Karst Aquifers - Hydrogeology: Objectives, Methods, Applications - page 60

• the spring has always been an outlet located along the Cavaillon
fault trace, the location of the deep drainage being a result of a more
favorable rock type in terms of porosity. It is, however, diffi cult, in
such an arrangement, to justify the reason for a drainage more than
300 m deep rising up the current exsurgence, given that limestone is
normally bedded and fractured. The density of discontinuities should
allow the emplacement of outlets near the top of the karst aquifer, as
is commonly seen elsewhere (Ford & Williams, 1989). However, the
difference in potential energy between recharge area and exsurgence
(analogous to difference in electrical potential) requires only that water
fl ow from one point to another, without dictating the path that the
water will take;
• the spring uses an inherited karst morphology (chasm or swallow
hole), and emplaced during a Messinian paleogeographic context very
different today's (Julian & Nicod, 1984; Mudry & Puig, 1991; Clauzon
et al ., 1997).
Figure 32 Discharge from the Fontaine de Vaucluse, from 2001 to 2004. The rapid spikes
during fl ood periods indicate a highly evolved karstifi cation. The slow recessions highlight the
size of the reserves. Note: the fl ood peaks were not acquired.
The exploration robot's observations of karrens in the walls of the chasm
at a depth of 250 m could indicate a phase during which the fountain was
dry, and the presence of Pliocene lithophages in the basin support the second
hypothesis (Figure 33). The system would then have been emplaced during
the Messinian, or even at an earlier period, with a very low regional base
level, the aquifer being drained by an outlet located more to the south or