In the Greenland ice core studied by Harvard researchers, platinum concentration increased by more than a hundredfold over roughly 20 years before subsiding.
Notes on verification
Confirmed by the original 2013 PNAS study (Petaev et al.) and corroborated by independent reporting (Phys.org) and a peer-reviewed follow-up (Kennett et al., PMC5343653) detailing the ~14-year rise and ~7-year decline in platinum concentration.
Sources
- Did a Comet Really Kill the Mammoths 12,900 Years Ago? (nationalgeographic.com)
- https://www.pnas.org/doi/10.1073/pnas.1303924110 (pnas.org)
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5343653/ (ncbi.nlm.nih.gov)