Based on extraterrestrial chromite grains (63−355 μm) in late Eocene sediments, the Chesapeake Bay impact crater (northeastern United States; 40−85 km diameter) likely formed from an H-chondritic projectile. This impact occurred 10−20 k.y. after the formation of the Popigai crater (Siberia, Russia; ∼100 km). The craters formed at the peak of a 2-m.y. period with a factor of 3−5 enhanced flux of 3He-rich extraterrestrial fine dust to Earth. The Massignano and Monte Vaccaro sections in Italy provide detailed sedimentary records of these events. Previous data from 1168 kg of acid-dissolved limestone at Massignano combined in the present study with 1663 kg of limestone from Monte Vaccaro, spanning the 3He anomaly, reveal a persistent decimeter-thick layer enriched in H-chondritic chromite grains at the stratigraphic level of the Chesapeake Bay impact. These well-preserved grains, free of shock features, likely were released from the regolith of the impactor as it approached Earth. We also report that the small Ir anomaly at the 6.19 m level at Massignano is not reproducible at Monte Vaccaro and may reflect diagenesis or reworking. We revise earlier interpretations and suggest that the late Eocene 3He and chromite anomalies, along with the two large impacts, likely relate to a major breakup event within the Koronis asteroid family, the source of today’s common H chondrites.

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