The age of the Popigai impact event and its relation to events at the Eocene/Oligocene boundary

Ages ranging from the Late Cretaceous (∼65 Myr) to the Oligocene (∼29 Myr) have been reported for the 100-km-diameter Popigai impact structure on the Anabar shield, central Siberia. These ages overlap the timing of several possible impact-related features, including the Cretaceous/Tertiary and Eocene/Oligocene stratigraphic boundaries, the North American tektites, and the recently reported occurrences of an iridium anomaly and shocked quartz in Late Eocene deposits in northern Italy. Here we report age determinations of several Popigai impact melt rocks using the 40Ar-39Ar step heating technique to constrain the age of the impact event. Our results are consistent with a Late Eocene impact age of 35.7± 0.2 Myr (2σ)-coincident in time with the impact deposits found in Italy. As this age is also similar to that of the North American tektites, which have been associated with the Chesapeake Bay impact structure in the eastern United States, there seem to have been at least two large and essentially contemporaneous impacts during the Late Eocene.