XAFS study of Sb and As in Cretaceous–Tertiary boundary sediments: an index of soiling of the global environment with dust and ashes from impact ejecta falls

Research at Stevns Klint, Denmark, reveals that unusually high concentrations of pentavalent antimony (Sb5+) and arsenic (As5+) in Cretaceous–Tertiary boundary sediments serve as a global environmental indicator. These elements, coprecipitated with iron oxides like ferrihydrite (schwertmannite), suggest widespread contamination by dust and ashes from asteroid impact ejecta falls during this geological transition. The study employed X-ray absorption fine structure (XAFS) spectroscopy to analyze the chemical states and coordination environments of Sb and As, confirming their incorporation into low-crystalline ferrihydrite structures with an Sb–O interatomic distance of 1.99(1) Å. This finding highlights a unique environmental signature in these sediments, distinct from modern soil contamination.

HONGU, H., YOSHIASA, A., TOBASE, T., OKUBE, M., SUGIYAMA, K., & SATO, T. (2019). XAFS study of Sb and As in Cretaceous–Tertiary boundary sediments: an index of soiling of the global environment with dust and ashes from impact ejecta falls. Journal of Mineralogical and Petrological Sciences, 114(5), 224–230. https://doi.org/10.2465/jmps.180927