Wasatchian (Early Eocene) pollen floras from the Red Hot Truck Stop, Mississippi, USA

Sediments at the Red Hot Truck Stop (RUTS), Mississippi, USA are important because they contain the lowest latitude record of both the earliest known Eocene plant and mammal fossils in North America. The RHTS contains the uppermost Tuscahoma Formation and the lowermost part of the basal Bashi and Hatchetigbee formations. The Tuscahoma Formation is composed of glauconitic sands and silts that represent estuarine to shallow marine sediments. Faunal remains indicate that the RHTS section belongs to the Wasatchian North American land mammal age and specifically to the lower Graybullian subdivision. Pollen and spore floras from the RHTS are moderately diverse (113 taxa) and contain families that today are associated with warm-adapted vegetation types such as Annonaceae, Bombacaceae, Burseraceae and palms. Eocene first occurrences are represented by Brosipollis sp., Celtispollenites sp., Interpollis microsupplingensis, cf. Nuxpollenites psilatus, Platycarya spp., Retistephanocolporites sp. and Symplocos? contracta and by one genus of pteridophyte spore (Granulatisporites sp.). The overall composition and within-sample diversity of the sporomorph flora is more similar to the Hatchetigbee Formation (early Eocene) than to the middle Tuscahoma Formation (late Palaeocene) but among-sample diversity remains unchanged across the Palaeocene/Eocene boundary. The distinct composition of the RUTS demonstrates that floral change across the Palaeocene/Eocene boundary is complex and composed of several phases of floral change.