previous classifications obtained from the interpretation of
aerial photography, but he accounted for new data from
coring and from recent advances in understanding reef
growth. He showed that previous interpretations could
be misleading to infer a reef-growth development typology. Then, Hopley (1982) established a new classification
for the shelf reef of the Great Barrier Reef, including as
a specific zone the northern Ribbon Reefs, which display
a typical barrier morphology, with linear reefs parallel to
the continent, from 15
S up to 10
S in the Torres Strait.
South of Cooktown, the Great Barrier Reef consists of
a dense (e.g., the Swains group) to open matrix (e.g., the
Capricorn Bunker group) of shelf patch reefs, also called
platform reefs. The size of these patch reefs displays
a wide range, from a few hundreds of square meters to several tens of square kilometers. The unique and photogenic
Pompey Group, at 21
S displays a general barrier linear
morphology, with very large individual reefs characterized by subsurface karstic formations, blue holes, and
numerous deep and narrow channels.
Recently, remote sensing technology provided complete coverage of reefs worldwide using high spatial resolution Landsat satellite images (Andréfouët et al., 2006a).
This new data set allows examining in details all barrier
reefs worldwide. A detailed typology was inferred,
although it cannot be precisely coupled in most locations
with coring data to relate planar morphology with genetic
processes like in Hopley (1982). Thus far, this link has
been done only for New Caledonia (Andréfouët et al.,
2009a). Nevertheless, the diversity of morphologies are
potential indicators of local processes keeping in mind
the same caveats that Hopley (1982) put forth for the interpretation of Great Barrier Reef structures.
Landsat images suggested a hierarchical typology that
can be applied to oceanic and continental reefs. In this
typology, atolls are described separately, and thus atoll
rims are not considered like barrier reefs. First, two main
types of barrier reefs are distinguished on the top of the
hierarchy: the outer shelf and intra-shelf barrier. The
intra-shelf barrier is composed of continuous lines of reefs
in a lagoon, well separated from the outer shelf barrier.
Then, these two types of barrier reefs can themselves be
separated into barrier, multiple-barrier, faro-barrier, imbricated-barrier, coastal-barrier, and fringing-barrier types.
Multiple-barriers are made of series of parallel reef flats
developed close to each other and sometimes connected
together (see Guilcher, 1988). A faro-barrier is a structure
made of faros, or in other words a series of reefs with
a central enclosed lagoon. An imbricated-barrier is a section of barrier, which is turning around itself, the outer side
turning to the inner side when bending, thus changing
completely the degree of exposure and the types of
habitats. An imbricated-barrier can also be a barrier that
terminates in the lagoon of a second separate barrier.
A coastal-barrier is an intermediate configuration between
a barrier and a fringing reef, that is, there is no deep
lagoon, but a shallow sedimentary terrace that clearly separates outer reef flat habitats from fringing-like habitats.
A fringing-barrier is a section of barrier that harbors large
islands, thus displaying fringing-type habitats in an outer
barrier environment. Examples of all these barrier reef
types are given in Figure 1. These types describe the diversity of barrier reefs worldwide based on their morphology
visible on remote-sensing images.
Locations
Beside the Australian Great Barrier Reef discussed above,
barrier reefs are found in all coral reef provinces worldwide. In the Caribbean Seas and Atlantic Ocean, the longest system is offshore Belize, approximately 200 km
long (Figure 1). This Belizean section is actually the only
true outer barrier system of the so-called Meso-American
Barrier Reef System (Mexican Yucatan, Belize, Guatemala
and Honduras), which includes fringing reefs for most of its
length. Honduras Bay Islands include a drowned barrier
structure and narrow coastal barrier systems. In the Bahamas, Andros Island is often cited as having one of the longest barriers in the Caribbean-Atlantic region, or even in
the world, but it is a fringing and coastal barrier system,
without any deep lagoon. Other small barrier systems are
found in Caribbean Panama, Columbian Islands (e.g., Providence Island), Venezuela (Los Roques), Greater Antilles
(especially Cuba, but also Haiti and Dominican Republic)
and Lesser Antilles (e.g., Guadeloupe), and in the Bahamas
(e.g., north of Little Bahama Bank).
In the Indian Ocean, the longest system is a nearly
1,000 km long drowned structure along the west coast of
Madagascar, at the edge of the shelf. It is poorly
documented, and was absent in the region coral reef maps
until recently (Andréfouët et al., 2009b), although it is visible in marine charts of this area. Southwest Madagascar
(the Toliara region), Mayotte Island, and on the other side
of the Mozambique channel, Mozambique, Kenya, and
Tanzania (e.g., the Tanga area) have small sections of barrier reefs, including coastal barrier systems. Barrier reefs
occur in Mauritius Island at various stages of development
(Montaggioni, 2005). The large outer Seychelles plateau,
also a deep subtidal system, present a barrier-like peripheral structure formed by large deep, drowned, platforms
intersected by deep passes. In the Eastern Indian Ocean,
the west coast of Australia displays the Ningaloo Reef system. It is generally described as a fringing reef, but its
structure and habitat zonations are consistent with the definition of a coastal barrier reef.
The Red Sea has unique reef morphologies (Purkis,
et al., 2010), and several areas can be classified as barrier
reefs especially in Saudi Arabia (e.g., Al Wadj Bank area),
Egypt (tip of the Sinai Peninsula), and South Sudan. Most
of the Red Sea is bordered by fringing structures, which
for the widest show coastal barrier like-patterns.
