MANY lines of evidence now support the identification of the Chicxulub structure, in Mexico, as a buried impact crater and the probable source of ejecta found in Cretaceous/Tertiary (K/T) boundary sections worldwide1–8. The question remains, however, of whether there might be additional craters of K/T age, which also contributed ejecta. Shocked zircons from a K/T ejecta layer in Colorado9 preserve a primary source age of 545 ± 5 Myr, with variable degrees of isotopic resetting consistent with partial lead loss at the time of impact (65 Myr ago)10. Here we report that the impact breccia from Chicxulub contains zircons that are identical in age, texture and lead loss pattern to the Colorado zircons, and to some from the Beloc section in Haiti. U–Pb data for 18 of the 36 grains studied (from all three sites) fall on a single line as well as if they had come from a single sample. An additional source age of 418 ±6 Myr is found only in Chicxulub and Haiti, suggesting that the Haiti and Colorado ejecta might have sampled different parts of the target stratigraphy. As all the ejecta ages found so far are also found at Chicxulub, our results are consistent with this being the only significant continental K/T impact crater.
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Krogh, T., Kamo, S., Sharpton, V. et al. U–Pb ages of single shocked zircons linking distal K/T ejecta to the Chicxulub crater. Nature 366, 731–734 (1993). https://doi.org/10.1038/366731a0
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