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Sci Rep. 2015 Sep 22;5:14132. doi: 10.1038/srep14132.

Impact of climate changes during the last 5 million years on groundwater in basement aquifers.

Author information

1
OSUR-Géosciences Rennes, Université Rennes 1 - CNRS, 35000 Rennes, France.
2
BRGM, Laboratory Department, 3 av C. Guillemin, 45000 Orléans, France.
3
OSUR-ECOBIO, Université Rennes 1 - CNRS, 35000 Rennes, France.
4
Université de Nîmes, EA 7352 CHROME, 30021 Nîmes, France.
5
Aster Team Aix-Marseille Université, CNRS-IRD UM 34 CEREGE, Technopôle de l'Environnement Arbois-Méditerranée, 13545 Aix-en-Provence, France.
6
CNRS/UPS UMR 8148 IDES, Université Paris-Sud, 91400 ORSAY France; P.A. GEOTOP, Université du Québec à Montréal, Montréal Qc, H3C 3P8, Canada.

Abstract

Climate change is thought to have major effects on groundwater resources. There is however a limited knowledge of the impacts of past climate changes such as warm or glacial periods on groundwater although marine or glacial fluids may have circulated in basements during these periods. Geochemical investigations of groundwater at shallow depth (80-400 m) in the Armorican basement (western France) revealed three major phases of evolution: (1) Mio-Pliocene transgressions led to marine water introduction in the whole rock porosity through density and then diffusion processes, (2) intensive and rapid recharge after the glacial maximum down to several hundred meters depths, (3) a present-day regime of groundwater circulation limited to shallow depth. This work identifies important constraints regarding the mechanisms responsible for both marine and glacial fluid migrations and their preservation within a basement. It defines the first clear time scales of these processes and thus provides a unique case for understanding the effects of climate changes on hydrogeology in basements. It reveals that glacial water is supplied in significant amounts to deep aquifers even in permafrosted zones. It also emphasizes the vulnerability of modern groundwater hydrosystems to climate change as groundwater active aquifers is restricted to shallow depths.

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