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darellacean algae). Fig. 10.4 exhibits the temporal dis-
tribution of major groups of calcareous algae. Further
smaller groups are dealt within the discussion of red
and green algae.
deeper subtidal, slope and basinal environments as well
as the growth of various red and some green algae at
water depths of several tens and even a few hundred
meters is also responsible for the possible occurrence
of algal material in deep-marine settings. Storms can
transport algal debris from open-marine platforms to
near-coastal environments. Even a transport of marine
algae to nonmarine settings by storms is likely (Pl. 131/4).
Significance of algae in microfacies analysis
Fossil calcified algae are most important in micro-
facies analysis, because of their high potential in re-
constructing paleoenvironments and ecological condi-
tions, their biostratigraphic potential, and their large
contribution to the formation of carbonate sediments.
To avoid some of these pitfalls, the use of distribu-
tion patterns is recommended. This approach relates
the composition of algal associations to other microfa-
cies data (limestone textures and structures, additional
fossils). The algal associations are characterized with
regard to their taxonomic composition, frequency and
dominance of specific taxa or groups, and diversities.
The distribution patterns of algal associations can not
be directly compared with the ecological zonation of
living algae, because many ancient taxa are extinct and
their relationship to living forms may be unknown.
Nevertheless, established empirical distribution patterns
have a high potential for reconstructing paleoecologi-
cal factors, e.g. paleoclimate and paleoceanography and
paleoenvironments.
Stratigraphic zonation: Calcareous algae are valu-
able in subdividing rock units and establishing zona-
tions. These zonations are based on the occurrence of
characteristic associations of species, or the range of
single species, or the abundance and climax of species.
Commonly used marine algal groups are dasyclad green
algae, some red algae, and charophycean algae in non-
marine sediments.
Paleoenvironment: Fossil calcified algae are used
in reconstructing environmental factors such as water
temperature (see Pl. 105), salinity and relative water
depths (see Pl. 108). This approach has to consider sev-
eral points:
(a) Modern calcareous green and red algae exhibit
different ecological controls with regard to water depths.
Some algal groups occupy wide bathymetric ranges:
Coralline red algae and udoteacean green algae are not
restricted to 'shallow' depths but also thrive at water
depths of several tens of meters, corallinaceans even in
depths of more than two hundred meters. Paleobathy-
metric interpretations should be based on specific al-
gal groups rather than on the generalized statement of
the occurrence of 'algae'.
(b) A few algal groups exhibit differences in pre-
ferred modern and ancient biotopes. Ancient calci-
microbes are common fossils in marine limestones,
whereas modern calcified cyanobacteria flourish in
waters with nonmarine salinities. Modern dasyclads
prefer lagoonal and shelf habitats in contrast to ancient
forms common in lagoonal and shelf carbonates, but
also occur in reef limestones. The major factors con-
trolling the distribution of algae may be modified by
local factors, e.g. substrate conditions (Flügel 1983).
(c) Not all modern calcified algae are highly light-
dependent. Green algae and red algae exist in shadowy
habitats. Ancient calcimicrobes are common constitu-
ents of cryptic biotopes.
(d) Mean annual water temperature has a strong con-
trol on the distribution of calcareous algae, but for mod-
ern corallinacean red algae this factor is distinctly taxa-
dependent.
(e) Algal bioclasts are easily transported and rede-
posited. They may not represent autochthonous con-
stituents of the sediment, but rather grains transported
into other carbonate settings. Downslope and turbidity
current transport of green algal debris from modern car-
bonate platforms to deep water environments is a com-
mon feature. Transport of shallow-marine algae to
Sedimentation: Calcareous algae are major produc-
ers of carbonate sediments in shallow marine environ-
ments as well as in deep-water settings. Modern sedi-
ment-producing algal groups in shallow platform and
inner ramp environments comprise predominantly udo-
teacean green algae (e.g. Halimeda ; see Sect. 4.1.2) and
corallinacean and squamariacean red algae. The con-
tribution of dasyclad algal skeletal grains to recent sedi-
ment production is minor as compared with ancient car-
bonate platforms, particularly of Late Paleozoic and
Mesozoic age. Udoteacean green algae were important
producers of carbonate mud and sand at least since the
Late Triassic, but probably already in the Paleozoic.
Common Late Paleozoic sediment producers were an-
cestral red algae forming rhodoids, and phylloid algae
contributing to the accumulation of sediment in reef
mounds.
The deposition of calcitic planktonic algae (cocco-
lithophorid chrysophyceans, calciodinoflagellate dino-
phyceans, and other related groups) in pelagic deep-
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