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We present new data from the debris-rich basal ice layers of the NEEM ice core (NW Greenland). Using mineralogical observations, SEM imagery, geochemical data from silicates (meteoric 10Be, εNd, 87Sr/86Sr) and organic material (C/N, δ13C), we characterize the source material, succession of previous glaciations and deglaciations and the paleoecological conditions during ice-free episodes. Meteoric 10Be data and grain features indicate that the ice sheet interacted with paleosols and eroded fresh bedrock, leading to mixing in these debris-rich ice layers. Our analysis also identifies four successive stages in NW Greenland: (1) initial preglacial conditions, (2) glacial advance 1, (3) glacial retreat and interglacial conditions and (4) glacial advance 2 (current ice-sheet development). C/N and δ13C data suggest that deglacial environments favored the development of tundra and taiga ecosystems. These two successive glacial fluctuations observed at NEEM are consistent with those identified from the Camp Century core basal sediments over the last 3 Ma. Further inland, GRIP and GISP2 summit sites have remained glaciated more continuously than the western margin, with less intense ice-substratum interactions than those observed at NEEM.

This research has been funded by the Spanish Ministry of Science and Innovation (Projects: CGL2015-66997-R and PID2021-126357NB-100), and by the European Regional Development Fund (FEDER) and Plan de Ciencia Tecnología e Innovación del Principado de Asturias (PCTI) (Grant reference: FC-GRUPIN-IBI/2018/00076/040). The ASTER AMS national facility (CEREGE, Aix-en-Provence) is supported by the INSU/CNRS, the ANR through the “Projets thématiques d’excellence” program for the “Equipements d’excellence” ASTER- CEREGE action and IRD.

International audience; During the Late Pleistocene, an ice cap temporarily rested on the highest summit of the Black Forest, Feldberg, and on the surrounding region. Moraines inside the last glaciation maximum ice extent document subsequent glacial standstills and/or re-advances, but the chronology of the deglaciation remains largely unknown. In Sankt Wilhelmer Tal, moraines were mapped, and suitable moraine boulders were sampled for 10 Be cosmic ray exposure (CRE) dating. Equilibrium line altitudes (ELAs) during moraine formation were reconstructed to evaluate whether these can be used for local stratigraphical correlations. Geomorphological mapping revealed numerous icemarginal positions in the main valley and in two tributary valleys. CRE ages and ELAs indicate two discrete phases of glacial standstills and/or re-advances by 17-16 ka at the latest and no later than 14 ka, respectively. Differing ELAs across the study area preclude the use of ELAs for local stratigraphical correlations. Recalculated 10 Be CRE ages from other localities in Central Europe indicate similar periods of moraine formation, thus raising the question of a common climatic forcing. Additional sets of CRE ages are needed to answer this question. In addition, future studies should concentrate on determining the age of the last glaciation maximum in the Black Forest.

International audience; The Upper Garonne Basin included the largest glacial system in the Pyrenees during the last glacial cycle. Within the long-term glacial retreat during Termination-1 (T-1), glacier fluctuations left geomorphic evidence in the area. However, the chronology of T-1 glacial oscillations on the northern slope of the Central Pyrenees is still poorly constrained. Here, we introduce new geomorphological observations and a 12-sample dataset of 10Be Cosmic-Ray Exposure (CRE) ages from the Ruda Valley. This U-shaped valley, surrounded by peaks exceeding 2800 m a.s.l., includes a sequence of moraines and polished surfaces that enabled to reconstruct the chronology of the last deglaciation. Following the maximum ice extent, warmer conditions prevailing at ~15-14 ka, during the Bølling-Allerød (B-A) Interstadial, favoured glacial retreat in the Ruda Valley. Within the B-A, glaciers experienced two phases of advance/stillstand with moraine formation at 13.5 and 13.0 ka. During the early YD, glacial retreat exposed the highest surfaces of the Saboredo Cirque (~2300-2350 m) at 12.7 ka. Small glaciers persisted only inside the highest cirques (~2470 m), such as in Sendrosa Cirque, with moraines stabilizing at 12.6 ka. The results of this work present the most complete chronology for Pyrenean glacial oscillations from the B-A to the YD.

Cosmogenic radionuclide 10Be and 26Al targets (BeO and Al2O3) for AMS analysis are produced by a growing number of geochemical laboratories, employing different sample processing methods for the extraction of Be and Al from environmental materials. The reliability of this geochronological tool depends on data reproducibility independent from the preparation steps and the AMS measurements. Our results demonstrate that 10Be and 26Al concentrations of targets processed following different, commonly used protocols and measured at two AMS facilities lead to consistent results. However, insoluble fluoride precipitates, if formed during processing, can cause decreased 26Al results, while 10Be concentrations are unaffected.

