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The Azraq oasis in the Eastern Desert of Jordan has produced considerable stone artefacts attributed to the early Palaeolithic, yet relatively few data are available regarding the chronology and palaeoenvironmental contexts of the remains. In this study, we present stratigraphic, sedimentological, and micropalaeontological analyses of the Late Acheulean site SM1 located within the former Shishan Marsh, which we combine with geochronological and sedimentological data from 13 neighbouring geological exposures to reconstruct landscape evolution at the western margin of the Shishan Marsh. We then discuss the Late Quaternary palaeolandscapes of the Greater Azraq Oasis Area over the past c. 350 ka. Our work demonstrates that the central Azraq Basin experienced three local wetting-drying cycles since the late Middle Pleistocene that would have dramatically shifted the quantity and distribution of freshwater resources, ranging from expansive wetland landscapes to desert refugia characterised by isolated spring pools—changes that would have significantly impacted the mobility decisions and settlement patterns of Palaeolithic inhabitants. Our study highlights that developing long-term records of human-environment dynamics in arid environments requires a mosaic approach to palaeoenvironmental reconstruction that is nested within a well-developed understanding of landscape evolution.

Strontium isotopes (87Sr/86Sr) are useful to trace processes in the Earth sciences as well as in forensic, archaeological, palaeontological, and ecological sciences. As very few large-scale Sr isoscapes exist in Australia, we have identified an opportunity to determine 87Sr/86Sr ratios on archived fluvial sediment samples from the low-density National Geochemical Survey of Australia. The present study targeted the northern parts of Western Australia, the Northern Territory, and Queensland, north of 21.5∘ S. The samples were taken mostly from a depth of ∼60–80 cm in floodplain deposits at or near the outlet of large catchments (drainage basins). A coarse ( mm) grain-size fraction was air-dried, sieved, milled, and digested (hydrofluoric acid + nitric acid followed by aqua regia) to release total Sr. The Sr was then separated by chromatography, and the 87Sr/86Sr ratio was determined by multicollector inductively coupled plasma mass spectrometry. The results demonstrate a wide range of Sr isotopic values (0.7048 to 1.0330) over the survey area, reflecting a large diversity of source rock lithologies, geological processes, and bedrock ages. The spatial distribution of 87Sr/86Sr shows coherent (multi-point anomalies and smooth gradients), large-scale (>100 km) patterns that appear to be broadly consistent with surface geology, regolith/soil type, and/or nearby outcropping bedrock. For instance, the extensive black clay soils of the Barkly Tableland define a >500 km long northwest–southeast-trending unradiogenic anomaly (87Sr/86Sr ). Where sedimentary carbonate or mafic/ultramafic igneous rocks dominate, low to moderate 87Sr/86Sr values are generally recorded (medians of 0.7387 and 0.7422, respectively). Conversely, In proximity to the outcropping Proterozoic metamorphic basement of the Tennant, McArthur, Murphy, and Mount Isa geological regions, radiogenic 87Sr/86Sr values (>0.7655) are observed. A potential correlation between mineralization and elevated 87Sr/86Sr values in these regions needs to be investigated in greater detail. Our results to date indicate that incorporating soil/regolith Sr isotopes in regional, exploratory geoscience investigations can help identify basement rock types under (shallow) cover, constrain surface processes (e.g. weathering and dispersion), and, potentially, recognize components of mineral systems. Furthermore, the resulting Sr isoscape and future models derived therefrom can also be utilized in forensic, archaeological, palaeontological, and ecological studies that aim to investigate, for example, past and modern animal (including humans) dietary habits and migrations. The new spatial Sr isotope dataset for the northern Australia region is publicly available (de Caritat et al., 2022a; https://doi.org/10.26186/147473).

