Felsic volcanism as a factor driving the end-Permian mass extinction.

The Siberian Traps large igneous province (STLIP) is commonly invoked as the primary driver of global environmental changes that triggered the end-Permian mass extinction (EPME). Here, we explore the contributions of coeval felsic volcanism to end-Permian environmental changes. We report evidence of extreme Cu enrichment in the EPME interval in South China. The enrichment is associated with an increase in the light Cu isotope, melt inclusions rich in copper and sulfides, and Hg concentration spikes. The Cu and Hg elemental and isotopic signatures can be linked to S-rich vapor produced by felsic volcanism. We use these previously unknown geochemical data to estimate volcanic SO2 injections and argue that this volcanism would have produced several degrees of rapid cooling before or coincident with the more protracted global warming. Large-scale eruptions near the South China block synchronous with the EPME strengthen the case that the STLIP may not have been the sole trigger.

Are Impact Craters and Extinction Episodes Periodic? Implications for Planetary Science and Astrobiology.

A review of the results of published spectral analyses of the ages of terrestrial impact craters (58 analyses) and biotic extinction events (35 analyses) reveals that about 60% of the crater trials support a statistically significant cycle averaging ∼29.7 million years (My), and about 67% of the trials of extinction episodes found a significant cycle averaging ∼26.5 My. Cross-wavelet transform analysis of the records of craters and extinctions over the past 260 My shows a mutual ∼26 My cycle and a common phase, suggesting a connection. About 50% of the best-dated impact craters seem to occur in approximately nine pairs or clusters in the past 260 My, apparently carrying the signal of an ∼26- to 30-My cycle. It has been suggested that periodic modulation of impacts and extinctions might be related to periodic comet storms that follow the solar system's oscillations in and out of the galactic mid-plane. Problems arise, however, with regard to the compatibility of such periodic pulses of comet flux with the makeup of the steady-state Near Earth Object (NEO) population, the estimated long-term NEO cratering rates on the terrestrial planets, and the predicted small contribution of Oort Cloud-derived comets to the terrestrial cratering record. Asteroid storms may be possible, but at present there are no accepted mechanisms for creating an ∼30-My period in asteroid breakup events and impacts. Astrobiological implications arise if extra-solar habitable planets suffer similar cyclical or episodic catastrophic bombardment episodes affecting long-term biotic evolution on those planets. Other planetary systems might commonly have comet reservoirs, but they are less likely to contain an asteroid belt in the proper orbital position. Further, frequent impacts of ∼1-km diameter comets and asteroids could affect the establishment and longevity of technological civilizations, including our own.

Global nickel anomaly links Siberian Traps eruptions and the latest Permian mass extinction.

Anomalous peaks of nickel abundance have been reported in Permian-Triassic boundary sections in China, Israel, Eastern Europe, Spitzbergen, and the Austrian Carnic Alps. New solution ICP-MS results of enhanced nickel from P-T boundary sections in Hungary, Japan, and Spiti, India suggest that the nickel anomalies at the end of the Permian were a worldwide phenomenon. We propose that the source of the nickel anomalies at the P-T boundary were Ni-rich volatiles released by the Siberian volcanism, and by coeval Ni-rich magma intrusions. The peaks in nickel abundance correlate with negative δ13C and δ18O anomalies, suggesting that explosive reactions between magma and coal during the Siberian flood-basalt eruptions released large amounts of CO2 and CH4 into the atmosphere, causing severe global warming and subsequent mass extinction. The nickel anomalies may provide a timeline in P-T boundary sections, and the timing of the peaks supports the Siberian Traps as a contributor to the latest Permian mass extinction.

Comment on "Atmospheric PCO2 perturbations associated with the Central Atlantic Magmatic Province".

Schaller et al. (Research Article, 18 March 2011, p. 1404) proposed that carbon dioxide (CO(2)) released by the Central Atlantic Magmatic Province eruptions over periods of about 20,000 years led to substantial increases of up to 2000 parts per million (ppm) in the concentration of atmospheric carbon dioxide (PCO(2)) near the Triassic-Jurassic boundary. Use of an atmosphere-ocean model coupled to a carbon-cycle model predicts PCO(2) increases of less than 400 ppm from magmatic volatiles, with only a small climatic impact.