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Over the last few decades the importance of geochronology in Quaternary studies has significantly increased and the development of accurate numerical dating tools has become an essential foundation for reliable interpretations of palaeoenvironmental proxies, landscape evolution, geomorphic processes, palaeoclimate records, palaeoecological changes, archaeological histories and human evolution. There is now a wide array of numerical Quaternary dating methods available, though their applicability and accuracy may vary significantly at individual sites depending on a series of factors, including the age range of interest, the types and purity of preserved material, and its association (e.g. taphonomic history, stratigraphic correlation) with the event that is being dated (e.g. Ludwig and Renne, 2000; Grun et al., 2010; Rink and Thompson, 2015; Rixhon et al., 2017). Radiometric methods such as radiocarbon, argon-argon (Ar–Ar) and U-series dating typically offer the greatest analytical precision and are based on relatively standardized analytical procedures. Other techniques such as electron spin resonance (ESR), luminescence, and cosmogenic radionuclide (CRN) dating have not yet reached the same level of standardization, but they nevertheless offer invaluable age constraint across a wide range of sites, depositional contexts and timeframes, particular when the more routinely used and standardized radiometric methods are not applicable.

Remotely sensed data from fluvial systems are extensively used to document historical planform changes. However, geometric and delineation errors inherently associated with these data can result in poor or even misleading interpretation of measured changes, especially rates of channel lateral migration. It is thus imperative to take into account a spatially variable (SV) error affecting the remotely sensed data. In the wake of recent key studies using this SV error as a level of detection, we introduce a new framework to evaluate the significance of measured channel migration. Going beyond linear metrics (i.e. migration vectors between diachronic river centrelines), we assess significance through a channel polygon method yielding a surficial metric (i.e. quantification of eroded, deposited, or eroded-then-deposited surfaces). Our study area is a mid-sized active wandering river: the lower Bruche, a ∼20 m wide tributary of the Rhine in eastern France. Within our four test sub-reaches, the active channel is digitised using diachronic orthophotos (1950 and 1964), and the SV error affecting the data is interpolated with an inverse-distance weighting (IDW) technique. The novelty of our approach arises from then running Monte Carlo (MC) simulations to randomly translate active channels and propagate geometric and delineation errors according to the SV error. This eventually leads to the computation of percentage of uncertainties associated with each of the measured planform changes, which allows us to evaluate the significance of the planform changes. In the lower Bruche, the uncertainty associated with the documented changes ranges from 15.8 % to 52.9 %. Our results show that (i) orthophotos are affected by a significant SV error; (ii) the latter strongly affects the uncertainty of measured changes; and (iii) the significance of changes is dependent on both the magnitude and the shape of the surficial changes. Taking the SV error into account is strongly recommended even in orthorectified aerial photos, especially in the case of mid-sized rivers ( m width) and/or low-amplitude river planform changes ( m2m-1yr-1). In addition to allowing detection of low-magnitude planform changes, our approach is also transferable as we use well-established tools (IDW and MC): this opens new perspectives in the fluvial context (e.g. multi-thread river channels) for robustly assessing surficial channel changes.

Along with the development of “classical” optically stimulated luminescence (OSL) dating, portable luminescence readers have been increasingly employed in a wide breadth of geomorphological settings over the last decade. Portable measurements of bulk samples along depth profiles yield infra-red and optically stimulated luminescence net intensities (IRSL/OSL). The signal build-up depends on (i) the burial duration of the sediment, (ii) the dose rate, (iii) the inherited dose at time of burial, (iv) the mineral composition and (v) the luminescence sensitivity of the minerals. In fluvial landscapes, however, the handful of existing case studies mostly focused on the sole identification of alluvium’s unconformities via luminescence profiling. We argue here that this approach shall go beyond the mere one- (or sometimes two-) dimensional sedimentary screening and steer towards the production of three-dimensional chronostratigraphical information.This study presents the outcomes of a luminescence-profiling approach performed in a wide array of fluvial depositional systems located in the Upper Rhine Graben and the adjacent Vosges Mountains (NE France). They include:modern and historical overbank fines from the main stem (Rhine) and its tributaries (Bruche and Sauer Rivers); palaeomeanders and swale-and-ridge topography (Bruche); Holocene terrace deposits (Bruche); fluvio-glacial deposits (probably) from the Last Glacial Maximum (Cleurie Valley). We thus explore the ability of the reader to measure signals of varying intensities in different morpho-sedimentary units of clearly distinct ages. The results globally show:a consistent pattern of downward increasing OSL/IRSL signal intensities, although some sharp contrasts (i.e., shifts of one order of magnitude in signal intensities) in some sequences could be identified (e.g., Rhine); a larger scatter of OSL/IRSL signal intensities in the sandy fraction than in the silty fraction, probably reflecting the influence of grain size on the signal accumulation (requiring further investigation); the potential of the portable reader as a rapid and efficient tool for tracing historical overbank fine deposition in floodplains.

Underground karst systems have an unique geomorphological relevance for the reconstruction of long-term landscape evolution as it is widely acknowledged that “(…) cave features tend to be preserved far longer than correlative surface features [(e.g., alluvium-mantled terraces in fluvial environments)], which are more susceptible to weathering and erosion” (Audra and Palmer, 2013, p. 187). In this contribution, we thus consider (i) endokarstic fluvial sediments deposited in multi-levels cave systems or networks, which have formed in response to regional base-level changes over long periods of time (typically 105-106 years), and (ii) how to date them. More specifically, we aim at fostering the use of cosmogenic burial dating of cave-deposited clastic sediments to unravel the long-term evolution of fluvial landscapes. The formation of epigenic cave systems and their geomorphological relevance as a marker of long-term river incision is firstly discussed. After a brief presentation of cosmogenic burial dating works and how it can be applied to cave-deposited alluvium, this contribution focuses on how/where to sample within multi-level cave systems and on selecting the sampling material. It afterwards highlights the main drawbacks (analytical and geomorphological uncertainties) associated to this method and presents some strategies to avoid them (if possible). The combination of cosmogenic burial dating with other geochronological tools in the underground realm is also tackled in that respect. Whilst the multi-purpose use of this approach to unravel evolution of fluvial landscapes is briefly reviewed, we focus on the reconstruction of long-term incision rates, including their variation through time, and the drivers of incision. We conclude by a number of useful recommendations to fully benefit from this approach. ReferenceAudra, P., Palmer, A.N., 2013. The vertical dimension of karst: controls of vertical cave pattern. In: Shroder, J. (Editor in chief), Frumkin, A. (Ed.), Treatise on Geomorphology. Academic Press, San Diego, CA, vol. 6, Karst Geomorphology, pp. 186–206.

