Jody M. Webster

Examining the impact of the Great Barrier Reef on tsunami propagation using numerical simulations

Publisher: Springer Science and Business Media LLC

Date: 25-03-2021

DOI: 10.1007/S11069-021-04686-W

Coral reef structural complexity provides important coastal protection from waves under rising sea levels

Publisher: American Association for the Advancement of Science (AAAS)

Date: 02-02-2018

DOI: 10.1126/SCIADV.AAO4350

Abstract: If coral reefs continue to degrade, waves on coastlines may substantially increase, leading to greater coastal erosion.

Late glacial to deglacial variation of coralgal assemblages in the Great Barrier Reef, Australia

Publisher: Elsevier BV

Date: 03-2018

DOI: 10.1016/J.GLOPLACHA.2018.12.014

Morphodynamic Controls for Growth and Evolution of a Rubble Coral Island

Publisher: MDPI AG

Date: 19-04-2021

DOI: 10.3390/RS13081582

Abstract: Rubble islands are dynamic sedimentary features present on reef platforms that evolve under a variety of morphodynamic processes and controlling mechanisms. They provide valuable inhabitable land for small island nations, critical habitat for numerous species, and are threatened by climate change. Aiming to investigate the controlling mechanisms dictating the evolution of One Tree Island (OTI), a rubble island in the Southern Great Barrier Reef, we combined different remotely-sensed data across varying timescales with wave data extracted from satellite altimetry and cyclone activity. Our findings show that (1) OTI had expanded by 7% between 1978 and 2019, (2) significant gross planform decadal adjustments were governed by the amount, intensity, proximity, and relative position of cyclones as well as El Niño Southern Oscillation (ENSO) phases, and (3) the mechanisms of island growth involve rubble spits delivering and redistributing rubble to the island through alongshore sediment transport and wave overtopping. Frequent short-term monitoring of the island and further research coupling variations in the different factors driving island change (i.e., sediment availability, reef-wave interactions, and extreme events) are needed to shed light on the future trajectory of OTI and other rubble islands under a climate change scenario.

Are coral reefs victims of their own past success?

Publisher: American Association for the Advancement of Science (AAAS)

Date: 04-2016

DOI: 10.1126/SCIADV.1500850

Abstract: Pleistocene sea-level change transformed staghorn corals into prolific reef builders that are sensitive to anthropogenic stressors.

Bryozoans are major modern builders of South Atlantic oddly shaped reefs

Publisher: Springer Science and Business Media LLC

Date: 25-06-2018

DOI: 10.1038/S41598-018-27961-6

Abstract: In major modern reef regions, either in the Indo-Pacific or the Caribbean, scleractinian corals are described as the main reef framework builders, often associated with crustose coralline algae. We used underwater cores to investigate Late Holocene reef growth and characterise the main framework builders in the Abrolhos Shelf, the largest and richest modern tropical reef complex in the South Western Atlantic, a scientifically underexplored reef province. Rather than a typical coralgal reef, our results show a complex framework building system dominated by bryozoans. Bryozoans were major components in all cores and age intervals (2,000 yrs BP), accounting for up to 44% of the reef framework, while crustose coralline algae and coral accounted for less than 28 and 23%, respectively. Reef accretion rates varied from 2.7 to 0.9 mm yr −1 , which are similar to typical coralgal reefs. Bryozoan functional groups encompassed 20 taxa and Celleporaria atlantica (Busk, 1884) dominated the framework at all cores. While the prevalent mesotrophic conditions may have driven suspension-feeders’ dominance over photoautotrophs and mixotrophs, we propose that a combination of historical factors with the low storm-disturbance regime of the tropical South Atlantic also contributed to the region’s low ersity, and underlies the unique mushroom shape of the Abrolhos pinnacles.

