Glacial dynamics at the beginning of Termination I in the Eastern Alps and their stratigraphic implications

Results of a geological re-investigation of the type localities of the Bühl stadial, the supposed first halt during ice decay of the Inn glacier in the basin of Hopfgarten and at the southern flank of the mountain range Wilder Kaiser (Northern Tyrol, Austria) are presented. It is shown that in this region no stationary or advancing Inn glacier tongue existed following the Last Glacial Maximum (LGM) ice extent. All sedimentary and morphological evidence indicates that large parts of the Inn glacier and all other Eastern Alpine valley glaciers became stagnant followed by massive down wasting. Hence, this period after the LGM, at the beginning of Termination I (∼Würm-Lateglacial), is best defined as “phase of early Lateglacial ice decay”, which can be tentatively correlated to Greenland Stadial 2c (21.2–19.5 kyr BP). Only smaller glaciers advanced towards their Lateglacial Maximum Position (LMP). This happened mostly due to short-lasting climatic oscillations as indicated in the Windau valley (Hopfgarten) and at Steinach am Brenner. A mechanically induced glacier advance is reconstructed for the cirque glaciers of the Wilder Kaiser. At an advanced stage of down melting they lost their blockade established by the Inn glacier during LGM and advanced downvalley. It is proposed to define the processes of this phase by lithostratigraphic type-sections.