Deglaciation of a large piedmont lobe glacier in comparison with a small mountain glacier - new insight from surface exposure dating. Two studies from SE Germany

Abstract

10Be surface exposure ages of moraine boulders deposited during the maximum Würmian ice extent and the deglaciation period in two different glacial environments show different age distributions despite similar climatic boundary conditions. A consistent and precise late Würmian chronostratigraphy was derived from deposits of a small valley glacier in the Bavarian Forest. Exposure ages from terminal moraines of the Isar-Loisach and the Inn glacier in the Eastern Alps indicate a moraine deposition well before 18.0±1.9 ka and moraine stabilization throughout the late glacial. Both glacial systems reached their maximum Würmian ice extent during the late Würmian. Despite this broad synchronicity, the response time to climatic fluctuations of the valley glacier in comparison to that of the piedmont glacier system is different, with the valley glacier being more sensitive to climatic signals. Synchronicity of the late glacial readvance in the Bavarian Forest and the Eastern Alps was reached during 16-15 ka (Gschnitz advance), when only valley glaciers existed in both regions. The age distributions determined for either of these glacial environments originate likely in glacier ice dynamics and geomorphic processes affecting moraine stabilization acting differently in each setting. Our data gives insight into landscape stability and moraine degradation in different glacial environments and has implications for sampling strategies and data interpretation for glacial exposure ages. Copyright: