Cosmogenic <Superscript>10</Superscript>Be-derived denudation rates of the Eastern and Southern European Alps

Denudation rates from cosmogenic ¹⁰Be measured in quartz from recent river sediment have previously been used in the Central Alps to argue that rock uplift occurs through isostatic response to erosion in the absence of ongoing convergence. We present new basin-averaged denudation rates from large rivers in the Eastern and Southern European Alps together with a detailed topographic analysis in order to infer the forces driving erosion. Denudation rates in the Eastern and Southern Alps of 170–1,400 mm ky⁻¹ are within a similar range to those in the Central Alps for similar lithologies. However, these denudation rates vary considerably with lithology, and their variability generally increases with steeper landscapes, where correlations with topographic metrics also become poorer. Tertiary igneous rocks are associated with steep hillslopes and channels and low denudation rates, whereas pre-Alpine gneisses usually exhibit steep hillslopes and higher denudation rates. Molasse, flysch, and schists display lower mean basin slopes and channel gradients, and, despite their high erodibility, low erosion rates. Exceptionally low denudation rates are also measured in Permian rhyolite, which has high mean basin slopes. We invoke geomorphic inheritance as a major factor controlling erosion, such that large erosive glaciers in the late Quaternary cold periods were more effective in priming landscapes in the Central Alps for erosion than in the interior Eastern Alps. However, the difference in tectonic evolution of the Eastern and Central Alps potentially adds to differences in their geomorphic response; their deep structures differ significantly and, unlike the Central Alps, the Eastern Alps are affected by ongoing tectonic influx due to the slow motion and rotation of Adria. The result is a complex pattern of high mountain erosion in the Eastern Alps, which has evolved from one confined to the narrow belt of the Tauern Window in late Tertiary time to one affecting the entire underthrust basement, orogenic lid, and parts of the Southern Alps today.     

Environmental controls on 10Be‐based catchment‐averaged denudation rates along the western margin of the Peruvian Andes

We present ¹⁰Be‐based basin‐averaged denudation rates for the entire western margin of the Peruvian Andes. Denudation rates range from c. 9 mm ka^?1 to 190 mm ka^?1 and are related neither to the subduction of the Nazca plate nor to the current seismicity along the Pacific coast and the occurrence of raised Quaternary marine terraces. Therefore, we exclude a tectonic control on denudation on a millennial time‐scale. Instead, we explain >60% of the observed denudation rates with a model where erosion rates increase either with mean basin slope angles or with mean annual water discharge. These relationships suggest a strong environmental control on denudation.     

Quantifying the impact of former glaciation on catchment‐wide denudation rates derived from cosmogenic 10Be

Glacial denudation can significantly perturb terrestrial cosmogenic nuclide depth profiles and, if this is not corrected for, derived apparent denudation rates will overestimate the actual denudation rates. Here we determine how much ¹⁰Be‐derived denudation rates – calculated under the assumption of steady state – deviate from actual denudation rates as a function of three parameters: (1) the total amount of glacial denudation, (2) the post‐glacial denudation rate and (3) the time elapsed since deglaciation. We provide correction lines for the full parameter space explored (glacial denudation: 0.01–100 m; post‐glacial denudation rate: 1–1000 mm/ka; deglaciation: 1–100 ka before present), to evaluate and, if necessary, correct denudation rates for the impact of glacial denudation. Applied to ¹⁰Be‐derived catchment‐averaged denudation rates for formerly glaciated catchments in the Black Forest, Germany, we find that uncorrected denudation rates overestimate actual rates by up to a factor of three.     

Morphological controls on the dynamics of carbonate landscapes under a mediterranean climate

The influence of the morphological setting on the denudation of carbonate landscapes and the respective contributions of mechanical and chemical weathering processes are still debated. We have addressed these questions by measuring ³⁶Cl concentrations in 40 samples from the Luberon mountain, SE France, to constrain the denudation of various landscape elements. We observe a clear contrast between the local denudation rates from the flat summit surface, clustered around 30 mm/ka, and the basin‐average denudation rates across the flanks, ranging from 100 to 200 mm/ka. This difference highlights the transient evolution of the range, whose topography is still adjusting to previous uplift events. Such a pattern also suggests that carbonate dissolution is not the only driver of denudation in this setting, which appears to be significantly controlled by slope‐dependent processes.     

