Multi-isotopic Approach for Dating Groundwater in the Laurentides, Southern Quebec, Canada

The age of the groundwater is an important parameter that plays a part in estimating the sustainability of the resource. This parameter is difficult to quantify, as samples (i.e., water wells) often contain a mixture of waters of different origins and residence times. Some tracers, such as radiogenic helium, have multiple sources that cannot be quantified. Here, we present the results of a study on water dating in a region near Montreal, Quebec. Four dating methods were compared: 3H-3He, 14C, U-Th/4He, and 234U/238U. At regional level, the results show a relationship between different ages, suggesting the presence of mixed water masses at aquifer level. The ages found are also put into context with the last deglaciation of the North American continent.