In parallel to standard optically stimulated luminescence (OSL) dating, portable OSL readers have been increasingly employed in a wide range of geomorphological settings over the last decade. In fluvial landscapes, most of the OSL signal intensities measured by the portable reader were successfully used either to explore bleaching characteristics of river deposits or to rapidly gain new insights into alluvial stratigraphy via luminescence profiling (Munyikwa et al., 2020). However, going beyond the mere one- (or sometimes two-) dimensional sedimentary screening, the use of portable readers shall steer toward the production of three-dimensional chronostratigraphical information. Against this background, the high lateral mobility of the lowermost Bruche reach (directly upstream of Strasbourg), documented at the decadal scale by Jautzy et al. (2022), thus represents a suitable setting to explore the potential of field-based portable luminescence profiling to provide new insights into both lateral and vertical fluvial dynamics.Here, the sampling approach with the portable reader using both blue and infra-red stimulations (BSL and IRSL) is twofold:testing the ability of the reader to measure signals of varying intensities in morpho-sedimentary units of different ages, i.e. an early Holocene terrace, historical palaeomeanders and a modern swale-and-ridge system; investigating the gradual lateral shifting and incision of a single palaeomeander in the floodplain recorded by a succession of palaeochannels and former point bar deposits. Preliminary results (i) show that the older the landform, the higher the BSL/IRSL signal intensity, and highlight (ii) a consistent pattern of downward increasing BSL/IRSL signal intensities in the homogeneous fine-grained upper part of all profiles. However, BSL/IRSL signal intensities measured in the sandy fraction (i.e. lower parts of the alluvial sequences or in the swale-and-ridge system) usually record a larger scatter that requires further investigations. This study underlines the potential of the portable reader as a rapid and efficient tool for tracing historical overbank deposition in floodplains; these results will be complemented soon by standard luminescence dating to constrain sedimentation rates.References:Jautzy, T., Schmitt, L., Rixhon, G., (2022, in press). Historical geomorphological adjustments of an Upper Rhine sub-tributary over the two last centuries (Bruche River, France). Géomorphologie, Relief, Processus et Environnements. Munyikwa, K., Kinnaird, T.C., Sanderson, D.C.W. (2020). The potential of portable luminescence readers in geomorphological investigations: a review. Earth Surface Processes and Landforms DOI: 10.1002/esp.4975.

*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 Vosges Mountains in NE France belong to the belt of Variscan massifs located in the foreland of the Alps. Despite its rather limited extension barely reaching 6000 km², this range of low mountains peaking at ~1425 m presents three contrasting primary characteristics. Firstly, a bipartite N-S subdivision can be achieved based on the geological basement: whereas the southern part, traditionally referred to as the crystalline Vosges, is composed of a mosaic of Palaeozoic rocks, including igneous (mostly intrusive and secondarily extrusive), metamorphic, and sedimentary rocks, the northern part is much more homogeneous given its Triassic sandstone cover (“sandstone Vosges”). Secondly, a clear E-W topographic gradient characterises the mountain range. By contrast to the steep hillslopes and elevation drops regularly exceeding 600 m (sometimes reaching 900-1000 m) between the summits and the valley floors on the eastern side (Alsace; south-western border of the Upper Rhine Graben, URG), the western side exhibits more gently-sloping hillslopes along with a longer extension (Lorraine; eastern border of the Parisian Basin). This results from the sharp E-W contrast in Late Cenozoic tectonic activity between sustained subsidence in the URG to the east and weak rock uplift characterising the Parisian Basin to the west. Finally, the imprint left by Quaternary climatic fluctuations yielded a N-S gradient: whereas the southern part (roughly covering 80-90% of the crystalline Vosges) hosted abundant valley glaciers and still bears traces of significant glacial erosion (cirques and U-shaped valleys), the northern part (mostly the sandstone Vosges) was void of ice cover.In spite of these advantageous characteristics, very little is known about the Quaternary evolution of the massif, in particular regarding the long-term interactions between denudation, lithological control, climatic forcing and tectonic activity. Against this background, this contribution aims to present the first data of long-term, massif-wide denudation. Modern stream sediments from 21 river catchments of different size draining the whole massif were thus sampled for in situ 10Be concentration measurements at the outlet of their mountainous reach. Catchment-wide denudation rates inferred from cosmogenic 10Be will be combined with the analysis of morphometric parameters and structural connectivity resulting from the processing of a high-resolution DEM (5 m). Catchment selection was operated according to the threefold subdivision above: i.e. heterogeneous vs homogenous petrography, tectonically-active eastern side vs “quiescent” western side and glaciated vs unglaciated catchments. We thus test the main hypothesis that the four NE, NW, SE, SW quarters of the Vosges massif shall be characterised by contrasting denudation rates, reflecting the respective role played by the controlling factors on long-term denudation. To our knowledge, this contribution is the first attempt to quantify denudation at the massif scale of a European low 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.*Georges Aumaître, Didier L. Bourlès and Karim Keddadouche

In southern Iberia, the surroundings of the Strait of Gibraltar are known as a crossroad for population movements, cultural exchanges, and trade from Late Prehistory to modern times. However, questions remain about the impact of this historical development on the environment. The settlement of La Silla del Papa, an important hillfort in southern Andalusia (Cádiz), was occupied during the entire Iron Age, replaced by the coastal town Baelo Claudia during Roman times, and re‐occupied during Early Medieval times. As such, La Silla del Papa and its territory represent an ideal location for long‐term studies on human‐environment interactions. Within the framework of the interdisciplinary project “Archeostraits,” geoarchaeological investigations in the surroundings of La Silla del Papa aimed at constraining ecological conditions and human‐environment interactions during the mid‐ and late Holocene and during major human occupation phases. Our results document an early mid‐Holocene marine embayment in the lower floodplain of the Río del Cachón, rapidly turning into a coastal lagoon and later into freshwater‐dominated wetlands. After approximately 2100 BP (c. 150 BC), fluvial and alluvial deposition i600ing a high anthropogenic impact on the local landscape during Roman or post‐Roman times. Palynological results reveal fluctuating agricultural and pastoral activities and distinct periods of landscape opening during the Neolithic and Iron Age., Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659, Agence Nationale de la Recherche http://dx.doi.org/10.13039/501100001665

