The K–Pg boundary is dated to 66.043 ± 0.043 Ma
Renne and colleagues published high-precision argon-40/argon-39 ages for tektites from the impact ejecta and for volcanic ash beds bracketing the boundary in terrestrial sections, placing the Cretaceous–Palaeogene boundary at 66.043 ± 0.043 million years and showing that the impact and the boundary are indistinguishable in time to within about thirty thousand years. The result also moved the boundary about half a million years younger than the previously accepted 65.5 Ma figure — an example of a date changing not because new rock was found but because the argon system was recalibrated against uranium–lead. The precision matters for the argument: an impact separated from the extinction by even a few hundred thousand years would be a coincidence rather than a cause.
Historical — it happened, and the record is settled.
Subjects
- Radiometric dating · process · not located
- Chicxulub impact crater, Yucatán · impact crater · Mexico
Evidence
Partly verified — Core facts are sourced; some optional detail is deliberately absent.
Time Scales of Critical Events Around the Cretaceous–Paleogene Boundary
Supports the boundary age of 66.043 ± 0.043 Ma and the finding that the Chicxulub impact and the extinction horizon are indistinguishable in time. V55 verification basis: this session had no network access to any source — WebFetch was egress-blocked and the WebSearch budget was exhausted — so the cited work was not retrieved and its pagination was not re-checked. Volume and page range are quoted from standing knowledge and were not re-checked.
Science · 2013 · Partly verified
Renne, P. R. et al., Science, vol. 339 (2013), pp. 684–687
Recorded on Radiometric dating
Related
Related because they share a subject in the Atlas — never because the text looks similar.