The timing of the first arrival of Homo sapiens in East Asia from Africa and the degree to which they interbred with or replaced local archaic populations is controversial. Previous discoveries from Tam Pà Ling cave (Laos) identified H. sapiens in Southeast Asia by 46 kyr. We report on a new frontal bone (TPL 6) and slightly older tibial fragment (TPL 7) discovered in the deepest layers of TPL. Bayesian modeling of luminescence dating of sediments and U-series and combined U-series-ESR dating of mammalian teeth reveals a depositional sequence spanning ~ 86 kyr. TPL 6 confirms the presence of H. sapiens by 70 ± 3 kyr, and TPL 7 extends this range to 77 ± 9 kyr, supporting an early dispersal of H. sapiens into Southeast Asia. Geometric morphometric analyses of TPL 6 suggest descent from a gracile immigrant population rather than evolution from or admixture with local archaic populations.

Background: Editorial board members of academic journals are often considered gatekeepers of knowledge and role models for the community. Editorial boards should have sufficiently diverse backgrounds to facilitate the publication of manuscripts with a wide range of research paradigms, methods, and cultural perspectives.Objectives: This study critically evaluates changes in the representation of binary gender and geographic diversity over time for the editorial boards of Chemical Geology and Geochimica et Cosmochimica Acta. These are the two flagship geochemistry journals from the European Association of Geochemistry and the Geochemical Society, respectively.Methods: Composition of editorial boards was taken from the first issue of the year in question and editorial board members were coded for country of affiliation and binary gender. Results: Gender parity, limited to men and women, and geographic representation of the editorial boards of Chemical Geology and Geochimica et Cosmochimica Acta, have steadily increased between the late 1980’s and 2021. However, geographic distribution remains largely dominated by affiliations from North America and Western Europe. The Editor-in-Chief or board of editors have a significant impact on the level of diversity of the editorial board. With nearly every newly appointed editor, both geographic and gender diversity may evolve. However, the persisting substantial underrepresentation of editorial board members from outside of North America and Europe is of concern and needs to be the focus of active recruitment and ongoing monitoring. This approach will ensure that traditionally low levels of geographic diversity are mitigated and representation of our global communities is improved and maintained in the future. Conclusions: Improving diversity and inclusion among editorial boards as well as strengthening journal and disciplinary reputations will reinforce one another. Instituting a rotating editorship with an emphasis on embedding broader geographic networks and more equitable international recruitment could ensure sustained and improved geographic, gender, and wider representation, which, as a consequence, may lift scientific originality and the quality of published research.

In light of climate change, wildfires are concurrently becoming more frequent and devastating worldwide. Though we have a good understanding of fire frequency changes in the past using charcoal analysis, records of the characteristics of these fires, such as fire severity, are lacking. This limits our ability to model how fire severity responds to climate change. Boron isotopes in clay minerals show promise as a novel fire severity proxy, where increased 𝛿B is correlated with higher fire severity. Through reacting boron leached from experimentally combusted plants with clays, we determine that the observed correlation with fire severity is likely caused by input of isotopically heavier boron from combusted leaves. In contrast, combusted barks lower the 𝛿B of clays upon reaction. Despite the different results, in both experiments with barks and leaves, similar boron isotope fractionation is observed during boron adsorption onto clays, where the lighter B is preferentially adsorbed. Therefore, the different results are likely caused by the different boron isotope composition of leaves and barks, where leaves have a much higher 𝛿B (~30 ‰) than bark (~9 ‰). Combustion temperature can also affect the 𝛿B of clays: changes to the 𝛿B of clays were observed only when reacting with bark combusted at >300 °C, or with leaves combusted at >550 °C. This could be because more boron can be leached into solution from materials combusted at higher temperatures, which in turn results in greater adsorption onto clays during reactions. Clays have higher 𝛿B in soils affected by high severity fires that consume tree crowns, because these fires combust more leaves that then deposit their isotopically heavier boron content into the soil. This relationship could help complete our fire record and improve our ability to predict future fire characteristics.

