Geochemical and paleontological evidence indicate that marine primary productivity decreased rapidly at the Cretaceous-Tertiary boundary resulting in the selective elimination of those organisms directly dependent upon the flux of organic matter as a food source (filter and suspension feeders). Detritus and deposit feeders, however, suffered relatively fewer extinctions, apparently utilizing the reservoir of organic matter stored within the sediments. Lower rates of oceanic productivity might have continued for at least 1.5 m.y. following the initial decrease despite the rapid evolution of fauna and flora during the early Paleocene. Although these results can be viewed as being compatible with the bolide impact hypothesis, the extended period of low productivity afterwards suggests some longer term effects on the biosphere than predicted by such a model.
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