Micropaleontological counting methods and techniques : an exercise on an eight metres section of the lower Pliocene of Capo Rossello, Sicily

Abstract

The LG.C.P. project 74/1/1 "a systems approach to accuracy in time", aims at a quantification of the refinement that may be attained with various methods of stratigraphic correlation. A considerable part of the pilot studies carried out by the "Dutch" working group deals with the application of numerical methods in biostratigraphy, in which one of the lines of research aims at a better understanding of counted numbers of specimens of individual taxa in suites of samples, as presented in so-called distribution charts or range charts. The biozonations constructed from such charts, from which in practice the more general zonation schemes are compiled, are commonly based on entries and exits of indivual taxa or groups of taxa. The corresponding datum levels based on single or multiple presence-absence criteria (as well as relatively high frequencies of taxa, so-called acmes) determine the zones recognized in the vertical successions. These methods and the actual counting on which they are - often unconsciously - based are being evaluated by the Utrecht team for several sections of the Mediterranean Neogene. The purpose of the present investigation was only to obtain a better documented insight in the reliability of different methods of collecting quantitative data.