Coral Record of Younger Dryas Chronozone Warmth on the Great Barrier Reef

Publisher: American Geophysical Union (AGU)

Date: 12-2020

DOI: 10.1029/2020PA003962

Morphotype differentiation in the Great Barrier Reef Halimeda bioherm carbonate factory: Internal architecture and surface geomorphometrics

Publisher: Wiley

Date: 16-08-2021

DOI: 10.1002/DEP2.122

Abstract: The calcareous Halimeda bioherms of the northern Great Barrier Reef, Australia are the largest actively accumulating Halimeda deposits worldwide. They contribute a substantial component of the Great Barrier Reef neritic carbonate factory, as well as the geomorphological development of Australia's northeast continental shelf. Halimeda bioherm geomorphology is complex, expressing three distinct variations in morphotype patterns: annulate, reticulate and undulate. Similar regular and irregular geomorphological patterning often results from scale‐dependent biophysical feedback mechanisms. Therefore, a better understanding of morphotype differentiation can inform the biotic and abiotic drivers of spatial heterogeneity in the bioherm ecosystem. Here, 3D LiDAR bathymetry is integrated with 2D sub‐bottom profile datasets to investigate surface topography and internal sedimentary architecture of Halimeda bioherms through space and time. Using the ESRI ArcGIS 3D Analyst and Benthic Terrain Modeller extensions, the bioherm surface and subsurface geomorphometric characteristics were quantified for the annulate, reticulate and undulate morphotypes. Significant variation was found between the three bioherm morphotypes in their surface topography, internal structure, volume, slope gradients and terrain complexity. Therefore, their geomorphology is probably influenced by differing processes and biophysical feedback mechanisms. The complex surface topography does not appear to be inherited from the antecedent substrate, and preferred aspect orientations resulting from hydrodynamic forcing appear to be limited. It is suggested here that autogenic dynamics or biotic self‐organization similar to patterns and processes in other marine organo‐sedimentary systems modulates Halimeda bioherm geomorphology, and some hypotheses are offered towards future studies. Morphotype differentiation has implications for the development of the Halimeda bioherm carbonate factory, rates of sediment aggradation and progradation, and variable capacity to fill accommodation space. Self‐organization dynamics and morphology differentiation in Modern bioherm systems could potentially inform palaeo‐environmental interpretations of fossil bioherms and phylloid algal mounds on geological timescales.

Paleoshorelines and lowstand sedimentation on subtropical shelves: a case study from the Fraser Shelf, Australia

Publisher: Informa UK Limited

Date: 10-02-2019

DOI: 10.1080/08120099.2018.1558417

Relative sea level response to mixed carbonate-siliciclastic sediment loading along the Great Barrier Reef margin

Publisher: Elsevier BV

Date: 04-2023

DOI: 10.1016/J.EPSL.2023.118066

Benthic communities of the lower mesophotic zone on One Tree shelf edge, southern Great Barrier Reef, Australia

Publisher: CSIRO Publishing

Date: 24-08-2023

DOI: 10.1071/MF23050

The Influence of Carbonate Platforms on the Geomorphological Development of a Mixed Carbonate‐Siliciclastic Margin (Great Barrier Reef, Australia)

Publisher: American Geophysical Union (AGU)

Date: 04-2020

DOI: 10.1029/2020GC008915

The Formation of Atolls: New Insights From Numerical Simulations

Publisher: American Geophysical Union (AGU)

Date: 08-2022

DOI: 10.1029/2022JF006812

Abstract: Several theories have been proposed to explain atoll formation. While karst dissolution during glacial periods and preferential coral reef accretion along raised bank margins during deglaciations and interglacials have been invoked to explain atoll formation, the respective roles of karst dissolution and reef margin construction in atoll formation have not been adequately evaluated by simulations. In this study, we conducted three‐dimensional numerical simulations of the Quaternary development of Meiji Atoll in the southern South China Sea based on interpreted data from a 2020‐m‐deep borehole drilled on its northeast rim in 2018. Our results suggest that the origin of atolls is more likely due to spatially differential dissolution across margin and interior areas (i.e., minimal along margins and maximal in bank centers) rather than preferential reef accretion along margins of flat‐topped banks. Preferential reef accretion along margins of flat‐topped banks that can result in central lagoons and atoll morphology can hardly result in the formation of lagoonal patch reefs that reach mean sea level. Preferential reef accretion along margins is mainly predicated on the karst‐induced morphology that has a central depression surrounded by raised rims, that is, using antecedent karst morphologies. If topographic highs in the lagoon are similar in elevation to the margins, reef accretion on these topographic highs can be similar to that observed on the margins, resulting in lagoonal patch reefs that reach mean sea level. Our simulation shows that spatially differential dissolution across margin and interior areas is a critical driver of worldwide central lagoons and atoll formation.

