A plant-wax δD record of palaeohydrology over the Cretaceous–Paleogene boundary

Alongside the mass extinction, the Cretaceous–Paleogene (K–Pg) boundary interval experienced major climate perturbations due to the Chicxulub meteorite impact and Deccan Trap volcanism. The volcanism and release of climate modifying gases likely had a drastic effect on global climate, though hypotheses of this change remain largely untested.

Recent work applied the lipid biomarker palaeotemperature proxy MBT'5me to two highly chronologically constrained lignites from the Western Interior, USA (palaeolatitudes 45–51°N). This reconstruction showed that mean annual air temperatures increased by 3°C during the last ~100 ka of the Cretaceous, likely driven by Deccan volcanism and long-term release of organic carbon into the atmosphere. A transient cooling event of up to 5°C is superimposed on to the longer-term warming trend, beginning ~35 ka before the K–Pg boundary. This cooling coincided with the second (Poladpur) eruptive phase of Deccan volcanism, which correlates with the modelled climatic cooling predicted by the release of associated aerosolised SO₂ emissions.

To gain a more holistic understanding of the end-Cretaceous climate system, here we use the hydrogen-isotope composition of plant-wax from the same lignites to reconstruct palaeohydrology. Determining the link between volcanism-induced temperature change and hydrology prior to the Chicxulub impact will provide a framework for understanding post-impact hydrological changes.

This work presents the first opportunity to evaluate palaeohydrology at a millennial scale in the Cretaceous, alongside temperature and carbon-cycling. Further, the excellent chronological constraints allow a unique insight into the relative timing of different climatic processes and major climate perturbations in the lead-up to and across the K–Pg boundary.