KT/K-Pg Extinction Botanical Turnover In Patagonia

(botanical composition during masstrichtian, earliest danian and late danian)

Cretaceous/Paleogene Floral Turnover in Patagonia: Drop in Diversity, Low Extinction, and a Classopollis Spike

Authors:

1. Viviana D. Barreda (a,*)

2. Nestor R. Cúneo (b)

3. Peter Wilf (c)

4. Ellen D. Currano (d)

5. Roberto A. Scasso (e)

6. Henk Brinkhuis (f)

Affiliations:

a. División Paleobotánica, Museo Argentino de Ciencias Naturales “Bernardino Rivadavia” – CONICET, Buenos Aires, Argentina

b. Museo Paleontológico Egidio Feruglio – CONICET, Trelew, Chubut, Argentina

c. Department of Geosciences, Pennsylvania State University, University Park, Pennsylvania, United States of America

d. Department of Geology and Environmental Earth Science, Miami University, Oxford, Ohio, United States of America

e. Departamento de Geología, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina

f. Institute of Environmental Biology, Faculty of Science, Utrecht University, Utrecht, The Netherlands

* Corresponding Author: (E-mail) vbarreda@macn.gov.ar

Abstract:

Nearly all data regarding land-plant turnover across the Cretaceous/Paleogene boundary come from western North America, relatively close to the Chicxulub, Mexico impact site. Here, we present a palynological analysis of a section in Patagonia that shows a marked fall in diversity and abundance of nearly all plant groups across the K/Pg interval. Minimum diversity occurs during the earliest Danian, but only a few palynomorphs show true extinctions. The low extinction rate is similar to previous observations from New Zealand. The differing responses between the Southern and Northern hemispheres could be related to the attenuation of damage with increased distance from the impact site, to hemispheric differences in extinction severity, or to both effects. Legacy effects of the terminal Cretaceous event also provide a plausible, partial explanation for the fact that Paleocene and Eocene macrofloras from Patagonia are among the most diverse known globally. Also of great interest, earliest Danian assemblages are dominated by the gymnosperm palynomorphs Classopollis of the extinct Mesozoic conifer family Cheirolepidiaceae. The expansion of Classopollis after the boundary in Patagonia is another example of typically Mesozoic plant lineages surviving into the Cenozoic in southern Gondwanan areas, and this greatly supports previous hypotheses of high latitude southern regions as biodiversity refugia during the end-Cretaceous global crisis.