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Abstract. An isotopic survey, including 18 H and noble gases, has been carried out

Summary: Abstract. An isotopic survey, including 18
O, 2
H, 13
C, 14
C, 3
H and noble gases, has been carried out
since 1998 on groundwaters of the Valréas Miocene aquifer. This aquifer is situated in the South of
France, close to the Rhône valley. It consists of calcareous cemented sandstones interbeded with marl
and sand lenses. A major paleo-ria, resulting from the drastic Messinian crisis, cuts the Miocene
sediments. During the Pliocene, it was infilled with marl and clays. This Pliocene cover keeps the
aquifer confined in the South of the study area. A strong isotopic contrast is found between unconfined
and confined aquifer. The depletion in the water molecule stable isotopes occurs around 20 000 years
BP and points out the transition from the Last-Glacial to Holocene. The constant value of deuterium
excess suggests persistence of the atmospheric circulation pattern over the South of Europe since the
end of the Pleistocene. The isotopic signature of the Miocene aquifer groundwaters indicates the
perfect integration of Southern France palaeoprecipitation into the present-day regional atmospheric
frame. A reliable estimate of the warming during the Pleistocene-Holocene transition could only be
derived from stable isotopes by calibrating them against noble gas temperatures.
Climatic change during the Late Quaternary has been inferred from isotopic composition of


Source: Aeschbach-Hertig, Werner - Institut für Umweltphysik, Universität Heidelberg


Collections: Geosciences; Environmental Sciences and Ecology