Rockfalls and other gravitational mass movements are expected to become more frequent under ongoing global warming in temperate and cold mountainous regions. In contrast, although high numbers of rockfalls are observed in humid tropical mountains, the processes controlling their occurrence remain poorly understood. These warmer regions offer valuable natural laboratories for anticipating the impacts of future warming on slope stability in currently colder environments. We used 10Be surface exposure dating to establish a chronology for seven individual rockfall deposits in the Rwenzori Mountains (Uganda) and assess climatic controls on slope destabilisation. The combination of steep valley flanks and pervasive fracturing in the basement rocks makes the Rwenzori Mountains prone to rockfalls. The 10Be ages range from 13.6 ± 0.9 ka to 1.0 ± 0.1 ka and cluster into three distinct periods: 11–9 ka, 7–5 ka and ~2 ka. These periods align with local temperature fluctuations, suggesting that rockfalls occurred episodically in response to Holocene temperature fluctuations. Early Holocene rockfall activity (~11–9 ka) likely reflects enhanced mechanical weathering and fracture propagation due to glacier retreat and freeze–thaw cycles. In contrast, mid-Holocene (7–5 ka) and late Holocene (~2 ka) rockfall activity coincide with warmer conditions that enabled chemical and biological weathering and enhanced subcritical crack growth, promoting fracture progression and slope destabilization. These results highlight the role of climate – especially temperature – driven chemical and biological weathering in preparing rock slope failures and rockfalls in tropical mountainous landscapes. With continued warming, chemical weathering may increasingly control rockfall activity in temperate and cold climates.

High mountain and polar regions are among the most impacted by present-day climate change, with cryosphere degradation altering geomorphic processes and sediment dynamics. These changes affect ecosystem functioning, hydrogeomorphological hazards, and sediment fluxes from glaciated catchments to the ocean. Understanding sediment transport mechanisms in proglacial rivers is thus crucial for predicting how sediment dynamics in these regions will evolve under continued climate warming.Here, we advance understanding of sediment dynamics in ice sheet-fed proglacial rivers by applying a coupled luminescence–modelling approach to the Qunnguata Kuussua river (Watson river) in south-western Kalaallit Nunaat (south-western Greenland). We build on the work of recent studies which have shown that luminescence signals in modern alluvial sediments can serve as sediment tracers and, when combined with numerical models, provide constraints on transport distances, velocities and storage times (Gray et al., 2018; Guyez et al., 2023).We collected a large dataset (~600 samples) of portable-reader luminescence measurements on bulk sandy sediment samples along the ~30 km-long Watson River during three summer melt seasons (2021–2023). The luminescence signal intensities of different samples are highly variable near the river source (Russell and Leverett glacier termini) and at junctions with tributaries, while the inter-sample signal variability reduces following progressive signal bleaching (i.e. resetting) with increasing downstream transport distance. To interpret and quantify this pattern, we develop a probabilistic luminescence-based sediment transport model that simulates suspended particle transport and luminescence bleaching in a proglacial river. The model successfully reproduces the observed downstream evolution of luminescence signal distributions observed along the Watson River, enabling estimation of sediment transport parameters from combined luminescence and hydrological data.ReferencesGray et al., 2018, Geophysical Research Letters 45.Guyez et al., 2023, Journal of Geophysical Research: Earth Surface 128.

