High-precision dating of the Kalkarindji large igneous province, Australia, and synchrony with the Early-Middle Cambrian (Stage 4-5) extinction

Abstract

The voluminous Kalkarindji flood basalts erupted in Australia during the Cambrian and covered >2 × 106 km2. New U-Pb and 40Ar/39Ar age data from intrusive rocks and lava flows yielded statistically indistinguishable ages at ca. 511 Ma, suggesting a relatively brief emplacement for this province. A zircon age of 510.7 ± 0.6 Ma shows that this province is temporally indistinguishable at the few-hundred-thousand-year level from the Early-Middle Cambrian (Stage 4-5) boundary age of 510 ± 1 Ma, which marks the fi rst severe extinction of the Phanerozoic and an extended marine anoxia period. Sulfur concentration measurements ranging from <50 to 1900μg/g, and fractal analysis of extensive explosive..