Are Early Paleocene hyperthermals a legacy of the Cretaceous/Paleogene mass extinction?

The Late Paleocene-Early Eocene is well known as a time interval of greenhouse conditions. Superimposed on these conditions is a series of transient global warming events, including the Paleocene-Eocene Thermal Maximum (PETM at ~56 Ma), the Eocene Thermal Maximum 2 (ETM2 at ~54 Ma), and ETM3 at ~52.8 Ma, alongside other smaller-scale events. These events, collectively known as hyperthermals, were caused by the release of massive amounts of isotopically light carbon into the exogenic pool - as revealed by negative carbon isotope excursions (CIEs) - leading to global warming and ocean acidification. Hyperthermals were likely triggered by crossing thermodynamic thresholds for carbon release from several potential sources, often in response to orbital forcing, although a volcanic origin for the PETM cannot be excluded. While Late Paleocene-Early Eocene hyperthermals are well documented in both marine and terrestrial sedimentary archives, the recent acquisition of well-resolved records from oceanic cores and land sections has revealed the occurrence of carbon cycle aberrations, potentially representing hyperthermal events also during the early Paleocene. In particular, several events of concomitant shoaling of the lysocline/CCD, as reflected in CaCO3-depleted intervals and negative CIEs, are observed at various sites, including South Atlantic ODP Site 1262, the Bottaccione-Contessa record in Central Italy, the Zumaia section (Spain), and Equatorial Pacific ODP Site 1209. Similar to the Late Paleocene-Early Eocene hyperthermals, these events are associated with maximal astronomical forcing, occurring in correspondence with short- and long-eccentricity maxima. Notably, these events are absent in the Maastrichtian, suggesting that the bolide impact and the major mass extinction marking the Cretaceous/Paleogene boundary may have led to profound changes in the marine carbon cycle and its sensitivity to astronomical forcing.