Impact of the Cretaceous-Paleogene event on sedimentary organic matter in southern high-latitude regions

Abstract

The Cretaceous–Paleogene (K/Pg) boundary marks one of Earth’s significant mass extinctions, disrupting terrestrial and marine ecosystems. We investigate sedimentary organic matter and geochemical proxies from two high-latitude K/Pg sections: El Puesto (continental, Chilean Patagonia) and Filo Negro (marine, Seymour Island, Antarctica). Despite contrasting depositional settings, both sections reveal that the most consistent signal associated with the iridium anomaly is a marked increase of plant tissue amorphous organic matter (PT-AOM), formed by the biodegradation of terrestrial vegetation. This pattern shows how the collapse of continental ecosystems left a strong imprint on both continental and marine records. Geochemical proxies provide further evidence of synchronous stress. Elemental ratios indicate shifts in terrigenous input, hydrological balance, productivity, and redox conditions, while Hg anomalies normalized to organic carbon support an external volcanic contribution contemporaneous with the impact. These multiproxy signals demonstrate how global perturbations were expressed differently across depositional environments, yet carried the same fundamental fingerprint. Our findings show that even in high latitudes, ecosystems experienced profound disturbances at the K/Pg boundary. The convergence of palynofacies and geochemical evidence underscores the global reach of the event and identifies PT-AOM as a key marker of ecosystem disruption during one of Earth’s most dramatic biotic crises.