Geochemical composition and ages of sediment core BELQ300 obtained from Lake Belau, north Germany

Geochemical and palynological data from an annually laminated core sequence (Lake Belau, Schleswig-Holstein) are interpreted with respect to vegetation and settlement history on the basis of a chronostratigraphical model and archaeological evidence. Most settlement periods indicated by pollen and archaeological data can be geochemically identified in the sediment sequence using tracer elements such as K, Rb, Zr and the K/Zr ratio. Whilst air-borne pollen carry a more regional signal, the sedimentary flux of these trace elements is determined by the allogenic input from the catchment area of the lake and, therefore, provides information about the local history of settlement and agricultural land use in the lake's vicinity. This is exemplified for the period of the middle Neolithic Funnel Beaker Culture ('Iversen landnam'), where a time offset of 250 years between both signals has been detected. In contrast, both geochemical and pollen signals are highly synchronous during the Early Migration Period and the High Medieval Period. Additionally, the Fe/Ca and/or U/Fe ratio may serve as a sensitive tracer for human impact on the trophic state of the lake. The suggested impact of the Romans and the High Medieval civilization can clearly be seen (and quantified) from elevated lead input into Lake Belau sediments at this time. Effects of secular climatic changes on the sedimentary chemistry have not been detected and, if present, seem to have been obliterated by anthropogenic activity.基于年代地层模型（chronostratigraphical model）与考古学证据，本研究对石勒苏益格-荷尔斯泰因州贝劳湖（Lake Belau）年纹层岩芯序列（annually laminated core sequence）的地球化学与孢粉学（palynological）数据展开解译，以反演区域植被与聚落历史。多数通过孢粉与考古数据指示的聚落时期，可借助钾（K）、铷（Rb）、锆（Zr）等示踪元素（tracer elements）以及K/Zr比值，在沉积序列中通过地球化学方法予以识别验证。尽管气传孢粉（air-borne pollen）携带的信号更具区域性，但这些微量元素的沉积通量（sedimentary flux）由湖泊流域（catchment area）的外源输入（allogenic input）所控制，因此可用于揭示湖泊周边区域的聚落与农业土地利用本地历史。这一特征在中新石器时代漏斗杯文化（Funnel Beaker Culture，即“Iversen landnam”时期）得到了典型例证，研究发现两类信号在此期间存在250年的时间差。与之形成鲜明对比的是，在民族大迁徙早期（Early Migration Period）与中世纪盛期（High Medieval Period），地球化学与孢粉两类信号呈现高度同步性。此外，铁钙比（Fe/Ca）与铀铁比（U/Fe）可作为敏感示踪剂（tracer），用以反映人类活动（anthropogenic activity）对湖泊营养状态（trophic state）的影响。从该时期贝劳湖沉积物中铅输入量的升高特征中，可清晰观测到并量化古罗马文明与中世纪盛期文明的人类活动影响。本研究未检测到长期气候变化（secular climatic changes）对沉积化学特征的影响；若此类影响确实存在，其信号似乎也已被人类活动的影响所掩盖。