(Cook Islands) (Purdy, 1974; Purdy and Winterer, 2001,
2006). Purdy and Winterer (2001, 2006) also found
a significant correlation between atoll and barrier reef
lagoon depths and precipitation rates. They showed statistically that barrier reef lagoon depths are not lower as compared to atoll lagoon depths as would be expected when
applying Darwin’s model of continued subsidence. Purdy
and Winterer (2006) also argued that fringing reefs located
within barrier reefs also do not fit the idea of a progressive
development of fringing and barrier reefs. Based on results
obtained during ocean drilling project legs 143 and
144 (Winterer et al., 1995; Haggerty and Premoli-Silva,
1995), Winterer and Metzler (1984) and Winterer (1998)
concluded that many guyots with Cretaceous reef caps
located in the western Pacific experienced a subaerial karst
phase before drowning, which enhanced their atoll
geomorphology.
The mechanisms of reef drowning, however, still
remain somewhat enigmatic and controversial. Grigg
(1982, 1997) suggested that movement of the lithospheric
plate has been transporting reefs of the Hawaiian chain out
of the warm tropical-subtropical realm toward higher latitudes where reef growth rates are progressively slower,
thereby causing reef demise and drowning. Hallock and
Schlager (1986) and Rougerie and Fagerstrom (1994)
argued that drowning of many mid-Cretaceous reefs,
including those in the Pacific, coincided with oceanic
anoxic events (OAEs), i.e., during the upwelling of
nutrient-rich, oxygen-depleted water masses. Wilson
et al. (1998) and Jenkyns and Wilson (1999) were able
to prove that numerous Cretaceous reefs, now forming
the tops of western Pacific guyots, were exterminated
when the reefs were situated in equatorial latitudes. Possibly, very high temperatures caused reef decline, as
observed today, e.g., during strong El Niño years. Reefbuilding scleractinian corals may lose their
photosymbionts, bleach, and eventually die off (HoeghGuldberg, 1999). Likewise, equatorial upwelling of
nutrient-rich waters might have been detrimental to coral
and rudist reef growth. Based on the observation that the
growth potential of corals and coral reefs usually exceeds
the rate of rise of sea-level, Schlager (1981) concluded that
only very rapid pulses of sea-level rise and/or environmental deterioration may cause reef drowning. While
some late Quaternary reefs in the Indo-Pacific region have
indeed been accreting at rates of up to 20 m/kyr
(Montaggioni, 2005), the majority of Holocene Atlantic
reefs accumulated with average rates of 3–5.5 m/kyr
(Gischler, 2008; Hubbard, 2009). These rates are well
below rapid rates of glacio-eustatic sea-level rise, e.g.,
during the last post-glacial and that predicted by the ICDP
for the twenty-first century. Thus, rapid sea-level rise
alone is a potential cause of reef drowning. Interestingly,
guyots, i.e., drowned atolls, exist adjacent to living atolls,
e.g., in the Marshall Islands. An instructive example is
Wodejabato (Sylvania) Guyot (Figure 1), which is positioned next to Bikini Atoll (Ladd et al., 1950; Hamilton,
1956; Schlanger et al., 1987). Wodejabato is a former atoll
reef that drowned in the latest Cretaceous and the top of
which is now 1,335 m below sea-level (Camoin et al.,
1998). In this case, environmental deterioration such as
nutrient excess cannot be used as an explanation for
drowning. It is highly unlikely that nutrient excess would
cause the demise of some reefs in the middle of the Pacific
Ocean while adjacent ones would not be harmed. A more
plausible explanation could be differences in the elevation
of the reef foundation. Elevation controls the timing and,
hence, the rate of initial eustatic sea-level rise over
a platform. The latter is crucial as full carbonate accretion
may be delayed initially due to the time necessary for
biotic colonization (Kim et al., 2012). Likewise, the relief
of the inundated reef pedestal during sea-level rise, providing a variety of habitats of reef builders, might be of
significance (Camoin et al., 1998).
