Quaternary atoll development: new insights from the 2-D

stratigraphic forward modelling of Mururoa Island

(Central Pacific Ocean).

LUCIEN F. MONTAGGIONI1, JEAN BORGOMANO2, FRANÇOIS

FOURNIER1 and DIDIER GRANJEON3

1 CEREGE, UMR 36, Aix-Marseille Université, Centre Saint-Charles,

3 Place Victor Hugo, F-13331, Marseille Cedex 03, France (Elail:

montaggioni@cerege.fr)

2 TOTAL CSTJF, EP, Avenue Laribeau, F-64018 Pau, France

3 IFP Energies nouvelles, 1 avenue de Bois-Preau, 92852 Rueil-

Malmaison Cedex, France

short title: stratigraphic modelling of Mururuoa Atoll development

ABSTRACT

1

The knowledge on the Quaternary evolution of mid-ocean atolls

comes mainly from drilling and field observations carried out on a

number of Pacific carbonate islands. However, little is known

about the early to mid Pleistocene atoll development history,

especially, at margin and foreslope settings. Using previous field

and subsurface data from Mururoa Atoll and a process-based

modelling software (DIONISOS), a 2-D forward stratigraphic model

of atoll development is proposed for the past 1.8 million years

(Ma). Observational data from vertical to inclined coring, seismic

and bathymetric surveys indicate that, from approximately 0.40

Ma, carbonate deposition at Mururoa Atoll has dominantly resulted

in a series of mostly prograding reef units. The model is first

constrained at the base by the shape and topography of the pre-

Quaternary basement. A number of sensitivity tests were performed

to define the respective influence of variant parameters. The

best-fit development scenario that accounts for the overall

geometry and architecture of the Quaternary sediment packages is

obtained by using the sea-level curve by Miller et al. (2005), an

uniform subsidence rate of 105 m/Ma, and carbonate production

rates of 0.50 to 0.80 mm/year, 0.80 to 2.5 mm/year and 2.50

2

mm/year during the intervals 1.80-1.0 Ma, 1.0-0.80 Ma and 0.50 Ma-

present respectively. Unvariant parameters include subaerial

erosion (at a rate of 0.25 m/1,000 years) and sediment-transport

processes. The stratigraphic forward model predicts a succession

of three distinct types of carbonate systems since the earliest

Pleistocene: toe-of-slope systems from 1.80 Ma to about 0.80 Ma,

ramp-like systems from 0.80 Ma to 0.50 Ma, and reef systems from

about 0.50 Ma to the present. The development of these different

systems is most likely controlled by climate variability,

especially changes in sea-level cycles. During the low-amplitude

41-ka cycle periods of the earliest Pleistocene, shallow-water

carbonate sedimentation has been dominantly gravity-driven,

operating along the platform foreslopes only. During the Mid-

Pleistocene Climate Transition, ramp-like units have developed at

the platform top. With the installation of the high-amplitude 100-

ka sea-level modes and climate restoration, reef frameworks

started to be generated. Climate variability seems to have played

a prominent role in controlling the development of carbonate

worldwide. The results from Mururoa agree with the contention that

most of the true framework reefs throughout the tropics were not

3

initiated prior to 0.50 Ma. Mururoa Atoll is demonstrated to be a

robust analog for providing more realistic interpretations of the

development history of Pacific atolls. Further modelling with

DIONISOS could generate better predictions by taking into account

hydrodynamic and transport parameters.

Keywords: coral reef growth, atoll, Quaternary, stratigraphic

modelling, sea level, subsidence, carbonate production.

INTRODUCTION

Geomorphologically speaking, atolls are mid-ocean, ring-shaped

coral reef islands, enclosing a central lagoon. Their surface

morphology is typified by three main features: the outer forereef,

the reef rim and the lagoon (See Woodroffe and Biribo, 2011 for a

comprehensive discussion on the definition of the term “atoll”).

The scientific characterization of atoll probably started with

the description of Charles Lyell (1832). Lyell interpreted atolls

as coral veneers overtopping the edge of submerged volcanoes.

Darwin (1842) was the first to propose an alternative

theory, known as« the subsidence-control theory». Atolls would

4

have resulted from the progressive conversion of fringing reefs

and subsequent barrier reefs through vertical reef growth to sea

level in response to the continuous subsidence of the underlying

volcanic foundations. Daly (1910) contested Darwin’s hypothesis

and proposed the so-called « glacial control theory ». This

suggests that atolls have developed through a number of sea-level

changes that have promoted marine planation of the former reef

bodies during Pleistocene glacial, low sea-level time-intervals.

A broader view was taken by Kuenen (1933) and Stearns (1946), and

more fully developed by Kuenen (1947). Where Daly had advocated

marine abrasion as the modifying mechanism, Kuenen by contrast

relied on the faster rates of intertidal and subaerial

dissolution to achieve the required result (see reviews by

Stoddart, 1969; Steers and Stoddart, 1977; Hopley, 1982; Purdy

and Winterer, 2001; Montaggioni and Braithwaite, 2009 ;

Woodroffe and Biribi, 2011).

From late in the 19th century and early in the 20th, atolls,

especially in the Pacific, became a focus of research. In 1896-

1898, the Royal Society of London together with Australian

geologists began deep drilling on Funafuti Atoll in search of reef

5

foundations (David and Sweet, 1904). Deep coring through atolls

subsequently took place on Kita-Daito-Jima Atoll (Ota, 1938), in

the Marshall islands (Ladd et al., 1953 ; Emery et al., 1954; Ladd

and Schlanger, 1960), on Midway Atoll (Ladd et al., 1967, 1970)

and on Mururoa Atoll (Deneufbourg, 1969; Repellin, 1975). These

works broadly supported Darwin’s theory but also restated Daly’s

theory in terms of karstic processes. The antecedent karst theory

supposes that there is no evolutionary development of atolls from

fringing and barrier reefs, but ascribes the origin of atoll

lagoons to differential subaerial solution by rainwater during

glacial, low sea stands (Purdy, 1974 ; Purdy and Winterer, 2001).

Over the last 3 decades, a significant body of new information

about Quaternary stratigraphy and development history in relation

to sea-level fluctuations has been gained from a number of atolls

and atoll-shaped, high carbonate islands worldwide. The data come

from three types of sources: (1) shallower to deep (>100 m)

drilling of low-lying atolls, (2) ocean drilling of submerged

atolls and (3) field observations of atoll-shaped, high carbonate

islands. Some data obtained from previous deep atoll drilling were

6

recently revisited, while additional drilling investigations were

conducted in a number of atoll sites (Table 1).

Apart from the Post-glacial development patterns of reef

rim/lagoon sections (see Montaggioni, 2005; Montaggioni and

Braithwaite, 2009, chapter 6; Woodroffe and Biribo, 2011; for

reviews), these studies have provided valuable information on some

aspects of Pleistocene stratigraphy and geometry of atolls.

Uranium series dating, but also strontium isotope measurements,

magnetostratigraphy and Electron Spin Resonance (ESR), have been

successfully applied in some areas and more recently, amino acid

racemization stratigraphy to the problem of dating Pleistocene

carbonate units in the cores and/or outcrops from atolls (See

Montaggioni and Braithwaite, 2009, p. 14-19, for review). In light

of geochronological analyses combined with detailed examination of

internal structure and bio-lithology and available seismic

records, the major features typifying the history of atoll can be

summarized as follows:

(1)The present-day relief of both atolls and atoll-like carbonate

islands is solution-inherited, reflecting the strong impact of

karstification on the topography expression ; the depth of the

7

central basins (“empty bucket” in the sense of Purdy and Gischler,

2005) is regarded as controlled by the combined influence of

paleo-rainfall rates and freshwater catchment area during

Pleistocene or earlier low-sea stands. Some lines of evidence

indicate that most mid-ocean shallow-water carbonate piles have

occurred in the form of flat-topped banks at sea level prior to

experience emergence and subaerial solution.

(2)Pleistocene shallow-water carbonate sequences beneath the

present-day atoll tops range from about 50 m to up to 200 m thick

(around 390 m thick at Bougaiville Guyot). This mainly reflects

differential depositional and erosion rates during

interglacial/glacial cycles from atoll to atoll in response to

differential tectonic behaviour. A number of marine istotope

stages (MIS), related to high and low sea stands as well, are not

recorded at most drilling or outcropping atoll sites.

(3)The shallow-water carbonate sequences are composed of a series

of superimposed units bounded at top by unconformities displaying

intensive dissolution, karst and paleosoil features. These

surfaces reflect periodic emergence and subaerial erosion during

sea-level low stands.

8

(4)In a number of atolls, the outer margin may have developed

seawards in the form of stacked fringing-like reef bodies,

recording high sea-levels and, in some areas, low sea-levels from

MIS 11 (0.40 million years) backwards to the present.

However, while the depositional history beneath lagoon areas is

relatively well documented, little is known about the development

patterns of atoll margins and flanks during the mid to early

Quaternary. Gaining data from the outermost parts of atoll margins

requires the use of obliquely seaward-oriented drillholes. The

lack of knowledge on atoll margins and flanks is therefore due to

the scarcity of such oblique cores extracted from atoll fronts.

Furthermore, oblique coring has proven to be unable to access the

deepest parts of atoll flanks (Buigues, 1997; Camoin et al.,

2001).

As a consequence, one way to achieve a general scheme of atoll

evolution and growth architecture over the Quaternary is to

perform stratigraphic forward modelling based on available field

observations and drilling records. During the last 15 years, an

increasing number of studies have been made to provide realistic

reconstructions of the internal structure and stratigraphy of

9

reefs and carbonate platforms and to quantify the major processes

that control reef growth on various spatial and temporal scales

(see Dalmasso et al., 2001 ; Montaggioni and Braithwaite, 2009, p.

262-269, for reviews). Among others, Bosscher and Southam (1992),

Warrlich et al. (2002), Matsuda et al. (2004), Webster et al.

(2007), Hill et al. (2009), Koelling et al. (2009), Schlager and

Warrlich (2009), Barrett and Webster, (2012), Seard et al. (2013)

and Toomey et al. (2013) applied stratigraphic forward modelling

to predict the evolution and/or reconstruct the internal

structure of different reef morphotypes over time scales ranging

from a few millennia to tens of thousands of years. In particular,

computer simulations of drowning processes of atolls have been

provided by Warrlich et al. (2002). The respective role of local,

regional and global factors in driving the geometry and

stratigraphy of carbonate deposits can be tested and estimated.

Herein, the software DIONISOS developed by the Institut Français

du Pétrole Enérgies Nouvelles (IFPEN, Paris) (Granjeon, 1997;

Granjeon and Joseph, 1999) was used to identify and quantify the

dominant parameters that could have governed the development and

anatomy of atolls, especially, those of undrilled sections, i.e.

10

atoll margins and flanks. Mururoa island, a typical mid-ocean

atoll in the south central Pacific, is an unique object for

investigating overall atoll evolution over the Quaternary, given

the abundance of observations and measurements on the surface and

outer-flank morphology (Buigues et al., 1992 ; Guille et al.,

1999), reef zonation (Chevalier et al., 1968 ; Bablet et al.,

1995), water properties and circulation (Leclerc et al., 1999;

Tartinville et al., 1997; Tartinville and Rancher, 2000) and the

most comprehensive suite of cores through an atoll constraining

the internal structure and stratigraphy (Buigues et al., 1992;

Buigues, 1998 ; Perrin, 1990 ; Camoin et al., 2001).

The aims of this study are to: 1) compare the architectural

attributes of the upper forereef parts derived from oblique

drilling investigations with the realizations obtained from the

forward modelling; 2) test the different parameters that could

have controlled the atoll development over the Quaternary

(conventionally, the last 1.8 million years); 3) to estimate the

influence of these parameters on the 2-D geometry and stratigraphy

of depositional bodies within the margin and along the outer flaks

11

of the atoll; and 4) test the capacity of DIONISOS to model such

atoll stratigraphies.

STUDY SITE

Location, modern morphology and environmental setting

The atoll of Mururoa, also known as “Moruroa”, lies in the

south central Pacific Ocean (21°50’S, 138°53’W). From a geographic

point of view, it belongs to the Tuamotu archipelago (French

Polynesia). Mururoa is an open atoll, with an irregular

elliptical shape, 28 km long and 11 km wide, and a total surface

area of nearly 155 km2 (Figure 1).

The modern atoll morphology and reef zonation have been

described by Chevalier et al. (1969), Bablet et al. (1995) and

summarized by Camoin et al. (2001) and Montaggioni (2011). The

outer reef rim forms a continuous ribbon, averaging 400 m wide

along the northeast to southeast sides and a discontinuous line,

1,300 m on maximum width, composed of successive islets (usually

12

called “motu”) separated by channels (“hoa”) along the south side.

In the north and northeast parts, the width of the reef flat

locally does not exceed 150 m. On the southwest part, the atoll-

rim surface is submerged, allowing the oceanic swell to directly

enter the lagoon. The lagoon is semi-enclosed, 135 km2 in surface

area and ranges between 28 and 52 m in depth (mean depth: 33 m).

It is connected to the open ocean through a 5-km wide and 9-m deep

pass located on the western side (Figure 1).

Bathymetric surveys carried out along the atoll foreslope off

drilling sites have allowed three sub-zones to be distinguished on

the basis of topographical attributes (Chevalier et al., 1969;

Bablet et al., 1995). The upper subzone, from reef top to around

20-25 m deep, is gently dipping (l0°-30°). From 25 to 100 m deep,

the intermediate subzone becomes increasingly steeper (40-45°) and

forms a sub-vertical (60-65 °) drop-off to 200 m deep (Figure 2).

The lower atoll flanks tend to progressively slope gently down

(less than 30 ° on average) from 250 m to the surrounding basin.

Submarine terraces have been observed at 10, 20, 40, 55 and 65 m,

together with cave-like features at 80, 90 100 and 150 m below

present sea level.

13

The climate and oceanographic conditions in the Tuamotu Islands

and at Moorea have been summarized by Rancher and Rougerie (1994)

and Bablet et al. (1995). All these islands are surrounded by the

South Equatorial Current, a global westward drift at a speed of 10

cm/s. In the south central Pacific, the average thermohaline field

forms a two-layered system: (1) the South Tropical Water, a warm

surface mixing layer (0-150 m) with a high salinity core (>36.3

PSU); (2) the Antarctic Intermediate Water with a salinity minimum

(34.5 PSU). These two layers are separated by a permanent

pycnocline. Between 12 and 30°S, the surface mixing layer is

nutrient-depleted, resulting in strong oligotrophy and clarity of

waters surrounding the Tuamotu region.

At Moorea, the climate is warm and humid, with a strong

seasonal variability. Annual air temperatures are around 25 °C and

precipitation rates are 1,350 mm on average. During the austral

winter, from May to October, since Mururoa atoll is subjected to

the direct influence of the South Pacific Convergence Zone, i.e. a

band of low-level convergence, cloudiness and rainfall, monthly

rainfall does not exceed 70 mm and air temperatures vary from 20

to 25°C . During the austral summer, from November to the end of

14

April, monthly rainfall is about 150 mm and air temperatures vary

between 25° and 29°C. Mean moisture content ranges from 80 to 85 %

in December and January, whereas it averages 75% during August.

The surface temperatures of oceanic waters vary from 22.5°C to

25.5°C, while lagoonal waters can reach 29°C during the summer.

By contrast, salinity in both the lagoon and nearby ocean waters

is pretty similar, with values of 36.00 PSU; locally, maximum

values of 36.5 PSU can be recorded. Tides are semi-diurnal, with

0.30 to 0.70 m in amplitude. During spring tides, maximum

amplitudes reach 1.20 m. The tidal currents entering through the

western pass was shown to weakly influence the circulation in the

lagoon (Tartinville et al., 1997).

The dominant wind regime affecting Mururoa atoll for about 8-9

months of the year is the southeast trade-winds at speeds

averaging 6 to 10 m/s. The resulting swells are typified by waves

less than 3 m in height and 7s in period. As a result, the most

vigorous reefs are growing in areas open to the swell generated

by the dominant SE trade-winds. The trade-wind swells cannot enter

the pass on the west side of the atoll. The intralagoonal

circulation is a fetch-driven wave field with a short, mean period

15

of less than 4 s and a height of less than 0.75 m. The cross-reef

currents are known to vary seasonally (Tartinville and Rancher,

2000). Episodically, the atoll is impacted by two other types of

swells coming from the west sectors; during the winter, antarctic

polar depressions generate a southwest swell characterized by

waves with long period (>12 to 20 s) and 3-4 m in height, while

during the summer, northwest swells (wave height: 2.5-6 m; period:

7-10 s) result from storms (wind speed: 25 m/s) operating from the

high latitudes of the north hemisphere. During the west-wind

regimes, ocean waters flow into the lagoon through the pass in the

form of wave fields with varying height (<0.5 to 1.5 m) and period

(4 to 20 s).