High‐resolution hyperspectral imaging of diagenesis and clays in fossil coral reef material: a nondestructive tool for improving environmental and climate reconstructions

Publisher: American Geophysical Union (AGU)

Date: 08-2017

DOI: 10.1002/2017GC006949

Spatio-temporal patterns in the postglacial flooding of the Great Barrier Reef shelf, Australia

Publisher: Elsevier BV

Date: 02-2019

DOI: 10.1016/J.CSR.2018.12.001

Depositional environments beneath the shelf-edge slopes of the Great Barrier Reef, inferred from foraminiferal assemblages: IODP Expedition 325

Publisher: Elsevier BV

Date: 2019

DOI: 10.1016/J.PALAEO.2018.10.033

Field measurements from contrasting reefs show spurs and grooves can dissipate more wave energy than the reef crest

Publisher: Wiley

Date: 03-03-2021

DOI: 10.1002/ESSOAR.10506369.1

Examining the impact of the Great Barrier Reef on tsunami propagation using numerical simulations

Publisher: California Digital Library (CDL)

Date: 31-01-2022

DOI: 10.31223/X5P010

Abstract: Coral reefs may provide a beneficial first line of defence against tsunami hazards, though this is currently debated. Using a fully nonlinear, Boussinesq propagation model, we examine the buffering capacity of the Great Barrier Reef against tsunamis triggered by several hypothetical sources: a series of far-field, Solomon Islands earthquake sources of various magnitudes (Mw 8.0, Mw 8.5, and Mw 9.0), a submarine landslide source that has previously been documented in the offshore geological record (i.e. the Gloria Knolls Slide), and a potential future landslide source (i.e. the Noggin Block). We show that overall, the Great Barrier Reef acts as a large-scale regional buffer due to the roughness of coral cover and the complex bathymetric features (i.e. platforms, shoals, terraces, etc.) that corals construct over thousands of years. However, the buffering effect of coral cover is much stronger for tsunamis that are higher in litude. When coral cover is removed, the largest earthquake scenario (Mw 9.0) exhibits up to a 31% increase in offshore wave litude and estimated run-up. These metrics increase even more for landslide scenarios, where they tend to double. These discrepancies can be explained by the higher bed particle velocities incited by higher- litude waves, which leads to greater frictional dissipation at a seabed covered by coral. At a site-specific level, shoreline orientation relative to the reef platforms also determines the degree of protectiveness against both types of tsunamis, where areas situated behind broad, shallow, coral-covered platforms benefit the most. Additionally, we find that the platforms, rather than gaps in the offshore reef structure, tend to lify wave trains through wave focussing when coral cover is removed from simulations. Our findings have implications for future tsunami hazards along the northeastern Australian coastline, particularly as the physiological stressors imposed by anthropogenic climate change further exacerbate coral die-off and reductions in ecosystem complexity. Therefore, areas that experience a protective benefit by the Great Barrier Reef’s platforms could be disproportionately more vulnerable in the future.

Reef Sedimentary Accretion Model (ReefSAM): Understanding coral reef evolution on Holocene time scales using 3D stratigraphic forward modelling

Publisher: Elsevier BV

Date: 09-2017

DOI: 10.1016/J.MARGEO.2017.07.007

New evidence of Hawaiian coral reef drowning in response to meltwater pulse-1A

Publisher: Elsevier BV

Date: 11-2017

DOI: 10.1016/J.QUASCIREV.2017.08.022

Submarine landslides on the Great Barrier Reef shelf edge and upper slope: A mechanism for generating tsunamis on the north-east Australian coast?

Publisher: Elsevier BV

Date: 2016

DOI: 10.1016/J.MARGEO.2015.11.008

Variations in Mid‐ to Late Holocene Nitrogen Supply to Northern Great Barrier Reef Halimeda Macroalgal Bioherms

Publisher: American Geophysical Union (AGU)

