The integration of Orthophragmina (larger Foraminifera) zonation, based on the artificial dissection of evolutionary lineages, in between planktonic and benthic subdivisions by zones can be carried out only by a considerable distortion of its internal consistency. Therefore the zonation as a whole was correlated first with numerical time scales, then through the latter with physical and paleontological subdivisions. This process is named numerical evolutionary correlation in which we used 20 evolutionary lineages of Upper Paleocene and Eocene Orthophragminae. The development of the common logarithm of the cross-diameter (d) of the deuteroconch (the second chamber of the megalosphaerical embryon) was considered to be an evolutionary clock. First we estimated the evolutionary age-functions of particular lineages in the shape of f(x)=a.x+b, where f(x) is the numerical evolutionary age and x is the value on the evolutionary clock, based on 54 samples from throughout Europe. Then by a convergent iteration procedure we made stepwise more and more precise estimates, alternatively for the numerical evolutionary ages of the samples and for the evolutionary age-functions. As a result we got a numerical evolutionary scale that can be correlated with any numerical time scale by tie-points. The procedure is open: under certain conditions any group of fossils can be inserted into it, thus it can be expanded at will both in time and space. Considering its internal proportions, the numerical evolutionary scale is independent of any numerical time scale, while it is well in accord with them as concerns the Eocene, thus it can possess a chronostratigraphic importance, too.
ASJC Scopus subject areas
- Space and Planetary Science