Thermal Regime and Evolution of the Congo Basin as an Intracratonic Basin - Geology and Resource Potential of the Congo Basin - page 227

a

b

c

d

Fig. 12.7 Density of the model domain as convective instabilities
form and the lateral change in density drives horizontal flow of the
transition region. ( a ) Density at 0 Myr, which is the model initial
condition with a 100 km wide transition zone between lithosphere
thickness of 100 km on the left and 200 km on the right. ( b ) 50 Myr:
where a single drip-like instability has formed due to the corner flow set

up by the transition in lithosphere thickness. ( c ) 100 Myr: where
convective instabilities have formed beneath both the thick and thin
lithosphere with a characteristic spacing of roughly 400-600 km. ( d )
150 Myr: where the interaction between the lateral change in density
and convective instabilities has caused a change in the pattern of
instabilities, the cause of change in surface topography

elevation at two locations, within the thinner lithosphere
(1,250 km, Fig. 12.7 ) and within the thicker region of litho-
sphere (1,750 km), we find that locally the episodic change
in elevation has a magnitude of roughly 200 m, with changes
occurring over periods of 20 to 40 Ma (Fig. 12.9 ). This
prediction is assuming that the upper mantle deforms by a
very simple diffusion creep. It is more probable that the
upper mantle deforms principally by dislocation creep that

is pressure and temperature dependent (Asaadi et al. 2011 ;
L ´ vy and Jaupart 2011 ). This would increase the rate of
change of topography, as instabilities would form at supra-
exponential rates rather than simply exponential (Conrad
and Molnar 1997 ; Armitage et al. 2013 ). Edge-driven con-
vection is clearly not a basin forming mechanism, but the
changes in topography due to the natural movement of a
evolving continental lithosphere will cause regional changes