Exploring a link between the Middle Eocene Climatic Optimum and Neotethys continental arc flare-up

The Middle Eocene Climatic Optimum (MECO), a similar to 500 kyr episode of global warming that initiated at similar to 40.5 Ma, is postulated to be driven by a net increase in volcanic carbon input, but a direct source has not been identified. Here we show, based on new and previously published radiometric ages of volcanic rocks, that the interval spanning the MECO corresponds to a massive increase in continental arc volcanism in Iran and Azerbaijan. Ages of Eocene igneous rocks in all volcanic provinces of Iran cluster around 40 Ma, very close to the peak warming phase of the MECO. Based on the spatial extent and volume of the volcanic rocks as well as the carbonaceous lithology in which they are emplaced, we estimate the total amount of CO2 that could have been released at this time corresponds to between 1052 and 12 565 Pg carbon. This is compatible with the estimated carbon release during the MECO. Although the uncertainty in both individual ages, and the spread in the compilation of ages, is larger than the duration of the MECO, a flare-up in Neotethys subduction zone volcanism represents a plausible excess carbon source responsible for MECO warming.

Automated summary

The Middle Eocene Climatic Optimum (MECO) was a period of global warming lasting about 500 kyr, with an increase in volcanic activity in Iran and Azerbaijan identified as a potential excess carbon source responsible for the warming. The estimated CO2 release during this time period is thought to align with the warming trends observed during the MECO.