Arid Coastal Carbonates and the Phanerozoic Record of Carbonate Chemistry

Ocean chemistry and carbonate sedimentation link Earth's climate, carbon cycle, and marine pH. The carbonate system in seawater is complex and there are large uncertainties in key parameters in deep time. Here, we link sedimentary textures formed in arid coastal environments and preserved in the rock record to past seawater carbonate chemistry. Prior to the mid-Mesozoic, tepee structures and pisoids - features associated with peritidal environments - co-vary with available shelf area during cycles of supercontinent formation and rifting. In contrast, tepees and pisoids are consistently scarce after the mid-Mesozoic, which coincides with a radiation in pelagic calcifiers as well as the breakup of Pangea. Numerical models suggest that the global and temporal abundances of tepee structures and pisoids are correlated with secular shifts in seawater chemistry, and that trends likely reflect the underlying influence of tectonics and biotic innovation on marine alkalinity and the saturation states of carbonate minerals. As independent sedimentary proxies, tepees and pisoids serve as benchmarks for global carbon cycle models and provide a new proxy record of seawater chemistry that can help discern links among tectonics, biotic innovation, and seawater chemistry.

Automated summary

The study examines the connection between ocean chemistry, carbonate sedimentation, Earth's climate, carbon cycle, and marine pH. It explores how sedimentary textures like tepee structures and pisoids can serve as independent proxies for past seawater carbonate chemistry, offering insights into global carbon cycle models and providing a new proxy record of seawater chemistry. The findings indicate that shifts in the global and temporal abundances of tepee structures and pisoids are correlated with changes in seawater chemistry due to tectonics and biotic innovation.