EARLY EOCENE INSECT HERBIVORY AND PALEOCLIMATE OF MID-LATITUDE WHIPSAW CREEK, ALLENBY FORMATION, BRITISH COLUMBIA, CANADA

The early Eocene included several global warming intervals during which North America supported a diverse mix of temperate and tropical plants and insects. Studies outside of Canada established that plant and insect diversity respond to climate change in the geological past–principally temperature–and the early Eocene provides an ideal setting to study this relationship. Previous studies of early Eocene sites from Wyoming-Colorado and Alaska show trends for decreasing diversity and frequency of insect leaf damage types with increasing latitude but lacked data for mid-latitude sites. The Whipsaw Creek site represents one of several early Eocene localities clustered in British Columbia (BC) that provide a mid-latitude site (~50 °N) between WY-CO sites and Alaska. Whipsaw Creek is a cool upland site, with the opportunity to separate temperature from latitude; is lower diversity of insect herbivory on early Eocene age fossil plant leaves in Alaska due to cooler temperatures or due to being at higher latitude? Insect damage data from Whipsaw Creek presents the first such study on a Canadian Eocene flora. This project uses a fossil collection sampled via census technique (i.e. >300 specimens sampled for leaf damage constrained within discrete bedding planes) to reconstruct plant community and insect leaf feeding types during the early Eocene. Preliminary paleoclimate data using leaf physiognomy for 24 leaf morphotypes, with a completion statistic of 0.86, indicate mean annual temperatures of 13-15°C and winters above 0°C for Whipsaw Creek. Our preliminary data shows a low diversity of insect feeding types (margin and hole feeding dominant; surface, skeletonization, and galls uncommon), and low incidence of percent leaf area damaged at 2 levels within this mid-latitude early Eocene site (0.72% & 0.46%). This is lower than WY-CO southern sites, but very comparable to the Alaskan site (0.48%). Follow-up research will expand the study to include early Eocene McAbee, BC.