Michael O'Leary's research while affiliated with University of Western Australia and other places

Publications (71)

Preprint
Several physical, chemical, and biological processes shape coastal environments close to sea level. Acting through time, these processes create a variety of coastal landforms. When found outside their environment of formation, these landforms can be used by geoscientists as geomorphological indicators of former relative sea levels. In this chapter,...
Preprint
Understanding sea level during the warmest peak of the Last Interglacial (125,000 yrs ago; Marine Isotope Stage 5e) is important for assessing future ice-sheet dynamics in response to climate change, and relies on the measurement and interpretation of paleo sea-level indicators, corrected for post-depositional vertical land motions. The coasts and...
Article
Reef islands are low-lying sedimentary landforms formed from the accumulation of unconsolidated skeletal material generated by carbonate-producing reef organisms. The coupling between ecological (extant community assemblage) and sedimentary processes (sediment composition and supply) that maintain these reef-fronted landforms make them increasingly...
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Palaeoshorelines and associated palaeo-coastal features are studied to reconstruct past sea level, climate, and depositional environments. Their identification typically depends on direct field observations and is therefore challenging in marine environment, where the interpretation mostly relies on sparse geophysical data. This review presents, ba...
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Bedforms are key components of Earth surfaces and yet their evaluation typically relies on manual measurements that are challenging to reproduce. Several methods exist to automate their identification and calculate their metrics, but they often exhibit limitations where applied at large scales. This paper presents an innovative workflow for identif...
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Regional-scale assessments have proven to be invaluable frameworks for research, public engagement and management of submerged archaeological landscapes. Regional-scale approaches have been implemented internationally through a variety of academic or strategic studies. Such studies represent a much-needed next step towards subregional and site-leve...
Article
Whitney et al. (2021) challenge our conclusions about rates of deformation and amount of uplift along the Cape Range, Western Australia, particularly the elevation constraints we place on the last interglacial shoreline along the northern half of Cape Range. They selectively focus almost entirely on the northern half of Cape Range, completely omitt...
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High-resolution bathymetry forms critical datasets for marine geoscientists. It can be used to characterize the seafloor and its marine habitats, to understand past sedimentary records, and even to support the development of offshore engineering projects. Most methods to acquire bathymetry data are costly and can only be practically deployed in rel...
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Turbidity impacts the growth and productivity of marine benthic habitats due to light limitation. Daily/monthly synoptic and tidal influences often drive turbidity fluctuations, however, our understanding of what drives turbidity across seasonal/interannual timescales is often limited, thus impeding our ability to forecast climate change impacts to...
Article
Recent studies conducted in Murujuga Sea Country have confirmed that Indigenous Australian archaeology does not end at the modern shore. Since the earliest peopling of the Australian continent, sea levels have fluctuated significantly, dropping as much as 130 m below modern mean sea-level during the Last Glacial Maximum (LGM). During this period, t...
Preprint
High-resolution bathymetry is a critical dataset for marine geoscientists. It can be used to characterize the seafloor and its marine habitats, to understand past sedimentary records and even to support the development of offshore engineering projects. Most methods to acquire bathymetry data are costly and can only be practically deployed on relati...
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Increasing evidence suggests that coral reefs exposed to elevated turbidity may be more resilient to climate change impacts and serve as an important conservation hotspot. However, lo-gistical difficulties in studying turbid environments have led to poor representation of these reef types within the scientific literature, with studies using differe...
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Coral reef islands are among the most vulnerable landforms to climate change. However, our understanding of their morphodynamics at intermediate (seasonal to interannual) timescales remains poor, limiting our ability to forecast how they will evolve in the future. Here, we applied a semi-automated shoreline detection technique (CoastSat.islands) to...
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A carbonate budget is a comprehensive measure of reef health and function that focuses on processes that produce and remove carbonate. A key parameter of a carbonate budget is reef topographic complexity, or rugosity, that is traditionally measured by the chain-and-tape (CT) method. However, to overcome spatial limitations of the CT method, modern...
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Here, we utilise a unique, 70-year-long (1949-2017), high-resolution historical aerial imagery dataset to track changes to coral reef structures in Bill's Bay on the Ningaloo coast. Reef habitat was distinguished from sand and rubble substrates based on imagery grey-scale values and autoclassified using unsupervised image analysis in ArcMap. This a...
Article
Over the last 20,000 years, one third of the continental land mass of Australia, or 2.12 million km 2 , has been drowned by postglacial sea-level rise. Much of this drowned territory is thought to have been occupied by humans. Where archaeological remains have survived inundation, they can be investigated by underwater and airborne remote sensing,...
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During the past 20,000 years approximately one-quarter of the continental landmass of Australia was inundated by postglacial sea-level rise, submerging archaeological evidence for use of these landscapes. Underwater archaeological sites can offer substantial insights into past lifeways and adaptations to rapidly changing environments, however the v...
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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 elevatio...
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The Dampier Archipelago (Murujuga) is on Australia’s National Heritage List because of its significant rock art and numerous stone structures. When people first started living in this arid landscape of the north-west coast, 50,000 years ago, the shoreline was 160 kilometres further north-and west. The Archipelago was created around 7,000 years ago,...
Article
Laterally continuous terraces along the western flank of Cape Range, Western Australia, record both past sea-level highstands and postdepositional vertical displacement. Four distinct fossil coral reef terraces extend nearly the entire length of the slowly uplifting anticlinal structure (∼100 km), enabling documentation of the timing and degree of...