Quantifying the timescale of sedimentary processes in river basins, such as erosion, transport and deposition, and their relationships with geomorphic parameters is important in the context of ongoing climate change. In this study, we combine uranium activity ratios (234U/238U) for fine-grained (

Dust plays important roles in the environment, and there has been much interest in the formation, provenance, and age of the world's dust deposits. Ongoing debates are concerned with the importance of glacial grinding versus eolian abrasion and fluvial transport in the formation of silt-sized particles. Short-lived uranium-series isotopes afford new insights because they can be used both for provenance fingerprinting and for constraining the integrated age of chemical and physical weathering and subsequent transport and storage of sediments. Here we present trace element and Sr, Nd, and U-series isotope analyses from a number of Australian dusts and suspended river sediments remobilized during floods a year later. The inferred ages of the Australian dust appear to be linked to aridification and the loss of inland megalakes ∼30–120 k.y. ago. This provides preliminary evidence that the age of dust may provide a new hydrological indicator in arid environments.

Calcium balance is abnormal in adults with chronic kidney disease (CKD) and is associated with the development of vascular calcification. It is currently not routine to screen for vascular calcification in CKD patients. In this cross-sectional study, we investigate whether the ratio of naturally occurring calcium (Ca) isotopes, 44Ca and 42Ca, in serum could be used as a noninvasive marker of vascular calcification in CKD.We recruited 78 participants from a tertiary hospital renal center: 28 controls, 9 subjects with mild–moderate CKD, 22 undertaking dialysis and 19 who received a kidney transplant. For each participant, systolic blood pressure, ankle brachial index, pulse wave velocity, and estimated glomerular filtration rate were measured, along with serum markers. Calcium concentrations and isotope ratios were measured in urine and serum. While we found no significant association between urine Ca isotope composition (noted δ44/42Ca) between the different groups, δ44/42Ca values in serum were significantly different between healthy controls, subjects with mild–moderate CKD and those undertaking dialysis (P

Explanations for the Upper Pleistocene extinction of megafauna from Sahul (Australia and New Guinea) remain unresolved. Extinction hypotheses have advanced climate or human-driven scenarios, in spite of over three quarters of Sahul lacking reliable biogeographic or chronologic data. Here we present new megafauna from north-eastern Australia that suffered extinction sometime after 40,100 (±1700) years ago. Megafauna fossils preserved alongside leaves, seeds, pollen and insects, indicate a sclerophyllous forest with heathy understorey that was home to aquatic and terrestrial carnivorous reptiles and megaherbivores, including the world’s largest kangaroo. Megafauna species diversity is greater compared to southern sites of similar age, which is contrary to expectations if extinctions followed proposed migration routes for people across Sahul. Our results do not support rapid or synchronous human-mediated continental-wide extinction, or the proposed timing of peak extinction events. Instead, megafauna extinctions coincide with regionally staggered spatio-temporal deterioration in hydroclimate coupled with sustained environmental change., The causes of the Upper Pleistocene megafauna extinction in Australia and New Guinea are debated, but fossil data are lacking for much of this region. Here, Hocknull and colleagues report a new, diverse megafauna assemblage from north-eastern Australia that persisted until ~40,000 years ago.

The values and distribution patterns of the strontium (Sr) isotope ratio 87Sr/86Sr in Earth surface materials are of use in the geological, environmental, and social sciences. Ultimately, the 87Sr/86Sr ratios of soils and everything that lives in and on them are inherited from the rocks that are the parent materials of the soil's components. In Australia, there are few large-scale surveys of 87Sr/86Sr available, and here we report on a new, low-density dataset using 112 catchment outlet (floodplain) sediment samples covering 529 000 km2 of inland southeastern Australia (South Australia, New South Wales, Victoria). The coarse (<2 mm) fraction of bottom sediment samples (depth ∼ 0.6–0.8 m) from the National Geochemical Survey of Australia were milled and fully digested before Sr separation by chromatography and 87Sr/86Sr determination by multicollector-inductively coupled plasma mass spectrometry. The results show a wide range of 87Sr/86Sr values from a minimum of 0.7089 to a maximum of 0.7511 (range 0.0422). The median 87Sr/86Sr (± median absolute deviation) is 0.7199 (± 0.0071), and the mean (± standard deviation) is 0.7220 (± 0.0106). The spatial patterns of the Sr isoscape observed are described and attributed to various geological sources and processes. Of note are the elevated (radiogenic) values (≥∼ 0.7270; top quartile) contributed by (1) the Palaeozoic sedimentary country rock and (mostly felsic) igneous intrusions of the Lachlan geological region to the east of the study area; (2) the Palaeoproterozoic metamorphic rocks of the central Broken Hill region; both these sources contribute radiogenic material mainly by fluvial processes; and (3) the Proterozoic to Palaeozoic rocks of the Kanmantoo, Adelaide, Gawler, and Painter geological regions to the west of the area; these sources contribute radiogenic material mainly by aeolian processes. Regions of low 87Sr/86Sr (≤∼ 0.7130; bottom quartile) belong mainly to (1) a few central Murray Basin catchments; (2) some Darling Basin catchments in the northeast; and (3) a few Eromanga geological region-influenced catchments in the northwest of the study area; these sources contribute unradiogenic material mainly by fluvial processes. The new spatial Sr isotope dataset for the DCD (Darling–Curnamona–Delamerian) region is publicly available (de Caritat et al., 2022; https://dx.doi.org/10.26186/146397)​​​​​​​.

