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  • 1
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    Synchronous Last Glacial Maximum across the Anatolian peninsula (2015)
    Geological Society (of London)
    Details
    Publication Date: 2015-12-13
    Description: Uludağ is a prominent mountain in northwestern Turkey where glacial deposits have been documented in the Kovuk Valley and the glacial history has been reconstructed based on 31 cosmogenic 10 Be exposure ages from glacially transported boulders and bedrock. The results suggest that the Kovuk Glacier began advancing before 26.5±1.6 ka. It reached its maximum extent at 20.3±1.3 ka, followed by a re-advance at 19.3±1.2 ka, both during the global Last Glacial Maximum (LGM) within Marine Isotope Stage 2. The timing of the LGM glaciations in the Kovuk Valley is consistent with the investigated LGM glaciations in other mountains of Anatolia, the Mediterranean and the Alps. Based on the geomorphological ice margin reconstruction and using the accumulation/ablation area ratio (AAR) approach, the equilibrium line altitude (ELA) of the Kovuk LGM glacier was c. 2000 m above sea level for an estimated AAR of 0.67. This indicates a c. 1000 m lowering of the ELA for the LGM compared with the modern ELA estimate. These lines of evidence are consistent with the LGM glaciers that have been documented elsewhere in the Anatolian Mountains. Supplementary material: An input file for exposure age calculation in the CRONUS-Earth online calculator and an KML file for sample locations are available at http://www.geolsoc.org.uk/SUP18878
    Print ISSN: 0305-8719
    Electronic ISSN: 2041-4927
    Topics: Geosciences
    Published by Geological Society (of London)
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  • 2
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    Near-synchronous interhemispheric termination of the last glacial maximum in mid-latitudes (2006)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2006-06-10
    Description: Isotopic records from polar ice cores imply globally asynchronous warming at the end of the last glaciation. However, 10Be exposure dates show that large-scale retreat of mid-latitude Last Glacial Maximum glaciers commenced at about the same time in both hemispheres. The timing of retreat is consistent with the onset of temperature and atmospheric CO2 increases in Antarctic ice cores. We suggest that a global trend of rising summer temperatures at the end of the Last Glacial Maximum was obscured in North Atlantic regions by hypercold winters associated with unusually extensive winter sea ice.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Schaefer, Joerg M -- Denton, George H -- Barrell, David J A -- Ivy-Ochs, Susan -- Kubik, Peter W -- Andersen, Bjorn G -- Phillips, Fred M -- Lowell, Thomas V -- Schluchter, Christian -- New York, N.Y. -- Science. 2006 Jun 9;312(5779):1510-3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Lamont-Doherty Earth Observatory (L-DEO), Palisades, NY 10964, USA. schaefer@ldeo.columbia.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/16763146" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 3
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    Regional synthesis of Mediterranean atmospheric circulation during the Last Glacial Maximum (2008)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2008-08-02
    Description: 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, approximately 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).〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kuhlemann, J -- Rohling, E J -- Krumrei, I -- Kubik, P -- Ivy-Ochs, S -- Kucera, M -- New York, N.Y. -- Science. 2008 Sep 5;321(5894):1338-40. doi: 10.1126/science.1157638. Epub 2008 Jul 31.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute for Geosciences, University of Tuebingen, Sigwartstrasse 10, D-72076 Tuebingen, Germany. kuhlemann@uni-tuebingen.de〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18669823" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 4
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    Constant denudation rates in a high alpine catchment for the last 6 kyrs (2016)
    Wiley
    Details
    Publication Date: 2016-10-23
    Description: ABSTRACT Terrestrial cosmogenic nuclides (TCN) have widely been used as proxies in determining denudation rates in catchments. Most studies were limited to samples from modern active streams, thus little is known about the magnitude and causes of TCN variability on millennial time scales. In this work we present a 6 kyrs long, high resolution record of 10 Be concentrations (n = 18), which were measured in sediment cores from an alluvial fan delta at the outlet of the Fedoz Valley in the Swiss Alps. This record is paired with a three-year time series (n = 4) of 10 Be measured in sediment from the active stream currently feeding this fan delta. The temporal trend in the 10 Be concentrations after correction for postdepositional production of 10 Be was found to be overall constant and in good agreement with the modern river 10 Be concentration. The calculated mean catchment-wide denudation rate amounts to 0.73 ± 0.18 mm/yr. This fairly constant level of 10 Be concentrations can be caused by a constant denudation rate over time within the catchment or alternatively by a buffered signal. In this contribution we suggest that the large alluvial floodplain in the Fedoz Valley may act as an efficient buffer on Holocene time scales in which sediments with different 10 Be signatures are mixed. Therefore, presumable variations in the 10 Be signals derived from changes in denudation under a fluctuating Holocene climate are only poorly transferred to the catchment outlet and not recorded in the 10 Be record. However, despite the absence of high frequency signals, we propose that the buffered and averaged 10 Be signal could be meaningfully and faithfully interpreted in terms of long-term catchment-averaged denudation rate. Our study suggests that alluvial buffers play an important role in regulating the 10 Be signal exported by some alpine settings that needs to be taken into account and further investigated. This article is protected by copyright. All rights reserved.
