accommodate the back-stepping of the upper reef
(Blanchon, in press). This jump also created a higherenergy wave field that mobilized back-reef and lagoonal
sediments, creating a high sediment flux which smothered
and eroded lagoonal framework, prevented the recovery
of the submerged reef-crest, and suppressed coral framework in the lagoon (Blanchon et al., 2009).
A jump in SL, that caused reef drowning and backsteeping in the Yucatan reef sequence, can also account
for the lack of reef development above þ3 m in low-lying
areas like the Bahamas and Grand Cayman. This is
because the SL rise rate during the jump was sufficient
to outpace the reef-accretion rate, and submerged
þ3 m reef tracts everywhere. This rapid depth change
induced a higher-energy wave field that not only
remobilized lagoonal sediments and buried or eroded
adjacent reef framework, but led to a switch in sediment
regime by suddenly providing extensive shallow-water
areas for the generation of marine sand bodies. This
increase in sediment flux prevented many of the submerged reefs from recovering after the rise, and led to
a widespread suppression new reef development in lowlying areas. Along narrower, steeper shelves with smaller
sediment reservoirs, a lower sediment flux after the jump
enabled reefs to recover and back-step to new upslope
positions.
Western Australia
Reef-terrace development at þ3 m not only occurs in stable areas of the Caribbean, but has been widely reported
along the coast of Western Australia. In a review of PlioPleistocene deposits, Kendrick et al. (1991) reported intermittent development of a coral-reef terrace for 2,000 km
along this coast, from Cape Range in the north to Cape
Leeuwin in the south. Such extensive reef development
provides an ideal opportunity to identify the controlling
factors on reef development, such as the rate and magnitude of sea-level rise, and to compare those factors with
other LIG reef provinces, such as the Caribbean.
The most northerly report of LIG reef development
occurs at Cape Range, in the Canarvan Basin, where
a fringing-reef forms a narrow coastal terrace running
alongside the modern Ningaloo reef. In some areas, the
terrace extends inland and consists of small patch reefs
and lagoonal sands and gravels (Kendrick et al., 1991).
Several sections in this area were investigated by Stirling
et al. (1998), who reported the
230
Th age of reef framework in the narrow coastal terrace at þ3 m. Two of those
locations yielded several strictly reliable ages: interior
lagoonal patch reefs at þ2 m in Mangrove Bay, gave ages
from 116.1 to 119.2 ka, whereas a þ3 m coastal reef tract
further south at Yardie Creek gave four ages between
119.8 and 121.6 ka with two outliers of 124.6 and
126.8 ka (Figure 4). Drilling on the þ2 m terrace at
Tantabiddi Bay, just north of Mangrove Bay, recovered
framework as deep as 10.3 m below SL, but no characterization of the core was provided (Stirling et al., 1998).
Further inland, along the sheltered coast of the Sandalwood Peninsula, Greenstein et al. (2005) discovered
a marine-erosion surface truncating a þ1.5 m reef terrace.
Some areas of this surface were recolonized by sparse
coral heads, but evidence of subaerial exposure was
absent, making it identical to other marine-erosion surfaces reported from LIG reef deposits elsewhere.
At Cape Cuvier a little further south, O’Leary et al.
(2008a) reported fringing-reef development in a coastal
terrace that sloped inshore from þ3 to þ5 m. Like the terrace to the north, corals on the surface were truncated and
capped with a layer of coralline algae. But unlike elsewhere, this coralline cap extended further upslope to
þ8 m, where it covered the inclined wave-cut surface of
the underlying tertiary eolianite (Figure 4). Above that elevation was a coral-cobble beach gravel. Unfortunately, all
230
Th ages measured from corals in this exposure had isotopic signatures associated with open-system diagenesis,
but they clearly indicate a LIG age for the deposit. At
Shark Bay, 200 km further south, O’Leary et al. (2008b)
also documented reef development in a horizontal coastal
terrace at þ2.5 m. This terrace yielded isotopically reliable
but stratigraphically inconsistent ages between 125.4 and
128.8 ka.
