the response of coral reefs to sea level change

THE RESPONSE OF CORAL REEFS TO SEA LEVEL CHANGE : EVIDENCE FROM THE RYUKYU ISLANDS AND THE GREAT BARRIER REEF

Jody Michael Webster

A thesis submitted in fulfillment of the requirements for the degree of Doctorate of Philosophy

School of Geosciences

University of Sydney August, 1999

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Unless otherwise acknowledged, all data and interpretations presented in this thesis are my own work.

Jody Michael Webster August, 1999

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ABSTRACT This thesis defines the response in two time frames, of individual reefs and coral reef ecosystems to sea-level change, through the bio-geological analysis of such reefs, on both active and passive margins. The raised Holocene reefs at Kikai-jima, Japan (Central Ryukyu Islands, ie. active margin) were examined for horizontal and vertical variation in exposed sections, and in drill core to determine the biological response of reefs to sea level fall. Holocene palaeoclimatic signals from a massive fossil coral at Kikai-jima were also investigated and their implications for reef growth and palaeoceanography discussed. Finally, two high-resolution cores from the Northern Great Barrier Reef (ie. passive margin) were examined to determine the biological response of reefs to repeated sea-level rise and fall over the last ~350 ky.

Kikai-jima, an island of some 40 square km, is fringed by exposed terraces of Holocene reefs, formed by periodic local tectonic uplift associated with regional subduction/collision. The terraces form four topographically distinct features (TI-IV) around the island and represent reefs that grew to sea-level at 9000-6065 y BP, 60653390 y BP, 3790-2630 y BP, and 2870 to 1550 y BP. The modern reef terrace has been growing since approximately 1550 y BP. The reef terraces were uplifted sequentially around 6050 y BP (4 m), 3390-3790 y BP (2.5 m), 2630-2870 y BP (1 m) and 1550 y BP (2.5 m). Five locations were studied to define reef development in response to rapid periodic relative sea-level fall and different stillstand recovery periods. Thirty coral genera and seventy species were recorded from four distinct shallow reef flat to upper reef slope, and one deeper reef slope coral assemblage. Significant horizontal variations in total coral abundance, genera number, diversity, and the coverage density of Acropora sp. and Faviids occur both within and between the terraces. Stratigraphically, drill core and outcrop data record shallowing upward sequences characterised by tabulate Acropora sp. overlying massive Porites sp. and Faviids. These biological variations represent growth strategies responding to initial colonisation, episodic perturbation (relative sea-level fall) and differing recovery times during stillstands, and indicate a reef ecosystem stable and strong enough to recover after substantial perturbations. However, this study suggests that relatively small geological changes have had substantial biological effects, and modelling indicates that such changes would have been more profound had other factors, such

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as substrate angle or the amplitude of sea-level fall varied more dramatically. Seasurface temperature (SST) derived from a fossil coral (60 year isotope record) at Kadon (TII, 3.8 ka) defines another potential factor influencing reef growth. During two periods (years 1-34, years 55-59) the SST threshhold for reef development (< 18 o

C, Veron and Minchin, 1992) was breached consistently during the winter months.

Comparison with biological data, suggests there may be an association between the biological variation recorded within the TII slope interval and the cold SST periods defined by the isotope record. It is possible that the TII reef experienced limited reef growth and even extensive coral mortality during these cool water periods. Further, based on the significantly lower coverage, abundance and diversity recorded in TIII at Kadon (compared with TII) it is predicted that SST's were substantially lower during development of TIII. In terms of palaeoceanography, these rapid and major SST fluctuations may represent significant shifts in the direction/position and strength of the Kuroshio Current. Two boreholes were drilled through reefs in the Great Barrier Reef on the continental shelf east of Cooktown, Australia. Boulder Reef (inner shelf) is composed of six thin reefs (R1-R6). The upper section (0-32 m) is a carbonate dominated section, composed of four reefs (R1-R4), overlying a siliciclastic mud dominated section (3286 m) and two further thin reefs (R5-R6). An outer shelf sequence from Ribbon Reef 5 is composed of an upper reef dominated section (0-96 m), a middle rhodolith dominated section (96-156 m) and a lower skeletal grainstone/packstone dominated section (156-210 m). Six reefs (R1-R6) comprise the upper section and are separated by boundaries defined by soil horizons, changes in coral and coralline assemblages and/or styles of diagenetic alteration. Two distinct coral assemblages and their palaeoenvironmental settings are identified in the Ribbon Reef 5 core, while Boulder Reef is dominated by a single coral assemblage type. In Ribbon Reef 5 the assemblages are repeated throughout the upper reef dominated section, with some individual reef sequences recording assemblage variations, while others record a single coral assemblage. The repeated occurrence of similar coral assemblages suggests that coral reef community structure has remained stable during the growth of the Great Barrier Reef despite major environmental fluctuations. When this coral assemblage data is tested against and combined with previously published coralline algal data (Braga and Aguirre 1997), there is substantial agreement in defining

