Dating techniques in geomorphology

Après une présentation des principes physiques généraux, les procédures mises en œuvre aussi bien sur le terrain qu’en laboratoire sont abordées, à partir de l’exemple des analyses réalisées sur des alluvions sableuses issues d’une basse terrasse de la Moselle.La place des datations OSL dans la recherche géomorphologique en France et son potentiel pour les recherches futures sont décrits à travers une présentation de la diversité des environnements sédimentaires et des problématiques pouvant être traités.The general principles of the method are described first.

dating techniques in geomorphology-7

They are now largely used to date not only palaeontological or organic remains, but also minerals that characterise detrital clastic sedimentary material.

The most common methods applied to minerals are cosmogenic radionuclides, electron spin resonance (ESR) and luminescence techniques.

Much later the grain is sampled in the field and stimulated in the laboratory using either visible light for quartz (OSL As shown in fig.

2, the luminescence signal obtained by stimulation corresponds with a decay curve which shows the progressive emptying of the electrons from the traps.

Hence it underlines the increasing importance of the method to geomorphological research, especially by contributing to the development of quantitative geomorphology.

L’objectif de cet article est de proposer une présentation d’ensemble des méthodes de datations par luminescence stimulée optiquement (OSL) et de leurs applications dans le champ des recherches en géomorphologie.

The radiation () comes from radionucleides which are present in the mineral and its natural environment, mainly uranium, thorium (and their decay products), potassium, and for a small proportion from cosmic particles (Aitken, 1985).

They lead to the emission of electrons which are subsequently trapped in crystalline lattice defects.

A case study of fluvial sands from the lower terrace of the Moselle valley is then presented to describe the range of field and laboratory procedures required for successful luminescence dating.

The paper also reviews the place of OSL dating in geomorphological research in France and assesses its potential for further research, by focusing on the diversity of sedimentary environments and topics to which it can be usefully applied.

The aim of this paper is to provide people involved in geomorphological research a global overview about the principles and procedures of optical dating, from the field sampling to the age interpretation.

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