Probabilistic analysis of a suite of internally consistent data on the distribution of calcareous nannofossils

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in 13 sections of late Paleocene and early Eocene strata yields a series of possible subdivisions. These subdivisions may be considered analogous to biostratigraphic zones, but they are defined in terms of a given level of the probability that a particular sequence is due to nonrandom distribution of species occurrences. Considering 144 species, and using a level of probability greater than 0.8, sequential relations exist between the lowest occurrences of 87 and between the highest occurrences of 86 of the species. Eleven stratigraphic intervals can be recognized using lowest occurrences exclusively and 9 intervals using highest occurrences exclusively. The limits of each interval can be defined in terms of mutually random occurrences of several different species.

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