International audience; Despite a wealth of recent studies dealing with the evolution of the drainage network in the uplifted Ardennes massif (E. Belgium), especially from the Middle Pleistocene onwards, the Ardennian landscape evolution and long-term incision rates in the Meuse catchment remain poorly documented over the whole Plio-Quaternary. Alluvium-filled multilevel cave systems represent a relevant setting to unravel the Late Cenozoic history of regional river incision. We present here a dataset of 26 Al/ 10 Be concentration data obtained from fifteen pebble samples washed into the Chawresse system, one of the largest multi-level cave systems of Belgium, which developed in Devonian limestones of the lower Ourthe Valley, the main Ardennian tributary of the Meuse. The sample collection spans an elevation difference higher than 120 m and their depleted 26Al/10Be ratios yield burial ages ranging from ~0.25 to 3.28 Ma. After critical assessment of our dataset for intra-karstic reworking issues, the most striking outcome of the obtained burial ages is the acceleration by a factor five of the incision rates (from ~30to ~150 m/Ma) during the first half of the Middle Pleistocene. Integrating this incision peak and our pre-burial denudation rates, we then revisit the existing framework of Plio-Quaternary denudation and river incision in the Ardennian Meuse catchment. Whilst our 26Al/10Be concentration data shed new light on the temporal andspatial variability of the local river and hillslope system response to coupled tectonic and climatic forcings, it simultaneously highlights sampling issues and the need for further chronological data.

Geoarchaeological cores were retrieved in the centre of the old “Bahia-Caleta” palaeochannel located between the Erytheia and Cotinusa islands in the former Cadiz archipelago, in present-day southern Spain. The unprecedented coring depth (~ 35–50 m) allowed us to identify the bottom of a Phoenician–Punic and Roman harbour. Located at 20–40 m b.s.l. in the sedimentary sequence, silty sand deposits reveal a deep semi-protected shelter with abundant ceramic and archaeobotanical findings. Based on these new results, the palaeotopography of the islands of Cadiz is reinterpreted, demonstrating the presence of a harbour accessible from the west and possibly from the east until (at least) the Roman period. This major discovery opens meaningful perspectives for archaeological, geomorphological and palaeoenvironmental research.

M. Bartz, L.J. Arnold, M. Demuro, M. Duval, G.E. King, G. Rixhon, C. Alvarez Posada, J.M. Pares, H. Bruckner

Dating the transport/deposition time of supratidal coarse-clast deposits is difficult, limiting their value for inferring frequency-magnitude patterns of high-energy wave events. On Bonaire (Leeward Antilles, Caribbean), these deposits form prominent landforms, and transport by one or several Holocene tsunamis is assumed at least for the largest clasts. Although a large dataset of 14C and electron spin resonance (ESR) ages is available for major coral rubble ridges and ramparts, it is still debated whether these data reflect the timing of major events, and how these datasets are biased by the reworking of coral fragments. As an attempt to overcome the current challenges for dating the dislocation of singular boulders, three distinct dating methods are implemented and compared: (i) 14C dating of boring bivalves attached to the boulders; (ii) 230Th/U dating of post-depositional, secondary calcite flowstone and subaerial microbialites at the underside of the boulders; and (iii) surface exposure dating of overturned boulders via 36Cl concentration measurements in corals. Approaches (ii) and (iii) have never been applied to coastal boulder deposits so far. The three 14C age estimates are older than 40 ka, i.e. most probably beyond the applicability of the method, which is attributed to post-depositional diagenetic processes, shedding doubt on the usefulness of this method in the local context. The remarkably convergent 230Th/U ages, all pointing to the Late Holocene period (1.0–1.6 ka), are minimum ages for the transport event(s). The microbialite sample yields an age of 1.23 ± 0.23 ka and both flowstone samples are in stratigraphic order: the older (onset of carbonate precipitation) and younger flowstone layers yield ages of 1.59 ± 0.03 and 1.23 ± 0.03 ka, respectively. Four coral samples collected from the topside of overturned boulders yielded similar 36Cl concentration measurements. However, the computed ages are affected by large uncertainties, mostly due to the high natural chlorine concentration. After correction for the inherited component and chemical denudation since platform emergence (inducing additional uncertainty), the calculated 36Cl ages cluster between 2.5 ± 1.3 and 3.0 ± 1.4 ka for three of four boulders whilst the fourth one yields an age of 6.1 ± 1.8 ka, probably related to a higher inheritance. These 230Th/U and 36Cl age estimates are coherent with a suggested tsunami age of

Our study focuses on the ephemeral stream deposits of Wadi Selloum to identify phases of morphodynamic stability (pedogenesis) and activity (flooding) in the direct vicinity of the rock shelter of Ifri n'Ammar (NE Morocco). As one of the oldest settlement sites of anatomically modern humans (AMH) in North Africa, Ifri n'Ammar documents periodical occupations since ~ 170 ka. Since the discontinuous settlement record may reflect climate forcing with subsequent landscape changes, we aim at reconstructing the palaeoenvironmental variability recorded in the ephemeral stream deposits. In addition to the use of micromorphological, sedimentological, geochemical and mineralogical methods, the geochronological framework of ephemeral stream deposits was established by the application of different luminescence dating techniques. The deposition ages between 102 ± 8 ka and 1.3 ± 0.2 ka span different morphodynamically stable and active phases. Periods of enhanced aggradation occurred around ~ 100 ka, ~ 75 ka, ~ 55 ka, after the LGM, and during the Holocene, whilst sedimentation ended after ~ 1.3 ka. The Wadi Selloum might be characterised by enhanced flooding during humid phases. Pedogenesis may be used as environmental indicator for more humid climate conditions during MIS 3 (palaeo-Calcisol), the early Holocene (Calcisol) and the late Holocene (Fluvisol). This study thus provides first insights into the palaeoenvironmental changes around the rock shelter of Ifri n'Ammar during the last glacial-interglacial cycle.

