Climate change in arid and tropical humid regions
689
j, b ,~
Guina~f
'~ ~-.(~J'
/
Liberia -
Camerou~
J ~ ,
J
r/" Limits ~ m~ sand ~
I~
~
~'d'~~
I
'
s~
i Main montane forest refuges ~ ~
#v~.(
~
I ~ Improverished montane forest (locally)
~
(a~
~000" " -----EP
Breaker
Cho
~ Lowland forest
~ ~~ ~1
II Montane forest
/ ~
8000 B P
t)
*
Cap
t "t Natural limit of forest
f Southern limit of desert
Lowland forest
II Montane forest
R
I
(C) Present
Figure 25.42. The probable distribution of forest in central Africa at 20,000 and 8000 BP compared with
the present (after Hamilton, 1976). Note that the existence of Greater Lake Chad at 8000 BP is now
questioned.
balanced with the present climate conditions, but have registered many climate changes in
the past, which makes the interpretation difficult. In Chapter 20, examples of different deep
weathering profiles, corresponding to humid tropics and extratropical regions, are shown.
The latter are located in Europe, Australia, India and USA; weathering can even be
Jurassic. From all these works, it can be stated that the principal period of deep weathering
took place in Mesozoic-lower Tertiary, when thick regoliths developed and later eroded as