XAFS study of Zr in Cretaceous–Tertiary boundary clays from Stevns Klint

A groundbreaking study reveals that zirconium (Zr) in Cretaceous–Tertiary boundary clays from Stevns Klint, Denmark, retains structural signatures of thermal quenching linked to a meteorite impact. Using Zr K-edge X-ray absorption fine structure (XAFS), researchers found that the Zr-O bonding distance and coordination number closely resemble those in rhyolitic volcanic glass and tektites—materials formed during high-temperature, reductive conditions. Notably, the partial reduction of zirconium ions (Zr^3.8+–3.9+) suggests rapid cooling after formation, preserving unique chemical states absent in natural glasses. This discovery offers a novel method to identify sedimentary rocks deposited during extinction events by analyzing Zr's local structure, providing critical insights into the environmental conditions following catastrophic impacts.

TOBASE, T., YOSHIASA, A., WANG, L., HIRATOKO, T., HONGU, H., OKUBE, M., & SUGIYAMA, K. (2015). XAFS study of Zr in Cretaceous–Tertiary boundary clays from Stevns Klint. Journal of Mineralogical and Petrological Sciences, 110(2), 88–91. https://doi.org/10.2465/jmps.141022a