Date: 02-2021

DOI: 10.1029/2020PA003871

Abstract: The northern Great Barrier Reef (GBR) Halimeda bioherms have accumulated on the outer continental shelf from calcium carbonate algal sediments over the past ∼10,000 years and cover ,000 km 2 of shelf area. As such, Halimeda bioherms play a key role in the shallow marine carbon cycle over millennial timescales. The main source of nitrogen (N) to these bioherms is thought to be westward transport of upwelled NO 3 ‐ ‐rich water from the Coral Sea. However, the primary N source has not been traced geochemically, and we have no understanding of any temporal variation. Here, we reconstruct patterns of N supply to Halimeda bioherms in the GBR since the mid‐Holocene using the 15 N/ 14 N ratio of skeletal‐bound organic N (δ 15 N‐skeletal organic material [SOM]) in modern and fossil Halimeda sediment cores. Average Halimeda skeletal δ 15 N‐SOM was 6.28 ± 0.26‰, consistent with δ 15 N‐NO 3 ‐ from western tropical South Pacific (WTSP) thermocline waters. Thus, geochemically validating shelf‐break upwelling of an oceanic N source that regulates bioherm spatial distribution. Halimeda δ 15 N‐SOM decreased by 1‰–2‰ from 5,000 to 2,000 cal. yr BP, reaching a minima of 5.5‰ that persisted for almost 1,000 years. The Halimeda δ 15 N‐SOM variation reflects mid‐ to late Holocene changes in regional climate and intensified El Niño activity that likely facilitated elevated N 2 fixation in the WTSP, thereby lowering thermocline δ 15 N‐NO 3 ‐ . Thus, Halimeda skeletal material provides a valuable high‐resolution geochemical archive of past oceanographic and climatic processes over centennial to millennial timescales, complementing existing paleoclimate proxy records.

Bayesreef: A Bayesian inference framework for modelling reef growth in response to environmental change and biological dynamics

Publisher: Elsevier BV

Date: 03-2020

DOI: 10.1016/J.ENVSOFT.2019.104610

Microbialites in Last Glacial Maximum and deglacial reefs of the Great Barrier Reef (IODP Expedition 325, NE Australia)

Publisher: Elsevier BV

Date: 2019

DOI: 10.1016/J.PALAEO.2018.10.007

Rapid glaciation and a two-step sea level plunge into the Last Glacial Maximum

Publisher: Springer Science and Business Media LLC

Date: 07-2018

DOI: 10.1038/S41586-018-0335-4

Abstract: The approximately 10,000-year-long Last Glacial Maximum, before the termination of the last ice age, was the coldest period in Earth's recent climate history

Variability of depth-limited waves in coral reef surf zones

Publisher: Elsevier BV

Date: 10-2018

DOI: 10.1016/J.ECSS.2018.06.010

Quaternary coral, coralline algal and vermetid assemblages as sea-level indicators: a review

Publisher: International Association of Sedimentologists

Date: 12-2022

DOI: 10.54780/IASSP49/01

Abstract: Corals, coralline algae and vermetid gastropods are indirect (marine limiting) relative sea-level (RSL) indicators. The precision in sea-level reconstruction based on fossils of those organisms depends on the probable palaeodepth in which they grew. Constraining such palaeodepth depends, in turn, on the available information about the habitats of their living counterparts. Diverse genera, species and species assemblages of corals, coralline algae and vermetid gastropods have historically been proposed as reliable indicators of narrow, shallow depth ranges. However, the increased information on depth distribution of marine benthos in the last two decades has challenged some early assumptions about depth ranges of taxa considered diagnostic of precise palaeodepths. Here, the authors test the reliability of coral, coralline algal and vermetid assemblages that have been extensively used in RSL reconstructions in the light of data from Ocean Biogeographical Information System (OBIS) and other recently published data. In the Indo-Pacific province, these data support the use of the robust-branching and the shallow, high-energy encrusting coral assemblages with a 0 to 10 m uncertainty. In both cases many component species have unimodal distributions and both median and average water depths are shallower than 10 m. The reliability of these coral assemblages as indicative of shallow water depths is strengthened when corals are encrusted by thick plants of the coralline alga Porolithon gr. onkodes. According to OBIS data, coralline algae of this species group in the Indo-Pacific are restricted to very shallow waters (95% probability of occurrence shallower than 0.2 m and in 99.6% of records shallower than 6 m). However, such a narrow depth range and the overall scarce data on coralline algal species in the OBIS database are questionable due to difficulties of coralline algal species identification with the naked eye. A comprehensive survey of the modern distribution of coralline algae at One Tree Reef (southern Great Barrier Reef) indicates that P. gr. onkodes has a log-normal distribution with median depth of less than 5 m and 95% of occurrence probability of thick crusts ( 0.2 mm) shallower than 8.8 m. Data on modern distribution of vermetids are scarce. In the OBIS database, vermetid species are reported from relatively wide depth ranges. However, relatively high densities ( 10 in iduals per m2) on coral and coralline algal surfaces only occur from above mean low tide to some 6 m depth. In the Western Atlantic-Caribbean province Acropora palmata is the most precise RSL marker and no additional components of fossil assemblages improve its palaeodepth information. The confident use of coralgal and vermetid assemblages as RSL indicators relies on the identification of fossil corals and coralline algae at the species or species-group level. The scarcity of available data highlights the need for further studies on distribution of coralline algal species and vermetid in modern coral reefs from a variety of oceans and reef settings.

