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Reef islands are some of the most highly sensitive landforms to the impacts of future environmental change. Previous assessments of island morphodynamics primarily relied on historical aerial and satellite imagery. These approaches limit analysis to two-dimensional parameters, with no ability to assess long-term changes to island volume or elevation. Here, we use high-resolution airborne LiDAR data to assess three-dimensional reef island features for 22 islands along the north-western coast of Australia. Our primary objective was to utilize two regional LiDAR datasets to identify characteristics indicative of island sensitivity and future vulnerability. Results show reef platform area to be an accurate predictor of island area and volume suggesting larger island volumes may reflect (1) increased carbonate production and supply from the reef platform and/or (2) enhanced shoreline protection by larger reef platforms. Locations of foredune scarping (an erosional signature) and island orientations were aligned to the regional wind and wave climate. Reef island characteristics (island area, volume, elevation, scarping, and platform area) were used to rank islands according to sensitivity, using a new Island Sensitivity Characteristics Index (ISCi) where low ISCi indicates stable islands (large areas and volumes, high elevations, and fewer scarped areas) and high ISCi indicates unstable islands (small areas and volumes, low elevations, and more scarped areas). Comparison of two LiDAR surveys from 2016 and 2018 validates the use of 3D morphometrics as important (direct) measurements of island landform change, and can complement the use of 2D parameters (e.g., area) moving forward. Results demonstrate that ongoing use of airborne LiDAR and other 3D technology for monitoring coral reef islands at regional scales will enable more accurate quantification of their sensitivity to future impacts of global environmental change.

© 2019, Springer-Verlag GmbH Germany, part of Springer Nature. Seagrass meadows are important benthic habitats contributing to many aspects of ecological community health, beach stability and sediment supply. Relationships between morpho-sedimentary features and distribution of seagrass meadows were investigated through an integrated analysis of geomorphology, sediments and benthic habitat structure in a temperate nearshore setting (Esperance Bay, Western Australia). The results demonstrate that seagrass distribution is related to gradients in sediment texture and composition, hydrodynamics and human impact. Dense seagrass meadows occurred in more sheltered regions of the bay, whereas sparser vegetation was found in areas of higher wave energy and artificial activities (like ship anchoring and dredging activities). A preferential retention of heavier siliciclastic sediments was recorded in the seagrass meadows especially in areas with high sediment supply resulting in elevated beds and formation of intermates. Sediment characteristics suggest that carbonate sediment is transported onshore from the seagrass meadow supplying the beach system. The combined analyses of geomorphological features and sediment characteristics at Esperance have allowed identification of a prevalent eastward oriented sediment transport current. Seagrass beds are confirmed to be a sediment source in terms of sediment budget contributing to beach stability. Integrated geomorphological data, sediment analyses and benthic habitat mapping provide useful information for the management of coastal environments characterized by the presence of seagrass meadows by providing new insights on coastal processes.

This research aims to explore the submerged landscapes of the Pilbara of Western Australia, using predictive archaeological modelling, airborne LiDAR, marine acoustics, coring and diver survey. It includes excavation and geophysical investigation of a submerged shell midden in Denmark to establish guidelines for the underwater discovery of such sites elsewhere.

Sedimentary rocks along the southern margin of Australia host an important record of the break-up history of east Gondwana, as well as fragments of a deeper geological history, which collectively help inform the geological evolution of a vast and largely underexplored region. New drilling through Cenozoic cover has allowed examination of the Cretaceous rift-related Madura Shelf sequence (Bight Basin), and identification of two new stratigraphic units beneath the shelf; the possibly Proterozoic Shanes Dam Conglomerate and the interpreted Palaeozoic southern Officer Basin unit, the Decoration Sandstone. Recognition of these new units indicates an earlier basinal history than previously known. Lithostratigraphy of the new drillcore has been integrated with that published from onshore and offshore cores to present isopach maps of sedimentary cover on the Madura Shelf. New palynological data demonstrate progression from more localised freshwater-brackish fluvio-lacustrine clastics in the early Cretaceous (Foraminisporis wonthaggiensis – Valanginian to Barremian) to widespread topography-blanketing, fully marine, glauconitic mudrocks in the mid Cretaceous (Endoceratium ludbrookiae – Albian). Geochronology and Hf-isotope geochemistry show detrital zircon populations from the Madura Shelf are comparable to those from the southern Officer Basin, as well as Cenozoic shoreline and palaeovalley sediments in the region. The detrital zircon population from the Shanes Dam Conglomerate is defined by a unimodal ~1400 Ma peak, which correlates with directly underlying crystalline basement of the Madura Province. Peak ages of ~1150 Ma and ~1650 Ma dominate the age spectra of all other samples, indicating a stable sediment reservoir through much of the Phanerozoic, with sediments largely sourced from the Albany-Fraser Orogen and Musgrave Province (directly and via multiple recycling events). The Madura Shelf detrital zircon population differs from published data for the Upper Cretaceou