Wind stress is shown to be the dominant forcing for the long-

term circulation and for the turnover of the lagoonal water

masses. Based on a three-dimensional model, the residence time of

waters in the lagoon, i.e. the period of time required for a water

parcel initially located at a given point in the lagoon to leave

through the pass and enter the ocean, has been estimated to be

about 100 days (Tartinville et al., 1997). The topography of the

lagoon is likely to play an important role in the circulation

16

pattern. Simulations performed by Mathieu et al. (2002) revealed a

two-cell circulation pattern, with a down-wind current in the

shallower parts close to the outer rim, and a returning up-wind

current in the deeper, central parts.

The Tuamotus belong to a low-frequency cyclonic zone. Mururoa

is likely to experience cyclone only every ten to twenty years on

average. Cyclone-induced swells usually come from northwest

sectors with wave height of 12 m and periods of 13 s

approximately.

Measurements of temperature within the atoll carbonate pile

have been performed from a number of drillholes (Guille et al.,

1995) . While in ocean waters, there is a rapid decrease from the

surface (about 25 °C) down to 250 m (about 18°C) and 450 m (about

10°C), beneath the atoll rim temperatures remain around 20°C and

16 °C at depths of 250 and 450 m respectively.

Origin and internal structure

From a geodynamic point of view, Mururoa is part of the

Pitcairn-Duke of Gloucester volcanic island chain. The origin of

17

the island chain has been attributed to the activity of a hot spot

zone at present operating at about 70-100 km southeast of Pitcairn

Island (Duncan et al., 1974). However, the presence of a submarine

plateau beneath Mururoa, located closely and oriented similarly to

the WSW-ENE trending Austral Fracture Zone, suggests that the

island basement may be partly resulting from fissural volcanism

along this fault system (Bardintzeff et al., 1986). The age of the

underlying oceanic crust beneath Mururoa is 35 million years (Ma)

(Dupuy et al., 1993). The cessation of subaerial volcanic activity

has occurred at around 11-10.5 Ma (Gillot et al., 1992).

From the beginning of the seventies, intensive geological,

geophysical and paleobiological investigations have been conducted

on the carbonate pile of the atoll, using deep drilling (Repellin,

1975; Buigues, 1985, 1997, 1998; Aissaoui et al., 1990; Perrin,

1990; Ebren, 1996; Camoin et al., 2001; Braithwaite and Camoin,

2011). The carbonate deposits occur between 300-570 m and 120-220

m beneath the reef rim and the center of the lagoon respectively

(Figure 2). Shallow-water carbonate deposition is likely to have

started in the form of fringing and barrier reefs early in the

Miocene, but to have been discontinuous throughout, as a result of

18

intensive volcanic activity and sea-level changes. An extensive

flat-topped carbonate platform is interpreted to have capped the

entire volcanic basement probably during the Pliocene. The

classical atoll morphology, i.e. saucer-shaped, has been acquired

not prior to the late Pliocene, in relation to intensive karstic

solution. This is evidenced by the occurrence of numerous seismic

reflectors identified in the carbonate pile and interpreted as

resulting from fresh-water diagenetic overprint below subaerial

exposure surfaces (Buigues, 1982).

Quaternary development and stratigraphy of the carbonate pile:

current knowledge.

Based on vertical drilling results, magnetostratigraphy and U-

series age dating, the total thickness of the Quaternary deposits

appear to range from 55 to 63 m beneath the present-day atoll

surface at reef-rim sites and from 35 to 45 m at lagoon sites.

The uppermost reef unit of Holocene age varies between about 3-11

m and 10-20 m thick beneath the reef rim and the lagoon

respectively. The entire Pleistocene reef sequence is about 60 m

19

in maximum thickness. This sequence is punctuated by 5 major

unconformity surfaces at 3-7 m, 18-22 m, 29-32 m, 36-40 m, and 48-

49 m below the present reef surface. These unconformities are

interpreted as related to exposure events separating successive

reef generations. The Pliocene-Pleistocene boundary forms a well-

differentiated unconformity surface at maximum depths of 63 to

about 85 m below present sea surface (Figure 2). Age-depth

relationships in cores suggested that the lowermost Pleistocene

reef unit identified at about 47-63 m deep is not older than 0.70

Ma (Aissaoui et al., 1990).

A significantly different picture of the distribution and

stratigraphy of the successive reef units has been obtained from

the atoll margin owing to seaward-deviated drillholes that have

penetrated the northeast edge of the atoll (Aissaoui et al., 1986;

Perrin, 1989; Ebren, 1996; Camoin et al., 2001). It appears that

the upper part of the outer reef margin has developed as a series

of fringing reefs dominated by progradation with minor

aggradation (Figure 2).

Based on four cores with high-recovery, 300 m long, 30° to

45°-inclined, and a large number of U/Th dates, Camoin et al.

20

(2001) tentatively reconstructed the successive development stages

of the atoll flanks from about 0.45 Ma backwards to the present,

and constrained sea-level fluctuations over the last 0.30 Ma. The

four uppermost units, prominently composed of coralgal

boundstones, have deposited during four episodes of high sea

levels, successively deposition of (1) a Holocene (MIS 1) unit, 9

m in vertical thickness, not older than 8 ka, (2) a 16 to 19 m-

thick unit related to MIS 5.5 (about 125 ka), (3) a 27 to 30 m-

thick unit attributed to MIS 7 (212 to 227 ka), and (4) a 30 to

40 m-thick unit related to MIS 9 (about 312 to 355 ka). Three

additional rock samples have been dated between 400 and 500 ka

at vertical depths of 69, 167 and 138 m, thus suggesting shallow-

water carbonate deposition between MIS 11 and 13. The lowermost

units, mainly composed of detrital material with subordinate

coralgal boundstones, occur at depths of 81 to 169 m below present

sea level. The unit attributed to MIS 2 (about 17 to 23 ka) form

a coralgal framework of about 30 m in vertical thickness that caps

the modern outer flanks. MIS 4 is represented by a 36 m-thick

deposit ranging from 59 to 69 ka in age. The unit related to MIS 8

is composed of about 23 m-thick skeletal accumulations dated at

21

around 270 to 295 ka. There is no direct record of MIS 6 in

cores. The corresponding unit is interpreted as deposited between

120 and 160 m below present sea level (Braithwaite and Camoin,

2011). Similarly, the MIS 3-unit has not been penetrated, but it

is likely to form the core of the intermediate foreslope between

about 25 and 100 m below sea surface. In addition, in the deviated

coreset, various karstified unconformities have been recognized at

depths of about 10, 30, 45, 65, 80, 90 and 110 m below present sea

level; those occur at top of units, tentatively attributed to MIS

5, MIS 7.3, MIS 7.5, MIS 9, MIS 11, MIS 13 and MIS 8 (Ebren,

1996).

METHODS AND INPUT DATA

Stratigraphic forward model

The realizations obtained with the stratigraphic forward model

“DIONISOS”, implemented by the IFPEN (Granjeon and Joseph, 1999).

Initially, this software was designed to investigate the primary

22

mechanisms controlling the development of both carbonate and

siliciclastic sedimentary systems at basin scale (10-100 km

dimensions) over time ranges of 100 Ma to 100 ka (comparable to

so-called 1st- to 4th-order sea-level fluctuations) (Granjeon and

Joseph, 1999; Rabineau et al., 2005; Granjeon et al., 2005;

Burgess et al., 2006). The software was later applicable to modern

carbonate environments, such as Holocene reefs (Seard et al.,

2013), allowing reconstructions of carbonate architectures over

shorter time intervals (similar to so-called 5th to 6th-order sea-

level fluctuations) and smaller spatial scales. In the present

paper, DIONISOS is intended to model the impact of internal

(carbonate production rates, sediment transport) and external

(sea-level changes, subsidence rate, subaerial erosion) forcing

factors on the development and stratigraphy of the atoll over the

past 1.8 Ma. The selected processes and estimations of their

parameters are based on recent reefs and associated depositional

settings in the Pacific (Kleypas, 1997; Kleypas et al., 1999;

Dullo, 2005; Montaggioni, 2005; Montaggioni and Braithwaite,

2009). The complex interplay between the main driving factors is

explored, while a variety of other processes thought to be

23

subordinate or confounding (rainfall rates, calcification rates,

bioerosion, carbonate diagenesis) are not taken into account in

the simulation.

The basic constrains of the model are the morphometric

attributes provided by previous geological surveys, including

present-day atoll morphology and stratigraphy (Table 2), together

with seven categories of parameters used as principal inputs: pre-

Quaternary basement topography, sea-level curve corrected for

subsidence (i.e. accommodation space), carbonate production,

sediment transport and subaerial erosion (Table 3).

Basement topography

The physiography, depth and slope of the antecedent topography

are known to influence significantly shallow-water carbonate

deposition (Daly, 1915; Hoffmeister and Ladd, 1944; Purdy, 1974).

In Mururoa, the basic attributes of the pre-Quaternary substratum

upon which the Pleistocene carbonates have deposited were

estimated from extensive drilling and seismic refraction surveys

(Buigues, 1982; Perrin, 1989; Ebren, 1996), combined to

24

chronostratigraphic analyses (Aissaoui et al., 1990; Buigues,

1997; Camoin et al., 2001). The Mio-Pliocene basement was clearly

identified at depths ranging from 55 to 63 m below the reef-rim

top. By contrast, its location below the lagoon floor remains

uncertain because of low recovery rate in the uppermost core

portions. Based on a limited number of radiometric dates, the

location of the Mio-Pliocene basement within cores Lagon 1-2,

Janie and Nerite is suggested to occur at depths of 25 to 30 m

beneath the lagoon floor (65 to 90 m below present sea level).

Variations in the stratigraphic position of the

Pliocene/Pleistocene unconformity can be partly explained by

irregular karstification. One remaining difficulty is the

definition of the geometry of the Pliocene talus within the atoll

margin. Because no seaward-inclined drillhole has penetrated the

antecedent foundation at the margin setting, establishing the

initial basement topography implies to assume that the Pliocene

talus and the modern slopes have the same angle down to 300 m

water depth at least. This assumption is supported by field

observations carried out on uplifted atoll-shaped high carbonate

islands, clearly indicating the general occurrence of steeply

25

dipping flanks around the pre-Quaternary island margins

(Montaggioni, 1985; Montaggioni et al., 1987; Stoddart et al.,

1990; Pandolfi, 1995; Suzuki et al., 2007). Beneath the lagoon

floor and the reef-flat zone, the surface of the Pliocene pile is

assumed to mimic that of the modern atoll, resulting in a “bucket”

shape morphology, while, within the outer margin, vertically below

the reef front line, the Pliocene surface tends to sharply dip

seawards. Several values of slope angles were tested iteratively

during the preliminary modelling phases to estimate the most

realistic Pliocene basement topography (Figure 2). The slope angle

varies from 40 ° between 80 and 200 m to 50° between 200 and 300 m

deep relative to present sea level. Despite the experimental

origin of this surface, it represents the most compatible slope

with the spatial distribution of the oldest Pleistocene carbonate

bodies identified within the Mururoa margin.

Accommodation space

26

Theoretically, accommodation space is the volume available for

sediment to accumulate, and primarily depends upon eustatic sea-

level change and subsidence. The upper limit of the space is the

position of eustatic sea level at a given time; the lower limit is

the initial basement surface. Moreover, it is noteworthy that the

respective boundaries of the sediment pile that have accumulated

over the past 1.80 Ma are the top Pliocene surface at the base of

the model and the modern atoll topography at the top. These two

boundaries provide a drastic geometrical constraint on the model

envelopes (Figure 2).

In the model, estimates of the changes in global eustatic sea

level over the past 1.80 Ma were based on the most comprehensive

benthic ∂18 O-based sea-level curve published so far (Miller et

al., 2005). The record is broadly consistent with the coral-based

sea-level data, at least for the last 0.40 Ma (Siddall et al.,

2006). The input includes initial sea-level position, and

sinusoidal frequency and amplitude. In the earliest tests, the

midpoint of each odd (high stand) and even (low stand) stage was

used as a time baseline from MIS 1 (Holocene) back to MIS 63

(approximately, 1.80 Ma). This has permitted to assess the best

27

time-slice duration to be taken into account for getting the most

consistent and readily understandable scheme of sediment

deposition at a given time interval (Table 2). It has been found

that time steps had to vary in duration through time to balance

computer time and model accuracy. In addition, to keep the modern,

>150 m-deep foreslope topography as a constant constraint for the

model, it was necessary to prescribe low rates (<0.80 mm/yr) of

carbonate deposition. Grouping MIS 63 to 28 and MIS 27 to 14

respectively into single time steps allowed to rapidly provide a

robust depositional pattern of the lower foreslope between 1.80

and 0.50 Ma. From 0.50 Ma to present, the successive time steps

vary from 30 to 60 ka as necessary (Table 2).

As a mid-plate oceanic island, Mururoa atoll is considered to

have undergone a long-term thermal subsidence, primarily resulting

from the cooling and thickening of the underlying oceanic crust

(Detrick and Crough, 1978). It was assumed that the amount of

thermal subsidence of such atolls can be approximated from an

empirical age-depth relationship, based on the age of the

underlying volcano and the age of the adjacent lithospheric floor

(Parsons and Sclater, 1977; Crosby et al., 2006). Applied to

28

Mururoa, the plate cooling model indicates that the underlying

volcanic shield, which sits on 35 Ma old crust and is inactive

since the last 10.5-11 Ma, may have drowned since by 250-300 m, at

a subsidence rate averaging 25 m/Ma. Subsidence calculated from

the depth occurrence and radiometric dating of the subaerial

basaltic bed-rock (Trichet et al., 1984), the present-day position

of the Miocene/Pliocene unconformity (Paulay and McEdward, 1990),

reef accumulation rates (Aissaoui et al., 1990) or the present-day

position of the Last interglacial reef unit (MIS 5.5) within the

atoll rim (Camoin et al., 2001) is found to be remarkably faster

than that predicted by thermal effects. According to these

calculations, the atoll would have subsided at rates ranging from

40 to 125 m/Ma.

The discrepancies between rates expected from the plate-

cooling model and those from the development history of the island

could be partly explained by the fact that atoll subsidence

incorporates additional components, i.e. isostatic response to

sediment and water loading and compaction. The loading due to 450-

m thick carbonate deposits is likely to have accelerated the

drowning of the underlying volcano. By contrast, as a result of

29

their margin narrowness, atolls are weakly amenable to

deformation triggered by water loading during events of sea-level

rise (Wheeler and Aharon, 1991) while considerable compaction may

occur through pressure solution and dolomitization of the

carbonate cap (Anderson and Franseen, 1991). Since the respective

role of each component is unknown, it is assumed that subsidence

has operated at a constant rate over the past 1.80 Ma. An

accommodation curve was constructed from the eustatic sea-level

curve corrected for subsidence (Figure 3).

Carbonate production

Gross carbonate production is known to vary greatly between reef

sites, within different reef environments and between the various

zones of a single reef system. It depends on an array of factors,

including the type of substrate, food supply, temperature,

salinity, water depth and water energy, and, as a result, coverage

and growth rates of reef builders (Dullo, 2005; Montaggioni, 2005;

Hopley et al., 2007, 372-403; Montaggioni and Braithwaite, 2009,

30

p. 172-183, for reviews). Production is generally the highest

within the upper few metres of the water column and tends to

decrease exponentially with depth as a function of light intensity

(Bosscher and Schlager, 1992). Consequently, water clarity through

promotion of light penetration appears to be one of the major

controlling factors of the growth-depth patterns of corals

(Kleypas et al., 1999). Unfortunately, no direct measurement of

water clarity is available from the surrounding waters of Mururoa

atoll. However, clarity status can be assessed from levels of

total chlorophyll “a” and nutrients in the water column. The south

central Pacific waters surrounding the Tuamotu Islands are

documented to be strongly depleted in chlorophyll “a” and

dissolved mineral nitrogen, phosphorus and silica (Dandonneau,

1979; Dufour et al., 1999 a). The open ocean waters close to

Mururoa contain 0.08 gL-1 chlorophyll “a” on average.

