reef crest species along many Caribbean shelf margins
until at least 7,000 years ago.
The process of reef drowning and back-stepping often
began while the soon-to-be-abandoned seaward reefs
were still active. Because depths over the two structures
appear to have been similar, it is unclear why the seaward
reef would have lagged behind its more protected landward counterpart – which was probably closer to sources
of sediment stress. Whatever the sea-level scenario, the
movement of larvae from one reef to the next was probably no more difficult than it is today. Thus, efficient larval
transfer and a stable reef community can be maintained
during periods of rapidly changing sea level even when
reef accretion cannot.
A simpler model
The lower section of the profile in Figure 8b is based on
Barbados (Fairbanks, 1989), but similar scenarios probably occurred throughout the region. The shallow reefs
are based on St. Croix, but generally mimic Puerto Rico
and Florida. Along the shelf-edge, the lower reef (labeled
“1”) was cored by Adey et al. (1977b) and formed more
than 10,500 years ago. Accretion was compromised as
the adjacent ridgetop flooded. Along the raised rim of
Lang Bank (labeled “2”), accretion was variable in timing
but not structure. At most sites, A. palmata dominated the
bank top and remained as the primary reef builder until at
least 7,000 years ago. Back-stepping to the inner-shelf
reefs was variable in both timing (antecedent topography,
sea-level elevation and rate of change, physical processes)
and community structure (water quality, wave energy).
Based on the above discussion, the critical points include:
1. Reef start-up, building, and demise are tied more simply to the relationship between sea-level rise and local
topography. In this scenario, less regional synchronicity is anticipated, and whether a reef is presently at
sea level is mostly a function of the rate of sea-level rise
when accretion began.
2. Both the spatial continuity and temporal persistence
of reduced water quality after platform flooding are
reduced. Bioerosion was perhaps as important as
reduced coral productivity in delaying initial reef
preservation.
3. The need for “inimical bank waters” or sudden leaps in
sea level to induce reef abandonment or back-steeping
(Schlager, 1981) is reduced. Both have undoubtedly
played important roles, but the shifting of reefs to
shallower sites can be a more orderly and less dramatic
process than has been traditionally assumed.
4. Larval dispersal was probably no more difficult during
episodes of back-stepping than it is today. Thus, the
need for dramatic “reassembly” following deglaciation
is minimized.
5. The high accretion rates often cited as “typical” for
Caribbean reefs are less common than previously characterized and are rarely representative of the pattern
seen throughout the reef in which they were found.
Accretion rates closer to 3–4 m/ky (perhaps 3–6 m/ky
on the Great Barrier Reef) are consistent with the
decrease in the rate of sea-level rise between 8,000
and 6,000 years ago being a “tipping point” that caused
a general shift from transgression to regression.
6. A. palmata was probably a more persistent reef builder
after platform flooding than has been assumed, and it
remained as an important shelf-edge reef builder from
10,000 to at least 7,000 years ago.
7. The eventual decline of A. palmata across the region
starting around 7,000 years ago is enigmatic inasmuch
as any potential for “inimical bank waters” had long
passed, sea level was slowing down dramatically, and
shelf-edge reefs were well above the accepted depth
limit for active reef accretion. Corollary to this, it is
not clear why many reefs were abandoned inasmuch
as they sat at depths similar to new reefs closer to land
and the attendant sources of stress.
Bibliography
Adey, W., 1975. The algal ridges and coral reefs of St. Croix – their
structure and Holocene development. Atoll Research Bulletin,
187, 1–67.
Adey, W., 1978. Coral reef morphogenesis: a multidimensional
model. Science, 202, 831–837.
Adey, W., and Burke, R., 1976. Holocene bioherms (algal ridges
and bank-barrier reefs) of the eastern Caribbean. Geological
Society of America Bulletin, 87, 95–109.
Adey, W., and Burke, R., 1977. Holocene bioherms of the Lesser
Antilles – geologic control of development. In Frost, S., Weiss,
M., and Saunders, J. (eds.), Reefs and Related Carbonates –
Ecology and Sedimentology. AAPG Studies in Geology No. 4.
