3 Coastal and Shallow Sea Sediments
3.4 Carbonate Buildups and
Reef-Lagoon Complexes
3.4.1 Introduction
3.4.2 Carbonate-Producing Communities
Modem Carbonates
Ancient Carbonate-Producing Communities
3.4.3 Carbonate Mineralogy and Non-Skeletal Grains
3.4.4 Carbonate Ramps
3.4.5 ReefTypes and Composite Carbonate Buildups
General Aspects
ReefTypes
Composite Carbonate Buildups
The Back -Reef Zone and Reef Lagoons
"Pelagic" Carbonate Platforms
Types ofReefLimestones
3.4.6 Response ofCarbonate Buildups to Subsidence
and Sea-Level Rise
Vertical Buildup and "Drowning"
Pro- and Retrograding Carbonate Buildups
3.4.7 Diagenesis ofReefs and Carbonate Buildups
General Processes of Carbonate Diagenesis
Cement Sequences
Dolomitization
Economic Aspects of Carbonate Diagenesis
3.4.8 Summary (Shallow-Marine Carbonates)
3.4.1 Introduction
Carbonate-rich sediments generally accumulate under
two principal conditions:
Relatively high production and preservation of
carbonate, and
- Low input of siliciclastic material to the site of
ultimate deposition.
This rule is valid for both shallow and deep seas (cf.
Chap. 10), but in this chapter shallow-water carbonates only are considered. The first prerequisite for the
formation of carbonate-rich sediments is met not only
in tropical to subtropical seas, as was widely thought
one or two decades ago, but also in cooler waters
(see below). The second prerequisite is necessary to
prevent too strong dilution of the carbonate produced
in place or exported to deeper water. Otherwise the
proportion of carbonate in the sediment or later rock
is strongly reduced resulting in mixed siliciclasticcarbonate sediments, such as marls, marly silts and
clays. Pure carbonates or carbonate-rich sediments
cannot form in front of large river mouths and coasts
with high influx or longshore transport of siliciclastic
material. F or this reason, the shelves of tropical
wetlands usually do not accumulate carbonates (Fig.
3.23). In this climatic zone, deposition of more or
less pure carbonates is restricted to isolated platforms
or islands.
Most of the carbonate present in young marine
sediments and Phanerozoic rocks has been produced
by organisms (skeletal or biogenic carbonate) in shallow waters. The penetration of sun light into surface
water enables plant life with photosynthesis (photic
biota or photozoan association; James 1997), and this
in turn feeds planktic and benthic faunal associations
(aphotic biota or heterozoan association; cf. Sect.
10.3.2). In shallow seas benthic organisms living on
the sea floor are the most important producers of
skeletal carbonate. Recent studies have shown that
biogenic shallow-water carbonates form at all latitudes in considerable quantities (Fig. 3.23). In the
modem oceans we can distinguish between
Tropical and subtropical carbonates (in latitudes
of 0 to about 30° N or S, >25°C),
Temperate carbonates (about 30 to 50 0 N or S, 25
to 10°C),
Polar and subpolar carbonates (>50 0 N or S,
<10°C).
There are transitions between these groups; the temperate and cold-water carbonates are often described
as one category (non-tropical carbonates) in contrast
to the warm-water carbonates (see below). These
contrasting groups are characterized by different
types of fauna, flora as well as size, shape, and mineralogy of their particles which to some degree also
control their preservation and diagenesis.
The carbonate-producing communities changed
through geological time with the evolution of life.
New communities responded differently to similar
changes in environmental factors. Nevertheless we
assume that carbonate production was always controlled,' to some extent, by water temperature (i.e.
latitude).
Many other aspects of carbonate production, ree~ building,
and carbonate diagenesis during the Earth's history are
3.4 Carbonate Buildups and
Reef-Lagoon Complexes
3.4.1 Introduction
3.4.2 Carbonate-Producing Communities
Modem Carbonates
Ancient Carbonate-Producing Communities
3.4.3 Carbonate Mineralogy and Non-Skeletal Grains
3.4.4 Carbonate Ramps
3.4.5 ReefTypes and Composite Carbonate Buildups
General Aspects
ReefTypes
Composite Carbonate Buildups
The Back -Reef Zone and Reef Lagoons
"Pelagic" Carbonate Platforms
Types ofReefLimestones
3.4.6 Response ofCarbonate Buildups to Subsidence
and Sea-Level Rise
Vertical Buildup and "Drowning"
Pro- and Retrograding Carbonate Buildups
3.4.7 Diagenesis ofReefs and Carbonate Buildups
General Processes of Carbonate Diagenesis
Cement Sequences
Dolomitization
Economic Aspects of Carbonate Diagenesis
3.4.8 Summary (Shallow-Marine Carbonates)
3.4.1 Introduction
Carbonate-rich sediments generally accumulate under
two principal conditions:
Relatively high production and preservation of
carbonate, and
- Low input of siliciclastic material to the site of
ultimate deposition.
This rule is valid for both shallow and deep seas (cf.
Chap. 10), but in this chapter shallow-water carbonates only are considered. The first prerequisite for the
formation of carbonate-rich sediments is met not only
in tropical to subtropical seas, as was widely thought
one or two decades ago, but also in cooler waters
(see below). The second prerequisite is necessary to
prevent too strong dilution of the carbonate produced
in place or exported to deeper water. Otherwise the
proportion of carbonate in the sediment or later rock
is strongly reduced resulting in mixed siliciclasticcarbonate sediments, such as marls, marly silts and
clays. Pure carbonates or carbonate-rich sediments
cannot form in front of large river mouths and coasts
with high influx or longshore transport of siliciclastic
material. F or this reason, the shelves of tropical
wetlands usually do not accumulate carbonates (Fig.
3.23). In this climatic zone, deposition of more or
less pure carbonates is restricted to isolated platforms
or islands.
Most of the carbonate present in young marine
sediments and Phanerozoic rocks has been produced
by organisms (skeletal or biogenic carbonate) in shallow waters. The penetration of sun light into surface
water enables plant life with photosynthesis (photic
biota or photozoan association; James 1997), and this
in turn feeds planktic and benthic faunal associations
(aphotic biota or heterozoan association; cf. Sect.
10.3.2). In shallow seas benthic organisms living on
the sea floor are the most important producers of
skeletal carbonate. Recent studies have shown that
biogenic shallow-water carbonates form at all latitudes in considerable quantities (Fig. 3.23). In the
modem oceans we can distinguish between
Tropical and subtropical carbonates (in latitudes
of 0 to about 30° N or S, >25°C),
Temperate carbonates (about 30 to 50 0 N or S, 25
to 10°C),
Polar and subpolar carbonates (>50 0 N or S,
<10°C).
There are transitions between these groups; the temperate and cold-water carbonates are often described
as one category (non-tropical carbonates) in contrast
to the warm-water carbonates (see below). These
contrasting groups are characterized by different
types of fauna, flora as well as size, shape, and mineralogy of their particles which to some degree also
control their preservation and diagenesis.
The carbonate-producing communities changed
through geological time with the evolution of life.
New communities responded differently to similar
changes in environmental factors. Nevertheless we
assume that carbonate production was always controlled,' to some extent, by water temperature (i.e.
latitude).
Many other aspects of carbonate production, ree~ building,
and carbonate diagenesis during the Earth's history are