Charcoal evidence that rising atmospheric oxygen terminated Early Jurassic ocean anoxia.

ABSTRACT: The Toarcian Oceanic Anoxic Event (T-OAE) was characterized by a major disturbance to the global carbon(C)-cycle, and depleted oxygen in Earth's oceans resulting in marine mass extinction. Numerical models predict that increased organic carbon burial should drive a rise in atmospheric oxygen (pO₂) leading to termination of an OAE after ?1?Myr. Wildfire is highly responsive to changes in pO₂ implying that fire-activity should vary across OAEs. Here we test this hypothesis by tracing variations in the abundance of fossil charcoal across the T-OAE. We report a sustained ?800?kyr enhancement of fire-activity beginning ?1?Myr after the onset of the T-OAE and peaking during its termination. This major enhancement of fire occurred across the timescale of predicted pO₂ variations, and we argue this was primarily driven by increased pO₂. Our study provides the first fossil-based evidence suggesting that fire-feedbacks to rising pO₂ may have aided in terminating the T-OAE.

SUBMITTER: Baker SJ 

PROVIDER: S-EPMC5437290 | biostudies-literature | 2017 May

REPOSITORIES: biostudies-literature