The Palaeocene–Eocene thermal maximum (PETM) is a well-known abrupt warming that occurred at about 55.8 Myr ago and is usually thought to have been caused by a large release of greenhouse gases, as recorded in a large carbon isotope excursion. Yet some marine evidence suggests that in fact the warming came first. Here it is shown that continental warming of about 5 °C preceded the excursion in the Bighorn Basin, Wyoming. Thus the PETM seems to have been caused by at least two separate warming events.
- Ross Secord
- Philip D. Gingerich
- Kenneth G. MacLeod