Argillaceous layers are often considered as impermeable formations preventing migration of contaminants. Nevertheless, porous and permeable layers in such formation may exist and play a role in contaminant dispersion. The objective here is to investigate the residence time of such porous and permeable layers based on a geochemical and isotopic approach.The study site is located on the Narbonne sedimentary basin, south of France. The Oligo-Miocene argillaceous sedimentary series overlays the cretaceous limestone substratum. A Quaternary deposit partially covers the Tertiary formations. On the western margin the Oligo-Miocene series abuts on the limestone formation. The Oligo-Miocene series is crossed by permeable to semi-permeable layers of conglomeratic deposits, from a few centimetres to a few meters thick, which may represent hydraulic short-circuit. Groundwater samples from the 3 formations were collected for analyses along with surface water samples, the Aude river, and rain water. The geochemical approach is based on the investigation of time tracers including 3H/3He, 14C and 36Cl/Cl along with the investigation of major and minor elements, stable isotope of water and strontium isotopes.Groundwater conductivity is relatively high ranging from 800 to 2000 µS/cm for the deepest bore hole in the cretaceous formation. Br/Cl and strontium isotope ratio show that groundwater from the permeable layers plot between groundwater from the limestone aquifer and a more mineralised end-member. Groundwater from the permeable layers are slightly depleted in stable isotopes of water with respect to modern precipitation, suggesting recharge under different conditions from the current one. 3H, below detection limit, shows the lack of modern recharge. 14C, in the order of a few pmc, would suggest a residence time of a few ten thousand years. The 36Cl/Cl ratio, in the order of 2x10-14 at/at, is nearly one order of magnitude lower than modern input. Groundwaters from the Oligo-Miocene permeable layers tend to plot on or below a mixing line between recent recharge and a chloride enriched and 36Cl depleted end-member, coherent with long residence time.All tracers are coherent with relatively long residence time and low circulation potential in the porous and permeable layers.

International audience; The Central Apennines are among the most seismically active regions in Italy. This region is affected by an extension accommodated by active normal faults. Those faults with high seismogenic potential hosted Mw > 6 shallow damaging earthquakes, such as the Mw 6.5 event of Oct. 30, 2016. Although fault slip rates are crucial to seismic hazard assessments, in the Central Apennines, slip rate assessments encompassing several seismic cycles (> 10 ka) are sparse. This is particularly true for the Mt. Vettore-Mt. Bove Fault system that ruptured during the mainshocks of the 2016–2017 seismic sequence. In this study, we present new geochronological constraints of offset geomorphological markers along the northern portion of the fault system on the Mt. Porche Fault segment using in-situ produced 36Cl cosmogenic nuclides. Offset measurements were made using a 5-cm resolution DEM obtained through a drone survey and constrained a fault scarp height of 15.5 ± 1.4 m and a maximal cumulative offset estimated between 32 and 40.5 m. Samples were collected from the Valle Lunga terminal moraine at 1710 m asl and yielded 36Cl exposure ages of 12.7 + 2.2/−1.9 ka, while the abraded surface, located on top of the tectonic scarp yielded 36Cl exposure ages of 23.4 + 5.3/−4.3 ka. Using the fault scarp height and the exposure age of this abraded surface, we constrained a minimum vertical fault slip rate of 0.7 + 0.2/−0.1 mm/yr. Assuming the offset started to accumulate when climate conditions allowed the scarp preservation, we constrained a maximal vertical slip rate of 1.2 ± 0.2 mm/yr along the main fault of the Mt. Vettore-Mt. Bove Fault system. This rate is higher than those previously obtained from trenches along secondary branches of the Mt. Vettore-Mt. Bove Fault system. Besides, the yielded chronology for the last glacial maximum in that area at ~23 ka is in good agreement with the timing previously proposed for the LGM in the Apennines.

Lake Turiec existed from Late Middle Miocene to Pliocene in the heart of the Western Carpathians in the intermontane Turiec Basin. Despite the long-lasting lacustrine deposition, which formed a muddy succession up to 900 m thick, specific history of this basin in Western Carpathians has been a puzzle due to the missing geochronological proxies. Authigenic 10Be/9Be dating method was applied to determine the existence duration and regression of the long-lived Lake Turiec. Altogether 35 samples were collected from 11 different localities of the basin representing different sedimentary environments such as lacustrine, fan delta, alluvial fan and braided river. Four different localities, Late Pleistocene alluvial fans Veľký Čepčín and Malý Čepčín, Holocene river floodplains Košťany and Kalamová were considered for determining the initial ratio. The initial ratio from the Veľký Čepčín alluvial fan was used for all other localities representing lacustrine, fan delta, alluvial fan and braided river to determine ages, because it is the only N0 in agreement with the independent age proxies indicating that the lacustrine deposits cannot be older than 11.6 Ma. Another explanation of the suitability of the Veľký Čepčín initial ratio is its rapid deposition settings, preventing it from alteration by post-depositional processes and interaction with ground water, in contrary to the remaining intial ratio sites. Weighted mean depositional ages calculated using N0 from Veľký Čepčín imply that the Lake Turiec existed from ~9.96 Ma for more than ~3.25 Myr and regression of the lake begun nearly ~6.71 Ma. Determining the precise timing of the lake existence will have important implications for geodynamic phases of the Western Carpathians, since it mirrors rapid increase of accommodation followed by intense increase of sediment supply during regression. The presented application of authigenic 10Be/9Be yielded a first radiometric age of long-lived Lake Turiec as compared to roughly estimated age described in previous studies of the Turiec Basin. This novel method also appeared as a promising dating tool to determine the beginning of regression of the lake in an intermontane settings with complicated tectonic and sedimentary history. The study was supported by the Slovak Research and Development Agency under contract APVV-20-0120.

