special environments met in caves that can be related to
water chemistry (e.g., elevated carbonate concentration),
anoxia, low light intensity, lack of physical disturbance, or
exclusion of grazing metazoa.
Bibliography
Backshall, D. G., Barnett, J., Davies, P. J., Duncan, D. C.,
Harvey, N., Hopley, D., Isdale, P. J., Jennings, J. N., and
Moss, R., 1979. Drowned dolines - the blue holes of the Pompey
reefs, Great Barrier Reef. BMR Journal of Australian Geology &
Geophysics, 4, 99–109.
Dill, R. F., 1977. The Blue Holes - geologically significant sink holes
and caves off British Honduras and Andros. In Proceedings 3rd
International Coral Reef Symposium, Vol. 2, pp. 238–242.
Fischer, A. G., 1962. The Lofer Cyclothems of the Alpine Triassic.
Kansas Geological Survey Bulletin, 169, 107–149.
Gascoyne, M., Benjamin, G. J., Schwarcz, H. P., and Ford, D. C.,
1979. Sea-level lowering during the Illinoian glaciation: evidence from a Bahama “blue hole”. Science, 205, 806–808.
Gischler, E., Shinn, E. A., Oschmann, W., Fiebig, J., and
Buster, N. A., 2008. A 1,500 year Holocene Caribbean climate
archive from the Blue Hole, Lighthouse Reef, Belize. Journal
of Coastal Research, 24, 1495–1505.
Sachet, M. H., 1962. Geography and land ecology of Clipperton
Island. Atoll Research Bulletin, 86, 1–115.
Schwabe, S., and Herbert, R. A., 2004. Black holes of the Bahamas:
what they are and why they are black. Quaternary International,
121, 3–11.
Taylor, P. D., and Palmer, T. J., 1994. Submarine caves in a Jurassic
reef (La Rochelle, France) and the evolution of cave biotas.
Naturwissenschaften, 81, 357–360.
Wyrwoll, K.-H., Zhu, Z. R., Collins, L. B., and Hatcher, B. G.,
2006. Origin of Blue Hole structures in coral reefs of the
Houtman Abrolhos of Western Australia. Journal of Coastal
Research, 22, 202–208.
Cross-references
Atolls
Lagoons
Sclerochronology
BOAT CHANNEL
Roger McLean
University of New South Wales, Canberra, ACT, Australia
Synonyms
Back-reef trough or tide pool; Moat; Shallow lagoon
Description
There are two types of boat channels. Artificially constructed boat channels are dug, dredged, or blasted through
a reef to allow access to land or wharf facilities. Such channels are usually cut normal to the reef edge or at an oblique
angle and require continual maintenance. Natural boat
channels, and the ones described in classical reef literature,
are depressions that run parallel to the shore and are
generally associated with the back reef area of fringing
reefs. Darwin (Darwin, Charles (1809–1882)) described
an example from Mauritius as a flat space with sandy bottom, located between the outer margin of the fringing reef
and the island shore, the depression being sufficiently deep
to offer “a safe coasting channel for boats.”
To Darwin the reason for a boat channel was clear;
a reef on a sloping surface would at first grow up some distance from the shore, and, because coral on the outer edge
would grow much more vigorously than those inshore,
a “flat space” would form behind. Others have suggested
a more dynamic process, where water driven across the
fringing reef by waves and currents, flows laterally out
through the boat channel maintaining its form. Because
the channels fail to drain completely at low tide they are
frequently colonized by marine grasses, algae, and sometimes corals.
Not all fringing reefs have boat channels. Those that do
have a myriad of length, width, depth, and continuity
scales fully described by Guilcher (1988) with examples
of incipient forms from the Gulf of Aquaba, intermediate
forms from the Seychelles and Sri Lanka, and well developed forms from Madagascar, New Caledonia, and Lord
Howe Island.
Narrow boat channels are also known from atolls and
table reefs where they separate the island shore from the
reef flat, do not drain completely at low tide, and generally
have sparse coral cover because of sediment movement.
Such channels are also known as Moats.
In a recent review of fringing reef growth and morphology Kennedy and Woodroffe (2002) prefer the less archaic
and less ambiguous term “shallow lagoon” rather than
boat channel for the back reef depression on fringing reefs.
And, they provide details of the 2 km wide and 1.5 m deep
shallow lagoon on Lord Howe Island.
Bibliography
Guilcher, A., 1988. Coral Reef Geomorphology. Chichester: Wiley,
p. 228.
Kennedy, D. M., and Woodroffe, C. D., 2002. Fringing reef growth
and morphology: a review. Earth Science Reviews, 57, 255.
Cross-references
Fringing Reef Circulation
Fringing Reefs
Moating
Moats
BOULDER BEACHES
Jonathan Nott
James Cook University, Cairns, QLD, Australia
Synonyms
Coarse clast beaches; Gravel beaches; Storm beaches
BOULDER BEACHES
165
water chemistry (e.g., elevated carbonate concentration),
anoxia, low light intensity, lack of physical disturbance, or
exclusion of grazing metazoa.
