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Figure 9. Geology of Kalyandurg mandal
Closepet Granite
Dolerite
Gravel
Grey Granite
Hornblende
Pink Granite
Quartz, Reef
4000 0 4000 8000 (m)
3.3 Geology and geomorphology
Kalyandurg has an undulating topography
with a general slope towards north and east.
The geology of the mandal (see Figure 9) is
comprised of Archean rocks which consist of
gneisses, schists, younger granites, quartz veins and
basic dykes. The Archaen rocks have suffered a
considerable degree of tectonic disturbance
as a result of which the rocks have been
metamorphosed and recrystallised (APGWD,
1999). The granite rocks may be separated into two
distinct groups, namely, the massive and foliated
types. The massive grey granites give rise to elevated
features while foliated rocks are found below the
plains and also occur as low dome hillocks. Dharwar
rocks, occurring as a linear schist belt within the
gneissic complex, form linear hills in the eastern
part of the mandal. Numerous basic dykes, which
are essentially dolerite in composition, traverse the
older rocks and these are exposed as long narrow
and generally persistent ridges. The length of the
dykes varies from 0.5 to 9 km and the width from
50 to 500 m. In addition to the above, alluvium of
1-7 m thickness occurs along the course of the
Pennar river and in the vicinity of minor streams
and tanks.
Located on the periphery of the Cuddapah
basin, Dhone has a geology that comprises both
crystalline and sedimentary rocks. Granites and
associated rocks with intrusive bodies like dykes and
quartz veins are encountered to the north and west
of the mandal and sedimentary rocks such as
limestones and shales with intercalation of chert
bands are found to the south and east. The areas
underlain by granites are undulating with numerous
rock outcrops. The areas underlain by the
sedimentary rocks are hilly with a steeper terrain.
Figure 10 shows Dhone’s main geomorphic units. 4
3.4 Soils
Approximately 95% of the soils in Kalyandurg
are alfisols with the remaining area covered by black
clayey soils (vertisols) (APGWD, 1999). The soils
in Dhone are also predominantly red sandy loam
soils with a depth in the range 0.3 - 1 m (APGWD,
2000). Table 3 provides information on the length
of growing period for each APRLP district based on
rainfall frequency analysis and soil water holding
capacity. The relatively short growing period in
Anantapur gives an indication of the risk involved
in rainfed cropping in this district. The inherent
advantages of the vertisols, in terms of soil water
availability, can also be seen.
Shallow and very shallow gravelly soils occur at
the base of foothills with 3-5% slope in Dhone and
4-8% slope in Kalyandurg. The gravel content of
these soils ranges from 50 to 85% and is a major
limitation on arable cultivation. Moderately deep
soils occur in gently sloping lands and deep to very
deep soils occur in valleys.
4 Despite considerable effort, obtaining a 1:50,000
groundtruthed map of Dhone proved to be impossible
during the water audit. Copies of this map could not
be found either in Kurnool or Hyderabad.
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