Carbon cycle was already disrupted millions of years ago

Dutch researcher Yvonne van Breugel analysed rocks from seabeds millions of years old. Carbon occurs naturally in two stable forms; atomic mass 12 (99 percent) and atomic mass 13 (1 percent). Episodes in the Jurassic and Cretaceous periods were characterised by a relatively strong increase in 12C. The analyses have shown that this was caused by a sudden large-scale release of carbon from stocks stored in the ocean floor or peats and bogs.