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palaeoenvironmental variation in the Great Barrier Reef during the late Pleistocene. Based on all available lithological, coral and coralline data and comparison with the modern Great Barrier Reef, a model of Pleistocene reef development in response to repeated sea-level rise and fall is proposed. The model defines six stacked, backstepping, high energy reefs and their predicted facies variations. A quantitative reconstruction of their development defines one possible scenario for the Pleistocene evolution of the Great Barrier Reef. This reconstruction suggests; (1) the oldest reef (R6) probably developed during the very earliest part of the transgression in Stage 9 and drowned, producing only a very thin reef, and (2) in addition to the highstand (R3-R1) growth postulated by Davies et al. (1988), two periods of interstadial reef growth may also be defined (R5 and R4). Individual reef thickness and boundaries predicted by the reconstruction correlate reasonably well with the observed Ribbon Reef 5 stratigraphy.

Finally, incorporating and extending the ideas raised by the Kikai-jima and Great Barrier Reef data, a series of models defining the expected morphologic and facies variations under different but realistic end member sea-level scenarios are proposed. The models confirm the importance of basement substrate angle and the rate, duration and amplitude of sea-level in controlling the morphologic and facies response of coral reefs. Further, they predict how reefs have responded to sea-level changes in the past and how they might respond in the future. To this end, the forereef slope off the front of Ribbon Reef 5 is identified as a key location for further testing the models proposed in this thesis.

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TABLE OF CONTENTS ACKNOWLEDGEMENTS ABSTRACT LIST OF FIGURES LIST OF TABLES

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CHAPTER 1 - INTRODUCTION AND BACKGROUND 1.1 1.2 1.3 1.4

INTRODUCTION AIMS AND OBJECTIVES DATA COLLECTION AND STORAGE PREVIOUS WORK AND BACKGROUND INFORMATION 1.4.1 Active margins 1.4.1.1 Uplifted reefs 1.4.1.2 Causes of raised reefs 1.4.2 Passive margins 1.4.2.1 Subsiding reefs

PART 1.

2 2 3 4 4 4 5 6 6

REEFS AND SEA-LEVEL FALL - KIKAI-JIMA

CHAPTER 2 – MODERN AND GEOLOGICAL SETTING OF KIKAI-JIMA 2.1 2.2

INTRODUCTION KIKAI-JIMA (MODERN AND GEOLOGICAL SETTING) 2.2.1 Climate and oceanography 2.2.2 Geology 2.2.3 Coral communities, assemblages and zonation - modern and fossil (Ryukyu Islands) 2.2.4 Holocene raised terraces at Kikai-jima 2.2.4.1 Terrace composition 2.2.4.2 Morphology and structure 2.2.4.3 Terrace age ranges vs growth ranges 2.2.4.4 Local tectonic uplift

8 8 8 10 12 14 14 14 15 16

CHAPTER 3 - HORIZONTAL CORAL VARIATIONS IN HOLOCENE TERRACES AROUND KIKAI-JIMA 3.1 3.2

3.3

INTRODUCTION METHODS 3.2.1 Site selection and description 3.2.2 Topographic profiles 3.2.3 Linear transect method RESULTS 3.3.1 Coral taxonomy

