Search

To understand the physical mechanisms of the spattering and denudation phenomena in the laser powder bed fusion process, we develop a multiphase flow model by bi-directionally coupling the discrete element method and finite volume method, where the exchanges of both momentum and energy between the powder particles and gases are incorporated. It is the first time that the dynamic behaviours of both the gas phase and powder particles during the spattering and denudation phenomena are reproduced in computational modelling, which agree well with the published experimental observation. The metal vapour spouts out and decelerates sharply along the jetting direction while expanding radially, which induces remarkable vortex flows of the ambient gas. With comparative simulation cases, the vapour jetting and the consequent vortex flow are demonstrated to be dominant in the spattering and denudation phenomena, and the thermal buoyancy effect is proved to be negligible. Moreover, the influence of the jetting angle is investigated: no remarkable effect within the range of 60° - 120°; while larger than 150°, the accumulation zone is eliminated leading to a completely exposed denudation zone.

Este trabalho objetiva compreender o quadro geomorfológico da porção terminal do baixo curso do rio Paraíba do Norte – PB, mediante a classificação e diferenciação cartográfica das unidades de relevos presentes na área de estudo. Adotou-se para o presente trabalho a escala de 1:25.000 que permitiu identificar os seis táxons propostos na metodologia de Ross (1992). O estudo possibilitou conhecer com maior nível de detalhe a geometria e os padrões de relevo existentes na região, onde se destacaram áreas de acumulação e denudação, dentre elas: planícies marinhas, fluviais e flúvio marinhas, formas de terraços e vertentes, falésias, praias, barras arenosas, bancos de areia, paleolinhas de praias, recifes, lagoas antropogênicas, lagunas, dolinas e glacis de sedimentação, além de formas de relevos tabulares e convexos que modelam os tabuleiros litorâneos da costa paraibana.

Cirque erosion contributes significantly to mountain denudation and is a key element of glaciated mountain topography. Despite long-standing efforts, rates of rockwall retreat and the proportional contributions of low-, mid- and high-magnitude rockfalls have remained poorly constrained. Here, a unique, terrestrial-lidar-derived rockfall inventory (2011–2017) of two glaciated cirques in the Hohe Tauern range, Central Alps, Austria, is analysed. The mean cirque wall retreat rate of 1.9 mm a−1 ranks in the top range of reported values and is mainly driven by enhanced rockfall from the lowermost, freshly deglaciated rockwall sections. Retreat rates are significantly elevated over decades subsequent to glacier downwasting. Elongated cirque morphology and recorded cirque wall retreat rates indicate headward erosion is clearly outpacing lateral erosion, most likely due to the cataclinal backwalls, which are prone to large dip-slope failures. The rockfall magnitude–frequency distribution – the first such distribution derived for deglaciating cirques – follows a distinct negative power law over 4 orders of magnitude. Magnitude–frequency distributions in glacier-proximal and glacier-distal rockwall sections differ significantly due to an increased occurrence of large rockfalls in recently deglaciated areas. In this paper, the second of two companion pieces, we show how recent climate warming shapes glacial landforms, controls spatiotemporal rockfall variation in glacial environments and indicates a transient signal with decadal-scale exhaustion of rockfall activity immediately following deglaciation crucial for future hazard assessments.

Large-scale gas accumulation areas in large oil-gas basins in central and Western China have multiple special accumulation mechanisms and different accumulation effects. Based on the geological theory and method of natural gas reservoir formation, this study examined the regional geological and structural background, formation burial evolution, basic characteristics of gas reservoirs, and fluid geology and geochemistry of typical petroliferous basins. The results show that the geological processes such as structural pumping, mudstone water absorption, water-soluble gas degasification and fluid sequestration caused by uplift and denudation since Himalayan stage all can form large-scale gas accumulation and different geological effects of gas accumulation. For example, the large-scale structural pumping effect and fluid sequestration effect are conducive to the occurrence of regional ultra-high pressure fluid and the formation of large-scale ultra-high pressure gas field; mudstone water absorption effect in the formation with low thickness ratio of sandstone to formation is conducive to the development of regional low-pressure and water free gas reservoir; the water-soluble gas degasification effect in large-scale thick sandstone can not only form large-scale natural gas accumulation; moreover, the degasification of water-soluble gas produced by the lateral migration of formation water will produce regional and regular isotopic fractionation effect of natural gas, that is, the farther the migration distance of water-soluble gas is, the heavier the carbon isotopic composition of methane formed by the accumulation.

Tectonically active high relief areas are proposed to have a substantial impact on climate regulation throughout the Cenozoic. Here, we present lithium (Li) isotope data of the dissolved load and suspended particulate material from the basins of the Yalong River and the Jinsha River, which drain the high-relief borders of the eastern Tibetan Plateau and constitute the headwaters of the Yangtze River. Dissolved δ7Li values are relatively low and constant in the Jinsha River mainstream (+6.8‰ to +9.7‰) compared to the higher and downstream increasing values in the Yalong River mainstream (+10.8‰ to +17.5‰). Furthermore, dissolved δ7Li values in the major tributaries of the Jinsha and Yalong River are highly variable and increase downstream from +11.4‰ to +29.4‰ and from +9.0‰ to +23.6‰, respectively. Robust correlations between Li, Na, and Cl concentrations identify that evaporite dissolution in the uppermost headwaters of the Jinsha River basin controls the Li budget and riverine δ7Li values of the mainstream and has a significant impact on dissolved Li in the Yangtze River. In contrast to the Jinsha River mainstream, dissolved Li in the Yalong River mainstream and the Jinsha and Yalong River tributaries are dominantly derived from the dissolution of silicates. δ7Li variations in the Yalong River basin and the Jinsha tributaries reflect little Li uptake by clays in the upper reaches and more Li uptake by clays in the lower reaches of the river basins. SWR/D ratios (where SWR is the chemical silicate weathering rate, and D is the total denudation rate) highlight an intermediate silicate weathering intensity under a kinetically limited weathering regime for the study area. However, positive correlations between dissolved δ7Li value and silicate weathering intensity proxies (such as Si/(Nasil + K) and K/(Nasil + K)) indicate an increasing weathering intensity downstream. A positive correlation between dissolved δ7Li values and the annual precipitation and a negative one between δ7Li values and elevation indicates that larger annual precipitation under a flattening relief results in a stronger silicate weathering intensity, thus, more Li uptake in clays and higher riverine δ7Li values in the lower reaches. Compared to the lower reaches of Yangtze River basin (∼+20‰), lower dissolved δ7Li values in its headwater of this study suggest that the increase in δ7Li of seawater over the Cenozoic is influenced by weathering in floodplains that developed due to erosion of high mountains, rather than weathering of mountain belts itself. Combined with silicate weathering rates of the eastern border of the Tibetan Plateau, the highest riverine δ7Li values in its catchments come along with the highest silicate weathering rates and high CO2 consumption, suggesting that a more elevated topography may have an important role in the drawdown of CO2 during the Cenozoic.

