U Isotope Systematics of Groundwaters from the Triassic Aquifer of the Northeastern Paris Basin and of the Rhine Graben, France

Groundwaters and spring waters from the French Lower Triassic Sandstones (LTS) and the Muschelkalk aquifers have been measured for U concentrations and activity ratios. All are clearly enriched in 234U, independently of thestratigraphic level and the geographic region. Attempts have been made to derive flow rates in the case of the northeastern Paris Basin, indicating that, although the flow rate is quite low (∼ 0.05 m/y), LTS groundwaters cannot be considered as completely stagnant in this area.