31 31 31 32 32 34 34

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3.4

3.5

3.3.2 Holocene reef composition 3.3.2.1 Kadon 3.3.2.2 Shidooke 3.3.2.3 Nakaguma 3.3.2.4 Nakazato 3.3.2.5 Araki 3.3.3 Sample size bias 3.3.4 Temporal variations between terraces 3.3.4.1 Kadon 3.3.4.2 Shidooke 3.3.4.3 Nakaguma 3.3.4.4 Nakazato 3.3.4.5 Araki DISCUSSION 3.4.1 Summary of temporal variation 3.4.2 Spatial variations between sites 3.4.3 Coral assemblages, their distribution and palaeoenvironmental settings SUMMARY AND CONCLUSIONS

34 35 37 39 41 43 45 46 47 48 49 49 50 51 51 52 54 56

CHAPTER 4 - VERTICAL CORAL VARIATIONS IN HOLOCENE TERRACES AROUND KIKAI-JIMA 4.1 4.2

4.3

4.4

4.5

INTRODUCTION METHODS 4.2.1 Vertical quadrat method 4.2.2 Data analysis RESULTS 4.3.1 Kadon 4.3.2 Shidooke 4.3.3 Nakaguma 4.3.4 Nakazato 4.3.5 Araki DISCUSSION 4.4.1 Patterns of vertical reef growth 4.4.2 Lateral variations in faunal patterns within and between the terraces SUMMARY AND CONCLUSIONS

107 107 107 108 108 108 113 117 121 126 129 129 134 136

CHAPTER 5 - SUB-SURFACE (DRILL CORE) HOLOCENE CORAL VARIATION AT KIKAI-JIMA 5.1 5.2

INTRODUCTION METHODS 5.2.1 Location and drill procedure

165 165 165

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5.3

5.4

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RESULTS 5.3.1 Holocene sequence - internal structure and morphology 5.3.2 Radiocarbon data - reef age and vertical accretion rates 5.3.3 Coral variation 5.3.4 Sedimentary facies DISCUSSION 5.4.1 Coral assemblage distribution 5.4.2 Vertical accretion 5.4.3 Palaeowater depth 5.4.4 Growth strategies SUMMARY AND CONCLUSIONS

166 166 166 167 167 168 168 169 171 173 173

CHAPTER 6 – CAUSES OF TEMPORAL AND SPATIAL BIOLOGICAL CHANGE IN THE KIKAI-JIMA TERRACES 6.1 6.2 6.3 6.4 6.5 6.6

INTRODUCTION TEMPORAL BIOLOGIC CHANGE - POSSIBLE CAUSES SPATIAL BIOLOGIC CHANGE - POSSIBLE CAUSES MODEL PARAMETERS AND ASSUMPTIONS MODEL OF FRINGING REEF GROWTH IN RESPONSE TO PROGRESSIVE SEA-LEVEL FALL SUMMARY AND CONCLUSIONS

181 181 183 185 186 187

CHAPTER 7 – HIGH-RESOLUTION ISOTOPIC RECORDS FROM KIKAI-JIMA 7.1 7.2

7.3

7.4

INTRODUCTION METHODS 7.2.1 Drilling technique and site location 7.2.2 Stable isotope sampling and analysis RESULTS 7.3.1 Radiocarbon age 7.3.2 Coral chronology and growth rates 7.3.3 Oxygen isotope record (δ18O) 7.3.4 Carbon isotope record (δ13C) 7.3.5 Comparison of coral growth rates with the isotopic record DISCUSSION AND INTERPRETATIONS 7.4.1 Seasonal isotopic variations 7.4.2 Inter-annual isotopic variations 7.4.3 Sea surface temperatures (SST) in the late Holocene 7.4.3.1 Coral thermometer 7.4.3.2 Sources of error 7.4.3.3 Interpretation 7.4.3.4 Implications for reef growth

192 193 193 193 194 194 194 195 196 198 198 198 200 204 204 204 204 206

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7.5

7.4.3.5 Implications for palaeoceanography SUMMARY AND CONCLUSIONS

PART 2.

207 210

REEFS AND SEA-LEVEL RISE - GREAT BARRIER REEF

CHAPTER 8 – REEF GROWTH ON THE GREAT BARRIER REEF 8.1 8.2

INTRODUCTION MODERN AND GEOLOGICAL SETTING OF THE NORTHERN GREAT BARRIER REEF 8.2.1 Climate and oceanography 8.2.2 Geology 8.2.3 Reef growth in the Great Barrier Reef during the Holocene

224 224 224 225 226

CHAPTER 9 – PLEISTOCENE REEF GROWTH IN THE GREAT BARRIER REEF 9.1 9.2 9.3

9.4 9.5 9.6 9.7

9.8.