Concentrations in NO-2, NO-

3, PO++4 , SiO3 approximate 0.050, 0.25,

0.30 and 1.0 M respectively (Rougerie et al., 1980; Bablet et

al., 1995). Such concentrations preclude significant plankton

development (Dufour et al., 1999 b), thus resulting in high water

clarity around the atoll.

31

High water clarity in the considered oceanic area is testified

by the distributional patterns of coral communities at Mururoa and

the nearby atoll of Fangataufa.The reef crest and the upper parts

of the forereef slopes on both atolls exhibit coral assemblages

dominated by robust branching Acropora group humilis, A. gr. palifera and A.

gr. selago (A. tenuis), together with Millepora platyphylla, at both windward

and leeward settings down to about 15 m deep (Bablet et al., 1995;

Camoin et al., 2001), while these forms are asserted to

prominently grow at reef-flat settings and uppermost parts of

outer reef slopes (Wallace, 1999; Veron, 2000) within depth

intervals rarely greater than 5-6 m in most Pacific reef sites

(Montaggioni, 2005). Similarly, Acropora nasuta, which is frequent

between 15 and about 40 m on the outer slopes of Mururoa and

Fangataufa atolls, generally occurs at the depth range of 6 to 12

m, occasionally to 20 m on the Great Barrier Reef (Done, 1982). In

addition, some forms of pocilloporids, usually restricted to

shallow-water settings or to high-energy reef fronts at depths not

exceeding a few metres, are observed to depths ranging from 10 m

(as Pocillopora verrucosa) to 20 m (as Pocillopora meandrina), or colonize

the atoll slopes between 18 and 38 m deep (as Pocillopora elegans). One

32

of the most abundant coral species along the intermediate forereef

zone is the foliaceous Montipora aequituberculata which is found

between 30 and 38 m deep at Mururoa and Fangataufa, while, in most

Pacific reef sites, it occupies sheltered reef slopes at depths

lower than 15 m. These observations are in line with those by Vijn

and Bosscher (in Schlager, 2005). These authors pointed out that

the active reef-growth depth-range averages 50 m on the Great

Barrier Reef, is less than 50 m at Tahiti, but can extent to

depths greater than 80 m in Pacific atolls.

Accordingly, based on the species composition and distribution

of coral communities, the highest potential coral growth rates are

regarded as taking place within the 0-25 m depth interval along

the fore-reef zone of Mururoa. From 40 m deep, light extinction is

considered to be critical for high coral growth rates (Bablet et

al., 1995) as observed in other Tuamotu atolls (Faure and Laboute,

1984) and for high carbonate production. In the model, the rates

of carbonate production have been chosen to evolve as a function

of depth, according to an exponential curve, the shape of which is

governed by a scale factor of 30 m. The rates were initially

specified by a maximum value which remains constant within the 0-

33

25 m depth interval, gradually decreases down to 40 m, drops

drastically from 40 to 65 m and tends toward zero from 65 m

downwards (Figure 4).

Although they may approximate gross production rates, the

values discussed in the present study express net production

strictly, i.e. the balance of gross production and destruction

(bioerosion plus mechanical abrasion), sediment volumes actually

trapped and accumulated into the atoll. Estimates of reef

accretion rates through time are usually based on drill core data.

There is no direct vertical reef accretion rates available for

Mururoa, but reports from French Polynesian reefs for the past 10

ka indicate that these rates range from 1 to >15 mm/yr in reef-

edge settings, and from 0.1 to 6 mm/yr on average in backreef and

lagoonal zones (Montaggioni, 2005). In-situ reef-margin growth

rates are markedly above the rates of backreef production.

However, atoll interior contains sediments largely shed by the

outer margin itself. Accordingly, in the model, the lagoon area is

assumed to accumulate amounts of sediments equal to the atoll

margin.

34

The time interval of observation is a significant determinant of

absolute accretion rates (Schlager et al., 1998). Values derived

from the Holocene record are most likely not representative of

long-term (tens to hundreds of thousands years) carbonate

sequences, especially, in the case of older shallow-water,

tropical carbonate environments in which low-frequency,

catastrophic events (i.e. storms, tsunamis) may dominate

depositional regimes and as such modulate long-term rates.

Production rates used in the model therefore are regarded as time-

averaged values coherent with the simulated time steps (Table 2);

furthermore, it is worth to note that these rates are maximum in

the upper 6 m of the water column.

Sediment transport

Shallow marine lateral transport of carbonate sediment is a

minor process at the scale of a single reef system, since detrital

carbonates are usually produced and accumulated in situ,

especially, in atoll lagoons interpreted as self-governing zones

of deposition (Fütterer, 1974; Adjas et al., 1990; Yamano et al.,

35

2002). Off-reef export of sediments can be regarded however as an

important process in the development of reef-associated deposits.

A number of studies indicated that reef crests and reef flats can

serve as point sources to nearby lagoons and/or foreslopes thus

promoting progradation inwards and seawards (Hughes, 1999;

Gischler, 2006; Harris and Heap, 2009; Morgan and Kench, 2012).

Transport functionality of the DIONISOS software allows, amongst

others, long-term sediment shift in the direction of water flow

(i.e. wave-driven, water-driven and slope-driven transport).

Sedimentation takes place when transport capacity decreases.

Sediment transport by wave depends upon wave energy and wave

action depth. Calculations of water (mass)-driven transport and

slope (gravity)-driven transport are based on a diffusion

equation. Sediment diffusion has been commonly used to simulate

sediment transport (Hill et al., 2009). The relevant algorithm

asserts that particles shift downslope at a rate that is

proportional to the tangent of the slope angle, to water depth and

to sediment grain-size. For transport along both the inner and

outer slopes, the average sediment flow is expressed as follows: Q

(km2/ka) = K slope . S with K (km2/ka) as the diffusion coefficient

36

and S as slope angle. For transport controlled by water masses,

the equation is : Q = K water . water .S . K values range between 0

to 4.103. For each time increment, sediments transported into the

lagoon builds up to sea surface and out across the atoll rim and

slope until all displaced sediments are deposited.

At Moorea, patterns of lateral transport are governed dominantly

by wind-induced waves (Bablet et al., 1995). The prevailing winds

come from the southeast. Paleocurrents in the area were assumed to

move from southeast to northwest across the atoll interior. The

parameters used in the simulations include wind velocities (12,

7.5 and 3.5 m/s), wind frequency (1% = 3.6 days per year, 9% = 33

days per year, and 6% = 22 days per year), wind propagation

angles (N170° to N125°), wave energy (61.2, 6.6 and 0.2 kW/h)

and wave action depths (11.0, 4.5 and 1.0 m).

Subaerial erosion

As stressed by Enos (1991) and Webster et al. (2007), little is

known about the long-term erosional pattern of subaerially exposed

carbonates in tropical areas; the end-product is known to be a

37

solutional lowering of bare rock surfaces. During low-sea stands,

rates of denudation in reef limestones may vary significantly

according to lithology (especially initial rock porosity and

permeability), terrace elevation and topography, timing and

duration of subaerial exposure and climate. In particular, there

would be a robust relationship between rainfall and maximum atoll

lagoon depth, thus highlighting the prominent role of climate in

the morphological evolution of atolls (Purdy and Winterer, 2001).

However, the rates at which subaerial erosion destroys atoll

limestones are poorly constrained. Based on estimates of the

amount of reef rock eroded since the last interglacial, the rates

of subaerial erosion have been speculated to range between 0 and

0.017 m per 1,000 years (ka) at Mururoa, 0.082 and 0.202 m/ka at

Enewetak and 0.011 and 0.146 m/ka at Tarawa (Paulay and McEdward,

1990). These rates can be regarded as minimum when compared with

those obtained from more sophisticated methods. For example, on

Aldabra Atoll (Western Indian Ocean), calculations based on ground

morphometric analysis gave mean values of 0.26 m/ka, while short-

term erosion rates measured in-situ using a micro-erosion meter

vary from 0.10 to 0.51m/ka with a mean value of about 0.25 m/ka

38

(Trudgill, 1979). These rates are consistent with the data gained

from other tropical/subtropical limestone sites in the Pacific.

From the accumulation rate of cosmogenic 36Cl in calcite measured

in equatorial New-Guinean limestones, Stone et al. (1994) obtained

rates of 0.20 m/ka. Similarly, Matsukura et al. (2007) have

assessed the rates of ground lowering of raised Holocene reef

terraces at Kikai-jima island (Ryukyus, Japan) to be 0.10 to 0.3

m/ka (mean values: 0.25 m/ka) using a linear relationship between

the elevation of pedestals and the duration of emergence.

Considering the similarity of climate parameters between Aldabra

(seasonal mean air temperatures ranging from 22 to 31°C; mean

annual rainfall: 1100 mm; in Farrow, 1971) and Mururoa (22.5 to

27°C, and 1,350 mm/yr on average) sites, a value of 0.25 m/ka was

used in the model as the vertical lowering rate. This rate is

taken as a variable that episodically removes the upper part of

each predicted carbonate unit during a low sea-level event; the

amount of removed material is defined as the result of multiplying

the erosion rate by the duration of exposure. Given the relatively

short time of limestone exposure during low-sea stands (See the

“Discussion” section), subaerial erosion appears not to have

39

significantly altered the initial geometry, architecture and

thickness of the deposits.

RESULTS

All prior estimated parameters have been used as input to

initial modelling tests (Table 3) illustrated by the stratigraphic

cross-sections of the Quaternary atoll deposits (Figures 5 to 7).

The most significant tested parameters are subsidence and

carbonate production rates.

Testing subsidence rates

There is no general agreement about the long-term geological

estimates of linear subsidence at Mururoa. As mentioned

previously, the expected rates range between 40 and 125 m/Ma. The

stratigraphic response of the atoll to subsidence during the

simulated 1.8 Ma period was investigated by running subsidence

rates of 25, 40, 75, 90, 105 and 120 m/Ma. In these successive

runs, production rates of 0.50 to 0.80 mm/yr, 0.80 to 2.50 mm/yr

40

and 2.50 mm/yr were used as best “base-cases” for the time

intervals of 1.80 to 1.0 Ma, 1.0 to 0.50 Ma and 0.50 Ma to the

present respectively.

The simulation results reveal that atoll architecture and the

distribution of depositional stacking patterns are strongly

impacted by subsidence-generated accommodation (Figure 5).

Increasing the rate of subsidence from 25 to 120 m/Ma vertically

increases accommodation space by about 171 m over the 1.80-0 Ma

time interval. As a result, the Quaternary sequence within the

atoll rim can reach a maximum thickness of 80 m. Sedimentation in

the atoll interior, which is also significantly affected by

subsidence, starts to operate as soon as subsidence rate is 40

m/Ma, during the MIS-5e high stand.

Subsidence at lower rates of 25 to 40 m/Ma maintains the

platform exposed at elevations of about 35 to 5 m respectively. In

both cases, highly progradational deposition takes place along the

initial platform margin and flanks. The interior is weakly to not

sediment-supplied. From a subsidence rate of 75 m/Ma, marginal

accumulation is able to maintain pace continuously with the

successive rises in sea level. The overall atoll morphology and

41

stratigraphy becomes gradually closer to those actually observed.

First, beneath the atoll rim, a condensed section develops,

strictly consisting of high-stand deposits not older than MIS 11.

At rates of 90, 105 to 120 m/Ma, the platform margin undergoes

more frequent inundation; the platform interior remains

episodically flooded during some sea-level minima and acquires a

well-pronounced “bucket” morphology. In these respective

scenarios, the lagoonal deposits record all high stands younger

than 1 Ma, while low-stand units are missing, except for MIS 10

and 8.

All architectural and stratigraphical characteristics described

above have demonstrated to be in great part inconsistent with

those derived from the field and drilling data. Beyond the fact

that subsidence at rates of 25 to 40 m/Ma result in final platform

emergence, it is important to notice the non-linear relationships

between the stratigraphic responses and the subsidence rates for

the scenarios based on subsidence rates of 75, 90 and 120 m/Ma.

At rate of 75 m/Ma, the total thickness of the Quaternary sequence

does not exceed 25 m at the atoll-rim site and 30 m at the lagoon

site. The sequence thickness remains slightly underestimated using

42

a rate of 90 m/Ma (about 40 m at both sites), and becomes

overestimated as the rate is 120 m/Ma (about 75 m at both sites).

In addition, the platform margin geometry varies as a function of

subsidence rates: progradation at lower subsidence rates, while

aggradation at higher rates. From subsidence rates of 120 m/Ma,

aggradation tends to dominate over progradation. Correlatively,

the width of the prograding margin core tends to decrease seawards

from 200 to about 130 m. These findings strongly suggest that the

best-estimate subsidence rate ranges around 105 m/Ma.

Independantly of the subsiding conditions between 1.8 and 0.50

Ma, the sediments prominently accumulate along the initial

foreslopes, building toe-of-slope to ramp-like carbonate units.

The final profile of the foreslopes down to 300 water depth is

weakly affected by variations in the subsidence rate. From about

10 m to 200 m deep, the slope angle remains constant at around 65

°, then diminishes to 25° basinwards. This is in perfect agreement

with the attributes of the presently observed outer fore-reef

slope. The only significant topographical change is the downward

shift of slope break, from steeper to more gentle. With

43

increasing subsidence rates, the slope break migrates from 180 m

to 260 m deep.

Testing carbonate production rates

In order to test the sensitivity of the model to changes in the

rate of sediment production, three test series were performed. One

series has experimented differing production rates (0.5, 1, 2.50,

4, 5 and 6 mm/yr) that remained unchanged over the duration of 1.8

million years. The second batch of tests is based on rates varying

from 0.50 to 10 mm/yr among the intervals of 1.80-1.0 Ma, 1.0-0.50

Ma and 0.50 Ma-present respectively. In the third test series, the

rates of carbonate production were constant, with 1, 4, 6 and 10

mm/yr during the 0.50 Ma-present period successively, while using

rates of 0.50 and 0.80 mm/yr over the 1.80-0.50 Ma interval

successively. For each run, the most realistic subsidence rate of

105 m/Ma was set to constant (see the section above).

The results from the first test series are illustrated by

Figures 6a and 6b in which the rates of 0.5 and 5 mm/yr are used

as limit conditions. With the lowest accretion rate, the

44

depositional system is unable to catch up with sea level. The

atoll platform rapidly reaches steady-state conditions. The final

stage is a submerged platform with a “bucket” topography less

pronounced than at present observed (Figure 6a). The platform

interior, i.e. lagoon area, 50 m in maximum depth, comprises

about 20 m-thick, dominantly aggradational deposits, the lowermost

of which are younger than 0.5 Ma. The innermost three-quarters of

the platform-edge surface is overcapped by a ridge less than 30 m

thick, but no typical reef morphology is produced. The Mio-

Pliocene basement partially crops out at the outermost one-quarter

of the edge and at the upper foreslope; the latter remains totally

devoid of sediment, probably as a result of its steepness.

Deposition appears to be mainly controlled by slope instability

and occurs from about 70 m water depth in the form of a tongue of

slope abruptly thickening basinwards (maximum thickness >150 m).

At its upper part, the tongue is composed of a few-metres thick

units, ranging from 1.8 to about 0.80 Ma in age; younger deposits

are missing. By constrast, from about 200 m deep, the lower part

of the tongue records the complete Quaternary stratigraphic set.

