A new late Thanetian mammal fauna from Therdonne (Oise, France): new evidence for a Clarkforkian-equivalent biozone in Western Europe

The Paleocene-Eocene transition is marked by dramatic global climatic change correlated with pronounced mammalian faunal change. A new late Paleocene mammal fauna from the Butte de Therdonne in the Paris Basin is described and compared with fossil assemblages of similar age elsewhere in Europe and North America. The Therdonne fauna is currently documented by c. 45 identifiable fossil specimens representing nine mammalian species. The stratigraphic position of this fossil assemblage in the early Paleogene Therdonne sequence indicates a late Thanetian age, and the taxonomic assemblage is consistent with the MP6b reference biochronological level defined on the basis of a mammalian fauna found in the Rivecourt sand Member in the Oise Valley, about 40 km east of Therdonne. The relative diversity of rodents and condylarthrans including the North American apheliscid Aletodon Gingerich, 1977, are the most striking characteristics of this fauna. Several lines of evidence, including biostratigraphy, sequence stratigraphic interpretation of the Therdonne section, and correlations with boreholes of the Paris Basin lead us to correlate the Therdonne and Rivecourt faunas. Therdonne therefore pertains to the MP6b biozone which corresponds roughly to the 1 Ma interval preceding the onset of the carbon isotope excursion (CIE) that marks the Paleocene-Eocene boundary.