The runoff-sediment relationship in the Yellow River Basin of China is still grim. People pay more and more attention to non-point source (NPS) pollution caused by surface pollutants migrating into the receiving water body with rainfall runoff. The particulate load of pollutants adsorbed in the soil and sediment by erosion and denudation and migration into water is also quite serious. It is necessary to deeply analyze the quantitative relationship between particulate nitrogen and phosphorus (PN/PP) load and soil loss. The soil erosion estimation of different administrative units in the study basin is obtained by the revised universal soil loss equation (RUSLE). The spatial distribution and the variation characteristics at different slopes and different land use of PN/PP load are discussed. An empirical equation of particulate organic load is used to calculate the PN/PP load. The results show that the multi-annual average erosion modulus of the basin is 358.33 t/(km2∙a); the multi-annual average soil erosion reaches 9.62 million tons. The PN/PP load caused by soil loss reaches 11,107.1 t and 7909.3 t, and the export coefficients are 4.13 kg/hm2 and 2.94 kg/hm2, respectively. Spatial distribution of the PN/PP load is in step with the soil erosion distribution. Soil erosion is prone to occur in the region under the slope of 8 ~ 25°, the NPS load of PN/PP are relatively large, and the average export coefficients of PN/PP are 7.17 kg/hm2 and 5.06 kg/hm2. With the increase of the slope, the PN/PP load export coefficient increases first and then decreases. Agricultural land (AGRL), forest land (FRST), and pasture (PAST) are the land use types that contribute the most to the PN/PP load and soil erosion, and the average export coefficients of PN/PP are 4.54 kg/hm2 and 3.23 kg/hm2, respectively. The variability of natural elements, the unevenness and heterogeneity of spatial distribution, and the heavy involvement of human activities will have a conspicuous impact on the soil erosion and NPS pollution processes in the basin. The research on the influence of single factor and combined factors on NPS pollution process can be strengthen and provides scientific theoretical basis for formulating reasonable and efficient water and soil conservation measures and NPS pollution control scheme, so as to achieve effective control and scientific management of environment pollution.

The study indicates the viability of geographic information system and remote sensing data for the analysis as well as estimation of the stage and the rate of erosional processes in a Himalayan watershed for improved planning and management. The Gaj watershed lies in the outer Himalayan region of Himachal Pradesh, India, which has been characterized in to nine sub-watersheds for studying the geomorphological evolution of each separately for comparative assessment irrespective of any scale issue. The method involves the use of 30 m Cartosat (digital elevation model) for operative and time-saving data extraction of morphometric and hypsometric parameters. The estimated hypsometric integral values and the shape of the hypsometric curves reveal varying degree of erosional stages of the sub-watersheds demanding attention over the denudation activities. The results have helped in the qualitative discussions and prioritizing the sub-watershed for sustainable soil–water conservation and management, which can be useful for controlling the erosional activities at right locations in the study area.

The Huizhou Movement refers to the Middle Eocene tectonic transition from the early to the late Wenchang Rifting stage (about 43 Ma ago) in the Pearl River Mouth Basin. Based on seismic reflection, drilling, logging and geological data, fault characteristic analysis, denudation thickness recovery, magmatism statistics, regional tectonic dynamics comparison and other methods are used to reveal the characteristics, properties and dynamic mechanism of the Huizhou Movement. The Huizhou Movement mainly shows the North-South transition of rifting and the migration along the faults, basement uplift, magmatic diapir and stratigraphic denudation. It is believed that the Huizhou Movement is a comprehensive reflection of plate interaction and lithospheric thinning process in the Pearl River Mouth Basin, which is closely related to the transition of lithosphere from initial rifting to rapid thinning, the India-Eurasia hard collision and the change of subduction direction of the Pacific plate. The Huizhou Movement has significant influence and control on the Paleogene hydrocarbon-generating sags and the development of hydrocarbon source rocks, sedimentary system and deep high-quality reservoir, hydrocarbon migration and accumulation in the Pearl River Mouth Basin.

Chemical weathering in the Himalayan river basins is among the highest in the world and has received vast research attention related to past climate change. Many early estimates of chemical weathering are based on a small number of water property data that ignore those spatial and seasonal variations. Therefore, this study analyzed spatial and seasonal variations in chemical weathering in the Mekong Basin, where the geology, climate, and hydrologic cycle of the basin vary significantly from the lower to upper reaches and from dry to rainy seasons. We separately estimated the origins of dissolved elements and potential CO2 consumption rates using the numerous chemical compositions of river water throughout the entire basin and in both seasons. The CO2 consumption rate in the rainy season is three to five times that in the dry season that may be due to the high temperature and precipitation. Despite the low temperatures and dryness of the upper and middle basins, the CO2 consumption rate is approximately twice that in the lower reaches; this can be attributed to active physical denudation in steep mountainous areas which increases the surface area for water–rock interactions. The total CO2 consumption obtained by combining each season and basin was 48‒70 × 109 mol/a and 148‒159 × 109 mol/a for silicate and carbonate weathering, respectively, which are almost half the values of previous estimates. Our results suggest that seasonally and spatially separated evaluations are important for generating estimates of chemical weathering in large Himalayan rivers.

Karst aquifers represent the most important renewable sources of drinking water. Because anthropogenic influences threaten the integrity of karst aquifers, it is important to determine the soil erosion and karst denudation rates. In order to study the complex signs of degradation processes of the karst, a paleodoline (paleo-polje) was selected near to the county seat Veszprém, Hungary. It was found that gamma radiation measurements can be a useful tool to detect the level of soil erosion since the low gamma radiation indicates the surface proximity of the carbonate bedrock. The level of gamma radiation also predicts the potential agricultural usability of a site. Both the patterns of contamination and the erosion attack zone are strongly defined by the relief. The gullies and the deepest parts of the karstic landscape are the traps of organic materials and pollutants. The amounts of 40K and its decay products originate from the covering sediment and negatively correlate with the soil depth. In the case of covered karsts, the measuring of the concentration of radionuclides and field gamma-ray dose measurement together can characterize the general horizontal and vertical trends of soil erosion, the potential land use, and the vegetation.

[Abstract The influence of climate on mountain denudation has been the topic of an intense debate for two decades. This debate partly arises from the covariation of rainfall and topography during the growth of mountain ranges, both of which influence denudation. However, the denudational response of this co‐evolution is poorly understood. Here, we use a landscape evolution model where the rainfall evolves according to a prescribed rainfall–elevation relationship. This relationship is a bell curve defined by a rainfall base level, a rainfall maximum and a width around the rainfall peak elevation. This is a first‐order model that fits a large range of orographic rainfall data at the ca. 1‐km spatial scale. We carried out simulations of an uplifting block with an alluvial apron, starting from an initially horizontal surface, and testing different rainfall–elevation relationships. We find that the denudation history is different from that with constant rainfall models. The results essentially depend on the ratio between the final steady‐state summit elevation Hss and the prescribed rainfall peak elevation Hp. This ratio is hard to predict because it depends on the transient coupling of rainfall and elevation. We identified three types of results according to Hss/Hp. If Hss/Hp > 4 (Type I), the denudation rates peak when the summits reach values close to Hp. If Hss/Hp > 1.5 and < 4 (Type II), the denudation is strongly accelerated when the elevation of the summits approaches Hp, and then the denudation increases slowly towards the uplift rate. If Hss/Hp < 1.5 (Type III), the denudation evolution is similar to situations with constant and homogeneous rainfall. In the Type I and II experiments, the mountain top is subjected to aridification once the summits have passed through Hp. To adapt to this reduced rainfall, the slopes increase. This can lead to a paradoxical situation where the mountain relief increases faster, whereas the denudation increases more slowly. The development of orographic precipitation may thus favour the stability of the mean denudation rate in a rising mountain. Despite the model limitations, including a constant rainfall–elevation relationship, our study suggests that the “classical” exponential increase in the denudation rate predicted by constant rainfall models is not the common case. Instead, the common case involves pulses and acceleration of the denudation even in the absence of uplift or global climate variations., The development of a precipitation peak at some elevation within mountain catchments appears to be a crucial factor that controls the denudation and topographic evolutions of a mountain. If the precipitation peak is located at low or medium elevation when the mountain has reached a dynamic equilibrium, the model predicts that denudation has strongly accelerated (b) in the early times of the mountain uplift, or even passed by a maximum resulting in a pulse of sediment outflux to basins (a). If the precipitation rate does not have a maximum in the mountain, it can be deduced that the denudation has not evolved differently from cases where the precipitation rate is constant (c). These results can be used to re‐examine the interpretation of sediment flux variations in real cases based on the current distribution of precipitation rates with altitude in mountain ranges. ]