Abstract. The electron spin resonance (ESR) of quartz can be used as a low temperature thermochronometric system, however, to date no field validation of the approach has been made. Here we explore the ESR signals of quartz from six samples from the MIZ1 borehole (Tono, Japan). Previous studies have shown that this low-relief region underwent Quaternary exhumation at rates of <0.2 mm yr-1. We investigate whether quartz ESR signals can resolve such low rates of exhumation, or whether the samples are in thermal equilibrium with ambient borehole temperature. ESR thermochronometry requires that both sample-specific signal saturation and thermal decay are constrained in the laboratory, which makes measurements highly time-consuming. To overcome this, the development of a standardised growth curve (SGC) was explored, which allowed more rapid constraint of the trapped-charge concentrations of each of the samples. Thermal kinetic parameters were determined using an isothermal decay experiment for each individual sample and except for sample MIZ1-08, it was possible to fit all the isothermal decay data together to yield a single set of kinetic parameters that successfully described the dataset. The ESR thermochronometry results show that the MIZ1 samples are in thermal equilibrium for the Al-centre, and that Monte-Carlo inversion of the ESR data yields present-day borehole temperature within 1σ uncertainties for all samples except the lowest temperature sample. In contrast, inversion of the different Ti-centre options (A, B, D) yields temperatures 15–20 °C above contemporary borehole temperature, indicating rock cooling equivalent to a total exhumation of ~1 km over the same period. The cause of this discrepancy is unclear but may relate to sub-linearity of Ti-centre dose response, that led to underestimation of the trapped-charge concentration and hence an overestimation of borehole temperature. Our results validate ESR-thermochronometry of the Al-centre and show that an SGC and common thermal kinetic parameters may be used to expediate sample measurements, however ESR-thermochronometric data from the Ti-centre should be used cautiously until further validation data are available.

Abstract. The storage and release of sediment from glacierised catchments is an important process in mountain landscape evolution, and yet sediment transport pathways and residence times within glaciers remain poorly constrained. We quantified headwall erosion rates and englacial sediment transport and storage times in the Mer de Glace catchment in the Mont Blanc massif, French Alps, during deglaciation through the Holocene (11.7 ka to present). Englacial sediment transport and storage times were constrained using luminescence rock surface burial ages of granitic clasts sampled along the central flow line of the Mer de Glace ablation area. We also used luminescence rock surface exposure dating and terrestrial cosmogenic nuclide (¹⁰Be) measurements to constrain headwall erosion rates for this catchment. These headwall erosion and sediment transport data were compared with simulated erosion, sediment trajectories and transport rates derived from the glacier model iSOSIA. Measured headwall erosion rates were ~0.1–5 mm a⁻¹ and are consistent with other estimates from the Mont Blanc massif. Luminescence rock surface burial ages ranged from ~0.6 to ~6.7 ka and clustered into distinct age populations at ~0.8 ka, ~1.5 ka, ~2.2 ka, and ~6.7 ka. The youngest age population is consistent with continuous englacial transport times predicted by the glacier modelling and observations of present-day glacier surface velocity, whereas the older age clusters indicate prolonged sediment storage within the catchment. Comparison of our results with results from Miage Glacier, Italian Alps, shows that long-term sediment storage with durations exceeding 1 ka is common in steep alpine glacierised catchments, despite high erosion rates and active ice flow. Luminescence burial ages indicate that sediment can be stored during periods of glacier minima, then released during more active phases. Glacierised catchments therefore act as millennial-scale sediment reservoirs, introducing time lags between sediment production and downstream transport, that modulate climatic signals recorded in proglacial stratigraphy during deglaciation.

Scarcity of thermal property data on lower crustal rocks and their variability is a major hindrance in constraining the continental geotherm. As part of the ICDP project DIVE, two boreholes have recently sampled 1.5 km of rocks across a lower crustal metasedimentary and a mafic-ultramafic section of the Ivrea-Verbano Zone. Complete drill core recovery and borehole logging allowed us to generate a new, representative dataset of thermal properties ranging from high-resolution measurements to larger scale profiles. Thermal conductivity under ambient conditions varies considerably within every lithology type: felsic lithologies are more variable and show higher averages ( 3.0 W/(m & sdot;K)) than mafic lithologies ( 2.4 W/(m & sdot;K)). Radiogenic heat production is generally low and varies considerably between mafic-ultramafic lithologies ( 0.05 mu W/m3), felsic lithologies and granulitefacies metasediments ( 0.5 mu W/m3), and amphibolite-facies metasediments ( 1.5 mu W/m3). Overall, metasediments are the largest contributor to the heat budget of the lower crust, where heat production seems to be related to the protolith, not to the metamorphic grade. Measurements of specific heat capacity, density, and thermal diffusivity also reveal primary differences between felsic and mafic lithologies. There is an inverse semi-logarithmic correlation between density and heat production. The variability of all measured thermal properties is significant at all spatial scales, and increases with increasing scales. Thermal conductivity and diffusivity vary by a factor of ca. 4 within each borehole, and heat production by a factor of 10 between the boreholes. These findings prompt for detailed sampling and comprehensive assessment of thermal property variabilities for applications involving the thermal field.

