浙江沿海15226~5550 cal.aBP的古环境与海平面变化及其对河姆渡文化的影响

SPORO-POLLEN RECORDS OF 15226~5550 cal.aBP ON ZHEJIANG COAST AND IMPLICATIONS FOR SEA-LEVEL CHANGE

通过对浙江沿海南部老鼠山遗址、中部灵山遗址、北部河姆渡遗址3个剖面土样的14 C测年和孢粉分析,揭示了15 226~5 550cal.aBP间孢粉记录反映的古环境及海平面变化,并简要分析二者对河姆渡文化形成发展和衰落的影响。结果表明:(15 226±256)^(5 550±48)cal.aBP大部分期间的沉积处于有海水入侵的环境或温暖的湿地沼泽环境,期间内发生两次海进和两次海退,海平面变化与气候变化基本一致,(15 226±256)^(13 600±130)cal.aBP为海进时期,气候温和略湿;(13 600±130)^(9 778±77)cal.aBP为海退阶段,气候温凉略干;(9 778±77)^(7 372±36)cal.aBP处于全新世大暖期,气候热暖潮湿,发生快速海进;(7 372±36)^(5 550±48)cal.aBP气候略转凉干,海平面下降,为河姆渡文化的形成发展与繁荣时期奠定了重要基础,后期咸潮与洪水内涝使环境恶化,河姆渡文化外迁并走向衰落时期,而浙江沿海古环境演化与海面波动引起的水环境变化是河姆渡文化兴衰的主要原因。

Three cultural ruins at the Mouse Mountain,Lingshan and Hemudu along the south,central and north coast of Zhejiang Province respectively are studied in this paper with the soil samples acquired there.The regional paleoenvironment and sea-level changes during the time of（15 226～5 550）cal.aBP are analyzed on the basis of 14 C dating data and sporo-pollen records.The impact of paleoenvironmental change and sea-level fluctuation on the formation and development of the Hemudu culture is discussed.Our results reveal that during the period of（15 226±256）～（9 778±77）cal.aBP,most of the region is suffered from seawater intrusion and phycophyta was booming.During the period of（9 778±77）cal～（5 550±48）cal.aBP,the region was rather warm and wet,and dominated by wetland marsh.Plants,which favoured a warm and humid environment,dominated with few phycophyta.Two transgressions and two regressions are recognized from the geological records during（15 226±256）～（5 550±48）cal.aBP.The first time of transgression happened in the period from（15 226±256）cal.aBP to（13 600±130）cal.aBP when the climate was mild and semi-humid,and our results suggest that the sea level in that period was higher than the present.Possibly due to the effect of the Younger Dryas Event,the sea level dropped during（13 600±130）～（9 778±77）cal.aBP,and the climate was relatively cold and dry.Climate became warmer again during the period of（9 778±77）cal.aBP to（7 372±36）cal.aBP,which caused the second time of seawater transgression.During（7 372±36）～（5 550±48）cal.aBP,there started the second period of seawater dropping.However,the sea level falling was not big enough to harm the growth of a variety of vegetations.As the result,the Hemudu culture appeared and was prosperously developed until the region was ruined by salt tide and the flooding later on.Changes in the water environment caused by paleoclimate and sea-level fluctuations are the main reason for the rise and fall of the Hemudu culture.