2. An active hydrodynamics generating a centripetal displacement of oceanic water, which passes through the
reef mass.
3. The presence of an aquifer of a minimal size necessary
for the development of a significant dolomitic body.
This supposes a relatively important relief above sea
level or surface area of the emerged island (Aïssaoui,
1986).
Outlook: What we still do not know about reef
diagenesis
The diagenetic modification of a carbonate sediment
results from cumulative effects of numerous biological,
physical, and chemical processes acting independently
and successively in time or interacting concomitantly.
The diversity of processes involved and the way they
may interact with each other leave in our present understanding of carbonate diagenesis several, if not many,
important gaps and question marks, some of which are
listed and briefly discussed below, but the list is far from
being exhaustive.
Role of organic matter
The interactions between organic matter and carbonate
precipitation or dissolution have been invoked in numerous works on carbonate diagenesis, including reefs, since
the beginning of studies of diagenesis in carbonate platforms. In particular, the influence of organic compounds
is frequently considered as the potential cause of the
non-thermodynamic behavior of carbonates (Morse
et al., 2007).
The assessment of the complex and diverse interplays
between carbonate mineral and living, dissolved or amorphous organic material has made significant progress in
the past 2 decades, but is still in its infancy. Both in vitro
experimentation and in situ observation-based research
in natural environments are needed in order to improve
our understanding of such systems.
Three different categories of interactions, which are
potentially of tremendous importance for diagenesis, may
be distinguished: (1) the behavior of carbonates (and related
diagenetic processes) in the presence of dissolved organic
matter, (2) the relationships between organic compounds
and mineral surfaces via adsorption at preferential sites,
and (3) the presence of glycoproteinous material as
intraskeletal organic matrices within skeletal carbonates
and bioclasts.
Role of microbial processes in reef diagenesis
In recent years, research investigations on living coral
reefs have been focused on the qualitative and quantitative
assessment of microbial benthic communities, including
photosynthetic microphytobenthos. This notably revealed
that the contribution of these microbial associations to the
primary carbonate production of the entire reef ecosystem
may be in the same order of magnitude of the production
estimated for corals (Werner et al., 2008). The potential
role of these microbes on the processes of early diagenesis, especially marine cementation, has to be investigated
together with the general understanding of possible interactions between single microbes, biofilms, and mineral
surfaces in marine and nonmarine interstitial waters.
Inversely, the role that early diagenesis can play in the
preservation of these biofilms and traces of microbial
assemblages in recent and deep geological record appears
particularly complex and represents a still open field for
future research.
As far as reefs and carbonate platforms are concerned,
these two points have strong and direct links with the practical highly relevant questions of the origin and interpretation of peloids (their nature as cement, internal sediment,
or microbialite) and the general lack of discriminant
criteria for inferring the nature of micritic crusts in general.
Bibliography
Aïssaoui, D. M., 1985. Botryoidal aragonite and its diagenesis. Sedimentology, 32, 345–361.
Aïssaoui, D. M., 1986. Diagenèse carbonatée en domaine récifal.
Thesis Doctorat Es Sciences, Université Paris-Sud, Orsay.
Aïssaoui, D. M., 1988. Magnesian calcite cements and their diagenesis: dissolution and dolomitization, Mururoa Atoll. Sedimentology, 35, 821–841.
Aïssaoui, D. M., and Purser, B. H., 1983. Nature and origin of internal sediments in Jurassic limestones of Burgundy (France) and
Fnoud (Algeria). Sedimentology, 30, 273–283.
Aïssaoui, D. M., and Purser, B. H., 1985. Reef diagenesis: cementation at Mururoa Atoll (French Polynesia). In Proceedings of the
Fifth International Coral Reef Congress. Tahiti, Vol. 3,
pp. 257–262.
Aïssaoui, D. M., and Purser, B. H., 1986. La cimentation dans les
récifs: principe de cimentation maximale. CRAS Paris, 303(2),
301–303.