9.9

INTRODUCTION DRILLING THE PLEISTOCENE GREAT BARRIER REEF SITE LOCATION AND DESCRIPTION 9.3.1 Ribbon Reef 5 9.3.2 Boulder Reef PLEISTOCENE DRILLING TECHNIQUE CORE LITHOLOGY AND STRATIGRAPHY CORAL VARIATION IN THE RIBBON REEF 5 AND BOULDER REEF CORES RESULTS 9.7.1 Coral assemblages and palaeoenvironmental significance 9.7.2 Distribution of coral assemblages 9.7.2.1 Ribbon Reef 5 9.7.2.2 Boulder Reef DISCUSSION 9.8.1 Coral assemblage variation through the Pleistocene 9.8.2 Testing the coral assemblage data against the coralline algal record through the Pleistocene 9.8.3 Palaeoenvironmental model through the Pleistocene SUMMARY AND CONCLUSIONS

235 235 236 236 239 240 241 241 242 242 243 243 245 246 246 249 251 252

CHAPTER 10 – MODEL OF PLEISTOCENE REEF GROWTH ON A PASSIVE MARGIN 10.1

INTRODUCTION

267

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10.2 10.3 10.4

10.5 10.6

PLEISTOCENE MODEL OF REEF GROWTH IN RESPONSE TO REPEATED SEA-LEVEL RISE AND FALL RECONSTRUCTION PARAMETERS AND ASSUMPTIONS RECONSTRUCTION OF PLEISTOCENE REEF DEVELOPMENT IN THE GREAT BARRIER REEF

TESTING THE MODEL AND RECONSTRUCTION AGAINST THE DRILL CORE DATA SUMMARY AND CONCLUSIONS

PART 3.

267 268 272

274 276

REEF GROWTH AND SEA-LEVEL CHANGE

CHAPTER 11 – REEF GROWTH IN RESPONSE TO SEA-LEVEL RISE AND FALL 11.1 11.2 11.3 11.4

11.5

11.6

INTRODUCTION REEF GROWTH IN RESPONSE TO SEA-LEVEL FALL : EVIDENCE FROM KIKAI-JIMA REEF GROWTH IN RESPONSE TO SEA-LEVEL RISE AND FALL : EVIDENCE FROM GREAT BARRIER REEF MAJOR FACTORS AFFECTING REEF GROWTH IN RESPONSE TO SEA LEVEL RISE AND FALL 11.4.1 Summary of major factors 11.4.2 Relative sea-level change (rates and amplitude of change) 11.4.3 Substrate character (slope and depth) 11.4.4 Geological time 11.4.5 Oceanography 11.4.6 Biological factors (recruitment source) MODEL OF REEF GROWTH IN RESPONSE TO SEA-LEVEL CHANGE 11.5.1 Expected morphologic and facies variations under different end member sea-level scenarios 11.5.1.1 Model assumptions 11.5.1.2 Sea-level fall 11.5.1.3 Sea-level rise 11.5.2 Examples of actual sea-level scenarios SUMMARY AND CONCLUSIONS

283 283 285 286 286 286 287 288 289 290 292 292 292 294 295 297 299

CHAPTER 12 - CONCLUSIONS 12.1 12.2 12.3 12.4

INTRODUCTION REEFS AND SEA-LEVEL FALL REEFS AND SEA-LEVEL RISE AND FALL REEFS AND SEA-LEVEL CHANGE

310 310 313 315

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REFERENCES

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APPENDIX 1 - KIKAI-JIMA DATA 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8

CORAL TAXONOMY HORIZONTAL SURVEY DATA HORIZONTAL DENSITY DATA HORIZONTAL PRESENCE AND ABSENCE DATA VERTICAL SECTION DATA NAKAGUMA DRILL CORE DATA PORITES ISOTOPE DATA WEBSTER ET AL (1998) - IN CORAL REEFS, SPECIAL ISSUE (HOLOCENE AND PLEISTOCENE REEF GEOLOGY)

330 347 362 372 382 419 437 443

APPENDIX 2 - GREAT BARRIER REEF DATA 2.1 2.2

RIBBON REEF 5 DRILL CORE DATA BOULDER REEF DRILL CORE DATA

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LIST OF FIGURES Figure 2.1. Map showing the study area.