This study examines the suitability of the authigenic 10Be/9Be dating method to the dating of the deposits of an incising river, taking as an example the Nová Vieska river terrace, which accumulated during the neotectonic inversion of the Danube Basin (western Slovakia). The succession was formed by a wandering river with minor preservation of proximal floodplain muds. The frequent occurrence of mud intraclasts reflects a significant input of eroded material from underlying, older successions. The ages of 13 authigenic 10Be/9Be dating samples formed three groups: (1) samples from below the base of the river terrace yielded dates of ~4.13–3.70 Ma; (2) muddy intraclasts from the river terrace an age range of ~2.79–1.96 Ma; and (3) in situ muddy layers had ages in the range of ~1.91–1.39 Ma. The large mammal fossil assemblage from channel thalweg deposits yielded a biostratigraphic age of ~3.6–2.2 Ma, matching the age of intraclasts, and thus emphasizing the redeposited origin of those fossils. The relatively wide range of authigenic 10Be/9Be dating ages is interpreted as a result of the redeposition of mud from older strata on three scales: decimeter-scale intraclasts, millimeter-scale rip-up clasts mixed into the newly formed beds, and formation of two authigenic rims with different age and 10Be/9Be record around individual particles. Considering these observations, an age range of in situ layers of ~1.91–1.39 Ma is proposed as the depositional age of the river terrace. The effect of redeposition is thus shown to be potentially limiting to the application of authigenic 10Be/9Be dating to incising rivers, and stands in marked contrast with aggrading river settings, where redeposition of older sediment is limited and the degree of 10Be/9Be variability is low.

Scientific knowledge of the glacial evolution of the Cantabrian Mountains (NW Spain) has experienced important advances in the last four decades. There are numerous works focused on the description and mapping of glacial landforms, as well as on the application of age models based on relative chronologies and correlations with other Iberian mountain areas. However, the application of dating techniques to obtain absolute ages is very recent here, and has focused mainly on the highest altitude mountain ranges. In contrast, areas such as the Central-Western Asturian Mountains, with lower altitudes and less evident glacial footprints, have received scarce scientific attention. With the aim of establishing a solid geochronological framework of the deglaciation pattern, this study is focused on the northern slope of Puerto de Ventana. It is a paradigmatic example of the glacial evolution that occurred during the Last Glacial Cycle in the Central-Western Asturian Mountains due to its altimetric and lithostatigraphic characteristics: moderate altitudes (Ferreirúa Peak, 1977 m a.s.l.) and predominance of quartzites, sandstones and slates of Paleozoic age. During the summer of 2021 we carried out an exhaustive fieldwork campaign, from which a detailed geomorphological mapping was carried out, and a total of 17 samples for 10Be Cosmic-Ray Exposure dating purposes were collected. Sampling strategy has been based on the in situ evaluation of each of the glacial landforms identified, and the search for the most suitable glacial boulders and surfaces. Specifically, two moraines belonging to the outermost moraine complex have been dated, obtaining age ranges from 64 to 34 ky (MIS 4-3). This shows that there is an asynchrony between the Maximum Ice Extend (MIE) of the Ventana Glacier and the global Last Glacial Maximum (gLGM), as has been confirmed in other Cantabrian and Iberian Mountain areas. In the internal moraine complexes, eight samples have been obtained, which provide ages of 25-18 ky, indicating their correlation with the gLGM (MIS 2). Therefore, it would be the second glacial stage in the evolution of the Ventana Glacier. Regarding the moraine complexes located at the foot of glacial cirques, two blocks belonging to a frontal moraine arch were dated, as well as three belonging to a rock glacier. Both the chronologies of the above-mentioned moraine complex and the rock glacier, seem to indicate that they are contemporary to the interstadial warm period known as Bølling-Allerød, in which the last stages of glacial retreat would take place, as well as the stabilization of the rock glacier. Acknowledgment:Benjamín González Díaz appreciates the support of the Spanish FPU program (reference: FPU19/06583). This contribution studies the research topics addressed in the project PID2020-115269GB-I00 (MICINN, Government of Spain).

