spherule

They were looking for spherule particles, or tiny fragments of rock, left behind by impact.

Within two hours of my arrival, we had recovered one such spherule, a few hundred microns in size, from a sample collected along the strip that I had calculated to be the most likely airburst location for IM1.

He worries that only two spherule beds match the crystal data, and one of those beds is not located within Australia—meaning that the timing might not match after all.

Evidence for the theory can be found not just within the crystals but also in areas called spherule beds.

Rasmussen, B., Blake, T. S. & Fletcher, I. R. U–Pb zircon age constraints on the Hamersley spherule beds: evidence for a single 2.63 Ga Jeerinah-Carawine impact ejecta layer.