462
considerable amounts of carbonate and accumulate at
a relatively slow rate (0.5 to 10 cmlka). Up to a certain point, preservation of organic matter and thus the
organic carbon accumulation rate in shales and marls
is furthered by an increasing sedimentation rate
(Sect. 10.5.3), but beyond this limit the effect of dilution prevails. The organic mattercontent also ~ends
to decrease with growing carbonate content (RIcken
1991).
10.2.6 Sedimentation Rates in so me
Specific Environments
The sedimentation rates in lakes displaya very wide
range (Fig. 10.3) depending largely on the size ofthe
lakes and the characteristics of their drainage areas.
Clastic sediments of small to middle-sized lakes often accumulate at rates of 100 to 1000 cmlka; carbonates at rates of 10 to 100 cm/ka.
Both lacustrine and marine evaporites, in particular highly soluble salts such as halite, can be precipitated at extremely high rates (for halite up to about
5000 cmlka). This occurs because the salt precipitating brines must have reached very high concentrations prior to salt crystallization. Then ongoing evaporation of water leads to rapid salt deposition. For
several reasons, however, such high rates cannot be
maintained for a long time (cf. Sect. 6.4).
Vertical growth of peat can be very fast under favorable conditions and surpass the common subsidence rates of most basin types (cf. Sect. 14.4.1).
Holocene peats in temperate and tropical regions
have accumulated at rates ranging from 20 to 200
cmlka (Cameron et al. 1989).- Sedimentation rates
reported in the literature for compacted Paleozoic to
Cenozoic coals (Stephanian basins in France, upper
Paleozoic to Mesozoic basins in China, Tertiary
Rhine basin in Germany, African rift valleys) mainly
vary between 0.3 and 30 cmlka (CoureI1989).
10.2.7 Sedimentation Rates, Denudation,
Subsidence, and Sea-Level Change
The sedimentation rates in the various depositional
environments discussed above represent relatively
wide ranges and may be used as a general guideline.
However, they do not include special cases which
deviate from these common values. In addition, the
fact that sedimentation rates may vary through time
within the same basin is not taken into account. During sea-Ievel highstands, terrigenous input into the
sea usually slows down, and carbonate production.
may significantly vary as a result of sea-Ievel
changes andother processes. Neglecting these complications, it is useful to compare common sedimenChapter 10 Sedimentation Rates and Organic Matter
tation rates with other rates relevant in geological
processes.
_
It is interesting to note that denudation rates on
land cover almost the same range (0.2 to more than
100 cmlka, cf. Sect. 9.5) as the sedimentation rates
discussed above (0.1 to 1000 cmlka; see also Kukal
1990). However, a direct comparison of sedimentation and denudation rates makes sense only for such
cases in which siliciclastic material predominates. In
addition, the drainage area of the basin should be
approximately equal to the area of the basin itself, or
the ratio between drainage area and basin area should
be known (cf. Sect. 11.2).
Furthermore, the subsidence rates in the various
types of sedimentary basins have a range (about 0.2
to more than 100 cmlka, Chap. 8) similar to that of
the sedimentation rates (cf. Fig. 3.29). This signifies
that, theoretically, any type of basin subsidence can
be compensated for by sediment accumulation, i.e.,
even the most rapidly subsiding basin may be kept
filled with sediments if an effective sediment source
is available. Acrually, all small basins, such as
graben strucrures, foreland basins,_ and pu!l-apart b~sins, can be filled, for example wlth fluvlal matenal,
although they may display very high subsidence rates
in their early evolutionary stage. However, when the
basins become larger and continue to subside substantially, such as in growing ocean basins, sediment
supply and sedimentation rates are normally no longer sufficient to keep the basins filled. These problems are discussed further in Section 11.3.
Finally, it is useful to know whether or not the sedimentation rates in specific environments could keep
pace with pre-Quaternary and Quaternary sea-level
rises. In the early Holocene, the short-term sea-Ievel
rise was so fast (6 to 10 mlka) that carbonate platforms were drowned, and many individual reefs were
not able to follow the rising water level (Schlager
1981). Pre-Quaternary, low-frequency s~a-Ievel
changes occurred at rates of about.l cmJka~ h~gh-frequency, low-amplitude oscillatlOns wlthm the
Milankovitch frequency band (Sects. 7.1 and 7.9)
may have caused maximum rates of sea-level change
of ab out 10 to 50 cmlka. Even in the latter cases, the
sedimentation rates of some environments, for exampIe tidal and subtidal carbonates, were sufficiently
high to keep pace with the sea-Ievel rise and to maintain approximately the same depositional system
through long time periods (Strasser 1991).
considerable amounts of carbonate and accumulate at
a relatively slow rate (0.5 to 10 cmlka). Up to a certain point, preservation of organic matter and thus the
organic carbon accumulation rate in shales and marls
is furthered by an increasing sedimentation rate
(Sect. 10.5.3), but beyond this limit the effect of dilution prevails. The organic mattercontent also ~ends
to decrease with growing carbonate content (RIcken
1991).
