Showing papers by "Peter W. Kubik published in 2010"

10Be and 26Al measurements at the Zurich 6 MV Tandem AMS facility

Abstract: The setups for the 10 Be and 26 Al AMS measurements at the Zurich 6 MV EN Tandem AMS facility are presented and data analysis procedures for both radionuclides are discussed. Performance parameters of the system are shown. In-house AMS standards are compared to commercially available AMS standards.

Cosmogenic nuclide‐derived rates of diffusive and episodic erosion in the glacially sculpted upper Rhone Valley, Swiss Alps

Abstract: Denudation rates of small tributary valleys in the upper Rhone valley of the Swiss Central Alps vary by more than an order of magnitude within a very small distance (tens of kilometers). Morphometric data indicate two distinct erosion processes operate in these steep mountain valleys. We determined the rates of these processes using cosmogenic beryllium-10 (10Be) in pooled soil and stream sediment samples. Denudation in deep, glacially scoured valleys is characterized by rapid, non-uniform processes, such as debris flows and rock falls. In these steep valleys denudation rates are 760–2100 mm kyr−1. In those basins which show minimal previous glacial modification denudation rates are low with 60–560 mm kyr−1. The denudation rate in each basin represents a binary mixture between the rapid, non-uniform processes, and soil creep. The soil production rate measured with cosmogenic 10Be in soil samples averages at 60 mm kyr−1. Mixing calculations suggest that the debris flows and rock falls are occurring at rates up to 3000–7000 mm kyr−1. These very high rates occur in the absence of baselevel lowering, since the tributaries drain into the Rhone trunk stream up-stream of a knickzone. The flux-weighted spatial average of denudation rates for the upper Rhone valley is 1400 mm kyr−1, which is similar to rock uplift rates determined in this area from leveling. The pace and location of erosion processes are determined by the oscillation between a glacial and a non-glacial state, preventing the landscape from reaching equilibrium. Copyright © 2010 John Wiley & Sons, Ltd.

A multi-dating approach applied to proglacial sediments attributed to the Most Extensive Glaciation of the Swiss Alps

Abstract: The number and the timing of Quaternary glaciations of the Alps are poorly constrained and, in particular, the age of the Most Extensive Glaciation (MEG) in Switzerland remains controversial. This ice advance has previously been tentatively correlated with the Riss Glaciation of the classical alpine stratigraphy and with Marine Isotope Stage (MIS) 6 (186–127 ka). An alternative interpretation, based on pollen analysis and stratigraphic correlations, places the MEG further back in the Quaternary, with an age equivalent to MIS 12 (474–427 ka), or even older. To re-evaluate this issue in the Swiss glaciation history, a multi-dating approach was applied to proglacial deltaic ‘Hohenschotter’ deposits in locations outside the ice extent of the Last Glacial Maximum. Results of U/Th and luminescence dating suggest a correlation of the investigated deposits with MIS 6 and hence with the Riss Glaciation. Cosmogenic burial dating suffered from large measurement uncertainties and unusually high 26Al/10Be ratios and did not provide robust age estimates.

Carrier-free measurements of natural 10Be/9Be ratios at low energies

Abstract: At ETH Zurich a new method to measure directly the natural 10 Be/ 9 Be ratio of a sample with the compact (0.6 MV) AMS system Tandy has been developed, which allows us to use standard sample preparation methods and AMS techniques. Our results show that carrier-free measurements with compact AMS machines represent a fast, less expensive and more precise alternative for applications where only the relative variation of the 10 Be/ 9 Be ratio is needed. Increased source efficiency for (artificial) low carrier samples has been found. If this effect could be exploited for natural samples, it would open the field for other applications like in situ 10 Be-dating of quartz with compact, low energy AMS systems.

Glacier activity at the Lateglacial / Holocene transition inferred from the Swiss Alps

Abstract: High-alpine environments react sensitively to changes in climate Depending on size, catchment area and valley topography, mountain glaciers response relatively fast with advances and recessions to shifts in temperature and precipitation (eg Oerlemans, 2005) About half of the present glaciers in the Swiss Alps are located in the highest mean altitudes areas Past glacier activity beyond actual glacier extent is sometimes easily identified, such as the moraines related to the Little Ice Age Records of older glacier activity, however, are usually less abundant Lateglacial glacier advances are often documented by moraine complexes