Varve microfacies and varve preservation record of climate change and human impact for the last 6000 years at Lake Tiefer See (NE Germany)
Varve microfacies and varve preservation record of climate change and human impact for the last 6000 years at Lake Tiefer See (NE Germany)
复制标题
DOI：
10.1177/0959683616660173
复制
发表时间：
2017-03-01
期刊：
影响因子：
2.4
通讯作者：
Brauer, Achim
中科院分区：
文献类型：
--
作者：
Draeger, Nadine;Theuerkauf, Martin;Brauer, Achim
铁费尔湖全新世沉积物记录显示出良好的变化和不变化的间隔之间的显著变化。在这里，我们提供了过去类似于6000年的高分辨率多代理记录，并讨论了观测到的沉积物变化的可能原因。这种方法包括微相、地球化学和微化石分析，以及包括伏特计数、年代学和放射性碳测年在内的多重测年概念。确定了6000-3950、3100-2850和2100-750cal四个沉积时期。英国石油公司和公元1924年-现在。除近新近形成的火山口外，这些时期被认为反映了湖泊环流减少，从而反映了更强的缺氧底水条件。相反，河流保存不佳的夹层甚至广泛混合的非变异沉积物表明湖泊环流增强。自1924年以来的次新近火山口形成，除了自然强迫外，还受到现代人为富营养化导致的湖泊生产力提高的影响。铁夫尔湖环流加强的周期普遍增加，与4000卡相似。BP可能是由北半球轨道强迫的逐渐变化引起的，导致中欧地区更凉爽和更多风的条件。湖泊环流状况的十年至百年尺度的叠加变化很可能是额外的人类引起的集水区植被变化的结果。铁费尔湖的主要非变异周期与波罗的海生物扰动沉积物的间隔相吻合，暗示了我们的发现具有更广泛的区域意义。
The Holocene sediment record of Lake Tiefer See exhibits striking alternations between well-varved and non-varved intervals. Here, we present a high-resolution multi-proxy record for the past similar to 6000years and discuss possible causes for the observed sediment variability. This approach comprises microfacies, geochemical and microfossil analyses and a multiple dating concept including varve counting, tephrochronology and radiocarbon dating. Four periods of predominantly well-varved sediment were identified at 6000-3950, 3100-2850 and 2100-750cal. a BP and AD 1924-present. Except of sub-recent varve formation, these periods are considered to reflect reduced lake circulation and consequently, stronger anoxic bottom water conditions. In contrast, intercalated intervals of poor varve preservation or even extensively mixed non-varved sediments indicate strengthened lake circulation. Sub-recent varve formation since AD 1924 is, in addition to natural forcing, influenced by enhanced lake productivity due to modern anthropogenic eutrophication. The general increase in periods of intensified lake circulation in Lake Tiefer See since similar to 4000 cal. a BP presumably is caused by gradual changes in the northern hemisphere orbital forcing, leading to cooler and windier conditions in Central Europe. Superimposed decadal- to centennial-scale variability of the lake circulation regime is likely the result of additional human-induced changes of the catchment vegetation. The coincidence of major non-varved periods at Lake Tiefer See and intervals of bioturbated sediments in the Baltic Sea implies a broader regional significance of our findings.