Tropical mangrove pollen from the Middle Miocene Asakawa Formation, northern Ibaraki Prefecture, Northeast Japan

Abstract

The mangrove-swamp-dwelling bivalve Geloina has been found in the Middle Miocene Asakawa Formation in northern Ibaraki Prefecture, Northeast Japan. It was expected that mangrove pollen would also be found in this formation. To investigate this possibility, 37 samples of mudstone were collected from four sites near the known locations of Geloina or Arcid-Potamid fauna. The pollen composition at the four sites is characteristic of the NP-2 zone of the Neogene pollen zones. In particular, fossil mangrove pollen of tropical Sonneratia and subtropical Kandelia were found in the Asakawa Formation.