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Figure 2.2. (A). Average atmospheric temperature (points) and rainfall (bars) at Kikai-jima over the last 27 years. (B) Sea-surface temperatures at Kikai-jima from 1993-1997. 20 Figure 2.3. Map showing the local geology of Kikai-jima and location of the C-D cross section. Figure 2.4. 22

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Holocene eustatic sea-level curves from Japan showing significant regional variation.

Figure 2.5. (A) Topographic section at Shiraho Reef on Ishigaki-jima, Ryukyu Islands; (B) Summary of the topographic zones and their characteristic coral taxa.

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Figure 2.6. Photographs showing examples of coral frameworks observed at Kikai-jima.

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Figure 2.7. Terrace morphology at Araki, Nakaguma, Nakazato and Kadon defined by Ota et al. (1978). 26 Figure 2.8. Elevation vs age plots using all available radiometric data for each raised terrace at Kikai-jima.

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Figure 3.1. Aerial photos of the five sites showing the location of the horizontal transects. 58 Figure 3.2. Photographs showing the locations examined around Kikai-jima.

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Figure 3.3. Photographs showing the locations examined around Kikai-jima.

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Figure. 3.4. Topographic profile of the five survey sites.

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Figure 3.5. Photographs showing details preserved within the Holocene terraces at Kadon.

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Figure. 3.6. Distribution of sample size, coral coverage, coral abundance, coral genera number and the average colony size recorded on the terrace surfaces at Kadon.

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Figure 3.7. Distribution of generic diversity and evenness, total coverage of allochthonous material and growth forms recorded on the terrace surfaces at Kadon.

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Figure 3.8. Distribution of relative coral abundance and coverage recorded from the terrace surfaces at Kadon.

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Figure 3.9. Distribution of relative coral abundance and coverage recorded from the terrace surfaces at Kadon.

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Figure 3.10. Photographs showing details preserved within the Holocene terraces at Shidooke.

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Figure 3.11. Distribution of sample size, coral coverage, coral abundance, coral genera number and the average colony size recorded on the terrace surfaces at Shidooke.

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Figure 3.12. Distribution of generic diversity and evenness, total coverage of allochthonous material and growth forms recorded on the terrace surfaces at Shidooke.

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Figure 3.13. Distribution of relative coral abundance and coverage recorded from the terrace surfaces at Shidooke.

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Figure 3.14. Distribution of relative coral abundance and coverage recorded from the terrace surfaces at Shidooke.

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Figure 3.15. Photographs showing details preserved within the Holocene terraces at Nakaguma. 74 Figure 3.16. Distribution of sample size, coral coverage, coral abundance, coral genera number and the average colony size recorded on the terrace surfaces at Nakaguma.

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Figure 3.17. Distribution of generic diversity and eveness, total coverage of allochthonous material and growth forms recorded on the terrace surfaces at Nakaguma.

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Figure 3.18. Distribution of relative coral abundance and coverage recorded from the terrace surfaces at Nakaguma.

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Figure 3.19. Distribution of relative coral abundance and coverage recorded from the terrace surfaces at Nakaguma.

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Figure 3.20. Photographs showing details preserved within the Holocene terraces at Nakazato.

79

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Figure 3.21. Distribution of sample size, coral coverage, coral abundance, coral genera number and the average colony size recorded on the terrace surfaces at Nakazato.

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Figure 3.22. Distribution of generic diversity and evenness, total coverage of allochthonous material and growth forms recorded on the terrace surfaces at Nakazato.

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Figure 3.23. Distribution of relative coral abundance and coverage recorded from the terrace surfaces at Nakazato.

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Figure 3.24. Distribution of relative coral abundance and coverage recorded from the terrace surfaces at Nakazato

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Figure 3.25. Photographs showing details preserved within the Holocene terraces at Araki.

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Figure 3.26. Distribution of sample size, coral coverage, coral abundance, coral genera number and the average colony size recorded on the terrace surfaces at Araki.

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Figure 3.27. Distribution of generic diversity and evenness, total coverage of allochthonous material and growth forms recorded on the terrace surfaces at Araki.

