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Abstract: We have measured the fast nucleon production of 10Be to depths of 2.37 m (659 g/cm2) in a granodiorite core of uniform density and composition from the Mt. Givens pluton on the western side of the Sierra Nevada, California, at 37° 14.7′ N, 118° 53.7′ W and 2286 m. The data are well fit with a simple exponential decrease yielding an apparent attenuation length of 10Be production of 177 + 4 (2σ) g/cm2. The shallowest data point is from a depth of 1.24 cm (3.45 g/cm2) and shows no indication of a near-surface flattening of the radionuclide inventory and hence the 10Be production rate. [Copyright &y& Elsevier]

We present an integrated petrological, petrophysical, and hydrogeological study of the critical zone (CZ) developed in the Hercynian granitic basement of the Strengbach watershed (Vosges Massif, France) to characterize its deep architecture and water circulation levels. For this purpose, six boreholes (50-120mdepth), from which three are cored, and three piezometers (10-15mdepth) were drilled to define the vertical extension and lateral variability of the main CZ horizons. The Strengbach watershed is composed of a topsoil horizon of limited vertical extension (0.8-1.2 m), a mobile saprolite level, and an in-place fractured bedrock. The latter is subdivided into a few meters thick saprock horizon, defined by open sub-horizontal fractures and a deeper fractured bedrock horizon with steeply dipping fractures (>50°). In the north-facing slope, the vertical extension of the mobile saprolite horizon increases from ≈1-2 m at the top of the slope to ≈9 m downstream, close to the valley bottom. In contrast, the south-facing and more easterly slope shows a mobile saprolite horizon with limited vertical extension (≈2-3 m thick). Such a difference is associated with the existence of a knickpoint in the river bed, separating a downstream zone marked by currently active erosion from an upstream one, less prone to erosion, with preserved reliefs formed around 20 ka ago. The water circulation scheme within the Strengbach watershed involves two different systems: a subsurface circulation within the shallow aquifer, corresponding to the mobile saprolite horizon and the saprock, and a deeper circulation in the fractured bedrock. The water circulation in the fractured bedrock is controlled by fractures of regional orientations, linked to the Vosges massif and the Rhine Graben Tertiary tectonics, and partly to reactivated Hercynian fracture zones. The unaltered bedrock was not reached by any of the three cores. These results from the Strengbach CZ demonstrate the importance of integrating geological history of the watershed, either the long-termgeological bedrock evolution or the Quaternary erosion patterns, to better understand and model the CZ hydrological functioning at the watershed scale. [ABSTRACT FROM AUTHOR]

The 2010 Eyjafjallajökull eruption in Iceland provided a unique opportunity to quantify the evolution of proglacial geomorphology during a series of volcanogenic jökulhlaups (glacial outburst floods) (>140 events). Time-lapse imagery and repeat terrestrial laser scans before and directly after the eruption show that the jökulhlaup of 14 April 2010 composed 61% of the 57 x 106 m³ total discharge of the combined events, and had the highest peak discharge for the two main flood events, but only deposited 18% of the total volume of sediment in front of Gigjökull glacier. The majority of sediments (67% of a total volume of 17.12 x 106 m³) were deposited by the 15 April 2010 jökulhlaup, and this was followed by extensive reworking by a series of smaller jökulhlaups over the following 29 days that deposited 15% of the total sediment. The geomorphological and sedimentary signatures of the two largest jökulhlaups associated with the onset of the eruption have either been reworked by later floods or are buried by later flood deposits. Consequently, the ice-proximal, posteruption landscape cannot be used to reconstruct the characteristics or magnitudes of either of the two largest jökulhlaups. The findings support a complex-response model in which peak discharge and the bulk of the sediment transported is decoupled by changing routing mechanisms and water:sediment ratios during the eruption. [ABSTRACT FROM AUTHOR]