The flank slope is 45°-dipping down to about 250 m water depth,

45

then progressively decreases from 25° to 10°. Running the highest

rate (5mm/yr) leads to the development of a typical table reef

system, i.e. an isolated platform with a continuous and regular

flat-topped surface (Figure 6b). The basement top is submerged for

the first time during the 1.0-0.50 Ma interval, resulting in total

infilling of the platform interior. The lagoonal sediments deposit

during all of the high sea stands over the past 1.0 Ma; the

resulting sequence is composed of units with varying thickness,

from about 1 m (MIS 27 to 13), 5 m (MIS 7 and 9), 10 m (MIS 5.5)

to 15 m (MIS 11). The outer rim consists of a raised terrace, a

few metres in elevation and up to 500 m wide, developed during the

last interglacial stage (MIS 5.5). The platform margin is a

dominantly seaward-prograding build-up, up to 300 thick. As soon

as the earliest Pleistocene stages, from 1.8 to 1.0 Ma, the

basement flanks are capped by a series of narrow (less than 300 m

wide) true framework reefs of fringing type, exhibiting flat-

topped reef crests and sub-vertical outer reef slopes. However,

the total thickness of the sequence deposited over the 1.0-0.50 Ma

span does not exceed 20 m. The thickest reef unit (25 m) accretes

during MIS 11 (0.43-0.38 Ma). All low-stand deposits identified in

46

the model (MIS 12 to 2) are restricted to the system flanks and

significantly participate in the lateral development of the margin

as veneers less than 5 m thick. The Holocene reef is a 30-m wide

body, positioned right next to the emerged MIS 5-e terrace, a few

metres below. The flank slope keeps very steep (up to 65°) to

about 150 m water depth.

The second batch of models is exemplified by one end-scenario

in which the production rates increase gradually from 0.50 to 1

mm/yr through time (Figure 6c). The final obtained stratigraphic

motif obtained is that of a submerged reef platform, composed of

sedimentary units not exceeding 10 m in maximum thickness and

displaying an inner depressed area. Deposition prior to MIS 11

results in a steeply dipping ramp-like system.

An example of the third model series is given in Figure 6d. The

production rates used are 0.50, 0.80 and 6 mm/yr over the spans of

1.80-1.0 Ma, 1.0-0.50 Ma and 0.50 Ma to present respectively. The

platform system in its final stage is typified by an emerged, 125

ka-old, outer rim with a central area at sea level. The Quaternary

reef core consists of an about 40-m thick, prograding unit

47

deposited during MIS 11. Most of both high- and low-stand units

younger than MIS 11 occur as veneers capping the margin flanks.

Analysis of the models indicates that the sediment

accumulation rates have an important effect on the morphology and

internal structure of the platform system, especially, on

thickness, width and slope steepness of the carbonate bodies.

Those produced by higher accretion rates are thicker, wider and

their margin slopes are steeper. Higher accumulation rates

compensate for both the impact of water energy and gravity

processes in the spatial redistribution of sediments and thus

trigger the growth of framework-type relief. As previously

observed (see Bosence and Waltham, 1990), the greatest

progradation occurs with the greatest carbonate accumulation and

maximum flooding.

By contrast, reduced carbonate production limits or prevents

significant in-situ deposition, and does promote intense sediment

reworking and displacement. Marine erosion, wave-driven transport

and chiefly slope-driven transport act as control thresholds that

finally overbalance in-situ deposition processes. Shallow-water

carbonates therefore are not trapped into their production sites,

48

but mostly exported outside and deposit downslope in the form of

ramp-like or toe-of slope systems. These findings strongly suggest

that developing a typical atoll morphology with a central

depression only occurs through a narrow window of carbonate

production. On the test area, optimal mean production rates for

framework reef building appear to range between 1 and about 2.5

mm/yr. Mean rates less than 1 mm/yr produce submerged platforms,

while those greater than 2.5 mm/yr result in flat-topped

platforms, emerged at outer-rim sites and devoid of central

depressions. The “bucket” physiography does not depend totally

upon the initial basement topography, but greatly derives from

specific accretion rates (Warrlich et al., 2002; Schlager, 2005).

Another interesting feature is the limited development of

carbonate bodies during low-stand episodes, regardless of the

carbonate production rates. This indicates that acquiring

framework-type relief is also dependent highly upon shape and

depth of the initial topography. Flank steepness prevents any

significant vertical reef accretion (James and Ginsburg, 1979).

All these modelled scenarios are inconsistent with the observed

cross-sections. In particular, the occurrence of flat-topped reef

49

topography older than MIS 11 (>0.40 Ma) seems incompatible with

the drilling data.

Presenting the best-scenario model output

As mentioned above, numerous sensitivity tests were needed

prior to get the most realistic set of parameters identified

(Table 2). The best-fit scenario is obtained applying production

rates of 0.50 to 0.80 mm/yr, 0.8 to 2.50 mm/yr and 2.50 mm/yr over

the periods of 1.80 to 1.0 Ma, 1.0 to 0.50 Ma and 0.50 Ma to the

present respectively, at both the outer-margin and lagoon

settings. A constant subsidence rate of 105 m/Ma was applied to

the model. The successive 2-D cross-sections reveal the

depositional patterns of carbonate units through high and low sea

levels and the development history of the atoll over the past 1.80

Ma (Figure 7).

The comparison between the modelled and observed stratigraphic

architectures confirms the great internal complexity of the atoll

margin as previously suggested by Perrin (1990) and Camoin (2001).

50

The best model output is overall consistent with the

physiographical and subsurface atoll records. The modelled atoll

rim is identical in width (less than 200 m) to the observed

northeast rim zone well documented by the wells. The mean water

depth of the simulated lagoon (about 30 m) is similar to the

observed lagoon (33 m); the slope of the inner talus to the

lagoonal bottom averages 20-25 ° in both cases. However, the

bottom remains at constant depth in the model while actually

observed as deepening to its central part. Along the modelled

island foreslope, change in the slope ange, from about 60° to 25°

occurs at about 250 m deep as observed from bathymetric lines.

The shape and size of the stratigraphic units predicted by the

model are similar to those recorded from vertical drilling data

(see Table 3, “subsidence at 105 m/Ma”). Below the present-day

atoll-rim surface, the total thickness of the Quaternary deposits

range around 55-60 m in both the modelled and observed cross-

sections. However, the lateral extension of the margin that

progrades seaward from the Pliocene basement is smaller in the

model (about 150 to 160 m) than in reality (up to 250 m). This is

due to a significant change in the dominant depositional regime as

51

the rate of subsidence exceeds 90 m/Ma. In general, the

simulations of the lagoonal deposits are less realistic compared

to the outer rim and margin simulations. The predicted Pleistocene

sediments are about 55 m in maximum thickness, thicker than the

observed (28-48 m). Thickness overestimation is interpreted as

resulting from running similar production rates across both the

platform margin and interior, while in-situ carbonate production

within lagoons are usually lower than in reef-flat environments.

Paradoxically, the simulated Holocene beds are thinner (less than

5 m thick), in contradiction with field data (about 10 m thick).

Such a discrepancy may be due to unsuitability of the sediment-

transport parameters used herein for reproducing the effects of

low-frequency, high-energy events responsible for transporting

large volumes of sediment over a short period. Furthermore, while

the thickness of MIS 1, 2, 4 and 5 units estimated from seaward-

inclined drilling (Camoin et al., 2001) are consistent with those

gained from vertical drilling and modeling, the thickness of MIS

7, 8 and 9 units appears significantly overestimated (Table 5).

This may result from the difficulty to accurately assess vertical

quantities from oblique measurements.

52

The model indicates that the earliest overlapping event of the

initial platform top by shallow-water carbonates occurred during

the 1.0-0.50 Ma interval. This agrees fully with the

magnetostratigraphy-derived age (about 0.70 Ma) of a lowermost

core section extracted from the atoll rim (Aissaoui et al., 1990).

As already shown from the alternative scenarios (see above), the

earliest stages of deposition, from 1.8 to 1.0 Ma, produce metre-

thick ramp-like units that cap the upper parts of the initial

platform flanks (to depths of 50-80 m). Ramp-derived sediments

contribute to the development of a toe-of-slope complex up to 50 m

in total thickness. The model assumes that the ramp system keeps

functioning until 0.48 Ma (MIS 13), prior to change into reef-like

buildups. High-stand units (MIS 11 to 1) have developed mainly as

superimposed, aggrading reefs, while successive low-stand units

(from MIS 12) are onlapping the seaward face of high-stand reef

flanks, chiefly forming prograding bodies. The maximum thickness

of the modelled high-stand units ranges from 25 m (MIS 11) to less

than 10 m (MIS 7). These values are within the range of those

expected from the vertical well data (Table 2). Unlike the

platform-top, the base of the modelled slope contains a

53

stratigraphically complete sequence, deposited by gravity-driven

processes. The model is in accordance with the concept of “re-

flooding window” proposed by Jorry et al. (2010); sediment export

to the foreslopes mainly occur during the short period of time

during which the uppermost flanks and top of the atoll are flooded

at glacial terminations when sea level is abruptly rising.

The strong similarity between the best-estimate scenario and

the observed atoll attributes indicates that using varying

production rate inputs over time is valid. This suggests that

environmental conditions have changed over the past 1.8 Ma, and

limiting parameters other than sea-level oscillations may have

operated, especially, to restrict coral growth rate and

sedimentation across the platform and along its adjacent upper

flanks.

DISCUSSION

Validating the stratigraphic model of Mururoa atoll

54

Qualitative comparison between the modelled “best-estimate”

cross-section of Mururoa atoll and those reconstructed from the

field data (Buigues, 1982, 1998; Perrin, 1990; Ebren, 1996; Camoin

et al., 2001) reveals strong similarities in surface and

subsurface patterns. The modelled physiography of the lagoon,

outer reef rim and foreslopes are in close approximation (within

less than 20%) with the observed ones in terms of area, shape and

size. The model provides a stratigraphical and architectural

reconstruction of the atoll margin that copes with constraints

posed by drilling findings. Especially, the distribution and

thickness of sedimentary units seem being reasonably simulated

when compared with available data and considering stratigraphical

uncertainties from the outermost margins and fore-reef zone.

Unfortunately, there is no available data on the internal

structure of the lower margin parts and deeper fore-reef zone. The

fact that the main geological features of the modelled atoll

system are consistent with those expected from the observations

gives confidence that the modelled lower margin and the adjacent

deep fore-slope are realistic. The earlier sedimentary bodies over

which the MIS-13 and younger high-stand units have deposited, are

55

steeply sloping and ramp-shaped, thus meeting the geometrical

requirements of the margin and fore-reef interiors.

Five main issues were recognized by Paterson et al. (2006) in

the evolution of isolated icehouse carbonate platforms, including

atolls : (1) the two distinct development steps, with margins

growing with the rise in sea level, and interiors filling with

sediment during the fall in sea level; (2) fourth-order 0.40-Ma

Milankovitch-driven sea-level cycles dominantly influence platform

architecture, while fifth order cycles (0.10 Ma) rarely exert a

control on the platform-top strata; (3) subsidence is a

fundamental control of platform stratigraphy and geometry. At

higher rates, the number of non-deposition events is limited,

resulting in preservation of additional sedimentary units, a more

aggradational platform geometry and a well-differentiated bucket

morphology at rates of 50 to 100 m/Ma are generating; (4)

Subaerial, solution-related erosion generally has a minor impact

on sequence thickness; (5) during highstands when the 0.40 and

0.10 Ma cycles are in phase, icehouse platforms can be inundated

to depths greater than 45 m while unfilled accommodation is

prevalent. The present study is far from being in full accordance

56

with the Paterson’s predictions. Only the third and fourth issues

seem to prevail on Mururoa. Following a number of previous works

(for instance, Handford and Loucks, 1993; Schlager, 1993; Demicco

and Hardie, 2002), this study confirms that changes in

accommodation space govern shallow-water platform geometry and

internal structure, and stratigraphic stacking patterns at a

range of scales. Especially, increasing subsidence rate results in

the change from progradation to aggradation at the atoll-margin

sites.

There are noticeable differences with the other three

concepts. First, on Mururoa, there is an only prevalent stage of

platform growth; during high stands, together with margin growth,

the platform interior gets infilled, while it is occasionally

sediment-fed during sea-level drops. Secondly, the overall

architecture of the atoll system clearly appears not to be

controlled by the 0.40-Ma cyclicity, but prominently controlled by

variations in the amplitude of sea level over fifth to higher

order sea-level cycles. From 1.8 to about 0.80 Ma, during the so-

called “41-ka world”, the platform margins and interiors remained

exposed most of the time, mainly because of low-amplitude (less

57

than 70 m) sea-level cycles; deposition operated mostly along the

outer flanks. From about 0.90-0.70 Ma, during the “Mid-Pleistocene

Climate Transition” (MPT)”, owing to sea-level change to higher

amplitude (up to 100 m) cycles, the platform top was flooded for

the first time (Aissaoui et al., 1990; this study); since this

time, atoll margins have accreted and lagoon sediment-fed during

successive transgressive episodes.

Otherwise, Paterson et al. (2006) claimed that long-term

platform exposure can result only in some 30% of the stratigraphic

record at rimmed-platform tops. According to the late Pleistocene

to Holocene reef history (Davies and Montaggioni, 1985;

Montaggioni, 2005, for reviews), accommodation infilling has

mostly happened during the last 10,000 years preceding sea level

stabilization at high stand. At top of the Mururoa platform, such

conditions have presumably prevailed during every transgressive

episode, from about 0.7 Ma (MIS 17). This implies that the

maximum time length fully supporting shallow-water deposition has

not exceeded 0.090 to 0.10 million years, that is only 5.0 to 5.5

% of the entire Quaternary times.

58

An intriguing outcome of the modelling is that, over the past

1.80 Ma, three types of carbonate systems were predicted to have

successively operated along the margins and foreslopes of Mururoa

(Figure 8). From the earliest Pleistocene to about 0.90-0.80 Ma,

in response to low-amplitude sea-level modes (less than 70 m) and

subsequent emergence of the pre-existing platform top, carbonate

deposition occurred strictly along the foreslopes as toe-of-slope

deposits. From approximately 0.90-0.80 to 0.50 Ma, while the model

revealed that the platform was episodically flooded, shallow-water

sediments have continued depositing preferentially at the upper

parts of the flanks in the form of ramp-like tracts. Typical reef

frameworks did not develop prior to 0.50-0.45 Ma. However, the

sensitivity tests indicated that typical reef building would have

initiated at the beginning of the Quaternary (1.8-0.50 Ma ) only

if prior carbonate production rates exceeded 1 mm/yr, thus

promoting the antecedent foundation for reefs. Such a scenario

does not match the observational data. It is worth emphasizing

that the best-fitting model has been produced using production

rates averaging 0.50 to 0.80 mm/yr from 1.80 to 1.0 Ma and 0.80

to 2.50 mm/yr from 1.0 to 0.50 Ma. This clearly means that ambient

59

conditions have not been sufficiently conducive to reef growth

prior to 0.50 Ma. However, there is some disagreement in defining

the role of climate in reef settlement and the timing of reef

initiation over the Pleistocene, especially in the Pacific

(Montaggioni et al., 2011). There are currently few data to

constrain tropical climate variability in the south central

Pacific, during the early to mid Pleistocene. At the Pliocene-

Pleistocene transition, the tropical Pacific atmospheric

circulation pattern is expected to have been affected by high-

latitude forcing processes, resulting in a significant cooling of

at least eastern equatorial waters (Medina-Elizalde et al., 2008).

During the 41-ka periodicities, from 1.80 to 1.00 Ma, increase in

upwelling intensity, associated with enhanced trade-wind and

shoaling of the thermocline, may have been an important factor

controlling sea surface temperature and resulted in relatively

high nutrient levels (Liu and Herbert, 2004). Accordingly, this

period does not appear to have experienced optimal conditions for

luxuriant development of shallow-water, calcifying organisms in

the tropical east Pacific. The MPT (1.20 Ma to about 0.60 Ma), at

least at its onset, has been accompanied by decreases in SST in

60

tropical-ocean upwelling regions (Schefus et al., 2004; Liu and

Herbert, 2004; McClymont and Rossel-Mele, 2005; Herbert et al.,

2010) and climate instability (Raymo et al., 1998). From

approximately 0.90 Ma, the shift from the 41-ka to 100-ka rhythms

indicates a fundamental change internal to the climate system,

characterized by an increase in the severity of glaciations (Clark

et al., 2006). There is no data giving evidence for climate

deterioration and upwelling intensification around Mururoa Atoll,

but, any significant change in environmental conditions could only

resulted in habitat disturbance and have inimical effects on

shallow-water, stenothermal benthic biota. From about 0.45 Ma,

accompanying the final settlement of the “100-ka world”,

luxuriant reef development can occur on the Mururoa platform.

