Comparison of the ages of large-body impacts, flood-basalt eruptions, ocean-anoxic events and extinctions over the last 260 million years: a statistical study

Many studies have linked mass extinction events with the catastrophic effects of large-body impacts and flood-basalt eruptions, sometimes as competing explanations. We find that the ages of at least 10 out of a total of 11 documented extinction events over the last 260 Myr (12 out of 13 if we include two lesser extinction events) coincide, within errors, with the best-known ages of either a large impact crater (≥70 km diameter) or a continental flood-basalt eruption. The null hypothesis that this could occur by chance can be rejected with very high confidence (>99.999%). The ages of large impact craters correlate with recognized extinction events at ~36 (two impacts), 66, 145 and 215 Myr ago (and possibly an event at ~168 Myr ago), and the ages of continental flood basalts correlate with extinctions at 66, ~94, ~116, 183, 201, 252 and 259 Myr ago (and possibly at ~133 Myr ago). Furthermore, at least 7 periods of widespread anoxia in the oceans of the last 260 Myr coincide with the ages of flood-basalt eruptions (with 99.999% confidence), and are coeval with extinctions, suggesting causal connections. These statistical relationships argue that most mass extinction events are related to climatic catastrophes produced by the largest impacts and large-volume continental flood-basalt eruptions.