NEW PALAEOECOLOGICAL DATA PROVIDED BY THE PREMERY FOREST CLOSED DEPRESSIONS (BURGUNDY-FRANCE)

The closed depressions (CDs) located in the Premery forest on the Nivernais Plateau (Burgundy, France) are suitable natural archives for palaeoecological studies as formerly demonstrated in the sixties. New pollen and non-pollen palynomorphs (mainly algal and fungal remains) analyses performed on two sequences, give complementary information about the context of the CDs infilling formation, and the vegetation dynamics on the Nivernais Plateau. The two cores chronologically complete each other: the first one concerns the Late Glacial and the Early Holocene (from 16 000 to 10 000 cal. yr BP), but it is less suitable for Mid- and Late Holocene because of hiatuses in the sedimentation. The second one documents only the end of the Late-Glacial period (Younger Dryas), but it continuously covers the whole Holocene. Concerning human impact, the indicators of agro-pastoral activities are very scarce and punctual during Prehistory and Bronze Age (from ca 5 000 to 800 BC). Even after this date, and despite further deforestation phases occurring during the Iron Age (800-50 BC), the classical Middle Ages (around 1000 AD) and the Modern period, the woodland remains dominant, and proximal pollen and fungal indicators of human activity are only present in one core, from the 16th to the beginning of the 19th century. However, the forest might be affected for other reasons than agro-pastoral purpose, such as fire wood, timber wood, palaeo-industries... If these two CDs have comparable evolutions during Late-Glacial and Early Holocene, running from a state of small pond to small peat bog, their later histories are different. This fact shows the role of the catchment area variability for each CD infilling process, and it highlights the very local value of each of the palaeoecological information they provide.