The influence of coral reef spur and groove morphology on wave energy dissipation and wave overtopping under future climate change scenarios

Publisher: Authorea, Inc.

Date: 18-09-2023

DOI: 10.22541/ESSOAR.169504527.76166520/V1

Towards solving the missing ice problem and the importance of rigorous model data comparisons

Publisher: Springer Science and Business Media LLC

Date: 24-10-2022

DOI: 10.1038/S41467-022-33952-Z

New insights on the Late Quaternary evolution of Abrolhos reefs, Eastern Brazilian Shelf

Publisher: International Association of Sedimentologists

Date: 12-2022

DOI: 10.54780/IASSP49/03

Abstract: The Abrolhos shelf, in the eastern Brazilian margin, encompasses the largest reef province in the South Atlantic, characterised by low coral ersity and a high level of endemism. Knowledge gaps about how the Abrolhos coastal reefs evolved, during the post LGM and MIS 6/MIS 5, favoured a paradigm that is revisited in the light of new data. Here, new data from two new, long boreholes (20 and 50 m-long) are presented in order to investigate and provide new insights into the evolution of two shallow reefs on the Abrolhos Shelf during the late Pleistocene and Holocene epochs. Results show that Holocene and Pleistocene reefs grew on highly turbid waters with a significant terrigenous sediment input. Corals and CCA assemblages were identified as main framework builders of Abrolhos inner-shelf reefs since the Pleistocene. No clear shallowing upward sequence of reef builders was observed, which differs from other reef sequences all over the world. In terms of Holocene reef growth, Pedra Grande and Coroa Vermelha reefs turned on roughly coevally at different depths and with different coral assemblages. Pedra Grande reef started growing circa 6.8 kyr BP in a water depth approximately 10 m deeper than Coroa Vermelha, which started growing around 6.4 kyr BP, but Coroa Vermelha turned off at around 4 kyr BP, while Pedra Grande kept growing until around 1.2 kyr BP. This novel reef stratigraphy data provided a new insight on the evolution of the Abrolhos coastal reefs, showing that different environmental and topographic controls could have acted spatially in different ways. Coroa Vermelha reef seems to have started its growth as a result of a topographic high control. Pedra Grande reef seems to be connected to a broader submerged reef setting and started to grow in deeper water depths. The presence of three reef arcs in Abrolhos is proposed, including a submerged reef arc.

Shelf-edge deglacial reef establishment and subsequent partial demise: Response to distinct pulses of sea-level rise associated with environmental changes

Publisher: International Association of Sedimentologists

Date: 12-2022

DOI: 10.54780/IASSP49/05

Abstract: The partial melting of Earth’s bi-polar ice sheets since the Last Glacial Maximum (LGM) has translated into a ~ 120 m litude stepwise sea-level rise punctuated by three major meltwater pulses that were tracked and recorded with some of the best accuracy by coral reefs. However, the initial meltwater pulse marking the end of the LGM, at 19 ka, is anchored in only two palaeo reefs (Barbados, Great Barrier Reef). Here, the authors present the analysis of a coralgal reef that thrived along the south-east Papua New Guinea Peninsula outer shelf during this initial pulse. In the cone of a piston core, a shallow Goniastrea retiformis coral colony was retrieved at 111 m below present sea-level and uranium/thorium dated to 19.4 ka BP. This colony had been buried beneath the debris of a proximal coralgal reef before its partial drowning at 14.5 ka BP. Seismic survey data suggest that the reef edifice was established directly on the eroded top of a lowstand shelf-edge delta, partially drowned and then back-stepped towards the south-east in response to three distinct deglacial sea-level pulses and stepwise increases of water column turbidity.