Southeast Asia (especially in the Philippines and Indonesia), including Japan (Ryukyus Archipelago) display
numerous significant barrier reefs at various stage of
development (e.g., Spermonde Barrier Reef ), from coastal
to outer barrier reefs, including drowned ones (e.g., east of
BARRIER REEF (RIBBON REEF)
103
aerial photography, but he accounted for new data from
coring and from recent advances in understanding reef
growth. He showed that previous interpretations could
be misleading to infer a reef-growth development typology. Then, Hopley (1982) established a new classification
for the shelf reef of the Great Barrier Reef, including as
a specific zone the northern Ribbon Reefs, which display
a typical barrier morphology, with linear reefs parallel to
the continent, from 15
S up to 10
S in the Torres Strait.
South of Cooktown, the Great Barrier Reef consists of
a dense (e.g., the Swains group) to open matrix (e.g., the
Capricorn Bunker group) of shelf patch reefs, also called
platform reefs. The size of these patch reefs displays
a wide range, from a few hundreds of square meters to several tens of square kilometers. The unique and photogenic
Pompey Group, at 21
S displays a general barrier linear
morphology, with very large individual reefs characterized by subsurface karstic formations, blue holes, and
numerous deep and narrow channels.
Recently, remote sensing technology provided complete coverage of reefs worldwide using high spatial resolution Landsat satellite images (Andréfouët et al., 2006a).
This new data set allows examining in details all barrier
reefs worldwide. A detailed typology was inferred,
although it cannot be precisely coupled in most locations
with coring data to relate planar morphology with genetic
processes like in Hopley (1982). Thus far, this link has
been done only for New Caledonia (Andréfouët et al.,
2009a). Nevertheless, the diversity of morphologies are
potential indicators of local processes keeping in mind
the same caveats that Hopley (1982) put forth for the interpretation of Great Barrier Reef structures.
Landsat images suggested a hierarchical typology that
can be applied to oceanic and continental reefs. In this
typology, atolls are described separately, and thus atoll
rims are not considered like barrier reefs. First, two main
types of barrier reefs are distinguished on the top of the
hierarchy: the outer shelf and intra-shelf barrier. The
intra-shelf barrier is composed of continuous lines of reefs
in a lagoon, well separated from the outer shelf barrier.
Then, these two types of barrier reefs can themselves be
separated into barrier, multiple-barrier, faro-barrier, imbricated-barrier, coastal-barrier, and fringing-barrier types.
Multiple-barriers are made of series of parallel reef flats
developed close to each other and sometimes connected
together (see Guilcher, 1988). A faro-barrier is a structure
made of faros, or in other words a series of reefs with
a central enclosed lagoon. An imbricated-barrier is a section of barrier, which is turning around itself, the outer side
turning to the inner side when bending, thus changing
completely the degree of exposure and the types of
habitats. An imbricated-barrier can also be a barrier that
terminates in the lagoon of a second separate barrier.
A coastal-barrier is an intermediate configuration between
a barrier and a fringing reef, that is, there is no deep
lagoon, but a shallow sedimentary terrace that clearly separates outer reef flat habitats from fringing-like habitats.
A fringing-barrier is a section of barrier that harbors large
islands, thus displaying fringing-type habitats in an outer
barrier environment. Examples of all these barrier reef
types are given in Figure 1. These types describe the diversity of barrier reefs worldwide based on their morphology
visible on remote-sensing images.
Locations
Beside the Australian Great Barrier Reef discussed above,
barrier reefs are found in all coral reef provinces worldwide. In the Caribbean Seas and Atlantic Ocean, the longest system is offshore Belize, approximately 200 km
long (Figure 1). This Belizean section is actually the only
true outer barrier system of the so-called Meso-American
Barrier Reef System (Mexican Yucatan, Belize, Guatemala
and Honduras), which includes fringing reefs for most of its
length. Honduras Bay Islands include a drowned barrier
structure and narrow coastal barrier systems. In the Bahamas, Andros Island is often cited as having one of the longest barriers in the Caribbean-Atlantic region, or even in
the world, but it is a fringing and coastal barrier system,
without any deep lagoon. Other small barrier systems are
found in Caribbean Panama, Columbian Islands (e.g., Providence Island), Venezuela (Los Roques), Greater Antilles
(especially Cuba, but also Haiti and Dominican Republic)
and Lesser Antilles (e.g., Guadeloupe), and in the Bahamas
(e.g., north of Little Bahama Bank).
In the Indian Ocean, the longest system is a nearly
1,000 km long drowned structure along the west coast of
Madagascar, at the edge of the shelf. It is poorly
documented, and was absent in the region coral reef maps
until recently (Andréfouët et al., 2009b), although it is visible in marine charts of this area. Southwest Madagascar
(the Toliara region), Mayotte Island, and on the other side
of the Mozambique channel, Mozambique, Kenya, and
Tanzania (e.g., the Tanga area) have small sections of barrier reefs, including coastal barrier systems. Barrier reefs
occur in Mauritius Island at various stages of development
(Montaggioni, 2005). The large outer Seychelles plateau,
also a deep subtidal system, present a barrier-like peripheral structure formed by large deep, drowned, platforms
intersected by deep passes. In the Eastern Indian Ocean,
the west coast of Australia displays the Ningaloo Reef system. It is generally described as a fringing reef, but its
structure and habitat zonations are consistent with the definition of a coastal barrier reef.
The Red Sea has unique reef morphologies (Purkis,
et al., 2010), and several areas can be classified as barrier
reefs especially in Saudi Arabia (e.g., Al Wadj Bank area),
Egypt (tip of the Sinai Peninsula), and South Sudan. Most
of the Red Sea is bordered by fringing structures, which
for the widest show coastal barrier like-patterns.
Southeast Asia (especially in the Philippines and Indonesia), including Japan (Ryukyus Archipelago) display
numerous significant barrier reefs at various stage of
development (e.g., Spermonde Barrier Reef ), from coastal
to outer barrier reefs, including drowned ones (e.g., east of
BARRIER REEF (RIBBON REEF)
103