EARLY EOCENE QUILCHENA FOSSIL LOCALITY, BRITISH COLUMBIA: PALEOCLIMATE AND BIOGEOGRAPHY

The Quilchena site in the southern interior of BC is one of several Okanagan Highlands (OH) fossil floras now known to date mostly to the Ypresian (Early Eocene). Quilchena is securely dated radiometrically at 51.5 mya, which places it at the beginning of the Early Eocene warm interval. Both leaf-margin analysis of dicot leaves and bioclimatic reconstructions using a nearest living relative (NLR) approach have determined that the paleoclimate of Quilchena was both the warmest and wettest of the OH sites of similar age. The OH floras are interpreted as having little temperature seasonality. While other fossil floras from this upland region are classified as microthermal (MAT < 13º C), Quilchena is warmer and falls within the mesothermal category (~ 15° C). As chronologies of other localities become better constrained, it is hoped that a time series of climate and vegetational changes will be developed that will assess the impact of the changes surrounding the warmest interval of the Cenozoic. Quilchena is floristically and biogeographically an interesting fossil locality, with a rich flora of gymnosperms (15 genera, including the only confirmed record in OH of the thermophilic Keteleeria), and the only known reproductive structures of Calocedrus and Taxodium. Taxodium and Glyptostrobus, along with an abundance of Metasequoia foliage and Azolla whole plants, suggest that the Quilchena locality was a shallow lake and swamp complex with deposition of coal seams as well as mineral sediments. The only recorded presence of Nyssa (a fruit stone of tupelo or black gum) in the OH further suggests similarities to modern swamp-forests of the southeastern American coastal plain. A large number of angiosperm fossils are also recorded at Quilchena, including thermophiles such as Eucommia (Chinese rubber tree), Dipteronia, and cf. Gordonia (Theaceae). A rich fossil insect fauna is providing a secondary source of paleoclimatic information, with taxa ranging from tropical to temperate affinities.