Introduction

In the years following the consensus on the Pliocene–Pleistocene boundary in France (Chaline and Michaux, 1972a) and the observation (Chaline, 1977) that the appearance of Allophaiomys pliocaenicus in European mammal faunas is synchronous with the Neogene–Quaternary boundary proposed by IGCP-41 at the top of the Olduvai event, there have been several further developments. In this chapter we review, in succession, the following: the new “rodent biostratigraphy” and the correlations that it implies; geochronologic data permitting new calibrations; new palynological and faunal data of significance for paleoclimatic correlations in northern Europe; and a reevaluation of the classic sites with respect to the Neogene–Quaternary boundary.

“Rodent biostratigraphy”

In the classic sites of Plio–Pleistocene age, the large mammals have provided the basis for a biostratigraphy that approaches a succession of assemblage-zones or cenozones. In practice, however, the true affiliations of the large mammal species from the various levels are seldom known for certain, because it is only rarely that sufficient numbers of individuals are found in a given assemblage to permit reliable determinations of the intraspecies and interspecies variations. The same is not true for rodents, which are notably very abundant in cave fillings, but can also occur in equal numbers in fluviolacustrine deposits. The best-documented rodent lineage in the interval under discussion is that which began with Mimomys occitanus, with seven species ranging from the middle Pliocene to middle Pleistocene (Chaline and Michaux, 1972a,b).