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Abstract. In the last decades surface exposure dating using cosmogenic nuclides has emerged as a powerful tool in Quaternary geochronology and landscape evolution studies. Cosmogenic nuclides are produced in rocks and sediment due to reactions induced by cosmic rays. Landforms ranging in age from a few hundred years to tens of millions of years can be dated (depending on rock or landform weathering rates) by measuring nuclide concentrations. In this paper the history and theory of surface exposure dating are reviewed followed by an extensive outline of the fields of application of the method. Sampling strategies as well as information on individual nuclides are discussed in detail. The power of cosmogenic nuclide methods lies in the number of nuclides available (the radionuclides 10Be, 14C, 26Al, and 36Cl and the stable noble gases 3He and 21Ne), which allows almost every mineral and hence almost every lithology to be analyzed. As a result focus can shift to the geomorphic questions. It is important that obtained exposure ages are carefully scrutinized in the framework of detailed field studies, including local terrace or moraine stratigraphy and regional morphostratigraphic relationships; as well as in light of independent age constraints.

Catchment-wide denudation rates (CWDRs) obtained from cosmogenic nuclides are an effi cient way to determine geomorphic processes quantitatively in alpine mountain ranges over Holocene time scales. These rate estimations assume steady geomorphic processes. Here we use a time series (3 yr) in the Aare catchment (central Swiss Alps) to test the impact of spatially heterogeneous stochastic sediment supply on CWDRs. Our results show that low-frequency, high-magnitude debris-fl ow events signifi cantly perturb cosmogenic nuclide ( 10 Be, 14 C) concentrations and thus CWDRs. The 10 Be concentrations decrease by a factor of two following debris-fl ow events, resulting in a doubling of inferred CWDRs. The variability indicates a clear time and source dependency on sediment supply, with restricted area-weighted mixing of sediment. Accordingly, in transient environments, it is critical to have an understanding of the history of geomorphic processes to derive meaningful CWDRs. We hypothesize that the size of debris fl ows, their connectivity with the trunk stream, and the ability of the system to suffi ciently mix sediment from low-and highorder catchments control the magnitude of CWDR perturbations. We also determined in situ 14 C in a few samples. In conjunction with 10 Be, these data suggest partial storage for colluvium of a few thousand years within the catchment prior to debris-fl ow initiation.

We combine 10Be surface exposure ages from boulders and bedrock, field observations and measurement of bedrock ice‐flow direction indicators with numerical ice surface models to develop a model of the evolution of the Oberhasli area in the central Swiss Alps from the Last Glacial Maximum (LGM) to the early Holocene. Surface exposure ages from bedrock and boulder samples imply that the highest ice surface at the glacial trimline in Haslital was attained at 23.0 ± 0.8 ka. Significant retreat followed no later than 17.7 ± 0.8 ka. Several boulders were let down on the Gelmerhörner ridge during lowering of the ice surface of the Aare LGM glacier. Their exposure ages of 16–14 ka suggest that patches of remnant ice persisted on the trough shoulder until the Bølling–Allerød interstadial. Lateglacial glacier systems in the High Alps were of a dendritic character, confined to the trunk valleys and cirques. Based on combined evidence from glacial erosional marks, surface exposure ages and numerical modelling we have been able to constrain the likely terminal position and ice surface of the Egesen stadial glacier (Younger Dryas equivalent) in Haslital. Exposure ages from the trough floor imply that deglaciation was completed at the end of the Younger Dryas at 12.2–10.8 ka.

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