A majority of European rivers have been extensively affected by diverse anthropogenic activities, including e.g. channelization, regulation and sediment mining. Against this background, the planimetric analysis based on remotely-sensed data is frequently used to evaluate historical planform changes, eventually leading to quantification of migration rates. However, geometric spatially-variable (SV) error inherently associated with these data can result in poor or even misleading interpretation of measured changes, especially on mid-sized rivers. We therefore address the following issue: What is the impact of spatially-variable error on the quantification of surfacic river planform changes?Our test river corresponds to a 20 m wide meandering sub-tributary of the Upper Rhine, the Lower Bruche. Within four, geomorphologically-diverse sub-reaches, the active channel is digitised using diachronic orthophotos (1950; 1964) and the SV-error affecting the data is interpolated with an Inverse Distance Weighting technique based on an independent set of ground control points. As a second step, the main novelty of our approach consists in running Monte-Carlo (MC) simulations to randomly translate active channels according to the interpolated SV-error. This eventually allows to display the relative margin of error (RME) associated with measured eroded and/or deposited surfaces for each sub-reach through MC simulations, illustrating the confidence level in the respective measurements of our river planform changes.Our results suggest that (i) SV-error strongly affects the significance of measured changes and (ii) the confidence level might be dependent not only on magnitude of changes but also on their shapes. Taking SV-error into account is strongly recommended, regardless of the remotely-sensed data used. This is particularly true for mid-sized rivers and/or low amplitude river planform changes, especially in the aim of their sustainable management and/or restoration. Finally, our methodology is transferrable to different fluvial styles.

Multi-level cave systems record the history of regional river incision in abandoned alluvium-filled phreatic passages which, mimicking fluvial terrace sequences, represent former phases of fluvial base-level stability. In this respect, cosmogenic burial dating of in cave-deposited alluvium (usually via the nuclide pair 26Al/10Be) represents a suitable method to quantify the pace of long-term river incision. Here, we present a dataset of fifteen 26Al/10Be burial ages measured in fluvial pebbles washed into a multi-level cave system developed in Devonian limestone of the uplifted Ardenne massif (eastern Belgium). The large and well-documented Chawresse system is located along the lower Ourthe valley (i.e. the main Ardennian tributary of the Meuse river) and spans altogether an elevation difference exceeding 120 m.The depleted 26Al/10Be ratios measured in four individual caves show two main outcomes. Firstly, computed burial ages ranging from ~0.2 to 3.3 Ma allows highlighting an acceleration by almost one order of magnitude of the incision rates during the first half of the Middle Pleistocene (from ~25 to ~160 m/Ma). Secondly, according to the relative elevation above the present-day floodplain of the sampled material in the Manants cave (per descensum model of speleogenesis generally acknowledged for the regional multi-level cave systems and their abandoned phreatic galleries. In addition to its classical use for inferring long-term incision rates, cosmogenic burial dating can thus contribute to better understand specific and complex speleogenetic evolution.

Timothée Jautzy1,2, Dominik Brill3, Laurent Schmitt1, Gilles Rixhon4Obtaining robust chronological data on landforms and their related deposits together with constraining rates of earth surface processes have constantly represented a major challenge in Quaternary science. In the fluvial context, Optically Stimulated Luminescence (OSL) is particularly well-established but still faces several limitations. It notably requires expensive and time-consuming sample processing and measurement, frequently resulting in a poor spatial and stratigraphical distribution of sampling which may negatively impact the chronological information. To overcome this main limitation, a Portable OSL reader (POSL) has been recently developed (Sanderson & Murphy, 2010). It consists in directly capturing a luminescence signal (counts per seconds) on unprepared sediment samples. This technique is quick and affordable but, unlike conventional OSL, is not able to yield numerical age estimates.This contribution explores POSL capacities to provide useful relative age information on alluvial sediments from the last centuries. We study and compare 42 samples collected from three alluvial profiles located in the floodplain of a gravelly-sandy mid-sized river: the Bruche (i.e. a sub-tributary of the Upper Rhine, France). POSL stimulations, including both blue and infra-red signals, are performed in combination with grain size analysis. We observe (i) an overall increase of signal intensity with increasing depth, (ii) a very good match between blue and IR signals and (iii) no systematic correlation between signal intensity and grain size. Whilst this last point must still be confirmed (i.e. signal intensity does not primarily depend on grain size), our preliminary results positively suggest that POSL is a promising tool to provide a relative chronology for very young alluvial sediments. Furthermore, it may also provide information on geomorphic processes. These results will be combined soon to numerical dating (OSL and 14C) and compared to outcomes of a planimetric analysis to thoroughly reconstruct the historical lateral mobility of the Bruche river.

Although cosmogenic surface exposure dating has substantially progressed over the last decades, dating tsunami- or storm-transported coarse clasts in supralittoral environments still is challenging. The most frequent pitfalls inherently associated to the method, i.e., inheritance and post-depositional erosion/weathering, as well as clast petrography must be carefully taken into account in this setting. Firstly, precisely pinpointing the source area of the clasts and purposely targeting those which experienced complete overturning during transport are prerequisite to overcome many issues related to inheritance. A twofold sampling from the currently exposed and shielded side of the clast is additionally recommended to reliably assess the inherited cosmogenic inventory. Secondly, one should simply avoid sampling clasts displaying significant post-depositional erosion/weathering, unless the latter can be appropriately assessed. Thirdly, high concentrations of stable chlorine usually contained in clasts made of coralline limestone impede a precise dating via 36Cl concentration measurements. Nevertheless, a successful application of cosmogenic surface exposure dating related to a megatsunami event (Cape Verde Islands) together with a list of specific guidelines for a sound sampling of supralittoral clasts are presented. The method indeed is promising as it has the potential to pinpoint the timing of the event, i.e., clast transport and deposition, regardless the considered time frame (Holocene or Pleistocene).

