Reworked pollen reduces apparent floral change during the Paleocene-Eocene Thermal Maximum

Abstract Plant megafossils from the Paleocene-Eocene Thermal Maximum (PETM) in Bighorn Basin, north-central Wyoming, USA, document a dramatic shift floral composition, whereas palynofloral change same sections has appeared to be more subtle. We investigated this discrepancy by quantifying pollen preservation and measuring stable carbon isotope composition of specific taxa. Pollen grains belonging two common latest Paleocene taxa are poorly preserved PETM samples, their δ13Cpollen is similar during PETM. In contrast, thermophilic taxon that became abundant pristine, specimens ∼4‰ lower than specimens. More broadly, lineages currently centered temperate climates when found now tropics well preserved. These differences isotopic indicate extensive redeposition older Increased abundance Cretaceous palynotaxa samples confirms erosion redeposition, likely resulting episodic intense precipitation. Exclusion reworked analyses reveals that, as megaflora, were absent at time dry tropical briefly appeared. Major climate changes like may commonly destabilize landscapes, increase reworking, thus smooth patterns microfloras, leading underestimates rate magnitude response past global change.