Combined osmium and strontium isotopic study of the Cretaceous-Tertiary boundary at Sumbar, Turkmenistan: A test for an impact vs. a volcanic hypothesis Available to Purchase

Osmium and strontium isotopic ratios at the Cretaceous-Tertiary boundary at Sumbar, Turkmenistan, display a negative hyperbolic covariation superimposed on the long-term trend, which displays a positive covariation. The minimum ratio for Os and the maximum ratio for Sr occur at the boundary clay. Volcanism with a mantle or crustal source cannot account for the isotopic data. The low ¹⁸⁷-O_s/¹⁸⁸-O_s and the high ⁸⁷-Sr/⁸⁶-Sr ratios can be explained by an impact, whereby Os was derived from the bolide and the ⁸⁷Sr/⁸⁶Sr ratio was enhanced by acid rain and/or a tsunami following the event.