The findings carry particular weight because they demonstrate that earlier underwater discoveries at Murujuga, first reported by the Deep History of Sea Country project in 2020 and again in 2023, were not isolated anomalies. Instead, they form part of a broader submerged cultural landscape spread across a region now inscribed on the World Heritage list. For archaeologists studying the deep history of the Australian continent, this distinction between a single lucky find and an extensive, patterned distribution of cultural material is fundamental. It means the seabed around Murujuga can be studied systematically, with sites predicted, located and interpreted in relation to one another, much as terrestrial landscapes are.

The scale of what was lost to the sea is difficult to overstate. More than two million square kilometres of Australia’s continental shelf was submerged as sea levels rose following the end of the last Ice Age, a process that unfolded over thousands of years as ice sheets melted and ocean basins filled. Before that transformation, generations of First Nations peoples lived across landscapes that now lie beneath the ocean, including coastal plains, river valleys and freshwater springs that would have made the region attractive for settlement. The newly documented sites offer a rare, direct window into that drowned world, capturing two distinct kinds of places within what was once dry, connected land.

The first of these sites centres on an ancient freshwater spring, a feature that would have been nothing short of vital in the arid northwest. Reliable water sources in such environments act as anchors for human activity, drawing people together for drinking, food procurement, social gatherings and ceremony. The presence of stone artefacts associated with the spring is consistent with such a pattern of congregation, indicating that this spot on the now-submerged plain was a focal point in the lives of the people who used it. The second site tells a different story: it is associated with a rocky hill overlooking an ancient river channel, a vantage point that would have offered both practical advantages and a different set of resources. Together, the two sites show how people used different parts of the landscape when the archipelago was still connected by dry land, moving between springs, hills and watercourses in ways that structured their daily and seasonal lives.

Among the most technically significant results of the analysis is evidence of raw material selection and transport. Some of the artefacts were made from stone sourced from around Rosemary Island, approximately 23 kilometres from where they were ultimately found on the seabed. That distance matters. It suggests that people deliberately moved valuable stone resources across a landscape that is now entirely underwater, carrying preferred raw materials over considerable distances either for immediate use or as part of broader exchange and mobility patterns. In archaeological terms, such transport demonstrates decision-making about stone quality, availability and curation, and it provides a measurable link between distinct places within the drowned landscape, effectively reconstructing ancient connections that no land-based survey could ever recover.

The research is the product of a partnership between underwater archaeology researchers from Flinders University, The University of Western Australia, James Cook University and the University of York in the United Kingdom, working with the Murujuga Aboriginal Corporation and its Rangers. Crucially, the collaboration was not a token consultation. Rangers from the Murujuga Aboriginal Corporation Land and Sea Unit trained as scientific divers and worked alongside the archaeologists to locate and document the underwater cultural sites. Malik Churnside and Richard Variakojis, Rangers from the Land and Sea Unit and co-authors on the paper, undertook scientific diver surveys and made some of the underwater discoveries themselves, embedding Indigenous expertise and custodianship directly into the scientific process.

Lead researcher Professor Jonathan Benjamin, a specialist in marine archaeology at Flinders University’s College of Human Sciences and Culture, emphasised the value of working beside trained Indigenous Rangers who actively contributed to this challenging scientific research. Underwater survey in this environment is far from straightforward: visibility, currents, tides and the sheer difficulty of recognising cultural material on a seabed that has been reshaped by thousands of years of marine processes all combine to make such work demanding. Recognising a stone artefact amid natural rock, and distinguishing a deliberate human deposit from geological scatter, requires both archaeological training and an intimate understanding of the country in question, which is precisely what the partnership model provides.

