Middle-and late-Holocene environments and vegetation history of Kunashir Island, Kurile Islands, northwestern Pacific

Abstract

Natural middle-and late-Holocene environmental development of Kunashiri Island reflects global climatic changes and the migration of warm and cold currents. Dry and cool climate changed to warm and moist about 7000–6500 BP, later than on Hokkaido Island. At this time Kuroshio Current system became more active. On Kunashir Island birch assemblages were replaced by cool-temperate broadleaf forests in the south and mixed coniferous/broadleaf forests in the north. The highest sea-level position reached 2.5–3 m above PSL about 6500–6300 BP. Cooling about 4700–4500 BP island vegetation weakly changed that connected with warm current influence. Major regression at this period led to formation of extensive coastal dunefields. The warming at the beginning of the late Holocene was almost similar to the Holocene Optimum. Two minor transgressions are recorded about 4010–3400 and 2950–2620 BP. Active entrance of detrital material to the coastal zone resulted in growth of accumulative landforms. Vegetation changes and climatic deterioration took place in the second half of the late Holocene. Coniferous and mixed coniferous/broadleaf forests shifted southward and occupied a large part of the island. During cooling at 1700–1300 BP the isthmus area increased, coastal wetlands with lakes and coastal dunes were formed, and grassland and swamp landscapes developed. Late-Holocene warming was not intensive. Active aeolian accumulation took place during the ‘Little Ice Age’ cooling and regression.