Surface scatters containing Eocene chert artefacts are a widespread cultural site type along the Swan Coastal Plain; however, no source rock for the chert is known to exist locally. In the absence of chert outcrops onshore, archaeologists have argued for an offshore source that was subsequently flooded during post-glacial sea level rise. Support for this theory has been the decline or absence of Eocene chert artefacts in deposits younger than 6000 years BP, and the apparent decrease in chert assemblage inland from the contemporary coastline, which may call into question a distal eastern source. This paper presents an alternative theory whereby chert was sourced from the Nullarbor Plain (~1000 km to the east) and traded east as well as west across southern Australia. Evidence to support this theory includes (1) absence of Eocene age sedimentary strata outcropping on the continental shelf, (2) faunal evidence showing bryozoans imbedded in the Swan Coastal Plain chert, with similar environmental affinities to bryozoans embedded in chert outcropping along the Nullarbor Plain sea cliffs, and (3) geochemical evidence showing a similar geochemical fingerprint between artefacts from the Nullarbor Plain and Swan Coastal Plain. With a peak in fossiliferous chert use around the Last Glacial Maximum, these findings have significant ethnographic implications supporting long distance trade to the east rather than local sourcing of lithic resources by isolated Aboriginal groups. These findings also have chronological implications relating to the use of Eocene fossiliferous chert as a chronological marker for Late Pleistocene to early-Holocene age deposits in southwest Western Australia, albeit with source accessibility following post-glacial sea-level rise still a main factor in the decline in chert use.

High-resolution seismic profiles were conducted across the metropolitan area of the Swan River estuary (Perth, Western Australia) to explore the sub-surficial stratigraphic architecture, down to a depth of about 40 m below the river bed. The acoustic profiles revealed a complex system of palaeochannels where three main unconformities (R1, R2, R3) bound as many seismic units (U1, U2, U3), over the acoustic basement. Integrating these data with sediment borehole analysis, LiDAR data and available literature of the geology and stratigraphy of the area, it was possible to determine the development of these stratigraphic units, in response to Late Pleistocene and Holocene sea level fluctuations and conditioned by pre-existing topography and depositional palaeoenvironments during the last ~ 130,000 years. The deepest unit (U3) can be interpreted as the Perth Formation, which consists of interbedded sediments that were deposited in a large palaeo-valley downcutting into the underlying acoustic basement (bedrock: Tamala Limestone and Kings Park Formation), under a fluvial to estuarine setting, existing between ~ 130 and 80 ky BP (in the Last Interglacial). The middle unit (U2), composed of heterogenic fluvial (possibly lacustrine) and estuarine sediments, represents the Swan River Formation. Similarly to the Perth Formation, the formation infills channels incised in older formations and reflects the hydrogeological conditions linked with sea level fluctuation changes during the Last Glacial low stand. Holocene (last ~ 10 ky) fluvial and estuarine deposits form the shallowest unit (U1). These sediments have a highly variable internal structure, ranging from heavily layered, filling palaeochannels, to hard and chaotic, atop pre-existing topographic highs. The wave-dominated Swan River system shares several similarities with a number of estuaries worldwide, such as Burrill Lake (NSW, Australia) and Arcachon Lagoon (Aquitaine, France). This research represents the first environ

Satellite remote sensing is one of the most efficient techniques for marine habitat studies in shallow coastal waters, especially in clear waters where field observations can be easily carried out. However, such in situ observations have certain limitations: they are time consuming, have a limited ability to capture spatial variability, and require an interdisciplinary approach between marine biologists and remote-sensing specialists. The main objective of this study was to survey and map Sargassum beds around Rottnest Island, Western Australia, through a combination of high spatial resolution WorldView-2 imagery, using a validated depth invariant index model for water-column correction, and in-field observations. The combination of field survey data and four classification methods resulted in highly accurate classification outcomes that showed the distribution patterns of Sargassum spp. around Rottnest Island during the austral spring season (October 2013). Overall, the minimum distance and Mahalanobis classifiers yielded the highest overall accuracy rates of 98.32% (kappa coefficient, κ = 0.96) and 98.30% (κ = 0.96), respectively. The K-means classification method gave the lowest accuracy percentage of 42.50% (κ = 0.22). Thus, the primary results of this study provide useful baseline information that is necessary for marine-conservation strategic planning and the sustainable utilization of brown macroalgae resources around the Western Australian coast.