It is hypothesized that the sedimentary regimes to which Mururoa

has been subjected successively were mainly climate-driven. The

toe-of-slope system is believed to have mostly functioned during

the 41-ka cyclic period owing to lower sea-level amplitude and

colder SST. The ramp system is likely to have developed during the

Mid-Pleistocene Climate Transition due, at least in part, to

climate disturbance. With the emergence of the high-amplitude 100-

61

ka cyclicity and SST warming, extensive reef growth was able to

operate. This evolutionary scheme is not unique to Mururoa, but is

a pervasive feature in the development history of various

carbonate platform systems worldwide. Most of them in the Pacific

(Alexander et al., 2001; Webster and Davies, 2003; Yamamoto et

al., 2006; Montaggioni et al., 2011) and the Caribbean (Gischler

et al., 2010) have experienced change in the mode of deposition,

usually going through ramp-like deposits prior to grow as true

framework reefs from about 0.50 Ma.

The Mururoa model as an analog for mid-ocean atoll development.

The degree to which this carbonate evolutionary model can be

extended to atolls with different growth histories is uncertain.

However, the simulations completed with varying subsidence rates

and sediment production, provide an array of atoll development

schemes that probably encompass most of the atoll systems.

Constraints on subsidence rates

62

The style of atoll development shown in Figure 5a is the result

of a model run using a subsidence rate of 25 m/Ma. This pattern is

illustrated by a number of atoll-shaped, high carbonate islands

in the Indo-Pacific: Makatea, French Polynesia (Montaggioni,

1985); Rennell (Taylor, 1973; Bourrouilh and Hottinger, 1988),

Niue (Paulay and Spencer, 1992; Wheeler and Aharon, 1997), Nauru

(Jacobson et al., 1997); Henderson (Blake, 1995; Pandolfi, 1995;

Stirling et al., 2001; Andersen et al., 2010). Their present-day

coastlines exhibit a series of mid-late Pleistocene to Holocene

fringing-reef terraces at a variety of elevations, frequently

surrounding an island core composed of uplifted Mio-Pliocene

reefal carbonates. For instance, on Henderson, four generations of

Pleistocene reef units have been observed as distinct seaward-

prograding packages respectively culminating at heights of 6 to

about 30 m. U-series ages revealed that reef growth took place at

about 0.630 Ma (MIS 15), 0.322 Ma (MIS 9.3), 0.307 Ma (MIS 9.1),

0.240-0.234 Ma (MIS 7.5). The last interglacial stage (MIS 5.5)

although radiometrically unidentified, is considered to have been

63

recorded, at present preserved in the form of recrystallized reef

limestones.

The modern atoll architecture generated by using a subsidence

rate of 40 m/Ma (Figure 5b) is typified by emergent, metre-thick,

last interglacial to Holocene reef deposits, that overlie an

exposed antecedent platform-top. Although reef exposure in the NW

Tuamotu area has been catalysed by uplifting, not by moderate

subsidence, some atolls, including Mataiva, Tikehau, Niau,

Kaukura, Anaa, have a structure mimicking that of the

stratigraphic model. These islands have emergent Holocene or last

interglacial terraces at elevations of 1 to 8 metres above

present mean sea level, locally overtopping a reef substrate of

Mio-Pliocene age (Pirazzoli et al., 1988b; Delesalle, 1985;

Harmelin-Vivien, 1985).

The simulations completed with subsidence rates ranging between

75 and 120 m/Ma provide morphologic and stratigraphic patterns

that are regarded as typical of modern, low-lying carbonate

islands, i.e. mid-ocean atolls and a number of shelf reef

platforms. Based on drilling and seismic data, these have been

demonstrated to consist of Quaternary plurisequential sediment

64

piles capping a Mio-Pliocene carbonate core beneath both outer-rim

and lagoonal zones (see Montaggioni and Braithwaite, 2009, p. 237-

247; Woodroffe and Biribo, 2011, for reviews). The Quaternary

sequences are up to 30-m thick beneath the Houtman Abrolhos

platforms, western Australia (Collins et al., 1998), 55-95 m

beneath the Belize reef platform complex, western Atlantic

(Gischler et al., 2010), 70-100 m thick at Bikini and Enewetok

Atolls, Marshall Islands, western Pacific (Tracey and Ladd, 1974;

Quinn and Saller, 1997), up to 200 m thick at Funafuti Atoll,

Western Pacific (Ohde et al., 2002), probably up to 200 m at

Midway Atoll, northern Pacific (Ladd and Tracey, 1970), Chenhang

(Jian et al., 1997) and Yongshu Atolls, southern China Sea

(Huanting et al., 1996), and the Maldives, western Indian Ocean

(Purdy and Bertham, 1993; Aubert and Droxler, 1996).

Linear subsidence for some of these atolls were estimated based

on the present-day position and age of the volcanic bed-rock top:

18 m/Ma (Lincoln and Schlanger, 1991) to 39 m/Ma (Quinn and

Matthews, 1990) at Enewetok, 45 m/Ma at Pukapuka and Rakahanga,

Cook Island (Hein et al., 1997), 30 m/Ma at Funafuti (Ohde et al.,

2002). If correct, according to the present-day stratigraphic

65

position of reef-rim surfaces (at respectively 8-12 m, 15-22 m and

26 m below present sea level) that have formed during the Last

Interglacial as sea level was + 6 m relative to present sea level

(Siddall et al., 2006), the atolls of Enewetok, Pukapuka,

Rakahanga and Funafuti have developed necessarily in the form of

submerged banks the tops of which were lying at water depths of

around 15 to 30 m. These scenarios are conflicting with

paleoecological and facies patterns defined from these atolls

(Enewetok:Tracey and Ladd, 1974, Quinn, 1991; Pukapuka,

Rakahanga: Gray et al., 1992; Funafuti: Royal Society, 1904,

Johnson, 1961). In addition, on Enewetok, applying a constant

subsidence rate of 30 m/Ma would imply that the pre-Quaternary

basement top, at present found at about 230 m downcore, has

remained mostly below the euphotic zone, at minimum depths of

about 60 to 80 m during low stands, forming a deep submerged bank,

fully incompatible with shallow-water carbonate deposition.

The modeling approach rules out the assumption that carbonate

sedimentation on most atolls has been triggered by weak

subsidence. It appears clearly that the previously expected

subsidence rates were markedly underestimated. Both atolls are

66

thought to have subsided at rates greater than 100 m/Ma. This is

sustained by compositional patterns identified in cored sections.

For instance, beneath the Funafuti outer rim, the sediments

deposited within the upper 189 m over the past 1.5 Ma were

interpreted as reefal in composition (Jonhson, 1961; Ohde et al.,

2002). With a subsidence rate up of about 125 m/Ma, the antecedent

foundation is likely to have been located at about 15 m water

depth 1.8 million years ago, and permanently remained within a

depth-range of less than 45 m, fully compatible with reef growth,

according to the maximum depth for optimal carbonate production

rate. This agrees with the conceptual models by Paterson et al.

(2006): during transgressions and highstands, when isolated

platforms are inundated to depths greater than 45 m, accommodation

space remains unfilled. Accordingly, rates of subsidence ranging

from 50 to up to 100 m/Ma, can be considered to be critical to

promote the development of low-lying, saucer-shaped coral islands

from initially submerged platforms, over the control of 41, 000

to 100,000 year-sea level cycles.

Another interesting feature to be emphasized is the difference

in terms of dominant depositional modes at margin sites between

67

Mururoa and Enewetok. As previously shown, at Mururoa,

progradation has finally dominated over aggradation. By contrast,

on Enewetok, seismic surveys and submarine lithologic observations

support a prominently continuous, aggraditional history (Quinn and

Saller, 1997). Such a discrepancy in the development history of

the two atoll margins is probably due to differential tectonic

behaviour. Higher subsidence rate may have opened wider

accommodation space (up to 90 m at Enewetok versus 60 m at

Mururoa).

Constraints on production rates

The present results indicate that typical atoll morphologies

are provided from net production rates not lower than 2.50 mm/yr

on average during high sea-stands for at least the past 0.5 Ma. By

contrast, testing net production rates varying from 0.5 to 1 mm/yr

over the same time interval resulted in the formation of isolated

submerged banks that are culminating at water depths of a few

metres to about 20 m, typified by a “bucket” morphology and

exhibiting a few-meter-thick, late Pleistocene to Holocene

68

carbonate deposits at top. Modern morphological analogs are

generally only a few kilometers in diameter and typically of

circular form, especially in the tropical Pacific and Indian

Oceans as well. For example, Alexandra Bank, located on the

Melanesian Border Plateau in the central Pacific, is an atoll-

shaped, bank lying at depths of 18-25 m (Fairbridge and Stewart,

1960). Another example is given by Geyser Bank, 300 km north-west

of Madagascar (Indian Ocean), exposed at low tide (Maugé et al.,

1982).

From production rates averaging or up to 4 mm/yr, the modelled

platforms refer to carbonate islands, with large, exposed outer

rims and infilled interiors. For example, modern morphological

counterparts are found in the Seychelles, Western Indian Ocean;

Aldabra Atoll and some islands of the Amirantes Group consist of

raised limestones of late Pleistocene or Holocene age between

about + 1 and + 8 m above present mean sea level (Braithwaite,

1984; Pirazzoli et al., 1990). Similarly, some of the Scattered

Islands (e.g. Glorioso and Europa islands) in the Mozambique

Channel (Western Indian Ocean) exhibit paleo-reef flats built up

69

during the last interglacial high sea levels and at present

elevated at + 4 m (Gaven and Vernier, 1979).

However, carbonate production rates, measured from late

Pleistocene to Holocene reef packages and used in the simulations,

are difficult to compare with carbonate accumulation rates

obtained from the older record. The latter appear systematically

underestimated, with mean values markedly lower than 0.10 mm/yr.

The vertical accumulation rates are usually inferred from

Quaternary sequences extracted from atoll rims, by dividing the

thickness of a given core section by the time over which it is

thought to have accumulated. At Mururoa, Aissaoui et al. (1990)

calculated carbonate accumulation rates of 0.065 mm/yr from 0.70

Ma to present, and 0.012-0.015 mm/yr from 1.8 to 0.70 Ma. At

Enewetok, deposition was assumed to have occurred at rates of

0.066 mm/yr for the past 0.60 Ma, and 0.060 mm/yr from 0.60 to 1.6

Ma (Quinn and Saller, 1997), while the Funafuti sequence was

believed to form at 0.013 mm/yr over the last 1.5 Ma (Ohde et al.,

2002). Similarly, McNeill (2005) reported rates averaging 0.014

mm/yr from sequences of the uplifted Mahé atoll in the western

Pacific. Such low rates do not reflect the actual patterns of

70

carbonate production and deposition during transgressive and high-

stand events because they include both hiatuses due to non-

depositional periods and to subaerial erosion. It should be

stressed that, over the last 1.80 Ma, only 10-15 % of the time may

have allowed shallow-water, carbonate deposition on platform-top

settings. At Mururoa, if the assumption that platform-top

deposition has operated only during about 5.0% of the entire

Quaternary, the way in which accumulation rates have been

calculated by Aissaoui et al. (1990) result necessarily in an

under-estimate by a factor of 18-20, irrespective of the effects

of late diagenesis. The rates so established do no express net

accumulation processes, but only preservation status of

limestones. Brought back to a maximum depositional time interval

of 0.90-0.10 million years, the rates by Aissaoui and associates

fall within a range of 1.2 to 1.3 mm/yr; these values thus become

consistent with mean rates derived from Holocene reef growth.

Rates of progradational processes are poorly documented in the

fossil record (McNeill, 2005). The simulated highest rates of

seaward accretion at the margins of Mururoa are in the range of 10

and <2 mm/yr during high and low sea levels respectively. These

71

rates are consistent with those measured from fringing reef fronts

(5-10 mm/yr) at St-Croix Island in the Caribbean (Hubbard et al.,

2005).

Value and limitations of the model

Over the last two decades, stratigraphic forward modelling

using process-based algorithms has been applied to get new

insights into factors controlling of shallow-water carbonate

deposition. However, as emphasized by Dalmasso et al. (2001) and

Warrlich et al. (2002), major challenges arise in attempting to

validate the resulting models due to a variety of uncertainties

and limitations. There are uncertainties in the identification of

processes and environmental variables regarded as the most

efficient in the control of reef evolution, being aware of the

fact that no simulation can take into account all of them. In

addition, there are limitations to understand physical processes

and to simulate them numerically. It results in a simplification

of numerical approaches that reduce the accuracy and realism of

the model.

72

DIONISOS has simulated the Quaternary development of Mururoa

Atoll with remarkable accuracy, despite significant uncertainty

due to the limited amount of drilling information on the internal

structure of the atoll margins and adjacent flanks. The best-

fitting model can be estimated with up to 80% confidence for the

architecture of the outer rim and the lagoon, and with about 50-

60% confidence for that of the margins and deeper fore-slopes.

Sensitivity analysis has demonstrated the relative influence of

eustacy, subsidence and carbonate accumulation rates on atoll

structure and development patterns. However, the degree to which

“long-term” processes (i.e. eustacy, subsidence”) compared to

“short-term” processes (i.e. carbonate production and

accumulation, wave-driven and slope-driven sediment transport)

“can individually account for the atoll architecture is difficult

to assess.

Some important limitations of the present models, especially

auto-cyclic facies 3-D evolution, could have been reduced with 3-D

DIONISOS modelling (Seard et al, 2013) by taking into account

short-term and long-term sediment transport by wave, currents and

slope instability. However, it is expected that applying the 3-D

73

version would not change significantly the key outcomes,

especially the overall stratigraphic picture of atoll development

and architecture and the succession of the 3 sedimentary regimes.

Second, it does take into account potential submarine landslide

events known to occur episodically along the steep atoll flanks

and causing important disturbances in stratal organization

(Holcomb and Searle, 1991; Keating, 1998). Another limitation is,

as claimed out by Barrett and Webster (2012), that biological

attributes and environmental requirements of the main reef

builders and their interactions are difficult to describe in

mathematical terms. Several parameters, not simulated, are known

to be important in coral growth and shallow-water carbonate

production, including salinity, sea surface temperature, aragonite

saturation and nutrient availability (see Montaggioni, 2005, for

review). For instance, the use of residence time of water in the

reef-rim and lagoonal zones and supersaturation of calcium

carbonate in sea water as key drivers for carbonate production

would explain the formation of non-ordered stratal architecture by

lateral migration in the locus of deposition (Hill et al., 2009).

Moreover, consideration has been recently given to carbonate mud

74

in suspension and nutrient availability used as limiting factors

in modeling carbonate facies distribution and stratigraphy

(Clavera-Gispert et al., 2012). However, there are poor

constraints on such processes over display times longer than a few

hundreds of years. A more realistic modeling of atoll stratal

geometries and heterogeneities with higher temporal resolution at

the very least should require better constraints on atoll

hydrodynamics (Peterson et al., 2006), slope gravity processes and

submarine landslide events (Holcomb and Searle, 1991; Keating

1998), preservation (Hill et al., 2012), and meteoric diagenetic

effects (Matsuda et al., 2004; Paterson et al., 2006).

CONCLUSIONS

The present case study, based on both re-examination of

previously published observational data from Mururoa Atoll, and 2-

D forward stratigraphic modelling, provides new insights into the

Quaternary development history of mid-ocean atolls. Modelling the

high-resolution stratigraphic architecture of Mururoa Atoll, well

constrained by absolute ages, allows a better understanding of

75

critical processes (eustasy, subsidence, carbonate production)

that controlled carbonate reef dynamics since the past 1.8 Ma.

(1)The antecedent topography appears to be a significant driver

of the present-day morphological attributes. Especially, the

“bucket” atoll morphology appears in great part inherited from

Pre-Quaternary subaerial solution, although reef accretion

preferentially localized at margin sites has amplified the relief

of the basement.

(2)The best-estimate scenario corroborates and clarifies the

original field models derived from geophysical and geological

surveys. The test simulations reveal that subsidence at a constant

rate of 105 m/Ma, net carbonate production at 0.50 to 0.80 mm/yr

during the interval 1.80-1.00 Ma, at 0.80 to 2.50 mm/yr from 1.0

to 0.50 Ma, and at 2.50 mm/yr from 0.50 Ma to present, with

subaerial erosion at a constant rate of 0.25 m/ka, are optimum to

best meet the observational data.

