POSTGLACIAL CLIMATIC AND ENVIRONMENTAL EVOLUTION IN CENTRAL EUROPE INFERRED FROM ANALYSIS OF LAKE STEISSLINGEN SEDIMENT CORE, SW-GERMANY

 

 

Understanding of past environmental changes including climatic evolution is crucial for prediction of future climate development following the argument “the past is the key to the future”. We investigated a 6.5 m well-dated (¹⁴C-AMS, tephra layers, varve-counting) core from Lake Steisslingen, SW-Germany, covering the past 15.600 years BP, for environmental and climate change using palynology and a variety of organic and isotope geochemical proxies at high (in key intervals decadal) resolution.

Excellent preservation of organic matter is due to intensive stratification of the water body, with periodic occurrence of photic zone anoxia indicated by isorenieratane pigments derived from chlorobiaceae. Whereas n-alkane distributions exclusively indicate land plant wax input, carboxylic acid compositions calculated as terrestric/aquatic-ratio (TAR_fa) reveal a constant aquatic background input (TAR_fa=0.5 to 0.8) interrupted by phases of predominantly terrigenic input (TAR_fa=1.0 to 2.8). Periods of elevated land plant input seem to coincide with Postglacial short-lived cold periods, so-called Bond-events, known from marine and ice-records. Several time-equivalent discharge events were reported from NW-German maar lakes.

Pollen and n-alkane distributions reveal a very short warming phase within the Younger Dryas (YD) cold period, the so-called Mid-YD-event. Furthermore, separation of an earlier, colder and drier from a later, warmer and more humid YD interval is achieved via d¹³Corg signatures, whereas carbonate d¹⁸O-values remain constant. Carbon isotopes of organic matter reflect the change from tundra to forest type vegetation with a shift to more depleted values. Fractionated input of leaf wax derived land plant material is evident from very light d¹³Corg (-29 to -38 ‰) and also from exceptionally light d¹⁵N-values (+2 to -6 ‰). Contrastingly, phases of intensive soil erosion, e.g. due to Roman settlement, yield heavy d¹³Corg (-24 to -26 ‰) and d¹⁵N-values (+4 to +8 ‰). A differentiation between natural climate variability and anthropogenic influence is achieved by using a multi-proxy approach.

The unique depositional regime of Lake Steisslingen enabled combined application of palynological, molecular and isotopic geochemical proxies, providing detailed information on fossil environments.