Accurate constraint of the trapped charge population is necessary for precise temperature reconstruction using thermoluminescence (TL) palaeothermometry. Here, we assess the performance of existing measurement protocols to accurately determine TL signal growth of K- and Na-feldspar. We compare four different protocols - single aliquot regenerative dose (SAR), multiple aliquot regenerative dose (MAR; signal resetting by both bleaching and annealing), and multiple aliquot additive dose (MAAD). A key challenge in protocol reliability is sensitivity change related to signal reset at the beginning of measurement in regenerative protocols. We identify sensitivity change by comparison of initial slopes of the dose response curves of regenerative and additive protocols. Further, we compare equivalent doses (De) determined using the various protocols to those obtained from a single aliquot regenerative additive dose (SARA) measurement to assess protocol performance. While sensitivity change and the level of protocol performance are strongly dependent on the individual sample and temperature range, strong desensitisation of the feldspar TL signal in the lower temperature range (200-250 degrees C) during SAR and bleached MAR results in De overestimation and leads to the protocols' exclusion from further consideration. Annealed MAR and MAAD on the other hand show approximately equal performance. As the level of saturation is relevant for the reliability of MAAD results, we suggest that this is considered when choosing a measurement protocol, and that the choice of kinetic model for dose response is carefully evaluated.

The western European Alps are characterised by deeply incised valleys, however the timing of their formation and the impact of Quaternary glaciation on rates of erosion remains disputed. This is mainly due to a lack of geochronological methods that cover the timespan of 103-106 years. Electron spin resonance (ESR) thermochronometry has a high potential to fill this temporal gap because of its low closure temperature (

Abstract. Infrared stimulated luminescence (IRSL) dating is a common technique for dating feldspar-bearing sediment deposits. The technique is preferentially applied as a single aliquot regenerative (SAR) protocol derivative: Post-infrared infrared (pIR1stIR2nd) and multiple elevated temperature (MET) SAR protocols. Both of these techniques aim to reduce problems with unstable luminescence traps common to feldspars, known as anomalous fading. Elimination of the unstable IRSL signal component, which may lead to age underestimation, is achieved by sequential sampling of the IRSL signal at either two (pIR1stIR2nd) or a few (MET) discrete temperatures, usually in the range 50 °C to 290 °C. We propose a modified approach, the progressively elevated temperature (PET) IRSL SAR, which continuously records the luminescence signal while progressively elevating the sample temperature. The benefits of this approach include the generation of quasi-continuous data chains, beginning with the recorded PET-IRSL signal curves, over De-value curves relevant for palaeodose assessment, a-value curves used for dose-rate refinement, and g-value curves serving to assess the signal loss resulting from fading. In addition to anomalous fading problems, feldspars do not bleach as quickly and thoroughly as quartz, potentially resulting in age overestimation. The illustrative PET data curves may be useful in illustrating a sample´s bleaching and fading history. Thus, they may allow users to both reduce problems with anomalous fading and identify aliquots that are least impacted by incomplete bleaching.