(3)Three depositional carbonate systems are predicted to have

successively functioned since the earliest Pleistocene: toe-of-

slope systems from 1.80 Ma to about 0.80 Ma, ramp-like systems

from 0.80 to 0.50 Ma, and finally, reef systems from 0.50-0.45 Ma

76

back to the present. The development of these systems is thought

to have been driven by changes in sea-level cyclicity and

climate. The low-amplitude 41-Ka sea-level cycles have precluded

any flooding of the Mio-Pliocene basement, and water cooling has

catalysed weak benthic carbonate production, thus restricting

deposition to the atoll foreslopes, as gravitational packages.

During the Mid-Pleistocene Climate Transition, climate

deterioration and upwelling intensification have affected shallow-

water carbonate production; only ramp-like units have developed at

the platform top. With the emergence of the high-amplitude 100-ka

sea-level modes and climate restoration, reef frameworks have

been generated. The margin and adjacent foreslopes to depths of

about 100 m result mainly from progradation of stacked fringing

reef bodies during high-stands.

(4)Climate variability seems to have played a prominent role in

controlling the development of carbonate platforms worldwide. The

simulation-based findings are consistent with data from various

tropical shelf systems. Most of the true framework reefs (Great

Barrier Reef, New Caledonia, Ryukyus, Belize) appear to have been

preceded by ramp systems, initiated not prior to 0.5 Ma.

77

(5) The Mururoa atoll model has demonstrated that a number of

previous atoll evolutionary schemes in the Pacific could deserve

re-interpretation. Using this model should provide more realistic

predictions, particularly, about subsidence and carbonate

production rates.

(7)The 2-D DIONISOS carbonate model and the input data used for

the simulations have proven to be able to closely approximate the

geometry and internal structure of the atoll sedimentary packages

over the past 1.80 Ma. However, there are limitations in 2-D

models, since the hydrodynamic parameters are partly incorporated

in the tested production rates. In addition, to generate a better

development model, new simulations should pay attention to more

realistic hydrodynamic conditions and to additional environmental

parameters (nutrient availability, calcium carbonate saturation

rate, late diagenetic effects) when possible.

ACKNOWLEDGEMENTS

78

Special thanks go to Mohamed Rezine for contributing to computer

simulations. This contribution is dedicated to the memory of our

friend and colleague Guy Cabioch.

REFERENCES

Adjas, A., Masse, J.P. and Montaggioni, L.F. (1990) Fine-grained

carbonates in nearly closed reef environments: Mataiva and

Takapoto atolls, Central Pacific Ocean. Sedim. Geology, 67,115-132.

Aissaoui, D. M. (1988) Magnesian calcite cements and their

diagenesis: dissolution and dolomitization, Mururoa Atoll.

Sedimentology, 35, 821-841.

Aissaoui, D.M. and Kirschvink, J.L. (1991) Atoll

magnetostratigraphy: calibration of their eustatic records. Terra

Nova, 3, 35-40.

Aissaoui, D.M., Buigues, D. and Purser, B.H. (1986) Model of reef

79

diagenesis: Mururoa Atoll, French Polynesia. In: Reef Diagenesis (Eds

J.H. Schroeder and B.H. Purser), pp. 27-52, Springer-Verlag,

Berlin

Aissaoui, D.M., McNeill, D.F. and Kirschvink, J.L. (1990)

Magnetostratigraphic dating of shallow water carbonates from

Mururoa Atoll, French Polynesia : implications for global eustacy.

Earth. Planet.Sci. Letters, 97,102-112.

Alexander, I., Andres, M.S., Braithwaite, C.R.J., Braga, J.C.,

Cooper, M.J., Davies, P.J., Elderfield, H., Gilmour, M.A., Kay,

R.L.F., Kroon, D., McKenzie, J.A., Montaggioni, L.F., Skinner, A.,

Thompson, R., Vasconcelos, C., Webster, J. M. and Wilson, P.A.

(2001) New constraints on the origin of the Australian Great

Barrier Reef : results from an international project of deep

coring. Geology, 29, 483-486.

Andersen,M.B., Stirling,C.H., Potter,E.-K., Halliday, A.N., Blake,

S.G., McCulloch, M.T., Ayling, B.F. and O’Leary, M.J. (2010) The

timing of sea-level high-stands during Marine Isotope Stages 7.5

80

and 9: Constraints from the uranium-series dating of fossil corals

from Henderson Island. Geochimica et Cosmochimica Acta, 74, 3598-

3620.

Anderson, N.L. and Franseen, E.K. (1991) Differential compaction

of Winnipegosis reefs – a seismic perspective. Geophysics, 56,

142-147.

Aubert, O. and Droxler, A. W. (1996) Seismic stratigraphy and

depositional signatures of the Maldive carbonate system (Indian

Ocean). Marine and Petroleum Geology, 13, 503-536.

Bablet, J.P., Gout, B. and Goutière, G. (1995) Les atolls de

Mururoa et de Fangataufa (Polynésie Française) – III- Le milieu

vivant et son évolution. Masson, Paris, 306 pp.

Bardintzeff, J.M., Demange, J. and Gachon, A. (1986) Petrology of

the volcanic bedrock of Mururoa Atoll (Tuamotu archipelago, French

Polynesia). J. Volcanol. Geotherm. Res., 28, 55-83.

81

Barrett, S.J., and Webster, J. M. (2012) Holocene evolution of the

Great Barrier Reef: Insights from 3D numerical modelling. Sed.

Geol., 265–266, 56-71

Belopolsky, A. and Droxler, A. W. (2004) Seismic expressions and

interpretation of carbonate sequences : The Maldive Platform,

equatorial Indian Ocean. Am. Assoc. Petrol. Geol., Studies in

Geology, 49, 1-46.

Blake, S.G. (1995). Late Quaternary history of Henderson Island,

Pitcairn Group. Biol. J. Linn. Soc., 56, 43-62.

Bosence, D. and Waltham, D. (1990). Computer modeling the internal

architecture of carbonate platforms. Geology, 18, 26-30.

Bosscher, H. and Southam, J. (1992) CARBPLAT – A computer moidel

to simulate the development of carbonate platform. Geology, 20,

235-238.

82

Bourrouilh-Le Jan, F.G. (1979) Les plates-formes carbonatées de

haute énergie à rhodolithes et la crise climatique du passage mio-

pliocène dans le domaine pacifique. Bull. Centr. Rech. Explor.

Prod. Elf-Aquitaine, 3, 489-495.

Bourrouilh-Le Jan, F.G. and Hottinger, L.C. (1988) Occurrence of

rhodolithes in the tropical Pacific – A consequence of Mid-Miocene

paleoceanographic change. Sedim. Geol., 60, 355-367.

Braithwaite, C.J.R. (1984) Geology of the Seychelles. In :

Biogeography and Ecology of the Seychelles Islands (Ed D.R.

Stoddart) , pp. 17-38, Dr.W. Junk Publishers, The Hague.

Braithwaite, C.J.R. and Camoin G. F. (2001) Diagenesis and sea-

level change : lessons from Moruroa, French Polynesia.

Sedimentology, 58, 259-284.

Buigues, D. (1982) Sédimentation et diagenèse des formations

carbonatées de l’atoll de Mururoa (Polynésie Française). Unpubl.

Ph.D. Thesis, University of Paris-Orsay, 203 pp.

83

Buigues, D. (1985) Principal facies and their distribution at

Mururoa Atoll (French Polynesia). Proc. Fifth Intern. Coral Reef

Congr., Tahiti, 3, 249-255.

Buigues, D. (1997) Geology and hydrogeology of Mururoa and

Fangataufa, French Polynesia. In: Geology and Hydrogeology of Carbonate

Islands (Eds H.L. Vacher and T.M. Quinn), pp. 433-452, Elsevier,

Amsterdam.

Buigues, D. (1998) La couverture carbonatée d’un atoll: exemple de

Mururoa et Fangataufa. Géologie de la France, BRGM Editions, 3, 87-96.

Buigues, D., Gachon, A. and Guille, G. (1992) L’atoll de Mururoa

(Polynésie Française)- 1- Structure et et évolution géologique.

Bull. Soc. Géol. France, 163, 645-657.

Burgess, P.M. and Wright V.P. (2003) Numerical forward modeling of

carbonate platform dynamics: an evaluation of complexity and

completeness in carbonate strata. J. Sed. Res., 73, 637–652.

84

Camoin, G.F., Ebren, Ph., Eisenhauer, A., Bard, E. and Faure, G.

(2001) A 300 000-yr coral reef record of sea level changes,

Mururoa atoll (Tuamotu archipelago, French Polynesia).

Palaeogeography, Palaeoclimatology, Palaeoecology, 175, 325-341.

Chevalier, J.-P., Denizot, M., Mougin, J.L., Plessis, Y. and

Salvat, B. (1969) Etude géomorphologique et bionomique de l’atoll

de Mururoa (Tuamotu). Cahiers du Pacifique, 12-13, 9-144.

Clark, P.U., Archer, D., Pollard, D., Blum, J.D., Rial, J.A.,

Brovkin, V., Mix, A.C., Pisias, N.G. and Roy, M. (2006) The middle

Pleistocene transition: characteristics, mechanisms, and

implications for long-term changes in atmospheric pCO2. Quat. Sc.

Rev., 25, 3150-3184.

Clavera-Gispert, R., Carmona, A., Gratacos, O. and Tolosana-

Delgado, R. (2012). Incorporating nutrients as a limiting factor

in carbonate modelling. Palaeogeog., Palaeoclim., Palaeoecol., 329-330,

150-157.

85

Coyne, M.K., Jones, B. and Ford, D. (2007) Highstands during

Marine Isotope Stage 5: evidence from the Ironshore Formation of

Grand Cayman, British West Indies. Quat. Sci. Rev., 26, 536-559.

Crosby, A.G., McKenzie, D. and Sclater, J.G. (2006) The

relationship between depth, age and gravity in the oceans. Geophys.

J. Int., 166, 553-573.

Dalmasso, H., Montaggioni, L.F., Bosence,D., and Floquet, M.

(2001). Numerical modelling of carbonate platforms and reefs:

approaches and opportunities. Energy Exploration & Exploitation, 19, 315-

345.

Daly, R.A. (1910) Pleistocene glaciation and the coral reef

problem. Am. J. Sci., 4, 297-308.

Daly, R.A. (1915) The glacial control theory of coral reefs.

Proceed. Am. Acad. Arts. Sci., 51, 155-207.

86

Darwin, C. (1842) The structure and Distribution of Coral Reefs. Smith, Elder

and Co., London, 214 pp.

David, T.W.E. and Sweet, G. (1904) The Geology of Funafuti. In :

The Atoll of Funafuti, pp. 61-88. Royal Society, London.

Davies, P.J. and Montaggioni, L.F. (1985). Reef growth and sea

level change : the environmental signature. Proceed. Fifth Intern. Coral

Reef Congr., Tahiti, 3, 477-511.

Delesalle, B. (1985). Mataiva Atoll, Tuamotu Archipelago. Proceed.

Fifth Intern. Coral Reef Congr., Tahiti,1, 269-322.

Demicco, R.V. and Hardie, L.A. (2002). The « carbonate factory »

revisited : a reexamination of sediment production functions used

to model deposition on carbonate platforms. J. Sedim. Res., 72, 849-

857.

Deneufbourg, G. (1969). Les forages de Mururoa. Cahiers du Pacifique,

13, 191-202.

87

Detrick, R.S. and Crough, S.T. (1978) Island subsidence, hot spots

and lithospheric thinning. J. Geophys. Res., 83, 1236-1244.

Dickinson, W.R. (2004) Impacts of eustasy and hydro-isostasy on

the evolution and landforms of Pacific atolls. Palaeogeography,

Palaeoclimatology, Palaeocology, 213, 251-269.

Dandonneau, Y. (1979) Concentrations en chlorophylle dans le

Pacifique Tropical sud-ouest: comparaison avec d’autres zones

océaniques. Oceanologica Acta, 2, 133-142.

Done, T. J. (1982) Patterns in the distribution of coral

communities across the central Great Barrier Reef. Coral Reefs, 1,

95-108.

Dufour, P., Charpy, L., Bonnet, S. and Garcia, N. (1999 a)

Phytoplankton nutrient control in the oligotrophic South Pacific

subtropical (Tuamotu archipelago). Marine Ecol. Progr. Ser., 179, 285-

290.

88

Dufour, P. and Berland, B. (1999 b) Nutrient control of

phytoplankton biomass in atoll lagoons and Pacific Ocean waters:

studies with factorial enrichment bioassays. J. Exp. Mar. Biol. Ecol., 234,

147-166.

Dullo, W.C. (2005) Coral growth and reef growth: a brief review.

Facies, 51, 33-48.

Dupuy, C., Vidal, P., Maury, R.C. and Guille, G. (1993) Basalts

from Mururoa, Fangataufa and Gambier islands (French Polynesia):

geochemical dependence on the age of the lithosphere. Earth Planet. Sc.

Letters, 117, 89-100.

Duncan, R.A., McDougall, I., Carter, R.M. and Coombs, D.S. (1974)

Pitcairn Island: another Pacific hot spot? Nature, 251, 679-682.

Ebren, P. (1996) Impact des variations rapides du niveau marin sur le

développement des atolls au Quaternaire: Mururoa (Polynésie Française)- Dynamique

89

récifale et diagenèse des carbonates. Unpubl. Ph.D. Thesis, University of

Aix-Marseille I, 310 pp.

Emery, K.C., Tracey, J. I., Jr and Ladd, H. S. (1954) Geology of

Bikini and nearby atolls. U.S. Geol. Survey, Prof. Paper 260-A, 265 pp.

Enos, P. (1991) Sedimentary parameters for computer modeling.

Bulletin of the Kansas Geological Survey, 233, 64-99.

Fairbridge, R.W. and Stewart Jr, H.B. (1960) Alexa Bank, a drowned

atoll on the Melanesian Border Plateau. Deep Sea Res., 7, 100-108.

Falkland, A.C. and Woodroffe, C.D. (1997) Geology and hydrogeology

of Tarawa and Christmas Island, Kiribati. In: Geology and Hydrogeology

of Carbonate Islands (Eds H.L. Vacher and T.M. Quinn), pp. 577-610,

Elsevier, Amsterdam.

Farrow, G.E. (1971) The climate of Aldabra Atoll. Philos. Trans. R. Soc.

London, Ser. B, 260, 67-91.

90

Faure, G. and Laboute, P. (1984) Formations récifales de l’atoll

de Tikehau (Tuamotu, Polynésie Française, Océan Pacifique)- 1.

Définition des unités récifales et distribution des principaux

peuplements de Scléractiniaires. Notes Doc. ORSTOM, 22, 108-136.

Fütterer, D.K. (1974) Significance of the boring sponge Cliona for

the origin of grained material of carbonate sediments. J. Sedim. Petrol.

44, 79-84.

Gaven, C. and Vernier, E. (1979) Datation Io-U de coraux et

paléodynamique du Pleistocène moyen des Iles Glorieuses (Canal du

Mozambique). Quaternaria, 21, 47-52.

Gillot, P.Y., Cornette, Y. and Guille, G. (1992) Age (K-Ar) et

conditions d’édification du soubassement volcanique de Mururoa

(Pacifique Sud). Comptes Rendus de l’Académie des Sciences, Paris,314, Sér.

II, 393-399.

Gischler, E. (2006) Sedimentation on Rasdhoo and Ari Atolls,

Maldives, Indian Ocean. Facies, 52, 341-360.

91

Gischler, E. (2007) Pleistocene facies of Belize barrier and atoll

reefs. Facies, 53, 27-41.

Gischler, E. and Hudson, J.H. (1998) Holocene development of three

isolated carbonate platforms, Central America. Marine Geology, 144,

333-347.

Gischler, E., Hudson, J.H. and Pisera, A. (2008) Late Quaternary

reef growth and sea level in the Maldives (Indian Ocean). Marine

Geology, 250, 104-113.

Gischler, E., Ginsburg, R.N., Herrle, J.O. and Prasad, S. (2010)

Mixed carbonates and siliciclastics in the Quaternary of southern

Belize: Pleistocene turning points in reef development controlled

by sea-level change. Sedimentology, 57, 1049-1058.

Granjeon, D. and Joseph, P. (1999) Concepts and applications of a

3D multiple lithology diffusive model in stratigraphic modeling.

In : Numerical experiments in Stratigraphy: Recent advances in Stratigraphic and

92

Sedimentologic Computer Simulations (Eds Harbaugh, J.W., Watney, W.L.,

Rankey, E.C., Slingerland, R., Goldstein, R.H. and Franseen, E.