Our study on the exact timing and the potential climatic, environmental, and evolutionary consequences of the Laschamps Geomagnetic Excursion has generated the hypothesis that geomagnetism represents an unrecognized driver in environmental and evolutionary change. It is important for this hypothesis to be tested with new data, and encouragingly, none of the studies presented by Picin et al . undermine our model.

Diversity, at every step along the scientific path, drives innovative research. Scientific societies, like the Geochemical Society (GS) and the European Association of Geochemistry (EAG), have a significant influence on which innovators are celebrated. Such choices have the consequence of shaping the future of research, and so are responsible for the evolution of our discipline and its relationship to the global community. These professional bodies are uniquely positioned to define and promote the success of all scientists, including those from under-represented groups, through proactive advocacy, inclusive mentorship, awards, and leadership. At present, the only data available to examine the distribution of under-represented groups between memberships, awardees leadership are those of gender. To assess gender diversity in the geochemistry and cosmochemistry community, we thus introspectively review available records of GS and EAG membership through Goldschmidt Conference attendees, awardees, leadership, and editorial boards. This work identifies areas for growth and begins a dialogue about how the society and its members can work together to better reflect and progress our community. Our examination of the record spanning the last decade demonstrates that leadership positions, awards, and honors have continued to be disproportionately given to white men, to the exclusion of women. The GS and EAG have recently taken positive steps towards becoming more inclusive; however, much more work is needed. In order for both communities to become diverse, equitable and inclusive, where all scientists flourish, we offer suggestions for swift steps that the GS and EAG and their members can pursue. The suggested structural improvements will require ongoing analysis and reforms, which must be shared by all of us, to create a sustainable legacy that we can be proud of.

Emerging applications in isotope geochemistry using stable metal isotope systems, including those in archaeological, environmental and medical sciences, along with commercial/industrial applications such as environmental source tracing and ore exploration, require high sample throughput that conventional element purification techniques—i.e. gravity flow ion exchange chromatography (IEC)—cannot match. Here, a simple and robust method for element purification from biological and geological samples has been developed, SpinChem™, wherein element purification via IEC is greatly facilitated through centrifugation. In brief, this involves adapting chromatographic columns for encapsulation within large (50 mL) centrifuge tubes, and subsequent element purification at enhanced flow rates (1.2–1.5 mL min−1) generated by centrifugal force. As proof of concept, Zn IEC purification from biological and geological materials has been detailed, demonstrating the utility of this method across the sample spectrum, and validating high yields (97 ± 4%), high separation efficiency and low contamination levels (blanks ≤1 ng). SpinChem™ IEC in the centrifuge proceeds at rates up to an order of magnitude faster than in gravity flow protocols, with 8–10 samples processed through IEC in under 2 hours (vs. 4–10 hours in gravity flow), while maintaining high subsequent MC-ICP-MS analytical precision, with average errors of 0.06‰ (2σ) or better for δ66Zn. Benchmarking this technique using an element very sensitive to endogenous and exogenous contamination (e.g. inefficient separation and external contaminants, respectively)—Zn—exemplifies the utility and high performance of this technique, and its ready adaptation to other isotope systems of interest, including Ca, Fe, Cu, Sr/Nd, Mo and Sn.