Late Quaternary denudation of the Alps,valley and lake fillings and modern river loads

Erosional denudation of the Alps and their role as sediment source underwent major changes throughout the Quaternary, by repeated glaciation and deglaciation. The sediment fluxes of 16 major Alpine drainage basins were quantified by determining the sediment volumes which have been trapped in valleys and lake basins. These became sedimentologically closed after the last glacier retreat around 17 000 cal. BP. The sediment volumes distributed over their provenance areas yield mean mechanical denudation rates between 250 to 1060 mm ka^–1. In contrast, modern denudation rates, derived from river loads and delta surveys, range from 30 to 360 mm ka^–1. Relief, such as mean elevation and slope, turned out to be the primary control of both modern and Late Glacial mechanical denudation. Rock types seem to be responsible for some scatter of the data, but their role is masked by other factors. Modern denudation rates increase with higher proportions of bare rocks and glaciated area, but decrease with forest cover. An area-weighted extrapolation of the studied drainage basins to the entire Alps on the basis of major morphotectonic zones yields a mean denudation rate of 620 mm ka^–1 over the last 17 000 years. This rate clearly exceeds the modern rate of 125 mm ka^–1. Lake sediments and palaeoclimatic reconstructions confirm that the sediment yield of the Alps reached a maximum during deglaciation when large masses of unconsolidated materials were available, vegetation was scarse, and transport capacities were high. During the early Holocene sediment yield declined to a minimum before some climate deterioration and human activities again accelerated erosional processes. Assuming a denudation rate in the early Holocene half of the modern one, the Late Glacial denudation rates must have been in the order of 1100 to 2900 mm ka^–1. Consequently, denudation rates during a glacial/interglacial cycle probably varied by a factor of 14, which lies well within the range of other studies in central Europe, Scandinavia and North America. From large scale sediment budgets of perialpine sedimentary basins the overall denudation rate of the Alps during the Quaternary has been c. 400 mm ka^–1, i.e. about one third lower than the estimate for the last 17000 years. This can be well explained by the outstanding role which deglaciation played in the time span studied here.     

Lithology, landscape dissection and glaciation controls on catchment erosion as determined by cosmogenic nuclides in river sediment (the Wutach Gorge, Black Forest)

Cosmogenic nuclides, measured in quartz from recent river bedload, provide a novel tool to quantify catchment‐wide erosion rates at geologically meaningful time scales. Here we present an analysis of the geomorphological evolution of the 350 km² Wutach catchment in the uplands of the south‐west German Black Forest. The robustness of the method is demonstrated by the fact that, although the area was affected by river capture at 18 kyr bp , the formed gorge is so narrow that spatially averaged erosion rates were not resolvably perturbed. However, because cosmogenic nuclides preserve an erosion memory of several thousand years, the only perturbation introduced was detected in the minor areas that have been subject to the last maximum glaciation. In unglaciated areas, an important relationship between lithology and erosion can by quantified: sandstone lithologies erode at 12–18 mm kyr^?1, granite lithologies at 35–47 mm kyr^?1 and limestone lithologies (as deduced from river load gauging) at 70–90 mm kyr^?1.     

A study of erosion rates on salt diapir surfaces in the Zagros Mountains, SE Iran

