AN 18 MILLION YEAR RECORD OF VEGETATION AND CLIMATE-CHANGE IN NORTHWESTERN CANADA AND ALASKA - TECTONIC AND GLOBAL CLIMATIC CORRELATES

We reconstruct long-term vegetation/paleoclimatic trends. spanning the last 18 million years, in Alaska, Yukon and far western Northwest Ter ritories. Twenty-one average percentage spectra for pollen and spores are assembled from eight surfade/subsurface sections. The sections are dated independently or by correlation. Pollen and spore ratios indica te the direction of change in vegetation and climatic parameters growi ng season temperature (T-est), tree canopy density (C-est) and paludif ication at study sites (P-est). A global warm peak ca. 15 Ma is shown by the abundance of thermophilous taxa, including Fagus and Quercus. A temperature decline immediately following IS Ma parallels climatic re constructions based on marine oxygen isotopes. Subsequent declines cor relate to the Messinian event and the onset of late Pliocene-Pleistoce ne glaciation. After 7 Ma herbs and shrubs become more important eleme nts of the palynological assemblages, suggesting a more continental, c older/drier climate. However, a late Pliocene warm interval is evident . Vegetation/climatic changes during the early to late Miocene show sy nchrony with, and are most economically attributable to. global events . After 7 Ma, vegetation/climate change is attributed primarily to lat est Miocene-to-Pleistocene uplift of the Alaska Range and St. Elias Mt s. The continuing influence of global climatic patterns is shown in th e late Pliocene warm interval, despite uplift to the south. The openin g of the Bering Strait ca. 3 Ma may have moderated the climate in the study area. (C) Elsevier Science B.V.