Tulsa, Okla: AAPG, pp. 67–81.
Adey, W., Adey, P., Burke, R., and Kaufman, L., 1977a. The Holocene reef systems of eastern Martinique, French West Indies.
Atoll Research Bulletin, 218, 1–40.
Adey, W., Macintyre, I., Stuckenrath, R., and Dill, R., 1977b. Relict
barrier reef system off St. Croix: its implications with respect to
late Cenozoic coral reef development in the western Atlantic. In
Proceedings of Third International Coral Reef Symposium. Vol. 2,
pp. 15–21.
Bard, E., Hamelin, B., and Fairbanks, R. G., 1990. U/Th ages
obtained by mass spectrometry in corals from Barbados: sea
level during the past 130,000 years. Nature, 346, 456–458.
Bard, E., Hamelin, B., and Delanghe-Sabatier, D., 2010. Deglacial
meltwater pulse 1B and Younger Dryas sea levels revisited with
Boreholes at Tahiti. Science, 327, 1235–1237.
Burke, R., Adey, W., and Macintyre, I., 1989. Overview of the Holocene history, architecture and structural components of Tague
reef and lagoon. In Hubbard, D. (ed.), Terrestrial and Marine
Geology of St. Croix, U.S. Virgin Islands. St. Croix, USVI: West
Indies Laboratory. Special Publication, 8, pp. 105–109.
Davis, W. M., 1926. The Lesser Antilles. American Geographical
Society Publication 2, p. 207.
Edinger, E. N., and Risk, M. J., 1997. Sponge borehole size as
a relative measure of bioerosion and paleoproductivity. Lethaia,
29, 275–286.
Fairbanks, R., 1989. A 17,000 year glacio-eustatic sea level record:
influence of glacial melting rates on the Younger Dryas event
and deep ocean circulation. Nature, 342, 637–642.
Geister, J., 1977. The influence of wave exposure on ecological
zonation of Caribbean coral reefs. In Proceedings of Third International Coral Reef Symposium. Vol. 1, pp. 23–29.
346
EASTERN CARIBBEAN CORAL REEFS
until at least 7,000 years ago.
The process of reef drowning and back-stepping often
began while the soon-to-be-abandoned seaward reefs
were still active. Because depths over the two structures
appear to have been similar, it is unclear why the seaward
reef would have lagged behind its more protected landward counterpart – which was probably closer to sources
of sediment stress. Whatever the sea-level scenario, the
movement of larvae from one reef to the next was probably no more difficult than it is today. Thus, efficient larval
transfer and a stable reef community can be maintained
during periods of rapidly changing sea level even when
reef accretion cannot.
A simpler model
The lower section of the profile in Figure 8b is based on
Barbados (Fairbanks, 1989), but similar scenarios probably occurred throughout the region. The shallow reefs
are based on St. Croix, but generally mimic Puerto Rico
and Florida. Along the shelf-edge, the lower reef (labeled
“1”) was cored by Adey et al. (1977b) and formed more
than 10,500 years ago. Accretion was compromised as
the adjacent ridgetop flooded. Along the raised rim of
Lang Bank (labeled “2”), accretion was variable in timing
but not structure. At most sites, A. palmata dominated the
bank top and remained as the primary reef builder until at
least 7,000 years ago. Back-stepping to the inner-shelf
reefs was variable in both timing (antecedent topography,
sea-level elevation and rate of change, physical processes)
and community structure (water quality, wave energy).
Based on the above discussion, the critical points include:
1. Reef start-up, building, and demise are tied more simply to the relationship between sea-level rise and local
topography. In this scenario, less regional synchronicity is anticipated, and whether a reef is presently at
sea level is mostly a function of the rate of sea-level rise
when accretion began.
2. Both the spatial continuity and temporal persistence
of reduced water quality after platform flooding are
reduced. Bioerosion was perhaps as important as
reduced coral productivity in delaying initial reef
preservation.
3. The need for “inimical bank waters” or sudden leaps in
sea level to induce reef abandonment or back-steeping
(Schlager, 1981) is reduced. Both have undoubtedly
played important roles, but the shifting of reefs to
shallower sites can be a more orderly and less dramatic
process than has been traditionally assumed.