Salt exposures and weathering residuum on several salt diapirs in different geographic/climatic settings were studied. Anhydrite, gypsum, hematite, calcite, dolomite, quartz, and clay minerals are the main constituents of the weathering residuum covering the salt diapirs in various thicknesses. Erosion rates of residuum as well as of rock salt exposures were measured at selected sites for a period of 5 years by plastic pegs as benchmarks. Recorded data were standardized to a horizontal surface and to long-term mean precipitation. For the rock salt exposures the following long-term denudation rates were determined of 30–40 mm a⁻¹ for coastal diapirs and up to 120 mm a⁻¹ for mountain salt diapirs. Long-term mean superficial denudation rate measured on weathering residuum of low thickness reached 3.5 mm a⁻¹ on coastal diapirs. The total denudation rate estimated for the thin residuum is close to 4–7 mm a⁻¹ based on apparent correlation with the uplift rate on Hormoz and Namakdan diapirs. Denudation of rock salt exposures is much faster compared to parts of diapirs covered by weathering residuum. The extent of salt exposures is an important factor in the morphological evolution of salt diapirs as it can inhibit further expansion of the diapir. Salt exposures produce huge amounts of dissolved and clastic load, thus affecting the surrounding of the diapir.     

Using climate to relate water discharge and area in modern and ancient catchments

Models relating sediment supply to catchment properties are important in order to use the geological record to deduce landscape evolution and interplay between tectonics and climate. Water discharge (Q _w) is an important factor in the widely used ‘BQART ’ model, which relates sediment load to a set of measurable catchment parameters. Although many of the factors in this equation may be independently estimated with some degree of certainty in ancient systems, water discharge (Q _w) certainly cannot. An analysis of a world database of modern catchments with 1255 entries shows that the commonly applied equation relating catchment area (A ) to water discharge (Q _w = 0·075A^0·8) does not predict water discharge from catchment area well in many cases (R ² = 0·5 and an error spanning about three orders of magnitude). This is because the method does not incorporate the effect of arid and wet climate on river water discharge. The inclusion of climate data into such estimations is an opportunity to refine these estimates, because generalized estimates of palaeoclimate can often be deduced on the basis of sedimentological data such as palaeosol types, mineralogy and palaeohydraulics. This paper investigates how the relationship between catchment area and river discharge varies with four runoff categories (arid, semi‐arid, humid and wet), which are recognizable in the geological record, and modifies the coefficient and exponent of the above‐mentioned equation according to these classes. This modified model yields improved results in relating discharge to catchment area (R ² = 0·95 and error spanning one order of magnitude) when core, outcrop or regional palaeoclimate reconstruction data are available in non‐arid systems. Arid systems have an inherently variable water discharge, and catchment area is less important as a control due to downstream losses. The model here is sufficient for many geological applications and makes it possible to include variations in catchment humidity in mass‐flux estimates in ancient settings.     

Interplay between erosion and tectonics in the Western Alps

Bedrock fission‐track analysis, high‐resolution petrography and heavy mineral analyses of sediments are used to investigate the relationships between erosion and tectonics in the Western Alps. Along the Aosta Valley cross‐section, exhumation rates based on fission‐track data are higher in the fault‐bounded western block than in the eastern block (0.4–1.5 vs. 0.1–0.3 mm yr⁻¹). Erosion rates based on the analysis of bed‐load in the Dora Baltea drainage display the same pattern and have similar magnitudes in the relative sub‐basins (0.4–0.7 vs. 0.04–0.08 mm yr⁻¹). Results highlight that climate, relief and lithology are not the controlling factors of erosion in the Western Alps. The main driving force behind erosion is instead tectonics that causes the differential upward motion of crustal blocks.     

Gypsum karst intensification as a consequence of sulphur mining activity (Jaziv field,Western Ukraine)

The scope of this study is to evaluate the parameters of the gypsum–anhydrite strata karstification under the influence of the quarry exploitation of Jaziv sulphur field (West Ukraine) accompanying by drainage. The quarry drainage provoked the enormous depression cone forming with 100 km² in area and the corresponding intensification of chemical denudation of the gypsum–anhydrite strata. The gypsum karstification rate for the 29-year period of the quarry drainage was 0.06% with the dissolved rock volume of 1,328,507 m³ that is about 80 times higher than in natural conditions. For the drainage period (29 years) the karst denudation rate was 17,952 m³/km² against the natural background of 231.3 m³/km². The absolute value of artificial denudation for the studied massif area is 1.79 cm for 29 years or 0.062 mm/year while the denudation rate under natural conditions would be 0.231 cm for 29 years or 0.0008 mm/year. The forecasted volumes of the surface-evident collapses are evaluated using the relationship between the calculated amount of dissolved sulphate rocks and volumes of the current surface-evident collapses. According to this evaluation, the current collapses correspond to about 34% only from the dissolved rocks volume calculated for the drainage period.     