For the Ngarda-Ngarli people, the Traditional Owners of the region, the findings confirm an understanding of Country that has never been confined to what is above the waterline. Vincent Adams, Director of the Murujuga Aboriginal Corporation, noted that the Ngarda-Ngarli people have cared for Murujuga for at least 50,000 years, and that the research shows their cultural landscape extends far beyond the shoreline and into Sea Country, where important parts of their story remain preserved beneath the sea. In Aboriginal and Torres Strait Islander frameworks, Sea Country is not an empty marine space but a living part of Country, holding ancestral connections, responsibilities and knowledge. The archaeological evidence now aligns with that understanding in a form recognised by mainstream science.

Adams also pointed to the implications of the region’s World Heritage recognition, observing that it brings new responsibilities as well as global recognition, and that research of this kind strengthens the community’s ability to identify, understand and protect the whole Murujuga cultural landscape, including Country that was submerged when sea levels rose thousands of years ago. That protective dimension is significant. Submerged heritage is vulnerable to industrial activity, anchoring, dredging and other seabed disturbances, and it is far less visible, and far less legally established, than terrestrial archaeology. Documented sites, mapped distributions and published evidence give custodians and regulators a concrete basis for managing what lies beneath the water with the same seriousness applied to heritage on land.

The study, an observational study published in Quaternary Science Reviews under the DOI 10.1016/j.quascirev.2026.110307, builds on the landmark discoveries reported in 2020 and 2023 by the Deep History of Sea Country project team, and its authors are affiliated with the ARC Centre of Excellence for Indigenous and Environmental Histories and Futures. The authors declare no known competing financial interests or personal relationships that could have appeared to influence the work. Taken together, the discoveries reframe the drowned continental shelf not as a void between archaeological sites but as an integral, preserved component of Australia’s deep human history, one in which freshwater springs, rocky hills and transported stone record the movements and decisions of people whose world the ocean swallowed at least 9,000 years ago, and whose descendants continue to read that story from beneath the waves.

Subject of Research: Submerged Aboriginal archaeological sites and stone artefact transport on the drowned cultural landscape of Murujuga, Western Australia

Article Title: Australia’s oldest underwater archaeology reveals ancient life within a lost landscape

Article References: Australia’s oldest underwater archaeology reveals ancient life within a lost landscape. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: underwater archaeology, Murujuga, Aboriginal heritage, sea-level rise, Quaternary Science Reviews, continental shelf, stone artefacts, Rosemary Island, Sea Country, Flinders University, last Ice Age, World Heritage

The shortcut in question is loss-on-ignition, or LOI, a technique beloved by monitoring agencies because it is fast, cheap and requires nothing more exotic than a furnace and a balance. A dried sediment sample is heated to 450 degrees Celsius for four hours, and the mass it loses is taken as a proxy for its organic matter content. Because organic carbon typically makes up only a fraction of that organic matter, the LOI value must then be converted into a total organic carbon, or TOC, estimate using a regression equation. The trouble, as the new study demonstrates, is that this conversion is not universal. It shifts with sediment composition, mineralogy and analytical protocol, meaning that a formula calibrated in one setting can quietly mislead in another.

The stakes are far from academic. Continental shelves cover roughly nine percent of the global seafloor, yet the top metre of subtidal, non-vegetated marine sediments is estimated to contain more than 2.3 trillion tonnes of organic carbon and to accumulate between 126 and 350 million tonnes each year. Fine-grained shelf deposits, including the Western Irish Sea mud belt, are recognised as hotspots of carbon accumulation, where silts and clays settling from suspension in low-energy waters carry organic matter down into long-term storage. Ireland’s Exclusive Economic Zone spans roughly 450,000 square kilometres, about ten times its land area, but its seabed carbon inventory remains poorly constrained despite years of mapping and sampling effort.

To test whether a single conversion equation could really serve such a varied environment, the team assembled an unusually rich dataset spanning surveys conducted between 2010 and 2023, drawing on the national INFOMAR mapping programme, Marine Institute monitoring cruises and the QUEST research project. Grab samples, box cores, gravity cores and vibrocores collected from the RV Celtic Voyager, RV Keary and RV Celtic Explorer yielded sediments ranging from coastal shallows less than five metres deep to the central basin at around 115 metres. Grain size was measured by laser diffraction, iron concentrations by portable X-ray fluorescence, and TOC by combustion elemental analysis after careful acid removal of carbonate carbon. Crucially, a subset of samples was analysed by both LOI and direct TOC methods, allowing the researchers to calibrate one against the other.