The Last Interglacial (MIS 5e, 128-116 ka) is among the most studied past periods in Earth’s history. The climate at that time was warmer than today, primarily due to different orbital conditions, with smaller ice sheets and higher sea-level. Field evidence for MIS 5e sea-level was reported from thousands of sites, but often paleo shorelines were measured with low-accuracy techniques and, in some cases, there are contrasting interpretations about paleo sea-level reconstructions. For this reason, large uncertainties still surround both the maximum sea-level attained as well as the pattern of sea-level change throughout MIS 5e. Such uncertainties are exacerbated by the lack of a uniform approach to measuring and interpreting the geological evidence of paleo sea-levels. In this review, we discuss the characteristicsof MIS 5e field observations, and we set the basis for a standardized approach to MIS 5e paleo sea-level reconstructions, that is already successfully applied in Holocene sea-level research. Application of the standard definitions and methodologies described in this paper will enhance our ability to compare data from different research groups and different areas, in order to gain deeper insights into MIS 5e sea-level changes. Improving estimates of Last Interglacial sea-level is, in turn, a key to understand the behavior of ice sheets in a warmer world.

The Last Interglacial (MIS 5e, 128-116 ka) is among the most studied past periods in Earth’s history. The climate at that time was warmer than today, primarily due to different orbital conditions, with smaller ice sheets and higher sea-level. Field evidence for MIS 5e sea-level was reported from thousands of sites, but often paleo shorelines were measured with low-accuracy techniques and, in some cases, there are contrasting interpretations about paleo sea-level reconstructions. For this reason, large uncertainties still surround both the maximum sea-level attained as well as the pattern of sea-level change throughout MIS 5e. Such uncertainties are exacerbated by the lack of a uniform approach to measuring and interpreting the geological evidence of paleo sea-levels. In this review, we discuss the characteristicsof MIS 5e field observations, and we set the basis for a standardized approach to MIS 5e paleo sea-level reconstructions, that is already successfully applied in Holocene sea-level research. Application of the standard definitions and methodologies described in this paper will enhance our ability to compare data from different research groups and different areas, in order to gain deeper insights into MIS 5e sea-level changes. Improving estimates of Last Interglacial sea-level is, in turn, a key to understand the behavior of ice sheets in a warmer world.

Sargassum C. Agardh is one of the most diverse genera of marine macroalgae, and commonly inhabits shallow tropical and sub-tropical waters. This study aimed at investigating the effect of seasonality and the associated water-quality changes on the distribution, canopy cover, mean thallus length and biomass of Sargassum beds around Point Peron, Shoalwater Islands Marine Park, southwest Australia. Samples of Sargassum and seawater were collected every 3 mo from the summer of 2012 to the summer of 2014, from 4 different reef zones. A combination of in situ observations and WorldView-2 satellite remote-sensing images were used to map the spatial distribution of Sargassum beds and other associated benthic habitats. The results demonstrated strong seasonal variation in the physicochemical water parameters, canopy cover, mean thallus length, and biomass of Sargassum, which were significantly (p < 0.05) influenced by nutrient concentrations (PO43-, NO3-, NH4+) and rainfall. However, no significant variation in any studied parameter was observed among the 4 reef zones. The highest Sargassum biomass peaks occurred between late spring and early summer (from September to January). The results provide essential information to guide effective conservation and management, as well as sustainable utilisation of this renewable coastal marine resource.

Coral reefs occur extensively along the northwest Australian continental shelf in the Kimberley Bioregion (KIM), forming major geomorphic features along and just off the coast. These reefs have not been studied in as much detail as the offshore reefs and are poorly known due to the coastal conditions, including extremely high tide regimes, high turbidity and complex coastline morphology. This study aims to establish a regional-scale distribution map of exposed and intertidal reefs of the KIM and to classify the Kimberley reefs into types, adopting widely recognised reef classification and typology schemes. Remote sensing and Geographic Information Systems (GIS) were used in this study to process and produce digital maps as well as to provide some of the first detailed spatial analysis of reef distribution. Outcomes of this study showed that the Kimberley reefs possess strong morphological complexity and clear regional patterns. The study revealed that the number of Kimberley reefs and their area are considerably (60%) greater than previously thought; the total combined reefal area is approximately 1,950 km2. Fringing reefs have been identified as the dominant reef type and are widely distributed throughout the KIM. It was also found that tidal range affected the distribution of reef geomorphologies. The outcomes of this study will contribute to a better understanding of the Kimberley reefs, and provide marine park managers with essential and quality scientific information so that better management decisions can be made in this area.

This study uses information derived from cores to describe the Holocene accretion history of coral reefs in the macrotidal (up to 11 m tidal range) Buccaneer Archipelago of the southern Kimberley coast, Western Australia. The internal architecture of all cored reefs is broadly similar, constituting well-preserved detrital coral fragments, predominantly branching Acropora, in a poorly sorted sandy mud matrix. However, once the reefs reach sea level, they diverge into two types: low intertidal reefs that maintain their detrital character and develop relatively narrow, horizontal or gently sloping reef flats at approximately mean low water spring, and high intertidal reefs that develop broad coralline algal-dominated reef flats at elevations between mean low water neap and mean high water neap. The high intertidal reefs develop where strong, ebb-dominated, tidal asymmetry retains seawater over the low tide and allows continued accretion. Both reef types are ultimately constrained by sea level but differ in elevation by 3–4 m.