Bibliography
Backshall, D. G., Barnett, J., Davies, P. J., Duncan, D. C.,
Harvey, N., Hopley, D., Isdale, P. J., Jennings, J. N., and
Moss, R., 1979. Drowned dolines - the blue holes of the Pompey
reefs, Great Barrier Reef. BMR Journal of Australian Geology &
Geophysics, 4, 99–109.
Dill, R. F., 1977. The Blue Holes - geologically significant sink holes
and caves off British Honduras and Andros. In Proceedings 3rd
International Coral Reef Symposium, Vol. 2, pp. 238–242.
Fischer, A. G., 1962. The Lofer Cyclothems of the Alpine Triassic.
Kansas Geological Survey Bulletin, 169, 107–149.
Gascoyne, M., Benjamin, G. J., Schwarcz, H. P., and Ford, D. C.,
1979. Sea-level lowering during the Illinoian glaciation: evidence from a Bahama “blue hole”. Science, 205, 806–808.
Gischler, E., Shinn, E. A., Oschmann, W., Fiebig, J., and
Buster, N. A., 2008. A 1,500 year Holocene Caribbean climate
archive from the Blue Hole, Lighthouse Reef, Belize. Journal
of Coastal Research, 24, 1495–1505.
Sachet, M. H., 1962. Geography and land ecology of Clipperton
Island. Atoll Research Bulletin, 86, 1–115.
Schwabe, S., and Herbert, R. A., 2004. Black holes of the Bahamas:
what they are and why they are black. Quaternary International,
121, 3–11.
Taylor, P. D., and Palmer, T. J., 1994. Submarine caves in a Jurassic
reef (La Rochelle, France) and the evolution of cave biotas.
Naturwissenschaften, 81, 357–360.
Wyrwoll, K.-H., Zhu, Z. R., Collins, L. B., and Hatcher, B. G.,
2006. Origin of Blue Hole structures in coral reefs of the
Houtman Abrolhos of Western Australia. Journal of Coastal
Research, 22, 202–208.
Cross-references
Atolls
Lagoons
Sclerochronology
BOAT CHANNEL
Roger McLean
University of New South Wales, Canberra, ACT, Australia
Synonyms
Back-reef trough or tide pool; Moat; Shallow lagoon
Description
There are two types of boat channels. Artificially constructed boat channels are dug, dredged, or blasted through
a reef to allow access to land or wharf facilities. Such channels are usually cut normal to the reef edge or at an oblique
angle and require continual maintenance. Natural boat
channels, and the ones described in classical reef literature,
are depressions that run parallel to the shore and are
generally associated with the back reef area of fringing
reefs. Darwin (Darwin, Charles (1809–1882)) described
an example from Mauritius as a flat space with sandy bottom, located between the outer margin of the fringing reef
and the island shore, the depression being sufficiently deep
to offer “a safe coasting channel for boats.”
To Darwin the reason for a boat channel was clear;
a reef on a sloping surface would at first grow up some distance from the shore, and, because coral on the outer edge
would grow much more vigorously than those inshore,
a “flat space” would form behind. Others have suggested
a more dynamic process, where water driven across the
fringing reef by waves and currents, flows laterally out
through the boat channel maintaining its form. Because
the channels fail to drain completely at low tide they are
frequently colonized by marine grasses, algae, and sometimes corals.
Not all fringing reefs have boat channels. Those that do
have a myriad of length, width, depth, and continuity
scales fully described by Guilcher (1988) with examples
of incipient forms from the Gulf of Aquaba, intermediate
forms from the Seychelles and Sri Lanka, and well developed forms from Madagascar, New Caledonia, and Lord
Howe Island.
Narrow boat channels are also known from atolls and
table reefs where they separate the island shore from the
reef flat, do not drain completely at low tide, and generally
have sparse coral cover because of sediment movement.
Such channels are also known as Moats.
In a recent review of fringing reef growth and morphology Kennedy and Woodroffe (2002) prefer the less archaic
and less ambiguous term “shallow lagoon” rather than
boat channel for the back reef depression on fringing reefs.
And, they provide details of the 2 km wide and 1.5 m deep
shallow lagoon on Lord Howe Island.
Bibliography
Guilcher, A., 1988. Coral Reef Geomorphology. Chichester: Wiley,
p. 228.
Kennedy, D. M., and Woodroffe, C. D., 2002. Fringing reef growth
and morphology: a review. Earth Science Reviews, 57, 255.
Cross-references
Fringing Reef Circulation
Fringing Reefs
Moating
Moats
BOULDER BEACHES
Jonathan Nott
James Cook University, Cairns, QLD, Australia
Synonyms
Coarse clast beaches; Gravel beaches; Storm beaches
BOULDER BEACHES
165