Karst Aquifers - Hydrogeology: Objectives, Methods, Applications - page 54

galleries of the abandoned army outpost in Albion, South France),
where they amount to less than one L/minute, or in the underground
Albion river in Saint-Christol (Vaucluse), where they can reach several
tens of L/second;
• the saturated zone, characterised by microfissured blocks, large
drainage passageways, and annex-to-drain systems.
2.2 Examples in France
On the scale of a large rock unit, the spatial organisation of a karst system
can reveal itself to be very complex, requiring an in-depth knowledge of
the local geologic structure and paleogeography in order to be understood.
The above vertical structure can also be lateral. For example, in the Berger
chasm system (Vercors), water circulates primarily at the roof of the marl
underlying the Urgonian limestone (Figure 27). The saturated zone is quasi-
nonexistant, except in the distal part of the system, where the monoclinal
structure gives way to a synclinal basin enclosing a saturated zone draining
towards the spring at the Cuves de Sassenage.
Figure 27 Spatial organization of fl ows through the Berger chasm (Vercors, France).
In the Atlantic Pyrenees, the underground hydrologic system of the Saint
Vincent river (Lonné-Peyret chasm, Pierre-Saint-Martin chasm, Arphidia
cave) totals over 100 km of explored galleries, containing multiple rivers.
The water infi ltrated into canyons circulates at the roof of the Paleozoic
substratum. At the Pierre-Saint-Martin, the lowering of the regional base