Island (Pirazzoli et al., 1991; Bard et al., 1995) and again
on Alor Island (Hantoro et al., 1994). In Cape Laundi
(Sumba), Pirazzoli et al. (1991) described the occurrence
of six reef complexes labeled I–VI, reaching an altitude
of 475 m and dated by Electron Spin Resonance and Uranium series methods at 1 million years. The accurate dating of corals from the reef complexes I and II revealed
a polycyclic origin for these terraces with ages from the
MIS 5 (86, 105, 125 ka in the complex I and 130 ka in
the complex II) and MIS 9 (280 and 355 ka in the complex
II). The sequence of raised reefs on Alor Island described
by Hantoro et al. (1994) is composed of six main coral terraces reaching an altitude of 700 m. Uranium series dating
methods provided data to identify the terraces from the
Holocene, MIS 5c, 5e, and 7. Based on the uplift rate of
the dated terraces, an age was calculated for the highest
terraces.
Red Sea
The Red Sea (see Red Sea and Gulf of Aqaba) region is
tectonically active as the Red Sea has been opened by seafloor spreading. In this region, a series of raised terraces
was reported by various authors. In the southern Sinaï,
Gvirtzman et al. (1992) reported the occurrence of several
emerged reefs distributed into several morphological complexes. Gvirtzman (1994) performed a morphological
description of these features and provided U/Th dating
records for some of these terraces. Using these dates
and taking into account the uplift rate, he estimated the
age of other terraces which were not dated. As a result,
ten low and high sea-level stands were identified from
today to 330 ka. In another site in the Red Sea, in the
coastal plain of Egypt, El Moursi et al. (1994) surveyed
a sequence of eight emerged coral terraces including
morphological description and Uranium series dating.
The highest terraces labeled 8 reach an altitude ranging
from 9 to 35 m, the intermediary terraces 5–7 from 22
to 32 m, and the lowest terraces 1–4 from 2 to 9 m.
Because the coral from the highest terraces were
recrystallized, only the lowest terraces 1–3 were dated
from 72 to 131 ka with a large range of intermediary
dates. These dates clearly indicate that these coral reefs
were formed during the last interglacial period (125 ka,
MIS 5). Based on the chronostratigraphy of the sea-level
variations, these authors advanced the hypothesis that
the terraces 5–7 were formed during the MIS 7
(230 ka) and the terrace 8 during the MIS 9 (330 ka).
Lithospheric flexure
Emerged uplifted coral terraces and atolls can provide
proof of the occurrence of lithospheric flexures due to
a bulge at the rear of trenches or due to the loading of
active volcanos in hotspot areas (e.g., Lambeck, 1981).
In the central Pacific, McNutt and Menard (1978)
observed the presence of raised atolls in the Cook and
Society archipelagos in the vicinity of still or recently
active volcanoes resulting from deformation caused by
volcanic loading. They performed a model taking into
account the elevation of these raised atolls which can give
reliable data for the lithospheric flexure. Pirazzoli and
Montaggioni (1998) dated some of the raised corals which
were interpreted as resulting from this lithospheric flexure.
The elevation of coral reefs in the vicinity of New Caledonia in the South-West Pacific provides another example of
lithospheric deformation (Figure 5). The islands of the
Loyalty ridge, from the south to the north, Maré, Lifou,
and Ouvéa are uplifted close to the Vanuatu trench where
the Australian plate dips beneath the Pacific plate and
the North Fiji basin microplate. Only the eastern part
of Ouvéa is uplifted, while the western part is still
submerged. The uplift of the Loyalty Islands and the differences of elevation observed at Ouvéa illustrate particularly well the lithospheric deformation of the bulge
formed just at the rear of the subduction zone (Dubois
et al., 1974, 1988) as also confirmed by the magnetostratigraphy performed on Maré Island (Guyomard et al.,
1996). Another example of lithospheric flexure marked
by raised corals can be found in the Hawaii hotspot area
(Grigg and Jones, 1997). Although the numerical models
agree with the observations, these authors did not exclude
the coexisting presence of tsunami deposits at this site.
Isostatic readjustment
On numerous Indo-Pacific islands and reefs, less prominent emerged features have been described including
abraded reef flats, emerged cemented deposits (beneath
which in situ coral heads may occur), and microatolls
growing at heights above that at which they grow today
(e.g., Dickinson, 2004). A mid to late Holocene age has
been established for these features, which generally show
an emergence of between 1 and 3 m. The occurrence of
this level and its altitude in 92 records from the Pacific
were reviewed by Grossman et al. (1998). These islands
far from the polar regions have been submitted to isostatic
and gravitational readjustments resulting from the meltwater load on the oceanic floors and depending on the
underlying mantle viscosity (Nakada, 1986; Nakada and
Lambeck, 1989). Grossman et al. (1998) noted that the
geophysical model of the rheological response to the last
deglacial melting of the continental ice is in good agreement with the field data, i.e., 1–3 m higher than that present between 5 and 1.5 ka, (for example see Nakada and
Lambeck, 1989; Lambeck and Nakada, 1990 for an Australian example). Variations occur even across continental
shelves and between island groups and there is an absence
of these features in the Caribbean where postglacial
hydroisostatic emergence did not take place.
Magma chamber inflation
In the volcanic island of Tanna (Vanuatu), some corals
uplifted between 155 and 15 m were dated by Chen et al.
