中文摘要：

为提高史前洪水研究的可信度,结合研究区现代洪水沉积特征的野外调查以及考古遗址高程与历史异常高水位的相关分析等,运用历史洪水资料考证的方法,对长江上游玉溪剖面约6 567～6 489aBP沉积的超过1.5m厚淤砂层进行了综合分析,探讨了该古洪水沉积现象的真实可靠性、发生规模、特征以及可能的驱动或影响因素。结果表明：长江上游玉溪约6 567～6 489aBP形成的古洪水层反映了长江上游中全新世在约78a的短暂时间里至少出现过5次以上的异常大洪水,所留下1.5m厚的洪水沉积物是可能的。研究区中全新世地层记录、历史文献记载所反映异常洪水的重现年数,与ENSO变化周期非常接近或基本吻合的特征,表明长江上游自中全新世以来其异常大洪水的频发现象,可能与ENSO变化周期有关。

英文摘要：

To improve the credibility of prehistory flood research,combining the field survey of sedimentary characteristics of modern flood as well as the correlation analysis between the archaeological sites and unordinary flood stage in history in the study area etc.,using the textual researches of the flood document in the history,this paper analyzed comprehensively the more than 1.5 m silt-sand layers which were deposited about during 6 567~6 489 aBP in Yuxi profile in the upper reaches of the Yangtze River,and discussed the authenticity,reliability,magnitude,characteristics and possible driving or influence factors of the paleoflood sedimentary phenomenon.The paleoflood layers formed about during 6 567~6 489 aBP in Yuxi profile reflected that there were more than 5 exceptional floods at least,which occurred about during the 78 a in the upper reaches of the Yangtze River in the mid Holocene,and it was possible that the more than 1.5 m flood deposits were remained.The characteristics which the return period（years） reflected by the stratum records in the mid Holocene and the exceptional floods recorded by the historical documents in study areas was very close or basically coincident with the change periods of ENSO.It indicated that,the frequency phenomena of exceptional floods might be linked to the change periods of ENSO in the upper reaches of the Yangtze River since the mid Holocene.