We present the first experimental evaluation of the alpha efficiency value for electron spin resonance (ESR) dating of coarse quartz grains, which is used for the evaluation of the internal and external alpha dose rate components. Based on our results, we recommend the use of an a-value of 0.07 ± 0.01 (1σ) for both the Al and Ti centres. Although we acknowledge that quartz ESR alpha efficiency may be sample dependent, and could also be impacted by other sources of uncertainty, this potential variability is presently impossible to evaluate given the absence of other experimental a-values available in the ESR dating literature. Measured radioactivity of quartz grains from the Moulouya catchment (NE Morocco) provides an internal dose rate in the range of 50–70 µGy/a when using an a-value of 0.07. The use of this empirically derived a-value for the evaluation of the internal and external alpha dose rate has a limited overall impact on the final ESR age results: they change by

Remote-sensed data in the fluvial context are extensively used to document historical planform changes. However, geometric and delineation errors inherently associated with these data can result in poor or even misleading interpretation of measured changes, especially (rates of) channel lateral migration. It is thus fundamental to take a spatially-variable (SV) error affecting remote-sensed data into account. In the wake of recent key studies using this SV-error as a level of detection, we introduce a new framework to evaluate the significance of measured channel migration. Going beyond their linear metric (i.e. migration vectors between diachronic river centrelines), we assess this significance through the channel polygon method yielding a surfacic metric (i.e. quantification of eroded, deposited, or eroded/deposited surfaces). Our study area is an active wandering mid-sized river: the lower Bruche, a ∼ 20 m wide sub-tributary of the Rhine in eastern France. Within our four test sub-reaches, the active channel is digitised using diachronic orthophotos (1950; 1964) and the sub-reach specific SV-error affecting the data is interpolated with an Inverse Distance Weighting (IDW) technique. A main novelty of our approach consists then in running Monte-Carlo (MC) simulations to randomly translate active channels and propagate geometric and delineation errors according to the SV-error. This eventually leads to the production of a Surface of Detection (SoD), which allows evaluating the significance of measured surfacic changes. Putting the SoD into practice in the lower Bruche shows that only 37 % of the total surfacic measured changes are significant. Our results suggest that (i) orthophotos are affected by a significant SV-error, (ii) the latter strongly affects the significance of measured changes and (iii) the significance is strongly dependent on the magnitude of surfacic changes. Taking the SV-error into account is strongly recommended, regardless of the remote-sensed data used (orthophotos or aerial photos), especially in the case of mid-sized rivers (2/yr). We finally insist on the transposability of our approach as we use well-established tools (IDW, MC): this opens new perspectives in the fluvial context (e.g. multi-thread river channels) for robustly assessing surfacic changes.

The Moulouya river has the largest catchment in Morocco and drains an area characterized by active crustal deformation during the Late Cenozoic due to the N–S convergence between the African and Eurasian plates. As yet, its Pleistocene terrace sequence remains poorly documented. Our study focuses on the lowermost reach of the river in north-eastern Morocco, which drains the Zebra-Triffa sedimentary basin directly upstream of the estuary. New field observations, measurements and sedimentological data reveal contrasting fluvial environments on each side of a newly identified, W–E striking thrust zone disrupting the sedimentary basin. On the one hand, long-lasting fluvial aggradation, materialized by 37 m-thick stacked terraces, has occurred in the footwall of the thrust. On the other hand, the hanging wall is characterized by a well-preserved terrace staircase, with three Pleistocene terrace levels. Whilst the identification of this thrust zone question some previous interpretations about the local (hydro-)geology, it is consistent with the statement that most of the Plio-Quaternary deformation in the eastern Rif mountains has concentrated in this region of Morocco. Our new data and interpretations also agree with morphometric indicators showing that the whole Moulouya catchment is at desequilibrium state (i.e. several knickzones in its longitudinal profile), showing several knickzones in its longitudinal profile, is at disequilibrium state. We also suggest that the knickzone in the Beni Snassen gorge, located directly upstream of the Zebra-Triffa sedimentary basin, could (partly) result from a transient fluvial reaction to Late Cenozoic thrusting activity and correlated uplift in the hanging wall.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

The prehistoric site of Ifri n'Ammar is situated in northeastern Morocco, in the northern prolongation of the Middle Atlas Mountains. It is a key location in unravelling the history of anatomically modern humans (AMH) in northern Africa as it reveals Middle and Late Palaeolithic occupation phases since ∼170 ka. Whilst the archaeological sequence within the rock shelter has been well studied, the timing of landscape dynamics around Ifri n'Ammar is still poorly understood. This study therefore aims to establish a detailed chronology of the Wadi Selloum profile at the apron of the shelter, based on optically stimulated luminescence (OSL) dating of ephemeral stream deposits. Coarse-grain quartz was used for single-grain and multiple-grain dating procedures to investigate the luminescence properties of these deposits and to get more accurate age information concerning the phases of human occupation. Continuous wave OSL (CW-OSL) revealed a dominant fast component for all quartz samples. The dose distribution of the uppermost samples showed overdispersion values >25% and significant positive skewness. We identified partial bleaching as the main source of scatter in the equivalent dose (D e ) distribution. The lowermost sample appeared to be close to signal saturation. The shapes of the dose response curve varied widely between aliquots and coarse quartz grains exhibited therefore very different dose saturation behaviours among aliquots. With fully saturated dose response curves (DRCs), meaningful D 0 values were assumed for D e estimation. The eight OSL samples yielded stratigraphically consistent ages ranging from 1.3 ± 0.2 ka to 76 ± 5 ka, thus reaching the Middle Palaeolithic period. Moreover, a pottery shard dated to 7.4 ± 0.6 ka (Early Neolithic period) by thermoluminescence (TL), perfectly matched the Holocene OSL samples extracted at the same depth of the profile. In summary, our results point to fluvial aggradation during OIS 5.1, the late glacial period, and the Holocene.

Along the Chilean–Peruvian coast, numerous archaeological sites associated with shell accumulations provide evidence for the role of coastal environments as a natural corridor for the human occupation of South America. In particular, the semi-arid coastline of northern Central Chile (∼33–27° S) is a key area for investigating the relationship between human occupation history and past climate changes, as palaeoenvironmental studies record important climatic fluctuations in the area throughout the Holocene. In this study, we present a consistent chronology of an anthropogenic shell accumulation layer and an associated palaeosol, found in the stratigraphy of palaeodunes in the Longotoma dune system, northern Central Chile (32°24′ S, 71°23′ W). Infrared Stimulated Luminescence (IRSL) dating of feldspars is used, for the first time in this context, to establish the chronological framework together with radiocarbon dating. The consistency between IRSL- and radiocarbon ages demonstrates the potential of IRSL techniques for studies in comparable settings and at similar time scales, where Optically Stimulated Luminescence (OSL) dating of quartz is problematic. The chronostratigraphical results (i) allow to infer different phases of dune activity as well as an intermittent period of interdunal soil formation at the end of the 6th millennium BP, when the cultural layer and the palaeosol formed; (ii) allocate an age range of ∼4500–3500 a to alluvial deposits below the modern dune corridor; and thereby (iii) give further evidence for the presence of Archaic coastal hunter-gatherer populations in the La Ligua Bay and in northern Central Chile.

