Seismic sequences of the Ross Sea continental margin (Antarctica)

Thick sedimentary sequences occur under the continental margin of the Ross Sea, Antarctica. MCS Lines collected in the Ross Sea since 1987 by OGS-Trieste, Italy and MAGE-Murmansk, Russia have been used to correlate the main unconformities and the major depositional patterns ranging in age from at least Late Oligocene to the present. The unconformity U5 has been identified as a continuous reflector from the eastern to north-western Ross Sea margin. Reflectors correlated with the U6, U5A, U4A, U4, U3, U2, and U1 unconformities show lateral continuity but are not present everywhere in the Ross Sea. Aggradation sequences occur below U5 on the north-western Ross Sea margin and on the eastern Ross Sea margin, while a prevailing progradational pattern with substantial advance of the shelf break occurs in the more recent sedimentary sequences. All the unconformities seem to be controlled by glacial erosion and tectonics. The beginning of progradation is related to the onset of major glacial expansion which prevented the preservation of most of the thin interglacial sedimentary sequences. The greater sediment thickness and greater advance of the shelf break in the eastern Ross Sea suggest a different ice flow pattern on the two sides of the Ross margin.