Paleofloristic and paleoenvironmental implications of a Late Jurassic palynoflora from the Tochikubo Formation, North-East Japan

Abstract

The first Jurassic palynofloral assemblage from Japan is reported from the Oxfordian Tochikubo Formation of the Soma-Nakamura Group, Fukushima Prefecture. Palynomorphs are quite diversified, with 32 genera and 41 species of lycopod and fern spores, gymnosperm pollen and freshwater algae. The composition of the assemblage is consistent with the Oxfordian age of this nonmarine formation and confirms a fluvio-lacustrine paleoenvironment, further detailing the paleovegetation reconstructed from macrofloral remains. Previous palynofloral reports of eastern Asia are reviewed and indicate that northeast Japan shares most similarities with coeval paleofloras of southeastern Russia. Consequences for paleofloristic provincialism and climates of the region during the Late Jurassic are discussed.