Three distinct detrital shocked zircon age populations at 3104 Ma, 3065 Ma and 2867 Ma were identified. Apparent ages of detrital shocked monazite range from 3044 Ma to 2157 Ma, including two groupings at 2640 Ma and 2454 Ma. The Vredefort impact event does not appear to have caused significant Pb-loss for the majority of the grains; Neoproterozoic lower concordia intercepts (1093-751 Ma) in the zircon populations indicate most Pb-loss occurred during the Kibaran orogeny in southern Africa.
This study demonstrates that shocked minerals survive long distances (at least 750 km) of transport within fluvial environments, and can be correlated to known bedrock localities using U-Th-Pb dating. The implications of these results are: (1) detrital shocked minerals within modern sediments can be used to identify the existence of an impact structure; geochronology of shocked zircon and monazite can provide target bedrock ages and metamorphic history that can constrain the location of the structure. (2) The persistence of ancient shocked zircon in modern fluvial sedimentary systems suggests that a detrital shocked mineral record of early impact events on Earth may be preserved in siliciclastic sedimentary rocks.