Abstract:

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return period (years) reflected by the stratum records in the mid Holocene and the exceptional floods recorded by the historical documents in study areas was very close or basically coincident with the change periods of ENSO.It indicated that, the frequency phenomena of exceptional floods might be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.〖