Age model and elemental data of DSDP Holes 48-401 and 80-549

Sites 401 and 549 confirms that the majority of NAIP volcanism occurred as subaerial flows. Thus the trace element records provide constraints on the nature and scope of the environmental impact of the NAIP during the late Paleocene–early Eocene interval. Subaerial volcanism would have injected mantle CO2 directly into the atmosphere, resulting in a more immediate increase in atmospheric greenhouse gas abundances than CO2 input through submarine volcanism.

The lack of significant hydrothermalism contradicts recently proposed mechanisms for thermally destabilizing methane hydrate reservoirs during the PETM. Any connection between NAIP volcanism and PETM warming had to occur through the atmosphere.