J.), SEPM, Spec. Publ., 62, 197-210.

Granjeon, D., Masson, R. and Wolf, S. (2005) Modélisation

stratigraphique 3D en zones tectoniques complexes. Rapport IFP

58598.

Gray, S. C., Hein, J. R., Hausmann, R. and Radtke, U. (1992)

Geochronology and subsurface stratigraphy of Pukapuka and

Rakahanga atolls, Cook Islands: Late Quaternary reef growth and

sea level history. Palaeogeography, Palaeoclimatology, Palaeoecology, 91,

377-394.

Guille, G., Goutière, G. and Sornein, J.F. (1995) The Atolls of Mururoa

and Fangataufa (French Polynesia) –1- Geology, Petrology , Hydrogeology. Masson,

Paris, 161 pp.

Guyomard, T.S., Aissaoui, D. and McNeill, D.F. (1996)

Magnetostratigraphy dating of the uplifted atoll of Maré:

93

geodynamics of the Loyalty Ridge, SW Pacific. J.Geophys. Res., 101

(B1), 601-612.

Handford, R.C. and Loucks, R.G. (1993). Carbonate depositional

sequences and system tracks – responses of carbonate platforms to

relative sea-level changes. In : Carbonate Sequence Stratigraphy (Eds

Loucks, R.G. and Sarg, J.F.), Am. Assoc. Petrol. Geologists,

Memoir 57, 3-42.

Harmelin-Vivien, M. (1985) Takapoto Atoll, Tuamotu Archipelago.,

Tahiti, 1, 213-234.

Harris P.T. and Heap, A.D. (2009) Cyclone-induced net

sedimenttransport pathway on the continental shelf of tropical

Australia inferred from reef talus deposits. Cont. Shelf Res., 29,

2011-2019.

Hein, J.R., Gray, S.C. and Richmond, B.M. (1997) Geology and

hydrogeology of the Cook Islands. In: Geology and Hydrogeology of

94

Carbonate Islands (Eds H.L. Vacher and T.M. Quinn), pp. 503-536,

Elsevier, Amsterdam.

Herbert, T.D., Cleaveland-Peterson, L., Lawrence, K.T. and Liu, Z.

(2010) Topical ocean temperature over the past 3.5 million years.

Science, 328, 1530-1534.

Hill, J., Tetzlaff, D., Curtis, A. and Wood, R. (2009) Modeling

shallow marine carbonate depositional systems. Computers and

Geosciences, 35, 1862-1874.

Hill, J., Wood, R., Curtis, A. and Tetzlaff, D.M. (2012)

Preservation of forcing signals in shallow water carbonate

sediments. Sedim. Geol., 275-276, 79-92.

Hoffmeister, J.E. and Ladd, H.S. (1944) The antecedent-platform

theory. J. Geology, 52, 388-402.

Holcomb, R.T. and Searle, R.C. (1991). Large landslides from

oceanic volcanoes. Marine Geotechnology, 10, 19-32.

95

Hopley, D. (1982) The Geomorphology of the Great Barrier Reef: Quaternary

Development of Coral Reefs. Wiley-Interscience, New-York, 453 pp.

Hopley, D., Smithers, S.G. and Parnell, K.E. (2007) The

Geomorphology of the Great Barrier Reef: Quaternary Development of Coral Reefs.

Cambridge University Press, Cambrige, UK, 532 pp.

Hubbard, D. K., Zankl, H., Van Heerden, I. and Gill, I.P. (2005) .

Holocene reef development along the northeastern St. Croix shelf,

Buck Island, U.S. Virgin Islands. J. Sedim. Res., 75, 97-113.

Hughes, T.P. (1999) Off-reef transport of coral fragments at

Lizard Island, Australia. Marine Geology, 57, 1-6.

Jacobson, G., Hill, P.J. and Ghassemi, F. (1997) Geology and

hydrogeology of Nauru Island. In: Geology and Hydrogeology of Carbonate

Islands (Eds H.L. Vacher and T.M. Quinn), pp. 707-742, Elsevier,

Amsterdam.

96

James, N.P. and Ginsburg, R.N. (1979). The seaward margin of Belize and

Atoll Reefs. Intern. Assoc. Sedimentologists, Spec. Publ. 3,

Blackwell, London, 191 pp.

Johnson, H. (1961). Fossil algae from Eniwetok, Funafuti and Kita-

Daito-Jima. U.S. Geol. Survey, Prof. Paper, 206-Z, 908-950.

Jones, B., Ng, K.-C. and Hunter, I.G. (1997) Geology and

hydrogeology of the Cayman Islands. In : Geology and Hydrogeology of

Carbonate Islands (Eds H.L. Vacher and T.M. Quinn), pp. 299-325,

Elsevier, Amsterdam.

Jorry, S., Droxler, A.W. and Francis, J.M. (2010) Deepwater

carbonate deposition in response to re-flooding of carbonate bank

and atoll-tops at glacial terminations. Quat. Sc. Reviews, 29, 2010-

2026.

Keating, B.H. (1998). Side-scan sonar images of submarine

landslides on the flanks of atolls and guyots. Marine Geodesy, 21,

129-145.

97

Kikuchi, R.K.P. and Leao, Z.M.A.N. (1997) Rocas (South-western

equatorial Atlantic, Brazil): an atoll built primarily by

coralline algae. Proceed. Eighth Intern. Coral Reef Symp., Panama, 1, 731-

736.

Kleypas, J.A. (1997) Modeled estimates of of global reef habitat

and carbonate production since the last glacial maximum.

Paleoceanography, 12, 533-545.

Kleypas, J.A., McManus, J.W. and Meñez, L.A.B. (1999)

Environmental limits to coral reef development: where do we draw

the line ?. Am. Zool., 39, 146–159.

Koelling, M., Webster, J.M., Camoin, G., Iryu, Y., Bard, E. and

Seard, C. (2009) SEALEX – Internal reef chronology and virtual

drill logs from a spreadsheet-based reef growth model. Global and

Planetary Change, 66: 149-159.

98

Kuenen, P.H. (1933) Geology of Coral Reefs. Weten-schappelijke

Uitkomsten der Snellius-Expeditie, vol. 5, pt. 2. Utrecht, 125 pp.

Kuenen, P.H. (1947). Two problems of marine geology : Atolls and

canyons. Kon. Ned. Akad, Wet., Verh. (Tweede Sectie) Dl. XLIII, 3, 1-69.

Ladd, H. S., Ingerson, Earl, Townsend, R. C., Russell, Martin, and

Stephenson, H. K. (1953) Drilling at Eniwetok Atoll, Marshall

Islands. Am. Assoc. Petroleum Geologists Bull,. 37, 2257-2280.

Ladd, H. S., Tracey, J. I., Jr., and Gross, M. G. (1967) Drilling

on Midway Atoll, Hawaii. Science,156, 1088- 1094.

Ladd, H. S., Tracey, J. I., Jr., and Gross, M. G. (1970) Deep

drilling on Midway atoll. U.S. Geol. Survey, Prof. Paper 680-A, 22 pp.

Ladd, H. S. and Schlanger, S. O. (1960) Drilling operations on

Eniwetok Atoll. U.S. Geol. Survey, Prof. Paper 260-Y, 863-903.

99

Leclerc, A. M., Jean-Baptiste, P. and Texier, D. (1999) Density-

induced water circulation in atoll coral reefs: a numerical study.

Limn. Oceanogr., 44, 1268-1281.

Lincoln, J.M. and Schlanger, S.O. (1991) Atoll stratigraphy as a

record of sea level change: Problems and prospects. J.Geophys. Res.,

96(B4), 6727-6752.

Liu, J., Ye, Z., Han, C., Liu, X. and Qu, G. (1997) Meteoric

diagenesis in Pleistocene reef limestones of Xisha Islands, China.

J. Asian Earth Sci., 15, 465-476.

Liu, Z. and Herbert, T.D. (2004) High-latitude influence on the

eastern equatorial Pacific climate in the early Pleistocene epoch.

Nature, 427, 720-723.

Ludwig, K.R., Halley, R.B., Simmons, K.R. and Peterman, Z.E.

(1988) Sr isotope stratigraphy of Enewetak Atoll. Geology, 16, 173-

177.

100

Lyell, Ch. (1832). Principles of Geology, vol.2. John Murray, London,

330 pp.

Major, R.P. and Matthews, R.K. (1983) Isotopic composition of

bank-margin carbonates on Midway Atoll: amplitude constraint on

post-early Miocene eustacy. Geology, 11, 335-338.

Marshall J.F. and Jacobson G. (1985) Holocene growth of a mid-

Pacific atoll: Tarawa, Kiribati. Coral Reefs, 4, 11-17.

Mathieu, P.P., Deleersnijder, E. Cushman-Roisin, B., Beckers, J.-

M. and Bolding, K. (2002) The role of topography in small well-

mixed bays, with application to the lagoon of Mururoa. Contin. Shelf

Res., 22, 1379-1395.

Matsuda, F., Saito, M., Iwahashi, R., Oda, H. and Tsuji, Y.

(2004). Computer simulation of carbonate sedimentary and shallow

diagenetic processes. Am. Ass. Petrol. Geolog., Memoir 80, 365-382.

101

Matsukura, Y., Maekado, A., Aoki, H., Kogure, T. and Kitano, Y.

(2007) Surface lowering rates of uplifted limestone terraces

estimated from the height of pedestals on a subtropical island of

Japan. Earth Surface, Processes and Landforms, 32, 1110-1115.

Maugé, L.A., Ségoufin, J., Vernier, E. and Froget, C. (1982)

Géomorphologie et origine des bancs di Nord-Est du Canal du

Mozambique, Océan Indien Occidental. Mar. Geol., 47, 37-55.

McClymont, E.L. and Rosell-Mele, A. (2005) Links between the onset

of modern Walker circulation and the mid-Pleistocene climate

transition. Geology, 33, 389-392.

Medina-Elizalde, M., Lea, D.W. and Fantle, M.S. (2008).

Implications of sea water Mg/Ca variability for Plio-Pleistocene

tropical climate reconstruction. Earth Plan.Sc. Lett., 269, 584-594.

Miller, K.G., Kominz, M.A., Browning, J.V., Wright, J.D.,

Mountain, G.S., Katz, M.E., Sugarman, P.J., Cramer, B.S.,

102

Christie-Blick, N. and Pekar, S.F. (2005) The Phanerozoic record

of global sea-level change. Science, 310, 1293-1298.

Montaggioni, L.F. (1985) Makatea Island, Tuamotu Archipelago.

Proceed. Fifth Intern. Coral Reef Congress, Tahiti, 1, 103-158.

Montaggioni, L.F. (1988) Le soulèvement polyphasé d’origine

volcano-isostasique : clé de l’évolution post-oligocène des atolls

du nord-ouest des Tuamotus (Pacifique central). Comptes Rendus de

l’Académie des Sciences, Paris, t. 309, Série II, 1591-1599.

Montaggioni, L.F. (2005) History of Indo-Pacific coral reef

systems since the last glaciation : development patterns and

controlling factors. Earth Sci. Rev., 71, 1-75.

Montaggioni, L.F. (2011) Mururoa Atoll. In: Encyclopedia of Modern Coral

Reefs (Ed D. Hopley), pp. 713-716. Springer, Dordrecht.

Montaggioni, L.F., Gabrié, C., Naim, O., Payri, C., Richard, G.

and Salvat, B. (1987) The seaward margin of Makatea, an uplifted

103

carbonate island (Tuamotus, Central Pacific). Atoll Res. Bull., 299, 1-

18.

Montaggioni, L.F. and Camoin, G.F. (1997) Geology of Makatea

Island, Tuamotu Archipelago, French Polynesia. In: Geology and

Hydrogeology of Carbonate Islands (Eds H.L. Vacher and T.M. Quinn), pp.

453-474, Elsevier, Amsterdam.

Montaggioni, L.F. and Braithwaite, C.J.R. (2009) Quaternary Coral Reef

Systems: History, Development processes and controlling factors. Developments in

Marine Geology, vol. 5, Elsevier, Amsterdam, 532 pp.

Montaggioni, L.F., Cabioch, G., Thouveny, N., Frank, N., Sato, T.

and Sémah, A.-M. (2011). Revisiting the Quaternary development

history of the western New Caledonian shelf system: from ramp to

barrier reefs. Mar. Geol., 280, 57-75.

Morgan, K. and Kench, P. (2012) Export of reef-derived sediment on

Vabbinfaru reef platform, Maldives. Proceed. 12 th Intern Coral Reef Symp.,

Cairns, Australia, 1A, 1-5.

104

Ohde, S. and Elderfield, H. (1992) Strontium isotope stratigraphy

of Kita-Daito-Jima Atoll, North Philippine Sea : Implications for

Neogene sea-level and tectonic history. Earth and Planetary Science Letters,

113 : 473-486.

Ohde, S., Greaves, M., Masuzawa, T., Buckley, H. A., Van Woesik,

R., Wilson, P. A., Pirazzoli, P. A. and Elderfield, H. (2002) The

chronology of Funafuti Atoll: revisiting an old friend.

Philosophical Transactions of the Royal Society, London, A458, 2289-2306.

Ota, Y. (1938) Cores from the test drilling on Kita-Daito-Jima.

Examination, chemical analyses, and microscopic study of the Daito

limestone. Institute Geol. and Paleontology, Tohoku Imp. Univ. Contrib., number

30, 25 pp.[In Japanese].

Pandolfi, J. (1995) Geomorphology of the Pleistocene uplifted

atoll at Henderson Island, Pitcairn Group. Biologic. J. Linnean Soc., 56,

3, 63-77.

105

Parsons, B. and Sclater, J.G. (1977) An analysis of the variation

of ocean floor bathymetry and heat flow with age. J.Geophys. Res.,

82, 803827.

Paterson, R.J., Whitaker, F.F., Jones, J.D., Smart, P.L., Waltham,

D. and Felce, G. (2006) Accommodation and sedimentary architecture

of isolated icehouse carbonate platforms : insights from forward

modeling with CARB3D. J. Sedim. Res., 76, 11

Paulay, G. and McEdward, L.R. (1990) A simulation model of island

reef morphology : the effects of sea level fluctuations, growth,

subsidence and erosion. Coral Reefs, 9, 51-62.

Paulay, G. and Spencer, T. (1992) Niue Island: geologic and

faunistic history of a Pliocene atoll. Pacific Sci. Assoc. Information Bull.,

44, 21-23.

Perrin, C. (1989) Rôle des organismes dans l’édification et l’évolution de l’atoll de

Mururoa (Polynésie Française). Unpubl. Ph.D. thesis, University of Paris-

Orsay, 301 pp.

106

Perrin, C. (1990) Genèse de la morphologie des atolls : le cas de

Mururoa (Polynésie Française). Comptes Rendus de l’Académie des Sciences,

Paris, 311, Série II, 671-678.

Pirazzoli, P.A, Montaggioni, L.F., Vergnaud-Grazzini, C. and

Saliège, J.F. (1987) Late Holocene sea-levels and coral reef

development in Vahitahi Atoll, eastern Tuamotu Islands, Pacific

Ocean. Marine Geology, 78, 405-116.

Pirazzoli, P.A. and Montaggioni, L.F. (1988 a) Late Holocene sea-

level changes in French Polynesia. Palaeogeography, Palaeoclimatology,

Palaeoecology, 68, 153-175.

Pirazzoli, P.A., Koba, M., Montaggioni, L.F. and Person, A. (1988

b) Anaa (Tuamotu Islands, central Pacific), an incipient rising

atoll. Marine Geology, 82, 261-269.

Pirazzoli, P.A., Kaplin, P.A. and Montaggioni, L.F. (1990)

Differential vertical crustal movements deduced from Late Holocene

107

coral-rich conglomerates: Farqhar and St Joseph Atolls

(Seychelles, Western Indian Ocean). J. Coastal Res., 6, 381-389.

Purdy, E.G. (1974) Reef configurations: cause and effect. In : Reefs

in Time and Space (Ed L.F. Laporte). Soc. Econ. Paleont. Mineral.

Special Publ.,18, 9-76.

Purdy, E. G. and Bertram, G. T. (1993) Carbonate Concepts from

the Maldives, Indian Ocean. Am. Assoc. Petrol. Geol., Studies in Geology, 34:

1-56.

