Recognizing pulses of extinction from clusters of last occurrences

The distribution of last occurrences of fossil taxa in a stratigraphic column are used to infer the pattern, timing, and tempo of extinction from the fossil record. Clusters of last occurrences are commonly interpreted as an abrupt pulse of extinction. However, stratigraphic architecture alone can produce clusters of last occurrences that can be misinterpreted as an extinction pulse. These clusters will typically occur in strata that immediately underlie facies changes and sequence-stratigraphic surfaces. It has been proposed that a basin-wide analysis of the fossil record within a sequence-stratigraphic framework can be used to distinguish between clusters of last occurrences caused solely by extinction pulses from those generated by sequence-stratigraphic architecture. A basin-wide approach makes it possible to observe lateral facies shifts in response to sea-level change, mitigating the effects of stratigraphic architecture. Using computer simulations of plausible Late Ordovician mas...