Orbitally‐Driven Nutrient Pulses Linked to Early Cambrian Periodic Oxygenation and Animal Radiation

Abstract 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 O 2 , 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.