Long-term landscape evolution of the northeastern margin of the Bohemian Massif: apatite fission-track data from the Erzgebirge (Germany)

To study the relative and absolute timing of post-Variscan cooling and denudation processes in the Erzgebirge of the Mid-European Variscides, eight samples for apatite fission-track (AFT) analysis were collected from a ~1,300 m drill-core. The fission-track data reveal two stages of accelerated cooling through the apatite partial annealing zone (APAZ; i.e., 110±10–60 °C) in the Late Jurassic-Late Cretaceous and in the late Cenozoic, respectively. Late Jurassic-Late Cretaceous cooling corresponding to denudation of 1.5–5.9 km has been related to wrench tectonics along the Elbe Zone during Triassic-Jurassic Pangea breakup. Late Cenozoic exhumation of 2.1–5.6 km, and the increase of the geothermal gradient from 17±5 °C km^–1 (Oligocene/Miocene) to 25–27 °C km^–1 (recent) is likely connected to the formation of the Eger Graben starting from the Oligocene, as a result of the late Alpine orogenic phases.     

Relict non-glacial surfaces in formerly glaciated landscapes

Relict non-glacial surfaces occur within many formerly glaciated landscapes and contain important information on past surface processes and long-term landscape evolution. Relict non-glacial surfaces are distinguishable from glacial surfaces by large-scale morphologies, including rounded summits, fluvial valleys, and cryoplanation terraces and pediments, and the presence of tors, blockfields, and/or saprolites. Preservation during glaciation occurs either through coverage by non-erosive, cold-based, ice or as nunataks. Although surface morphologies and denudation rates indicate a continuous non-glacial surface history since preglacial times, relict non-glacial surfaces are dynamic features that have evolved during the Quaternary. Depending on spatial variables such as lithology, slope, regolith depth and the abundance of fine matrix and water some surfaces are denuding very slowly, while others display more rapid denudation. High spatial variability in denudation rates results in changing surface morphologies over time. Denudation rates also display high temporal variability, with much surface evolution having perhaps occurred soon after the initial onset of glaciation or during paraglacial phases. While some parts of non-glacial landscapes are currently active, others may be largely inactive relicts of past higher energy regimes. Although non-glacial surfaces are dynamic much remains to be determined regarding surface denudation rates and the magnitude of morphological changes over time.     

Sediment production and transport from in situ-produced cosmogenic 10Be and river loads in the Napo River basin,an upper Amazon tributary of Ecuador and Peru

Cosmogenic nuclide-based denudation rates and published erosion rates from recent river gauging in the Napo River basin (Peruvian Amazonia) are used to decipher erosion and sedimentation processes along a 600 km long transect from the headwaters to the lowlands. The sediment-producing headwaters to the Napo floodplain are the volcanically active Ecuadorian Andes, which discharge sediment at a cosmogenic nuclide-based denudation rate of 0.49 ± 0.12 mm/yr. This denudation rate was calculated from an average ¹⁰Be nuclide concentration of 2.2 ± 0.5 × 10⁴ at/g_(Qz) that was measured in bedload-derived quartz. Within the Napo lowlands, a significant drop in trunk stream ¹⁰Be nuclide concentrations relative to the Andean hinterland is recorded, with an average concentration of 1.2 ± 0.5 × 10⁴ at/g_(Qz). This nuclide concentration represents a mixture between the ¹⁰Be nuclide concentration of eroded floodplain deposits, and that of sediment eroded from the Andean hinterland that is now carried in the trunk stream. Evidence for addition of sediment from the floodplain to the trunk stream is provided by published decadal-scale sediment flux measurements from gauging stations operated in the Napo basin, from which an increase from 12 × 10⁶ t/yr at the outflow of the Andes to ～47 × 10⁶ t/yr at the confluence with the Solimões (upper Amazon River) is recorded. Therefore, approximately 35 × 10⁶ t of floodplain sediment are added annually to the active Napo trunk stream. Combined with our nuclide concentration measurements, we can estimate that the eroded floodplain deposits yield a nuclide concentration of ～0.9 × 10⁴ at/g_(Qz) only. Under steady state surface erosion conditions, this nuclide concentration would translate to a denudation rate of the floodplain of ～0.47 mm/yr. However, we have no geomorphologic explanation for this high denudation rate within the low relief floodplain and thus suggest that this low-nuclide concentrated sediment is Andean-derived and would have been deposited in the floodplain at a time when erosion rates of the Andes were elevated. Therefore, the recently eroded floodplain sediment provides an Andean “paleo denudation rate” of 1.2 mm/yr that was calculated for high Andean production rates. A likely period for elevated erosion rates is the LGM, where climate and vegetation cover of the Andes differed from that of the Holocene. A possible cause for the erosion of the floodplain is the tectonic uplift of the Eastern Andes, which progressively shifts the Napo River northwards. Hence, the river cuts into ancient lowland sediment, which is admixed to the Andean sediment carried in the main Napo River.     