Based on a combination of Electron Spin Resonance (ESR) dating of quartz, luminescence dating of K-feldspar and palaeomagnetism, this study presents the first chronostratigraphic framework for the Pleistocene fluvial deposits of the lower Moulouya river in the Triffa basin (NE Morocco). K-feldspar pIRIR225 and pIRIR290 signals of all samples are saturated, suggesting fluvial deposition at least as early as the Middle Pleistocene (∼0.39–0.80 Ma). Consequently, further chronological information was obtained with ESR dating of quartz grains from the ancient Pleistocene fluvial deposits. As for ESR, the multiple centres approach provides equivalent dose values derived from the Al and Ti centres that mostly agree within 1σ-error, suggesting complete signal resetting from the former during fluvial transport. ESR dating results yield Calabrian deposition ages for all river profiles from ∼1.1 to ∼1.5 Ma. These ages are remarkably consistent with the palaeomagnetic results: the occurrence of mostly reversed polarity in the deposits indicates a Matuyama age (>0.78 Ma). While low incision rates in the Triffa basin (0.025 ± 0.003 mm/a) related to thrusting activity during the Calabrian could be inferred, the fluvial record points to an acyclic and discontinuous sedimentation pattern over the last ∼1.3 Ma. It thereby probably rules out climate as the main driver for fluvial aggradation in the lowermost sedimentary basin. At a regional scale, several indicators point to transient fluvial response resulting from major Quaternary tectonic activity along the Beni Snassen gorge, located directly upstream of the investigated basin. We suggest that a capture event at the margin of the uplifting Beni Snassen massif occurred between 1.04 and 1.36 Ma at the latest and subsequently led to the creation of the gorge.

Field geologists and geomorphologists are increasingly looking to numerical modelling to understand landscape change over time, particularly in river catchments. The application of landscape evolution models (LEMs) started with abstract research questions in synthetic landscapes. Now, however, studies using LEMs on real-world catchments are becoming increasingly common. This development has philosophical implications for model specification and evaluation using geological and geomorphological data, besides practical implications for fieldwork targets and strategy. The type of data produced to drive and constrain LEM simulations has very little in common with that used to calibrate and validate models operating over shorter timescales, making a new approach necessary. Here we argue that catchment fieldwork and LEM studies are best synchronized by complementing the Pattern Oriented Modelling (POM) approach of most fluvial LEMs with Pattern Oriented Sampling (POS) fieldwork approaches. POS can embrace a wide range of field data types, without overly increasing the burden of data collection. In our approach, both POM output and POS field data for a specific catchment are used to quantify key characteristics of a catchment. These are then compared to provide an evaluation of the performance of the model. Early identification of these key characteristics should be undertaken to drive focused POS data collection and POM model specification. Once models are evaluated using this POM/POS approach, conclusions drawn from LEM studies can be used with greater confidence to improve understanding of landscape change.

Co-auteur étranger; International audience; Marine conglomerates at high elevation on the flanks of ocean islands are usually interpreted as evidence of mega-tsunamis generated by volcano flank collapses, although their origin is sometimes debated (elevated littorals vs. tsunami). In this review, we introduce case studies of well-documented examples of tsunami conglomerates in Hawaii (Pacific Ocean), the Canary and Cape Verde Islands (Atlantic Ocean), and Mauritius Island (Indian Ocean). Other less-documented marine conglomerates are also presented as tsunami candidates. Then, we build a comprehensive picture of the general characteristics of these conglomerates and the different methods that can be applied to date them. Different perspectives of research are proposed, especially on the use of tsunami conglomerates as proxies for better constraining numerical models of ocean island flank collapses and associated tsunamis. We also discuss the possible links between volcano growth, flank instability, and climate.

As a response to Late Cenozoic tectonic uplift of the Ardenne massif, the Meuse River and its drainage system deeply incised the landscapes of Southern Belgium. Well-preserved terrace staircases flanking the main Ardennian valleys show a break at the height of the Main Terrace Complex, whose younger level (YMT) marks the transition towards the steep-sided lower part of valley transverse profiles. Numerical 10Be/26Al dates obtained for the YMT in various places along the lower Meuse—lower Ourthe—Ambleve line yield an age around 620 ka for the pulse of tectonic uplift responsible for increased incision rates and fast valley deepening. They also show diachronic abandonment of the YMT, indicating that post-YMT erosion invaded the drainage system through the migration of knickpoints originating in the ~20 m base level lowering initially created at the margin of the en-bloc uplifted region. A study of knickpoints in modern long profiles of Ardennian rivers fully confirms this view. Assimilation of the new data imposes a revised model be proposed for river incision in the Ardenne. Integrating the climatic control with the various modes of tectonic control over river incision, this conceptual model offers a sounder frame of the Quaternary river system evolution in the Ardenne, also explaining observed cases of stream piracy. Basin average denudation rates published for the Ardenne are also briefly compared with valley incision rates.

This paper reviews the diversity of relationships between river evolution and karstogenesis. It also underlines the fundamental role of numerical dating methods (e.g. cosmogenic nuclides) applied to sedimentary sequences in tiered cave passages as they have provided new insights into these complex interactions. Although karst terrain is widespread worldwide, we focus on European karst catchments, where the sedimentary records are especially well preserved. We review the recent dating of fluvial sediments and speleothems, to examine the timing of karstification, incision and deposition in cave levels. The most complete alluvial records occur in tectonically uplifted high mountains where some of the oldest sediment fills date to the Miocene. Evidence indicates that not only uplift, but also climatic conditions and fluvial dynamics (e.g. knickpoint retreat, increased channel flow and/or sediment load, and stream piracies) can play a major role in speleogenesis and geomorphological evolution. In evaporite rocks, speleogenesis is characterized by rapid dissolution and subsidence. In European catchments, gypsum cave development largely occurred during cold climate periods, while limestone caves formed during warm interglacial or interstadial phases. Our synthesis is used to propose four models of fluvial and karst evolution, and highlight perspectives for further research.