Article
Almost 2 million square km of Australia’s continental shelf was flooded following the termination of the last glacial maximum, and with it the cultural heritage of the first arrival and coastal occupation of Australia beginning some 65,000 years ago. In order to prospect for this missing cultural record, we must first identify submerged coastal lan...
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This article reports Australia’s first confirmed ancient underwater archaeological sites from the continental shelf, located off the Murujuga coastline in north-western Australia. Details on two underwater sites are reported: Cape Bruguieres, comprising > 260 recorded lithic artefacts at depths down to −2.4 m below sea level, and Flying Foam Passag...
Article
The southern Nullarbor Plain is covered by low amplitude (generally 1–2 m) parallel ridges and swales with variable wavelength (300–900 m). The ridges are stony; the swales hold thin deposits of unconsolidated silt and clay. The ridges and swales have previously been attributed to joint control but are not parallel to joints exposed in cave roofs....
Article
Abstract The Mid‐Pliocene Warm Period (MPWP, 2.9 to 3.3 Ma), along with older Pliocene (3.2 to 5.3 Ma) records, offers potential past analogues for our 400‐ppmv world. The coastal geology of western and southern coasts of the Republic of South Africa expose an abundance of marine deposits of Pliocene and Pleistocene age. In this study, we report di...
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Extreme climate events, such as the El Niños in 1997/1998 and 2015/16, have led to considerable forest loss in the Southeast Asian region following unprecedented drought and wildfires. In Borneo, the effects of extreme climate events have been exacerbated by rapid urbanization, accelerated deforestation and soil erosion since the 1980s. However, st...
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High-resolution shallow seismic profiles collected along the inner shelf in Geographe Bay (south-west Australia) illustrate a highly-variable buried architecture. Three main acoustic units, separated by unconformities, correspond to different geological facies, deposited under various sea-level conditions. The acoustic basement (Unit B) belongs to...
Article
Following from previous research in Western Australia, this study explores the use of embedded microfossils—including bryozoan and foraminiferal fossil assemblages—to help identify source and distribution of fossiliferous chert artefacts from South Australian archives. Artefacts from key archaeological sites include Allen’s Cave, Koonalda Cave, Wil...
Article
Eocene fossiliferous chert is a distinctive rock used in the manufacture of stone artefacts commonly found in archaeological sites in southwestern Western Australia (WA). In this study, we employ non-destructive high-resolution X-ray computer tomographic (CT) imaging at the Australian Synchrotron to map and identify embedded bryozoan (and other) fo...
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Underwater archaeology and submerged landscapes in Western Australia—ERRATUM - Volume 92 Issue 364 - Jonathan Benjamin, Michael O'Leary, Ingrid Ward, Jorg Hacker, Sean Ulm, Peter Veth, Mads Holst, Jo McDonald, Peter J. Ross, Geoff Bailey
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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 sit...
Poster
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We reconstruct the spatio-temporal dynamics of sea surface temperature, light availability and oxygen isotopic composition of seawater based on paired stable isotope (oxygen, carbon) and Sr/Ca measurements on coral cores obtained from three sites within the Miri-Sibuti Coral Reef National Park, Borneo, Malaysia. Our results reveal distinct seasonal...
Article
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 Cretac...
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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) b...
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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 fo...
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The mid-shelf reefs of the Kimberley Bioregion are one of Australia’s more remote tropical reef provinces and such have received little attention from reef researchers. This study describes the geomorphology and late Holocene accretion history of Adele Reef, a mid-shelf platform reef, through remote sensing of contemporary reef habitats, shallow se...
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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 m...
Article
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...
Article
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...
Article
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 tur...
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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,...
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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, predomina...
Article
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) appro...
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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...
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The deep-sea environment is among the most stable on Earth, making it well suited for amino acid geochronology. Foraminifera with calcareous tests are distributed across the World Ocean and are often recovered in sufficient abundance from sediment cores to derive robust mean amino acid D/L values of multiple replicates from each stratigraphic level...
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Proxy data suggest that atmospheric CO2 levels during the middle of the Pliocene epoch (about 3Myr 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 40m above present, and a value of +25m is often adopted in numerical climate mode...
Article
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 analyti...
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Full-text of this article is not available in this e-prints service. This article was originally published following peer-review in Quarternary Geochronology, published by and copyright Elsevier. We appreciate the opportunity to respond to the comments of Mr. Bastian, and are pleased to learn that he agrees that carbonate eolianites, so common as s...
Article
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 textural properties and the controls on texturally-defined sediment fabrics. Reef–lagoon sediments, sampled from across the expansive (~ 8 km wide) carbonate-domin...
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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 leve...
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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...
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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...
Article
Robust, independent age constraints on the absolute timing of climate events based on the U-series dating of fossil coral are sparse before the last glacial cycle. Using multiple-collector inductively coupled plasma mass spectrometry with multiple-Faraday protocols, we are able to date ˜ 600 ka samples with an uncertainty of better than ± 15 ka (2s...
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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...
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The geomorphology and morphostratigraphy of numerous worldwide sites reveal the relative movements of sea level during the peak of the Last Interglaciation (Marine Isotope Stage (MIS) 5e, assumed average duration between 130±2 and 119±2 ka). Because sea level was higher than present, deposits are emergent, exposed, and widespread on many stable coa...
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The opening sentence of the introduction [Dumas, B., Hoang, C.-T., Raffy, J., 2006. Record of MIS 5 sea-level highstands based on dated coral terraces of Haiti. Quaternary International 145–146, 106–118] “Quaternary sea-level changes are mainly deduced from the study of raised coral terraces” involves a flawed premise. As two undefined variables op...