflection and refraction data suggest the presence of sediments of pre-Late Oligocene age in the deeper parts of the two basins beneath the Ross Sea. Four strata in the basin of the Dumont d'Urville Sea are interpreted from reflection data. They were formed by seafloor-spreading associated with rifting between Wilkes Land and South Australia. Seismic refraction indicates a maximum sedimentary thickness in excess of 5km. The age of the acoustic basement may be older than Late Oligocene.
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