The Albian-Cenomanian flora of the Kukpowruk River, western North Slope, Alaska: stratigraphy, palaeofloristics, and plant communities

Cretaceous plant fossils were collected in the context of sedimentary facie s at 34 localities along the Kukpowruk River, north-western Alaska. The riv er transects three mapped units: the predominantly marine Torok Formation, the transitional Kukpowruk Formation and the predominantly non-marine Corwi n Formation. Fifty-seven taxa, mostly leaves bur including several reproduc tive structures, were recognised and compared to similar aged fossil plants from north-eastern Russia and Alaska. Although divisible into upper and lo wer regional floral suites, most of the flora represents a single stage in floral evolution (we refer to these two plant suites together as the Kukpow ruk flora). There are strong similarities to the very rich (more than 150 s pecies) early-middle Albian flora of the Buor-kemuss floral type in north-e astern Russia. However, because several taxa are quite long-ranging those p lants from the upper delta plain environments of the Corwin Formation are l ikely to be late Albian in age. A second, smaller, component of the flora ( which we here refer to as the Corwin flora) contains angiosperms and is sim ilar both to the Grebenka floral type of north-eastern Russia and the Upper Killik and Niakogon floras from the central and eastern North Slope of Ala ska. From consistent associations between specific taxa and sedimentary fac ies distinct plant communities have been recognised: a marginal marine and early successional marsh/heath community dominated by Equisetites and Biris ia ferns, shrubby to forested river margin communities dominated by Ginkgo, and mire forest communities dominated by Pityophyllum and Podozamites. (C) 2001 Academic Press.