© 2016 Elsevier Ltd.The inner shelf Kimberley Bioregion of Northwest Australia is characterised by a macrotidal setting where prolific coral reefs growth as developed around a complex drowned landscape and is considered a biodiversity "hotspot". High-resolution shallow seismic studies were conducted across various reef settings in the Kimberley (Buccaneer Archipelago, north of Dampier Peninsula, latitude: between 16°40'S and 16°00'S) to evaluate stratigraphic evolution, interaction with different substrates, morphological patterns and distribution. Reef sites were chosen to assess most of the reef types present, particularly high intertidal planar reefs and fringing reefs. Reef internal acoustic reflectors were identified according to their shape, stratigraphic position and characteristics. Two main seismic horizons were identified marking the boundaries between Holocene reef (Marine Isotope Stage 1, MIS 1, last 12 ky), commonly 10-20 m thick, and MIS 5 (Last Interglacial, LIG, ~120 ky, up to 12 m thick) and Proterozoic rock foundation over which Quaternary reef growth occurred. Within the Holocene Reef unit, at least three minor internal reflectors, generally discontinuous, subparallel to the reef flat were recognised and interpreted as either growth hiatuses or a change of the coral framework or sediment matrix. The LIG reefs represent a new northernmost occurrence along the Western Australian coast. The research presented here achieved the first regional geophysical study of the Kimberley reefs. Subbottom profiles demonstrated that the surveyed reefs are characterised by a multi-stage reef buildup, indicating that coral growth occurred in the Kimberley during previous sea level highstands. The data show also that antecedent substrate and regional subsidence have contributed, too, in determining the amount of accommodation available for reef growth and controlling the morphology of the successive reef building stages. Moreover, the study showed that in spite of ma

Marine submerged aquatic vegetation (MSAV) naturally occurs on rubble and dead coral substrates in temperate and tropical coastal regions. During the growing season, MSAV develops to form dense canopy seaweed beds that play a vital role in coastal marine ecosystems and offer great potential to chemical, pharmaceutical, and bio-energy industries. At present, the total biomass and the distribution of the MSAV beds along the coast of Western Australia (WA) are not fully identified and quantified. Therefore, the application of satellite remote sensing data with high spatial resolution for examining the MSAV beds is required. The main objective of the present study was to assess and map the distribution of MSAV at two sites; Rottnest Island and Point Peron, Rockingham, WA, using WorldView-2 (WV2) satellite data. These study sites are important marine protected areas in WA waters with extraordinary documented biodiversity. By means of quantitative quadrat techniques, the MSAV canopy covers and fresh biomass data from the ground truth observations were assessed from September 2012 to December 2014. At Point Peron, the fresh biomass of Sargassum in the inter-tidal zone reached 5651.7±754.5, 5218.9±192.6, 1136.6±526.4, and 3472.2±434.2 g m-2 for spring, summer, fall, and winter, respectively. The overall accuracy of the minimum distance method was employed and yielded the highest accuracy rates of 90.93% (Kappa coefficient, k = 0.96) and 97.13% (k = 0.96) for Rottnest Island and Point Peron, respectively. The Mahalanobis classification with overall accuracy yielded 90.66% (k = 0.88) and 94.16% (k = 0.85) for Rottnest Island and Point Peron, respectively. The study results revealed that WV2 satellite data provided evidence of the high accuracy of MSAV classification.

© 2015 MTS.Marine submerged aquatic vegetation (SAV) plays a vital role as habitats, nursery and feeding grounds for a wide range of marine aquatic and terrestrial life. Recently, remote sensing techniques have been successfully applied in marine benthic mapping in coastal waters. However, the majority of these techniques have focused on either seagrasses meadows or coral reefs. There are a few studies that have been published validating a methodology for mapping SAV on brown macroalgae (Sargassum spp., Ecklonia spp.), seagrasses, and/or other macroalgae groups by spectral response from remote sensing. Hence, we studied the in-situ optical properties of living macroalgae, seagrasses, and rubble. The spectral characteristics of varied SAV groups were measured using the high resolution FieldSpec® 4 Hi-Res portable spectroradiometer. The study site selected was the Shoalwater Islands Marine Park, Rockingham, Western Australia as it is one of the fifteen biodiversity hotspots in Australia. Correlation and Principle Component Analysis were employed to evaluate the differences between SAV groups. The results have documented the spectral features of SAV and their associated habitats in Shoalwater Islands Marine Park, Western Australia, and developed a spectral library to distinguish among seagrass species and algae groups (green, red, and brown benthic macroalgae). The implications of this study will contribute to estimate and detect the distribution and seasonal variation of SAV on a broader scale.

