JOHN F. LERBEKMO, ARTHUR R. SWEET, ROBERT M. ST. LOUIS; The relationship between the iridium anomaly and palynological floral events at three Cretaceous-Tertiary boundary localities in western Canada. GSA Bulletin ; 99 (3): 325–330. doi: https://doi.org/10.1130/0016-7606(1987)99<325:TRBTIA>2.0.CO;2
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Profiles illustrating the abundance of iridium and the changes in the relative abundances of major groups within the palynoflora are given for three localities from western Canada. The peak abundance of iridium ranges from 1.35 to 5.60 ppb and corresponds to the base of a coal and to a floral-extinction event at the three localities. Immediately above the iridium-peak anomaly, angiosperm pollen is conspicuous in the assemblage, in contrast to the fern-spore spike described for sections in the mid-continental United States and at the Morgan Creek locality in south-central Saskatchewan.