Constraining the timing of landslides is crucial for deciphering their triggering mechanisms. Recent years have seen a high number of landslides in tropical regions emphasizing the need to explore the links between climate and slope instability over longer timescales. While considerable data exists for alpine, arctic, and arid regions, limited preservation of geomorphological features accounts for the lack of data in tropical environments (e.g., Pánek, 2019). The Rwenzori Mountains in Uganda offer a natural laboratory for such a study. The upper part of the range features multiple rockfall deposits that disrupt the glacially sculpted landscape, while the lower elevations are characterized by recent debris flows and active landslides. However, no chronological data currently exist for the major rockfall deposits in the Rwenzori Mountains. To address this gap, we used in-situ produced 10Be dating to establish the chronology for seven individual rockfall deposits. The concentrations of 10Be are relatively consistent, ranging from 1.61 ± 0.11 × 10⁴ to 2.96 ± 0.08 × 10⁵ atoms per gram of quartz. The resulting 10Be ages range from 0.8 ± 0.1 ka to 9.2 ± 0.6 ka, clustering during three distinct periods: 9–8 ka, 6–4.5 ka, and 2–1 ka. The 9–8 ka and 6–4.5 ka clusters correspond to periods of enhanced precipitation during the African Humid Period (~10–5 ka; Mason et al., 2024). They specifically align with the onset of warmer temperatures and a temperature optimum based on local lake records (Garelick et al., 2022). The more recent cluster (2–1 ka) aligns with a brief temperature increase (Garelick et al., 2022). These findings suggest that increased temperatures and precipitation create favourable conditions for triggering rockfall in the Rwenzori Mountains, highlighting the interplay between climate and slope instability in tropical glacial landscapes.

The impact of Quaternary glaciation on the exhumation of the western European Alps remains unclear due to a lack of geochronological methods that cover the timespan of 103-106 years. In this study, we combine new ultra-low temperature (

The Middle and Upper Palaeolithic sites in the Carpathians and Danube lowlands constitute key contexts for tracing the dispersal of Homo sapiens into central-western Europe and the replacement of Homo neanderthalensis. Surprisingly, the Romanian archaeological inventory lacks transitional technologies and only a few sites have been systematically excavated and numerically dated, explaining the incomplete understanding of the Middle Palaeolithic and hence Neanderthal population dynamics. Here we present new age constraints for the Abri 122/1200 and Pestera Mare caves in the Romanian Carpathians, obtained by radiocarbon dating of charcoal and bone and by optically stimulated luminescence (OSL) dating of cave sediments. Methodological issues and the method's upper limit cause grossly underestimated radiocarbon ages for charcoal from Abri 122/1200 and provide only minimum ages (>41-60 14C ka bp) for bones from Pestera Mare cave. However, the OSL ages suggest Middle Palaeolithic cave occupation in the Carpathians since early Marine Isotopic Stage (MIS) 7 and lasting at least until MIS 5. These ages reinforce the vast potential of Carpathian cave sites in solidifying our understanding of Neanderthal dynamics in the region and their habitats. We discuss the reliability of this new chronology and the archaeological implications for the Middle Palaeolithic of neighbouring areas.

Droughts are amongst the most significant natural hazards in the central and southern Great Plains (USA). Chronologies of droughts and related dune activity phases in the Great Plains are paramount for understanding the frequency and magnitude of these potential risks. Beyond historical records, the timing and magnitude of droughts can be revealed only from sediment archives. Our joint DFG/SNF project, CONSTRAIN, aims to provide a new, accurate, and precise temporal placement of prehistoric droughts in the Great Plains, specifically the Nebraska Sand Hills, over the last 1,500 years. We combine methodological research (zircon luminescence dating, luminescence screening) with high-resolution quartz OSL dating to better understand the regional landscape dynamics. Our collaboration is currently in a pilot phase, performing the first methodological tests and identifying suitable archives for dating. In our first field season, we sampled sand blowouts in the Nebraska Sand Hills identified from LiDAR data. These widespread crater-like depressions (Stubbendieck et al., 1989) are similar to modern blowouts but are grass-covered, suggesting they are likely prehistoric. Still, they remain poorly studied. The blowouts are deflation hollows that seem unrelated to anthropogenic activity or disturbance through wild animals. Instead, they likely formed from drought events that resulted in aeolian deflation on dune crests, but they were either of lower magnitude or shorter-lived than droughts that reactivated the dunes that last moved between 1,000 to 600 years ago (Mason et al., 2004; Miao et al., 2007; McKean et al., 2015). Our contribution presents field luminescence screening results from 141 samples and the first optically stimulated luminescence (OSL) quartz ages derived from standard measurements testing the hypothesis that the naturally occurring blowouts are related to partial dune reactivation phases between 800 to 200 years ago. References Mason, J. A., Swinehart, J. B., Goble, R. J., and Loope, D. B.: Late-Holocene dune activity linked to hydrological drought, Nebraska Sand Hills, USA, The Holocene, 14, 209–217, https://doi.org/10.1191/0959683604hl677rp, 2004. McKean, R. L. S., Goble, R. J., Mason, J. B., Swinehart, J. B., and Loope, D. B.: Temporal and spatial variability in dune reactivation across the Nebraska Sand Hills, USA, The Holocene, 25, 523–535, https://doi.org/10.1177/0959683614561889, 2015. Miao, X., Mason, J. A., Swinehart, J. B., Loope, D. B., Hanson, P. R., Goble, R. J., and Liu, X.: A 10,000-year record of dune activity, dust storms, and severe drought in the central Great Plains, Geology, 35, 119–4, https://doi.org/10.1130/g23133a.1, 2007. Stubbendieck, J., Flessner, T. R., and Weedon, R.: Blowouts in the Nebraska Sandhills: The Habitat of Penstemon haydenii, Proceedings of the North American Prairie Conferences, 223–225, 1989.

