Continental climatic changes in Normandy (France) between 3.3 and 2.3 Myr B.P.

Pollen analysis of the La Londe sequence indicates that several environmental and climatic changes occurred during the interval between 3.3 and 2.3 Myr. The use of two pollen indices, the Climate Severity Index (CSI) and the Continental Biomass Index (CBI) permits the characterization of these changes. They illustrate significant climatic variations throughout the considered time interval. At the base of the record, the CSI indicates the occurrence of an important warming associated with an increase of the plant biomass. This event might be also associated with an important event recorded in Antarctica and in the Arctic ocean at the same time and increases in both oxygen and carbon isotope records from DSDP 552 A cores. A general cooling trend, punctuated by cold peaks leads to a major cooling at around 2.4 Myr, associated with low values of plant biomass.