长江三峡库区玉溪遗址的环境与人类活动的孢粉记录

对玉溪遗址剖面53个地层样品和附近山地的9个现代表土样品进行了孢粉分析,结果表明:玉溪文化时期(6 000a.BP—7 200a.BP)孢粉组合以乔灌木为主,草本次之,蕨类孢子含量较少。乔灌木中以松属、桦木属、栎属占绝对优势;草本中藜科、蒿属含量较高;蕨类孢子以凤尾蕨为主。孢粉谱反映了较为湿润的气候特征。表土孢粉以超代表性的松属占绝对优势,可能是植被群落演替过程中松属植物作为先锋种类表现在演替初级阶段具有明显生长优势的结果,表土孢粉组合基本与当地植被状况相吻合。本研究在14 C测年基础上结合其它代用指标发现在剖面上部第4—8层和下部淤泥层中Rb/Sr值较高且乔灌木花粉百分含量明显增加,可以解释为该段淤泥层为古洪水遗迹,洪水可能有利于对孢粉的富集。地层剖面中文化层与淤泥层呈现交互沉积,表明周期性的洪水事件影响到了人类活动的连续性。

POLLEN RECORDS OF THE YUXI CULTURE SITE IN THE THREE GORGES RESERVOIR AREA,YANGTZE RIVER

According to the sporopollen analysis of 53 layers samples and 9surface samples at the Yuxi site,Chongqing,SW China,we have discovered that the the pollen assemblages mainly dominanted by trees and shrubs,upland herbs followed,ferns the least in Yuxi cultural period.Most of trees and shrubs are Pinus,Betulaand Quercus,Chenopodiaceae.Artemisiacontents are higher in the herbs;Fern spore is given priority to Pteris.The pollen spectrum reflects a relatively humid climate condition.Surface soil pollen is dominanted by Pinus,which is super representative.As a pioneer plant,Pinus shows obvious growth advantage in community succession.Surface soil pollen assemblages is congruent with local vegetation conditions.Combined with 14 C dating and other climatic proxies,it is recognized that the value of Rb/Sr and the percentage of trees and shrubs are markedly increased in the upper,the 4— 8layers and the bottom sludge layer of the section,which reflects that sludge layer are flood markers and flood can enrich the sporopollen to a certain extent.Interactive Cultural and sludge layers presented in the section at the Yuxi site indicates that periodic flooding events interrupted the continuity of human activity.