Constraining the timescales of sediment transport by glacier systems is important for understanding the processes controlling sediment dynamics within glacierized catchments, and because the accumulation of supraglacial sediment influences glacier response to climate change. However, glacial sediment transport can be difficult to observe; sediment can be transported englacially, subglacially, supraglacially or at the ice margins, and may be stored temporarily on headwall slopes or within moraines before being (re-)entrained and transported by glacier ice. This study is a proof of concept of the use of luminescence rock surface burial dating to establish rates of englacial sediment transport. Our novel approach combines luminescence rock surface burial dating of englacial clasts with an ice-flow model that includes Lagrangian particle tracking to quantify rates of sediment transport through the Miage Glacier catchment in the Italian Alps. Luminescence rock surface burial ages for seven samples embedded in the near-surface ice in the ablation area range from 0.0 +/- 1.0 to 4.7 +/- 0.3 ka and are consistent with the ice-flow model results. Our results show that the transport durations of individual clasts vary by an order of magnitude, implying rapid clast transport near the glacier surface and longer transport histories for clasts transported lower in the ice column. In some cases, clasts were stored on the headwalls or within ice-marginal moraines for several thousand years before being englacially transported. The results illustrate the different routes by which glaciers transport sediment and provide the first direct measurements of englacial sediment transport duration.

Base level fall on a tributary is genetically related to its trunk channel incision, and analysis of tributaries thus provides information of the trunk channel evolution history. In the middle Yellow River, for example, several integration processes were proposed and should be consistent with river terrace data from the trunk channel. We investigate the rates and spatiotemporal variations of incision along the Jinshan Gorge in the middle Yellow River with dated strath terraces from its tributaries. The incision rate for six tributaries along the Jinshan Gorge is constrained using mapped and dated terraces. By comparing terraces of similar age, we find generally decreasing incision rates from the confluence with the trunk river to upstream within a tributary in the southern Jinshan Gorge. Decreasing incision rates are also observed among tributaries from south to north along the gorge. The results independently confirm the spatial pattern from “pseudo-terraces” derived from channel profile modeling. This interpretation reinforces the previous proposal that paleo-lake regressions in the Weihe Graben or integration with the Hetao Graben are unlikely to have been responsible for recent incision. An estimation method with terrace data within a tributary of erodibility coefficient, K, a crucial parameter for river profile inversion analysis, is also provided. K is recalibrated to be 1.03 10-5 m0.3/a with all terrace data. With an assemblage of published terrace data along the Jinshan Gorge, we suggest a re-examination of published terrace ages, which may help unravel the mysterious evolution history of the middle Yellow River.