Purdy, E.G. and Winterer, E.L. (2001) Origin of atoll lagoons.

Geol. Soc. Am. Bull., 113, 837-854.

Purdy, E.G., Gischler, E. and Lomando, A.J. (2003) The Belize

margin revisited. 2. Origin of Holocene antecedent topography.

Intern. J. Earth Sci., 92, 552-572.

Purdy, E.G. and Gischler, E. (2005) The transient nature of the

empty bucket model of reef sedimentation. Sed.Geol., 175, 35-47.

108

Quinn, T.M. (1991a). Meteoric diagenesis of Post-Miocene

limestones on Enewetak Atoll. J. Sedim. Petrol., 61, 681-703.

Quinn, T.M. (1991b) The history of post-Miocene sea-level change:

inference from stratigraphic modeling of Enewetak Atoll. J. Geophys.

Res., 96 (B4), 6713-6725.

Quinn, T.M. and Matthews, R.K. (1990) Post-Miocene diagenetic

and eustatic history of Enewetak Atoll: model data and

comparison. Geology, 18, 942-945.

Quinn, T.M., Lohmann, K.C. and Halliday, A.N. (1991) Sr isotopic

variation in shallow water carbonate sequences: stratigraphic,

chronostratigraphic, and eustatic implications of the record at

Anewetak Atoll. Paleoceanography, 6, 371-385.

Quinn, T.M., Taylor, F.W. and Halliday, A.N. (1994) Strontium-

isotopic dating of neritic carbonates at Bougainville Guyot (Site

109

831), New Hebrides Island Arc. Proceed. Ocean Drilling Program, Scient.

Results, vol. 134, 89-98.

Quinn, T.M. and Saller, A.H. (1997) Geology of Anewatak Atoll,

Republic of the Marshall Islands. In: Geology and Hydrogeology of

Carbonate Islands (Eds H.L. Vacher and T.M. Quinn), pp. 637-666,

Elsevier, Amsterdam.

Rabineau, M., Berné, S., Aslanian, D., Olivet, J.L., Joseph, P.,

Guillocheau, F., Bourillet, J.F., Ledrezen, E. and Granjeon, D.

(2005) Sedimentary sequences in the Gulf of Lion: a record of

100,000 years climatic cycles. Mar. Petrol. Geol., 22, 775–804.

Rancher, J. and Rougerie, F. (1994) L’environnement océanique de

l’Archipel des Tuamotu (Polynésie Française). Oceanologica Acta, 18,

43-60.

Raymo, M.E., Ganley, K., Carter, S., Oppo, D.W. and McManus, J.M.

(1998) Millenial-scale instability during the early Pleistocene

epoch. Nature, 392, 699-702.

110

Repellin, P. (1975) Contribution à l’étude pétrologique d’un récif corallien: le

sondage “Colette”, Atoll de Mururoa (Polynésie Française). Unpubl. Ph.D. thesis,

University of Paris 6, 108 pp.

Rougerie, F., Gros, R., and Bernadac, M. (1980) Le lagon dec

Mururoa (Archipel des Tuamotu): esquisse des caractéristiques

hydrologiques et échange avec l’océan. Office de la Recherche Scientifique et

Technique d’Outre-Mer, Notes et Documents d’Océanographie, 80/16, 28 pp.

Schefus, E., Sinninghe Damste, J.S. and Jansen, J.H.F. (2004)

Forcing of tropical Atlantic sea surface temperature during the

mid-Pleistocene transition. Paleoceanography, 19, PA4029, doi:

10.1029/2003PA000892.

Royal Society (1904) The Atoll of Funafuti. Royal Soc. London, 428 p.

Schlager, W. (1993). Accommodation and supply – a dual control on

stratigraphic sequence. Sedimentary Geology, 86, 111-136.

111

Schlager, W. (2005) Carbonate Sedimentology and Sequence Stratigraphy.

Concepts in Sedimentology and Paleontology Series , 8, SEPM,

Tulsa, Oklahoma, 200 pp.

Schlager, W. and Warrlich, G. (2009) Record of sea-level fall in

tropical carbonates. Basin Res., 21, 209-224.

Schlager, W., Marsal, D., Van der Geest, P.A.G. and Sprenger, A.

(1998) Sedimentation rates, observation span, and the problem of

spurious correlation. Mathematical Geology, 30, 547-556.

Seard, C., Borgomano, J., Granjeon, D. and Camoin, G.F. (2013)

Impact of environmental parameters on coral reef development and

drowning: Forward modelling of last deglacial reefs from Tahiti

(French Polynesia; IODP Expedition #310), Sedimentology, doi:

10.1111/sed.12030.

Siddall, M., Chappell, J. and Potter, E.K. (2006) Eustatic sea

level during past interglacials. In : The Climate of Past Interglacial (Eds

F. Sirocko, M. Clausen, M.F. Sanchez-Goni and T. Litt), Developm.

112

Quaternary Sci., 7, pp. 75-92. Elsevier , Amsterdam.

Stearns, H.T. (1946). An integration of coral reefs hypotheses.

Am. J. Sci., 244, 245-262.

Steers, J.A. and Stoddart, D.R. (1977). The origin of fringing

reefs, barrier reefs and atoll. In: Biology and Geology of Coral Reefs ,

Geology 2 (Eds O.A. Jones and R. Endean), pp. 212-227. Academic

Press, New-York.

Stirling, C.H., Esat, T.M., Lambeck, K., McCulloch, M.T., Blake,

S. G., Lee, D.C. and Halliday, A.N., (2001). Orbital forcing of

the marine isotope stage 9 interglacial. Science, 291, 290-293.

Stoddart, D.R. (1969). Ecology and morphology of recent coral

reefs. Biological Reviews, 44, 433-498.

Stoddart, D. R., Spencer, T., and Scoffin, T. P. (1985) Reef

growth and karst erosion on Mangaia, Cook Islands: a

reinterpretation. Z. Geomorph., N.F. Suppl-bd., 57, 121-140.

113

Stoddart, D.R., Woodroffe, C.D. and Spencer, T. (1990) Mauke,

Mitiaro and Atiu : geomorphology of makatea islands in the

southern Cook. Atoll Res. Bull., 341, 1-65.

Stone, J., Allan, G.L. Fifield, L.K., Evans, J.M. and Chivas, A.R.

(1994) Limestone erosion measurements with cosmogenic chlorine-36

in calcite – preliminary resutls from Australia. Nuclear Instruments

and Methods in Physics Res., Sect.B, Beam Interactions with Materials and Atoms, 92,

311-316.

Suzuki, Y., Iryu, Y., Nambu, A., Inagaki, S. and Ozawa, S. (2007)

Plio-Pleistocene reef evolution of Kita-Daito-Jima, Japan. In :

Fossil Corals and Sponges (Eds B. Hubmann and W. E. Piller).

Schriftenreihe der Erdwissenschaftlichen Kommission, 17, 493-506.

Szabo, B. J., Tracey, J. I., and Goter, E. R. (1985) Ages of

subsurface stratigraphic intervals in the Quaternary of Eniwetak

Atoll, Marshall Islands. Quaternary Research, 23, 54–61.

114

Tartinville, B. and Rancher, J. (2000) Wave-induced flow over

Mururoa atoll reef. J.Coastal Res., 16, 776-781.

Tartinville, B., Deleersnijder, E. and Rancher, J. (1997) The

water residence in the Mururoa atoll lagoon : sensitivity analysis

of a three-dimensional model. Coral Reefs, 16, 193-203.

Taylor, G.R. (1973) Preliminary observations on the structural

history of Rennell Island, South Solomon Sea. Bull. Geol. Soc. Am., 84,

2795-2806.

Toomey, M., Ashton, A.D. and Perron, J.T. (2013) Profiles of

ocean island coral reefs controlled by sea-level history and

carbonate accumulation rates. Geology, doi:10.1130/G34109.1

Trichet, J., Repellin, P. and Oustrière, P. (1984) Stratigraphy

and subsidence of the Mururoa Atoll (French Polynesia). Marine

Geology, 56, 241-257.

Trudgill, S.T. (1979) Surface lowering and landform evolution on

115

Aldabra. Philos. Trans. R. Soc. london, Ser. B, 286, 35-45.

Veron, J.E.N. (2000) Corals of the World. Australian Institute of

Marine Science and CSIRO Publishing, Townsville, Australia, Vol.

1, 463 pp; Vol. 2, 429 pp; Vol. 3, 490 pp.

Vézina, J., Jones, B. and Ford, D. (1999) Sea-level highstands

over the last 500,000 years : evidence from the Ironshore

Formation on Grand Cayman, British West Indies. J. Sed. Res., 69,317-

327.

Wallace, C.C. (1999) Staghorn corals of the World : A revision of the world genus

Acropora (Scleractinia ; Astrocoeniina ; Acroporidae) worldwide,with emphasis on

morphology, phylogeny and biogeography. CSIRO Publishing, Melbourne,

Australia, 421 pp.

Warrlich, G.M.D., Waltham, D.A. and Bosence, D.W.J. (2002)

Quantifying the sequence stratigraphy and drowning mechanisms of

atolls using a new 3-D forward stratigraphic modelling program

(Carbonate 3D). Basin Research, 14; 379-400.

116

Webster, J.M. and Davies, P.J. (2003) Coral variations in two deep

drill cores from the Northern Great Barrier Reef: significance for

the Pleistocene development of the Great Barrier Reef. Sedim. Geol.,

159, 61-80.

Webster, J. M., Wallace, L. M., Clague, D. A. and Braga, J. C.

(2007) Numerical modeling of the growth and drowning of Hawaiian

coral reefs during the last two glacial cycles (0–250 kyr).

Geochemistry. Geophysics. Geosystems, 8, Q03011,

doi:10.1029/2006GC001415.

Wheeler, Ch. and Aharon, P. (1991) Mid-oceanic carbonate platforms

and oceanic dipsticks: examples from the Pacific. Coral Refs, 10,

101-114.

Wheeler, Ch. and Aharon, P. (1997) Geology and hydrogeology of

Niue. In : Geology and Hydrogeology of Carbonate Islands (Eds H.L. Vacher

and T.M. Quinn), pp. 537-564, Elsevier, Amsterdam

117

Woodroffe, C. D., Stoddart, D. R., Spencer T., Scoffin, T. P. and

Tudhope, A. (1990). Holocene emergence in the Cook Islands, South

Pacific. Coral Reefs, 9, 31-39.

Woodroffe, C.D. and Falkland, A.C. (1997) Geology and hydrogeology

of the Cocos (Keeling) Islands. In : Geology and Hydrogeology of

Carbonate Islands (Eds H.L. Vacher and T.M. Quinn), pp. 885-908,

Elsevier, Amsterdam

Woodroffe, C. D. and McLean, R. F. (1998) Pleistocene morphology

and Holocene emergence

of Christmas (Kirimati) Island, Pacific Ocean. Coral Reefs, 17, 235-

248.

Woodroffe, C.D., Kennedy, D.M., Jones, B.G. and Phipps, C.V.G.

(2004) Geomorphology and Late Quaternary development of Middleton

and Elizabeth Reefs. Coral Reefs, 23, 249-262.

Woodroffe, C.D., Biribo, N. (2011). Atolls. In: Encyclopedia of Modern

Coral Reefs (Ed D. Hopley), pp. 51-71. Springer, Dordrecht.

118

Yamamoto, K., Iryu, Y., Sato, T., Chiyonobu, S., Sagae, K. and

Abe, E. (2006) Responses of coral reefs to increased amplitude of

sea-level changes at the Mid-Pleistocene Climate Transition.

Palaeogeogr., Palaeoclim., Palaeoecol., 241, 160-176.

Yamano, H., Kayanne, H., Matsuda, F. and Tsujii, Y. (2002)

Lagoonal facies, ages and sedimentation in three atolls in the

Pacific. Marine Geology, 185, 233-247

Ye, Y., He, J. and Diao, S. (1993) ESR dating of coral reefs in

the South China Sea. China J. Oceanol. Limnol., 11, 207-214.

Yubo, M., Shiguo, W., Fuliang, L., Dongdong, D., Qiliang, S.,

Yianto, L. and Mingfing, G. (2011). Seismic characteristics and

development of the Xisha carbonate platforms, northern margin of

the South China Sea. J. Asian Earth Sciences, 40, 770-783.

Zhao, H., Sun, Z., Zhu, Y. and Wen, X. (1996) Quaternary

environmental changes as recorded in coral reefs of Nansha

119

Islands, South China Sea. In: Advances in Solid Earth Sciences (Eds Pang,

Z., Zhang, J. and Sun, J.), pp. 99-108, Science Press, Bejing.

120

Figure Captions

Figure 1. Maps illustrating the position of Murururoa Atoll in the

central south Pacific Ocean and the main topographical features of

the atoll with location of previous drillhole sites (open

circles).

Figure 2. Idealized, WSW to ENE-oriented cross-section through

Murururoa Atoll, showing the internal structure and stratigraphy

of the Quaternary carbonate pile beneath the outer rim and the

lagoon. The location and alignment of both vertical and oblique

drillholes are indicated, together with the radiometric ages of

coral samples extracted from the inclined cores (modified from

Perrin 1989; Ebren, 1995; Camoin et al., 2001).

Figure 3. Relative sea-level curve (“accommodation” curve) for the

past 1.8 Ma used as a primary input variable in the model. This

curve was constructed from the eustatic sea-level curve of Miller

et al. (2005) corrected by a linear subsidence rate of 105 m/Ma.

121

Figure 4. Relationship between the rates of carbonate production

and water depth at different time intervals (1.80-0.80 Ma; 0.80-

0.50 Ma; 0.50 Ma-present) on Mururoa Atoll. The rates decrease

exponentially as depth increases. The depth variables which define

the shape-fitted curves are: 0-25 m, 25-40 m, 40-65 m, and >65 m.

The curves given herein refer to production rates identified as

providing the best-estimate development scenario.

Figure 5. Model outputs illustrating the effect of increasing

subsidence rates (from 25 m/Ma to 125 m/Ma) on the predicted

morphological and stratigraphical attributes of Mururoa Atoll.

Production rates of 0.5 to 0.8, 0.8 to 2.5, and 2.5 mm/yr were

used as best “base-cases” for the time intervals of 1.8-1.0 Ma,

1.0-0.50 Ma and 0.50 Ma-present respectively. Each value of the

simulated production rates is highest in the upper 6 m of the

water column. Each model covers the entire development history of

1.80 million years. Each color refers to a determined marine

isotope stage (MIS 63 to 1).

122

Figure 6. Model outputs illustrating the effect of changing

carbonate production rates on the predicted morphological and

stratigraphical attributes of Mururoa Atoll. The curves relate to

the production rates prescribed in each run. A subsidence rate of

105 m/Ma was used as the”best-case” over the entire 1.80 Ma

period. Each value of the simulated production rates is highest

in the upper 6 m of the water column. Each color refers to a

determined marine isotope stage (MIS 63 to 1).

Figure 7. Best-estimate scenario outputs, showing platform cross-

sections at successive stages of atoll development, from 1.0 Ma to

present. The values of production rates identified as resulting in

the best-estimate model, increase from 0.5 to 0.8 mm/yr over the

1.8-1.0 Ma interval, from 0.8 to 2.5 mm/yr over the 0.8 to 0.5 Ma

interval and keep constant at 2.5 mm/yr for the period of 0.50 Ma

to present. Each value of the simulated production rates is

highest in the upper 6 m of the water column. Each color refers

to a determined marine isotope stage (MIS 63 to 1).

123

Figure 8. Major steps in the development history of Mururoa Atoll

over the past 1.8 million years. Three successive sedimentary

systems are postulated to have functioned in relation to changes

in the amplitude and frequency of sea-level cycles.

Tables

Table 1. Investigated atolls and atoll-shaped, high carbonate

islands worldwide.

Table 2. Major morphometric and stratigraphic attributes of

Mururoa Atoll based on field and drilling surveys and used as

primary input variables.

Table 3. Additional input variables and values used to test the

model outputs.

Table 4. Predicted morphometric and stratigraphic attributes

derived from testing increasing values of subsidence rate. Each

124

value results in a end-member scenario. Only running the value of

105m/Ma ends up with the best estimate model, in fully agreement

between observational and predicted data.

Table 5 : Maximum thickness (in metres) of MIS 1-to-MIS 13 reef units beneath the outer-rim

surface and within the margin pile.

125