Sixteen boulder and bedrock surfaces related to the Flims landslide (volume 8–12 km
3) were dated with
36Cl and
10Be. Exposure ages range from 4900
±
250 yr to 15,440
±
1480 yr, including corrections ...made due to snow cover and karst erosion. Ages of 11,410
±
590 yr and 13,340
±
1090 yr were obtained on bedrock surfaces outside of the landslide zone. These are minima for deglaciation of Segnes valley and provide constraints on possible amounts of inherited nuclides. Based on seven boulder ages, which range from 8200
±
260 to 9520
±
990 yr, a mean of 8900
±
700 years is calculated for the Flims landslide. We exclude three outliers (one significantly older and two significantly younger than the others) and the ages from the Cassons bedrock site from the mean calculation. The latter is excluded as shielding due to snow and vegetation cover is difficult to constrain there. The oldest boulder on the landslide yielded an age (15440
±
1480 yr) more than 5000 years older than any other boulder age, suggesting that it included the surface of the pre-slide bedrock. The exposure ages are consistent with a single failure event. The erratics and patches of till lying on the landslide debris must have been carried piggy-back on top of the landslide rather than having been deposited by the late Pleistocene Vorderrhein Glacier. The Flims rockslide is about the same age as the Köfels (9800 yr) and Kandertal (9600 yr) rockslides. All three occurred during the marked transition to warmer, wetter conditions during the early Holocene.
Atmospheric circulation leaves few direct traces in the geological record, making reconstructions of this crucial element of the climate system inherently difficult. We produced a regional ...Mediterranean synthesis of paleo-proxy data from the sea surface to alpine altitudes. This provides a detailed observational context for change in the three-dimensional structure of atmospheric circulation between the Last Glacial Maximum (LGM, ~23,000 to 19,000 years ago) and the present. The synthesis reveals evidence for frequent cold polar air incursions, topographically channeled into the northwestern Mediterranean. Anomalously steep vertical temperature gradients in the central Mediterranean imply local convective precipitation. We find the LGM patterns to be analogous, though amplified, to previously reconstructed phases of enhanced meridional winter circulation during the Maunder Minimum (the Little Ice Age).
We have determined the production yields for radionuclides in Al
2O
3, SiO
2, S, Ar, K
2SO
4, CaCO
3, Fe, Ni and Cu targets, which were irradiated with slow negative muons at the Paul Scherrer ...Institute in Villigen (Switzerland). The fluences of the stopped negative muons were determined by measuring the muonic X-rays. The concentrations of the long-lived and short-lived radionuclides were measured with accelerator mass spectrometry (AMS) and γ-spectroscopy, respectively. Special emphasis was put on the radionuclides
10Be,
14C and
26Al produced in quartz targets,
26Al in Al
2O
3 and S targets,
36Cl in K
2SO
4 and CaCO
3 targets, and
53Mn in Fe
2O
3 targets. These targets were selected because they are also the naturally occurring target minerals for cosmic ray interactions in typical rocks. We also present results of calculations for depth-dependent production rates of radionuclides produced after cosmic ray μ
− capture, as well as cosmic ray-induced production rates of geologically relevant radionuclides produced by the nucleonic component, by μ
− capture, by fast muons and by neutron capture.
The quantification of geomorphic process rates on the outcrop- and the orogen-scale is important to describe accurately the interaction between the relative effects of erosion, tectonics and climate ...on landscape evolution. We report single and paired cosmogenic nuclide (
10Be,
26Al and
21Ne) derived erosion rates and exposure ages on hillslope interfluves from the tectonically active western central Andes that show a distinct spatial variation. A positive correlation of erosion rates with elevation and present-day rainfall rates is observed. Erosion rates at lower altitudes–the hyperarid
Coastal Cordillera and the
Western Escarpment with the northern part of the
Atacama Desert–are extremely low and of the order of 10–100 cm/My (nominal exposure ages 1–6 My). In contrast, erosion rates at higher altitudes–the semiarid
Western Cordillera–range up to 4600 cm/My (nominal exposure ages 0.02–0.1 My). This latter average long-term bedrock erosion rate record, suggested to be coupled to an orographically controlled pattern of rainfall, is also reflected in the pattern of denudation rates derived from a short-term decadal record of limited sediment yield data. Specifically, denudation rates calculated from sediment flux data are of a similar order of magnitude as erosion rates deduced from long-lived cosmogenic nuclides from bedrock hillslope interfluves of the
Western Cordillera. Nevertheless, the production and the supply of sediment from the western Andean slope are very limited.
Analysis of multiple cosmogenic nuclides allows simultaneous determination of erosion rates and exposure ages but also reveals complex exposure histories of non-bedrock samples, such as boulders or amalgamated clast samples. Notably, this study shows that saturation of nuclides, usually assumed in studies where only a single nuclide is analyzed, is rather the exception than the rule, as revealed by erosion island plots. Constant erosion that started much later than the formation age of the rocks or episodic erosion by spalling can partially explain non-steady-state concentrations and more complicated exposure scenarios. Furthermore, the use of multiple nuclides with different half-lives allowed us to infer that no significant variations in long-term erosion rates have occurred and that at the
Western Escarpment erosion rates have been low and constant for most of the late Neogene
. Nevertheless, the time intervals necessary to reach steady-state concentrations for cosmogenic nuclides can be quite different from those needed for landscapes to reach steady state.
Kavron Valley lies in the Kaçkar Mountain range of northeastern Anatolia and is a north–south-oriented, typically U-shaped glacial valley consisting of a main and three tributary valleys. The ...Quaternary units that outcrop in this valley have been mapped and 22 samples have been processed for surface exposure dating using cosmogenic
10Be. According to the
10Be ages, the advance of the Kavron Paleoglacier began at least 26.0±1.2
kyr ago, with the Last Glacial Maximum (LGM) advance continuing until 18.3±0.9
kyr. After this time the Kavron Paleoglacier receded, although the magnitude of this recession is still unknown. Subsequent to this retreat, the glacier most probably separated into three smaller glaciers that were restricted to the tributary valleys (Ifrit, Derebaşı and Mezovit Paleoglaciers). The main valley was definitely ice-free by 15.5±0.7
kyr ago, with the Mezovit Paleoglacier completing its recession around 15.5±0.6
kyr. A Late Glacial advance took place around 13.0±0.8 to 11.5±0.8
kyr, and Little Ice Age moraines appear to be absent. Our results from the Kavron Valley system seem to be consistent with the LGM paleoclimate record of Anatolia, which has been delineated by data gathered from lowlands and lakes, the deposition of red clay layers in the northwestern Black Sea and the deposition of Heinrich 1 layers in the North Atlantic.
To investigate muon-induced nuclear reactions leading to the production of radionuclides, targets made of C
9H
12, SiO
2, Al
2O
3, Al, S, CaCO
3, Fe, Ni, Cu, Gd, Yb and Tl were irradiated with 100 ...and 190 GeV muons in the NA54 experimental setup at CERN. The radionuclide concentrations were measured with accelerator mass spectrometry and γ-spectroscopy. Results are presented for the corresponding partial formation cross-sections. Several of the long-lived and short-lived radionuclides studied are also produced by fast cosmic ray muons in the atmosphere and at depths underground. Because of their importance to earth sciences investigations, calculations of the depth dependence of production rates by fast cosmic ray muons have been made.
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