RE: Methane concentrations23 Feb 2024 13:50
I don't think the biogenic necessarily has to be newer although generally it is.
From my understanding it could've been formed when those layers were shallower and then was sealed off.
I've got an itch pointing towards messinian salinity crisis.
Methanogenesis in hypersaline environments is determined by redox potential and permanency of anaerobic conditions, and by the concentration of other terminal electron acceptors, particularly sulfate, because sulfate-reducing bacteria have a greater affinity than methanogens for competitive substrates like hydrogen and acetate. Hypersalinity, however, is not an obstacle to methanogenesis; in many cases it provides higher concentrations of non-competitive substrates like methylamines, which derive from compatible solutes such as glycine-betaine that is synthesized by many microbes inhabiting hypersaline environments. Also, depletion of sulfate, as may occur in deeper sediments, allows increased methanogenesis
No idea how this fits in. Paul should do an interview.