J. T.Temple writes: The appearance of the new Guide to stratigraphical procedure presented on behalf of the Stratigraphy Committee of the Society (Whittaker et al. 1991) is welcome, and several aspects of the Guide will undoubtedly be useful to stratigraphers. The section on biostratigraphy, however, is inadequate: not only does it omit discussion of two fundamental logical problems in biostratigraphical correlation, but it ignores also the whole important field of quantitative stratigraphical correlation.
The first problem is epitomized by fig. 2 of the Guide (1991, p. 816), which illustrates different types of biozone in relation to the stratigraphical ranges of several taxa (the relevant taxa are identified in the text of the Guide as usually being species, and this usage will be followed here). The figure shows the stratigraphical ranges of various species, but it is unfortunately not made clear to the reader whether these are the ranges in a single section or composite ranges based on several sections (presumably they must be one or the other). It is convenient to consider first the parts of fig. 2 that include more than one species (i.e. figs. 2B, C & F). If these diagrams represent the ranges of the species in a single section, the biozones so defined apply only to that particular section and are irrelevant to correlation, since we cannot assume a priori that the mutual relations of the species will be the same in all sections (Temple 1988, p. 875). If, on the other hand, figs 2B, C
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