The glacial history of the Iberian Peninsula, both glacial landforms and associated deposits, as well as the geochronology framework of the successive glacial stages within the Last Glaciation (LG), is now better understood. In turn, there is a growing body of evidence on glacial stages prior to LG. The increased use of absolute dating techniques has made these advances possible. However, some issues should be addressed to fully understand the extent and significance of past glacial processes in the Iberian Mountains. Those areas that were marginally affected by the ice during the LG (that is, located in low or moderate altitude sectors) remain unexamined in depth, with few geochronological contributions. These are more distant areas and often far from the main research focus. Moreover, the finding of glacial evidence (generally scarcer) is hindered by a dense vegetation cover. This is the case of A Seara Valley (Courel Mountains), located in the NW edge of the Iberian Peninsula, where several boulders and erosion surfaces of glacial origin were sampled for 36Cl Cosmic-Ray Exposure (CRE) dating. Nine samples were collected during the spring2019 fieldwork campaign. Additionally, the paleoglacier was reconstructed and the associated landforms were mapped. Sampling strategy was challenging because only few moraines are well-preserved, and suitable boulders for CRE dating are scarce due to the predominant outcropping of slates. Only one moraine ridge was located at the bottom of A Seara Valley (1113 m a.s.l.), in which seven samples were collected. It is a polygenic moraine, dismantled by postglacial processes. Besides, the discrepant ages obtained in some boulders show that they were probably covered by sediments. The oldest geochronological data indicates that, at least, the glacier connected with this moraine at 21 ka (MIS-2). Additionally, two samples were collected on a glacial polished threshold located in an intermediate sector of the valley, at 1243 m a.s.l. Here, the result of 19 ka points to an accelerated retreat of this glacier to its headwater (as in other glaciated areas of NW Spain), i.e., a very quick deglaciation process. Acknowledgments:Benjamín González Díaz appreciates the support of the Spanish FPU program (reference: FPU19/06583). This contribution studies the research topics addressed in the project FUO-19-112 (Courel Mountains UNESCO Global Geopark; Ribeira Sacra-Courel Local Action Group, LEADER Program of the European Union).

We present a new set of 25 10Be surface exposure ages of boulders located on the Pomeranian moraines and of erratic boulders located directly upstream of the Pomeranian moraines in northern Poland. Together with recalculated 10Be surface exposure ages along the Pomeranian Phase ice-marginal belt from Denmark to the west to Lithuania and Belarus to the east, the full data set (n = 86) enabled us to constrain the timing of the ice front standstill and its subsequent retreat. The investigated area consists of geomorphological record along ~2000 km of the ice margin associated with the ice sheet limit correlated so far with the Late Weichselian Pomeranian Phase (Bælthav in Denmark, Baltija in Lithuania and Braslav in Belarus).We constrained the age of the ice margin position in the area occupied by the Baltic Ice Stream to ~20–19 ka, in the area occupied by the Odra Ice Stream to ~19–18 ka, in the interstream area between the Odra and the Vistula Ice Streams to ~20–19 ka, in the area occupied by the Vistula Ice Stream to ~19–18 ka, in the area occupied by the Mazury Ice Stream to ~18–17 ka, in the area occupied by the Riga Ice Stream to ~17–16 ka, and in the area occupied by the Novgorod Ice Stream to ~16–15 ka. Our best age estimates are based on: (1) a minimum age of the ice margin retreat inferred from new and recalculated 10Be ages of boulders as well as interpretation of available radiocarbon ages from organic deposits and OSL ages from sediments overlying tills, and (2) a maximum age of the ice margin stillstand and retreat inferred from interpretation of available OSL ages from sandur sediments deposited in front of the ice sheet. The asynchrony of the ice margin positions along the Pomeranian Phase ice-marginal belt shows about 3–5 ka difference between the Bælthav ice margin in Denmark and the Braslav ice margin in Belarus. We propose a new scenario of the Pomeranian Phase ice sheet evolution and a time-slice reconstruction of the last Scandinavian Ice Sheet’s southern fringe for the period ~20–15 ka.

The weathering of continental surfaces and the transport of sediments via rivers into the oceans is an integral part of the dynamic processes that shape the Earth's surface. To understand how tectonic and climatic forcings control regional rates of weathering, we must be able to identify their effects on sedimentary archives over geologic timescales. Cosmogenic nuclides are a valuable tool to study rates of surface processes and have long been applied in fluvial systems to quantify basin-wide erosion rates. However, in large rivers, continual processes of erosion and deposition during sediment transport make it difficult to constrain how long sediments spend within the fluvial system. In this study, we examine the role of rivers in buffering erosional signals by constraining the timescales of fluvial transport in large rivers across the world. We apply a stochastic numerical model based on measurements of cosmogenic nuclides concentrations and calculate sediment residence times of 10(4)-10(5) years in large rivers. These timescales are equal to or longer than climatic cycles, implying that changes to rates of erosion brought on by climatic variations are buffered during transport in large rivers and may not be recognizable in the sedimentary record., Journal of Geophysical Research: Earth Surface, 127 (5), ISSN:0148-0227, ISSN:2169-9003, ISSN:2169-9011

