Klaus M. Wilcken

To quantify the reproducibility and precision of cosmogenic ¹⁰Be and ²⁶Al analyses, we analysed a suite of liquid and quartz reference materials, together with duplicate preparations of unknown research samples. Comparison among these materials allows us to constrain uncertainties associated with AMS measurement, chemical extraction, and quartz purification, and to assess whether additional variability is introduced at successive stages of the analytical process. Samples were prepared in three chemistry laboratories at the Australian Nuclear Science and Technology Organisation (ANSTO), the University of Wollongong (UOW), and Imperial College London, and subsequently analysed by accelerator mass spectrometry (AMS) using the 6 MV SIRIUS accelerator at ANSTO. All three laboratories showed intra-laboratory variability below the routine 2% analytical uncertainty, while measured values were consistent with the nominal values of the reference materials. These results indicate that both methodological reproducibility and inter-laboratory variability are also within the analytical uncertainty, and provide no evidence for additional uncertainty associated with processing quartz relative to liquid reference materials. The implications for cosmogenic-nuclide research are that: (1) the reproducibility and precision of cosmogenic ¹⁰Be and ²⁶Al analyses are typically 2–3% when sufficient counting statistics are achieved; (2) at lower isotope concentrations, counting statistics and/or background corrections may limit the achievable measurement uncertainty, although the resulting variability remains consistent with the reported analytical precision; and (3) precision of approximately 1% is achievable for high-concentration liquid reference materials, as demonstrated by Be-KN-5-4 and Al-KN-4-3, but has not yet been demonstrated for quartz samples.

To quantify the reproducibility and precision of cosmogenic ¹⁰Be and ²⁶Al analyses, we analysed a suite of liquid and quartz reference materials, together with duplicate preparations of unknown research samples. Comparison among these materials allows us to constrain uncertainties associated with AMS measurement, chemical extraction, and quartz purification, and to assess whether additional variability is introduced at successive stages of the analytical process. Samples were prepared in three chemistry laboratories at the Australian Nuclear Science and Technology Organisation (ANSTO), the University of Wollongong (UOW), and Imperial College London, and subsequently analysed by accelerator mass spectrometry (AMS) using the 6 MV SIRIUS accelerator at ANSTO. All three laboratories showed intra-laboratory variability below the routine 2% analytical uncertainty, while measured values were consistent with the nominal values of the reference materials. These results indicate that both methodological reproducibility and inter-laboratory variability are also within the analytical uncertainty, and provide no evidence for additional uncertainty associated with processing quartz relative to liquid reference materials. The implications for cosmogenic-nuclide research are that: (1) the reproducibility and precision of cosmogenic ¹⁰Be and ²⁶Al analyses are typically 2–3% when sufficient counting statistics are achieved; (2) at lower isotope concentrations, counting statistics and/or background corrections may limit the achievable measurement uncertainty, although the resulting variability remains consistent with the reported analytical precision; and (3) precision of approximately 1% is achievable for high-concentration liquid reference materials, as demonstrated by Be-KN-5-4 and Al-KN-4-3, but has not yet been demonstrated for quartz samples.

