Asteroids and crustal evolution

Uniformitarian models for the early Earth take little or no account of repeated impacts of asteroid clusters and their effects on crust and mantle. However a growing body of evidence exists for multiple impacts by bodies on the scale of tens of kilometer during ~3.47–2.48 Ga, likely accounting at least in part for mafic-ultramafic volcanism produced by mantle rebound and melting events, consistent with the original suggestion by Green (Earth Planet Sci Lett 15:263–270, 1972, Precambrian plate tectonics. Elsevier, Amsterdam, pp 469–489, 1981). Further, the juxtaposition of at least four impact ejecta units with the fundamental unconformity between granite-greenstone terrains and semi-continental deposits in both the Barberton Greenstone Belt and the Pilbara Craton about ~3.26–3.227 Ga constitutes a primary example for the tectonic and magmatic effects of asteroid impact clusters in the Archaean, supporting Lowe and Byerly (Did the LHB end not with a bang but with a whimper? 41st Lunar Planet Science Conference 2563pdf, 2010) suggested extension of the late heavy bombardment (LHB).