An Early Cretaceous siliceous large igneous province (SLIP) that developed on the eastern margin of Gondwana produced some of the most voluminous siliceous volcaniclastic deposits known globally. We report U-Pb ages and trace-element and Hf-isotopic signatures of detrital zircons from the Madura Shelf (onshore Bight Basin), Western Australia. These zircons include a geochemically distinct 106 Ma component with age and Hf characteristics that match SLIP volcanics some 2300 km distant in eastern Australia. This young subpopulation shows limited grain abrasion, which contrasts with older detrital components that are stratigraphically persistent. Regional detrital zircon provenance demonstrates that sediment routing systems were disconnected in the eastern and western Bight Basin, negating terrestrial transport mechanisms as a possible vector of the zircons from the SLIP to their recovered position. Palynology indicates that the 106 Ma zircons are syn-depositional, and we interpret them as being significantly transported in an eruption plume. Given the grain size and distance from source, such distal zircon emplacement suggests previously undocumented 106 Ma super-eruptions. The 106 Ma zircons likely reflect Southern Hemisphere winter eruptions when tropospheric polar easterly winds would have been favored across southeastern Australia.

Coral reefs of the Kimberley Bioregion are seldom studied due to limited accessibility and extreme water conditions, which make management of these vital ecosystems a challenging task. Managing reef resources requires a considerable amount of credible, consistent and continual information. We identified the geographic information system (GIS) approach to be useful in developing an integrated geodatabase by acquiring information from different sources relating to the Kimberley reefs. Based on this approach, the study aimed to create a foundation for the first comprehensive geodatabase of the Kimberley reefs, called ReefKIM. The work included compiling existing spatial and non-spatial data, as well as collecting new data to complete information gaps. The study demonstrates how new technologies can be harnessed to crowdsource data from a wide range of people though a web-based platform. ReefKIM will provide a practical tool for scientists and managers to facilitate better monitoring and sustainable management of these vital natural resources. Moreover, it will support further studies in various disciplines leading to a more detailed understanding of the Kimberley Bioregion reefs.

Coral reefs are a major coastal feature of the Kimberley bioregion in north-western Australia; however, very little is known about the habitats and substrates of the reefs in this coast. Previous studies have been conducted on a broad scale, but no geomorphological, surface substrate and habitat maps of the reefs have been produced. Such maps would provide researchers and coastal zone managers with significant information and estimations of reef growth and productivity. The primary aim of this study was to obtain detailed information on reefs in the Kimberley bioregion. This study used remote sensing and Geographic Information Systems (GIS), as well as multiple other data sources, to map reef geomorphic zones and the associated key habitats and substrate types of shallow nearshore reefs. Despite the macrotidal regimes and the turbid waters of the study area, remote sensing was effectively used to identify the dominant habitats and substrate types of eight reef platforms. This study provides long-term quantitative assessments of the main habitats and substrates of these reefs and offers a better understanding of reefs in the Kimberly bioregion. It is also a source of valuable information for the marine park and coastal managers investigating the coral reefs that have been targeted for conservation, but have not yet been the subject of regional analysis.

Palaeoclimate research relevant to marine systems in Australia includes the collection and analysis of: (a) shallow-water and deep-sea corals, which provide highresolution archives, (b) deep-sea sediment and ice cores, which span longer time scales, and (c) palaeoclimate modelling, which gives us insights into mechanisms, dynamics and thresholds underlying past climate states. Palaeoclimate research in Australia is mature and well recognised internationally. To further advance Australian palaeoclimate research, we must address major challenges that include insufficient research vessel access, insufficient targeted research funding, as well as the lack of a well funded national centre to coordinate research efforts (e.g. academic institution or ARC Centre of Excellence for Palaeoclimate Research).

The coral reefs of the Kimberley bioregion are situated in an area that is considered a significant ‘biodiversity hotspot’ and are poorly known and of recognised international significance. This paper is a review of ongoing research as part of one of the first geoscientific reef studies of the Kimberley Biozone. Remote sensing, sub-bottom profiling and associated sedimentological work have been employed to produce a regional geodatabase of coral reefs and determine the Holocene internal architecture and growth history of the coral reefs. Satellite image analysis has revealed that fringing reefs in the Kimberley bioregion grow very well and differ geomorphologically from planar reefs both inshore and offshore. The acoustic profiles have depicted multiple reef build-ups, demonstrating the reefs’ long-term resilience. This research has provided a better understanding of the Kimberley reefs and demonstrated their capacity to succeed in challenging environments and generate habitats characterised by high complexity and species diversity.

