Guilcher, A., 1988. Coral reef geomorphology. New York: Wiley.
Hopley, D., Smithers, S. G., and Parnell, K. E., 2007. The geomorphology of the Great Barrier Reef: Development, diversity, and
change. Cambridge: Cambridge University Press.
James, N. P., and Ginsburg, R. N., 1979. The seaward margin of
Belize barrier and atoll reefs. Morphology, sedimentology,
organism distribution and late Quaternary history. Special publ.
n
3 of the international Association of Sedimentologists.
Oxford: Blackwell.
Land, L. S., and Moore, C. H., 1977. Deep forereef and upper island
slope, north Jamaica. In Frost, S. H., Weiss, M. P., Saunders, J. B.
(eds.), Reefs and related carbonates – ecology and sedimentology. American Association of Petroleum Geologists, Studies in
Geology No. 4, pp. 53–65.
Land, L. S., and Moore, C. H., 1980. Lithification, micritization and
syndepositional diagenesis of biolithites of the Jamaïca island
slope. Journal of sedimentary Petrology, 50, 357–369.
Montaggioni, L. F., Gabrié, C., Naim, O., Payri, C., Richard, G., and
Salvat, B., 1987. The seaward margin of Makatea, an uplifted
carbonate island (Tuamotus, Central Pacific). Atoll Research
Bulletin, 299, 1–18.
Salvat, B., Sibuet, M., and Laubier, L., 1985. Benthic megafauna
observed from the submersible “Cyana” on the fore-reef slope
of Tahiti (French Polynesia) between 70 and 100 m. In Proceedings of the Fifth International Coral Reef Congress, Tahiti, 2,
pp. 338.
Cross-references
Antecedent Platforms
Barrier Reef (Ribbon Reef )
Double and Triple Reef Fronts
Geomorphic Zonation
Glacial Control Hypothesis
Reef Front Wave Energy
Reef Structure
Sea Level Change and Its Effect on Reef Growth
Spurs and Grooves
Submarine Lithification
Submerged Reefs
Subsidence Hypothesis of Reef Development
FOSSIL CORALLINE ALGAE
Juan C. Braga
Universidad de Granada, Granada, Spain
Definition
Fossil coralline algae are the remains in the geological
record of a group of calcified marine red algae
(Corallinales, Rhodophyta), which are common components in coral reef environments and can be significant
framework builders.
Introduction
Coralline algae are the major extant group of calcareous
red algae. As a group, they are cosmopolitan and have wide
ecological tolerances. They are common on seafloors with
low terrigenous supply at depths of up to 100–120 m in all
climatic belts. Individual species and genera, however,
have restricted dispersal areas and sensitivity to light conditions, trophic levels, wave energy, salinity, and other ecological factors, all of which limit their geographic and
environmental ranges.
The body (thallus) of corallines consists of filaments of
cells joined together to form a coherent mass. Most extant
coralline algae are pervasively calcified by high magnesian calcite precipitated in the cell walls. In crustose
coralline algae (CCA), also known as non-geniculate corallines, all vegetative cells except those at the thallus
surface are calcified. Consequently, the entire plant is
rigid, with varying degrees of fragility, and a high preservation potential as fossils (Bosence, 1991).
In contrast, in geniculate (articulated) corallines, calcified segments of the thallus are separated by noncalcified
joints (genicula). Articulated corallines have bushy thalli
formed by branches for which the joints offer flexibility.
After death, articulated corallines disintegrate and calcified segments are shed as sand and gravel particles.
CCA are common components in coral reef environments and can be major framework builders in algal ridges
(Adey, 1986). Accordingly, CCA are significant components in fossil coral reefs (Figure 1). Like their living
counterparts, fossil CCA can occur attached to hard
substrates, typically coral skeletons, cemented reef rock,
shells, and other calcified algae. CCA can also be unattached, occurring as nodules generally termed rhodoliths
or as loose branching growths within gravel or sand
deposits. Fragments of CCA and calcified segments of
geniculate corallines are abundant in reef debris and carbonate packstones and grainstones associated with
fossil reefs.
Diagnostic features for delimiting families and subfamilies and many diagnostic characters used to separate genera and species can be recognized in fossil plants in
ultrathin sections (less than 20 microns) with an optical
microscope (Figure 2) and scanning electron microscope
(SEM) after light etching (Braga et al., 1993). In some
cases, however, the diagnostic characters to distinguish
genera and species in living corallines correspond to
uncalcified reproductive structures that are not preserved
or are difficult to discern in fossil corallines. Fossil plants
of the majority of the main CCA species of modern
reefs usually preserve characters that permit their identification. In a few cases, the preserved anatomic features
only warrant the identification of a species group
within a genus. A species group is a set of species that
share a series of characters separating them from other
species of the genus. Plants with very thin laminar thalli
(less than 0.02 mm in thickness) are commonly micronized and usually cannot be identified. Therefore, they are
not taken into account in palaeoenvironmental interpretations based on fossil CCA.
