Focused erosion in the Alps constrained by fission-track ages on detrital apatites
Published:January 01, 2009
Marco G. Malusà, Massimiliano Zattin, Sergio Andò, Eduardo Garzanti, Giovanni Vezzoli, 2009. "Focused erosion in the Alps constrained by fission-track ages on detrital apatites", Thermochronological Methods: From Palaeotemperature Constraints to Landscape Evolution Models, F. Lisker, B. Ventura, U. A. Glasmacher
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Fission-track dating on detrital apatites from modern sands of the Po Delta is used for a provenance study of sediments in the Po River basin. Analysed samples show a fission-track grain-age distribution characterized by two prominent peaks at 7.7 Ma and 17 Ma. The youngest peak accounts for 46% of the total population of dated grains. This young component in the grain-age distribution is consistent with bedrock cooling ages observed in the Western Alps between the External Massifs and the Houiller unit, as well as in the Lepontine dome of the Central Alps and in the Miocene foredeep units of the Apennines, that overall represent only 12% of the orogenic source area. Results suggest that most of the sediment load in the last 102–105 years was supplied by focused erosion of relatively small areas that experienced short-term erosion rates one order of magnitude higher than in the rest of the belt.
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Thermochronological Methods: From Palaeotemperature Constraints to Landscape Evolution Models
Thermochronology - the use of temperature-sensitive radiometric dating methods to reconstruct the thermal histories of rocks - has proved to be an important means of constraining a wide variety of geological processes. Fission track and (U–Th)/He analyses of apatites, zircons and titanites are the best-established and most sensitive methods for reconstructing such histories in the uppermost kilometres of the crust, over time scales of millions to hundreds of millions of years.
The papers published in this volume are divided into two sections. The first section on ‘New approaches in thermochronology’, presents the most recent advances of existing thermochronological methods and demonstrates the progress in the development of alternative thermochronometers and modelling techniques.
The second section, ‘Applied thermochronology’, comprises original papers about denudation, long-term landscape evolution and detrital sources from the European Alps, northwestern Spain, the Ardennes, the Bohemian Massif, Fennoscandia and Corsica. It also includes case studies from the Siberian Altai, Mozambique, South Africa and Dronning Maud Land (East Antarctica) and reports an ancient thermal anomaly within a regional fault in Japan.