The best sections method of studying mass extinctions

Abstract

Phanerozoic mass extinctions have been studied primarily by analysing global diversity patterns compiled from the published literature. However, such compilations are beset by problems of incorrect correlation, imprecise age assignments and changing taxonomy. An alternative approach is to analyse mass extinctions by the ‘best sections’ method. This method identifies abundantly fossiliferous, well‐studied, stratigraphically dense and temporally extensive fossil records in strata that contain geochemical and other relevant non‐palaeontological data from a single depositional basin or geographically restricted outcrop area as the ‘best sections’ by which to analyse extinctions. A strength of the best sections method is that it allows the extinctions identified to be compared directly to changes in facies and other factors recorded in the best section. And, the hypothesis of a widespread extinction based on an extinction seen in a best section can be tested by its presence or absence in temporally equivalent sections. What we need are more field‐based studies of the best sections that encompass mass extinctions (real and hypothetical) and less of a reliance on literature‐based diversity compilations to produce a more reliable and comprehensive understanding of the history of extinctions.

Recognizing pulses of extinction from clusters of last occurrences

“…This is particularly evident in depositionally up‐dip columns, where different extinction scenarios produce similar patterns of last occurrences (Figs 4A, 5A) owing to hiatuses that represent much of the Hirnantian in these columns. The extent to which face‐value patterns of last occurrences misrepresent the pattern, timing and tempo of an extinction provides strong evidence that relying on a single ‘best’ stratigraphic column for interpreting mass extinctions (as advocated by Lucas 2017, for example) will be misleading.…”

Stratigraphic paleobiology

“…For these reasons, many studies collect and interpret data at the outcrop scale, commonly from single stratigraphic columns. Some have even advocated that mass extinctions are best studied in a single stratigraphic column (Lucas 2017). Yet it is precisely at the outcrop scale where interpreting the timing, tempo, and causes of mass extinction and recovery are potentially most fraught.…”