The precise environmental mechanisms controlling Quaternary glacial cycles remain ambiguous. To address this problem, it is critical to better comprehend the drivers of spatio-temporal variability in ice-sheet evolution by establishing reliable chronologies of former outlet-glacier advances. When spanning multiple glacial cycles, such chronologies have the capacity to resolve conundrums on interhemispheric phasing of glaciations and climate events. In southern Argentina, reconstructions of this kind are achievable, as Quaternary expansions of the Patagonian Ice Sheet have emplaced a well-preserved geomorphological record covering several glacial cycles. Moreover, robust ice-sheet reconstructions from Patagonia are powerful barometers of former climate change, as Patagonian glaciers are influenced by the Southern Westerly Winds and its coupled Antarctic Circumpolar Current. Former shifts in these circulation mechanisms are essential to better constrain, as they may have played a critical role in pacing regional and possibly global Quaternary climate change. Here, we present a new set of cosmogenic 10Be and 26Al exposure ages from pre-Last Glacial Cycle moraine boulder, glaciofluvial outwash cobble and bedrock samples. This dataset constitutes the first direct chronology dating pre-LGM glacier advances in northern Patagonia, and completes our effort to date the entire preserved moraine record of the Río Corcovado valley system (43° S, 71° W). We find the outermost margins of the study site depict at least three distinct pre-Last Glacial Cycle glaciations occurring at 284 ± 7 ka, 257 ± 7 ka, and 147 ± 4 ka. Combined with the local LGM chronology, we discover that a minimum of four distinct Pleistocene glaciations occurred during Marine Isotope Stages eight, six, and two in northern Patagonia. Evidence for stage four and three deposits were not found at the study site, which illustrates former longitudinal and latitudinal asynchronies in Patagonian Ice Sheet mass balance during these stages. We find the most extensive middle-to-late Pleistocene expansions of the Patagonian Ice Sheet appear to be out-of-phase with local summer insolation intensity, but synchronous with orbitally-controlled periods of longer and colder winters. Our findings thus enable to explore the potential roles of seasonality and seasonal duration in driving southern mid-latitude ice-sheet mass balance and facilitate novel glacio-geomorphological interpretations for the study region. They also provide empirical constraints of former ice-sheet extent and dynamics that are essential to calibrating numerical ice-sheet and glacial isostatic adjustment models.

The chronology of the arrival of Homo erectus on the island of Java is a cornerstone of paleoanthropology. Understanding the dispersal routes of Homo erectus, but also of other hominin lineages in Asia and across Southeast Asia, depends on this timing. Their dispersal across Sundaland, in particular, is challenged by an extremely transient climatic and geological environment during Early Pleistocene. Furthermore, ages of first appearance of Javanese H. erectus remain controversial. New age constraints based on cosmogenic nuclides 10Be and 26Al produced in situ indicate that H. erectus reached Java and dwelled at Sangiran at least ~1.4 Ma ago and more probably around 1.8 Ma. During this period, Java was just emerging from the sea while the adjacent Sundaland was a vast and continuous expanse of climatically and environmentally hospitable land connecting Java to mainland Asia, which facilitated the prior dispersal of hominins and terrestrial faunas to the edge of Java. This ancient age makes H. erectus the contemporary of the earliest members of the genus Homo in Africa and Asia, and rejuvenates the question of dispersal and evolutionary pathways across Eurasia and Sundaland.

The Greenland Ice Sheet (GrIS) is a key component of the global climate system. However, our current understanding of the spatio-temporal oscillations and landscape transformation of the GrIS margins since the last glacial cycle is still incomplete. This work aims to study the deglaciation in the Zackenberg Valley, Greenland, and the origin of the derived glacial landforms. In order to reconstruct the spatial extent and geometry of past glacial phases we carried out extensive fieldwork and high-detailed geomorphological mapping, together with cosmic-ray exposure (CRE) dating to samples from erosive and depositional glacial landforms. Erratic boulders dispersed across the summits suggest that Late Quaternary glaciers filled the valleys and fjords during periods of maximum ice expansion. As glacier thickness decreased, the Zackenberg glacier was confined in the interior of the main valley, leaving several lateral moraine ridges along the slopes. The deglaciation started by ~13.7-12.5 ka and accelerated paraglacial slope processes (e.g. solifluction). By ca. 10.5 ka, the last remnants of glacial ice disappeared from the lower sections of the valley. This deglaciation chronology broadly agrees with what is observed in other sites across Greenland.

