Abstract Detail

Plants at the Cretaceous-Paleogene boundary

Stiles, Elena [1], Wilf, Peter [2], Iglesias, Ari [3], Gandolfo, Maria A [4], Cuneo, Nestor [5].

Quantifying macrofloral extinction and morphological diversity across the K-Pg boundary in Argentine Patagonia.

The response of Southern Hemisphere floras to the Cretaceous-Paleogene (K-Pg) meteorite impact and mass extinction 66 million years ago is poorly understood compared to the Northern Hemisphere. The catastrophic atmospheric and environmental consequences of this worldwide major event resulted in extinction rates of 30% for microfloras and 57% for macrofloras in the western interior of North America where the vast majority of K-Pg Northern Hemisphere localities is reported. Leaf collections including over 4,000 specimens from well-dated strata of the latest Cretaceous (Maastrichtian) Lefipán Fm. (66-67 Ma) and earliest Paleogene (Danian) Salamanca and Peñas Coloradas fms. (65.7-62.2 Ma) in Argentine Patagonia offer a unique opportunity to quantify macrofloral K-Pg turnover for the first time in the Southern Hemisphere. Morphospace analysis is used to search for possible survivor pairs and track changes in morphological diversity across the K-Pg boundary. Each morphotype in the Maastrichtian-Danian collection is described by a set of discrete leaf architectural characters summarizing its shape, size, and venation patterns. This dataset is plotted into a multivariate morphospace where the pairwise dissimilarity between morphotypes can be observed as the graphical distance between them. The ordination distances between morphotypes in the space are used not only to narrow down the possible survivor pairs but to track changes in morphological diversity across the K-Pg boundary. Morphospace analysis indicates that age is a strong factor, with Maastrichtian and Danian leaves occupying distinct morphological spaces and higher morphological diversity in the Danian following the K-Pg. Further inspection of this pattern reveals that untoothed and unlobed leaves dominate in the Maastrichtian, whereas toothed and lobed leaves dominate in the Danian. The increased proportion of lobed and toothed leaves in the early Danian indicates cooler temperatures than in the terminal Maastrichtian. These results suggest a relative net cooling occurring between late Cretaceous and early Paleogene of Argentine Patagonia.

1 - Pennsylvania State University, Geosciences, 335 Deike, University Park, PA, 16802, USA
2 - Pennsylvania State University, Geosciences, 537 Deike Bldg., University Park, PA, 16802, United States
3 - Universidad Nacional del Comahue, Geosciences, San Carlos de Bariloche, Rio Negro, Argentina
4 - Cornell University, L.H. Bailey Hortorium, Section Of Plant Biology, 410 Mann Library Building, Ithaca, NY, 14853.0, United States
5 - MEF, Mef Av. Fontana 140, Trelew-Chubut, U, 9100, Argentina

Keywords:
Cretaceous-Paleogene boundary 
extinction
Gondwana
Leaves
Morphospace.

Presentation Type: Colloquium Presentations
Session: C01, Plants at the Cretaceous-Paleogene boundary
Location: 101/Mayo Civic Center
Date: Monday, July 23rd, 2018
Time: 9:00 AM
Number: C01005
Abstract ID:343
Candidate for Awards:None