Reef islands are unique landforms composed entirely of sediment produced on the surrounding coral reefs. Despite the fundamental importance of these ecological-sedimentary links for island development and future maintenance, reef island sediment production regimes remain poorly quantified. Using census and sedimentary data from Vakkaru island (Maldives), a sand-dominated atoll interior island, we quantify the major sediment-generating habitats, the abundance of sediment producers in these habitats, and the rates and size fractions of sediment generated by different taxa. The estimated annual sediment production is 685,000 kg (or 370 m3), ~75% of which is produced on the narrow outer reef flat, despite composing only 21% of the total platform area. Approximately 65% of the platform acts solely as a sediment sink. Census data identify parrotfish as the major sediment producers, generating >85% of the 5.7 kg m–2 of new sand-grade sediment produced on the outer reef flat each year. Halimeda (macroalgae) produce a further 10%, most as gravel-grade material. Comparisons between production estimates and sedimentary data indicate that reef ecology and island sedimentology are tightly linked; reef flat and lagoon sediments are dominated by coral and Halimeda, although fine- to medium-grained coral sand is the dominant (~59%) island constituent. The generation of sediment suitable for maintaining this reef island is thus critically dependent on a narrow zone of high-productivity reef, but most especially on the maintenance of healthy parrotfish populations that can convert reef framework to sand-grade sediment.

Australian scientists are world leaders in developing robust palaeo-environmental reconstructions from coral archives, relevant for understanding Australian climate extremes. The key issues for advancing this field are the need for high-resolution marine paleoclimate records to place the present in the context of past natural climate and sea level change, and to understand the impact of those changes on marine ecosystems. We call for sustained investment in paleoclimate science, infrastructure, and personnel to advance these critical areas of research.

Determining eustatic sea level during the Mid-Pliocene warm period (~3.3 to 2.9 Ma) has been a central but elusive goal in the study of past warm climates. Estimates of eustatic sea level based on geologic data span a broad range; variation that we now recognize is due in part to geographically varying post-depositional displacement caused by glacial isostatic adjustment and dynamic topography. In this study, we combine field observations and glacial isostatic adjustment modeling to estimate the dynamic topography signal in three areas that are important to paleo-sea level studies of the Mid-Pliocene warm period (South Africa, West Australia and southeastern United States). We show that dynamic topography played a significant role in the post-depositional displacement of Pliocene, and even younger Pleistocene, shorelines. In this regard, we provide a robust paleo-sea level elevation data set, corrected for glacial isostatic adjustment, that can be used to evaluate predictions from mantle flow models of dynamic topography.

In order to establish the ‘fingerprint’ of past sea level changes, many field measurements of paleo sea level from globally distributed locations are needed. It is because this problem requires a geographically expansive database that it becomes an ideal candidate for crowdsourcing techniques. In order to crowdsource sea level data from the Mid-Pliocene Warm Period, we developed three tools: PlioWiki, RSLcalc and RSLmap. PlioWiki is a web portal, open to contributions, where investigators can share knowledge on Pliocene to Quaternary relative sea levels. RSLcalc is a standardized, ready-to-use tool for field geologists to log their own sea level field observations and, if they desire, submit new data to an open access database of relative sea level markers. RSLmap allows one to visualize and query the database built with RSLcalc on a Google Map interface. Here we describe these tools and discuss the advantages of crowdsourcing, relative to traditional approaches, for the creation of sea level databases for any time period. Highlights: ► The creation of databases of relative sea level (RSL) markers can be crowd-sourced. ► To achieve this goal, PLIOMAX has created three tools: PlioWiki, RSLcalc and RSLmap. ► The tools can be used to build RSL datasets. ► They will therefore help scientists in creating past sea level ‘fingerprints’.

Proxy data suggest that atmospheric CO 2 levels during the middle of the Pliocene epoch (about 3g€‰Myr ago) were similar to today, leading to the use of this interval as a potential analogue for future climate change. Estimates for mid-Pliocene sea levels range from 10 to 40'm above present, and a value of +25'm is often adopted in numerical climate model simulations. A eustatic change of such magnitude implies the complete deglaciation of the West Antarctic and Greenland ice sheets, and significant loss of mass in the East Antarctic ice sheet. However, the effects of glacial isostatic adjustments have not been accounted for in Pliocene sea-level reconstructions. Here we numerically model these effects on Pliocene shoreline features using a gravitationally self-consistent treatment of post-glacial sea-level change. We find that the predicted modern elevation of Pliocene shoreline features can deviate significantly from the eustatic signal, even in the absence of subsequent tectonically-driven movements of the Earth's surface. In our simulations, this non-eustatic sea-level change, at individual locations, is caused primarily by residual isostatic adjustments associated with late Pleistocene glaciation. We conclude that a combination of model results and field observations can help to better constrain sea level in the past, and hence lend insight into the stability of ice sheets under varying climate conditions

