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  • 1
    Publication Date: 2016-07-26
    Description: The late-Neogene evolution of the European Alps was influenced by both tectonic and climatically driven erosion processes, which are difficult to disentangle. We use low-temperature thermochronometry data from surface and borehole samples in the Aar massif–Rhône valley (Swiss central Alps) to constrain the exhumation history of the region. Multiple exhumation events are distinguished and linked to regional-scale tectonic deformation (before 5 Ma), short-lived climatically driven orogen contraction (between 4 and 3 Ma), and glacial valley carving since ~1 Ma. Compared with previous studies, we clearly show the existence of two separate exhumation phases in the Late Miocene–Pliocene and better constrain the onset of glacial valley carving. The hydrothermal activity and geothermal anomalies currently observed in the borehole have been local and short-lived, with only a minor influence on thermochronometric observations. We thus suggest that late-stage glacial valley carving may have triggered topography-driven fluid flow and transient hydrothermal circulation. This article is protected by copyright. All rights reserved.
    Print ISSN: 0954-4879
    Electronic ISSN: 1365-3121
    Topics: Geosciences
    Published by Wiley
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  • 2
    Publication Date: 2011-02-22
    Print ISSN: 0278-7407
    Electronic ISSN: 1944-9194
    Topics: Geosciences
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
    Publication Date: 2012-01-12
    Description: The late Neogene–Quaternary exhumation history of the European Alps is the subject of controversial findings and interpretations, with several thermochronological studies arguing for long-term steady state exhumation rates, while others have pointed to late Miocene–Pliocene exhumation pulses associated with tectonic and/or climatic changes. Here, we perform inverse thermal-kinematic modeling on dense thermochronological data sets combining apatite fission track (AFT) data from the literature and recently published apatite (U-Th-Sm)/He (AHe) data along the upper Rhône valley (Aar and Aiguilles Rouges massifs, Swiss Alps) in order to derive precise estimates on the denudation and relief history of this region. We then apply forward numerical modeling to interpret cooling paths quantified from apatite 4He/3He thermochronometry, in terms of denudation and relief-development scenarios. Our modeling results highlight the respective benefits of using AFT/AHe thermochronology data and 4He/3He thermochronometry for extracting quantitative denudation and relief information. Modeling results suggest a late Miocene exhumation pulse lasting until ∼8–10 Ma, consistent with recently proposed exhumation histories for other parts of the European Alps, followed by moderate (∼0.3–0.5 km Myr−1) denudation rates during the late Miocene/Pliocene. Both inverse modeling and 4He/3He data reveal that the late stage exhumation of the studied massifs can be explained by a significant increase (∼85–100%) in local topographic relief through efficient glacial valley carving. Modeling results quantitatively constrain Rhône valley carving to 1–1.5 km since ∼1 Ma. We postulate that recent relief development within this part of the Swiss Alps is climatically driven by the onset of major Alpine glaciations at the mid-Pleistocene climate transition.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 4
    Publication Date: 2011-10-01
    Description: Significant increase in relief of the European Alps during mid-Pleistocene glaciations Nature Geoscience 4, 688 (2011). doi:10.1038/ngeo1242 Authors: Pierre G. Valla, David L. Shuster & Peter A. van der Beek Some of Earth’s greatest relief occurs where glacial processes act on mountain topography. This dramatic landscape is thought to be an imprint of Pleistocene glaciations. However, whether the net effect of glacial erosion on mountains is to increase or decrease relief remains disputed. It has been suggested that in the European Alps, the onset of widespread glaciation since the mid-Pleistocene climate transition led to the growth of large, long-lived and strongly erosive alpine glaciers that profoundly influenced topography. Here we use 4He/3He thermochronometry and thermal-kinematic models to show that the Rhône Valley in Switzerland deepened by about 1–1.5 km over the past one million years. Our results indicate that while the valley was incised and back-cut, high-altitude areas were preserved from erosion. We find an approximately two-fold increase in both local topographic relief and valley concavity, which occurred around the time of the mid-Pleistocene transition. Our results support the proposed link between the onset of efficient glacial erosion in the European Alps and the transition to longer, colder glacial periods at the middle of the Pleistocene epoch.
    Print ISSN: 1752-0894
    Electronic ISSN: 1752-0908
    Topics: Geosciences
    Published by Springer Nature
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  • 5
    Publication Date: 2011-02-01
    Description: Constraining the uplift and exhumation history of the Venezuelan Andes is critical for understanding the complex geodynamic evolution of northern South America. We present new apatite fission-track (AFT) data from the Sierra Nevada de Merida in the central Venezuelan Andes and compare the results with previously published AFT data for the Sierra La Culata (El Carmen block) to the north. The AFT data are combined with three-dimensional thermal modeling to constrain the exhumation and relief history of both blocks, which show significant differences. The Sierra Nevada indicates exhumation rates of [~]1.7 km/m.y. from ca. 10 Ma until 4 Ma, decreasing to [~]0.4 km/m.y. from 4 Ma to present; the El Carmen block, in contrast, underwent much more rapid recent exhumation, with rates of [~]1.4 km/m.y. since 4 Ma. The data suggest [~]4 km of relative rock uplift of the Sierra La Culata with respect to the Sierra Nevada since 4 Ma and support significant uplift of basement blocks along major preexisting discontinuities during transpression in the Northern Andes, linked to accretion of the Panama arc and indentation of the Maracaibo block. Rapid Middle-Late Miocene exhumation in the Sierra Nevada resulted from surface uplift that caused the Late Miocene deflection of the Orinoco River inferred from the Neogene sedimentary record.
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
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