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Figure 3.28. Distribution of relative coral abundance and coverage recorded from the terrace surfaces at Araki.

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Figure 3.29. Distribution of relative coral abundance and coverage recorded from the terrace surfaces at Araki.

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Figure 3.30. Correlation plots of sample size versus coral abundance, genera number and generic diversity from Araki, Shidooke and Nakazato. Average colony size versus coral coverage is also plotted.

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Figure 3.31. Density variations in key biological characteristics at Kadon.

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Figure 3.32. Density variations in key biological characteristics at Shidooke.

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Figure 3.33. Density variations in key biological characteristics at Nakaguma.

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Figure 3.34. Density variations in key biological characteristics at Nakazato.

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Figure 3.35. Density variations in key biological characteristics at Araki.

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Figure 3.36. Holocene and modern surface coral assemblages at Kikia-jima. Examples of Assemblage A coral types.

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Figure 3.37. Holocene and modern surface coral assemblages at Kikia-jima. Examples of Assemblage A and B coral types.

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Figure 3.38. Holocene and modern surface coral assemblages at Kikia-jima. Examples of Assemblage B and C coral types.

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Figure 3.39. Holocene and modern surface coral assemblages at Kikia-jima. Examples of Assemblage D and E coral types.

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Figure 4.1. Photo and sketch of a vertical section (KVS6) through TII at Kadon showing the vertical distribution of the corals in terms of coral composition and growth form variation.

138

Figure 4.2. Photo and sketch of a vertical section (KVS1) through TII at Kadon showing the vertical distribution of the corals in terms of coral composition and growth form variation.

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Figure 4.3. Photo and sketch of a vertical section (SV3) through TII at Shidooke showing the vertical distribution of the corals in terms of coral composition and growth form variation.

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Figure 4.4. Photo and sketch of Pillar 1 and 2 at Shidooke showing the vertical distribution of the corals in terms of coral composition and growth form variation.

141

Figure 4.5. Photo and sketch showing the contact between the Pleistocene basement and the Holocene at Shidooke (SV8).

142

Figure 4.6. Photo and sketch of a vertical section (NGV2) through TIII at Nakaguma showing the vertical distribution of the corals in terms of coral composition and growth form variation.

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Figure 4.7. Photo and sketch of a vertical section (NGV1) through TIII at Nakaguma showing the vertical distribution of the corals in terms of coral composition and growth form variation.

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Figure 4.8. Photo and sketch of a vertical section (NV3) through TII at Nakazato showing the vertical distribution of the corals in terms of coral composition and growth form variation.

145

Figure 4.9. Detailed sketches showing the coral composition and distribution in sections NV10 and NV9.

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Figure 4.10. Photo and sketch of a vertical section (NV7) through TII at Nakazato showing the vertical distribution of the corals in terms of coral composition and growth form variation.

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Figure 4.11. Section NV11 in TII at Nakazato showing the vertical coral and lithological variation.

148

Figure 4.12. Photo of section AVA7 showing the flat, low angle contact between the Holocene and Pleistocene in TII at Araki.

149

Figure 4.13. Photo and sketch of section AVA6 showing the contact between the Holocene and the Pleistocene.

150

Figure 4.14. (A) Photo and sketch of a vertical section (AVA2) through TIII at Araki showing the vertical distribution of the corals in terms of coral composition and growth form variation.

151

Figure 4.15. Schematic section summarising the major characteristics of the shallowing upward sequence (pattern 1) observed in TII and TIII at Kikia-jima. 152 Figure 4.16. Schematic diagram summarising the coral distribution on the landward and seaward sides of the pillar features at Shidooke.

152

Figure 4.17. Simplified map showing the location of vertical sections and characteristic faunal patterns at Kadon.

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Figure 4.18. Simplified map showing the location of vertical sections and characteristic faunal patterns at Shidooke.

160

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Figure 4.19. Simplified map showing the location of vertical sections and characteristic faunal patterns at Nakaguma.

161

Figure 4.20. Simplified map showing the location of vertical sections and characteristic faunal patterns at Nakazato.

162

Figure 4.21. Simplified map showing the location of vertical sections and characteristic faunal patterns at Araki.