    Print ISSN: 0197-9337
    Electronic ISSN: 1096-9837
    Topics: Geography , Geosciences
    Published by Wiley
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  • 5
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    Multi-method (14C, 36Cl, 234U/230Th) age bracketing of the Tschirgant rock avalanche (Eastern Alps): Implications for absolute dating of catastrophic mass-wasting (2016)
    Wiley
    Details
    Publication Date: 2016-11-01
    Description: ABSTRACT Correct and precise age determination of prehistorical catastrophic rock-slope failures prerequisites any hypotheses relating this type of mass wasting to past climatic regimes or palaeo-seismic records. Despite good exposure, easy accessibility and a long tradition of absolute dating, the age of the 230 million-m 3 carbonate-lithic Tschirgant rock avalanche event of the Eastern Alps (Austria) still is relatively poorly constrained. We herein review the age of mass-wasting based on a total of seventeen absolute ages produced with three different methods ( 14 C, 36 Cl, 234 U/ 230 Th). 36 Cl cosmogenic surface exposure dating of five boulders of the rock avalanche deposit indicates a mean event age of 3.06 ± 0.6 ka. 234 U/ 230 Th dating of soda-straw stalactites formed in microcaves beneath boulders indicate mean precipitation ages of three individual soda straws at 3.20 ± 0.26 ka, 3.04 ± 0.10 ka and 2.81 ± 0.15 ka; notwithstanding potential internal errors, these ages provide an 'older-than' ( ante quam ) proxy for mass-wasting. This article is protected by copyright. All rights reserved. Based on radiocarbon ages (nine sites) only, it was previously suggested that the present rock avalanche deposit represents two successive failures (3.75 ± 0.19 ka BP, 3.15 ± 0.19 ka BP). There is, however, no evidence for two events neither in surface outcrops nor in LiDAR derived imagery and drill logs. The temporal distribution of all absolute ages ( 14 C, 36 Cl, 234 U/ 230 Th) also does not necessarily indicate two successive events but suggest that a single catastrophic mass-wasting took place between 3.4 and 2.4 ka BP. Taking into account the maximum age boundary given by reinterpreted radiocarbon datings and the minimum U/Th-ages of calcite precipitations within the rock avalanche deposits, a most probable event age of 3.01 ± 0.1 ka BP can be proposed. Our results underscore the difficulty to accurately date catastrophic rock slope failures, but also the potential to increase the accuracy of age determination by combining methods. This article is protected by copyright. All rights reserved.
    Print ISSN: 0197-9337
    Electronic ISSN: 1096-9837
    Topics: Geography , Geosciences
    Published by Wiley
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  • 6
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    Holocene glacier culminations in the Western Alps and their hemispheric relevance (2012)
    Geological Society of America (GSA)
    In: Geology
    Details
    Publication Date: 2012-10-01
    Description: The natural variability of Holocene climate defines the baseline to assess ongoing climate change. Greenland ice-core records indicate warming superimposed by abrupt climate oscillations in the early Holocene, followed by a general cooling trend throughout the middle and late Holocene that culminated during the Little Ice Age (LIA). Tropical precipitation changes correlate with these patterns throughout the Holocene. Here we use mountain glaciers in the European Alps to reconstruct the regional Holocene climate evolution and to test for a link between mid-latitude, North Atlantic, and tropical climate. Our precise 10 Be chronology from Tsidjiore Nouve Glacier, western Swiss Alps, indicates a glacier culmination during the earliest Holocene ~11.4 k.y. ago, likely related to the Preboreal Oscillation. Based on our data, no Holocene glacier advance of similar amplitude occurred until ~3.8 k.y. ago, when the glacier reached LIA limits. The 10 Be ages between 500 and 170 yr correspond to the LIA, while the youngest 10 Be ages overlap with the historically recorded post-LIA glacier positions. Integrating our data with existing records, we propose a hemispheric climate link between the Alps, North Atlantic temperature, and tropical precipitation patterns for the Holocene, supporting the concept of a pervasive climate driver. These findings from northern mid-latitudes are consistent with the hypothesis formulated for the tropics that the Earth’s thermal equator, responding to North Atlantic temperature changes, might have migrated southward throughout the Holocene, reaching the southern turning point toward the end of the LIA.
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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  • 7
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    Debris-flow-dependent variation of cosmogenically derived catchment-wide denudation rates (2012)
    Geological Society of America (GSA)
    In: Geology
    Details
    Publication Date: 2012-10-01
    Description: Catchment-wide denudation rates (CWDRs) obtained from cosmogenic nuclides are an efficient 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-flow events significantly perturb cosmogenic nuclide ( 10 Be, 14 C) concentrations and thus CWDRs. The 10 Be concentrations decrease by a factor of two following debris-flow 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 flows, their connectivity with the trunk stream, and the ability of the system to sufficiently mix sediment from low- and high-order 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-flow initiation.
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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  • 8
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    Estimation of erosion rates at the quinghai-xizang plateau on erratic boulders using cosmogenic isotopes10Be and26Al (1998)
    Springer
    Details
    Publication Date: 1998-08-01
    Print ISSN: 1001-6538
    Electronic ISSN: 1861-9541
    Topics: Natural Sciences in General
    Published by Springer
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  • 9
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    An update on in situ cosmogenic 14C analysis at ETH Zürich (2013)
    Elsevier
    Details
    Publication Date: 2013-01-01
    Print ISSN: 0168-583X
    Electronic ISSN: 1872-9584
    Topics: Physics
    Published by Elsevier
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  • 10
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    In-situ production of radionuclides at great depths (1997)
    Elsevier
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    Publication Date: 1997-03-01
    Print ISSN: 0168-583X
    Electronic ISSN: 1872-9584
    Topics: Physics
    Published by Elsevier
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