The Early–Middle Cambrian (Stage 4-5) boundary which is approx. 510 million years old, marks the very first severe extinction of the Phanerozoic and an extended marine anoxia period.
In this study, F. Jourdan and colleagues use a combination of 40Ar/39Ar and U-Pb dating techniques to demonstrate that the Kalkarindji large igneous province (about two million square kilometers), Australia, was emplaced over a relatively short period of time 510-511 million years ago.
The temporal synchrony between the Kalkarindji eruption of and the Early-Middle Cambrian boundary approx. 510 million years ago is another example of a well-defined temporal correlation between volcanism, climate shifts, and extinction and extends such a relationship to the beginning of the Phanerozoic demonstrating a direct causation.
Geochemical analyses show that the likely factors responsible for the Early-Middle Cambrian extinction are climate shifts due to emission of mantle gases (SO2 and possibly CO2) dissolved in the magma, and gases (in particular CH4 and SO2) generated by the interaction between magma and abundant evaporite layers and oil-rich rocks.
Citation: High-precision dating of the Kalkarindji large igneous province, Australia, and synchrony with the Early–Middle Cambrian (Stage 4-5) extinction F. Jourdan et al., http://dx.doi.org/10.1130/G35434.1