【摘要】 郑州地区深约4~12m多处发现有1-2层灰黑色黏土层,具有湖沼相沉积特征。中原地区是华夏文明发祥地,文明发展与环境密切相关,稳定的水源是先民生存繁衍的基础,探究古湖存在对认识文明起源与发展具有重要意义。选取该区张五寨、司马村、后真村、安庄村等4个含湖沼层剖面,采集2个标准钻孔和15个控制孔岩心,进行沉积学、物理磁学、生物化石、有机碳和地球化学等环境指标分析。湖沼层系灰—黑色黏土—粉砂黏土,夹于上下河流相沉积中。放射性碳和释光等测年技术测定结果表明,湖沼层时代为全新世中期,约3~8kaBP。黏土含量高值与磁化率低值对应,反映出径流搬运的磁性重矿物较少,表明较弱的水动力条件或静水沉积,代表湖沼相环境。孢粉分析出香蒲属、蓼属、莕菜属、狐尾藻属、眼子菜属等水生植物花粉,最高占草本的19.4%。该湖沼层中有机碳含量平均为21.6%,最高达29.4%。化学元素综合环境C值与黏土含量变化同步,反映出古湖在气候湿润或降水增加的环境下形成;还反映了流域植被覆盖度较高,水土流失少,主要搬运细颗粒物质入湖。沉积证据重建的全新世中期湖沼环境,与区域仰韶和龙山文化的古遗址点分布特征一致,由此定量估计了其分布范围和面积。本研究为郑州地区全新世存在古湖沼提供了科学依据,也为人文考古、遗址发掘提供实践意义的帮助。更多还原

【Abstract】 Black lacustrine peat deposits have been found at several sites of Zhengzhou in a depth of about 4~12m.This paper selected 4outcrops and 17 sediment cores,for analysis of environmental proxies of sedimentology,environmental magnetism,geobiology(pollen and snall shells)and geochemistry.14 C,TL,and OSL dating indicates that the lake occurred 3 ~ 8kaBP,in Mid-Holocene.Lake deposits are composed of gray-black silty clays.The percentage of clay in the layer is higher than that in other layers.High clay content is correlated to low magnetic susceptibility,which means that there was less magnetic heavy minerals coming in,indicating a weak hydrodynamic environment.Pollen of aquatic plants account for 19.4% of the total,including Typha,Polygonum,Nymphoides,Myriophyllumand Potamogeton.TOC content in the lacustrine layers reaches 21.6%on average,and in some of the layers it may be as high as 29.4%.The C-index(function of various chemical elements)is synchronously fluctuated with fine particles.The higher clay content and higher C-index,the more humid climate.This means that it was relatively high in precipitation,with high vegetation coverage,and lower soil erosion during early-mid Holocene than in the periods after ca.3kaBP Some historical documents before 220 BC.mentioned some ancient lakes in the area for examples,the Xingze and the Putianze,eventhough the locations of the paleolakes remain unknown up to date.All the evidence supports the existence of Mid-Holocene paleolakes,whose range and area are quantitatively estimated in the this paper.The results of this study will certainly provide technique support for cultural archeological studies and relic excavation.更多还原