11.3 Dynamic Denudation Accumulation Systems
E
a::
Cf)
c:
co
Q)
::;E
co
~
-....
Q)§ 400
(JC
Co Q) . -
:s! ~ 300
Cf)...,
..c c
::JQ)
Cf)E
_._ 200
0"0
Q)
Cf) Cf)
~"O 100
COc
a:::co
a
\
\
SR,,,
o 5 10
Extensional basins
20
SR so corresponds to
DR me = 50 (mm/ka)
but p<2.5 g/cm 3
Ritt b ., ocean basin
- -- Marine b. , deepening - - - -
30
40
Cent .
A /A=- 8-- 4----- 2 - ------------ 1-------- - - - 0.66
d
b
Extensional basin
b
Necessary for complete _
Drainage area A d and ß = const.
basin filling
_ -
Mechanical denudation rate DR .... = variable (m/Ma)
'\. - .,..-.,..-.....
4
,200
111 "'~."w. )........
E
Potential mean thickness of
accumulated porous sediment
25
Accumulated
sediment
/
e
IJ)
IJ)
Q)
c:
~
(J
.s::
2 :::
c:
Q)
E
"0
Q)
Cf)
o
'0
20
30
40
50
60 Ma
2 - - Ad/A b - - - - - - 1 - - - - - - -- - - - - - - - - - -- -- - - - - 0 .5
503
Fig. 11.14. Extensional basins with varying sediment
supply. a Rates of subsidence and mean clastic sedimentation SR vs. time. After 20 Ma, the basin width
is W=50 km (rate of extension 0.25 cmla) or 500 km
(2.5 cmla); the changing A,jA b ratio is shown at base
of diagram. The curves of SR correspond with different denudation rates DR (e.g. SR JOo with DR JOo ) but
take into account changing sediment porosities. Both
the continental phase of basin evolution and the occurrence of the maximum rate of subsidence are controlled by SR. A short-lived basin with lirnited SR
may first display continental deposits followed by
marine beds and finally again continental conditions.
b as Fig. 11.13b, but with short-term changes in
S~e and thus also in S~e' This may cause interrnittent complete basin filling (point I) or facies change
in marine deposition (point II). At a later stage (point
III), only long-term increased terrigenous sediment
supply only can restore continental deposition