Constraining the pathways and time scales of englacial sediment transport is of primary importance for both understanding the processes that move sediment through glacierised catchments and quantifying the response of mountain glaciers to climate change. However, sediment transport through glaciers is a more complex process than ice flow and difficult to observe; clasts can be transported englacially and at the ice margins, but also deposited into moraines before being re-entrained into englacial transport. We developed a novel method taking a Lagrangian approach that combines luminescence rock surface burial dating of the time for englacial transport of individual rock debris with ice-dynamical glacier evolution modelling of glacial sediment transport to quantify rates of sediment transport through the Miage Glacier catchment in the Italian Alps. Luminescence rock surface burial dating allows determining the burial duration of rocks after they have been exposed to sunlight, but this method has not previously been applied to englacial clasts. We obtained luminescence ages for seven samples embedded in the ice in the ablation zone of Miage Glacier, with burial ages ranging from 0.2 ± 0.1 ka to 5.0 ± 1.4 ka. Samples collected in the upper part of the ablation zone yield younger ages than samples collected near the terminus. The younger luminescence ages (0.2 ± 0.1 ka and 0.3 ± 0.1 ka) are consistent with expected burial duration based on the present-day glacier velocity. In contrast, older luminescence ages obtained for samples located in the lower part of the ablation zone (1.2 ± 0.1 ka to 5.0 ± 1.4 ka) show that these samples record a longer and more complex burial history, suggesting that these samples were either stored in the headwall area or within moraines for several thousand years before being entrained in the ice. In the Miage catchment, debris could have been stored in a moraine at the junction between the Bionnassay Glacier and the Dome Glacier before being entrained in the Miage glacier. We compare the burial ages of the englacial clasts with simulations of glacial sediment transport using a Lagrangian particle tracking scheme in the glacier model iSOSIA. The model results illustrate the range of englacial and subglacial sediment flow paths through the Miage Glacier and simulate similar durations of englacial transport to those obtained for our luminescence samples.

In south-western Martinique (Lesser Antilles), the Pointe Burgos Basaltic monogenetic strombolian cone and lava flow cut through a porphyritic dacitic lava dome (Morne Champagne) dated at 617 ± 52 ka (Germa et al., 2011). An exceptional feature of the basaltic lava flow is the occurrence of about 4% of large (up to 2 cm) quartz crystals. Previous studies suggested that quartz xenocrysts had been added to the basaltic magma upon mechanical magma mixing with the cooled shallow dacitic reservoir, with a 9:1 ratio. Indeed, plagioclase phenocrysts (>1 cm) present resorbed surface and reaction rims, a well-known evidence of crystal remobilization. However, no other textural evidence of magma mixing is visible in the basaltic edifice. Moreover, the quartz crystals present unusual habits, are heavily cracked, and appear as filling voids in the basalt. This led us to investigate the age of the basaltic eruption and of the quartz crystals to propose a scenario for the xenocrysts’ origin.The groundmass of the basaltic lava flow was K-Ar dated at 379 ± 25 ka, therefore ~240 ka after the eruption of the dacitic dome that it cuts through. Such a long time difference suggests that magma in the shallow reservoir was completely solidified when the basaltic magma ascended through it. Therefore, we would have expected to see also enclaves of dacite included in the basalt. Thermoluminescence (TL) dating allows for estimating the time since mineral formation or the last heating of a mineral above ~350 °C, thus representing an ideal tool to test whether the quartz xenocrysts formed synchronously with lava flow, or if they were formed later as substitutional minerals or void fillings. Here, we used red TL in combination with several protocols for dose determination, yielding consistent results. For assessing the dose rate, we took into account the quartz xenocrysts’ size distribution, the radioelement concentration of the basaltic matrix and the sites’ erosive evolution. The latter is particularly important because the basaltic matrix is comparatively poor in radioactivity so that the share of the cosmic dose rate becomes important. We obtain preliminary TL ages of 345 ka (with a total erosion of 20 m) and 377 ka (with an erosion of 50 m), each with a ~7% uncertainty. This result emphasizes the importance of reconstructing the lava flow geometry for answering the research question. As we believe that scenario (1) is more plausible, our results indicate the xenocrysts were likely formed post-eruption, challenging the initially suggested model of magma mixing and favouring secondary precipitation or mineral substitution. In case of TL resetting through geothermal activity, the age would represent the cooling following its cessation. However, given the xenocrysts’ pseudomorphic habit, it appears more likely that they represent secondary precipitates from hydrothermal fluids in voids left by strong geothermal alteration of the basaltic host rock. ReferencesGerma, A., Quidelleur, X., Lahitte, P., Labanieh, S., Chauvel, C., 2011. The K–Ar Cassignol–Gillot technique applied to western Martinique lavas: a record of Lesser Antilles arc activity from 2 Ma to Mount Pelée volcanism. Quat. Geochronol. 6, 341-355.

