7.10 General Discussion
383
AMPLITUDES OF MESOZOIC SEA-LEVEL CHANGES
~ SEA-LEVEL RISE (m)
100
50
BERRIAS.
VOLGIAN
,
u
ü5
(/)
- - - t .. - _____________________________________________ l ________ -------------------~ KIMMER.
=>
.
..,
::j
OXFORD.
u
ü5 CALLOV
(/)
< CI:
=>
..,
::?i BATHON.
---+ -----------------------BAJOC.
HAQ ET AL.
"GLOBAL" (HAQ ET AL. 1988)
------<--------------------------RUSSIAN PLATFORM
(SAHAGIAN ET AL.
1996)
Fig. 7.48. Comparison ofthe amplitudes ofMesozoic
"eustatic" sea-level curves derived a predominantly
from passive continental margins (Haq et al. 1988),
or b from Russian platform (intracratonic basin).
Note the different scales used for the amplitudes.
(6) Some ofthe terms and definitions ofsequence stratigraphy, introduced by the EXXON group, are not
generally accepted. The modified concept ofbase-level
change (e.g. Cross 1998; Guillocheau 1991; Homewood 1996) appears to be more universally app1icable
including continental deposits. In this case, the genetic
sequence only consists oftwo half-cycle facies tracts:
the prograding and the aggrading or backstepping tract.
Then the maximum flooding surface or an equivalent
surface representing maximum sediment accommodation space or, altemative1y, surfaces of minimum accommodation space, non-deposition, and/or erosion
are used as sequence boundaries. Also, in marine systems the maximum flooding surface is often better
suited as sequence boundary than the (partially
diachronous) base ofthe lowstand systems tract (Galloway 1989).
(7) Part of the existing uncertainties and conflicts also
stern from different scales of observation (small outSANTON.
~ CONIAC.
o w
U
~ TURON.
w
CI:
u
::i CENOM.
(/)
=>
o w
ALBIAN
~ APTIAN
Iw
CI:
U BARREM.
CI:
W
~
9 HAUTER.
VALANG.
BERRIAS.
--E-- -~"'A-LEVEL RISE (mI
100
50
-d~n.. - .. ---:-- -
----_.-.--------. __ .-.
- -..;;
------------------------------------~~
HAQ ET AL.
RUSSIAN PLATFORM
Both curves show similar general trends, but significant differences in detail. The amp1itudes of the Haqcurve, in particular, are 2.4 to 2.5 times greater than
those of the Russian p1atform. (Modified from
Sahagian et al. 1996)
crops on land vs. seismic profiles; Weimer and
Posamentier 1993) and errors inherent in the methods
to be used for deriving past relative and eustatic sealevel changes from ancient sediment sections. Apart
from the problems of stratigraphic dating and correlation, these methods include the evaluation of isostatic
compensation in response to an increasing sediment
load and sediment decompaction (e.g. Steckler et al.
1993).
(8) One of the main problems in sequence stratigraphy
is the fact that global and regional causal factors are
frequently modified and obscured by local processes in
the specific depositional environment, including variations in the supply and distribution of sediment, bioand chemo-facies. Changes in paleo-water depth reflect only local relative sea-Ievel change, which is influenced by the balance between changes in the rates at
which accommodation space forms and sediments fills
that space (Bond and Kominz 1991). These are the
383
AMPLITUDES OF MESOZOIC SEA-LEVEL CHANGES
~ SEA-LEVEL RISE (m)
100
50
BERRIAS.
VOLGIAN
,
u
ü5
(/)
- - - t .. - _____________________________________________ l ________ -------------------~ KIMMER.
=>
.
..,
::j
OXFORD.
u
ü5 CALLOV
(/)
< CI:
=>
..,
::?i BATHON.
---+ -----------------------BAJOC.
HAQ ET AL.
"GLOBAL" (HAQ ET AL. 1988)
------<--------------------------RUSSIAN PLATFORM
(SAHAGIAN ET AL.
1996)
Fig. 7.48. Comparison ofthe amplitudes ofMesozoic
"eustatic" sea-level curves derived a predominantly
from passive continental margins (Haq et al. 1988),
or b from Russian platform (intracratonic basin).
Note the different scales used for the amplitudes.
(6) Some ofthe terms and definitions ofsequence stratigraphy, introduced by the EXXON group, are not
generally accepted. The modified concept ofbase-level
change (e.g. Cross 1998; Guillocheau 1991; Homewood 1996) appears to be more universally app1icable
including continental deposits. In this case, the genetic
sequence only consists oftwo half-cycle facies tracts:
the prograding and the aggrading or backstepping tract.
Then the maximum flooding surface or an equivalent
surface representing maximum sediment accommodation space or, altemative1y, surfaces of minimum accommodation space, non-deposition, and/or erosion
are used as sequence boundaries. Also, in marine systems the maximum flooding surface is often better
suited as sequence boundary than the (partially
diachronous) base ofthe lowstand systems tract (Galloway 1989).
(7) Part of the existing uncertainties and conflicts also
stern from different scales of observation (small outSANTON.
~ CONIAC.
o w
U
~ TURON.
w
CI:
u
::i CENOM.
(/)
=>
o w
ALBIAN
~ APTIAN
Iw
CI:
U BARREM.
CI:
W
~
9 HAUTER.
VALANG.
BERRIAS.
--E-- -~"'A-LEVEL RISE (mI
100
50
-d~n.. - .. ---:-- -
----_.-.--------. __ .-.
- -..;;
------------------------------------~~
HAQ ET AL.
RUSSIAN PLATFORM
Both curves show similar general trends, but significant differences in detail. The amp1itudes of the Haqcurve, in particular, are 2.4 to 2.5 times greater than
those of the Russian p1atform. (Modified from
Sahagian et al. 1996)
crops on land vs. seismic profiles; Weimer and
Posamentier 1993) and errors inherent in the methods
to be used for deriving past relative and eustatic sealevel changes from ancient sediment sections. Apart
from the problems of stratigraphic dating and correlation, these methods include the evaluation of isostatic
compensation in response to an increasing sediment
load and sediment decompaction (e.g. Steckler et al.
1993).
(8) One of the main problems in sequence stratigraphy
is the fact that global and regional causal factors are
frequently modified and obscured by local processes in
the specific depositional environment, including variations in the supply and distribution of sediment, bioand chemo-facies. Changes in paleo-water depth reflect only local relative sea-Ievel change, which is influenced by the balance between changes in the rates at
which accommodation space forms and sediments fills
that space (Bond and Kominz 1991). These are the