Summary
Many atolls and guyots in the Pacific are genetically
connected by the processes of subsidence of volcanic
islands, reef accretion, and reef drowning. Still, subsidence alone may not satisfactorily explain reef development and drowning. Sea-level is another crucial factor of
reef development. Sea-level rise results in reef aggradation
and retrogradation and/or backstepping. Sea-level stalling
and fall may cause progradation and karstification during
subaerial exposure. Possible causes of drowning include
rapid pulses of sea-level rise, reef elevation and relief,
and environmental stress such as low sea-surface temperatures as well as high sea-surface temperatures and
upwelling of nutrient-rich and oxygen-depleted waters.
Bibliography
Belopolsky, A. V., and Droxler, A., 2003. Imaging Tertiary carbonate systems – the Maldives, Indian Ocean: insights into carbonate sequence interpretation. Leading Edge, 22, 646–652.
Boehlert, G. W., and Genin, A., 1987. A review of the effects of seamounts on biological processes. Geophysical Monograph, 43,
319–334.
Camoin, G. F., Arnaud-Vanneau, A., Bergersen, D. D., Enos, P., and
Ebren, P., 1998. Development and demise of mid-oceanic carbonate platforms, Wodejabato Guyot (NW Pacific). International Association of Sedimentologists Special Publication, 25,
39–67.
Camoin, G., Ebren, P., Eisenhauer, A., Bard, E., and Faure, G.,
2001. A 300,000 years record of sea-level changes, Mururoa
Atoll (French Polynesia). Palaeogeography Palaeoclimatology
Palaeoecology, 175, 325–341.
Daly, R. A., 1915. The glacial-control theory of coral reefs. Proceedings of the American Academy of Arts and Sciences, 51,
157–251.
Darwin, C. R., 1842. The Structure and Distribution of Coral Reefs.
London: Smith Elder, 214 p.
Davies, T. A., Wilde, P., and Clague, D. A., 1972. Koko Seamount:
a major guyot at the southern end of the Emperor Seamounts.
Marine Geology, 13, 311–321.
Dickinson, W. R., 2009. Pacific atoll living: how long already and
until when? GSA Today, 19, 4–10.
Flood, P., 1999. Development of northwest Pacific guyots: general
results from Ocean Drilling Program legs 143 and 144. Island
Arc, 8, 92–98.
GUYOT, ATOLL
307
2006). Purdy and Winterer (2001, 2006) also found
a significant correlation between atoll and barrier reef
lagoon depths and precipitation rates. They showed statistically that barrier reef lagoon depths are not lower as compared to atoll lagoon depths as would be expected when
applying Darwin’s model of continued subsidence. Purdy
and Winterer (2006) also argued that fringing reefs located
within barrier reefs also do not fit the idea of a progressive
development of fringing and barrier reefs. Based on results
obtained during ocean drilling project legs 143 and
144 (Winterer et al., 1995; Haggerty and Premoli-Silva,
1995), Winterer and Metzler (1984) and Winterer (1998)
concluded that many guyots with Cretaceous reef caps
located in the western Pacific experienced a subaerial karst
phase before drowning, which enhanced their atoll
geomorphology.
The mechanisms of reef drowning, however, still
remain somewhat enigmatic and controversial. Grigg
(1982, 1997) suggested that movement of the lithospheric
plate has been transporting reefs of the Hawaiian chain out
of the warm tropical-subtropical realm toward higher latitudes where reef growth rates are progressively slower,
thereby causing reef demise and drowning. Hallock and
Schlager (1986) and Rougerie and Fagerstrom (1994)
argued that drowning of many mid-Cretaceous reefs,
including those in the Pacific, coincided with oceanic
anoxic events (OAEs), i.e., during the upwelling of
nutrient-rich, oxygen-depleted water masses. Wilson
et al. (1998) and Jenkyns and Wilson (1999) were able
to prove that numerous Cretaceous reefs, now forming
the tops of western Pacific guyots, were exterminated
when the reefs were situated in equatorial latitudes. Possibly, very high temperatures caused reef decline, as
observed today, e.g., during strong El Niño years. Reefbuilding scleractinian corals may lose their
photosymbionts, bleach, and eventually die off (HoeghGuldberg, 1999). Likewise, equatorial upwelling of
nutrient-rich waters might have been detrimental to coral
