Fission track ages on apatite of Bergell rocks from Central Alps and Bergell boulders in Oligocene sediments |
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| Authors: | Günther A Wagner Donald S Miller Emilie Jäger |
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| Institution: | Max-Planck-Institut für Kernphysik, Heidelberg, Federal Republic of Germany;Department of Geology, Rensselaer Polytechnic Institute, Troy, NY 12181, USA;Laboratorium für Isotopengeologie, Universität Bern, Bern, Switzerland |
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| Abstract: | Previous radiometric dating studies indicated that the Bergell region, in contrast to other regions of the Central Alps, experienced an early, rapid uplift, but with decreasing rate. Furthermore, there is also a geological record of the early uplift history of the Bergell granite by the existence of boulders which were derived from this granite and which occur in the Late Oligocene sediments of the Po plain.In this work the uplift history of the Bergell is studied in more detail by fission track dating of additional apatites from the Bergell region. Secondly, by determining apatite fission track ages the granitic boulders of the Po plain can be re-assigned to their original vertical position within the Bergell intrusive before erosion removed them in Late Oligocene time. A rather conservative estimate replaces them 6 km above the present morphology of the Bergell massif. Thus, the thickness of the Bergell granite must have been at least 8 km.Generally, fission track studies on boulders may become an important tool to study the vertical extent of mountain chains during the geological past. |
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