Should add that constraints on d13C of source for PETM are getting better. eg https://www.pnas.org/content/117/39/24088 - favouring volcanic (-6) rather than coal (-25) or gas (-60).
Should add that constraints on d13C of source for PETM are getting better. eg https://www.pnas.org/content/117/39/24088 - favouring volcanic (-6) rather than coal (-25) or gas (-60).