and rudist reef growth. Based on the observation that the
growth potential of corals and coral reefs usually exceeds
the rate of rise of sea-level, Schlager (1981) concluded that
only very rapid pulses of sea-level rise and/or environmental deterioration may cause reef drowning. While
some late Quaternary reefs in the Indo-Pacific region have
indeed been accreting at rates of up to 20 m/kyr
(Montaggioni, 2005), the majority of Holocene Atlantic
reefs accumulated with average rates of 3–5.5 m/kyr
(Gischler, 2008; Hubbard, 2009). These rates are well
below rapid rates of glacio-eustatic sea-level rise, e.g.,
during the last post-glacial and that predicted by the ICDP
for the twenty-first century. Thus, rapid sea-level rise
alone is a potential cause of reef drowning. Interestingly,
guyots, i.e., drowned atolls, exist adjacent to living atolls,
e.g., in the Marshall Islands. An instructive example is
Wodejabato (Sylvania) Guyot (Figure 1), which is positioned next to Bikini Atoll (Ladd et al., 1950; Hamilton,
1956; Schlanger et al., 1987). Wodejabato is a former atoll
reef that drowned in the latest Cretaceous and the top of
which is now 1,335 m below sea-level (Camoin et al.,
1998). In this case, environmental deterioration such as
nutrient excess cannot be used as an explanation for
drowning. It is highly unlikely that nutrient excess would
cause the demise of some reefs in the middle of the Pacific
Ocean while adjacent ones would not be harmed. A more
plausible explanation could be differences in the elevation
of the reef foundation. Elevation controls the timing and,
hence, the rate of initial eustatic sea-level rise over
a platform. The latter is crucial as full carbonate accretion
may be delayed initially due to the time necessary for
biotic colonization (Kim et al., 2012). Likewise, the relief
of the inundated reef pedestal during sea-level rise, providing a variety of habitats of reef builders, might be of
significance (Camoin et al., 1998).
Summary
Many atolls and guyots in the Pacific are genetically
connected by the processes of subsidence of volcanic
islands, reef accretion, and reef drowning. Still, subsidence alone may not satisfactorily explain reef development and drowning. Sea-level is another crucial factor of
reef development. Sea-level rise results in reef aggradation
and retrogradation and/or backstepping. Sea-level stalling
and fall may cause progradation and karstification during
subaerial exposure. Possible causes of drowning include
rapid pulses of sea-level rise, reef elevation and relief,
and environmental stress such as low sea-surface temperatures as well as high sea-surface temperatures and
upwelling of nutrient-rich and oxygen-depleted waters.
Bibliography
Belopolsky, A. V., and Droxler, A., 2003. Imaging Tertiary carbonate systems – the Maldives, Indian Ocean: insights into carbonate sequence interpretation. Leading Edge, 22, 646–652.
Boehlert, G. W., and Genin, A., 1987. A review of the effects of seamounts on biological processes. Geophysical Monograph, 43,
319–334.
Camoin, G. F., Arnaud-Vanneau, A., Bergersen, D. D., Enos, P., and
Ebren, P., 1998. Development and demise of mid-oceanic carbonate platforms, Wodejabato Guyot (NW Pacific). International Association of Sedimentologists Special Publication, 25,
39–67.
Camoin, G., Ebren, P., Eisenhauer, A., Bard, E., and Faure, G.,
2001. A 300,000 years record of sea-level changes, Mururoa
Atoll (French Polynesia). Palaeogeography Palaeoclimatology
Palaeoecology, 175, 325–341.
Daly, R. A., 1915. The glacial-control theory of coral reefs. Proceedings of the American Academy of Arts and Sciences, 51,
157–251.
Darwin, C. R., 1842. The Structure and Distribution of Coral Reefs.
London: Smith Elder, 214 p.
Davies, T. A., Wilde, P., and Clague, D. A., 1972. Koko Seamount:
a major guyot at the southern end of the Emperor Seamounts.
Marine Geology, 13, 311–321.
Dickinson, W. R., 2009. Pacific atoll living: how long already and
until when? GSA Today, 19, 4–10.
Flood, P., 1999. Development of northwest Pacific guyots: general
results from Ocean Drilling Program legs 143 and 144. Island
Arc, 8, 92–98.
GUYOT, ATOLL
307