163

Figure 5.1. Aerial photo showing the location of drill holes and the terrace boundaries (white dashed line) at Nakaguma, on the western margin of Kikai-jima. 175 Figure 5.2 Nakaguma drill core transect located on the north-western margin of Kikai-jima.

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Figure 5.3. Reconstruction of the vertical accretion of the reef, taking into account the timing of uplift events, the amount of uplift, the influence of the Holocene transgression, the vertical reef accretion rate and an estimate of palaeowater depth over the last 9 ky.

178

Figure 5.4. Palaeowater depth variation over the landward (C1), mid (C5) and seaward (C12) regions of the reef at Nakaguma, Kikia-jima.

179

Figure 6.1. Model of fringing reef development at Kikai-jima in response to progressive sea-level fall over the last 7 ky.

189

Figure 6.2. Model of fringing reef development at Kikai-jima in response to progressive sea-level fall over the last 7 ky.

190

Figure 7.1. (A) Photo showing portable drilling of P19;(B) Close up of P19; (C) Simplified map of Kadon showing the location of P19.

213

Figure 7.2. X-radiograph of core P19 (Porites sp. gp. 1) showing high and low density annual bands.

214

Figure 7.3. Linear extension rates of each annual band.

215

Figure 7.4. Sixty year record of oxygen isotope variations in P19 (Porites sp. gp. 1) from TII at Kikai-jima

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Figure 7.5. Sixty year record of carbon isotope variations in P19 (Porites sp. gp. 1) from TII at Kikai-jima.

217

Figure 7.6. Detailed comparison of the oxygen and carbon isotope records.

218

Figure 7.7. Sixty year record showing the correlation between the oxygen and carbon isotope records and linear extension rates in P19 (Porites sp. gp. 1) from TII at Kikai-jima.

219

Figure 7.8. SST palaeotemperature curve for a sixty year period during the later Holocene (~ 3.5-4 ka).

220

Figure. 7.9. Plot of the general Holocene sea-surface temperatures (SST) in Japan vs age.

222

Figure 8.1 The position of the Great Barrier Reef relative to the bathymetry and main

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physiographic features of north east Australia.

231

Figure 8.2. Controls on high energy reef growth - substrate, energy and accumulation rates.

232

Figure 8.3. Model of high energy reef growth during two high sea-level growth phases and a low sea-level phase.

233

Figure 9.1. Summary lithostratigraphic logs from drill holes in Heron Island, Wreck Reef and Michaelomas Cay.

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Figure 9.2. Ribbon Reef 5 - showing the morphology, surface and subsurface facies distribution and radiocarbon data.

255

Figure 9.3. Distribution of coral community and morphologic types in the central Great Barrier Reef.

256

Figure 9.4. Boulder Reef - showing the drill hole location, lithologic and radiocarbon data.

257

Figure 9.5. Summary of the lithologic log of the Boulder and Ribbon Reef Five drill holes.

258

Figure 9.6. Photographs showing the principal coral components of Assemblage A from the Ribbon Reef 5 core.

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Figure 9.7. Photographs showing the principal coral components of Assemblage B and C from the Ribbon Reef 5 and Boulder Reef cores.

261

Figure 9.8. Individual reef sequences at Ribbon Reef 5 showing the distribution of coral assemblages, coralline algal associations and major sedimentary facies. 262 Figure 9.9. Individual reef sequences at Boulder Reef showing the distribution of coral assemblages and major sedimentary facies.

263

Figure 9.10. Log summarising the lithologic and biologic variation in the Ribbon Reef 5 core.

264

Figure 9.11. Log summarising the major lithologic and coral assemblage variation in the Boulder Reef cores.

265

Figure 10.1. Model of Pleistocene reef growth on the Great Barrier Reef margin.

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Figure 10.2. Global eustatic sea level changes for the last 350 ky based on Chappell et al. (1996) and Imbrie et al. (1984). 280 Figure 10.3. Quantitative reconstruction of reef development in the Great Barrier Reef in response to repeated sea level rise and fall over the last 350 ky.

281

Figure 11.1. Summary showing the major factors effecting the biological response of coral reefs to sea-level change.

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Figure 11.2. Model of reef growth and expected facies variations in response to sea-level fall on a flat substrate. (A) The response of reefs to fast sea-level fall. (B) The response of reefs to slow sea-level fall.

