Global carbon cycle disruption during the latest Pliensbachian (Lower Jurassic) evidenced by simultaneous isotopic depletion in marine and terrestrial carbon pools

Highlights

For an approximately 10 Kyr period in the Latest Pliensbachian (in the Early Jurassic), both marine and terrestrial exchangeable carbon reservoirs became isotopically depleted. This is recorded in a thin black shale in the Cleveland Basin (Yorkshire, UK), and was possibly coeval with the Pliensbachian-Toarcian event.

This interval of carbon cycle disruption cannot be tied directly to volcanism since it post-dates a potential geochemical marker for enhanced volcanism by 10 Kyr. The interval was, instead, likely characterised by the collapse of a climatically sensitive methane reservoir, and the consequent release of depleted carbon into the atmosphere.

It is possible that the carbon cycle disruption in the Latest Pliensbachian, while being geologically short-lived, exhausted stabilizing mechanisms within the earth system (e.g. carbon burial), and thus left the planet more vulnerable to the climate change associated with the later Toarcian Oceanic Anoxic Event. This further highlights the long-lasting effects of disruption to the earth system by short, sharp intervals of climate change.