The object of this book is to explain how to create a synthesis of complex biostratigraphic data, and how to extract from such a syn thesis a relative time scale based exclusively on the fossil content of sedimentary rocks. Such a time scale can be used to attribute relative ages to isolated fossil-bearing samples. From a practical point of view, the method described in this book will particularly interest paleontologists and geologists who must construct zonations and establish correlations on the basis of bio stratigraphic data that are both plentiful and apparently contra dictory. It is well known that the difficulties involved in constructing bio chronologic scales are largely due to the discontinuous nature of the fossil record. We know that the relationships between the first ap pearances (or disappearances) of different fossil species are rarely constant in stratigraphic sections that are distant from each other. It if often extremely difficult to discover datums or sets of species that are useful in making significant biochronologic correlations on a large scale. The theoretical model explained here (known as the Unitary As sociation Method) provides clear solutions to most of these problems. That method is purely deterministic, as opposed to statistical and probabilistic analytical techniques producing "average" ranges. We demonstrate in Chapter 15 why most of these techniques produce results which are usually not compatible with the original biostrati graphic observations (i.e., the taxonomic contents of the studied sam ples are not reproduced in the outputs). The application of a deterministic mathematical model in solving stratigraphical problems leads to more realistic results than by statistic or probabilistic approaches. The aim of this analytical method, elaborated by the author, is to resolve systematically the multiple contradictions inherent to the stratigrahic record of fossil species. A theoretical part treating the interpretation of highly complex biostratigraphic data is followed by the presentation of the computer-aided Unitary Association Method. Geologists and structural geologists as well as micro-palaentologists in science and practice will benefit from this new tool in stratigraphy. Das Problem der biostratigraphischen Korrelation stellt sich Geologen, Paläontologen, Strukturgeologen, Sedimentologen in Lehre und Forschung, aber auch in der Erdölindustrie. Für sie bietet dieses Buch die Grundlage für einen sedimentstratigraphischen Kurs und eine hervorragende Methode zur Erstellung einer biostratigraphischen Zeitskala.