Manfred Menning, Dieter Weyer, Immo Wendt, Nicholas J. Riley & Vladimir I. Davydov write: ⇓Hess et al. (1999, p. 528) investigated ‘about one dozen rock samples from coal tonsteins’ from the Donets Basin for Ar/Ar sanidine dating. ‘Unfortunately, only one proved could be dated isotopically. All other samples contain no chronometer minerals that which were (1) of primary volcanic origin and (2) unaffected by secondary alterations’. The datable sample has an age of 305.5±1.5 Ma (±1σ without the age errors of the monitors) using sanidines for high-precision Ar/Ar spectrum dating. However, the expected age is about 6 Ma older according to sanidine tuff ages from Central Europe (⇓Lippolt et al. 1984). Hess et al. (p. 532) concluded that ‘the most plausible explanation [for this deviation] is an inaccurate or even erroneous [biostratigraphic] correlation of the Donets Basin Carboniferous with the Western European and non-European Carboniferous occurrences’. They ‘suggest a reconsideration of the validity of the current biostratigraphic correlation between the Carboniferous of western and East Europe’ (p. 527).

We reconsider the biostratigraphic correlation because an age difference of about 6 Ma corresponds to the duration of about two substages (stages) of the Upper Carboniferous e.g., Westphalian B+C (Duckmantian+Bolsovian). Such fundamental biostratigraphic miscorrelation between best known mining areas is extremly improbable.

We explain the presumed age difference by a significant correction of the erroneous biostratigraphic correlation used by Hess et al. (fig. 2), which reduces the discussed about 6 Ma to a markedly smaller difference of about 4 Ma. These 4 Ma are not significant if (necessarilly) 2σ analytical age uncertainties are taken into account.