Eocene Thermal Maximum 3

ETM3 has been dated to about 52.5 Ma.^[1] It is demarcated in the chronostratigraphic record by a marked negative δ¹³C and δ¹⁸O excursion.^[2]

ETM3 was caused by a massive input of isotopically light carbon into the atmosphere. It has been suggested that methane hydrate reservoirs, recharged over millennia after melting during previous Eocene hyperthermals, were the source of this light carbon during ETM3.^[3]