Toward a comprehensive provenance analysis: A multi-method approach and its implications for the evolution of the Central Alps
Published:January 01, 2004
Cornelia Spiegel, Wolfgang Siebel, Joachim Kuhlemann, Wolfgang Frisch, 2004. "Toward a comprehensive provenance analysis: A multi-method approach and its implications for the evolution of the Central Alps", Detrital thermochronology - Provenance analysis, exhumation, and landscape evolution of mountain belts, Matthias Bernet, Cornelia Spiegel
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In this study, we discuss potential problems connected with using geochronological data from foreland basins to unravel exhumation histories of the hinterland. In particular, we compare the results of a provenance analysis solely based on zircon fission-track ages from the foreland basin with a multi-method approach based on (i) the aforementioned zircon fission-track data, (ii) Nd isotope ratios of detrital epidote, and (iii) sediment accumulation rates in the foreland basins. For the example of the Central European Alps, we demonstrate that the multi-method approach can lead to highly different interpretations in terms of hinterland exhumation and geodynamic evolution. This is due to the fact that fission-track dating on detrital zircons alone only monitors the exhumation and erosion of zircon-containing lithologies and therefore only of restricted areas of the hinterland while the combination with Nd isotope ratios on detrital epidote also includes the erosion of zircon-free or -poor units such as basic magmatic rocks. A comparison of zircon fission-track and epidote Nd data with the sediment accumulation curve shows whether hinterland exhumation was predominantly caused by tectonic or by erosional denudation. Furthermore, we discuss some problems that may arise from using geochronological data from foreland basins to assess the maturity of a mountain belt in the hinterland. Applied to the Central Alps, our combined approach shows that the metamorphic core became exposed simultaneously over large areas by one sudden pulse of exhumation between 21 and 20 Ma. The main trigger for that exhumation event was tectonic denudation which is consistent with a geodynamic setting of large-scale extension. The Central Alps did not achieve exhumational steady-state conditions before 14 Ma.