Evidence for natural molecular hydrogen seepage associated with Carolina bays (surficial, ovoid depressions on the Atlantic Coastal Plain, Province of the USA)

A study of soil gases was made in North Carolina (USA) in and around morphological depressions called Carolina bays. This type of depression is observed over the Atlantic coastal plains of the USA, but their origin remains debated. Significant concentrations of molecular hydrogen (H-2) were detected, notably around the bays. These measurements suggest that Carolina bays are the surficial expression of fluid flow pathways for hydrogen gas moving from depth to the surface. The potential mechanisms of H-2 production and transport and the geological controls on the fluid migration pathways are discussed, with reference to the hypothesis that Carolina bays are the result of local collapses caused by the alteration of rock along the deep pathways of H-2 migrating towards the surface. The present H-2 seepages are comparable to those in similar structures previously observed in the East European craton.