*Georges Aumaître, Didier L. Bourlès, Karim KeddadoucheLocated in northeastern France, the Vosges Mountains (VM) belongs to these Hercynian ranges strewn across the European alpine foreland. Peaking at ~1425 m of elevation, it presents four contrasting primary characteristics. Firstly, the geological basement allows a bipartite N-S subdivision: the Palaeozoic southern part (crystalline Vosges) composed of various igneous, metamorphic and sedimentary rocks contrasts with the much more homogeneous Triassic cover in the northern part (sandstone Vosges). Secondly, a clear E-W topographic gradient is reflected by steep hillslopes on the eastern side (Alsace) and gently-sloping hillslopes on the western side (Lorraine). Thirdly, a sharp W-E precipitation gradient (>1000mm/yr) is recorded between the windward and the leeward side. Finally, the imprint left by Quaternary climatic fluctuations yields a N-S gradient: whereas the crystalline Vosges hosted abundant valley glaciers, the sandstone Vosges were void of ice cover.Owing to these advantageous characteristics, this contribution aims to present the first data of catchment-wide denudation at the massif scale and to explore the long-term interactions between denudation, lithological control, morphometry and climatic forcing. Modern stream sediments from 21 river catchments draining the whole massif were sampled for in situ 10Be and 26Al concentration measurements at the outlet of their mountainous reach. The mean Channel Steepness Index (ksn) was computed as a morphometric “predictor” of denudation rates. Groups of lithologically uniform catchments were statistically identified based on their lithological surficial proportions.Catchment-wide denudation rates inferred from cosmogenic 10Be and 26Al concentrations range from 33 to 83 mm/ka and 38 to 337 mm/ka, respectively. The [26Al]/[10Be] ratio range from 1.43 to 7.96, highlighting a complex exposure history for the glaciated catchments. At the massif scale, results show (i) no relation between denudation and steepness, (ii) a strong positive relation between denudation and precipitations when lithological groups are considered and (iii) a negative relation between the surficial proportion of fluvio-glacial deposits in the catchment and the [26Al]/[10Be] ratio.To our knowledge, this contribution is the first massif-scale attempt to quantify denudation in an European low- to medium-altitude mountain range. This is especially relevant as long-term landscape evolution in the Variscan belt, by contrast to the numerous works focusing on denudation in high-mountains ranges (e.g. the Alps), has been regularly disregarded in recent geomorphological studies. Importantly, whereas a vast majority of studies measuring denudation rates rely on 10Be concentrations only, this study highlights the need of using a pair of cosmogenic nuclides (i.e. 26Al/10Be) to check whether stream sediments in formerly glaciated catchments have experienced complex exposure history.

The Upper Garonne Basin constituted the longest glacier of the Pyrenean ice field during the Late Pleistocene. From the peaks of the axial Pyrenees that exceed 2,800-3,000 m, the Garonne palaeoglacier flowed along ~80 km northwards during the major glacial advances reaching only 420-440 m. This palaeoglacier reached the Pyrenean foreland, at the Loures-Barouse-Barbazan basin (LBBB) where it formed a terminal moraine complex that is examined in this work. We have constrained the timing of the maximum glacial extent as well as the onset of the deglaciation from the end of the Last Glacial Cycle (LGC) based on the geomorphological observations and a 12-sample dataset of 10Be Cosmic-Ray Exposure (CRE) ages. There are two moraine systems at the LBBB, where the first is composed of weathered ridges at the outermost part of the basin and the second encompasses well-preserved ridges stretching across the innermost part of the basin. Chronological data shows that the external moraines were abandoned by the ice at the end of the Penultimate Glacial Cycle (PGC) and the onset of the Eemian Interglacial, at ~129 ka. The few existing reliable boulders to date in the internal moraine showed inconsistent ages as they were probably affected by post-glacial processes and therefore, this work adds no evidence of subsequent glacial advances or standstills during the LGC in the LBBB. However, the terminal basin was already deglaciated during the global Last Glacial Maximum (GLGM) at 24-21 ka, as revealed by exposure ages from polished surfaces at the confluence of the Garonne-la Pique valleys, 13 km south of the entrance of the LBBB. This study introduces the first solid CRE database in the Pyrenees for the glacial advance that occurred during the PGC and provides also new evidence from the GLGM when the Garonne palaeoglacier had already significantly shrunk.

As one of the major erosive processes acting at Earth’s surface, fluvial incision is highly sensible to tectonic, isostatic and climatic variations. In order to better understand what is the timing and driving mechanism(s) for Late-Quaternary incision in the Southwestern Alps, we focused on bedrock gorges and measured in situ-produced 36Cl concentrations along several river-polished gorge walls in the external Southwestern French Alps. Unlike previously dated river gorges in the study area, these newly dated catchments lie out of the previously glaciated domains during the last glacial periods, which makes them suitable to quantify fluvial incision dynamics in a non-glacial environment.Cosmic-ray exposure dating results (ranging from 1 to 85 ka), compared to previous literature results in nearby catchments with glacial imprint and combined with a morphometric analysis, allow us to highlight three catchment groups related to different incision dynamics: (i) Group A with very high (≈5 mm/yr) and recent (post-10 ka) incision rates that reflect recent topographic readjustment of glaciated catchments by fluvial and hillslope processes; (ii) Group B, including gorges that are directly or indirectly connected to the glacial processes, showing increased incision rates (1-3 mm/yr) during the paraglacial period after the Last Glacial Maximum (ca. 20 ka), possibly related to an increase in sediment yield and water runoff following glacier retreat; (iii) Group C with slow and steady incision rates (In catchments with glacial imprints, the climatic impact on fluvial incision is evidenced through high amplitudes changes that hinder the long-term (background) tectonic signal. Despite this, our results suggest the influence of long-term tectonic on geomorphic processes for sites disconnected from the glacial influence, showing that fluvial bedrock gorges can provide insightful constraints on both long-term tectonic and short-term climatic forcing.

