Appendix A4

In order to constrain the evolution of the boundary conditions for the clay pore waters over time, the stable isotopic composition of meteoric recharge that feeds the aquifers needs to be known over the considered evolution time. The temporal variability of the stable isotopic signature of recharge water at a given site depends mainly on temperature and therefore on climate. Provided the evolution of surface temperature can be constrained on the basis of independent evidence and the relationship between temperature and isotopic composition of recharge is known, the evolution of the latter can be estimated for the periods of interest. For this purpose, previous works (e.g. Marivoet et al. 2000) used the world-wide correlation between mean annual temperature and O, H isotope compositions in precipitation (Dansgaard 1964, Fricke &amp O’Neil 1999:

Natural Tracer Profiles Across Argillaceous Formations: The CLAYTRAC Project

Appendix A4

Aspects Pertinent to the Evolution of Boundary and Initial Conditions Over Time