Floral and paleoenvironmental history from the late Pliocene to middle Pleistocene in and around central Japan

Abstract

Floral and paleoclimatic change from the late Pliocene to middle Pleistocene in and around central Japan is described based on the plant macrofossil records. From the later stage of the Pliocene to middle Pleistocene, Tertiary elements became extinct and modern elements including middle-temperate to subarctic elements emerged instead. The floral change succeeded stepwise. Before 3 m.y. B.P., Tertiary elements flourished under the warmest climate through the late Pliocene and Pleistocene. The first climatic deterioration began at about 3 m.y. B.P. By 2.5 m.y. B.P., 17 extinct members were eliminated and middle- and cool-temperate elements appeared instead. Around the Plio-Pleistocene boundary, 1.6 m.y. B.P., the first severe cold stage was indicated by the first occurrence of subarctic elements. After 1.1 m.y. B.P., climatic fluctuation occurred at less than 100,000 year intervals. A severe cold stage is recognized at a horizon above the Jaramillo event, about 0.8 m.y. B.P. Some plant species, including Metasequoia glyptostroboides, became extinct during the later stage of the early Pleistocene. The remnants of Tertiary elements became extinct during the later stage of the middle Pleistocene, later than about 0.5 m.y. B.P. Plio-Pleistocene plant extinction in and around central Japan is attributed to climatic deteriotation in combination with the geomorphological changes caused by uplift of the mountains around the sedimentary basin.