The oceanic collection consists of sediment cores and dragged sediments, mainly collected by crews on the French ship, the Marion Dufresne. These samples help to improve our knowledge of the composition of the oceanic crust and the evolution of past climates.
The oceanic collection consists of around 700 marine sediment cores and 70 rock dredges , mainly from the Indian Ocean. Sediment cores can reach lengths of over 50 metres, representing a time interval in the Earth’s history. Depending on the sites where the samples are taken, this interval can vary from around ten thousand years to millions of years. Each core is then cut into sections of around 1.50 metres. They are preserved in 3 cold chambers in the basement of the Geology building, at a temperature of 7°C. In addition, dredges can represent a tonne of oceanic rocks from the seafloor. These are stored at ambient temperature.
The oceanic collection is very recent compared to the Muséum’s other collections. It was initiated in 1973 with the development of new tools that enabled deep sea coring. The boat Marion Dufresne 1, chartered by the FSAL (French Southern and Antarctic Lands) and built in 1972, developed a coring system in the 80s that could reach lengths of up to 30 metres. Currently the Marion Dufresne 2’s Calypso corer (commissioned in 1995) enables coring of up to 60 metres of sediment at depths of up to 5,000 metres. Since then other tools have been developed, like the CSAQ corer, which is still on board the Marion Dufresne 2 and is used to sample very large square cores.
The purpose of this collection is mainly scientific research. However, a few samples have also been the subject of exhibitions inside and outside of the Muséum. Ocean cores form the basis for palaeoclimatic studies (study of ancient climates). The sediment’s mineralogical composition and the many microfossils it contains enable us to learn about and reconstruct the climate and oceanic conditions of the past. Only half of the core (the work sections) is used for sampling, and the other half is stored (archive sections) and only used rarely. Moreover, the samples resulting from dragging are made up of rocks (basalts, peridotites, gabbros, etc.) from mid-ocean ridges and polymetallic nodules. The latter are millimetric or centimetric spherules formed of concentric circles of iron and manganese hydroxides around a core. They are rich in copper, nickel and cobalt.