During the Cambrian Explosion, episodic radiations of major animal phyla occurred in concert with repeated coupled carbon-sulfur isotope excursions.
These isotope patterns are thought to reflect oscillations in atmospheric and shallow-marine O2, which promoted animal diversification events. However, the driver for oxygenation pulses is unclear.
Here we show that these synchronous carbon-sulfur isotope cycles and marine oxygenation pulses can be driven by long-period orbital forcing through effects on continental weathering and nutrient delivery. The impact of orbital forcing is explored using a combined climate-biogeochemical model.
When forced with latitudinally-resolved insolation signals, the model produces long-term variations in nutrient weathering and carbon burial, which reproduces the co-variation of carbon-sulfur isotopes.
We conclude that the oxygen-driven evolutionary changes in the early Cambrian can be explained by recurrent nutrient inputs to the ocean, resulting from climate change caused by long-period orbital cycles.
Orbitally-Driven Nutrient Pulses Linked to Early Cambrian Periodic Oxygenation and Animal Radiation, Geophysical Research Letters (open access)
Astrobiology, evolution,
