Abstract Detail

Paleobotany

Cleveland, Claire [1].

What are early signals of Patagonian paleofloral response to Eocene cooling and initial stages of South America’s separation from Antarctica?

Fossil floras from South America, Antarctica, Australia, and New Zealand support an extended rainforest biome spanning much of the Late Cretaceous Southern Hemisphere. However, global cooling and separation of South America from Antarctica resulted in significant climatic and ecological change in Paleogene Patagonia. Fossil floras from Rió Pichileufú (RP) and Laguna del Hunco (LH) in Patagonia, South America, provide a unique opportunity for comparative analysis of two fossil floras bracketing the Early Eocene Climatic Optimum. LH (52.22 ±0.22 Ma) and RP (47.74 ±0.05 Ma), separated by just 4.5 Ma and 160 km, share significant similarities. Both fossil floras were quarried from tuffaceous caldera-lake sediments in the Huitrera Formation less than 15° latitude north of the Drake Passage. Research in the literature indicates that although many plant taxa are found at both sites, including Dacrycarpus and Agathis, RP lacks many of the taxa observed at LH, including Eucalyptus and Gymnostoma. Additionally, new taxa observed at RP are not represented at LH, including the oldest known macrofossil of Asteraceae. Qualitative evidence from EW Berry’s 1938 RP type and cohort collection at the National Museum of Natural History, will be considered with quantitative evidence from recent RP collections at the Museo Paleontologico Egidio Feruglio in Trelew, Argentina. Through multivariate analysis of composition and relative abundance, the recent RP collection and published LH data sets will be compared in the context of the earliest stages of biogeographic isolation of South America, change from greenhouse to icehouse conditions, and signals of refugium versus extirpation. I predict that net loss of ancient Gondwanan rainforest associations and net gain of new occurrences, as well as shifts in relative abundance, will be observed through comparison of the recent RP and LH fossil collections. This research may help provide insights into early transition from Old World Gondwanan rainforest assemblages to New World Patagonian floral assemblages.

1 - Pennsylvania State University, Geosciences, 236 Deike Building, University Park, PA, 16802, USA

Keywords:
Patagonia
Gondwana
Eocene
refugium
Paleogene
Cenozoic.

Presentation Type: Poster
Session: P, Paleobotanical Section Posters
Location: Exhibit Hall/Savannah International Trade and Convention Center
Date: Monday, August 1st, 2016
Time: 5:30 PM This poster will be presented at 5:30 pm. The Poster Session runs from 5:30 pm to 7:00 pm. Posters with odd poster numbers are presented at 5:30 pm, and posters with even poster numbers are presented at 6:15 pm.
Number: PPB003
Abstract ID:804
Candidate for Awards:None