Stratigraphic events defined by the highest or lowest

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occurrences of fossils in a group of wells or natural sections can be ordered into an optimum sequence. In the statistical model used, the relative position of the events in the most likely sequence is an "average" of all the relative positions encountered. The frequency of cross-over (miscorrelation) of events in the sections correlated has been used to estimate average distances between successive events in the optimum sequence. The events can be clustered by using the estimated distances between them, which gives results similar to those of the assemblage zone approach in biostratigraphy.

The computer program prepared for the statistical model has been used to create a zonation for our Cenozoic benthonic and planktonic foraminiferal record (209 taxa) in 22 wells on the Canadian Atlantic continental margin between 43 and 60°. Northern and southern optimum sequences have been recognized containing 40 and 60 taxa, respectively, about half of which are in common. The southern sequence contains 11 Eocene and 7 Miocene planktonic foraminiferal species and the northern sequence contains 6 Eocene species. The difference reflects more pronounced post-Eocene latitudinal watermass heterogeneity and differential post-Eocene shallowing across the margin.

The northern and southern probabilistic zonations each consists of eight clusters of Paleocene through Pliocene-Pleistocene age.

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