North Jiangsu Basin Xinghua Kong Late Pleistocene Paleo-vegetation And Paleoclimate Records

Northern Jiangsu basin lies in the transitional area from ocean to terrene. The climate of this area is influenced significantly by the East-Asian monsoon. With its successive and thick lacustrine sediments, it has become a fertile ground for paleoclimate and paleoenvironment research. A 350-m core was collected from Xinghua, the central part of northern Jiangsu basin. We choose the upper 25m for the scropollen analysis because it could provide continuous paleoclimate change information since late Pleistocene.With the combination of numerical technique and routine method, the scropollen assemblages was divided into three spore-pollen zones and several subzones.Based on the result of scropollen analysis, we reconstructed the paleovegetation and paleoclimate for this area since late Pleistocene. The primary conclusions are as follows:(1) On the basis of two 14C datings and the result of comparing the percentage curve of arboreal with the SPECMAP curve, we concluded that the depths of 6.4m-5.5m, 12.64m-6.4/5.5m and 25.02m-12.64m correspond to the periods of Holocene, last glacial and last interglacial, respectively.(2) The percentage curve of arboreal is well related to the SPECMAP , and we also can distinguish five stages from it. Stage-l(late glacial period) ;stage-2 (last maximum glacial period);stage-3(interstadial period);stage-4(early stadial of last galcial period) and stage-5(last intergalcial period). The stage-5 can be further divided into five substages: a b c d e.(3) PlaeovegetationThe succession course of paleovegetation in northern Jiangsu basin since the late Pleistocene is: evergreen broad-leaved forest with deciduous broad-leaved trees forest or forest grassland deciduous broad-leaved forest with evergreen broad-leaved trees forest or forest grassland deciduous broad-leaved forest with evergreen broad-leaved trees vegetation sparseness zones evergreen broad-leaved forest with deciduous broad-leaved trees deciduous broad-leaved forest with evergreen broad-leaved trees mixed forest of evergreen and diciduous broad-leaved evergreen broad-leaved forest with deciduous broad-leaved trees.(4) The rule of climate change1) last interglacial periodIt was warm and wet in the early and middle stage and became attenuated in the late stage with some intervening cold events during this period. In this paper, we indentified two colling events at 115-107kaBP and 93.6-85. lkaBP, respectively. And during these colling periods, the temperature is below 8癈, the precipitation is about 600mm.In addition, Temperature corresponding MIS5e is 1癈 higher than today.2) last glacial periodThe scropollen in the last glacial period corresponding to spore-pollen zone2 is relatively scarce. All the arboreal herb and fern almostly disappered, which indicates that the climate of northern Jiangsu basin for this period is veryatrocious,featured by exetremely cold and dry climate. 3) HoloceneThe warmest period of northern Jiangsu basin are about 7.8~6.8ka BP,which lasts lka.And during this period the Holocene optimum of this region reached a maximum, the temperature of this period is 1 C warmer than today. It happened two transgression during the Holocene, the first transgression is at about 8~5 ka BP and the second is at aboutl.7ka BP.Based on the percentage of pollen chenopodiaceae, we infered that the second transgression is on a much larger scale than the first one .