“To this day, scientists know of only two layers of sediment 'broadly distributed across several continents that exhibit coeval abundance peaks in a comprehensive assemblage of cosmic impact markers, including nanodiamonds, high-temperature quenched spherules, high-temperature melt-glass, carbon spherules, iridium and aciniform carbon.'
These layers are found at the Cretaceous-Paleogene Boundary 65 million years ago, when it has long been agreed that a gigantic cosmic impact in the Gulf of Mexico caused the mass extinction of the dinosaurs, and at the Younger Dryas Boundary 12,800 years ago.”