The MARGEST cruise, carried out from 9 to 27 April 2022 on board the R/V ALIS, aims to gain a better understanding of the evolution and stratigraphy of the modern mixed silicoclastic/carbonate tropical platform on the eastern margin of New Caledonia's Grande Terre. This cruise follows a previous study of the Southwest platform (Calgon cruise, 2002, CALICO cruise, 2013) carried out by the same research team belonging to the Geological Survey of New Caledonia, Ifremer and the University of Brest. The objectives of the cruise were in particular to:

• Recognise in detail the stratigraphic architecture of the eastern platform of Grande Terre, including the internal platform, the palaeochannels, the passage systems and their outlets through the reef barrier;
• Constrain current sediment transfer processes across the shelf, and understand sediment partitioning;
• To understand the potential control of Neogene tectonics on Quaternary sedimentation.

The 17-day cruise (Noumea/Noumea) on the N/O Alis focused mainly on the lagoon domain and the upper slope (up to 400m depth) of the eastern margin, combining acquisitions by multibeam bathymetry, side-scan sonar imagery, single- and multi-track sparker seismic, and sampling by Küllenberg corer, Shipek grab, dredge, video module and sidescan imagery.

The study area covers nearly 200km between the latitudes of Yaté in the south and Ponérihouen in the north. The areas of Cap Bayes de Thio and Kouakoué were studied in particular with geophysical surveys and sampling along transects from the coast to the upper slopes.