Manfred Menning, Dieter Weyer, Immo Wendt, Nicholas J.
     Riley & Vladiinir I. Davydov write: Hess et al (1999, p. 528)
     investigated 'about one dozen rock samples from coal
     tonsteins' fro   the Donets Basin tot 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 (+/- sig 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 a inaccurate or even
     erroneous [biostratigraphic] correlation of the Donets Basin
     Carboniferous with the Western European und 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 biostratigraphie 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 fun-
     damental 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 (necessarily) 2sig analytical age
     uncertainties are taken into account.