Geography Reference
In-Depth Information
less if they are unstructured because of the high granites resistivity to
weathering due to high contents of quartz in their petrographic structures.
Basic rocks and schists may have good potential aquifer due to their altered
upper part often very well developed. This regolith especially has a capacitive
function that plays an important role in deferred groundwater recharge and
therefore may be a useful aquifer for hand dug wells. So, the most interesting
potentials are recorded at ultra-basic rocks and in carbonate formations.
Volcano-sedimentary can be a good aquifer with a good groundwater
potential. However, schists present a moderate potential and low potential are
found on granites and acid volcanic rocks.
II.3. Lineaments
They have been subject of several studies in the West Africa (Biémi,
Engelec, Kouamé, Savadogo Savané). Their involvement in the research area
conducive to the implementation of drilling is well established today. On
satellite imagery, lineaments correspond to image discontinuities and are
expressed by the juxtaposition or layering simple physiographic elements or
composite varied natures (morphology, hydrography, vegetation, surface
difference in tone ...) where, different parties are rectilinear relationship or
slightly curvilinear (Kouamé, 1999). On the ground there are the lithological
discontinuities (contact between different formations) or structural (fault, joint,
dyke…) (GRONAYES et al.). Four major lineament directions are noted in the
region. The N60-N50 directions (Fig. 5) are the most representative with
respectively 10.8% and 10.5% of total lineament length followed by the N170-
N180 and N0-N10 and finely the N100 direction that represents about 8% of
the total lineament length. The preponderance of the N60 and N50 is
essentially due to a regional tectonic accident called main transcurrent zone
(MTZ) which represents a regional shear zone that affected the whole region
.
II.4. Slope
The plain occupies most part of the area and the terrain is often marked by
plateaus covered by a thick lateritic mantle. Slopes are higher especially in the
southern west part of Kédougou in vicinity of Mako and in the center of the
study area where they can reach 32% (Fig. 6). The north side of the study area
land becomes relatively flat with few elevations and gentle slope near the