Sand used as aggregates for construction and other civil engineering works come from two types of artisanal mining in the western part of Cameroon. Sand is sourced from the river or open pit quarries suggesting their alluvial and elluvial origin. The suitability of sand used for civil engineering works in Western Cameroon was assessed. The study found that sand from both river and quarry sources are of a poor quality for use in construction, due to the fine grained nature of the materials and the presence of clay, which can shrink and swell. In addition, these open pit quarries creates negative consequences on the environment such as the loss of vegetation, land incision and denudation, soil and landscape degradation leading to the total disappearance of some mountains. Then, existing law and regulation on sand mining cannot protect the environment in Cameroon. The geoscience and geotechnical knowledge on these practices are crucial when enacting any appropriate legislation for the environmental protection in this sector.

Topographic uplift of the southern African Plateau is commonly attributed to mantle causes, but the links between mantle processes, uplift, and erosion patterns are not necessarily straightforward. We acquired apatite (U-Th)/He (AHe) dates from eight kimberlite and basement samples from the lower reaches of the large westward-draining Orange River system with the goal of evaluating the roles of lithospheric modification and river incision on the erosion history here. Average AHe dates range from 79 to 118 Ma and thermal history models suggest that most samples are consistent with a main erosion phase at ca. 120–100 Ma, with some variability across the region indicating a complex erosion history. Major erosion overlaps with the timing of strong lithospheric thermochemical modification as recorded in xenoliths from the studied kimberlites, but the denudation pattern does not mimic the northward progression of lithospheric alteration across the study region. We attribute this area’s denudation history to a combination of mantle effects, rifting, establishment of the Orange River outlet at its current location, and later faulting. When considering these results with other kimberlite-derived surface histories from an ∼1000-km-long E-W transect across the plateau, an eastward-younging trend in denudation is evident. The interplay of mantle processes and the shape of the large, west-draining Orange River basin likely control this first order-pattern.

The restoration of the denudation thickness is the basis for quantitatively analyzing the basin burial history, thermal evolution history and hydrocarbon accumulation conditions. The well data is not sufficient to do this in the southern Lishui Sag with only 5 wells, so the new, high-quality three-dimensional (3D) seismic data is essential. The methods employed to determine the eroded thicknesses of key unconformities in the study area are the mudstone acoustic time difference (AC) method, vitrinite reflectance (Ro%) method and stratigraphic trend comparison method. On the basis of the structural evolution, the restoration of the paleogeomorphology is carried out. The results show that the Wenzhou formation (E2w) in the entire study area has been all denuded. The denudation thickness is in the range of 0-550 m, and decreases gradually from west, thicker than 200 m, to east. The erosion of the upper Lingfeng formation (E11) are mainly occurred in the N-P-1 structural trap (N-P-1), the N-P-2 structural trap (N-P-2) and the N-P-3 structural trap (N-P-3). Among them, the eroded area in N-P-1 (near well S-1) and N-P-2 is 200-230km2, and the denudation thickness is 0-600m, which increases from south to north, even up to 200-400m in the region around well S-1. In N-P-3, the extent of denudation is 30-50 km2, and the denudation thickness is 0-400m. In the early stage of the upper E11, one north-south strike slip fault began to develop in the southern study area. Affected by this fault, the southern Lingfeng bulge was offset, forming a gorge, and the eastern and western sides of the concave belt connected to each other. On the basis of the paleo-geomorphological characteristics, it is shown that the sedimentary center of the west subsag began to migrate to the south.

The study area is located on a tectonic belt shaped by the segments of Bitlis Zagros Suture Zone in the Eastern Anatolia Compression Regime Region, which is one of the morphotectonic regions of Anatolia. At the same time, the main structure of the area to the east of the Toros Orogen Belt consists of a curved structure extending in NW-SE direction. However, the dislocations of the Alp Orogenesis, which were exacerbated by the paroxysmal phases in the post-Miocene period, changed the general morphographic structure. This change occurred by fractures formed due to the rigid characteristics of the Jurassic-Cretaceous massive limestones. Although the dominant structure around the study area is curved, the last movement has been shaped by faulting and many shapes of fault geomorphology have enriched the geomorphological landscape of the region. The aim of this study was to determine the tectono-geomorphological forms in the Sinebel Gorge Valley and its surroundings, and to reveal its lithological, tectonic relations and its effects on the landscape. As a result of field and literature studies, several geomorphic elements reflecting fracture tectonics were identified in the study area: hanging valleys, hanging cave, fault valleys, fault perpendicularty, stepped topography, faceted hills, directional lapya, landslide, antesedant valley, sequential scree cones, cut hills, travertine, shifted valleys slope, slope fractures. As a result of these investigations, it is understood that these shapes are formed depending upon the compression and stress tectonics. The geomorphological landscape of the area has a tectono-dynamic character and later became a polygenic topography with the coming into play of denudation processes.

Here, we show the present-day tectonic stress field and regional GPS velocity and strain rate fields in Hubei Province, central China. Our results are calculated based on the digital observation data from 01 January 2010, to 31 December 2017, by using the seis-CAP, P-wave first motion, and grid search methods and the software GAMIT/GLOBK10.4. The results show that the P axis azimuths of focal mechanism solutions, the principal compressional stress field, and the regional velocity and strain rate fields are conformably compressional in a NW–SE direction. The regional stress shape ratio R values are relatively low, and the faults are dominantly compressive-shear or compresso-shear faults. The average velocity modulus value for the GPS observation stations in western Hubei is 6.1 mm/a, which is higher than that in eastern Hubei (5.4 mm/a). The average velocity modulus value in the Jianghan Basin interior is relatively low (4.4 mm/a), while that in the northwestern Jianghan Basin is higher (7.6 mm/a). The strain rate field is characterized by NW–SE compression accompanied by NE–SW tension. The results suggest that the present-day crustal movement in Hubei Province is mainly controlled by collisions with the Indian Plate in the west and the Philippine Plate in the east and the consequent crustal shortening induced by western Hubei wedging into the Jianghan Basin. Further, the resistance by the thrust-and-fold belt in eastern Hubei contributes to the principal compressional movement in the study area. The T axis azimuth of focal mechanism solutions is consistent with the principal extensional stress field direction. In the central and northern Jianghan Basin, the R values are relatively high, the faults are mainly transtensional, and the crustal deformation is mainly extensional, which may be affected by the denudation, thinning and rapid rebound of the Dabie Orogen, resulting in tectonic extrusion and flow in the Jianghan Basin to both the NE and SW sides.