It is still disputed whether very old archaeological and palaeontological remains found in the Belle-Roche palaeocave (eastern Belgium) pertain to the Early (∼1 Ma) or Middle (∼0.5 Ma) Pleistocene. Here, in situ-produced cosmogenic 10Be concentrations from a depth profile in nearby sediments of the Belle-Roche terrace (Ambleve Main Terrace level) are used as an indirect solution of this chronological issue. The distribution of 10Be concentrations in the upper 3 m of this profile displays the theoretically expected exponential decrease with depth. Assuming a single exposure episode, we obtain a best fit age of 222.5±31 ka for the time of terrace abandonment. However, below 3 m, the 10Be concentrations show a marked progressive increase with depth. This distinctive cosmogenic signal is interpreted as the result of slow aggradation of the fluvial deposits over a lengthy interval. Modelling of the whole profile thus suggests that the onset of the terrace formation occurred at around 550 ka, with a sediment accumulation rate of ∼20 mm ka−1. Based on two slightly different reconstructions of the geomorphic evolution of the area and a discussion of the temporal link between the cave and Main Terrace levels, we conclude that the fossil-bearing layers in the palaeokarst pertain most probably to MIS 14–13, or possibly MIS 12–11. This age estimate for the large mammal association identified in the Belle-Roche palaeokarst and the attribution to MIS 14–13 of a similar fauna found in the lowermost fossiliferous layers of the Caune de l'Arago (Tautavel) are in mutual support. Our results therefore confirm the status of the Belle-Roche site as a reference site for the Cromerian mammal association in NW Europe.

Les vallées de la Moselle et de la Meurthe, un de ses principaux affluents, se caractérisent par la présence de terrasses alluviales bien préservées. Alors que les terrasses associées aux derniers cycles glaciaires-interglaciaires ont récemment été datées par luminescence (datations OSL), l’âge des terrasses alluviales plus anciennes reste sujet à discussion en raison du manque de datation absolue. Cet article présente les résultats de datations par résonance électronique de spin (ESR) portant sur la terrasse alluviale Me4 (+30 m d’altitude relative) de la Meurthe, sur la terrasse M7 (+70 m) de la vallée de la Moselle à la frontière franco-allemande, ainsi que sur le complexe des terrasses dites « principales » qui jalonnent la vallée allemande de la Moselle dans sa traversée du Massif schisteux rhénan à une altitude absolue constante d’environ 260 m entre Trèves et Cochem, soit à des altitudes relatives comprises entre 130 et 180 m. Les datations de la terrasse Me4 permettent d’attribuer sa mise en place à la seconde moitié du Pléistocène moyen. Bien qu’elles ne permettent pas de corréler la formation de cette terrasse alluviale à un stade isotopique spécifique en raison de marges d’erreur significatives, elles semblent toutefois cohérentes avec les âges par luminescence optiquement stimulée (OSL) obtenus pour les terrasses plus récentes. En dépit d’âges anormalement jeunes obtenus pour la terrasse M7 ainsi que pour deux sites de terrasse principale, les deux autres datations réalisées dans ce complexe suggèrent des âges supérieurs à 1 Ma, cohérents avec les taux d’incision observés pour les terrasses plus récentes. Ce résultat remettrait en question l’âge communément admis de ~800 ka pour la mise en place de l’avant-dernière terrasse principale dans la vallée de la Moselle. The valleys of the River Moselle and one of its main tributaries, the Meurthe, are characterized by well-preserved fluvial terrace staircases. Whereas the younger terraces, attributed to recent glacial-interglacial cycles, have been dated by Optically Stimulated Luminescence (OSL), the chronology of the older terraces remains questionable due to the lack of absolute dating. Electron Spin Resonance (ESR) dating was therefore undertaken on Meurthe terrace Me4 (+30 m of relative elevation), Moselle terrace M7 (+70 m) near the French–German border, and the so-called Main Terrace Complex of the German Moselle valley in the Rhenish massif. These main terraces are characterized by the constant absolute elevation of their base (~260 m a.s.l.) along the ~150 km-long reach between Trier and Cochem, implying relative elevations ranging from to 130 to 180 m. The results from terrace Me4 point to its formation during the second part of the Middle Pleistocene, a time span consistent with the Optically Stimulated Luminescence (OSL) ages of the younger terraces. Unfortunately, deposition cannot be allocated to a specific MIS due to the significant age uncertainties. Although abnormally young ages were obtained for the M7 terrace and for two sites in the Main Terrace Complex, two further sites belonging to this complex point to ages older than 1 Ma. While this result is consistent with the incision rates observed for the younger terraces, it would also refute the commonly assumed age of 800 ka allocated to the penultimate terrace within the complex.

Over the last three decades, theoretical and technical developments have considerably fostered and intensified the use of terrestrial (or in situ) cosmogenic nuclides as a geochronometer in a variety of environments at the Earth’s surface for the Late Cenozoic. These dating methods, including both surface exposure and burial dating, also significantly benefited to fluvial geomorphology. They opened new dating horizons for different kinds of fluvial archives at distinct time scales and thereby provided new insights into previously unanswered questions. This contribution aims at providing a concise (but not exhaustive) overview of these dating applications in a variety of fluvial environments (e.g. river terraces, alluvial fans, in cave-deposited alluvium). Therefore, it briefly presents the fundamental principles of both surface exposure and burial dating, together with a clear statement of the main methodological issues arising from the use of these methods in fluvial contexts. For each dating applications, key information about sampling procedures in the field and representative case studies are also provided.

During the last twenty years, several technical developments have considerably intensified the use of numerical dating methods for the Quaternary. The study of fluvial archives has greatly benefited from these enhancements, opening new dating horizons for a range of archives at distinct time scales and thereby providing new insights into previously unanswered questions. In this contribution, we separately present the state of the art of five numerical dating methods that are frequently used in the fluvial context: radiocarbon, Luminescence, Electron Spin Resonance (ESR), 230Th/U and terrestrial cosmogenic nuclides (TCN) dating. We focus on the major recent developments for each technique that are most relevant for new dating applications in diverse fluvial environments and on explaining these for non-specialists. Therefore, essential information and precautions about sampling strategies in the field and/or laboratory procedures are provided. For each method, new and important implications for chronological reconstructions of Quaternary fluvial landscapes are discussed and, where necessary, exemplified by key case studies. A clear statement of the current technical limitations of these methods is included and forthcoming developments, which might possibly open new horizons for dating fluvial archives in the near future, are summarised.

