Résumé
Detailed continental records of past interglacials where both palaeoenvironnemental and paleoclimatic reconstructions can be achieved are scarce in NW Europe. In this context, calcareous tufas are generally the only sedimentary records of Pleistocene interglacial optima. They are thus key-archives to investigate climate-environment interactions during interglacials for they contain abundant flora and fauna remains (especially molluscs) and their calcite composition allows direct dating as well as geochemical reconstructions of palaeoclimatic parameters. During the last two decades, multiproxy investigations of tufa deposits from northern France, including Caours (Somme basin, MIS 5e) et La Celle (Seine valley, MIS 11c), have provided detailed records of climatic and environmental changes during past interglacials and allowed comparisons with the Holocene.In the Seine basin, the large tufa deposit of Resson has recently provided the opportunity to expand the record of Eemian environments and climates in the area. The site delivered in the 19th century a rich content in macroflora and large mammal fossils but was little investigated since. New fieldworks involving a multidisciplinary research team have allowed to describe and sample an extended section (>20 m long) of the Resson tufa. The entire 10m-thick sequence was sampled continuously and in parallel for malacology and isotopic geochemistry. Preliminary mollusc data indicate a high richness, especially in the number of both land snails and forest species and document the progressive development of interglacial conditions. Calcite stable isotopes provide a consistent record, showing a regular increase in humidity (δ13C) and warm conditions (δ18O), reaching an optimum in the upper part of the sequence. Compared to Caours palaeoenvironmental and palaeoclimatic reconstructions, where the optimum is strongly marked at the very bottom of the tufa sequence, Resson provides a more dilated record of the progressive establishment of wet and temperate conditions during the early phase of the Last Interglacial. Comparisons with data from tufas assigned to other interglacials from the same area confirm that the Eemian optimum, just as the MIS 11c, was significantly wetter than the Atlantic period while no strong differences are observed between Eemian and Holocene temperatures.