Thick sediments from foreland basins usually provide valuable information for understanding the relationships between mountain building, rock denudation, and sediment deposition. In this paper, we report environmental magnetic measurements performed on the Miocene sediments in the Subei Basin, northeastern Tibetan Plateau. Our results show two different patterns. First, the bulk susceptibility and SIRM, ARM, and HIRM mainly reflect the absolute-concentration of magnetic minerals; all have increased remarkably since 13.7 Ma, related to provenance change rather than climate change. Second, the ratios of IRM100mT/SIRM, IRM100mT/IRM30mT, and IRM100mT/IRM60mT, together with the redness and S ratio, reflect the relative-concentration of hematite, being climate-dependent. Their vertical changes correlate in general with the long-term Miocene climatic records of marine oxygen isotope variations, marked by the existence of higher ratios between 17 and 14 Ma. This may imply that global climate change, rather than uplift of the Tibetan Plateau, played a dominant role in the long-term climatic evolution of the Subei area from the early to middle Miocene.

The vast geomorphological heritage of the outstanding German scientist Albrecht Penck mainly related to general geomorphology, the geomorphology of mountains, climatology, hydrology and hypsometric maps, has so far been insufficiently known by Soviet/Russian geomorphologists. His fundamental studies are related to the last twenty years of the 19 th and the first quarter of the 20 th century. He was engaged in fieldwork in Europe–mainly in the Alps and the Danube basin, the mountains of Spain, North Morocco, and also in Canada, Australia, China, Japan and some other countries, and created the first classification of climates. Together with Eduard Bruckner, he was co-author of a concept of ancient glaciation; they were the first to identify the four ice ages of the European Pleistocene (Gunz, Mindel, Riss, Wurm). Albrecht Penck enriched geomorphology with the concept of “summit level of denudation”. He was convinced that the heights of the snow- and forest-line were responsible for mountain heights, the rate of denudation and therefore, determine the height of the summit level of denudation ( gipfelflur ) for each climate. Later, he moved away from these ideas and introduced the term “summit surface” poining to the constant eleveation of the summit levels without explaining the phenomenon per se. Academician Konstantin Markov spoke of Albrecht Penck as one of the prominent geomorphologists with rich scientific heritage and as “Nestor the Chronicler of foreign geomorphology”. For a long time Penck was a Director of the Institute and Museum of Oceanography in Berlin and a member of the Royal Swedish Academy of Sciences. He was well-known in the academic circles of Russia, some of his works were published in Russian; he regularly visited Russia and was elected honorary member of the Moscow Society of Naturalists, Russia’s oldest society of nature explorers set up in 1805. In 1859, von Humboldt-Ritter Stiftung (the Humboldt-Ritter Foundation) was set up in Germany and actively functioned after their deaths. After Pencks death died in 1945 the foundation was transformed to Humboldt-Ritter-Penck Foundation, and has been active up to now days.

Introduction. Climate warming, which is currently observed in the Arctic, has the potential to intensify chemical denudation in river basins partially or completely located within permafrost. In order to test this hypothesis, we investigated the longterm dynamics of the rivers’ ion runoff in the Pechora River basin, 42 % of which are located within permafrost. Methods. To study changes in the chemical denudation intensity in nonstationary climate, we analyzed data of systematic observations over the main ion concentrations from 1985 to 2017 in the Pechora River outlet (Naryan-Mar) and its tributaries (Usa, Adzva, Kolva, Sula rivers). The intensity of chemical denudation in the Pechora River basin was assessed in terms of ion runoff. The probable reasons for its changes — water content and concentrations of macrocomponents — were also analyzed. Results. The ion-salt composition of Pechora River water is mainly determined by the dissolution of carbonate minerals in the underlying rocks. Calculations and comparison of ion runoff moduli showed that the studied rivers are comparable in terms of the chemical denudation intensity in catchments. The exceptions were the Sula and Kolva rivers, where, with the river runoff, a relatively high amount of chlorides and hydrocarbonates is carried. Contrary to the initial assumptions about the possible intensification of the chemical denudation process under the conditions of climate warming, we found a decrease in the sulfate runoff moduli in all rivers. In addition to that, individual changes in the runoff moduli for other main ions are observed for the studied rivers. Conclusion. In modern conditions, the chemical denudation intensity remains at the level of the end of the last century, and the long-term dynamics of the Pechora River ion runoff correlates in time with the variability of anthropogenic factors, in particular, wet sulfate deposition with atmospheric waters.

Geological records indicate that the hyper-aridity in the Atacama Desert has prevailed since at least the mid-Miocene, with shorter periods of increased humidity punctuating long-term aridity. The 7-m-high accumulation of colluvial sediments at the Salar Grande (21°S/70°W) studied here provides a key palaeoclimate record to understand hillslope dynamics and its relation to humid periods. While 10Be surface exposure ages point to long-term surface stability of the flat upslope surface, a combination of humidity-driven soil creep, overland flow and soil creep related to seismic shaking, caused denudation of the hillslope and accumulation of several metres of colluvium over much shorter timescales during the last 130 ka. A robust chronology for the hillslope sediments has been established by using Infrared Stimulated luminescence (pIR-IR225 protocol) on K-feldspar extracts from nine samples collected within the accumulation. A series of tests has been carried out to confirm the suitability of the method. The estimated ages indicate accelerated sedimentation at 35–80 ka, and 100–130 ka, which are interpreted as periods with more humid climate conditions than present. These findings agree with climate variations in the hyper-arid Atacama indicated by the activity of coastal alluvial fans and river catchments.

The South Atlantic passive margin along the south-eastern Brazilian highlands exhibits a complex landscape, including a northern inselberg area and a southern elevated plateau, separated by the Doce River valley. This landscape is set on the Proterozoic to early Paleozoic rocks of the region that once was the hot core of the Araçuaí orogen, in Ediacaran to Ordovician times. Due to the break-up of Gondwana and consequently the opening of the South Atlantic during the Early Cretaceous, those rocks of the Araçuaí orogen became the basement of a portion of the South Atlantic passive margin and related south-eastern Brazilian highlands. Our goal is to provide a new set of constraints on the thermo-tectonic history of this portion of the south-eastern Brazilian margin and related surface processes, and to provide a hypothesis on the geodynamic context since break-up. To this end, we combine the apatite fission track (AFT) and apatite (U–Th)/He (AHe) methods as input for inverse thermal history modelling. All our AFT and AHe central ages are Late Cretaceous to early Paleogene. The AFT ages vary between 62 Ma and 90 Ma, with mean track lengths between 12.2 μm and 13.6 μm. AHe ages are found to be equivalent to AFT ages within uncertainty, albeit with the former exhibiting a lesser degree of confidence. We relate this Late Cretaceous–Paleocene basement cooling to uplift with accelerated denudation at this time. Spatial variation of the denudation time can be linked to differential reactivation of the Precambrian structural network and differential erosion due to a complex interplay with the drainage system. We argue that posterior large-scale sedimentation in the offshore basins may be a result of flexural isostasy combined with an expansion of the drainage network. We put forward the combined compression of the Mid-Atlantic ridge and the Peruvian phase of the Andean orogeny, potentially augmented through the thermal weakening of the lower crust by the Trindade thermal anomaly, as a probable cause for the uplift. Keywords: Tectonic reactivation, Differential denudation, Passive margin, South-eastern Brazil, Apatite fission tracks, Apatite (U–Th)/He

