Abstract
The Bohemian Forest (Šumava Mts.) lakes are situated along the Czech-German-Austrian border. In addition to the existing eight glacial lakes, other eight infilled lakes were found so far. These sites represent important natural archives, allowing reconstructions of past environmental changes since the end of the last deglaciation. Although these sediments became a subject of increasing scientific interest during the last decades, a comparison among the individual lakes is still lacking. Here, we aim to investigate the age of these natural archives and compare their general lithostratigraphic patterns. To fulfil our research aim, we studied lake sediment cores from three localities (Plešné jezero, Prášilské jezero, Stará jímka) and compared them with the published data on other two sites (Malé Černé jezero, Rachelsee), using accelerator mass spectrometry (AMS) radiocarbon dating, simplified description of the lithology, and loss-on-ignition (LOI). Sediments of Late Glacial age contain a series of silt- and clay-dominated layers with low proportion of organic matter indicated by LOI with concentrations usually <10%. In contrast, the Holocene sediment consists of organically-rich dark brown material (gyttja). In the infilled lakes, this sediment gradually becomes peaty in the upper layers (LOI 16-96%). The oldest 14C date based on AMS dating of terrestrial plant remains (14411-13831 cal. yr. BP; Stará jímka) corresponds to the Bolling interstadial. Despite repeated sampling, no evidence of Late Glacial sediments was documented in Prášilské jezero. Based on the first results obtained from the sediment cores, we conclude that:
1) The age of sedimentation onset in the Bohemian Forest lakes may differ from age of the moraines damming the lake water.
2) The oldest natural archives represented by the Bohemian Forest lake sediments cover at least the whole Late Glacial period (ca. 14700-11650 cal. yr. BP).
3) Besides individualities in historical development of each catchment, the lake sediments reflect the general regional changes due to climatically driven deglaciation and forest establishment.
4) The future investigation of the Bohemian Forest lake sediments needs to be based on a uniform and coherent approach including geochemical, geophysical, and palaeoecological methods. In addition, the dating can be supported by tephrochronology as the Laacher See Tephra was recently documented at Stará jímka site.