Wölfler Andreas, Stüwe Kurt, Danišík Martin, Evans Noreen J
Institute of Earth Sciences, University of Graz, Universitätsplatz 2, 8010 Graz, Austria.
John de Laeter Centre for Isotope Research, Applied Geology, Curtin University of Technology, GPO Box U1987, Perth WA 6845, Australia; Departement of Earth & Ocean Sciences, Faculty of Science & Engineering, University of Waikato, Hillcrest Road, Hamilton, New Zealand.
Tectonophysics. 2012 May 14;541-543(6):1-18. doi: 10.1016/j.tecto.2012.03.016.
According to new apatite fission track, zircon- and apatite (U-Th)/He data, we constrain the near-surface history of the southeastern Tauern Window and adjacent Austrolapine units. The multi-system thermochronological data demonstrate that age-elevation correlations may lead to false implications about exhumation and cooling in the upper crust. We suggest that isothermal warping in the Penninic units that are in the position of a footwall, is due to uplift, erosion and the buildup of topography. Additionally we propose that exhumation rates in the Penninic units did not increase during the Middle Miocene, thus during the time of lateral extrusion. In contrast, exhumation rates of the Austroalpine hangingwall did increase from the Paleogene to the Neogene and the isotherms in this unit were not warped. The new zircon (U-Th)/He ages as well as zircon fission track ages from the literature document a Middle Miocene exhumation pulse which correlates with a period of enhanced sediment accumulation during that time. However, enhanced sedimentation- and exhumation rates at the Miocene/Pliocene boundary, as observed in the Western- and Central Alps, cannot be observed in the Eastern Alps. This contradicts a climatic trigger for surface uplift, and makes a tectonic trigger and/or deep-seated mechanism more obvious to explain surface uplift in the Eastern Alps. In combination with already published geochronological ages, our new data demonstrate Oligocene to Late Miocene fault activity along the Möll valley fault that constitutes a major shear zone in the Eastern Alps. In this context we suggest a geometrical and temporal relationship of the Katschberg-, Polinik-Möll valley- and Mur-Mürz faults that define the extruding wedge in the eastern part of the Eastern Alps. Equal deformation- and fission track cooling ages along the Katschberg-Brenner- and Simplon normal faults demonstrate overall Middle Miocene extension in the whole alpine arc.
根据新的磷灰石裂变径迹、锆石和磷灰石（U-Th）/He数据，我们确定了陶恩窗东南部及相邻的澳大利亚拉平单元的近地表演化历史。多体系热年代学数据表明，年龄-海拔相关性可能会对上地壳的剥露和冷却产生错误的推断。我们认为，位于下盘位置的彭宁单元的等温翘曲是由于隆升、侵蚀和地形的形成。此外，我们提出彭宁单元的剥露速率在中新世中期并未增加，即在侧向挤压时期。相反，奥地利阿尔卑斯上盘的剥露速率从古近纪到新近纪确实增加了，且该单元的等温线并未翘曲。新的锆石（U-Th）/He年龄以及文献中的锆石裂变径迹年龄记录了一个中新世中期的剥露脉冲，这与该时期沉积物堆积增强的阶段相关。然而，在西阿尔卑斯和中阿尔卑斯观察到的中新世/上新世边界处沉积物堆积和剥露速率的增强，在东阿尔卑斯并未出现。这与表面隆升的气候触发因素相矛盾，使得构造触发因素和/或深部机制更明显地成为解释东阿尔卑斯表面隆升的原因。结合已发表的地质年代年龄，我们的新数据表明，沿着构成东阿尔卑斯主要剪切带的默尔山谷断层，存在渐新世到晚中新世的断层活动。在此背景下，我们提出了卡奇贝格、波林尼克-默尔山谷和穆尔-米尔茨断层的几何和时间关系，这些断层界定了东阿尔卑斯东部的挤压楔体。沿着卡奇贝格-布伦纳和辛普朗正断层的同等变形和裂变径迹冷却年龄表明，整个阿尔卑斯弧在中新世中期整体处于伸展状态。