The Zemo Imereti (Chiatura) Structural Plateau covers the easternmost part of the western Georgia limestone belt and is the only region of the platform karst in the entire Caucasus. Zemo Imereti Plateau’s complex structural studies revealed that the karst landscape has been completely transformed due to human strong economic activities, mainly related to the manganese unplanned, predatory extraction. The ore mining process completely destroyed the soil and vegetation cover thus creating “anthropo-badlands”. Due to manganese open-cast mining, the layers located over limestones are almost totally removed and heavy rains stipulate intense washout of substances from loose rocks. Intense washout of manganese extracted from mines and high contamination of river water streams take place directly in the river beds. Karst sinkholes and wells are common in the plateau, which are often used as waste fills-storages by the local population. Contaminated underground karst waters flowing into the above mentioned landforms are directly related to the karst springs used by the population and occasionally cause their turbidity and contamination, which is also confirmed by our indicator tests. As a laboratory study of the samples showed, mineralization of underground karst waters in the study area is 1.5 - 3 times higher than similar values in neighboring karst areas, which should be explained by the widespread of manganese open pits in the feeding basins of underground karst waters. According to the materials obtained from our surveys and calculations carried out, karst (chemical) denudation (surface 64.2 - 190.6 m3/km2/year, underground 1.5 - 117.0 m3/km2/year) has been increased in the study area than in other karst regions of Georgia, which is also related to technologic factors.

Red Mediterranean Soils developed over carbonate rocks can precipitate pedogenic carbonates at the base of their profiles, forming an evolutionary stage of calcretes. We studied a 0.6 m deep soil profile in Dalmatia (Croatia) where the lowest section of the soil is a calcic horizon formed by diffuse calcite particles and small nodules. These nodules record different events of dissolution and precipitation. Using a 3-month period of soil environmental monitoring, where soil temperature, soil water content, soil bulk electrical conductivity and soil air CO2 were measured, we implemented a thermodynamic model for dissolution and precipitation of calcite in the soil. The simulation shows a stage dominated by calcite dissolution during spring and early summer followed by a stage dominated by calcite precipitation. Soil air CO2 is the main control of the calcite reactions, with concentration of solutes also being of some importance during the stage of calcite precipitation. Soil water content and temperature, both affect soil air CO2. Precipitation events also have high-frequency impact on soil air CO2, but the response is complex. The model enables soil water solutions to be supersaturated in relation to calcite without precipitation of that mineral. Simulated soil water reached variable values of supersaturation in relation to calcite before its precipitation was triggered, suggesting that there is no fixed threshold value for the precipitation of calcite in a particular soil. During the 3-month simulated period, 83% of the calcite dissolved was reprecipitated as pedogenic carbonate. Most of the initially dissolved calcite, was expected to be diffuse pedogenic carbonate particles, although nodules and bedrock at the base of the soil should also have contributed to the solutes dissolved. Therefore, karst landscapes where soils have pedogenic carbonates are expected to record less denudation rates than those regions without calcretes.

Наблюдения за формированием осадка в котловине озера Спартаковского (о. Большевик архипелага Северная Земля) на протяжении нескольких месяцев, изучение отложений, слагающих берега Хатангского залива и долины р. Лены, формировавшихся в среднем и позднем неоплейстоцене, выявили причины и скорости процессов седиментации на суше и дне водоёмов, происходящих при значительных колебаниях базиса эрозии; а также специфическое прилегающее залегание четвертичных отложений, которое встречается не как исключение, а как правило в зависимости от мощности и времени действия процессов осадконакопления и денудации. Находки раковин морских моллюсков Hiatella arctica (Linnaeus, 1758) и линз янтареносных песков, датирование отложений свидетельствуют о каргинском возрасте морских и эстуарно-морских отложений в долине р. Хатанги., Observation of sedimentation and denudation in drained periglacial lake during some months at Bolshevik Island of Severnaya Zemlya Archipelago, sediments studying of Khatanga Bay and Lena River Valley, which formed in Middle and Late Pleistocene reveal causes and rates of sedimentation on land and bottom of basins during fluctuations of erosion level base. Overlap and broken bedding of sediments and rocks are not rare cases of bedding and they depends on time and capacity of sedimentation and denudation processes. Found and dated shells of marine mollusks Hiatella arctica (Linnaeus, 1758) wood and amber sands give an evidence of sediments marine genesis and their Karginski age (Regional stratigraphic scale of Siberia) in Khatanga Bay.

We present a detailed analysis of weathering fluxes at Lake Baikal, the largest lake in the world, using the major element, trace element and isotope geochemistry of major inflowing rivers, the lake itself, and its sediments. Our objective is to assess how lake records could be used to understand river-catchment-scale denudation and weathering processes. Total denudation rates at Lake Baikal, as obtained from meteoric 10Be/9Be, are an order of magnitude lower than the global average, at 16–35 t km−2 yr−1. Chemical weathering rates obtained from the riverine dissolved load and discharge are, on the other hand, in the same range as global values, at 6–29 t km−2 yr−1. Chemical weathering rates are higher in the north of the catchment than in the south, consistent with higher runoff in the north. In contrast, 10Be/9Be-derived denudation rates are higher in the south. We hypothesize that this pattern of variation may be due to the stabilizing effect of permafrost soils preventing erosion in the north. An inverse model shows that the Selenga River, Lake Baikal's major tributary, has a silicate weathering contribution to riverine dissolved cation fluxes of 42 mol%; this and other characteristics are representative of large rivers globally. Many trace elements have much lower concentrations in the lake than in inflowing rivers (Be (5%), Mn (3%), Fe (0.4%) and REE (1–2%)). We suggest, based on REE patterns and Mn, Fe-depth profiles in the lake, that this removal is the result of pH induced changes in dissolved-adsorbed partitioning at the river-lake interface, and the incorporation of trace elements into authigenic Fe-Mn (oxyhydr)oxide phases forming within the lake. Strontium is isotopically uniform within the lake, demonstrating that the whole lake mixes on a timescale shorter than its residence time (, Geochimica et Cosmochimica Acta, 321, ISSN:0016-7037, ISSN:1872-9533

The utility of speleothems as environmental and geological archives has greatly expanded with recent advances in geochronology. Here we reevaluate their ability to constrain late Cenozoic uplift in karst terranes. Using combined U-Th and U-Pb speleothem chronologies for the Buchan karst along the passive margin of southeastern Australia, we calculate a maximum uplift rate of 76 ± 7 m m.y.−1 maintained over the past 3.5 m.y. The timing and extent of this process is consistent with independent constraints on Neogene uplift in Australia, possibly in response to increased plate-boundary strain with New Zealand. Speleothem chronologies provide highly precise age control on individual events and the potential for near-continuous records across long periods of geological time, complementing and expanding upon existing uplift proxies.

