We review the extensive record of plant fossils before, at, and after the Cretaceous-Paleogene event horizons, recognizing that key differences between plants and other organisms have important implications for understanding the patterns of environmental change associated with the Cretaceous-Paleogene event. Examples are given of the breadth of prior environmental conditions and ecosystem states to place Cretaceous-Paleogene events in context. Floral change data across the Cretaceous-Paleogene are reviewed with new data from North America and New Zealand. Latest Cretaceous global terrestrial ecology was fire prone and likely to have been adapted to fire. Environmental stress was exacerbated by frequent climate variations, and near-polar vegetation tolerated cold dark winters. Numerous floristic studies across Cretaceous-Paleogene event horizons in North America attest to continent-wide ecological trauma, but elsewhere greater floral turnover is sometimes seen well before the Cretaceous-Paleogene boundary rather than at it. Data from the Teapot Dome site (Wyoming) indicate continued photosynthesis, but during or immediately after the Cretaceous-Paleogene event, growth was restricted sufficiently to curtail normal plant reproductive cycles. After the Cretaceous-Paleogene transition in New Zealand, leaf form appears to have been filtered for leaves adapted to extreme cold, but at other high-southern-latitude sites, as in the Arctic, little change in floral composition is observed. Although lacking high-resolution (millimeter level) stratigraphy and Cretaceous-Paleogene event horizons, gradual floral turnover in India, and survival there of normally environmentally sensitive taxa, suggests that Deccan volcanism was unlikely to have caused the short-term trauma so characteristic elsewhere but may have played a role in driving global environmental change and ecosystem sensitivity prior to and after the Cretaceous-Paleogene boundary.

Four different types of paleosols are recognized in the late Eocene–earliest Oligocene Solent Group (Isle of Wight, UK), representing a patchwork of ecosystems. Weakly developed marsh paleosols (Entisol-like; histic Inceptisol-like) are the most common, and there are relatively fewer, slightly elevated Inceptisol-like and Alfisol-like paleosols present as well. The more developed paleosols allow for a quantitative paleoclimatic reconstruction. The Eocene-Oligocene transition is associated globally with the Oi-1 glaciation event. Some nonmarine sequences show long-term cooling and aridification associated with the glaciation. Reconstructed paleoclimatic conditions using Solent Group paleosols do not; instead, they reflect steady mean annual temperatures and gradually increasing mean annual precipitation. This result is consistent with previous evaluations of floral assemblages, which indicate consistent vegetative covering and niche floral elements spanning the Eocene-Oligocene transition. In contrast, there is a significant change in the mammalian faunas found throughout western Europe (Grande Coupure). The evidence for relatively static climatic conditions is not consistent with the scenario of a climatically driven turnover event for the Grande Coupure, although the impact of increased seasonality cannot be ignored.