4. Larval dispersal was probably no more difficult during
episodes of back-stepping than it is today. Thus, the
need for dramatic “reassembly” following deglaciation
is minimized.
5. The high accretion rates often cited as “typical” for
Caribbean reefs are less common than previously characterized and are rarely representative of the pattern
seen throughout the reef in which they were found.
Accretion rates closer to 3–4 m/ky (perhaps 3–6 m/ky
on the Great Barrier Reef) are consistent with the
decrease in the rate of sea-level rise between 8,000
and 6,000 years ago being a “tipping point” that caused
a general shift from transgression to regression.
6. A. palmata was probably a more persistent reef builder
after platform flooding than has been assumed, and it
remained as an important shelf-edge reef builder from
10,000 to at least 7,000 years ago.
7. The eventual decline of A. palmata across the region
starting around 7,000 years ago is enigmatic inasmuch
as any potential for “inimical bank waters” had long
passed, sea level was slowing down dramatically, and
shelf-edge reefs were well above the accepted depth
limit for active reef accretion. Corollary to this, it is
not clear why many reefs were abandoned inasmuch
as they sat at depths similar to new reefs closer to land
and the attendant sources of stress.
Bibliography
Adey, W., 1975. The algal ridges and coral reefs of St. Croix – their
structure and Holocene development. Atoll Research Bulletin,
187, 1–67.
Adey, W., 1978. Coral reef morphogenesis: a multidimensional
model. Science, 202, 831–837.
Adey, W., and Burke, R., 1976. Holocene bioherms (algal ridges
and bank-barrier reefs) of the eastern Caribbean. Geological
Society of America Bulletin, 87, 95–109.
Adey, W., and Burke, R., 1977. Holocene bioherms of the Lesser
Antilles – geologic control of development. In Frost, S., Weiss,
M., and Saunders, J. (eds.), Reefs and Related Carbonates –
Ecology and Sedimentology. AAPG Studies in Geology No. 4.
Tulsa, Okla: AAPG, pp. 67–81.
Adey, W., Adey, P., Burke, R., and Kaufman, L., 1977a. The Holocene reef systems of eastern Martinique, French West Indies.
Atoll Research Bulletin, 218, 1–40.
Adey, W., Macintyre, I., Stuckenrath, R., and Dill, R., 1977b. Relict
barrier reef system off St. Croix: its implications with respect to
late Cenozoic coral reef development in the western Atlantic. In
Proceedings of Third International Coral Reef Symposium. Vol. 2,
pp. 15–21.
Bard, E., Hamelin, B., and Fairbanks, R. G., 1990. U/Th ages
obtained by mass spectrometry in corals from Barbados: sea
level during the past 130,000 years. Nature, 346, 456–458.
Bard, E., Hamelin, B., and Delanghe-Sabatier, D., 2010. Deglacial
meltwater pulse 1B and Younger Dryas sea levels revisited with
Boreholes at Tahiti. Science, 327, 1235–1237.
Burke, R., Adey, W., and Macintyre, I., 1989. Overview of the Holocene history, architecture and structural components of Tague
reef and lagoon. In Hubbard, D. (ed.), Terrestrial and Marine
Geology of St. Croix, U.S. Virgin Islands. St. Croix, USVI: West
Indies Laboratory. Special Publication, 8, pp. 105–109.
Davis, W. M., 1926. The Lesser Antilles. American Geographical
Society Publication 2, p. 207.
Edinger, E. N., and Risk, M. J., 1997. Sponge borehole size as
a relative measure of bioerosion and paleoproductivity. Lethaia,
29, 275–286.
Fairbanks, R., 1989. A 17,000 year glacio-eustatic sea level record:
influence of glacial melting rates on the Younger Dryas event
and deep ocean circulation. Nature, 342, 637–642.
Geister, J., 1977. The influence of wave exposure on ecological
zonation of Caribbean coral reefs. In Proceedings of Third International Coral Reef Symposium. Vol. 1, pp. 23–29.
346
EASTERN CARIBBEAN CORAL REEFS