GREENHOUSE PALEOBIOGEOGRAPHY IN WESTERN NORTH AMERICA: CONSTRAINING THE INFLUENCE OF CLIMATE AND GEOGRAPHY ON PLANT PROVINCIALITY THROUGH TIME

Spatial climate patterns are primary controls on the geographic distribution of plant and animal taxa and communities. Shifts in climate and environmental zones can pose significant challenges for species adapted to specific conditions, often resulting in biodiversity loss and local extinctions. Understanding how spatial climate variations affected ecosystems in the past is essential for addressing the pressing challenges of modern climate change. During the Late Cretaceous period (100 to 66 Mya), the spatial distribution of key floral and faunal groups in western North America has been interpreted as evidence of pronounced north-south biological provinciality. Previous studies have suggested that these distinct northern and southern communities were produced by a “climate barrier.” Consistent with this hypothesis, a recent geostatistical analysis of Late Cretaceous paleobotanical and paleotemperature data from western North America provided strong evidence of a temperature “transition zone” separating a southern warm province and a northern cool province. These climate zones were associated with distinct paleobotanical provinces, and the authors suggested that the spatial temperature pattern and associated botanical biogeography were produced by circulation patterns in the nearby Western Interior Seaway. However, to better constrain the impact of the seaway on nearby paleoclimate conditions and paleobotanical distributions, additional data are needed from before the seaway’s formation (~125 Ma) and after its final retreat (~50 Mya). The objective of this study is to create an expanded Cretaceous paleobotanical database for comparison to paleotemperature and paleoprecipitation maps of Cretaceous North America, with the goal of constraining paleobotanical provinciality during the growth and retreat of the Western Interior Seaway.