The paired measurements correlated strongly across the whole dataset, with a coefficient of determination of 0.948, and the baseline Western Irish Sea model took the form TOC equals 0.41 times LOI minus 0.18. That might sound like a success story, and in aggregate it is. But the residuals told a subtler tale. The pooled equation slightly over-predicted carbon in sandy, low-carbon samples and under-predicted it in carbon-rich muds, hinting that a single line was being forced through what were really two different populations of sediment.

Statistical tests made the split explicit. Chow tests, which probe whether a relationship changes abruptly across a threshold, identified significant structural breaks in the LOI-to-TOC relationship at 0.99 percent iron, 19.8 percent mud content and 29.6 metres water depth. Analysis of covariance confirmed that the regression slopes genuinely differed between the groups. The high-mud slope of 0.42 was nearly double the low-mud slope of 0.24, meaning that a given loss-on-ignition value corresponds to almost twice as much organic carbon in fine, deeper sediments as it does in shallow, sand-dominated ones. Mean TOC-to-LOI ratios reinforced the pattern, reaching 0.34 in fine sediments against just 0.20 in coarse ones.

The physical explanation lies in how minerals shelter organic matter from decay. Fine-grained matrices rich in clay minerals and iron or manganese oxides can bind organic molecules and protect them from microbial attack, allowing more carbon to persist per unit of organic matter. Iron phases such as oxyhydroxides and sulfides co-accumulate with organic carbon in quiet, fine-grained or oxygen-poor settings, which is why the iron threshold emerged as the strongest independent statistical split. The researchers are careful, however, to frame iron and water depth as proxies for depositional environment rather than proven causal controls, since all three variables co-vary with the fundamental grain-size regime of the seafloor.

Splitting the dataset at the 19.8 percent mud threshold produced group-specific models that improved fit markedly for high-mud sediments, reaching a coefficient of determination of 0.97, while the low-mud model, at 0.72, retained greater uncertainty. That asymmetry matters. In coarse sediments, where organic content is low and absolute LOI values are small, estimates are acutely sensitive to minor inorganic mass losses, structural water released from clays, salt effects and seasonal inputs of organic material. Prediction uncertainty is greatest in exactly these low-carbon sands, particularly for samples near the classification threshold, and the authors caution that extrapolating the fitted intercepts to near-zero LOI values is unreliable.

The study is equally candid about its own limits. The paired LOI-TOC subset is smaller than the full metadata set, group sizes are uneven at 18 high-mud and 59 low-mud samples, and the thresholds were chosen through exploratory analysis without independent validation. LOI itself, even when carefully performed, cannot match the specificity of direct combustion analysis, since ignition at 450 degrees Celsius drives off not only organic matter but also clay structural water and other volatile components. The authors stress that their models convert LOI to estimated TOC only; they do not by themselves quantify carbon stocks, accumulation rates, burial rates or climate-mitigation potential, all of which require dry bulk density, sediment thickness, spatial data, chronological constraints and rigorous propagation of uncertainty.

What the study does offer is a practical blueprint. Rather than treating LOI as a poor substitute for elemental analysis, the researchers position it as a way to extend the spatial reach of existing datasets, unlocking carbon estimates from archived samples where LOI was measured but TOC was not, provided paired calibration, sediment-class metadata and uncertainty estimates accompany the conversion. Just as importantly, the work demonstrates how routine geotechnical measurements, grain-size data and monitoring samples from mapping programmes, regulators, ports, offshore energy developers and commercial surveys can be woven together into national carbon inventories, reducing duplicated sampling and strengthening the evidence base on which marine spatial planning, protected area design and blue carbon accounting increasingly depend.

