Post-Imbrium Pb-Pb isochron ages for Apollo basaltic impact melt samples 14078 and 68415.

The Apollo 14 and 16 missions returned several samples commonly interpreted as crystalline impact melt, with ages of approximately 3800-3850 Ma. Previous work has suggested that these rocks formed in one or more pre-Imbrium basin forming impact(s). By contrast, recent ages determined for a range of lunar breccias provide compelling evidence that the Imbrium basin was formed at approximately 3920 Ma.

Precise radiometric age establishes Yarrabubba, Western Australia, as Earth's oldest recognised meteorite impact structure.

The ~70 km-diameter Yarrabubba impact structure in Western Australia is regarded as among Earth's oldest, but has hitherto lacked precise age constraints. Here we present U-Pb ages for impact-driven shock-recrystallised accessory minerals. Shock-recrystallised monazite yields a precise impact age of 2229 ± 5 Ma, coeval with shock-reset zircon.