Geospatial Analysis of Fluoride Contamination in Groundwater of Southeastern Part of Anantapur District, Andhra Pradesh - Management of Natural Resources in a Changing Environment - page 60

Fig. 2 Geological map of the study area (GSI District Resource Map, Anantapur District, 1994)
alluvium occurs along the major river courses and to some extent along minor stream
courses. The Archaean crystalline rocks include granites, gneisses and Dharwarian
schists. The ground water in these formations occurs in the weathered and fractured
zones under water table and semi-confined conditions, respectively. These rock types
do not possess primary porosity. Due to fractures and weathering, they have developed
secondary porosity often giving rise to potential aquifers at depth. The degree of weath-
ering in the Archaean formation is less than 20 m depth. This weathered zone has been
tapped extensively by the dug wells and dug-cum-bore wells, which invariably tap the
fractures occurring below the weathered zone. Ground water occurring in these forma-
tions is generally developed by dug wells, dug-cum-bore wells and bore wells. The