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Cosmogenic radionuclides (CRNs) are commonly employed to quantify both the production rates and residence times of mobile regolith. Meteoric and in situ CRNs have different accumulation mechanisms and can independently constrain landscape evolution rates. Here we use both in situ and meteoric 10 Be to investigate where in the regolith 10 Be is stored, and to quantify production rates and residence times of mobile regolith on active hillslopes in Gordon Gulch, within the Boulder Creek Critical Zone Observatory (CZO), Colorado, USA. Our data reveal that two-thirds of in situ 10 Be in regolith is produced within saprolite, and at least one-tenth of the meteoric 10 Be inventories is stored in saprolite, highlighting the importance of consistent terminology and identifi cation of the mobile regolith-saprolite boundary. We fi nd that mobile-regolith production rates are on average 3.1 cm/k.y., and residence times are between 10 and 20 k.y. A notable exception exists at the depositional north-facing footslope, where residence times likely exceed 40 k.y. Close agreement between the meteoric and in situ results indicates that upperand mid-slope positions are consistent with steady, uniform lowering of the landscape. In addition to comparing the two methods, we develop a one-dimensional analytical model for the 10 Be concentration fi elds on an active, steady-state catena with uniform erosion. We then compare model predictions with measurements to evaluate how well our sites adhere to the steady-state assumption underlying the calculations for mobile-regolith resi dence time and production rates. Such comparisons suggest that calculated residence times and lowering rates are likely no closer than ±25% of the geomorphic reality.

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This paper presents a detailed sedimentologic data set of minor moraines (heights ≤2.0 m, widths ≤14 m, lengths ≤108 m) that formed beginning near the end of the Little Ice Age by Schwarzensteinkees, a valley glacier in Austria. Sorted sediment and stratified diamict dominate five exposures, and compact massive diamict exists in one exposure. This sediment is interpreted as proglacial outwash and subglacial till. Most moraine sediment shows deformation structures (e.g., smaller and larger folds), and some units contain evidence of water escape. Other units maintain their original subhorizontality. All moraines contain unequivocal evidence of having formed through deformation by pushing during ice-margin fluctuations. Minor moraines formed more specifically by three identified processes: (1) pushing of outwash sediment; (2) stacking and pushing of outwash sediment; and (3) pushing of outwash sediment and freezing-on of subglacial till. Our data suggest that the sedimentologic composition of the valley fill influences the style of push-moraine formation. In this case, the friable nature of outwash sediments can increase the efficiency of the pushing ice front and the likelihood of sediment collapse down the proximal ice-contact slope after ice retreat. This study contributes to our understanding of sediment transport and deposition in high-mountain environments.