Systematic Affinities, Age and Biogeographic Relationships of Fossil Floras from the Eocene Clarno Formation of Oregon

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The Eocene Clarno Formation of Oregon contains a diverse assemblage of fossil fruits, seeds, woods and leaves. Although frequently cited in discussions of Eocene phytogeography, only a small percentage of the Clarno flora has been described. Because it contains several kinds of plant structures preserved in a variety of depositional settings that can be dated radiometrically, the Clarno assemblage is potentially important as a link in correlating Eocene floras across the Northern Hemisphere. A comprehensive treatment of the Clarno flora including reproductive structures and leaves will facilitate intercontinental correlations between the early Tertiary floras of Europe, known mostly from fruit and seed deposits, and those of Asia and North America, best known from leaves. The resulting data set will provide a better understanding of relative intra- and intercontinental floristic uniformity in the Northern Hemisphere during the Eocene and insight into the timing and directions of phytogeographic migrations.