Reef growth history at intermediate to mesophotic depths since the end of the Last Glacial period along the Great Barrier Reef shelf edge

Publisher: International Association of Sedimentologists

Date: 12-2022

DOI: 10.54780/IASSP49/07

Abstract: Reef communities at intermediate (10 to 30 m) and mesophotic (~ 30 to 150 m) depths occupy large areas of sea floor but little is known about their potential to accrete vertically, their response to sea-level change and other environmental perturbations. In this study, the authors have examined cores from two holes, M0040A and M0041A, drilled by the International Ocean Drilling Program Expedition 325 along the shelf edge of the modern GBR at 131 m water depth. The objective was to investigate reef growth history at palaeo-water depths 20 m over a time period spanning 30,000 years, from the end of the Last Glacial period through the last deglaciation. Based on changes in lithologies and biotic components, and a robust chronostratigraphic framework supported by 47 radiometric ages, the authors have identified two episodes of reef growth, one during Marine Isotope Stage (MIS) 2 and the other at the onset of the deglaciation, both characterised by abundant microbialite crusts and distinct coral assemblages. Palaeo-water depths range from 30 to 60 m and from 20 to 30 m for the MIS 2 and early deglacial reef sections, respectively. The first episode of reef growth documented in the cores initiated at 27 to 25 ka, possibly in response to increased light availability and change in sedimentation resulting from falling sea-level between 32 and 29 ka from MIS 3 and also to low atmospheric pCO2 at the end of the Last Glacial period. Reef accretion was reduced or ceased sometime between 24 and 19 ka, coinciding with the rapid 20 m sea-level fall of the peak Last Glacial Maximum and minima of SSTs. Reef growth resumed at 19.5 to 18.5 ka, influenced by a period of moderate sea-level rise and increasing sea surface temperatures at the onset of the deglaciation. Reef growth termination at ca. 17 ka correlates with a major episode of reef demise previously identified in adjacent mid and outer terrace cores and linked to reduced water quality combined with rapid deglacial sea-level rise. Vertical accretion (VA) rates were calculated based on two methods: linear visual fitting and Bayesian modelling. The findings show that the highest VA rates are associated with microbialite boundstone. Reef ecosystems dominated by microbialite and corals developed at intermediate and mesophotic depths, and grew vertically at maximum rates of 2 to 5 mm yr-1 depending on the method used, over a period of rapid environmental change during the transition from MIS 3 to MIS 1. Further study needs to explore the potential of modern-type deep coralgal communities to cope with higher rates of sea-level rise predicted this century.

