Shallow-water hydrothermal venting linked to the Palaeocene-Eocene Thermal Maximum

Widespread shallow-water hydrothermal venting in the North Atlantic, probably a source of methane, coincided with the onset of the Palaeocene-Eocene Thermal Maximum, according to borehole proxy records and seismic imaging. The Palaeocene-Eocene Thermal Maximum (PETM) was a global warming event of 5-6 & DEG;C around 56 million years ago caused by input of carbon into the ocean and atmosphere. Hydrothermal venting of greenhouse gases produced in contact aureoles surrounding magmatic intrusions in the North Atlantic Igneous Province have been proposed to play a key role in the PETM carbon-cycle perturbation, but the precise timing, magnitude and climatic impact of such venting remains uncertain. Here we present seismic data and the results of a five-borehole transect sampling the crater of a hydrothermal vent complex in the Northeast Atlantic. Stable carbon isotope stratigraphy and dinoflagellate cyst biostratigraphy reveal a negative carbon isotope excursion coincident with the appearance of the index taxon Apectodinium augustum in the vent crater, firmly tying the infill to the PETM. The shape of the crater and stratified sediments suggests large-scale explosive gas release during the initial phase of vent formation followed by rapid, but largely undisturbed, diatomite-rich infill. Moreover, we show that these vents erupted in very shallow water across the North Atlantic Igneous Province, such that volatile emissions would have entered the atmosphere almost directly without oxidation to CO2 and at the onset of the PETM.

Automated summary

Widespread shallow-water hydrothermal venting in the North Atlantic, probably a source of methane, coincided with the onset of the Palaeocene-Eocene Thermal Maximum. This venting occurred around 56 million years ago and was caused by carbon input into the ocean and atmosphere, leading to a global warming event. The vents erupted in shallow water, resulting in the direct release of volatile emissions without oxidation to CO2, and played a key role in the carbon-cycle perturbation.