Coral reef islands are among the most vulnerable environments on Earth to climate change because they are low lying and largely constructed from unconsolidated sediments that can be readily reworked by waves and currents. These sediments derive entirely from surrounding coral reef and reef flat environments and are thus highly sensitive to ecological transitions that may modify reef community composition and productivity. How such modifications - driven by anthropogenic disturbances and on-going and projected climatic and environmental change - will impact reef island sediment supply and geomorphic stability remains a critical but poorly resolved question. Here, we review the unique ecological-geomorphological linkages that underpin this question and, using different scenarios of environmental change for which reef sediment production responses can be projected, explore the likely resilience of different island types. In general, sand-dominated islands are likely to be less resilient than those dominated by rubble grade material. However, because different islands typically have different dominant sediment constituents (usually either coral, benthic foraminifera or Halimeda) and because these respond differently to individual ecological disturbances, island resilience is likely to be highly variable. Islands composed of coral sands are likely to undergo major morphological change under most near-future ecological change scenarios, while those dominated by Halimeda may be more resilient. Islands composed predominantly of benthic foraminifera (a common state through the Pacific region) are likely to exhibit varying degrees of resilience depending upon the precise combination of ecological disturbances faced. The study demonstrates the critical need for further research bridging the ecological-geomorphological divide to understand: (1) sediment production responses to different ecological and environmental change scenarios; and (2) dependant landform vulnerability. © 2

Carbonate platform evolution around the island of Rodrigues, southwestern Indian Ocean, is reconstructed from cores recovered across the platform's windward margin. In contrast to the classic "bucket-fill"model of carbonate platform evolution, whereby platform filling occurs predominantly as a function of the lagoonward transport of sediment from the reef rim, data from Rodrigues demonstrate that the primary mode of platform filling was through reef progradation from the platform interior seaward. Indeed, radiocarbon dates indicate that much of the platform interior had filled by ~2000 cal. (calibrated) yr B.P. Data also indicate that the reef rim probably caught up with sea level only in the past ~1000 yr, and subsequent export of sediment from those areas into the lagoon has probably only become important during the final stages of the platform's evolution. We interpret this as a function of the platform margin reef's catch-up growth mode. This would have allowed significant marine circulation within the platform interior, thus promoting active reef growth prior to sea level being attained. Given that such catch-up growth modes are widely recognized on many reef/platform margins, we suggest that this novel platform evolutionary model may have widespread applicability

Direct dating of fossil coral reefs using the U-series chronometer provides an important independent test of the Milankovitch orbital forcing theory of climate change. However, well-dated fossil corals pre-dating the last interglacial period (>130 thousand years ago; ka) are scarce due to, (1) a lack of sampling localities, (2) insufficient analytical precision in U-series dating methods, and (3) diagenesis which acts to violate the assumption of closed-system U-series isotopic decay in fossil corals.Here we present 50 new high-precision U-series age determinations for fossil corals from Henderson Island, an emergent coral atoll in the central South Pacific. U-series age determinations associated with the Marine Isotope Stage (MIS) 9 interglacial and MIS 7.5 interstadial periods are reported. The fossil corals show relatively little open-system U-series behaviour in comparison to other localities with fossil coral reefs formed prior to the last glacial cycle, however, open-system U-series behaviour is still evident in most of the dated corals. In particular, percent-level shifts in the [230Th/238U]act composition are observed, leading to conventional U-series ages that are significantly younger or older than the true sample age. This open-system U-series behaviour is not accounted for by any of the open-system U-series models, indicating that new models should be derived. The new U-series ages reported here support and extend earlier findings reported in Stirling et al. (2001), providing evidence of prolific coral reef development on Henderson Island at 320 ka, most likely correlated with MIS 9.3,and subsequent reef development at 307 ka during MIS 9.1, while relative sea-level was potentially 20 m lower than during MIS 9.3. The U-series ages for additional well-preserved fossil corals are suggestive of minor reef development on Henderson Island during MIS 7.5 (245–230 ka) at 240.3 ± 0.8 and 234.7 ± 1.3 ka. All U-series observations are consistent with the Milank

