First 36Cl exposure ages from a moraine in the Northern Calcareous Alps


A well-preserved moraine system in the Mieminger Range (Northern Calcareous Alps of Austria) provides geomorphological evidence of a former glacier advance reaching significantly beyond the extent of subsequent glaciation during the “Little Ice Age”. The reconstructed palaeoglacier is associated with an equilibrium line altitude lowering of -70 – -120 m and boulders on its moraine were 36Cl dated to the early Holocene (~10.4 ka). Hence, the glacier advance was likely triggered during a phase of glacier-friendly climate within the Preboreal period. On the proximal side of the moraine, further boulders were dated on hummocky moraines within the former glacier tongue area showing considerably younger ages of around 9 ka. In connection with several relict rock glaciers in the cirque that formed subsequently to the glacier advance, these ages point to a prolonged phase of instable conditions, possibly as a consequence of the formation of discontinuous permafrost and periglacial activity within the cirque. All these landforms lie significantly up valley from a series of lateral moraine segments related to the “Egesen” stadial (Younger Dryas cold phase). The 36Cl ages presented here are the first exposure ages gained from moraines in the northern Alps and form a first step for a numerically dated moraine chronology in the northern Alps.
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