Applications of fossil CCA
The habitat preferences of different genera and species,
the variations in morphology according to turbulence
FOSSIL CORALLINE ALGAE
423
Hopley, D., Smithers, S. G., and Parnell, K. E., 2007. The geomorphology of the Great Barrier Reef: Development, diversity, and
change. Cambridge: Cambridge University Press.
James, N. P., and Ginsburg, R. N., 1979. The seaward margin of
Belize barrier and atoll reefs. Morphology, sedimentology,
organism distribution and late Quaternary history. Special publ.
n
3 of the international Association of Sedimentologists.
Oxford: Blackwell.
Land, L. S., and Moore, C. H., 1977. Deep forereef and upper island
slope, north Jamaica. In Frost, S. H., Weiss, M. P., Saunders, J. B.
(eds.), Reefs and related carbonates – ecology and sedimentology. American Association of Petroleum Geologists, Studies in
Geology No. 4, pp. 53–65.
Land, L. S., and Moore, C. H., 1980. Lithification, micritization and
syndepositional diagenesis of biolithites of the Jamaïca island
slope. Journal of sedimentary Petrology, 50, 357–369.
Montaggioni, L. F., Gabrié, C., Naim, O., Payri, C., Richard, G., and
Salvat, B., 1987. The seaward margin of Makatea, an uplifted
carbonate island (Tuamotus, Central Pacific). Atoll Research
Bulletin, 299, 1–18.
Salvat, B., Sibuet, M., and Laubier, L., 1985. Benthic megafauna
observed from the submersible “Cyana” on the fore-reef slope
of Tahiti (French Polynesia) between 70 and 100 m. In Proceedings of the Fifth International Coral Reef Congress, Tahiti, 2,
pp. 338.
Cross-references
Antecedent Platforms
Barrier Reef (Ribbon Reef )
Double and Triple Reef Fronts
Geomorphic Zonation
Glacial Control Hypothesis
Reef Front Wave Energy
Reef Structure
Sea Level Change and Its Effect on Reef Growth
Spurs and Grooves
Submarine Lithification
Submerged Reefs
Subsidence Hypothesis of Reef Development
FOSSIL CORALLINE ALGAE
Juan C. Braga
Universidad de Granada, Granada, Spain
Definition
Fossil coralline algae are the remains in the geological
record of a group of calcified marine red algae
(Corallinales, Rhodophyta), which are common components in coral reef environments and can be significant
framework builders.
Introduction
Coralline algae are the major extant group of calcareous
red algae. As a group, they are cosmopolitan and have wide
ecological tolerances. They are common on seafloors with
low terrigenous supply at depths of up to 100–120 m in all
climatic belts. Individual species and genera, however,
have restricted dispersal areas and sensitivity to light conditions, trophic levels, wave energy, salinity, and other ecological factors, all of which limit their geographic and
environmental ranges.
The body (thallus) of corallines consists of filaments of
cells joined together to form a coherent mass. Most extant
coralline algae are pervasively calcified by high magnesian calcite precipitated in the cell walls. In crustose
coralline algae (CCA), also known as non-geniculate corallines, all vegetative cells except those at the thallus
surface are calcified. Consequently, the entire plant is
rigid, with varying degrees of fragility, and a high preservation potential as fossils (Bosence, 1991).
In contrast, in geniculate (articulated) corallines, calcified segments of the thallus are separated by noncalcified
joints (genicula). Articulated corallines have bushy thalli
formed by branches for which the joints offer flexibility.
After death, articulated corallines disintegrate and calcified segments are shed as sand and gravel particles.
CCA are common components in coral reef environments and can be major framework builders in algal ridges
(Adey, 1986). Accordingly, CCA are significant components in fossil coral reefs (Figure 1). Like their living
counterparts, fossil CCA can occur attached to hard
substrates, typically coral skeletons, cemented reef rock,
shells, and other calcified algae. CCA can also be unattached, occurring as nodules generally termed rhodoliths
or as loose branching growths within gravel or sand
deposits. Fragments of CCA and calcified segments of
geniculate corallines are abundant in reef debris and carbonate packstones and grainstones associated with
fossil reefs.
Diagnostic features for delimiting families and subfamilies and many diagnostic characters used to separate genera and species can be recognized in fossil plants in
ultrathin sections (less than 20 microns) with an optical
microscope (Figure 2) and scanning electron microscope
(SEM) after light etching (Braga et al., 1993). In some
cases, however, the diagnostic characters to distinguish
genera and species in living corallines correspond to
uncalcified reproductive structures that are not preserved
or are difficult to discern in fossil corallines. Fossil plants
of the majority of the main CCA species of modern
reefs usually preserve characters that permit their identification. In a few cases, the preserved anatomic features
only warrant the identification of a species group
within a genus. A species group is a set of species that
share a series of characters separating them from other
species of the genus. Plants with very thin laminar thalli
(less than 0.02 mm in thickness) are commonly micronized and usually cannot be identified. Therefore, they are
not taken into account in palaeoenvironmental interpretations based on fossil CCA.
Applications of fossil CCA
The habitat preferences of different genera and species,
the variations in morphology according to turbulence
FOSSIL CORALLINE ALGAE
423