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Faunal evidence for reduced productivity and uncoordinated recovery in Southern Hemisphere Cretaceous-Paleogene boundary sections

¹ Museum für Naturkunde, Humboldt-Universität Berlin, Invalidenstrasse 43, D-10115 Berlin, Germany
² Departamento de Ciencias Geológicas, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, 1428 Buenos Aires, Argentina

The mass extinction at the Cretaceous-Paleogene boundary is generally explained by a severe crisis in primary productivity, following a catastrophic bolide impact. Consistent with this scenario, Danian mollusk-dominated benthic shelf ecosystems of southern middle paleolatitudes (Neuquén Basin, Argentina) are characterized by (1) a stratigraphically limited low in macrofossil abundances; (2) an increase in starvation-resistant, nonplanktotrophic deposit feeders and chemosymbionts; (3) a reduction in the average body size of individuals; and (4) individuals with inactive lifestyles being more common than in the late Maastrichtian. Return to pre-extinction conditions of the various synecological attributes occurred over unequal time spans, indicating that recovery was uncoordinated with respect to ecological traits. Global comparison of ecological patterns suggests that reduced food supply (1) was a controlling factor in both hemispheres; (2) affected macrobenthic marine faunas at various distances from the Chicxulub impact site; and (3) was more effective in siliciclastic environments as compared to oligotrophic carbonate settings.

Key Words: mass extinction • Cretaceous-Paleogene boundary • ecology • productivity • Southern Hemisphere

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