Lake Woods, Jurrkulu, is northern Australia's largest freshwater lake filled today in strong Indo–Australian summer monsoons (IASM) to maximum depths of ~5 m. On the western margins of the lake, two large arcuate ridges occur 20 to 40 m above the lake floor and inset within these are other mid‐elevation lake deposits, such as depositional ridges, which suggest past filling events much higher than the modern maximum. We have undertaken the analysis of 20 samples for single‐grain optically stimulated luminescence (OSL) from shoreline and lake‐floor deposits and supplemented this chronology with an analysis of the basin hypsometry, basin‐wide erosion rates and rare earth elements to ascertain the dominant source of the large source‐bordering ridges. The outer and inner arcuate ridges represent both aeolian accumulation and inferred lake‐level highstands due to the presence of fine gravel facies and gastropods contained within them. We document two lake highstands at 195 ± 16 ka and at 98 ± 7 ka (20 and 15 m above the lake floor, respectively; the lake floor is 197 m Australian Height Datum, AHD). We also present a third but undated filling event 18.5 m above the lake floor (215.5 m AHD) but that is bracketed by two OSL ages of 91 ± 5 and 52 ± 3 ka, with a Bayesian modelled boundary age for lake filling of 95.9 to 53.8 ka (95% credible interval; C.I.). We find no evidence of the previously reported late Marine Isotope Stage [MIS] 3 highstand deposits and the prevalence of gully‐filled structureless sediments, dated to the mid to late Holocene, many of which contain archaeological artefacts that do not allow for the quantification of any accurate Holocene lake‐filling episodes. The lake floor is characterised by deeply cracking silts and clays, with single‐grain OSL results supporting significant post‐depositional mixing (maximum ages are <143 ka). Denudation rate data from detrital stream sediment samples indicate some of the lowest rates of denudation in northern Australia, of between 2.05 ± 0.51 and 0.83 ± 0.23 m/Myr, with the latter rate stemming from the dominant catchment area in the Barkly Tablelands. Sediment provenance data indicate that the slowly eroding Barkly Tablelands is the dominant source for the clays and silts in the lake basin. Despite being the largest lake in northern Australia, the slow rates of catchment‐wide erosion coupled with the intermittent filling have only produced a discontinuous record of the IASM, but one that shows exceptional episodic filling in MIS 5 to 4.

To quantify the reproducibility and precision of cosmogenic ¹⁰Be and ²⁶Al analyses, we analysed a suite of liquid and quartz reference materials, together with duplicate preparations of unknown research samples. Comparison among these materials allows us to constrain uncertainties associated with AMS measurement, chemical extraction, and quartz purification, and to assess whether additional variability is introduced at successive stages of the analytical process. Samples were prepared in three chemistry laboratories at the Australian Nuclear Science and Technology Organisation (ANSTO), the University of Wollongong (UOW), and Imperial College London, and subsequently analysed by accelerator mass spectrometry (AMS) using the 6 MV SIRIUS accelerator at ANSTO. All three laboratories showed intra-laboratory variability below the routine 2% analytical uncertainty, while measured values were consistent with the nominal values of the reference materials. These results indicate that both methodological reproducibility and inter-laboratory variability are also within the analytical uncertainty, and provide no evidence for additional uncertainty associated with processing quartz relative to liquid reference materials. The implications for cosmogenic-nuclide research are that: (1) the reproducibility and precision of cosmogenic ¹⁰Be and ²⁶Al analyses are typically 2–3% when sufficient counting statistics are achieved; (2) at lower isotope concentrations, counting statistics and/or background corrections may limit the achievable measurement uncertainty, although the resulting variability remains consistent with the reported analytical precision; and (3) precision of approximately 1% is achievable for high-concentration liquid reference materials, as demonstrated by Be-KN-5-4 and Al-KN-4-3, but has not yet been demonstrated for quartz samples.

To quantify the reproducibility and precision of cosmogenic ¹⁰Be and ²⁶Al analyses, we analysed a suite of liquid and quartz reference materials, together with duplicate preparations of unknown research samples. Comparison among these materials allows us to constrain uncertainties associated with AMS measurement, chemical extraction, and quartz purification, and to assess whether additional variability is introduced at successive stages of the analytical process. Samples were prepared in three chemistry laboratories at the Australian Nuclear Science and Technology Organisation (ANSTO), the University of Wollongong (UOW), and Imperial College London, and subsequently analysed by accelerator mass spectrometry (AMS) using the 6 MV SIRIUS accelerator at ANSTO. All three laboratories showed intra-laboratory variability below the routine 2% analytical uncertainty, while measured values were consistent with the nominal values of the reference materials. These results indicate that both methodological reproducibility and inter-laboratory variability are also within the analytical uncertainty, and provide no evidence for additional uncertainty associated with processing quartz relative to liquid reference materials. The implications for cosmogenic-nuclide research are that: (1) the reproducibility and precision of cosmogenic ¹⁰Be and ²⁶Al analyses are typically 2–3% when sufficient counting statistics are achieved; (2) at lower isotope concentrations, counting statistics and/or background corrections may limit the achievable measurement uncertainty, although the resulting variability remains consistent with the reported analytical precision; and (3) precision of approximately 1% is achievable for high-concentration liquid reference materials, as demonstrated by Be-KN-5-4 and Al-KN-4-3, but has not yet been demonstrated for quartz samples.

