Early Paleogene Boguchan flora of the Amur Region (Russian Far East): Composition, age and palaeoclimatic implications

The Boguchan floristic assemblage from the Middle Tsagayan subformation of the Zeya-Bureya Basin (Russian Far East) is Paleocene in age according to both palaeobotanical (palynological and plant megafossil) studies and isotope dating of the plant-bearing deposits. It comes from two localities situated in the vicinity of Arkhara Village. The Boguchan assemblage includes 48 fossil plant species belonging to horsetails, ferns, gymnosperms and angiosperms, with angiosperms and taxodiaceous conifers being the most diverse and numerous. For the first time all plant fossils of the Boguchan assemblage are illustrated, the plant-bearing deposits and their correlation between the localities are discussed and two new angiosperm species, Craspedodromophyllum boguchanicum and Archeampelos betulifolia, are described. Variables of palaeoclimate experienced by the Boguchan plants are estimated using CLAMP technique. The Boguchan flora grew in humid temperate conditions with hot summers, mild winters and without dry period during the year (climate Cfa according to the Köppen's classification of global climates).