The effects of human activity on geomorphic processes, particularly those related to denudation/sedimentation, are investigated by reviewing case studies and global assessments covering the past few centuries. Evidence we have assembled from different parts of the world, as well as from the literature, show that certain geomorphic processes are experiencing an acceleration, especially since the mid-twentieth century. This suggests that a global geomorphic change is taking place, largely caused by anthropogenic landscape changes. Direct human-driven denudation (through activities involving excavation, transport, and accumulation of geological materials) has increased by a factor of 30 between 1950 and 2015, representing a ten-fold increase of per capita effect. Direct plus indirectly human-induced denudation (triggered by land surface alteration) is presently at least one order of magnitude greater than denudation due to purely natural processes. The activity of slope movements, which represent an important contribution to denudation, sediment generation and landscape evolution, also shows a clear intensification. Frequency of hazardous events and disasters related to slope movements (an indirect measure of process frequency) in specific regions, as well as at continental and global levels, has grown considerably, in particular after the mid-twentieth century. Intense rainstorm events are often related to slope movement occurrence, but the general increasing trend observed is not satisfactorily explained by climate. Sedimentation has augmented considerably in most regions and all kinds of sedimentation environments. Although the link between denudation and sedimentation is not direct and unequivocal, it is safe to assume that if sedimentation rates increase in different regions during a given period, denudation must have increased too, even though their magnitudes could be different. This augmentation, particularly marked from the second half of the last century onwards, appears to be determined mainly by land surface changes, in conjunction with climate change. The changes observed suggest: a) there is evidence at a global scale of a growing response of geomorphic systems to socio-economic drivers, being Gross Domestic Product density, a good indicator of the human potential to cause such impacts; b) Land use/cover changes enhance effects of climate change on global denudation/sedimentation and landslide/flood frequency, and appear to be a stronger controlling factor; c) Our findings point to the existence of a global geomorphic change. This manifestation of global change is especially evident since the ?great geomorphic acceleration? that began in the middle of the 20th century, and constitutes one of the characteristics of the proposed Anthropocene. This work was supported, at different stages, by projects: FEDER, AEI, CGL2017-82703-R (Ministerio de Ciencia e Investigacion, Spain) and PICT2011-1685; MTM2014-56235-C2-2215 (Ministerio de Ciencia, Tecnología e Innovacion, Argentina). We also thank Dr. Anthony R. Berger for critical review and writing assistance.

We suggest a set of variables based on documentation of the active denudational and depositional fronts in a segment of Chandra river valley in the Higher Himalaya (India). Convergence and divergence of the denudational front (Dw) with depositional front (S), advancements of lateral valley denudation front (Lw), and the changes in base levels (bn) under the constant valley-accommodation-space earmarks the active geomorphic evolution of the Chandra valley basin through Late Holocene. The cumulative enrichment of stable and metastable sediment mass entrapped into precarious valley spaces, valley floors, and catchments is susceptible to episodic clearance by mass flow through flash floods during extreme conditions like glacial surge, GLOF, cloud burst or river dam and breach activity. Field mapping and scaling of these parameters and sediment masses provide essential database and parametric inputs to long-term predictions and interrelationships of denudation with basin fill and sediment transfer rates. We find that the entrapped sediment mass in proportionately larger denudational catchment area against restricted valley conduits into the Chandra trunk system hampers correct estimation on the rates of sediment production and transfer. Late Holocene regime is further stressed by excessive sediment inputs from largely underestimated colluvial and scree deposition, besides recycling of morainic material. Hence the mapping of advancements of these various fronts (surfaces) as suggested here makes a feasible approach to study the Late Holocene evolution of the glaciofluvial basins in the Higher and Trans Himalayas.

L’“écriture empêchée” de Samuel Beckett se trouve contrainte par ses propres moyens d’expression. Entre 1930 et la fin des années 1940, à une époque où le travail de l’écrivain est marqué par l’improductivité littéraire, comme en témoigne sa correspondance avec Thomas MacGreevy et Mary Manning Howe. Pourtant, c’est cette même improductivité qui devient source de productivité et que l’auteur décrit dans ses échanges épistolaires avec Georges Duthuit., Samuel Beckett’s ‘hindered writing’ is constrained by his own mean of expression, at a time when, between 1930 and 1940, the writer’s work is marked by literary standstill, as his correspondence with Thomas MacGreevy and Mary Manning Howe testifies. However, this same absence of productivity becomes a source of productivity, which the author describes in his epistolary exchanges with Georges Duthuit.

This study presents the first apatite fission-track results from the Tolimán area, which is located in the western portion of the southern Sierra Madre Oriental, central Mexico. In total, six rock samples from different lithostratigraphic units were dated, adding new results to the thermochronological data set of the Sierra de los Cuarzos–San Joaquín–Tamazunchale transect in the Mexican fold-and-thrust belt. The apatite fission-track ages vary from 84 ± 4 Ma to 52 ± 2 Ma, indicating that the main denudation period of the Tolimán area lasted until the Eocene. Combining our results with previous geological data, we suggest that the western part of the southern Sierra Madre Oriental was uplifted and undergoing erosion during the whole period of development of the Campanian–Ypresian Mexican orogenic system. Therefore, the Tolimán area may be considered as one of the source areas from which clastic materials of the Campanian–Maastrichtian Méndez and Paleocene–Eocene Velasco and Chicontepec Formations were partially derived. Older cooling ages recording the latest Aptian accretion of the Guerrero terrane with the Mexican continental interior were not detected in samples from the Tolimán area.

Disentangling the influence of bedrock erodibility from the respective roles of climate, topography and tectonic forcing on catchment denudation is often challenging in mountainous landscapes due to the diversity of geomorphic processes in action and of spatial/temporal scales involved. The Dora Baltea catchment (western Italian Alps) appears the ideal setting for such investigation, since its large drainage system, extending from the Mont Blanc Massif to the Po Plain, cuts across different major litho-tectonic units of the western Alps, whereas this region has experienced homogeneous climatic conditions and glacial history throughout the Quaternary. We acquired new 10Be-derived catchment-wide denudation rates from 18 river-sand samples collected both along the main Dora Baltea river and at the outlet of its main tributaries. The inferred denudation rate results vary between 0.2 and 0.9 mm/yr, consistent with values obtained across the European Alps by previous studies. Spatial variability in denudation rates was statistically compared with topographic, environmental and geologic metrics. 10Be-derived denudation records do not correlate with the distribution of modern precipitation and rock geodetic uplift. We find, rather, that catchment topography, in turn conditioned by bedrock erodibility (litho-tectonic origin) and glacial overprint, has the main influence on denudation rates. We calculated the highest denudation rate for the Mont Blanc Massif, whose granitoid rocks and long-term tectonic uplift support steep slopes and high relief and thus favour intense glacial/periglacial processes and recurring rock fall events. Finally, our results, in agreement with modern sediment budgets, demonstrate that the high sediment input from the Mont Blanc catchment dominates the Dora Baltea sediment flux, explaining the constant low 10Be concentrations measured along the Dora Baltea course even downstream the multiple junctions with tributary catchments.

The denudation of rocks in mountain belts exposes a range of fresh minerals to the surface of the Earth that are chemically weathered by acidic and oxygenated fluids. The impact of the resulting coupling between denudation and weathering rates fundamentally depends on the types of minerals that are weathering. Whereas silicate weathering sequesters CO2, the combination of sulfide oxidation and carbonate dissolution emits CO2 to the atmosphere. Here, we combine the concentrations of dissolved major elements in stream waters with 10Be basin-wide denudation rates from 35 small catchments in eastern Tibet to elucidate the importance of lithology in modulating the relationships between denudation rate, chemical weathering pathways, and CO2 consumption or release. Our catchments span three orders of magnitude in denudation rate in low-grade flysch, high grade metapelites, and granitoid rocks. For each stream, we estimate the concentrations of solutes sourced from silicate weathering, carbonate dissolution, and sulfide oxidation using a mixing model. We find that for all lithologies, cation concentrations from silicate weathering are largely independent of denudation rate, but solute concentrations from carbonates and, where present, sulfides increase with increasing denudation rate. With increasing denudation rates, weathering may, therefore, shift from consuming to releasing CO2 in both (meta)sedimentary and granitoid lithologies. We find that catchments draining high grade metamorphic rocks have systematically higher concentrations of sulfate from sulfide weathering than catchments containing weakly metamorphosed sediments. Moreover, our data provide tentative evidence that sulfate concentrations in these catchments are potentially more sensitive to denudation rate. We propose that changes in the sulfur oxidation state during prograde metamorphism of pelites in the mid-crust could lead to sulfate reduction that is even more complete than in low-grade sediments and provides a larger sulfide source for oxidation upon re-exposure of the rocks. In this case, the elevated concentration of sulfate in catchments draining high-grade metapelites would suggest that exposure of an increasing fraction of metamorphic rocks during orogenesis could lead to a boost in the release of CO2 that is independent of denudation rate.