To quantify the reproducibility and precision of cosmogenic 10Be and 26Al analyses, we analysed a suite of liquid and quartz reference materials, together with duplicate preparations of unknown research samples. Comparison among these materials allows us to constrain uncertainties associated with AMS measurement, chemical extraction, and quartz purification, and to assess whether additional variability is introduced at successive stages of the analytical process. Samples were prepared in three chemistry laboratories at the Australian Nuclear Science and Technology Organisation (ANSTO), the University of Wollongong (UOW), and Imperial College London, and subsequently analysed by accelerator mass spectrometry (AMS) using the 6 MV SIRIUS accelerator at ANSTO. All three laboratories showed intra-laboratory variability below the routine 2% analytical uncertainty, while measured values were consistent with the nominal values of the reference materials. These results indicate that both methodological reproducibility and inter-laboratory variability are also within the analytical uncertainty, and provide no evidence for additional uncertainty associated with processing quartz relative to liquid reference materials. The implications for cosmogenic-nuclide research are that: (1) the reproducibility and precision of cosmogenic 10Be and 26Al analyses are typically 2–3% when sufficient counting statistics are achieved; (2) at lower isotope concentrations, counting statistics and/or background corrections may limit the achievable measurement uncertainty, although the resulting variability remains consistent with the reported analytical precision; and (3) precision of approximately 1% is achievable for high-concentration liquid reference materials, as demonstrated by Be-KN-5-4 and Al-KN-4-3, but has not yet been demonstrated for quartz samples.

The Carrington event of 1859 CE is considered one of the largest geomagnetic storms of the observational era and often used as a benchmark for a worst-case scenario. Yet, there exists no robust evidence of an associated solar energetic particle (SEP) event of a significant magnitude, based on measurements of cosmogenic radionuclides 10Be and 14C from ice cores and tree rings, respectively. In this study, we present two 36Cl records from Greenland with 2- and 4-year resolution from the EGRIP and NGRIP ice core sites, together with semi-annual 10Be data from EGRIP, as well as annual 10Be and 36Cl concentrations from the Dome Summit Site, Law Dome, East Antarctica. We observe no significant 36Cl concentration increase around 1859 CE in the three records. This allows us to rule out an extreme SEP event hitting Earth associated with the Carrington event in terms of fluence above 30 MeV. Based on these ice core 36Cl measurements, we can suggest two scenarios: (i) a soft SEP event with a maximum fluence above 30 MeV up to three times larger than any Space Age event or (ii) the possibility that there was no Earth-bound SEP event. This article is part of the Theo Murphy meeting issue ‘Radiocarbon and cosmic radiation events’.

The Cadí Massif (42°17′09″ N, 1°38′11″ E; 2649 m a.s.l.) in the southeastern Pyrenees preserves clear evidence of Late Pleistocene glaciation, although previous research has focused almost exclusively on its northern slope. By contrast, the southern slope has remained largely unexplored. In this study, we present the first glacial geochronology for this sector by combining ³⁶ Cl terrestrial cosmogenic nuclide (TCN) surface‐exposure dating with numerical paleoclimate modeling. We analyzed 18 boulder samples collected from moraines in two major cirques to constrain the timing of glacier fluctuations. Although some exposure ages were interpreted as reflecting post‐depositional disturbance or possible nuclide inheritance, the resulting chronology indicates that the upper plateaus and southern cirques remained glaciated during the late stages of deglaciation following the Last Glacial Cycle, while subsequent moraine systems document later glacial advances. These include small snowdrift glaciers, up to ca . 4 km in length, that persisted during the Younger Dryas stadial at ca . 12–13 ka, with their mass balance sustained largely by wind‐driven snow redistribution and avalanche‐fed accumulation. Paleoclimate simulations indicate that temperatures were ca . 3°C lower during that phase, while precipitation was comparable to present‐day conditions. This integrated approach demonstrates the sensitivity of southern‐slope glaciers to abrupt climate shifts and provides a more comprehensive view of the spatial variability of glacial responses across the Cadí Massif and the broader Eastern Pyrenees.