648 
NIGERIA 150,000 ENGINEERING SOIL MAP OF NIGERIA sheet 39SE 
t'4£' 
16*1 S' 
Scala 1.50.0 0 0 
AIR PHOTOGRAPHY 
NOV. 1976 
INDFX TO AW0WINÇ SHEET 
hwJne 
sw 
SE 
SW 
SE 
m 
NE 
NW 
NE 
SW |SE 
SW |S£ 
INDEX 
Towns A Vlllagss- - <Q3> 
Main Roads 
Main paths 
Rivers . . . 
SM Silty sand-- |rn~] 
SM-SC Silty sand Clayeyjand mixture1 | 
SC Clayey sand 
ML Silt of low compressibility , pm 
MH Silt of high compressibility ngg 
CL Clay of low plasticity-- |jpp 
CH Clay of high plasticity 
J Jin glin (Calcareous deposit) 
True North 
A 
Prepared by 
N BRRI 
LA GOS 
Fl G. 4 
A typica 
in India 
Spec: 
a soluble calcium bicarbonate Ca(HC03>2. The later 
is then washed down the slopes of depressions and 
hollows of undulating topography to form calcium 
carbonate, after water and carbon dioxide have been 
evaporated, as illustrated in the equation below:— 
CaCo3 + H2 0 + C02 Ca(HCC>3)2. 
4.1 Location of calcrete in Indian desert 
The calcrete bearing areas in desert terrain of 
Rajaisthan in North-Western part of India, had bear 
interpreted from the aerial photographs. (Nanda 
1970). They are interdunal sandy plain or shallow 
depressions of light grey tone, showing signs of 
wind erosion and with scattered bushes. 37 such 
sites had been identified in an area of 13,000 km2. 
Field verification revealed that 75% of the site con 
firm air-photo interpretation. A typical stereopair 
is shown in Fig. 7. 
4.2 Frospecting of calcrete in sandy terrain 
of Northern Nigeria. 
Similarly, air photo interpretation study for the 
location of calcrete has been carried out in the 
sandy terrain of North-Cast Nigeria (Bomo and 
Kano States), covering an area of 18000 km2. The 
calcrete has predominantly been interpreted to be 
in the interdunal sandy plain and shallow depres 
sions with light grey tone, showing signs of wind 
erosion and without remarkable vegetation, as it has 
been the ca 
landform en 
hollow. Th 
tone withou 
is shown in 
occuracy of 
the order o; 
5. conclus: 
(i) Air 
and 
higV 
regj