Abstract
Recent revised magnetostratigraphic and astrochronologic calibrations of several calcareous planktonic microfossil datum events (in particular
Coccolithus miopelagicus and
Neogloboquadrina acostaensis) combined with our magnetobiostratigraphic investigation of a 10 m-thick section at Ecotet, near Lyon (France), in which terrestrial micromammals (Vallesian Zone MN9) are intercalated with calcareous nannoplankton and planktonic foraminifera belonging to Zones NN6–NN8 and N14–15 (=M11 and M12), respectively, lead us to question the recent recalibration by Krijgsman et al. [(1996) Eart Planet. Sci. Lett. 142, 367–380) of the Aragonian/Vallesian (MN7–8/MN9) boundary with Chron C5r.1r (∼11.1 Ma) and the lower/upper Vallesian (MN9/10) boundary with Chron C4Ar.2n (∼9.6–9.7 Ma). Ecotet, with a uniform reverse polarity, is shown to be assignable uniquely to Chron C5r. Interregional correlation of Ecotet with Mediterranean terrestrial stratigraphies indicates that
Progonomys (whose First Occurrence (FO) has been traditionally placed in Mediterranean Mammal Zone MN10) was already present in Mediterranean Zone MN9 at ∼11.4 Ma and did not experience a 2 million-year delay in its putative prochoresis from Asia.