Coral reef development and sea-level changes over the past 50,000 years

Publisher: International Association of Sedimentologists

Date: 12-2022

DOI: 10.54780/IASSP49/08

Abstract: Understanding of global sea-level changes and coral reef development is poorly constrained during Marine Isotope Stage 3 (MIS 3 ~ 60 to 30 ka). Australia’s North West Shelf (NWS), at depths of ~ 50 to 120 m below present sea-level (mbsl), represents an ideal natural laboratory to address these knowledge gaps. In this study, the authors investigate a unique suite of sea-bed rock drill (PROD) cores recovered as part of a geotechnical survey from the NWS ~ 150 km south-east of Ashmore Reef. Twenty cores, penetrating to 28 m below sea floor, were collected from the top of the now drowned platform complex in similar water depths (74.8 to 81.6 mbsl), forming two transects ~ 17 km apart. High-resolution 3D seismic and multibeam bathymetry data reveal three distinct, multigenerational platforms that are rimmed by smaller reef terraces and bisected by deeper channels, placing the core transects into a robust, regional geomorphic context that includes a succession of linear palaeo-shorelines and tidal-estuarine channel systems on the adjacent shelf between ~ 90 to 110 mbsl. The authors have completed detailed logging, high-spatial resolution hyperspectral scanning, petrologic, mineralogic and sedimentary facies analysis of these cores, including a precise palaeoenvironmental reconstruction based on coral, algal and larger benthic foraminifera assemblages and extensive radiometric dating. The authors have observed a complex suite of lithologies including in situ coralgal reef frameworks, well-lithified to friable grainstones, packstones and coralline algal floatstone facies separated by at least two major palaeosol horizons. Together with thirty 14C-AMS and closed-system U/Th ages spanning 10.7 to 50 ka, the authors define a complex but consistent record of four distinct chrono-stratigraphic units (Units 1 to 4), representing a repeated succession of shallow reef to deep reef-slope depositional settings as the platforms experienced repeated sea-level oscillations (interstadial/stadial to glacial/deglacial) over the last 75,000 yr. Two distinct phases of shallow-water, high-energy reef development are defined. The age of the older, diagenetically distinct reef unit (Unit 3) is unknown but interpreted to have developed before the MIS 4 lowstand (~ 65 ka). However, firm chronological constraints on the MIS 3 development of the younger reef unit (Unit 2), place the position of relative sea-level (RSL) between ~ 63 to 75 + 1.8 mbsl by 45.95 to 39.23 + 0.2 ka, consistent with other predictions and observations for the region. Following its exposure and demise due to sea-level fall to the Last Glacial Maximum (LGM), the platform system was unable to re-establish fully as it was reflooded during the subsequent deglacial sea-level rise. Deeper reef slope (Unit 1) facies dominate the core tops between ~ 13.2 to 10.7 ka, representing a major hiatus in shallow-water reef development on the platforms. Deglacial sea-level rise was either too fast and/or other environmental conditions inadequate (i.e. massive riverine sediment flux due to the strengthening Australian summer monsoon and/or reworking of shelf sediments) to allow re-establishment of shallow-water coral reef development on the platforms apart from a few isolated and distal locations (i.e. Ashmore, Cartier, Adele and Scott Reefs).

Role of the Deglacial Buildup of the Great Barrier Reef for the Global Carbon Cycle

Publisher: American Geophysical Union (AGU)

Date: 14-02-2022

DOI: 10.1029/2021GL096495

Abstract: The carbon isotope 13 C is commonly used to attribute the last deglacial atmospheric CO 2 rise to various processes. Here we show that the growth of the world's largest reef system, the Great Barrier Reef (GBR), is marked by a pronounced decrease in δ 13 C in absolutely dated fossil coral skeletons between 12.8 and 11.7 ka, which coincides with a prominent minimum in atmospheric δ 13 CO 2 and the Younger Dryas. The event follows the flooding of a large shelf platform and initiation of an extensive barrier reef system at 13 ka. Carbon cycle simulations show the coral δ 13 C decrease was mainly caused by the combination of isotopic fractionation during reef carbonate production and the decomposition of organic land carbon on the newly flooded shallow‐water platform. The impacts of these processes on atmospheric CO 2 and δ 13 CO 2 , however, are marginal. Thus, the GBR was not contributing to the last deglacial δ 13 CO 2 minimum at ∼12.4 ka.

University Of Sydney

Location: Australia

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Linkage Infrastructure, Equipment And Facilities - Grant ID: LE230100044

Start Date: 2023

End Date: 12-2024

Amount: $4,378,196.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP120101793

Start Date: 2012

End Date: 11-2018

Amount: $490,000.00

Funder: Australian Research Council

Linkage Infrastructure, Equipment And Facilities - Grant ID: LE0882854

Start Date: 03-2008

End Date: 09-2013

Amount: $6,000,000.00

Funder: Australian Research Council

Linkage Infrastructure, Equipment And Facilities - Grant ID: LE160100067

Start Date: 2016

End Date: 12-2020

Amount: $10,000,000.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP1094001

Start Date: 03-2010

End Date: 09-2015

Amount: $372,000.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP200100206

Start Date: 06-2020

End Date: 06-2024

Amount: $418,000.00

Funder: Australian Research Council

Linkage Infrastructure, Equipment And Facilities - Grant ID: LE210100028

Start Date: 08-2021

End Date: 08-2023

Amount: $3,000,000.00

Funder: Australian Research Council

Industrial Transformation Training Centres - Grant ID: IC190100031

Start Date: 08-2020

End Date: 08-2025

Amount: $3,973,202.00

Funder: Australian Research Council

Linkage Infrastructure, Equipment And Facilities - Grant ID: LE140100047

Start Date: 2014

End Date: 12-2016

Amount: $3,600,000.00

Funder: Australian Research Council