Palynostratigraphy indication of the Pliocene–Pleistocene boundary in Hupo Basin of the East Sea, offshore Korea

A palynological analysis was carried out for the first time on sediments from Hupo Basin, East Sea, offshore Korea, to locate the Pliocene–Pleistocene boundary and thus determine the depositional age of this stratigraphic unit. Core 19ESDP-101, taken from Hupo Basin, yielded diverse, abundant to common pollen and dinocysts. Age-diagnostic palynomorphs were present in certain core intervals (Zone I, depths 120–63.96 mbsf). However, those age indicators were dark brown, heavily broken representatives that appeared together with poorly sorted, opaque, dark phytoclasts in the lower part of Zone II (63.96–38.76 mbsf), and they were considered to have been recycled from reworked late Pliocene strata due to contour currents during the transgression. Biostratigraphically meaningful taxa were the pollen Carya, Liquidambar, and Fagus and the dinocysts Filisphaera filifera subsp. pilosa and Spiniferites pachyderma. The latest stratigraphic occurrence of these pollen taxa in northeast Asia is the Late Pliocene, and that of the dinocysts is the Late Pliocene across a wide range of aquatic areas, especially in the Pacific. The last appearance datum of the age indicators in this study suggested 63.96 mbsf (top boundary of Zone I) as the Pliocene–Pleistocene boundary in core 19ESDP-101.