Understanding the evolution of soil systems on geological time scales has become fundamentally important to predict future landscape development in light of rapid global warming and intensifying anthropogenic impact. Here, we use an innovative uranium isotope-based technique combined with organic carbon isotopes and elemental ratios of sediments from Lake Ohrid (North Macedonia/Albania) to reconstruct soil system evolution in the lake's catchment during the last ~16,000 cal yr BP. Uranium isotopes are used to estimated the paleo-sediment residence time, defined as the time elapsed between formation of silt and clay sized detrital matter and final deposition. The chronology is based on new cryptotephra layers identified in the sediment sequence. The isotope and elemental data are compared to sedimentary properties and pollen from the same sample material to provide a better understanding of past catchment erosion and landscape evolution in the light of climate forcing, vegetation development, and anthropogenic land use. During the Late Glacial and the Early Holocene, when wide parts of the catchment were covered by open vegetation, wetter climates promoted the mobilisation of detrital matter with a short paleo-sediment residence time. This is explained by erosion of deeper parts of the weathering horizon from thin soils. Detrital matter with a longer paleo-sediment residence time, illustrating shallow erosion of thicker soils is deposited in drier climates. The coupling between climatic variations and soil erosion terminates at the Early to Mid-Holocene transition as evidenced by a pronounced shift in uranium isotope ratios indicating that catchment erosion is dominated by shallow erosion of thick soils only. This shift suggests a threshold is crossed in hillslope erosion, possibly as a result of a major change in vegetation cover preventing deep erosion of thin soils at higher elevation. The threshold in catchment erosion is not mirrored by soil development over time, which gradually increases in response to Late Glacial to Holocene warming until human land use during the Late Holocene promotes reduced soil development and soil degradation. Overall, we observe that soil system evolution is progressively controlled by climatic, vegetation, and eventually by human land use over the last ~16,000 years.

Lithium (Li) isotopes in marine carbonates have considerable potential as a proxy to constrain past changes in silicate weathering fluxes and improve our understanding of Earth's climate. To date the majority of Li isotope studies on marine carbonates have focussed on calcium carbonates. The determination of the Li isotope fractionation between dolomite and a dolomitizing fluid would allow us to extend investigations to deep times (i.e. Precambrian) when dolostones were the most abundant marine carbonate archives. Dolostones often contain a significant proportion of detrital silicate material, which dominates the Li budget; thus, pretreatment needs to be designed so that only the isotope composition of the carbonate-associated Li is measured. This study aims to serve two main goals: (1) to determine the Li isotope fractionation between Ca–Mg carbonates and solution, and (2) to develop a method for leaching the carbonate-associated Li out of dolostone while not affecting the Li contained within the detrital portion of the rock. We synthesized Ca–Mg carbonates at high temperatures (150 to 220 ∘C) and measured the Li isotope composition (δ7Li) of the precipitated solids and their respective reactive solutions. The relationship of the Li isotope fractionation factor with temperature was obtained: 103ln⁡αprec-sol=-(2.56±0.27)106(1)/T2+(5.8±1.3) Competitive nucleation and growth between dolomite and magnesite were observed during the experiments; however, there was no notable effect of their relative proportion on the apparent Li isotope fractionation. We found that Li isotope fractionation between the precipitated solid and solution is higher for Ca–Mg carbonates than for Ca carbonates. If the temperature of a precipitating solution is known or can be estimated independently, the above equation could be used in conjunction with the Li isotope composition of dolostones to derive the composition of the solution and hence make inferences about the past Li cycle. In addition, we also conducted leaching experiments on a Neoproterozoic dolostone and a Holocene coral. Results show that leaching with 0.05 M hydrochloric acid (HCl) or 0.5 % acetic acid (HAc) at room temperature for 60 min releases Li from the carbonate fraction without a significant contribution of Li from the siliciclastic detrital component. These experimental and analytical developments provide a basis for the use of Li isotopes in dolostones as a palaeo-environmental proxy, which will contribute to further advance our understanding of the evolution of Earth's surface environments.