Discovered in 1988 by R. Oslisly and B. Peyrot, Elarmékora is a high terrace that, today, is situated 175 m above the Ogooué River in the historical complex of Elarmékora, attached to the Lopé National Park in Gabon, a World Heritage site since 2007. The site yielded a small lithic assemblage, including mainly cobble artefacts embedded within the 1 m thick alluvial material. Based on geomorphological and palaeoclimatological criteria, the preliminary dating suggested an age of 400 ka. However, Elarmékora could be a key site for Atlantic Central Africa if this lithic industry can be dated absolutely. In 2018 and 2019, two field trips were organized to collect surface samples as well as samples in vertical depth profiles with the aim of measuring their in situ -produced cosmogenic nuclide ( 10 Be and 26 Al) content. Results suggest a surface abandonment between 730 and 620 ka ago representing a minimum age for the cobble artefacts. Concurrently, technological reappraisal of the artefacts suggests an atypical lithic industry that should, for the moment, be considered as ‘undiagnostic’ Earlier Stone Age. This age bracketing may be compared with a similar age range obtained for prehistoric occupations in Angola using the same approach. This age will place Elarmékora among the oldest evidence for the presence of hominins in western Central Africa and raises the question of a ‘West Side Story’ to early human dispersals in Africa. This article is part of the theme issue ‘Tropical forests in the deep human past’.

International audience; It is of major importance for Earth surface sciences to reconstruct denudation rates in the most precise and accurate way. For this, it can be useful to test on the same setting methods based on different assumptions, such as those relying on geomorphological and geochemical observations. Here, we use an exceptionally suited setting in the Locumba catchment (southwestern Peruvian Andes) that offers the unique opportunity to compare denudation rates derived from in situ cosmogenic 3He and 10Be with a geomorphological sediment budget integrated over the last 18 ka. The sediment budget is estimated by determining the volume of sediment trapped in the Aricota lake that formed 18 ka ago after the occurrence of a giant rockslide dam. We reconstructed the topography of the Locumba valley before the dam emplacement and established that the captured sediment volume is 0.8 ± 0.1 km3. Considering that the lake-water output is restricted to seepage through the dam and that overflow above the dam never occurred, this volume correctly represents the sediment flux integrated over the last 18 ka. Integrating this volume over the upstream catchment area (∼1500 km2), we derived a corresponding mean erosion rate of 30 ± 9 mm.ka-1. Fluvial sediments feeding the Aricota lake were sampled to derive denudation rates from in-situ cosmogenic 10Be in the silicates and from in-situ cosmogenic 3He in the ferromagnesian minerals. Cosmogenic nuclide denudation rates from the main stream are 30 ± 2, 33 ± 2, 21 ± 1 and 82 ± 5 mm.ka-1 for the 10Be-quartz, the 10Be-feldspar, the 3He-amphibole and 3He-pyroxene, respectively. The consistency between the cosmogenic nuclide denudation rates derived from 10Be in the silicates and the erosion rate derived from our sediment budget shows that the 10Be accurately estimates of the sediment flux. Additionally, this work provides the first successful application of 10Be-feldspar nuclide-mineral pair to derive catchment-mean denudation rate and demonstrate that 10Be-feldspar can thus be a good alternative in catchments dominated by volcanic rocks with no quartz. The discrepancies observed between the denudation rates derived from the 3He-amphibole and 3He-pyroxene couples require further studies.

International audience; This study examines the suitability of the authigenic 10Be/9Be dating method to the dating of the deposits of an incising river, taking as an example the Nová Vieska river terrace, which accumulated during the neotectonic inversion of the Danube Basin (western Slovakia). The succession was formed by a wandering river with minor preservation of proximal floodplain muds. The frequent occurrence of mud intraclasts reflects significant input of eroded material from underlying, older successions. The ages of 13 authigenic 10Be/9Be dating samples formed three groups: (1) samples from below the base of the river terrace yielded dates of ~4.13–3.70 Ma (including uncertainties); (2) muddy intraclasts from the river terrace gave an age range of ~2.79–1.96 Ma; and (3) in situ muddy layers had ages in the range of ~1.91–1.39 Ma. The large mammal fossil assemblage from channel thalweg deposits yielded a biostratigraphic age of ~3.6–2.2 Ma, matching the age of intraclasts, and thus emphasising the redeposited origin of those fossils. The relatively wide range of authigenic 10Be/9Be dating ages is interpreted as a result of the redeposition of mud from older strata on three scales: decimetre!scale intraclasts, millimetre!scale rip!up clasts mixed into the newly formed beds, and formation of two authigenic rims with different age and 10Be/9Be records around individual particles. Considering these observations, an age range of in situ layers of ~1.91–1.39 Ma is proposed as the depositional age of the river terrace, with the most probable age falling within the most recent part of this interval. The effect of redeposition is thus shown to be potentially limiting to the application of authigenic 10Be/9Be dating to incising rivers, and stands in marked contrast to aggrading river settings, where redeposition of older sediments is limited and the degree of 10Be/9Be variability is low.

