The ELSA-Flood-Stack: A reconstruction from the laminated sediments of Eifel maar structures during the last 60 000 years

Abstract

This study reconstructs the main flood phases in central Europe from event layers in sediment cores from Holocene Eifel maar lakes and Pleistocene dry maar structures. These reconstructions are combined with recent gauge time-series to cover the entire precipitation extremes of the last 60000years. In general, Eifel maar sediments are perfectly suited for the preservation of event layers since the deep water in the maar lakes is seasonal anoxic and therefore, bioturbation is low. However, the preservation of annual lamination is only preserved in Holzmaar and Ulmener Maar; the other cores are dated by 14C, magnetostratigraphy, tephra markers and ice core tuning. The cores were drilled in the Eifel region of central western Germany, which represents a climatic homogenous region from Belgium to Poland and all across Central Europe.A total of 233 flood layers over 7.5mm were detected in all analysed cores. The stratigraphic classification of the flood events follows the newly defined Landscape Evolution Zones (LEZ). The strongest events in the Holocene have occurred during LEZ 1 (0–6000b2k) in the years 658, 2800 and 4100b2k. Flood layers in the LEZ 2 (6000–10500b2k) are not as frequent as during the LEZ 1, nevertheless, the floods cluster between 6000 and 6500b2k. Twenty flood layers are found in the LEZ 3 (10500–14700b2k); 11 in LEZ 4 (14700–21000b2k); 15 in LEZ 5 (21000–28500b2k); 34 in LEZ 6 (28500–36500b2k); 8 in LEZ 7 (36500–49000b2k); zero in LEZ 8 (49000–55000b2k) and LEZ 9 (55000–60000b2k). The maximum flood phases during the Pleistocene are at 11500–17500 (late glacial and Younger Dryas), 23000–24000 (before Greenland Interstadial (GI) 2), 29000–35000 (especially between GI 5 and 4) and 44000–44500b2k (transition from GI 12 to 11).The variations in flood dynamics are climatically driven and mainly associated with climate transitions and colder periods, combined with light vegetation. It turns out that low vegetation coverage related to both Greenland Stadial phases and anthropogenic impacts since late Holocene is the main cause for the development of flood layers in maar sediments. The precipitation itself, plays only a secondary role. This interpretation is based on the current climate understanding of cold phases and several studies of fluvial erosion related to vegetation coverage.