Tributary creeks of the southern Sierra Nevada have pronounced knickpoints that separate the landscape into an alternating sequence of gently sloped treads and steeply sloped risers. These knickpoints and the surrounding “stepped topography” suggest that the landscape is still responding to Pleistocene changes in base level on main-stem rivers. We tested this hypothesis using cosmogenic nuclides and uranium isotopes measured in stream sediment from widely distributed locations. Catchment-scale erosion rates from the cosmogenic nuclides suggest that the treads are relict surfaces that have adjusted to a previous base level. Nevertheless, erosion rates of relict interfluves are similar to canyon incision rates, implying that relief is unchanging in the lower Kings and San Joaquin Rivers. In addition, our results suggest that much of the southern Sierra Nevada is in a state of arrested development: the landscape is not fully adjusted to—and moreover is not responding to— changes in base-level lowering in the canyons. We propose that this can be explained by a paucity of coarse sediment supply, which fails to provide sufficient tools for bedrock channel incision at knickpoints. We hypothesize that the lack of coarse sediment in channels is driven by intense weathering of the local granitic bedrock, which reduces the size of sediment supplied from hillslopes to the channels. Our analysis highlights a feedback in which sediment size reduction due to weathering on hillslopes and transport in channels is both a key response to and control of bedrock channel incision and landscape adjustment to base-level change.

The development of weathering profiles shapes Earth’s surface and regulates its climate via chemical weathering. Hence, it is essential to be able to determine the age of weathering profiles and quantify how fast they form. Uranium-series isotopes allow for such quantification. However, isotope compositions are generally measured in bulk regolith, which represents a complex mixture of mineral and organic phases of different origins that can impact the reliability of the information derived from U-series isotopes. Thus, in this study, we assess whether sequential extraction and mineral separation could provide more reliable estimates of weathering ages and rates. We focus on a granitic profile developed under temperate climate in southeastern Australia, a tectonically quiescent environment. Regolith production rates have been independently estimated in the region using cosmogenic isotopes. As expected, the mineralogy and geochemistry of the bulk regolith show that biotite and feldspar are the main phases lost during weathering, progressively replaced by clay minerals. There is no evidence for significant input of element from external sources, such as via aerosol deposition. While sequential extraction does not seem to affect major mineral phases and element concentrations, it is suspected of producing artificial radioactive disequilibrium. Biotite separates show very large accumulation of U and Th, which increases with decreasing depth. Regolith production rates and mineral dissolution rates calculated with weathering rates estimated using the bulk saprolite and quartz separate compositions yield values comparable to independent estimates. Conversely, weathering ages derived from the compositions of saprolite leached experimentally or biotite separates underestimate regolith production rates and mineral dissolution rates. Thus, sequential extraction or biotite separation are not recommended methods to derive reliable rates of regolith production and mineral dissolution. Despite the potential complexity of the composition of bulk regolith, the use of regolith without any pre-treatment seems to yield satisfying estimates of regolith production and mineral dissolution rates. The composition of quartz separates yields rates similar to those derived from bulk compositions. This provides an alternative method, potentially allowing reliable results to be obtained from a single mineral phase rather than a complex mixture of weathering products.