Continuing south into the Perth Basin, several sites
have been investigated around Geraldton, including Burney and Leander Points on the mainland, and particularly
the Houtmann Abrolhos Islands some 60 km offshore
(Figure 4). In the Abrolhos, the reef terrace normally
reaches þ2 to 3 m and, as in other places, is thinly capped
by crustose corallines. This reef framework is then overlain by up to 2 m of skeletal sands and gravels deposited
in shallow subtidal or intertidal conditions. An exception
to this sequence is found on east Wallabi Island at Turtle
Bay, where the top of a domal exposure of reef framework
reached þ4 m and lacked the normal cap of coralline algae
(Zhu et al., 1993). Subsequent drilling and dating of the
Turtle Bay unit by Eisenhauer et al. (1996) gave two reliable surface ages of 124.0 ka and an outlier at 130.2 ka,
and recovered 32 m of branching-coral framework. Drilling was also performed on the þ2 m terrace at Rat and
Roma Islands in the Easter Group of the Abrolhos by
Collins et al. (1993). Both sequences were again dominated by branching corals but showed abundant encrustation by corallines. Only one reliable age of 124.0 ka was
recorded from the surface exposure on Rat Island.
More successful dating of the þ2 to 3 m reef terrace has
been made on the adjacent mainland sections at Burney
and Leander Points (Stirling et al., 1995, 1998). Interestingly, both these sections recorded multiple reliable ages
that were similar to the Abrolhos. At Leander point, corals
from a 1.5 m interval just above sea level recorded six ages
from 121.8 to 124.2 ka with a single outlier of 126.6 ka.
Similarly at Burney Point, four corals from a 1.3 m interval at the top of the terrace recorded ages between 121.7
and 123.5 ka. Clearly, these data convincingly demonstrate that coastal reef terrace in this region had a restricted
interval of development between 124 and 122 ka.
LAST INTERGLACIAL AND REEF DEVELOPMENT
631
(Blanchon, in press). This jump also created a higherenergy wave field that mobilized back-reef and lagoonal
sediments, creating a high sediment flux which smothered
and eroded lagoonal framework, prevented the recovery
of the submerged reef-crest, and suppressed coral framework in the lagoon (Blanchon et al., 2009).
A jump in SL, that caused reef drowning and backsteeping in the Yucatan reef sequence, can also account
for the lack of reef development above þ3 m in low-lying
areas like the Bahamas and Grand Cayman. This is
because the SL rise rate during the jump was sufficient
to outpace the reef-accretion rate, and submerged
þ3 m reef tracts everywhere. This rapid depth change
induced a higher-energy wave field that not only
remobilized lagoonal sediments and buried or eroded
adjacent reef framework, but led to a switch in sediment
regime by suddenly providing extensive shallow-water
areas for the generation of marine sand bodies. This
increase in sediment flux prevented many of the submerged reefs from recovering after the rise, and led to
a widespread suppression new reef development in lowlying areas. Along narrower, steeper shelves with smaller
sediment reservoirs, a lower sediment flux after the jump
enabled reefs to recover and back-step to new upslope
positions.
Western Australia
Reef-terrace development at þ3 m not only occurs in stable areas of the Caribbean, but has been widely reported
along the coast of Western Australia. In a review of PlioPleistocene deposits, Kendrick et al. (1991) reported intermittent development of a coral-reef terrace for 2,000 km
along this coast, from Cape Range in the north to Cape
Leeuwin in the south. Such extensive reef development
provides an ideal opportunity to identify the controlling
factors on reef development, such as the rate and magnitude of sea-level rise, and to compare those factors with
other LIG reef provinces, such as the Caribbean.
The most northerly report of LIG reef development
occurs at Cape Range, in the Canarvan Basin, where
a fringing-reef forms a narrow coastal terrace running
alongside the modern Ningaloo reef. In some areas, the
terrace extends inland and consists of small patch reefs
and lagoonal sands and gravels (Kendrick et al., 1991).
