Numerical dating of the Eckfeld maar fossil site, Eifel, Germany: a calibration mark for the Eocene time scale.

Sediments of the Eckfeld maar (Eifel, Germany) bear a well-preserved Eocene fauna and flora. Biostratigraphically, Eckfeld corresponds to the Middle Eocene mammal reference level MP (Mammals Paleogene) 13 of the ELMA (European Land Mammal Age) Geiseltalian. In the maar crater, basalt fragments were drilled, representing explosion crater eruption products. By 40Ar/39Ar dating of the basalt, for the first time a direct numerical calibration mark for an Eocene European mammal locality has been established. The Eckfeld basalt inverse isochron date of 44.3 +/- 0.4 Ma suggests an age for the Geiseltalian/Robiacian boundary at 44 Ma and, together with the 1995 time scale of Berggren et al., a time…