How do the changes in benthic foraminiferal 18O compare to the already defined epoch boundaries

The long-term (greater than 106 yr) character of the Earth’s climate appears to exhibit distinct shifts from one state to the next. The succession of such states can be thought of as an evolutionary process with the average characteristics of each successive climatic state fundamentally different from any previous state. Each state may differ in terms of mean condition, in the amount of oscillation around the mean condition, and in the distribution of the amplitude of oscillation as a function of frequency. This long-term evolution of climate appears to be associated with telluric changes (i.e., changes in the geography and topography that form the boundaries to the fluid spheres). The rate of climatic change depends on the nature of the telluric effects. For example, the opening of an ocean gateway to deep and surface flow (such as passage between Antarctica and Australia) may have had a sudden and dramatic effect on average oceanic conditions, whereas the gradual opening of the Atlantic or closing of the Tethyan seaway may have caused longer term shifts in climatic conditions.

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