10.2.6 Sedimentation Rates in so me
Specific Environments
The sedimentation rates in lakes displaya very wide
range (Fig. 10.3) depending largely on the size ofthe
lakes and the characteristics of their drainage areas.
Clastic sediments of small to middle-sized lakes often accumulate at rates of 100 to 1000 cmlka; carbonates at rates of 10 to 100 cm/ka.
Both lacustrine and marine evaporites, in particular highly soluble salts such as halite, can be precipitated at extremely high rates (for halite up to about
5000 cmlka). This occurs because the salt precipitating brines must have reached very high concentrations prior to salt crystallization. Then ongoing evaporation of water leads to rapid salt deposition. For
several reasons, however, such high rates cannot be
maintained for a long time (cf. Sect. 6.4).
Vertical growth of peat can be very fast under favorable conditions and surpass the common subsidence rates of most basin types (cf. Sect. 14.4.1).
Holocene peats in temperate and tropical regions
have accumulated at rates ranging from 20 to 200
cmlka (Cameron et al. 1989).- Sedimentation rates
reported in the literature for compacted Paleozoic to
Cenozoic coals (Stephanian basins in France, upper
Paleozoic to Mesozoic basins in China, Tertiary
Rhine basin in Germany, African rift valleys) mainly
vary between 0.3 and 30 cmlka (CoureI1989).
10.2.7 Sedimentation Rates, Denudation,
Subsidence, and Sea-Level Change
The sedimentation rates in the various depositional
environments discussed above represent relatively
wide ranges and may be used as a general guideline.
However, they do not include special cases which
deviate from these common values. In addition, the
fact that sedimentation rates may vary through time
within the same basin is not taken into account. During sea-Ievel highstands, terrigenous input into the
sea usually slows down, and carbonate production.
may significantly vary as a result of sea-Ievel
changes andother processes. Neglecting these complications, it is useful to compare common sedimenChapter 10 Sedimentation Rates and Organic Matter
tation rates with other rates relevant in geological
processes.
_
It is interesting to note that denudation rates on
land cover almost the same range (0.2 to more than
100 cmlka, cf. Sect. 9.5) as the sedimentation rates
discussed above (0.1 to 1000 cmlka; see also Kukal
1990). However, a direct comparison of sedimentation and denudation rates makes sense only for such
cases in which siliciclastic material predominates. In
addition, the drainage area of the basin should be
approximately equal to the area of the basin itself, or
the ratio between drainage area and basin area should
be known (cf. Sect. 11.2).
Furthermore, the subsidence rates in the various
types of sedimentary basins have a range (about 0.2
to more than 100 cmlka, Chap. 8) similar to that of
the sedimentation rates (cf. Fig. 3.29). This signifies
that, theoretically, any type of basin subsidence can
be compensated for by sediment accumulation, i.e.,
even the most rapidly subsiding basin may be kept
filled with sediments if an effective sediment source
is available. Acrually, all small basins, such as
graben strucrures, foreland basins,_ and pu!l-apart b~sins, can be filled, for example wlth fluvlal matenal,
although they may display very high subsidence rates
in their early evolutionary stage. However, when the
basins become larger and continue to subside substantially, such as in growing ocean basins, sediment
supply and sedimentation rates are normally no longer sufficient to keep the basins filled. These problems are discussed further in Section 11.3.
Finally, it is useful to know whether or not the sedimentation rates in specific environments could keep
pace with pre-Quaternary and Quaternary sea-level
rises. In the early Holocene, the short-term sea-Ievel
rise was so fast (6 to 10 mlka) that carbonate platforms were drowned, and many individual reefs were
not able to follow the rising water level (Schlager
1981). Pre-Quaternary, low-frequency s~a-Ievel
changes occurred at rates of about.l cmJka~ h~gh-frequency, low-amplitude oscillatlOns wlthm the
Milankovitch frequency band (Sects. 7.1 and 7.9)
may have caused maximum rates of sea-level change
of ab out 10 to 50 cmlka. Even in the latter cases, the
sedimentation rates of some environments, for exampIe tidal and subtidal carbonates, were sufficiently
high to keep pace with the sea-Ievel rise and to maintain approximately the same depositional system
through long time periods (Strasser 1991).