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have become increasingly more important (Johansen
1981; Woelkerling 1988; Bosence 1991).
Reproductive organs are borne in calcified case-like
chambers (conceptacles). Conceptacles may be uni-
porate (Pl. 54/4), multiporate (Pl. 54/1), or arranged in
rows (sori; Pl. 54/7). The type, the kind of conceptacle
roof formation, and the location of conceptacles are dia-
gnostic criteria.
Coralline bioclasts
contribute significantly to the for-
mation of marine warm-water, temperate-water, cold-
water and even polar sand- and gravel-sized carbonates
(Pl. 33/2, Pl. 35/1).
Reef frameworks
are constructed from crustose or
branching coralline algae both in high- and low-energy
environments, but differ in the density of the crusts and
branches. Frameworks cemented by fibrous aragonite
and microcrystalline High-Mg calcite occur in high-
energy coralline algal ridges. Low-energy frameworks
are characterized by intraskeletal cements precipitated
only during the life of the algae. Bioerosion by micro-
and macroborers is strong in high-energy reefs and less
common in low-energy reefs. Sediments derived from
high-energy reefs comprise coarse particles from break-
age by waves and fine particles caused by borers. Quiet-
water frameworks are broken by wave action and bio-
turbation; wackestones and packstones are deposited
around the reefs (Bosence 1985).
Environmental constraints:
Modern corallines range
from tropical to polar oceans and extend from inter-
tidal areas to depths of about 250 m. Tropical taxa oc-
cur in depths down to about 80 m, cold-water taxa be-
tween about 20 and 250 m (Pl. 4/1). The distribution of
corallines is controlled by environmental factors, pre-
dation (grazing) and competition. Competitive inter-
action among crustose corallines is influenced by the
thickness of the crusts and the height to which the grow-
ing margin is raised (Steneck et al. 1991). Most coral-
lines prefer hard rough substrates, dim light conditions
and agitated water. They occur in warm and cold wa-
ters from low to high latitudes and are commonly
adapted to normal marine salinities. Growth rates de-
pend mainly on light conditions. Many corallines are
shade-adapted.
Significance of corallinacean algae:
Most Tertiary
genera occur even today. Because of these long-term
ranges, the study of present-day coralline algae offers
an
excellent potential for paleoenvironmental interpre-
tations
. Of particular value are thallus shape and ge-
neric associations. The morphology of coralline crusts
and branches reflect different water energies (Bosence
1983). Rhodoids are sensitive to turbulence in shallow-
marine environments (Bosence and Pedley 1982; Sect.
4.2.4.2). Because modern crustose coralline genera have
existed from the Miocene onward, the
paleobathymetry
can be successfully evaluated at least for the Neogene
(Basso 1998).
Distribution:
The definite record of abundant coral-
lines begins near the start of the Cretaceous, perhaps
already in the latest Jurassic. The recognition of Or-
dovician and Silurian fossils with coralline-like features
extends the earliest record to the Early Paleozoic (Brooke
and Riding 1998; Riding et al. 1998).
Sediment production:
Coralline algae are one of the
most abundant marine carbonate producers. Unattached
corallines live on hard and soft sea bottoms and can
form
rhodoids
(Sect. 4.2.4.2; Pl. 12/6, Pl. 149/6) that
contribute to
rhodolith pavements
and
maerl
(composed
of branched rhodoids and coralline branches; Pl. 4/2;
Sect. 2.4.4.3). Attached corallines form
algal ridges
(late successional stage of coral reef development form-
ing a constructional cap over corals as the reef ap-
proaches sea level) and
algal cup reefs
(intertidal cup-
shaped reefs formed by intergrowing coralline algae
and invertebrates),
trottoirs
(intertidal buildups, usu-
ally growing on steep rock shores, e.g. Mediterranean
and the Northern Atlantic) and the
coralligène de pla-
teau
(occurring in deeper shelf waters of about 20 to
160 m, and passing laterally into carbonate sands and
gravels or terrigenous sands). Crustose corallines are
important Cenozoic
reef builders
in tropical and sub-
tropical regions, as framebuilders and binders, and as
cementing agents for bio- and lithoclasts (Pl. 149/2).
Basics: Corallinacean red algae
Adey, W.H., MacIntyre, I.G. (1973): Crustose coralline al-
gae: a re-evaluation in the geological sciences. - Bull.
Geol. Soc. Amer.,
84
, 883-904
Basso, D. (1998): Deep rhodolith distribution in the Pontian
Islands, Italy: a model for the paleoecology of a temperate
sea. - Palaeogeogr., Palaeoclimat., Palaeoecol.,
137
, 173-
187
Bosence, D.W. (1983): Coralline algal reef frameworks. - J.
Geol. Soc. London,
140
, 365-376
Bosence, D.W. (1991): Coralline algae: mineralization, tax-
onomy, and palaeoecology. - In: Riding, R. (ed.): Calcar-
eous algae and stromatolites. - 98-113, Berlin (Springer)
Bosence, D.W., Pedley, H.M. (1982): Sedimentology and
palaeoecology of a Miocene coralline algal biostrome from
the Maltese Island. - Palaeogeogr., Palaeoclimat., Palaeo-
ecol.,
39
, 9-43
Braga, J.C., Bosence, D.W., Steneck, T.S. (1993): New ana-
tomical characters in fossil coralline algae and their taxo-
nomic implications. - Palaeontology,
36
, 535-547
Johansen, H.W. (1981): Coralline algae, a first synthesis. -
239 pp., Boca Raton, Florida (CRC)
