Latest Cretaceous (Maastrichtian) climate of the Koryak Upland of North-East Russia based on a quantitative analysis of a palaeo-polar flora

Abstract

We describe fossil plant assemblages from the late Maastrichtian Kakanaut Formation of the Koryak Upland, North-East of Russia, which represent a high (75oN) palaeolatitude flora. The flora contains about 40 species, including liverworts, horsetails, ferns, cycadophytes, ginkgos, conifers and angiosperms. Angiosperms and conifers predominate and, unusually, the flora contains typical Cretaceous taxa admixed with elements that are more characteristic of the Paleocene. Reconstruction of the palaeoclimate in the Kakanaut area was made using the Climate Leaf Analysis Multivariate Program (CLAMP) employing a recently developed calibration that yields 23 different climate variables. Analysis was made based on 21 morphotypes of woody dicotyledonous plants from the Kakanaut flora. The analysis indicated a mean annual temperature of 12.2 ± 2.0 °C, a warmest month mean temperature of 20.6 ± 2.5 °C, a coldest month mean temperature of 4.8 ± 3.2 °C. The growing season lasted approximately 7 months, during which there was almost 1 m of precipitation. This and other indicators (relative humidity, vapour pressure deficit and potential evapotranspiration) all suggest a year-round humid regime. The winter temperatures suggest occasional mild frosts in this near sea level setting, so that at higher elevations freezing conditions would have been more persistent. These results throw new light on the living and breeding conditions of diverse latest Cretaceous Arctic dinosaur populations as represented by numerous skeletal and egg remains associated with the plants.