Deep sea

Quantum mechanics

Methane

Isotopes of carbon

Ecology

Biology

Carbon cycle

Dissociation (chemistry)

Glacial period

Geology

Oceanography

Physical chemistry

Paleontology

Thermodynamics

Physics

Organic chemistry

Total organic carbon

Environmental chemistry

Hydrostatic pressure

δ13C

Hydrostatic equilibrium

Chemistry

Stable isotope ratio

Clathrate hydrate

Seawater

Hydrate

Ecosystem

Nature Geoscience

Methane hydrate dissociation has long been considered as a mechanism for global carbon cycle perturbations, climate change and even mass extinctions in Earth’s history. However, direct evidence of hydrate destabilization and methane release coinciding with such events is scarce. Here we report the presence of diagnostic lipid biomarkers with depleted carbon isotopes from three sites in the Southern Ocean that are directly linked to methane release and subsequent oxidation across the Oligocene–Miocene boundary (23 million years ago). The biomarker evidence indicates that the hydrate destabilization was initiated during the peak of the Oligocene–Miocene boundary glaciation and sea-level low stand, consistent with our model results suggesting the decrease in hydrostatic pressure eroded the base of global methane hydrate stability zones. Aerobic oxidation of methane in seawater consumes oxygen and acidifies the ocean, acting as a negative feedback that perhaps facilitated the rapid and mysterious termination of glaciation in the early Miocene. Methane hydrate dissociation occurred across the Oligocene–Miocene boundary, which may have contributed to the termination of glaciation, according to analysis of lipid biomarkers from the Southern Ocean.

Methane hydrate dissociation across the Oligocene–Miocene boundary