Subei Basin The Xinghua Hole In The Pleistocene Paleo-vegetation And Paleoclimate Records

Studies of long-term climate records are benefit to infer the cycles and rules of climate change, which can provide scientific basis for forecasting the trend of environment evolution in future. In China, most long sequences studies of Quaternary climates are focused on the central loess area and western tableland, in recent years, researches on marine sediments in south -eastern part also make a rapid progress. Compared with them, studies of long-term terrestrial climate records in East Asian monsoon area are very rare. Northern Jiangsu basin lies in the transitional region from ocean to continent and its climate is dominated by the East Asian monsoon system.Reconstructing the evolution history of paleovegetation and paleoclimate in this region will provide significant further understanding of the process, rule and evolution trend of the East Asian monsoon. A drilling core of 350 m at Xinghua in the basin was recovered to reconstruct its environment evolution history. We choose the upper part from 25m to 86.5m for sporopollen analysis.Based on the result of pollen identification and statistics, and combining a numerical technique with the routine method, the pollen assemblages of Xinghua Core was divided into fourteen pollen zones. According to the result of sporopollen analysis, we reconstructed the paleovegetation and paleoclimate of Northern Jiangsu basin during the mid-Pleistocene, and the primary conclusions are as follows:1 Based on the result of former studies ,combing with the paleogeomagnetism datings and the well correlation between pollen assemblages and deep-ocean δ ¹⁸O record ,we deduced that Xinghua Core entered mid-Pleistocene at the depth of 86.5m and ended up it at the depth of 28m.2 Result shows that arbor percentage curve and total concentration curve can be well correlated to the deep-ocean δ ¹⁸O record , seven major cold-warm climatic fluctuation cycles revealed from the pollen record can be well corresponded to the glacial and interglacial cycles from marine sediments, they are MIS19 MIS6 from the bottom up, respectively.3 PaleovegetationThe evolution sequence of paleovegetation in Northern Jiangsu basin during the mid-Pleistocene from the bottom up is: deciduous broad-leaved forest with evergreen broad-leaved trees â†' vegetation sparseness zone â†' forest-forest grassland â†' vegetation sparseness zone â†' evergreen broad-leaved forest with deciduous broad-leaved trees â†' vegetation sparseness zoneâ†'deciduous broad-leaved forest or forest grasslandâ†'vegetation sparseness zone â†' forest-forest grassland â†' vegetation sparseness zone â†' deciduous broad-leaved forest with evergreen broad-leaved trees â†' vegetation sparseness zone â†' deciduous broad-leaved forest with evergreen broad-leaved treesâ†'vegetation sparseness zone.4 PaleoclimateCorresponding to MIS19: Generally speaking, the climate was relatively warm and humid, the annual average temperature was about 1℃ lower than that of today and the annual average precipitation was approximately 900mm. But the climate in later period was a little more drier and warmer than that of the early period.Corresponding to MIS 18: It was cold and dry, but not very severe, there still existedwarm-wet fluctuations.Corresponding to MIS 17: It was relatively warm and dry in early period, but it became more humid in later period. In general, it was the forest-forest grassland climate, the annual average temperature was about 5°C lower than today's and the annual average precipitation was approximately 600⁷00mm.Corresponding to MIS 16: It was cold and dry, belonging to the typical glacial climate.Corresponding to MIS 15: It was very warm and humid. The annual average temperature was 1²Â°C higher than today's and the annual average precipitation was about 1000- 1200mm.Corresponding to MIS 14: It was cold and dry. belonging to the typical glacial climate.Corresponding to MIS 13: In general, the climate was similar to that of MIS 17, but the fluctuation frequency was much lower than that of MIS 17. In early period, climate was warm and humid, but in middle and later period, arbor content decreased, indicating a drop in temperature, the annual average temperature was 5°C lower than today's and the annual average precipitation was approximately 700⁸00mm.Corresponding to MIS 12: It was cold and dry, belonging to the glacial climate.Corresponding to MIS11: It was relatively warm and dry in early period, the annual average temperature was about 5 C lower than today's and the precipitation was about 600⁷00mm. With the emergence of a lot of ferns in later period, the temperature returned to rise and the precipitation also increased relatively.Corresponding to MIS 10: It was cold and dry, belonging to the glacial climate.Corresponding to MIS9: It was warm and humid relatively, the annual average temperature was 1°C lower than today's and the annual average precipitation was about 900mm.Based on the continuous and steady emergence of a large amount of Chenopodiaceae pollen in this stage, we inferred that a transgression may have taken place in Northern Jiangsu basin during this period.Corresponding to MIS8: In general, it was cold and dry, but there still existed warm-wet fluctuations.Corresponding to MIS7: It was relatively warm and humid, the annual average temperature was similar to today's and the annual average precipitation was approximately 900mm. With the increase of arbor percentage and decrease of ferns, the climate in later period was a little more warmer and drier than that of the early period.Corresponding to MIS6: In general, it was cold and dry, but there still existed a warm-wet fluctuation.