The Great Trap region of the Deccan covers the whole district.
It is entirely of volcanic formation. The volcanic portion consists
of compact, stratified basalts, and an earthy trap. The basalts
are the most conspicuous geological feature. To the west they
lie in flat-topped ranges, separated by valleys, trending from
west to east. In some flows the- basalt is columnar and then it
weathers into the fantastic shapes. The formation at the base
of the traps is chiefly amygdaloidal, containing quartz in vertical
veins, crystals and zeolitic minerals, especially apophyllite
weathering into a gray soil. The absence of laterite, which caps
the summits of the hills to the south, is a curious feature in
the geology of the area. The basalt is either fine textured or
it is coarse and nodular.
Soils : As regards the
soil, the valleys are filled with disintegrated basalt of various
shades from gray to black, washed down by rain. It is of argillaceous
nature. This soil is not favourable to the growth of large trees
but it is very fertile for cereals and pulses. The black soil
contains high alumina and carbonates of calcium and magnesium
with variable amounts of potash, low nitrogen and phosphorus.
The red soil is less common and is suitable for cultivation
under a heavy and consistent rainfall.
Economic Minerals :
Lime nodules and Kankar are found practically all over the district.
The lime nodules yield a very good lime, slightly hydraulic,
but not sufficiently so to be used under water. Mixed with pounded
bricks and sand it forms a fair mortar. The trap rock is very
useful for building purposes.
Occurrence of iron ore is reported near Bhadra in the Surgana
mahal. The deposits consist of magnetite and ilmenite sands
occurring in sporadic patches, but it is not of any economic