Fractured Aquifers - Hydrogeology: Objectives, Methods, Applications - page 46

village wells were dug in fractured environments. Paradoxically, the
construction work (research, development, engineering) was done with
the goal of studying and using the impermeability of these rocks (tunnels,
storage of radioactive waste).
The prospecting of basement rock began in intertropical zones, but
programs with a broader scope were subsequently developed in temperate
or boreal zones.
2 AFRICAN HYDROGEOLOGY
Africa contains (Guiraud, 1988) extensive outcrops of Lower and Middle
Precambrian basement rock (Figure 21).
Figure 21 Lower and Middle Precambrian outcrops of basement rock in Africa.