International audience; Cosmogenic nuclide dating of glacial landforms on the Kerguelen Archipelago (49°S, 69°E) gives the opportunity to study multi-millennial glacier fluctuations within the sub-Antarctic sector of the Indian Ocean. We here dated such geomorphic features to provide time constraints over the last 17,000 years using in situ-produced 36Cl in three glacial valleys: Val Travers valley, Ampere Glacier valley and Arago Glacier valley. For the first time, a combination of in situ-produced 36Cl and 10Be dating and 26Al/10Be ratios analysis was performed in the quartz-bearing syenite boulders of the Arago Glacier site. In addition, a Bayesian approach was computed to obtain a better constraint on moraine dating. Glacial advances occurred during the Late Glacial at 16.0 ± 1.9 ka and at 12.9 ± 1.7 ka in Val Travers, and at 13.6 ± 1.8 ka in Arago Glacier valley, probably linked to the Heinrich Stadial 1 and/or Antarctic Cold Reversal events, respectively. This suggests that all glaciers at this latitude were broadly sensitive to the large-scale climatic signal of the Antarctic Cold Reversal. So far, no Early nor Mid-Holocene moraines have been found in the glacial valleys on Kerguelen, indicating that the glaciers had probably receded significantly during these periods. This is in agreement with previously determined 14C ages from peat bogs, which suggest extensive deglaciation during several millennia of the Holocene period. Samples from glacially-polished bedrock surfaces (ranging from ~4.4 ka to ~14 ka) at Ampere Glacier site also suggest that this valley was ice free for several millennia during the Holocene. Finally, glaciers seem to have re-advanced only during the Late Holocene, especially within the last millennium, at ~1 ka, ~430 yr and ~300 yr. A comparison of this new dataset with the available 10Be ages from other southern mid latitude regions during the Holocene allows the identification of three different glacier evolution patterns. We suspect that variations of Kerguelen glaciers, which are located in the Southern Indian Ocean, were controlled by the combined effects of sea surface temperature related to the variations of the Antarctic Polar Front and fluctuations of precipitation related to long-term variations of the Southern Annular Mode.

International audience; Despite their significance for estimating hazards and forecasting future activity, dating young volcanic deposits and landforms (< 50,000 yrs old) remains a challenge due to the limitations inherent to the different isotopic chronometers used. The Trans-Mexican Volcanic Belt is one of the most active and populated continental arcs worldwide, yet its temporal pattern of activity is poorly constrained. Such deficiency is particularly problematic for the Sierra Chichinautzin Volcanic Field (SCVF) that is located at the doorstep of Mexico City and Cuernavaca and is hence a major source of risk for these cities. Existing ages for this area derive mostly from either radio-carbon on charcoal, which is rare and may be contaminated, or 40Ar/39Ar on rock matrix, which is poorly precise for this time period and rock type. Here, we focus on the Pelado monogenetic volcano, which is located in the central part of the SCVF and erupted both explosively and effusively, producing a large lava shield and a widespread tephra blanket. This unique eruptive event was previously dated at similar to 12 calibrated (cal) kyrs BP, using radiocarbon dating on charcoal from deposits related to the eruption. To test alternative dating approaches and confirm the age of this significant eruption, we applied two less conventional techniques, radiocarbon dating of bulk paleosol samples collected below the complete tephra sequence at nine sites around the shield, and in-situ Cl-36 exposure dating of two samples of an aphyric lava from the base of the shield. Radiocarbon paleosol ages span a continuous time interval from 13.2 to 20.2 cal kyrs BP (2 sigma), except for one anomalously young sample. This wide age spread, along with the low organic contents of the paleosols, may be due to erosive conditions, related to the sloping topography of the sampling sites and the cool and relatively dry climate of the Younger Dryas (11.7-12.9 ka), during which the Pelado eruption probably occurred. The two Cl-36-dated lava samples have consistent ages at 1 sigma analytical errors of 15.5 +/- 1.4 ka and 13.2 +/- 1.2 ka, respectively, yielding an average age of 14.3 +/- 1.6 ka for this lava flow. The high full uncertainty in Cl-36 ages (24%) is due to high rock Cl content. We conclude that paleosol radiocarbon dating is useful if numerous samples are analyzed and climatic and relief conditions at the time of the eruption and at the sites of tephra deposition are considered. The Cl-36 dating technique is an alternative method to date volcanic eruptions, as it gave consistent results, but in the specific case of Pelado volcano, the high Cl content in the analyzed rocks increases the age uncertainties.