Several sections in this area were investigated by Stirling
et al. (1998), who reported the
230
Th age of reef framework in the narrow coastal terrace at þ3 m. Two of those
locations yielded several strictly reliable ages: interior
lagoonal patch reefs at þ2 m in Mangrove Bay, gave ages
from 116.1 to 119.2 ka, whereas a þ3 m coastal reef tract
further south at Yardie Creek gave four ages between
119.8 and 121.6 ka with two outliers of 124.6 and
126.8 ka (Figure 4). Drilling on the þ2 m terrace at
Tantabiddi Bay, just north of Mangrove Bay, recovered
framework as deep as 10.3 m below SL, but no characterization of the core was provided (Stirling et al., 1998).
Further inland, along the sheltered coast of the Sandalwood Peninsula, Greenstein et al. (2005) discovered
a marine-erosion surface truncating a þ1.5 m reef terrace.
Some areas of this surface were recolonized by sparse
coral heads, but evidence of subaerial exposure was
absent, making it identical to other marine-erosion surfaces reported from LIG reef deposits elsewhere.
At Cape Cuvier a little further south, O’Leary et al.
(2008a) reported fringing-reef development in a coastal
terrace that sloped inshore from þ3 to þ5 m. Like the terrace to the north, corals on the surface were truncated and
capped with a layer of coralline algae. But unlike elsewhere, this coralline cap extended further upslope to
þ8 m, where it covered the inclined wave-cut surface of
the underlying tertiary eolianite (Figure 4). Above that elevation was a coral-cobble beach gravel. Unfortunately, all
230
Th ages measured from corals in this exposure had isotopic signatures associated with open-system diagenesis,
but they clearly indicate a LIG age for the deposit. At
Shark Bay, 200 km further south, O’Leary et al. (2008b)
also documented reef development in a horizontal coastal
terrace at þ2.5 m. This terrace yielded isotopically reliable
but stratigraphically inconsistent ages between 125.4 and
128.8 ka.
Continuing south into the Perth Basin, several sites
have been investigated around Geraldton, including Burney and Leander Points on the mainland, and particularly
the Houtmann Abrolhos Islands some 60 km offshore
(Figure 4). In the Abrolhos, the reef terrace normally
reaches þ2 to 3 m and, as in other places, is thinly capped
by crustose corallines. This reef framework is then overlain by up to 2 m of skeletal sands and gravels deposited
in shallow subtidal or intertidal conditions. An exception
to this sequence is found on east Wallabi Island at Turtle
Bay, where the top of a domal exposure of reef framework
reached þ4 m and lacked the normal cap of coralline algae
(Zhu et al., 1993). Subsequent drilling and dating of the
Turtle Bay unit by Eisenhauer et al. (1996) gave two reliable surface ages of 124.0 ka and an outlier at 130.2 ka,
and recovered 32 m of branching-coral framework. Drilling was also performed on the þ2 m terrace at Rat and
Roma Islands in the Easter Group of the Abrolhos by
Collins et al. (1993). Both sequences were again dominated by branching corals but showed abundant encrustation by corallines. Only one reliable age of 124.0 ka was
recorded from the surface exposure on Rat Island.
More successful dating of the þ2 to 3 m reef terrace has
been made on the adjacent mainland sections at Burney
and Leander Points (Stirling et al., 1995, 1998). Interestingly, both these sections recorded multiple reliable ages
that were similar to the Abrolhos. At Leander point, corals
from a 1.5 m interval just above sea level recorded six ages
from 121.8 to 124.2 ka with a single outlier of 126.6 ka.
Similarly at Burney Point, four corals from a 1.3 m interval at the top of the terrace recorded ages between 121.7
and 123.5 ka. Clearly, these data convincingly demonstrate that coastal reef terrace in this region had a restricted
interval of development between 124 and 122 ka.
LAST INTERGLACIAL AND REEF DEVELOPMENT
631