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Austradec I and II marine seismic surveys carried out in 1972 and 1973 by the IFP-CEPM-ORSTOM group in the southwes tem Pacifi,c contribüted to the exploration of the structural elements located between Lord Howe Rise and Norfolk Ridge, investigated the sedimentary fills in accordance with data from DSDP boreholes, and pointed out the importance of volcanic alignments.
The leading structural element discovered by these surveys was the Fairway Ridge beginning at Fairway Reef in the North. Two of us (C.E. de Broin and C. Ravenne) consider that this ridge prolongs into West Norfolk Ridge towards the South.
The discovery of this ridge thus leads us to divcde the New Caledonia Basin into an eastem New Caledonia Basin sensu stricto and a wes tem Fairway Basin.
A study of seismic facies and data from DSDP boreholes enables us to suggest that the fill in the New Caledonian Basin sensu stricto is mainly of turbidite origin and that in the Fairway Basin is mainly pelagic except in its southem part. The proportion of elements derived from volcanism is considerable in both basins.
Lastly, we clearly delimit two volcanic alignments, i.e. one located in the eastem part of Lord Howe Rise, and the other in the westem part of Norfolk Ridge.
In this paper we first describe the structural elements, and then we show how magnetic data confirm our hypotheses , before examining the sedimentary series.