2025-10-27 中国科学院（CAS）
Carbonate carbon and carbonate-associated sulfate sulfur isotopes. (Image by NIGPAS)
＜関連情報＞
- https://english.cas.cn/newsroom/research_news/earth/202510/t20251027_1094847.shtml
- https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2025GL118689
軌道駆動型栄養脈動は初期カンブリア紀の周期的酸素化と動物の放射線に関連している Orbitally-Driven Nutrient Pulses Linked to Early Cambrian Periodic Oxygenation and Animal Radiation
Yinggang Zhang, Benjamin J. W. Mills, Robert J. Newton, Tianchen He, Ailsa Roper, Tao Yang, Maoyan Zhu
Geophysical Research Letters Published: 22 October 2025
DOI:https://doi.org/10.1029/2025GL118689
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 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.
Plain Language Summary
During the Cambrian Explosion, many major animal groups appeared in a relatively short period of time. These evolutionary bursts happened alongside seawater chemical changes which are thought to reflect variations in the amount of oxygen in Earth’s oceans and atmosphere, which could set the pace of animal diversification. But the cause of these oxygen fluctuations has remained unclear. In this study, we show that slow changes in Earth’s orbit may have played a key role. Our model shows that changing inputs of solar energy can change weathering processes on land and the flow of nutrients into the ocean, driving photosynthesis, and increased production of oxygen that occurs in pulses similar to those seen in animal evolution.
Key Points
- Carbon and sulfur isotope records from the early Cambrian show evidence of orbital cyclicity
- Biogeochemical modeling suggests that orbitally-driven nutrient pulses could drive long-period cyclic variations in the C-S-O cycles
- Low ocean sulfate levels were likely crucial in amplifying the C-S-O cycle responses to orbitally-driven nutrient pulses