Aïssaoui, D. M., Buigues, D., and Purser, B. H., 1986. Model of reef
diagenesis: Mururoa atoll, French Polynesia. In Schroeder, J. H.,
and Purser B. H. (eds.), Reef Diagenesis. Berlin: Springer, pp.
27–52.
Badiozamani, K., 1973. The Dorag dolomitization model – application to the Middle Ordovician of Wisconsin. Journal of Sedimentary Petrology, 43, 965–984.
Badiozamani, K., Mackenzie, F. T., and Thorstenson, D. C., 1977.
Experimental carbonate cementation: salinity, temperature and
vadose-phreatic effects. Journal of Sedimentary Petrology, 47,
529–542.
Berbey, H., 1989. Sédimentologie et géochimie de la transition
substrat volcanique-couverture sédimentaire de l’Atoll de
Mururoa. PhD thesis, Université Paris-Sud, Orsay.
Bricker, O. P., 1973. Carbonate Cements. Baltimore, MD: John
Hopkins University Press, Vol. 19, 376 pp.
Buigues, D., 1982. Sédimentation et diagenèse des formations
carbonatées de l’atoll de Mururoa (Polynésie Française). Thesis 3e cycle, Université Paris-Sud, Orsay, 309 pp.
Buddemeier, R. W., and Oberdorfer, J. A., 1986. Internal hydrology
and geochemistry of coral reefs and atoll islands: key to diagenetic variations. In Schroeder, J. H., and Purser B. H. (eds.), Reef
Diagenesis. Berlin: Springer, pp. 91–111.
Cailleau, G., Verrecchia, E. P., Braissant, O., and Emmanuel, L.,
2009. The biogenic origin of needle fibre calcite. Sedimentology,
56, 1858–1875.
Carrière, D., 1987. Sédimentation, diagenèse et cadre
géodynamique de l’atoll soulevé de Maré, Nouvelle Calédonie.
PhD Thesis, Université Paris-Sud, Orsay, 369 pp.
DIAGENESIS
319
reef mass.
3. The presence of an aquifer of a minimal size necessary
for the development of a significant dolomitic body.
This supposes a relatively important relief above sea
level or surface area of the emerged island (Aïssaoui,
1986).
Outlook: What we still do not know about reef
diagenesis
The diagenetic modification of a carbonate sediment
results from cumulative effects of numerous biological,
physical, and chemical processes acting independently
and successively in time or interacting concomitantly.
The diversity of processes involved and the way they
may interact with each other leave in our present understanding of carbonate diagenesis several, if not many,
important gaps and question marks, some of which are
listed and briefly discussed below, but the list is far from
being exhaustive.
Role of organic matter
The interactions between organic matter and carbonate
precipitation or dissolution have been invoked in numerous works on carbonate diagenesis, including reefs, since
the beginning of studies of diagenesis in carbonate platforms. In particular, the influence of organic compounds
is frequently considered as the potential cause of the
non-thermodynamic behavior of carbonates (Morse
et al., 2007).
The assessment of the complex and diverse interplays
between carbonate mineral and living, dissolved or amorphous organic material has made significant progress in
the past 2 decades, but is still in its infancy. Both in vitro
experimentation and in situ observation-based research
in natural environments are needed in order to improve
our understanding of such systems.
Three different categories of interactions, which are
potentially of tremendous importance for diagenesis, may
be distinguished: (1) the behavior of carbonates (and related
diagenetic processes) in the presence of dissolved organic
matter, (2) the relationships between organic compounds
and mineral surfaces via adsorption at preferential sites,
and (3) the presence of glycoproteinous material as
intraskeletal organic matrices within skeletal carbonates
and bioclasts.
