Global hydrocarbon seep-carbonate precipitation correlates with deep-water temperatures and eustatic sea-level fluctuations since the Late Jurassic

The anaerobic oxidation of methane (AOM) in marine sediments, most obviously at cold seeps, is a major sink for this important greenhouse gas and is associated with the precipitation of carbonates. The geological record of seep carbonates provides insights into the long-term dynamics of this process. Since the Late Jurassic, rates of seep-carbonate precipitation have been high during times of low sea levels and cold deep-water temperatures, and vice versa. One possibility is that sea-level fall decreases the thickness of the methane hydrate stability zone in the sediment so that gas hydrates decompose in deeper sediments, thereby increasing seepage and carbonate precipitation. Alternatively, low deep-water temperature facilitates gas hydrate formation on continental slopes and may thereby increase methane availability for AOM-performing consortia and associated carbonate precipitation. These correlations and their potential causes may be of interest for the modelling of global carbon budgets and of past and future climates.