PALEOCLIMATE AND PALEOBIODIVERSITY DYNAMICS IMMEDIATELY PRIOR TO THE END-CRETACEOUS EXTINCTION (66MA) IN CENTRAL CANADA: EVIDENCE FROM PALEOSOLS, FOSSIL LEAVES AND VERTEBRATE MICROSITES

The fossil-rich deposits of the latest Maastrichtian Frenchman Formation (66Ma) of Saskatchewan, Canada, coeval with the upper Hell Creek and Lance formations in the USA, contain a complete and continuous record of terrestrial vertebrate diversity during the last half-million years leading up to the end-Cretaceous mass extinction. Directly associated with these fossil deposits are a variety of paleoclimatic and paleoenvironmental indicators, preserved on the same fine temporal scales. This study employed a multidisciplinary approach to assessing and linking trends in paleobiodiversity and paleoenvironment/ paleoclimate at a high temporal resolution, with a partial goal to elucidating the relative importance of local factors (e.g. fire, habitat fragmentation) relative to regional and global factors (e.g. volcanism, bolide impact) in shaping pre-extinction biodiversity patterns. Data collected from 31 stratigraphic sections in study area of Grasslands National Park, SK were used to designate seven temporally distinct lithostratigraphic units within the Frenchman Formation. Paleoclimate estimates from these units were derived from x-ray florescence (XRF) analysis of paleosol samples, and from plant macrofossil physiogamy using the Climate Leaf Analysis Multivariate Program (CLAMP). Paleoenvironmental information was additionally gained from sedimentological and lithological examinations. Vertebrate fossil material collected from 38 vertebrate microsites, comprising some 7800 specimens, was used to quantify biodiversity trends across time. This study found that, 1) overall biodiversity was relatively stable prior to the mass extinction, but with two sudden, temporally distinct declines, 2) temporal diversity trends varied among different vertebrate groups (fish, turtles, dinosaurs etc.), 3) faunal turnovers in certain groups suggest changing environmental conditions over time, and 4) local factors (e.g. forest fire) were as important in creating paleobiodiversity patterns as regional or global drivers. These results have important implications for the understanding of the duration and cause of the Cretaceous mass extinction on small spatial scales, and demonstrate the benefits of assessing paleodiversity patterns on multiple ecological levels.