Ранний - средний голоцен северного Сахалина

Abstract

New palynological and radiocarbon data obtained from sections of two ancient peatbogs permitted to specify the landscape and climatic changes in the nature of the first half of the Holocene on the southern outskirts of North Sakhalin. The Early Holocene was generally colder and drier in comparison with modern climatic conditions. The vegetation cover was dominated by larch/birch forests with the shrub birch undergrowth. In the middle of the Boreal Period (9000-8400 yrs. BP / 10,100-9300 Cal. yrs. BP), the climate became significantly warmer and slightly wetter, yet remaining drier than the modern one. Birch forests with the presence of broad-leaved and dark coniferous tree species were widespread. In the initial phase of the Atlantic Period (probably 7800-7500 yrs. BP / 8800-8300 Cal. yrs. BP), in the climatic conditions warmer and much more humid than modern ones, the first expansion of spruce/fir forests occurred. The second half of the early and first half of the middle phase of the Atlantic Period (7500-6500 yrs. BP / 8300-7400 Cal. yrs. BP) were distinguished by decreased humidity and further warming of the climate, which resulted in dominating birch forests, subordinate spruce/fir taiga, and a lot of deciduous forests. There were two cold episodes at the beginning and in the middle of this stage. The first of them, about 7300 yrs. BP / 8100 Cal. yrs. BP, was dry and provided the return of birch/larch forests. The second, about 7100 yrs. BP / 7900 Cal. yrs. BP, had a more humid climate, which caused an increase in the role of dark coniferous taiga and a weakening of birch forests. In the second half of the middle and, possibly, the beginning of the late phase of the period (probably 6500-5400 yrs. BP / 7400-6200 Cal. yrs. BP), spruce/fir forests with participation of broad-leaved tree spread. They developed in a warmer and more humid climate, similar to the current climate in the south of the Sakhalin Island and close to the optimal climatic conditions of the post-glacial time. The middle of the Late Atlantic Period, about 5300 yrs. BP / 6100 Cal. yrs. BP, was marked by the second, maximum expansion of spruce/ fir forests, due to the onset of the cool and, possibly, the wettest episode in the Middle Holocene.