Subject of Research: Region-specific loss-on-ignition to total organic carbon conversion models for estimating blue carbon in Western Irish Sea marine sediments

Article Title: Region-specific LOI–TOC conversion models for marine sediment blue carbon assessment in the Western Irish Sea

Article References: Grey, A., Mhaoldomhnaigh, C. N., Chatting, M., Walsh, P., Lee, A., Kelleher, B., & Coughlan, M. (2026). Region-specific LOI–TOC conversion models for marine sediment blue carbon assessment in the Western Irish Sea. Environmental Monitoring and Assessment, 198(10), Article 1078. https://doi.org/10.1007/s10661-026-15918-6

Image Credits: AI Generated

DOI: 10.1007/s10661-026-15918-6

Keywords: blue carbon, marine sediments, loss-on-ignition, total organic carbon, Western Irish Sea, continental shelf, sediment classification, mud content, iron geochemistry, carbon stock assessment, seabed mapping, organic matter preservation

Silicate weathering is one of the fundamental thermostats of the Earth system. When rainwater, charged with atmospheric carbon dioxide in the form of carbonic acid, attacks silicate minerals in rocks, the carbon is converted into dissolved bicarbonate and carried by rivers to the ocean, where much of it is ultimately buried in carbonate sediments. Over geological timescales, this process acts as a long-term sink for atmospheric CO2, and its intensity is conventionally assumed to track temperature and runoff: hot, humid climates accelerate chemical denudation, while cold, dry glacial climates slow it down. That assumption underpins much of how scientists model the carbon cycle over glacial-interglacial cycles, which is precisely why the new findings are so consequential. The study suggests that during the very intervals when the conventional model predicts weakened weathering, an enormous and previously overlooked weathering engine was running at full tilt on the exposed mid-latitude shelves of East Asia.

The evidence comes from Site CSDP-1, a core recovered by the Chinese Continental Shelf Drilling Program in the South Yellow Sea. The team conducted a comprehensive analysis of the mineralogical and geochemical properties of the sediments, layer by layer, building a continuous archive that spans six hundred millennia of alternating glacial and interglacial conditions. Among the key indicators they examined was the Chemical Index of Alteration, or CIA, a widely used proxy that measures the degree to which feldspars and other primary silicate minerals have been chemically transformed into clay minerals through hydrolysis. They also tracked the ratio of potassium to aluminum, K/Al, which decreases as labile potassium-bearing minerals are leached away during weathering, and the ratio of smectite to illite plus chlorite, which captures the balance between newly formed alteration products and relatively unweathered detrital minerals transported from the river basin.

All of these proxies told the same story. The weathering intensity recorded in glacial shelf sediments was consistently and markedly higher than that recorded in interglacial sediments. In quantitative terms, the team calculated that the rate of carbon consumption through silicate weathering during glacial periods was approximately 1.5 times that of interglacial periods. This inversion of the expected pattern, in which colder climates should yield weaker chemical denudation, is the heart of the discovery. The researchers interpret it as evidence that glacial weathering on the shelf was decoupled from climate in the conventional sense. It was not temperature or precipitation over the source basin that controlled the signal, but rather the physical state of the sediment itself and the amount of time it spent exposed at the surface.

The mechanism hinges on sea level. During glacial periods, global sea level fell by well over a hundred meters as water was locked into continental ice sheets. This regression exposed the loosely consolidated, unconsolidated sediments that had accumulated on the continental shelf during earlier highstands. Rather than being rapidly buried beneath the ocean, these fine-grained deposits were left stranded on the emergent plain, where they remained for thousands of years, subjected to repeated wetting and drying, oxidation, and infiltration by CO2-charged meteoric water. Because the sediments were fine-grained, freshly deposited, and largely unweathered when first delivered by the Yellow River, they presented an enormous reactive surface area to chemical attack. The long residence time of these materials on the exposed shelf gave weathering reactions the opportunity to proceed far beyond what would have been possible had the sediment been quickly sequestered on the seafloor.

