148-6 Palynofloral Composition of Polar and Mid-Latitude Samples from the Paleocene-Eocene of North America

Session: Insights from Microfossils and Their Modern Analogs: From Traditional to Emerging Approaches (Posters)

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Here we assess floral composition and infer paleoclimate from fossilized pollen occurring in late Paleocene to early Eocene samples from middle and high paleolatitudes of North America. This was the warmest interval of the Cenozoic, so we expect thermophilic plants to attain their highest paleolatitudinal distributions, especially during the early Eocene. We examined four samples: two from the Paleocene (Arkansas and Alaska) and two from the early-middle Eocene (Arkansas and Canada). For each slide, two randomly selected 3.81 mm² regions were examined. Pollen grains were identified using published literature and, when possible, associated with their nearest living relatives. In total, 903 pollen grains were identified. Plant families found in all samples include Cupressaceae (bald cypress relatives), Arecaceae (palms), Fagaceae (oak family), Juglandaceae (walnut family), and Betulaceae (birch family). The sample from the Paleocene of Alaska (paleolatitude 80N) was dominated by Pinaceae and ferns, suggesting a temperate forest. The Eocene sample from Canada (paleolatitude 66N) contained temperate taxa such as Platycarya and Anacardiaceae, but also tropical elements such as Bombacoideae. The Paleocene of Arkansas (36N) we interpret as a warm-temperate to subtropical forest, uniquely featuring Asteraceae and Ericaceae. The Eocene sample from Arkansas (34N) included humid, warm-temperate to marginally subtropical taxa (e.g., Platycarya), as well as tropical Bombacoideae. These findings are consistent with the temperature increase from the late Paleocene to early Eocene based on marine oxygen isotope compilations. The presence of Arecaceae and Bombacoideae in the Eocene sample from Canada, far from the Arctic Sea coast, suggests warm winters (>~5 °C Cold Month Mean), as living relatives are not able to survive prolonged subfreezing temperatures. The mild high latitude winters of the early Eocene facilitated the poleward migration of tropical taxa. Although the number of samples in this study was small, the results highlight the importance of refining climatic models with terrestrial plant records. These results are part of a larger study developed on a continental scale to not only understand floral composition through the latitudinal gradient, but also to test paleoclimate models.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9553

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