949 / 2024-09-19 21:47:23

Impact of orbitally forced peatland dynamics on atmospheric CO2 concentration in the Mid-Jurassic

Peat,jurassic,Orbital cycles

Session 42 - Deep-time ocean and climate changes: insights from models and proxies

The Jurassic greenhouse period was marked by generally high atmospheric pCO₂ and frequent perturbations of the global carbon cycle. As a significant terrestrial sink for organic carbon, coal accumulation dynamics during this period can be a major contributor to the global carbon cycle. However, there is still limited understanding of the causal relationship between climate, peatland dynamics, and atmospheric pCO₂ fluctuations during the Jurassic. Here we present a ~ 2.2-Myr-long high-resolution reconstruction of atmospheric pCO₂ in the Aalenian using δ¹³C of fossil C₃ plants preserved in sediments from the Ordos Basin, North China. We show an apparent correspondence between periodic pCO₂ changes and the waxing and waning of mid-latitude peatlands at 405-kyr eccentricity cycles, correlating with δ¹³C shifts in both marine and terrestrial realms. Mass balance calculations show that the estimated organic carbon storage of ~1540 Gt in Ordos Basin peatlands alone during eccentricity minima would have reduced ~50% of the reconstructed global pCO₂ drawdown and accounted for ~25% of marine δ¹³C positive excursion. Our results suggest that climate-driven peatland dynamics and organic carbon burial at Earth’s surface might have played a major role in the global carbon cycle during the Middle Jurassic greenhouse world.