Le karst des plateaux jurassiques de la moyenne valee de l'Ardeche; datation par paleomagnetisme des phases d'evolution plio-quaternaires (aven de la Combe Rajeau)

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Publication Date

1-1-2001

Publication Title

Bulletin de la Société Géologique de France

Volume Number

172

Issue Number

1

Abstract

Thanks to its immunity, karst is an excellent recorder of environmental change, which also offers the possibility for dating. Karst records position of old base levels, in particular to which were linked horizontal underground drains located near the piezometric surface. After a base level lowering, a new drain appears at a lower level, the old perched drain being abandoned. If base level lowering is slow, the initial drain is progressively entrenched, forming a canyon. The "Combe Rajeau" cave system corresponds to this last type: a 100 m high underground canyon, continuously entrenched during the Ardeche valley downcutting. The underground river left several terraces during the entrenchment. Knowing that speleothem U/Th radiometric dating method covers only the most recent part of karst systems history, which spans over several million years, paleomagnetism has been applied to date the Combe Rajeau sediments. A more precise knowledge of the evolution phases of this system provides a better understanding of the middle Ardeche valley evolution upon which it depends.

Document Type

Article

Digital Object Identifier (DOI)

https://doi.org/10.2113/172.1.121

Language

English

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