It is still debated whether the primary control on the middle Pleistocene denudation of the uplifted Ardennes massif (western Europe) is tectonic or climatic. Here, based on geomorphological observations, we calculate the amount of river incision and interfluve denudation in the Meuse basin upstream of Maastricht since 0·7 Ma and we show that the main response to tectonic forcing was incision. This allows us to provide first-order estimates of the tectonic and climatic contributions to the denudation of the Ardennes. From a dataset of 71 remnants of a terrace level dated ∼0·7 Ma, we first derive a basin-scale functional relationship linking incision with distances to the regional base level (Lc) and to the source (Ls) in the Ourthe basin (pertaining to the Ardennian part of the Meuse basin). Expressed as I = I0*(1 – a*Lcb/Lsc), I0 being the incision measured at the basin outlet, this relationship calculates that river incision has removed 84 km3 of rock in the Meuse basin upstream of Maastricht since 0·7 Ma. In the same time, 292 km3 were eroded from the interfluves. A comparison of these volumes shows that the tectonically forced river incision accounts for ∼22% of the total post-0·7 Ma denudation. Furthermore, the mean denudation rate corresponding to our geomorphological estimate of the overall denudation in the Meuse basin since 0·7 Ma amounts to 27 mm/ky, a figure significantly lower than the ∼40 mm/ky mean rate derived from 10Be studies of terrace deposits of the Meuse (Schaller et al., 2004). This suggests that, taken as a basin average, the 10Be-derived rate is overestimated, probably due to an overrepresentation of the erosion products of the rapidly incising valleys in the alluvial deposits. Copyright © 2009 John Wiley & Sons, Ltd.

Fluvial terraces are a powerful tool for unraveling the combined tectonic and climatic conditions that controlled, directly or indirectly, the Quaternary incision of rivers. Terrace long profiles are usually retrieved from sparse traces of ancient floodplains preserved in the present topography. However, when these traces classically collected from topographic maps, aerial photographs, and field analyses are too few, the inferred profiles may be questionable. Yet the now available high quality and high resolution digital elevation models (DEMs) offer an opportunity to increase greatly the quantity of information usable to reconstruct terrace profiles. Therefore, the purpose of this study was to develop a new DEM-based method of terrace recognition in order to create a larger database and better constrain the profile reconstruction. Moreover, particular procedures of image and numerical processing were defined to fully automate the analysis. Basically, our method relies on the production of bivariate scatter plots depicting the relation between slope and relative altitude (i.e., the altitude above the current alluvial plain) for all pixels of successive sections of the valley. For each scatter plot, the curve of the lowest slope values observed at every relative altitude is smoothed and its minima are assumed to locate the altitudes of the “terrace” elements preserved in the section. We successfully tested this method in the Vesdre valley, incised in the NE Ardenne massif (E Belgium), notably identifying fault deformation of the profiles. The main advantages of our approach are its objectivity, exhaustiveness, and rapidity, allowing fast and coherent analysis of many rivers over extended regions.

International audience

Coastal geomorphology and the stratigraphy of coastal geoarchives record past coastal and fluctuations of coastal environments. In addition, these archives potentially store traces of past extreme events such as earthquakes and tsunamis, severe storms, and major flfl oodings of the coastal hinterland, e.g. due to El Niño conditions. Studying their characteristics may thus improve the knowledge of past frequency and magnitude patterns of such extreme events. For instance, large scaled spatial information about past earthquakes is needed for the understanding and estimation of seismo-tectonic processes. Misinterpretations in the size of preceding earthquakes may lead to incorrect strain balance estimations along megathrusts. Thus, fundamental research on the occurrence of past earthquakes is needed, which can be reflected in sudden or long-term coastal changes. Using sedimentological, geomorphological and microfaunal evidence, coeval geomorphodynamic and palaeoenvironmental changes at four different locations between 29° 50′ and 32° 20′ S in Central Chile were identififi ed in estuary systems, coastal swamps and coastal plains. The results may represent possible indirect evidence for palaeoseismicity, affecting the coastal system by vertical tectonic movements. Changes of coastline elevation, morphodynamic activity and/or coastal environments, as well as the formation of a liquefaction layer took place during the last c. 400 years. Moreover, major flfl ooding events related to strong El Niño conditions are assumed to have influenced the coastal stratigraphy by depositing high energy fluvial deposits. Our results suggest that the coastal environment, geomorphology and stratigraphy are considerably inflfl uenced by tectonic processes in the study area; a relation of the presented fifi ndings to the 1730 Great Valparaíso Earthquake is assumed. In general, the findings may encourage the implementation of comparable detailed studies, which may ultimately contribute to a better understanding of the Holocene coastal evolution and its relation to palaeoseismicity in Central Chile.

While climatic models of valley downcutting discuss the origin of terrace staircases in valleys of middle Europe within the frame of alternating cold and temperate periods of the Quaternary, other models, starting from a base level fall imposed by an initial tectonic signal, describe the response of the drainage network mainly as the propagation of an erosion wave from the place of base level fall (the margin of the uplifted region) toward the headwaters, the two types of model being rarely confronted. In the Ardennes (West Europe), cosmogenic10Be and26Al ages have recently been calculated for the abandonment of the Younger Main Terrace (YMT) level, a prominent feature at mid-height of the valleysides marking the starting point of the mid-Pleistocene phase of deep river incision in the massif. These ages show that the terrace has been abandoned diachronically as the result of a migrating erosion wave that started at 0.73 Ma in the Meuse catchment just north of the massif, soon entered the latter, and is still visible in the current long profiles of the Ardennian Ourthe tributaries as knickpoints disturbing their upper reaches. At first glance, these new findings are incompatible with the common belief that the terraces of the Ardennian rivers were generated by a climatically triggered stepwise general incision of the river profiles. However, several details of the terrace staircases (larger than average vertical spacing between the YMT and the next younger terrace, varying number of post-YMT terraces in trunk stream, tributaries and subtributaries) show that a combination of the climatic and tectonic models of river incision is able to satisfactorily account for all available data. The cosmogenic ages of the YMT also point out a particular behaviour of the migrating knickpoints, which apparently propagated on average more slowly in the main rivers than in the tributaries, in contradiction with the relation that makes knickpoint celerity depend directly on drainage area. We tentatively suggest a process accounting for such anomalies in migration rates.