Identification of reef facies by computer classification

A newly developed, hierarchical, agglomerative computer programme using an information statistic for the classification of mixed data shows that the various facies of the well‐exposed Famennian reefal limestones of the Bonaparte Basin, northwest Australia, are characterised by distinctive assemblages of groups defined numerically by 30 petrographic and 11 chemical attributes, and qualitatively by 6 petrographic attributes. Assemblages of groups from fragmentary occurrences of Frasnian and Lower Carboniferous carbonates in the Bonaparte Basin were compared with those of the Famennian reefal sequence: two occurrences were thus identified as inter‐fingering lagoonal‐back‐reef fades, and a third as non‐reefal. Given a geologically determined situation as a control, this method, with its power to resolve geologically significant groups, is ideal for studying the common intrinsically complex problems in geology.