What causes mass extinctions? Large asteroid/comet impacts, flood-basalt volcanism, and ocean anoxia—Correlations and cycles
Published:September 11, 2019
Michael R. Rampino*, Ken Caldeira, Andreas Prokoph#, 2019. "What causes mass extinctions? Large asteroid/comet impacts, flood-basalt volcanism, and ocean anoxia—Correlations and cycles", 250 Million Years of Earth History in Central Italy: Celebrating 25 Years of the Geological Observatory of Coldigioco, Christian Koeberl, David M. Bice
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What causes recurrent mass extinctions of life? We find that the ages of 10 of the 11 well-documented extinction episodes of the last 260 m.y. show correlations, at very high confidence (>99.99%), with the ages of the largest impact craters or the ages of massive continental flood-basalt eruptions. The four largest craters (≥100 km diameter, impact energies ≥3 × 107 Mt trinitrotoluene [TNT]) can be linked with recognized extinction events at 36, 66, 145, and 215 Ma, and with stratigraphic distal impact debris correlative with the extinctions. The ages of 7 out of 11 major flood-basalt episodes can be correlated with extinction events at 66, 94, ca. 120, 183, 201, 252, and 260 Ma. All seven flood-basalt–extinction co-events have coincident volcanogenic mercury anomalies in the stratigraphic record, closely linking the extinctions to the volcanism. Furthermore, the seven major periods of widespread anoxia in the oceans of the last 260 m.y. are significantly correlated (>99.99%) with the ages of the flood-basalt–extinction events, supporting a causal connection through volcanism-induced climate warming. Over Phanerozoic time (the last 541 m.y.), the six “major” mass extinctions (≥40% extinction of marine genera) are all correlated with the ages of flood-basalt episodes, and stratigraphically with related volcanogenic mercury anomalies. In only one case, the end of the Cretaceous (66 Ma), is there an apparent coincidence of a “major” mass-extinction event with both a very large crater (Chicxulub) and a continental flood-basalt eruption (the Deccan Traps).
The highly significant correlations indicate that extinction episodes are typically related to severe environmental crises produced by the largest impacts and by periods of flood-basalt volcanism. About 50% of the impacts of the past 260 m.y. seem to have occurred in clusters, supporting a picture of brief pulses of increased comet or asteroid flux. The largest craters tend to fall within these age clusters. Cross-wavelet transform analyses of the ages of impact craters and extinction events show a common, strong ~26 m.y. cycle, with the most recent phase of the cycle at ~12 Ma, correlating with a minor extinction event at 11.6 Ma.
The stream of life flows so slowly that the imagination fails to grasp the immensity of time required for its passage, but like many another stream it pulses irregularly as it flows. There are times of quickening, the expression points of evolution, which are almost invariably coincident with some great geologic change, and the correspondence so exact and so frequent that the laws of chance may not be invoked by way of explanation.
—Richard Swann Lull (Organic Evolution, New York, Macmillan, 1929, p. 693)
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250 Million Years of Earth History in Central Italy: Celebrating 25 Years of the Geological Observatory of Coldigioco
Central Italy has been a cradle of geology for centuries. For more than 100 years, studies at the Umbria and Marche Apennines have led to new ideas and a better understanding of the past, such as the Cretaceous-Paleogene (K-Pg) boundary event, or the events across the Eocene-Oligocene transition from a greenhouse to an icehouse world. The Umbria-Marche Apennines are entirely made of marine sedimentary rocks, representing a continuous record of the geotectonic evolution of an epeiric sea from the Early Triassic to the Pleistocene. The book includes reviews and original research works accomplished with the support of the Geological Observatory of Coldigioco, an independent research and educational center, which was founded in an abandoned medieval hamlet near Apiro in 1992.