Assessments of carbonate platform reef–lagoon sediments and benthic habitats around Rodrigues Island (south-west Indian Ocean) have been undertaken in order to examine carbonate sediment texturalproperties and the controls on texturally-defined sediment fabrics. Reef–lagoon sediments, sampled from across the expansive (~8 km wide) carbonate-dominated windward platform, principally comprise poorly sorted medium- to coarse-grained bioclastic sands, composed of a low diversity of grain constituents — predominantly non-geniculate coralline algal bioclasts. Despite a marked homogeneity in sediment compositional and grain size properties, eight distinct sediment textural groups can be identified that form a heterogeneous mosaic across the contemporary reef–lagoon system. Only along the narrow outer platform margins (reef crest, sand apron and outermost lagoon environments) do we observe consistent (predictable) transitions in sediment textural groups, where physical processes are the primary drivers of selective sediment transport and sorting. In contrast, across the main expanse of the lagoon, the sediment substrates are characterised by an irregular mosaic of texturally-defined sediment groups — formed primarily as a function of sediment bio-retexturing. The burrowing activities of alpheid and callianassid shrimps are particularly important in this respect and impart a distinctly unique textural fabric to the upper sediment horizons in the environments in which the respective organisms occur. The consequence of this is that, at the platform system scale, individual, texturally-defined sediment groups are relatively poor indicators of prevailing hydrodynamic regimes or of local sediment production, reflecting more the biological action of organisms inhabiting the substrate. This has important implications for understanding the development of carbonate sediment fabrics in the context of palaeoenvironmental reconstructions and for interpreting a key diagnostic criteria of

Field observations and U-series ages reveal that Shark Bay, Western Australia (WA) has been inundated by the sea on at least three occasions during the Late Pleistocene/Holocene, resulting in a succession of marine deposits around the Bay. The exact age of these deposits has until now been problematic due to a lack of reliable and accurate age data. This study reports 16 new U-series coral dates from emergent reef deposits around Shark Bay, and point to an extended period of coral reef development during the peak of the last interglacial, marine isotope stage (MIS) 5e. This is attributed to enhancement of marine circulation within the reaches and basins, a result of higher sea levels and an absence of major sill and bank structures. Stromatolites are absent from the geological record within Shark Bay until the late Holocene, suggesting that sea levels and marine sedimentary processes that have operated during the present sea-level highstand are unique to this period. There is little direct evidence of fossil reef development occurring during interglacials of the middle/late Pleistocene (MIS 9/11).

A detailed geomorphologic and morphostratigraphic investigation of raised marine terraces at Cape Cuvier, Western Australia, reveals two morphologically distinct units. A lower, well-developed accretional reef terrace between 3 and 5.5 m above MLWS (mean low-water springs; hereafter denoted as “+”) represents an extended interval of stable sea level. An upper erosional terrace and incipient coralgal rim between + 8.5 to 10.5 m represents a brief sea-level stillstand at this higher elevation. These features suggest the lower and upper terraces developed during discrete sea-level events. In an attempt to better define the timing of emplacement of each marine unit, 20 coral samples collected along vertical and lateral reef growth axis from both terraces were analysed with U-series dating. Unfortunately, all coral samples exhibited elevated d234Uinitial values, suggesting that pervasive uptake of 234U-enriched uranium and 230Th thorium had occurred. Despite the shortcomings of absolute dating, a succession of events can be resolved though morphostratigraphic relationships. Comparison of the facies relationships, coral growth, and morphostratigraphic features between the lower and upper terraces indicates that an early to mid MIS 5e stillstand at + 3 to 5 m was followed by a late rise to + 8.5 to 10.5 m. This agrees with an emerging global view of MIS 5e sea-level history derived from stable carbonate platforms, rejecting the hypothesis that these higher sea-level benchmarks are an artefact of localized tectonic processes.

Marine and eolian carbonate deposits, grouped under the name “Tamala Limestone”, have been investigated along thousands of kilometers of coastal Western Australia (WA). Relative-age diagenetic features of carbonate sand dunes or “eolianites” indicate that coastal ridges decrease in age seaward, reflecting coastal accretion during successive sea-level stands. Yellow- to red-stained quartz sands are associated with eolianites as pits, lenses, extensive beds, and even 40-m-high dunes.A regional survey using whole-rock and land snail amino acid epimerization geochronology confirms the eolianite succession and provides a means of correlating widespread deposits along a steep climatic gradient and 16° of latitude. AMS 14C and uranium–thorium (U/Th) ages provide independent radiometric calibration of the amino acid ratios, and eolianite ages can be estimated using a parabolic kinetic model.Over 90% of the sampled eolianite deposits comprise Aminozones A, C, E (125 ka), F?, G, and H, and correlate with interglacials from <10 ka (Holocene) to ca. 500 ka. In contrast, at the type locality of the Tamala Limestone along the Zuytdorp Cliffs, the upper eolianite-paleosol units are characterized by advanced stages of cavernous weathering, pedogenesis, and recrystallization. In the same units, sediment and snail samples generally yield very low or non-detectable levels of amino acids. These factors along with the stratigraphic complexity of the deposits reflect an age much greater than a large majority of sites along the WA coastline. These findings encourage a revision of the existing classification and nomenclature of Quaternary carbonate deposits in WA, as well as a reexamination of the underlying mechanisms related to the formation and emplacement of both carbonate and quartz dunes.