Late Pleistocene Spread Of (cool-)temperate Forests In Northeast China And Climate Changes Synchronous With The North Atlantic Region

摘要

The results presented here from the annually laminated sedimentary sequence of Sihailongwan lake provide the first comprehensive palaeoecological record covering the Late Pleniglacial to the Early Holocene (16,700-10,600 cal yrs. BP) from Northeast China. High-resolution pollen analyses have enabled the vegetational and climatic changes of the last glacial-interglacial transition to be reconstructed in more detail than has been previously possible. Moreover, a reliable chronology has been provided by both varve counting and 40 calibrated AMS ~(14)C age determinations. Palaeobotanical evidence indicates predominantly steppe and open taiga-like woodland communities, with abundant Betula, Larix, Alnus fruticosa, Artemisia, grasses and sedges, which are typical of cold and dry conditions between 16,700 and 14,450 cal yrs. BP. The beginning expansion of Ulmus and Fraxinus marks the onset of the Late-glacial climatic amelioration at 14,450 cal yrs. BP. Dense deciduous forests, predominantly consisting of thermophilous broadleaf taxa, become established and widespread during the Early Holocene. Two short-term climatic reversals to colder and/or dryer conditions are recorded in the proxy data between 13,900 and 13,800 cal yrs. BP and 13,100 and 12,900 cal yrs. BP, correlating with the Oldest Dryas/Greenland Interstadial (GI) 1d event and the Gerzensee/Killarney/GI-1b oscillation, respectively. The prominent reappearance of Picea and Larix, coupled with a marked decrease in broadleaved trees, prior to the start of the Holocene, implies a climatic reversal compatible with the Younger Dryas event in the circum-Atlantic region. The evident synchroneity of climate changes in the North Atlantic region and East Asia supports the theory of strong atmospheric coupling between both regions.