THE 'MULTIPLE IMPACTS HYPOTHESIS' FOR MASS EXTINCTION: A COMPARISON OF THE LATE DEVONIAN AND THE LATE EOCENE

Abstract

Application of the lag-time multiple impacts hypothesis [Poag, 1997b. Palaios 12, 582–590; Poag et al., 2001. Columbia Univ. Press] to the Late Devonian leads to the prediction that the Frasnian–Famennian pulsed extinctions were triggered by a rapid drop in global temperature that followed an impact-produced anomalous warm interval, which interrupted the global cooling trend from the Middle Devonian greenhouse to the Early Carboniferous icehouse. In actualistic comparison with the late Eocene, the lag-time multiple impacts hypothesis would predict that a Frasnian interval of multiple impacts should have occurred between 367.7 and 366.7 Ma. The fact that three impacts (the Alamo, Siljan and Flynn Creek) do occur either within this predicted interval, or close to it in time, is corroborative evidence that the lag-time multiple impacts hypothesis may indeed provide the causal mechanism for the Frasnian–Famennian mass extinction. Based on the application of the lag-time multiple impacts hypothesis to the Frasnian–Famennian mass extinction, it is here suggested that future searches for evidence of impact events in the Late Devonian be concentrated in strata that occur in the Frasnian transitans to Early hassi zonal interval, and not in strata immediately below or above the Frasnian–Famennian boundary.