For area D of the Ordos Basin, the Yan 9 oil-bearing group were finely divided and compared using the marker layer method, the principle of equal thickness, and the sedimentary cycle analysis method. According to the stratigraphic division results, the plan view of the thickness of the small strata and the structure map of the top of the strata were drawn. It is believed that the Yan93 and Yan91+2 stratums are relatively complete in the whole area and have not suffered denudation. The overall thickness of the formation does not vary widely, and the thickness of the two small layers is mainly about 20m. The nose-like structure at the top of Yan 9 is densely developed, forming multiple rows of nearly east-west nose-like structures, with a structural amplitude less than 25m, and the distribution of rhinoplasty has a certain difference. The distance between rhinoplasty is 3-8km. These nose structures provide favorable trap conditions for hydrocarbon accumulation. The study of the stratigraphic and structural characteristics of the Yan 9 oil-bearing group provides basic geological data for the prediction of later sedimentary facies, sand body distribution, reservoir characteristics and favorable blocks, which is of great significance.

Long-term landscape evolution is controlled by tectonic and climatic forcing acting through surface processes. Rivers are the main drivers of continental denudation because they set the base level of most hillslopes. The mechanisms of fluvial incision are thus a key focus in geomorphological research and require accurate representation and models. River incision is often modeled with a stream power model (SPM) based on the along-stream evolution of drainage area and channel elevation gradient but can also incorporate more complex processes such as threshold effects and statistical discharge distributions, which are fundamental features of river dynamics. Despite their importance in quantitative geomorphology, such model formulations have been confronted with field data only in a limited number of cases. Here we investigate the behavior of stochastic-threshold incision models across the southeastern margin of the French Massif Central, which is characterized by significant relief and the regular occurrence of high-discharge events. Our study is based on a new dataset combining measurements of discharge variability from gauging stations, denudation rates from 34 basins from 10Be cosmogenic radionuclide (CRN) concentration measurements in river sediments, morphometric analysis of river long profiles, and field observations. This new dataset is used for a systematic investigation of various formulations of the SPM and to discuss the importance of incision thresholds. Denudation rates across the SE margin of the Massif Central are in the 20–120 mm kyr−1 (equivalent to mm/ka in the figures) range, and they positively correlate with slope and precipitation. However, the relationship with the steepness index is complex and supports the importance of taking into account spatial variations in parameters (D50, discharge variability k, runoff) controlling the SPM. Overall, the range of denudation rate across the margin can mainly be explained using a simple version of the SPM accounting for spatially heterogeneous runoff. More complex formulations including stochastic discharge and incision thresholds yield poorer performances unless the spatial variations in bedload characteristics controlling incision thresholds are taken into account. Our results highlight the importance of the hypotheses used for such a threshold in SPM application to field studies and notably the impact of actual constraints on bedload size.

IF 4.40; Q1); International audience; An emerged coral reef terrace sequence flanks the northern coast of Sumba Island in Indonesia. The sequence was created by the joint effects of uplift and Quaternary sea level oscillations. Since its emergence, it undergoes chemical erosion, which is facilitated by its carbonate lithology. The morphology is dissected by multiple catchments drained by deep canyons, whose stream profiles display several knickpoints. We applied a multi-methods approach using high-resolution topographic data (Pleiades imagery), geomorphological analysis and denudation rates derived from 36Cl cosmogenic nuclide concentrations to characterize the dynamics of these coastal drainages. We specifically investigate (1) the channel response to eustatic forcing, by analyzing knickpoint dynamics along a longitudinal river profile, and (2) the control of internal and external forcing over the catchment-scale erosion. Firstly, knickpoints form at the distal edge of the emergent reef at each regressive stage following a sea level highstand. The knickpoint propagates and rotates upward by regressive erosion. Knickpoint propagation rate decreases sharply over time until it becomes negligible before the next sea-level rise, which implies a marked decline in knickpoint retreat rate before its resorption. We attribute the inability of the river at Cape Laundi to fully propagate eustatic oscillations to its low stream discharge and low sediment supply, related to its small drainage area, to the karstic nature of the coral reef terraces composing the sequence, and to the high frequency of eustatic forcing. Secondly, average denudation rates calculated from 36Cl cosmogenic nuclide concentrations of sands collected at the outlet of five catchments draining the sequence amount to 69 ± 8 mm·ka−1. We emphasize the role of canyon areas in driving the denudation of the major catchments. However, no first-order correlation has been observed between catchment metrics, uplift rates and denudation rates. Finally, our correlations between catchment finite eroded volumes and uplift rates highlight the tendency of catchments to widen with low uplift rate and to lengthen while incising the sequence deeply with higher uplift rates.

Observational data of coastal change over much of the Arctic are limited largely due to its immensity, remoteness, harsh environment, and restricted periods of sunlight and ice-free conditions. Barter Island, Alaska, is one of the few locations where an extensive, observational dataset exists, which enables a detailed assessment of the trends and patterns of coastal change over decadal to annual time scales. Coastal bluff and shoreline positions were delineated from maps, aerial photographs, and satellite imagery acquired between 1947 and 2020, and at a nearly annual rate since 2004. Rates and patterns of shoreline and bluff change varied widely over the observational period. Shorelines showed a consistent trend of southerly erosion and westerly extension of the western termini of Barter Island and Bernard Spit, which has accelerated since at least 2000. The 3.2 km long stretch of ocean-exposed coastal permafrost bluffs retreated on average 114 m and at a maximum of 163 m at an average long-term rate (70 year) of 1.6 ± 0.1 m/yr. The long-term retreat rate was punctuated by individual years with retreat rates up to four times higher (6.6 ± 1.9 m/yr; 2012–2013) and both long-term (multidecadal) and short-term (annual to semiannual) rates showed a steady increase in retreat rates through time, with consistently high rates since 2015. A best-fit polynomial trend indicated acceleration in retreat rates that was independent of the large spatial and temporal variations observed on an annual basis. Rates and patterns of bluff retreat were correlated to incident wave energy and air and water temperatures. Wave energy was found to be the dominant driver of bluff retreat, followed by sea surface temperatures and warming air temperatures that are considered proxies for evaluating thermo-erosion and denudation. Normalized anomalies of cumulative wave energy, duration of open water, and air and sea temperature showed at least three distinct phases since 1979: a negative phase prior to 1987, a mixed phase between 1987 and the early to late 2000s, followed by a positive phase extending to 2020. The duration of the open-water season has tripled since 1979, increasing from approximately 40 to 140 days. Acceleration in retreat rates at Barter Island may be related to increases in both thermodenudation, associated with increasing air temperature, and the number of niche-forming and block-collapsing episodes associated with higher air and water temperature, more frequent storms, and longer ice-free conditions in the Beaufort Sea.

