Precise tracing of exhumation and provenance using 40Ar/39Ar geochronology of detrital white mica: the example of the Central Alps
H. Von Eynatten, J. R. Wijbrans, 2003. "Precise tracing of exhumation and provenance using 40Ar/39Ar geochronology of detrital white mica: the example of the Central Alps", Tracing Tectonic Deformation Using the Sedimentary Record, T. McCann, A. Saintot
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Single-grain 40Ar/39Ar dating of detrital white mica from Oligocene to Miocene (31–13 Ma) sediments of the North Alpine Foreland Basin in Switzerland reveals three prominent age clusters indicating cooling of the source rocks below 350–420°C in Carboniferous, Early Permian, and Tertiary times. Precise calibration of sedimentation age throughout the study area enables the thermal evolution of the hinterland in space and time to be precisely traced. Palaeozoic mica ages are documented in all samples and are used as additonal provenance indicators. Tertiary mica ages are restricted to sediments younger than 21 Ma, and are only found in central and western drainage systems. Tertiary micas document progressively increasing average cooling rates up to 34–41°C/Ma in the source area (Lepontine Dome), between 21 Ma and 14 Ma. The observed cooling rates and the time-span for rapid cooling in the source area (between 19 and 14 Ma) agree with thermal models derived from currently exposed rocks of the Lepontine metamorphic dome. This study proves that detrital mica geochronology is a robust tool for deciphering the thermal histories of ancient orogens which are no longer exposed today.
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The study of sediments and sedimentary basins in terms of their tectonic environment requires a multidisciplinary approach and has increasingly drawn both techniques and objectives from fields outside sedimentology. The application of different theoretical, experimental and empirical resources provided by structural geology, geochemistry, geophysics, scale modelling, and field geology, complement sedimentological methods, with the combined aim of achieving a deeper understanding of the origins, evolution and significance of sedimentary sequences in terms of their tectonic history.
Studies presented in this volume range across a wide spectrum from the analysis of sedimentary sequence architecture at basin scale down to the chemical properties of individual grains, and include studies from a range of tectonic settings.
The volume will be of interest to those involved with, or contemplating, studies involving the linkages between tectonics and sedimentation, as well as a wider audience to whom the results of such studies may provide fresh insight.