Abstract Detail

Paleobotany

Wilson, Paige K. [1], Stromberg, Caroline [2], Wilson Mantilla, Gregory [3].

Plant Community Turnover at the Cretaceous-Paleogene (K/Pg) Boundary in Northeastern Montana.

The Cretaceous-Paleogene (K/Pg) boundary is marked by a major mass extinction resulting in global biotic turnover, notably the extinction of non-avian dinosaurs. The Hell Creek Area in northeastern Montana contains some of the best-studied vertebrate fossil localities recording this mass extinction; however, very little is known about floral changes in this area. This study presents data from a sequence of macrofloral assemblages spanning approximately 2 m.y. around the K/Pg boundary to examine the pattern and magnitude of extinction among plants. We test the hypotheses that a) plant communities experienced large turnover coincident with the K/Pg boundary and b) plant communities in the aftermath of the mass extinction were homogeneous and depauperate. Each site preserves leaves, reproductive structures, and other vegetative structures. These fossils are recovered from siltstone and sandstone lithologies, interpreted as riparian depositional environments. Our results indicate that many of these floras have taxa in common (e.g., Metasequoia occidentalis, Glyptostrobus europaeus, and Zizyphoides), but overall preserve distinct plant communities through time. Vegetation through the latest Cretaceous was diverse and variable, suggestive of landscape heterogeneity, changing plant communities through time, or both. While diversity remained relatively stable into the Paleogene, there is large taxonomic turnover between latest Cretaceous and earliest Paleogene plant communities. We estimate that greater than 68% of Cretaceous plant taxa disappeared just before or at the K/Pg boundary. Earliest Paleogene floras were relatively homogeneous, with common Late Cretaceous taxa remaining present, if rare. We further compare our floras to contemporaneous records from other areas of the Western Interior to examine whether extinction and recovery patterns varied regionally. Overall, this record of plant communities lends insight into the dynamics of Late Cretaceous ecosystems, plant community change across the K/Pg boundary, and variation between regional floras of the northern Great Plains region.

1 - University of Washington, Earth and Space Sciences, Johnson Hall Rm-070, Box 351310, 4000 15th Avenue NE, Seattle, WA, 98195, USA
2 - University Of Washington, Department Of Biology, Life Sciences Building, Box 351800, Seattle, WA, 98195, United States
3 - University Of Washington, Department Of Biology, Life Sciences Building, Box 351800, Seattle, WA, 98195, USA

Keywords:
Paleobotany
Cretaceous
K-Pg.

Presentation Type: Oral Paper
Session: PL1, Paleobotany: Cookson Student Presentations - Session I
Location: /
Date: Monday, July 19th, 2021
Time: 11:00 AM(EDT)
Number: PL1005
Abstract ID:882
Candidate for Awards:Isabel Cookson Award