The Late Miocene-Pliocene Dhok Pathan Formation (DPF) fluvial sequence of Eastern Sulaiman Foldbelt and Thrust Belt (SFTB) has different lithofacies of sandstone and mudstone deposited in the Himalayan foredeep basin. The present study deals with detailed geochemical analyses of DPF to deduce its provenance, weathering, and tectonic settings. The geochemical data of major oxides plot on scatter diagram shows that the sandstones of DPF are predominantly Arkose-Subarkose and Litharenite-Sublitharenite which were mainly sourced from granitic composition and deposited in fluvial conditions under semi-arid to arid climate. The low elemental ratios of Ni/Co and Cu/Zn indicate oxic conditions during deposition. The mudstone’s ICV values are 1.44 indicating that the source area was influenced by moderate to high weathering. The geochemical analysis indicates lower values of Zr, Nb, Y, and Y/Ni ratio in studied area which point out the existence of ultramafic/mafic sequence in source area. The tectonic discrimination diagrams depict active continental margin tectonic settings for provenance of DPF with partial influx from Continental and Oceanic Island Arc. The present study concludes that clastic rocks of DPF were mainly sourced from Himalayan orogeny with partial influx of Kohistan-Ladakh arc and subsequent deposition in Himalayan foredeep basin which coincides with regional tectonic scenario. Interpretation of paleoenvironments and basin tectonics by geochemical analysis will help to delineate the poorly understood uplift and denudation history in SFTB.

The Qinshui Basin is in the Central Orogenic Belt of the North China Craton (NCC), and the production of coalbed methane accounts for 70% of China’s total coalbed methane output. Aiming at the unclear dynamic causes of large-scale coalbed methane accumulation in the basin and the unclear response relationship with the destruction of the NCC, we present joint illite crystallinity and vitrinite reflectance study across the Zijin Mountain and Qincan 1 wells of the Qinshui Basin, respectively. Inverse modeling suggested that tectono-thermal events occurred during the Early Cretaceous, associated with the maximum burial depth and heat flow. The maximum paleo-geothermal temperature and gradient reconstruction results recorded at the Carboniferous strata are 180–190°C and 6.5°C/100 m. The denudation thicknesses recorded by illite crystallinity of Zijinshan and the vitrinite reflectance of the Qincan 1 Well are 3,180.63 m and 3,269.32 m, respectively. We propose that the Qinshui Basin was affected by the extensional environment of the NCC, which caused deep lithospheric thinning and magma upwelling, and a tectono-thermal event occurred during the Early Cretaceous in Qinshui Basin. In addition, the accumulation of coalbed methane, triggered by a tectono-thermal event during the Early Cretaceous, is consistent with the early Cretaceous accumulation and mineralization events in the NCC. Overall, our results reflect the subduction event influence of the western Pacific plate into the East Asian continental plate on the tectono-thermal history of the Central Orogenic Belt of the NCC, which is theoretically significant for clarifying the thermal lithospheric thickness and rheological structure of the basin, as well as the evolutionary history of coalbed methane, and the basin response relationship to the destruction of the NCC.

The Devonian–lower Eocene Central East and NE Greenland Composite Tectono-Sedimentary Element (CTSE) is a part of the NE Atlantic rift system. The East and NE Greenland geology is therefore analogous to that of the prolific basins on the conjugate Atlantic margin and in the North Sea in many respects. Nonetheless, hydrocarbon discoveries remain. The presence of world-class source rocks, reservoirs and seals, together with large structures, may suggest an East and NE Greenland petroleum potential, however. The CTSE was established through Devonian–Carboniferous, Permian–Triassic and Jurassic–Cretaceous rifting interspersed by periods of uplift and post-rift sagging. Subsequently, Paleocene–Eocene magma-rich rifting accompanied the NE Atlantic break-up. Depositional environments through time varied in response to the changing tectonism and climate. Non-marine deposition dominated until the end of the Triassic, only interrupted by marine sedimentation during Late Permian–Early Triassic times. Subsequently, marine conditions prevailed during the Jurassic and Cretaceous. A volumetric series of basalt erupted over most of the CTSE during the latest Paleocene–early Eocene following a significant latest Cretaceous–Paleocene regression, uplift and erosion event. Since the Eocene, denudation pulses have removed much of these basalts and uniquely exposed the up to 17 km-thick strata of the CTSE.

Reconstructing Cenozoic history of continental silicate weathering is crucial for understanding Earth’s carbon cycle and greenhouse history. The question of whether continental silicate weathering increased during the late Cenozoic, setting the stage for glacial cycles, has remained controversial for decades. Whereas numerous independent proxies of weathering in ocean sediments (e.g., Li, Sr, and Os isotopes) have been interpreted to indicate that the continental silicate weathering rate increased in the late Cenozoic, beryllium isotopes in seawater have stood out as an important exception. Beryllium isotopes have been interpreted to indicate stable continental weathering and/or denudation rates over the last 12 Myr. Here we present a Be cycle model whose results show that variations in the (9)Be weathering flux are counterbalanced by near-coastal scavenging while the cosmogenic (10)Be flux from the upper atmosphere stays constant. As a result, predicted seawater (10)Be/(9)Be ratios remain nearly constant even when global denudation and Be weathering rates increase by three orders of magnitude. Moreover, (10)Be/(9)Be records allow for up to an 11-fold increase in Be weathering and denudation rates over the late Cenozoic, consistent with estimates from other proxies. The large increase in continental weathering indicated by multiple proxies further suggests that the increased CO(2) consumption by continental weathering, driven by mountain-building events, was counterbalanced by other geological processes to prevent a runaway icehouse condition during the late Cenozoic. These processes could include enhanced carbonate dissolution via pyrite weathering, accelerated oxidation of fossil organic carbon, and/or reduced basalt weathering as the climate cooled.

(IF 4.45: Q1); International audience; The emerged coral reef terrace sequence at Cape Laundi, on the north coast of Sumba Island (Indonesia), with at least 18 successive strandlines, remains poorly dated in spite of numerous previous data. The age discrepancies within these coral reef terraces (CRTs) were previously explained by their polycyclic nature, triggered by marine erosion and reoccupation of old coral colonies by new ones. This study aims at highlighting these processes, as well as the continental denudation that participates in the partial stripping of the thin superficial coral reef layer overlying the pre-existing surface, exhuming older coral colonies. For this purpose, we use a combined analysis of 36Cl cosmogenic concentrations, new 230Th/U ages, and previous dating in order to quantify denudation rates affecting the sequence and to highlight the role of marine erosion in reworking the lowest CRT surface. Our results demonstrate that 1) the lowermost CRT is composite, i.e., formed by different reefal limestone units constructed and eroded during successive highstands of the last interglacial, 2) following the last deglaciation, this CRT has been subjected again to coastal erosion and reoccupation during the Mid Holocene highstand, 3) its distal edge is affected by the current marine erosion and shows denudation rates higher by one to two orders of magnitude (from 279 ± 0.4 to 581 ± 0.4 mm ka−1) than the continental denudation values of higher CRTs (14.7 ± 8.3 mm ka−1 on average), 4) at the scale of a single CRT surface, variations in continental denudation rates are caused by epikarstification roughness, and 5) the distal edges have the highest continental denudation rate due to diffusion and regressive erosion produced by the runoff occurring along the steep downward cliff.