Late Quaternary ice sheet extents in northeastern Germany inferred from surface exposure dating

Abstract

We determined in situ cosmogenic 10Be ages for 11 boulders on the Hoher Fläming ice marginal belt and five boulders on the Gerswalder moraine, a recessional moraine of the Pomeranian stage. Previous time estimations for the deposition of these moraines along the southern margin of the Scandinavian Ice Sheet (SIS) in northeastern Germany are mostly based on geomorphology and stratigraphy, and on few radiocarbon dates and recently published surface exposure ages in the case of the Pomeranian moraine. Our new exposure ages range from 21.7±1.2 10Beka to 172.6±6.0 10Beka for the Hoher Fläming ice marginal belt. The wide range of exposure ages may reflect episodic ice marginal belt modification due to intensified erosion by meltwater channeled in the Baruther Urstromtal, (ice marginal valley) accompanied by long-lasting erosional processes like solifluction and aeolian deflation.For the Gerswalder moraine, our new exposure ages range from 12.3±0.6 10Beka to 16.6±1.0 10Beka. Excluding the youngest sample (BER-97-03), we calculated error-weighted mean ages ranging from 15.2±0.5 10Beka to 16.0±0.5 10Beka (n=4), depending on choice of scaling methods, surface erosion and snow cover. These results firmly establish the position of the southern margin of the SIS in northeastern Germany during the Gerswalder substage a recessional phase of the Pomeranian stage.