Interglacial conditions reversed this arrangement. As sea level rose, the river mouth retreated landward and the previously exposed shelf was flooded once more. Fine-grained material eroded from the basin was then rapidly transported through the estuary and dispersed across the shelf and into the deep sea, sharply reducing both the time and the space available for reweathering of the sediment. In other words, the same sediment that lingered and weathered during glacial lowstands was efficiently exported and buried during highstands. The sediment routing system, rather than the climate system, emerged as the dominant control on chemical weathering intensity in this basin-shelf configuration, a conclusion that challenges how weathering signals in marine sediments are commonly interpreted.

To appreciate the scale of the overlooked sink, the researchers extended their quantitative estimates beyond the Yellow Sea. Taking into account the exposed shelves of the Yellow Sea and the East China Sea, along with comparable low-latitude marine areas that experience similar sea-level-driven exposure, they calculated that the increased silicate weathering of shelf sediments during glacial periods may account for approximately 9.3 percent of the total reduction in atmospheric CO2 during glacial times. For a mechanism that had previously gone essentially unrecognized in glacial carbon budgets, nearly a tenth of the glacial drawdown is a substantial contribution. It implies that the mid-latitude shelf region functioned as an active and underestimated silicate weathering carbon sink precisely during the intervals when the global climate was coldest and atmospheric CO2 was at its lowest.

This finding also reframes comparisons with earlier work in low-latitude seas, where enhanced glacial weathering had been documented but attributed to specific tropical conditions. The new study demonstrates that the phenomenon is not confined to the tropics. Mid-latitude shelves fed by major sediment-discharging rivers, of which the Yellow River is one of the largest on Earth, can host equally vigorous weathering during lowstands. Given the abundance of such river-shelf systems around the world, from the Sunda Shelf of Southeast Asia to the shelves of other major river depocenters, the implication is that shelf weathering may be a globally significant and systematically underestimated term in glacial carbon cycle accounting.

Methodologically, the study is notable as the first quantitative reconstruction of the Late Quaternary history of silicate weathering carbon consumption in the Yellow River basin-continental shelf system. By combining multiple independent weathering proxies with calculated carbon consumption fluxes, the team was able to move beyond qualitative statements about alteration intensity and place firm numbers on the carbon sink, both through time at the study site and extrapolated across the broader shelf systems of the western Pacific margin. The 600,000-year record captures numerous glacial-interglacial cycles, giving the researchers the statistical confidence to distinguish a systematic glacial enhancement of weathering from episodic or local effects.

The broader significance of the work lies in the perspective it opens for understanding the mechanisms of glacial-interglacial climate evolution. If exposed continental shelves acted as a meaningful carbon sink during ice ages, then models of the glacial carbon cycle must incorporate sea-level-driven shelf exposure as a first-order process, alongside the ocean’s biological pump, changes in ocean circulation, and carbonate compensation dynamics that have traditionally dominated the discussion. The study, authored by Zhang, Wan, and colleagues in SCIENCE CHINA Earth Sciences, thus adds a continental margin process to the roster of mechanisms that helped the planet cool into glacial states and, by implication, helped release that carbon as shelves were reflooded during deglaciation. For a field that has long focused its attention on the open ocean and the terrestrial biosphere, the message from the muddy floor of the South Yellow Sea is that some of the most important carbon chemistry of the ice ages may have happened in plain sight, on land that is now underwater.

Subject of Research: Enhanced silicate weathering on the South Yellow Sea continental shelf during glacial periods and its role in the glacial carbon cycle

Article Title: Enhanced silicate weathering on the South Yellow Sea shelf during glacial periods and its influence on the glacial carbon cycle

Article References: Enhanced silicate weathering on the South Yellow Sea shelf during glacial periods and its influence on the glacial carbon cycle. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: silicate weathering, South Yellow Sea, continental shelf, glacial periods, carbon cycle, atmospheric CO2, sea level, Chemical Index of Alteration, Yellow River, CSDP-1, Science China Earth Sciences, Quaternary climate