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Figure 11.3. Model of reef growth and expected facies variations in response to sea-level

xviii fall on a gentle sloping substrate (~2o). (A) The response of reefs to fast sea-level fall. (B) The response of reefs to slow sea-level fall.

304

Figure 11.4. Model of reef growth and expected facies variations in response to sea-level fall on a steep sloping substrate (~5o). (A) The response of reefs to fast sea-level fall. (B) The response of reefs to slow sea-level fall.

305

Figure 11.5. Model of reef growth and expected facies variations in response to sea-level rise on a flat substrate. (A) The response of reefs to fast sea-level fall. (B) The response of reefs to slow sea-level fall.

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Figure 11.6. Model of reef growth and expected facies variations in response to sea-level rise on a gentle sloping substrate (~2o). (A) The response of reefs to fast sea-level fall. (B) The response of reefs to slow sea-level fall.

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Figure 11.7. Model of reef growth and expected facies variations in response to sea-level rise on a steep sloping substrate (~5o). (A) The response of reefs to fast sea-level fall. (B) The response of reefs to slow sea-level fall.

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LIST OF TABLES Table 2.1. Physical environment at Ishigaki (Ishigaki-jima), Hirara (Miyako-jima), Naha (Okinawa-jima) and Naze (Amami-o-shima).

19

Table 2.2 Basic stratigraphy of Kikai-jima.

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Table 2.3. Pleistocene coral communities of the Ryukyu Group, their depositional environments and modern counter parts.

24

Table 2.4. Summary of terrace morphology at the five locations, showing average height and width.

26

Table 2.5. All available radiometric dates from the raised Holocene terraces at Kikai-jima.

27

Table 2.6. Summary of radiocarbon data for the raised Holocene terraces at Kikai-jima showing terrace elevation, growth ranges for the terrace, timing of uplift events, amount of uplift and accumulated uplift.

28

Table 3.1. Summary of the important abiotic factors (energy, turbidity and basement substrate) affecting modern day reef growth at Kikai-jima. 59 Table 3.2. Coral species and groups identified in the raised Holocene reefs of Kikai-jima. 63 Table 3.3. Summary of biological variations in the flat and slope intervals at Kadon.

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Table 3.4. Summary of biological variations in the flat and slope intervals at Shidooke.

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Table 3.5. Summary of biological variations in the flat and slope intervals at Nakaguma. 95 Table 3.6. Summary of biological variations in the flat and slope intervals at Nakazato.

97

Table 3.7. Summary of biological variations in the flat and slope intervals at Araki.

99

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Table 3.8. The mean, standard deviation (SD) and relative standard deviations (RSD) for each major biological characteristic from the five sites.

100

Table 3.9. Summary of the main characteristics, palaeoenvironmental settings and distribution of the surface Holocene coral assemblages at Kikai-jima.

101

Table 4.1. Summary of the vertical section data from Kadon.

153

Table 4.2. Summary of the vertical section data from Shidooke.

154

Table 4.3. Summary of the vertical section data from Nakaguma.

155

Table 4.4. Summary of the vertical section data from Nakazato.

156

Table 4.5. Summary of the vertical section data from Araki.

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Table 4.6. Description of sections which show the development of Holocene reef growth on the Pleistocene (pattern 9). 158 Table 5.1. Nakaguma drill core data showing radiocarbon age, drill hole depth relative to current mean sea-level, accretion rate and coral type. 176 Table 7.1. Comparison of SST's in the modern environment and the late Holocene, calculated using the palaeothermometer of Kiyama et al. (1989).

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Table 7.2. Summary of previous studies into Holocene sea-surface temperatures (SST) around Japan.

222

Table 9.1. Coral species and groups identified in the Ribbon Reef 5 and Boulder Reef cores.

259

Table 10.1. Major assumptions or parameters used in the reconstruction of Pleistocene reef development in the Great Barrier Reef.

279

Table 10.2. The average subsidence rates for ODP Sites 821, 820 and 819.

279

Table 10.3. The likely reef growth and erosion dominated periods corresponding to each isotope stage during the last 350 ky.

280

Table 11.1. Summary of the major morphologic, horizontal and vertical reef responses to sea-level fall and rise as defined by the study of the raised reefs at Kikai-jima and the deep drilling from the Northern Great Barrier Reef.

301