Role of microbial processes in reef diagenesis
In recent years, research investigations on living coral
reefs have been focused on the qualitative and quantitative
assessment of microbial benthic communities, including
photosynthetic microphytobenthos. This notably revealed
that the contribution of these microbial associations to the
primary carbonate production of the entire reef ecosystem
may be in the same order of magnitude of the production
estimated for corals (Werner et al., 2008). The potential
role of these microbes on the processes of early diagenesis, especially marine cementation, has to be investigated
together with the general understanding of possible interactions between single microbes, biofilms, and mineral
surfaces in marine and nonmarine interstitial waters.
Inversely, the role that early diagenesis can play in the
preservation of these biofilms and traces of microbial
assemblages in recent and deep geological record appears
particularly complex and represents a still open field for
future research.
As far as reefs and carbonate platforms are concerned,
these two points have strong and direct links with the practical highly relevant questions of the origin and interpretation of peloids (their nature as cement, internal sediment,
or microbialite) and the general lack of discriminant
criteria for inferring the nature of micritic crusts in general.
Bibliography
Aïssaoui, D. M., 1985. Botryoidal aragonite and its diagenesis. Sedimentology, 32, 345–361.
Aïssaoui, D. M., 1986. Diagenèse carbonatée en domaine récifal.
Thesis Doctorat Es Sciences, Université Paris-Sud, Orsay.
Aïssaoui, D. M., 1988. Magnesian calcite cements and their diagenesis: dissolution and dolomitization, Mururoa Atoll. Sedimentology, 35, 821–841.
Aïssaoui, D. M., and Purser, B. H., 1983. Nature and origin of internal sediments in Jurassic limestones of Burgundy (France) and
Fnoud (Algeria). Sedimentology, 30, 273–283.
Aïssaoui, D. M., and Purser, B. H., 1985. Reef diagenesis: cementation at Mururoa Atoll (French Polynesia). In Proceedings of the
Fifth International Coral Reef Congress. Tahiti, Vol. 3,
pp. 257–262.
Aïssaoui, D. M., and Purser, B. H., 1986. La cimentation dans les
récifs: principe de cimentation maximale. CRAS Paris, 303(2),
301–303.
Aïssaoui, D. M., Buigues, D., and Purser, B. H., 1986. Model of reef
diagenesis: Mururoa atoll, French Polynesia. In Schroeder, J. H.,
and Purser B. H. (eds.), Reef Diagenesis. Berlin: Springer, pp.
27–52.
Badiozamani, K., 1973. The Dorag dolomitization model – application to the Middle Ordovician of Wisconsin. Journal of Sedimentary Petrology, 43, 965–984.
Badiozamani, K., Mackenzie, F. T., and Thorstenson, D. C., 1977.
Experimental carbonate cementation: salinity, temperature and
vadose-phreatic effects. Journal of Sedimentary Petrology, 47,
529–542.
Berbey, H., 1989. Sédimentologie et géochimie de la transition
substrat volcanique-couverture sédimentaire de l’Atoll de
Mururoa. PhD thesis, Université Paris-Sud, Orsay.
Bricker, O. P., 1973. Carbonate Cements. Baltimore, MD: John
Hopkins University Press, Vol. 19, 376 pp.
Buigues, D., 1982. Sédimentation et diagenèse des formations
carbonatées de l’atoll de Mururoa (Polynésie Française). Thesis 3e cycle, Université Paris-Sud, Orsay, 309 pp.
Buddemeier, R. W., and Oberdorfer, J. A., 1986. Internal hydrology
and geochemistry of coral reefs and atoll islands: key to diagenetic variations. In Schroeder, J. H., and Purser B. H. (eds.), Reef
Diagenesis. Berlin: Springer, pp. 91–111.
Cailleau, G., Verrecchia, E. P., Braissant, O., and Emmanuel, L.,
2009. The biogenic origin of needle fibre calcite. Sedimentology,
56, 1858–1875.
Carrière, D., 1987. Sédimentation, diagenèse et cadre
géodynamique de l’atoll soulevé de Maré, Nouvelle Calédonie.
PhD Thesis, Université Paris-Sud, Orsay, 369 pp.
DIAGENESIS
319