Late Quaternary landscape evolution in tropical environments, such as Indonesia, remains poorly constrained due to limited prior studies and mineral properties that are challenging for luminescence dating. In this study, singleand multi-grain luminescence measurements of quartz and K-feldspar were explored for fill terrace deposits at the Kampar Kanan River, Indonesia. Our objective is to develop a chrono-stratigraphic framework that allows the reconstruction of late Quaternary fluvial morpho-dynamics, including climatic change. Quartz measurements were made using blue and green stimulation and single-aliquot regenerative dose (SAR) and double SAR protocols. However, as none of the quartz signals were fast component-dominated, they were not used for dating. Infrared-stimulated luminescence of multiple grains of K-feldspar at 50 degrees C (IR50) and post-infrared infrared-stimulated luminescence at 225 degrees C (pIR50IRSL225) yielded sufficiently bright signal intensities for dating, and ages were calculated using either the average dose (ADM) or minimum age model (MAM). The luminescence chronology based on fading corrected pIR50IRSL225 data yields ages from Marine Isotope Stage (MIS) 6 or earlier to MIS 1. The chrono-stratigraphy indicates that the river was likely aggradational during climate transitions from wet to dry with the deposition of more gravelly material, and erosional during colder periods when overbank deposition of fines may have been coincident with increased vertical river erosion due to a stronger monsoon.

Significant mass loss and increased rock debris cover have been observed across many mountain glaciers due to climate change. However, the dynamics of sediment transport through alpine glaciers are not fully understood and should be investigated to better constrain the future evolution of mountain glaciers under a changing climate. Englacial sediment transport is difficult to observe and to that end, we quantify the englacial transport time of debris within a glacier using a novel method combining luminescence rock surface burial dating and ice-flow modelling. Our study focuses on Mer de Glace, Mont Blanc Massif, French Alps, where supraglacial debris has expanded over the past 20 years.We collected near-surface rock debris (4–22 cm in diameter) of granite from the ablation area of Mer de Glace that we expect to have experienced different englacial transport durations. Under subdued red light, we cored the samples perpendicular to their surfaces and sliced the cores into ~1 mm discs for luminescence dating. We first evaluated whether the luminescence signals had been well bleached prior to deposition by measuring the evolution of luminescence signals with depth throughout the core (i.e. measurement of the bleaching plateau). We used a protocol comprising infra-red stimulation at 50 °C and 225 °C, followed by blue stimulation at 125 °C to explore the signals of different minerals with different luminescence properties. Of the 29 samples investigated, 20 were well bleached, exhibiting a clear plateau in luminescence signals with depth (following the approach of Rades et al., 2018). We are currently using a single-aliquot regenerative dose protocol to date the rock surfaces of these samples to obtain englacial transport durations. In the next step, we will contrast the englacial transport durations measured using luminescence with those predicted using the ice-flow model IGM (Jouvet et al., 2022), allowing us to better understand the dynamics of mountain glaciers over centennial to millennial time scales. ReferencesJouvet, G., Cordonnier, G., Kim, B., Lüthi, M., Vieli, A., & Aschwanden, A. (2022). Deep learning speeds up ice flow modelling by several orders of magnitude. Journal of Glaciology, 68(270), 651-664.Rades, E. F., Sohbati, R., Lüthgens, C., Jain, M., & Murray, A. S. (2018). First luminescence-depth profiles from boulders from moraine deposits: Insights into glaciation chronology and transport dynamics in Malta valley, Austria. Radiation Measurements, 120, 281-289.