To quantify chemical weathering processes, it is essential to develop and utilize new geochemical tools that can provide information about chemical weathering in the field. U-series isotopes have emerged as a useful chronometer to directly constrain the rates and duration of chemical weathering. However, the conventional solution-based MC-ICPMS method involves a long and expensive sample processing procedure that restricts the numbers of measurements of samples by U-series analysis that can be completed. Here, we report in situ measurements of U-series disequilibria obtained with laser ablation (LA)-MC-ICPMS on weathering rinds collected from the tropical island of Basse-Terre in the archipelago of French Guadeloupe. We characterized two weathering rinds for U-series isotope compositions and elemental distributions with LA-MC-ICPMS and LA-Q-ICPMS. The in situ measurements of U-series disequilibria were consistent with the previous bulk measurements obtained by conventional solution MC-ICPMS despite the larger analytical uncertainties. The LA technique allowed a greater number of measurements that accelerated sample throughput and improved spatial resolution of measurement. The rind formation age, weathering rates, and U-series mobility parameters modeled in this study are comparable to the results from previous studies conducted on the same clasts, and also reveal new insights on rind formation such as the impact of micro-fractures on weathering history and U-series ratios. The improved spatial resolution available with LA Q-ICPMS helps distinguish between linear and power law rind thickness-age relationships that were unresolvable using conventional solution-based MC-ICPMS. In situ measurements with LA-Q-ICPMS in these weathering rinds also elucidates the sequences of mineral reactions during chemical weathering. The LA-Q-ICPMS maps of major and trace elements and elemental ratios reveal details about the rind formation processes at the weathering interfaces of clasts such as dissolution of primary phases, formation of new phases, development of porosity, and mobility behavior of U. This study demonstrates a new analytical method for determining weathering rates in rinds rapidly and accurately that can be used in a large number of rinds, providing key information at the clast scale.

Flores represents a unique insular environment with an extensive record of Pleistocene fossil remains and stone artefacts. In the So'a Basin of central Flores these include endemic Stegodon, Komodo dragons, giant tortoises, rats, birds and hominins, and lithic artefacts that can be traced back to at least one million years ago (1 Ma). This comprehensive review presents important new data regarding the dating and faunal sequence of the So'a Basin, including the site of Mata Menge where Homo floresiensis-like fossils dating to approximately 0.7 Ma were discovered in 2014. By chemical fingerprinting key silicic tephra originating from local and distal eruptive sources we have now established basin-wide tephrostratigraphic correlations, and, together with new numerical ages, present an update of the chronostratigraphy of the So'a Basin, with major implications for the faunal sequence. These results show that a giant tortoise and the diminutive proboscidean Stegodon sondaari last occurred at the site of Tangi Talo ∼1.3 Ma, and not 0.9 Ma as previously thought. We also present new data suggesting that the disappearance of giant tortoise and S. sondaari from the sedimentary record occurred before, and/or was coincident with, the earliest hominin arrival, as evidenced by the first records of lithic artefacts occurring directly below the 1 Ma Wolo Sege Tephra. Artefacts become common in the younger layers, associated with a distinct fauna characterized by the medium-sized Stegodon florensis and giant rat Hooijeromys nusatenggara. Furthermore, we describe a newly discovered terrace fill, which extends the faunal record of Stegodon in the So'a Basin to the Late Pleistocene. Our evidence also suggests that the paleoenvironment of the So'a Basin became drier around the time of the observed faunal transition and arrival of hominins on the island, which could be related to an astronomically-forced climate response at the onset of the Mid-Pleistocene Transition (MPT; ∼1.25 Ma) leading to increased aridity and monsoonal intensity. publishedVersion

