Polar Terrestrial Climate During the Coniacian Age (Middle Late Cretaceous)

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The Tuluvak Tongue of the Prince Creek Formation, North Slope of Alaska, contains the highest-latitude flora of Coniacian (middle Late Cretaceous) age. Preliminary work suggests that the flora probably represents a mixed coniferous forest, and that it contains a diverse assemblage of angiosperms. Leaf-margin analysis of angiosperms can provide quantitative information on mean annual temperature. The temperature estimates can be supported by analysis of the vegetational physiognomy (overall aspect of the vegetation, which is strongly controlled by climate) and of the growth-ring characteristics in fossil wood, particularly if these characteristics can be compared with those of under= and overlying floras. Thus, the flora of the Tuluvak Tongue provides the opportunity to quantify near-polar terrestrial temperatures for the Coniacian Age. Because the Coniacian may have been a thermal maximum in the Late Cretaceous, based on isotopic evidence from marine fossils at lower latitudes, it is particularly important to understand the climate in polar regions for that time. In addition, comparison of the Tuluvak flora with the floras of the Albian-Cenomanian Niakogon Tongue (Chandler Formation) and Campanian-Maastrichtian Kogosukruk Tongue (Prince Creek Formation) will help determine whether climate change near the North Pole was synchronous, within the resolution of the data, with the changes observed at lower latitudes. The information gathered from the Tuluvak Tongue can be used not only to help establish latitudinal temperature gradients for the Coniacian Age, but also will complete the history of near-polar climate change already determined from older and younger floras in the region.