(1995) of A.D. 1002 and A.D. 1878, respectively. The
occurrence of such emerged corals at such an elevation
was interpreted by the authors as resulting from the
EMERGED REEFS
377
on Alor Island (Hantoro et al., 1994). In Cape Laundi
(Sumba), Pirazzoli et al. (1991) described the occurrence
of six reef complexes labeled I–VI, reaching an altitude
of 475 m and dated by Electron Spin Resonance and Uranium series methods at 1 million years. The accurate dating of corals from the reef complexes I and II revealed
a polycyclic origin for these terraces with ages from the
MIS 5 (86, 105, 125 ka in the complex I and 130 ka in
the complex II) and MIS 9 (280 and 355 ka in the complex
II). The sequence of raised reefs on Alor Island described
by Hantoro et al. (1994) is composed of six main coral terraces reaching an altitude of 700 m. Uranium series dating
methods provided data to identify the terraces from the
Holocene, MIS 5c, 5e, and 7. Based on the uplift rate of
the dated terraces, an age was calculated for the highest
terraces.
Red Sea
The Red Sea (see Red Sea and Gulf of Aqaba) region is
tectonically active as the Red Sea has been opened by seafloor spreading. In this region, a series of raised terraces
was reported by various authors. In the southern Sinaï,
Gvirtzman et al. (1992) reported the occurrence of several
emerged reefs distributed into several morphological complexes. Gvirtzman (1994) performed a morphological
description of these features and provided U/Th dating
records for some of these terraces. Using these dates
and taking into account the uplift rate, he estimated the
age of other terraces which were not dated. As a result,
ten low and high sea-level stands were identified from
today to 330 ka. In another site in the Red Sea, in the
coastal plain of Egypt, El Moursi et al. (1994) surveyed
a sequence of eight emerged coral terraces including
morphological description and Uranium series dating.
The highest terraces labeled 8 reach an altitude ranging
from 9 to 35 m, the intermediary terraces 5–7 from 22
to 32 m, and the lowest terraces 1–4 from 2 to 9 m.
Because the coral from the highest terraces were
recrystallized, only the lowest terraces 1–3 were dated
from 72 to 131 ka with a large range of intermediary
dates. These dates clearly indicate that these coral reefs
were formed during the last interglacial period (125 ka,
MIS 5). Based on the chronostratigraphy of the sea-level
variations, these authors advanced the hypothesis that
the terraces 5–7 were formed during the MIS 7
(230 ka) and the terrace 8 during the MIS 9 (330 ka).
Lithospheric flexure
Emerged uplifted coral terraces and atolls can provide
proof of the occurrence of lithospheric flexures due to
a bulge at the rear of trenches or due to the loading of
active volcanos in hotspot areas (e.g., Lambeck, 1981).
In the central Pacific, McNutt and Menard (1978)
observed the presence of raised atolls in the Cook and
Society archipelagos in the vicinity of still or recently
active volcanoes resulting from deformation caused by
volcanic loading. They performed a model taking into
account the elevation of these raised atolls which can give
reliable data for the lithospheric flexure. Pirazzoli and
Montaggioni (1998) dated some of the raised corals which
were interpreted as resulting from this lithospheric flexure.
The elevation of coral reefs in the vicinity of New Caledonia in the South-West Pacific provides another example of
lithospheric deformation (Figure 5). The islands of the
Loyalty ridge, from the south to the north, Maré, Lifou,
and Ouvéa are uplifted close to the Vanuatu trench where
the Australian plate dips beneath the Pacific plate and
the North Fiji basin microplate. Only the eastern part
of Ouvéa is uplifted, while the western part is still
submerged. The uplift of the Loyalty Islands and the differences of elevation observed at Ouvéa illustrate particularly well the lithospheric deformation of the bulge
formed just at the rear of the subduction zone (Dubois
et al., 1974, 1988) as also confirmed by the magnetostratigraphy performed on Maré Island (Guyomard et al.,
1996). Another example of lithospheric flexure marked
by raised corals can be found in the Hawaii hotspot area
(Grigg and Jones, 1997). Although the numerical models
agree with the observations, these authors did not exclude
the coexisting presence of tsunami deposits at this site.
Isostatic readjustment
On numerous Indo-Pacific islands and reefs, less prominent emerged features have been described including
abraded reef flats, emerged cemented deposits (beneath
which in situ coral heads may occur), and microatolls
growing at heights above that at which they grow today
(e.g., Dickinson, 2004). A mid to late Holocene age has
been established for these features, which generally show
an emergence of between 1 and 3 m. The occurrence of
this level and its altitude in 92 records from the Pacific
were reviewed by Grossman et al. (1998). These islands
far from the polar regions have been submitted to isostatic
and gravitational readjustments resulting from the meltwater load on the oceanic floors and depending on the
underlying mantle viscosity (Nakada, 1986; Nakada and
Lambeck, 1989). Grossman et al. (1998) noted that the
geophysical model of the rheological response to the last
deglacial melting of the continental ice is in good agreement with the field data, i.e., 1–3 m higher than that present between 5 and 1.5 ka, (for example see Nakada and
Lambeck, 1989; Lambeck and Nakada, 1990 for an Australian example). Variations occur even across continental
shelves and between island groups and there is an absence
of these features in the Caribbean where postglacial
hydroisostatic emergence did not take place.
Magma chamber inflation
In the volcanic island of Tanna (Vanuatu), some corals
uplifted between 155 and 15 m were dated by Chen et al.
(1995) of A.D. 1002 and A.D. 1878, respectively. The
occurrence of such emerged corals at such an elevation
was interpreted by the authors as resulting from the
EMERGED REEFS
377