Natural environmental changes indicated by Late Glacial and Holocene sediments from Lake Constance, Germany

The sediments of Lake Constance are a detailed archive for manifold environmental changes of the lake and its catchment area for the period after the last deglaciation. They are dated by means of sedimentological characteristics, secular variations of the declination of the earthʹs magnetic field, AMS-14C and counting of sediment laminations. In total, the sediments represent a time span of approximately 17,500 cal. yr, i.e. 14,600 14C yr. After meltwater-dominated sedimentation during retreat of the Rhine glacier, wind-transported material settled down between 17,500 and 15,600 cal. yr B.P. (approximately 13,100 14C yr B.P.) and formed beige-brown rhythmites. Overlying dark clays were deposited until the beginning of the Holocene. The lack of wind-transported sediments indicates increasing vegetation around the lake. A subdivision of the dark clay indicated by a change in magnetic volume susceptibility is the result of the Younger Dryas event, which increases the sedimentation rate. Early Holocene sediments contain the highest autochthonous calcite concentrations. Three maximum concentrations occurred around 11,100, 9300 and 7800 cal. yr B.P. (9600, 8300, 6900 14C yr B.P.). Several horizons with dark gray interflow sediments indicate periods with numerous flood events related to the Alpine River Rhine around 4100, 3300 and 2600 cal. yr B.P. (3700, 3100, 2500 14C yr B.P.).