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Soil Organic Carbon (SOC) represents with up to 80% the largest part of the terrestrial’s carbon pool. However, it is still highly debated if soil-carbon is a net atmospheric carbon source or sink. This is mainly due to a paucity of information on the SOC’s fate during soil erosion, which controls the interplay between SOC oxidation during soil storage, transportation, and final storage in a sedimentary sink. The southern hemisphere landmasses have the potential to play a dominant role in the SOC - atmosphere carbon cycle, since wetter (dryer) climates can cause the expansion (contraction) of terrestrial biomass in vast continental areas, such as for example in temperate to semi-arid SE Australia.We herein investigate the interplay between catchment erosion (quantified by means of uranium isotopes), vegetation density (pollen), the wetland’s response (diatoms), and catchment-wide carbon and nitrogen cycling (carbon and nitrogen isotopes) on glacial/interglacial time scales in SE Australia. The analyses are applied to the sediments of Lake Couridjah, which is part of the Thirlmere Lake system located approximately 100 km SE of Sydney. A previous study has shown that Lake Couridjah and its catchment vegetation are highly sensitive to local and regional climate change. Radiocarbon and luminescence dating revealed that recovered lake sediments cover the time interval between ~140 ka and 100 ka, and between ~17.6 cal yr BP and present day. Lake Couridjah is thus one of the very few sedimentary archives providing a continuous archive for the previous interglacial complex in SE Australia, and thus offers an outstanding opportunity to study SOC cycling in a small catchment across different interglacial boundary conditions. The sedimentary analyses are supported by uranium, carbon, and nitrogen isotope analyses of a soil pit from the vicinity of the lake.Statistical analyses revealed robust phase-relationships between catchment erosion, vegetation density, and carbon and nitrogen cycling during both glacial-interglacial complexes. The data implies that the density of the catchment’s sclerophyll woodland and mid- to understory vegetation - and not the amount of rainfall - has major control on catchment erosion, and, thus, on SOC storage in the catchment. Overall wetter and warmer peak interglacial conditions promote the expansion of dense sclerophyll vegetation, reducing catchment erosion while simultaneously increasing SOC storage as well as lake productivity and lake carbon-storage. The later post-Eemian phase of the preceding interglacial reveals overall cooler climates and a more open sclerophyll vegetation, resulting in faster catchment-wide erosion and reduced SOC and lake-C storage, conditions that are amplified in glacial periods (post-LGM, penultimate glacial period).

Reversing the field Do terrestrial geomagnetic field reversals have an effect on Earth's climate? Cooper et al. created a precisely dated radiocarbon record around the time of the Laschamps geomagnetic reversal about 41,000 years ago from the rings of New Zealand swamp kauri trees. This record reveals a substantial increase in the carbon-14 content of the atmosphere culminating during the period of weakening magnetic field strength preceding the polarity switch. The authors modeled the consequences of this event and concluded that the geomagnetic field minimum caused substantial changes in atmospheric ozone concentration that drove synchronous global climate and environmental shifts. Science , this issue p. 811

For over half a century, uranium (U) and thorium (Th) decay series isotopes have been used as a chronometer and tracer of a range of geological and biological processes. In volcanic rocks, they can be used to help determine how magma is produced in a range of environments, how fast it is transported, and minerals that are precipitated in the process. They have also been used to date volcanic eruptions. In soils, U-series isotopes can estimate how fast parent material is weathered and converted into regolith. In fluvial sediments, they allow a determination of how long sediments have resided in a catchment. Uranium-series isotopes have also been applied to the study of groundwater, where they inform on the dissolution rate of the aquifer rock and the groundwater flow rate. In marine sediments, U- and Th-series isotopes have played a key role in improving our understanding of marine processes. For instance, they can quantify particular organic matter flux (with implications for the carbon cycle), and inform on particular transport and palaeo-productivity. Finally, U-series dating of carbonates such as corals has been instrumental in our understanding of past sea levels. The use of these isotopes in the dating of phosphates such as fossil bones and teeth has allowed us to directly date human fossils, with major implications for human evolution.

Uranium (U) isotopes can be used to estimate the comminution age of sediments, i.e. the time elapsed from sediment production on continents, via weathering and physical erosion, to deposition in the sedimentary record. The calculation of this comminution age is based on measured (234U/238U) activity ratios in river sediments, and inferred time-dependent recoil effect, which leads to the preferential release of 234U from mineral lattices during erosion processes. In this study, we report on a large-scale (234U/238U) investigation of modern river sediments worldwide, with the aim to determine the extent to which parameters such as grain size, lithology, weathering, climate and geomorphology may influence the distribution of U isotopes in fine-grained sediments. Our extensive dataset (N=64) includes U isotopic measurements for many of the world’s largest rivers, but also rivers draining particular climatic and geological settings. Our results indicate that sediments collected from river basins draining mostly igneous, metamorphic or volcanic rocks often display (234U/238U) ratios >1, with clay-size fractions (

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