The environmental disaster of Aznalcóllar (southern Spain) as an approach to the Cretaceous-Palaeogene mass extinction event

Bottom-water conditions in a marine basin after the Cretaceous-Paleogene impact event: timing the recovery of oxygen levels and productivity

An ultra-high-resolution analysis of major and trace element contents from the Cretaceous–Paleogene boundary interval in the Caravaca section, southeast Spain, reveals a quick recovery of depositional conditions after the impact event. Enrichment/depletion profiles of redox sensitive elements indicate significant geochemical anomalies just within the boundary ejecta layer, supporting an instantaneous recovery –some 10² years– of pre-impact conditions in terms of oxygenation. Geochemical redox proxies point to oxygen levels comparable to those at the end of the Cretaceous shortly after impact, which is further evidenced by the contemporary macrobenthic colonization of opportunistic tracemakers. Recovery of the oxygen conditions was therefore several orders shorter than traditional proposals (10⁴–10⁵ years), suggesting a probable rapid recovery of deep-sea ecosystems at bottom and in intermediate waters.