江苏句容宝华山全新世中晚期的花粉与环境

STUDY ON POLLEN ANALYSIS AND PALAEOENVIRONMENTS IN BAOHUASHAN MT. OF JURONG COUNTY, JIANGSU PROVINCE

根据宝华山华山口和官塘头两个剖面的花粉、地层资料 ,结合植物大化石和1 4 C年代资料 ,揭示该地区从 >670 0— 560 0aBP为稳定的温暖湿润时期 ;自 560 0— 51 0 0aBP为全新世中期气候的转型时期 ,冷暖干湿变化较大 ,前期转凉 ,旱涝频繁 ,中期暖湿 ,后期转冷 ;大约从 440 0— 40 0 0aBP又变为稳定的暖湿气候。还根据自然保护区现代植被与花粉的关系和与植物大化石共生的沉积物花粉 ,阐明长江下游新石器时代以来 ,因受人为影响 ,其地区青冈栎与栲的花粉之和占孢粉总数的 1 0 .0 %左右便可能有中亚热带性质的森林存在。本地区的沉积特征表明 :侵蚀和次生黄土堆积反映不稳定气候 ,与海面下降相关 ;淤泥、泥炭堆积阶段为温暖湿润气候 ,受海面升高影响。

On the basis of pollen analysis from two stratigraphical profiles at a valley pass of Baohuashan Mt. and Guantang, integrated with macrofossil data and radiocarbon dating, this study shows a stable climate period with warm and wet conditions between earlier than 6 700 and 5 600 aBP. There was a transitional period of climate fluctuations with cold and/or warm, dry and/or wet conditions between 5 600 and 5 100 aBP. A change in climate with warm and wet conditions registers a stable period from ca 4 400 to 4 000 aBP, and a back to cool condition after 4 000 aBP. Furthermore, according to the relationships between modern vegetation and pollen spectra in the natural protective area of Baohaushan Mt. and between sedimentary pollen and macrofossils, the presence of ca 10% of pollen Cyclobarlanopsis and Castanopsis indicates that a middle subtropical evergreen broad leaved forest did exist in the lower reaches of Yangtze River, where human activities have affected the areas since the Neolithic Age. On the other hand, based on the stratigraphical characteristics, the erosion surfaces and secondary loess deposits indicate unstable conditions, i.e. related to the lowing of sea levels while deposits of mud and peat imply a warm and wet condition and the rising of sea levels which is very typical in the lower reaches of Yangtze River.