Discovery of fossil remains of Tertiary high-latitude forest vegetation during 19th century polar exploration was recognized as critical to an understanding of long-term global climatic evolution and origins of modern mid-latitude northern temperate vegetation. An extensive record of early Tertiary plants is preserved within rocks of the Eureka Sound Group exposed in the Canadian Arctic Archipelago, and intensive collecting from this Group over the past 15 years has provided a basis for paleofloristic and paleoenvironmental interpretations. Fossil locality data and preliminary floral lists are included for all principal collection sites on Ellesmere and Axel Heiberg islands from the four constituent units of the Group, the Expedition, Strand Bay, Iceberg Bay, and Buchanan Lake formations, ranging in age from early Paleocene through middle Eocene and representing paleolatitudes of 75-80 degrees N. Flora and vegetation are consistent with a mesothermal, humid climatic regime with little or nonexistent frost at low elevations throughout the polar regions. Although the four formations are floristically distinct, Paleocene through early Eocene assemblages are vegetationally similar. Assemblages from the youngest formation, the middle to late Eocene Buchanan Lake, are more complex and are correlated with both structural reorganization of the ancient Sverdrup Basin during the Eurekan Orogeny and the onset of Tertiary global climatic deterioration. The origins of some of the lineages that characterize northern deciduous vegetation may have been influenced by tectonically induced regional environmental complexity and global cooling.
