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Double impact at K-T boundary ?

Geology 2010; 38: 835-38        doi: 10.1130/G31034.1 


The end-Cretaceous mass extinction has been attributed by most to a single 
asteroid impact at Chicxulub on the Yucatán Peninsula, Mexico. The discovery 
of a second smaller crater with a similar age at Boltysh in the Ukraine has 
raised the possibility that a shower of asteroids or comets impacted Earth 
close to the Cretaceous-Paleogene (K-Pg) boundary. Here we present 
palynological and delta-13C evidence from crater-fill sediments in the . Our 
analyses demonstrate that a post-impact flora, formed on the ejecta layer, was 
in turn devastated by the K-Pg event. The sequence of floral recovery from the 
K-Pg event is directly comparable with that in middle North America. We 
conclude that the Boltysh crater predated Chicxulub by ~ 2-5 k.y., a time 
scale that constrains the likely origin of the bodies that formed the two 
known K-Pg craters.

Interestingly a double impact was proposed by Wolfe in 1991

Palaeobotanical evidence for June 'impact winter' at the Cretaceous/Tertiary 
boundary, Nature 1991; 352: 420-2