This monograph presents the fossil diatom remains collected from a forest - tundra deposit discovered in 2001 on Bylot Island (72-74N, 60 - 80W), just north of Baffin Island (Nunavut, Canadian High Arctic). Located more than 2000 km north of the present - day northern treeline, the sediments associated with this fossil forest have been tentatively dated at ca. 2 - 2.5 Ma BP corresponding to the late Pliocene - early Pleistocene period. Several late Tertiary and early Pleistocene fossil beds in North American arctic regions have yielded abundant well - preserved remains of plants and animals, documenting the past existence of coniferous forests at high latitudes. However, the diatom assemblages of these sites have not been ocumented until the present and our knowledge of the late Pliocene - early Pleisocene siliceous algal flora remains scarce. Nine out of a total of 30 analyzed samples contained enough diatom frustules for paleoenvironmental interpretations. These samples originated from three different outcrops within an organic - rich layer assigned to the late Pliocene, representing different stages of wetland (peatland) development within a forested catchment. A total of 218 diatom taxa in 52 genera were recorded and documented on 97 plates with light (LM) and scanning electron microscope (SEM) photomicrographs. The fossil diatom flora was dominated by pennate forms belonging to the genera Cymbella sensu lato, Eunotia, Fragilaria sensu lato, Navicula sensu lato and Pinnularia. Less than 2% belonged to centric diatoms, represented by Ellerbeckia arenaria and taxa of the genus Aulacoseira. This monograph complements information on taxonomy, ecology and distribution of North American diatoms, gathered within the series 'Diatoms of North America'.weiterlesen