More than 700 petrographic samp.lcs from the Vions formation (Upper Berriasian, Southern Jura mounlains, France) are automatically classified into 7 microfacies. These samples are described by means of 41 non-numerical variables (descriptors), which are used to compute matching coefficients (Sokal-Michener type). The coefficient matrix is treated according to the unweighted pairgroup method, and a dendrogram is produced, on which the microfacies are defined.

The relative importance of descriptors to the classification is then expressed by the combination of the total and within-group variabilities.

Finally, the degree of relationship between all the descriptors is established without using the usual contingency coefficients, and 3 paleontological associations are shown, which are characteristic of the Vions formation.