中国阿尔泰山流域侵蚀速率及其控制因素

流域侵蚀速率的时空变化对于理解活动造山带的地貌演化具有重要意义。以阿尔泰山8个山地流域为研究对象,利用1964—2011年的水文数据,采用河流输沙量法估算了年代际山地流域侵蚀速率。首先确定悬移质、推移质和溶解质对河流输沙量的贡献,然后计算各流域的年代际侵蚀速率,并结合已有研究结果,探讨了阿尔泰山流域侵蚀速率的时空特征及其控制因素。结果表明：阿尔泰山8个山地流域的平均侵蚀速率为0.03 mm·a^-1,其中乌伦古河山地流域侵蚀速率最小（0.01 mm·a^-1）,额尔齐斯河支流克兰河山地流域侵蚀速率最大（0.05 mm·a^-1）。进一步对侵蚀速率与气候、地形、岩性、构造和植被等因素进行相关分析,发现流域侵蚀速率与地形因子（流域面积、地形起伏度）和气候因子（径流深度、平均温度）的相关性较强,表明这些因素可能对阿尔泰山山地流域侵蚀起主要影响。与阿尔泰山百万年尺度的剥蚀速率（0.07~0.3 mm·a^-1）相比,研究时段内的流域侵蚀速率偏低,这表明中亚地区晚新生代持续的干旱气候可能制约了阿尔泰山地表侵蚀。     

The impact of diamond extraction on natural denudation rates in the Diamantina Plateau (Minas Gerais,Brazil)

The ¹⁰Be method was used to investigate the effect of mining activities on the natural denudation rates in alluvial sediments from catchments of the Southern Espinhaço Range (SER) in Minas Gerais State (Brazil). In this region, which is predominantly composed of quartzites, the ¹⁰Be concentrations were measured in alluvial sediments from catchments in a preserved natural area of the Serra do Cipó National Park and on the Diamantina Plateau, which was subjected to diamond extraction from beginnings of XVIII century until the end of the XX. Two types of drainage were identified in the Diamantina Plateau area: (i) reworked drainage (alluvial sediments reworked by panning) and (ii) overloaded drainage (alluvial sediments originating from panning processes on saprolites located upstream). The mean denudation value for the natural drainages (∼4.4 m.My-1) is similar to that of the reworked drainages (∼4.3 m.My-1) However, the denudation rates obtained for eleven samples from three sites in overloaded basins range from ∼6.4 m My-1 to ∼22.8 m My-1 and are thus higher than those determined for the reworked and natural basins. These results show that despite the alluvium deposits have been intensely reworked by panning, the values of denudation rates were not changed, they are similar to denudation rates from the natural drainages. However, the natural rates are lower than those affected by panning processes on saprolites.     

Measuring alluvial fan sensitivity to past climate changes using a self‐similarity approach to grain‐size fining,Death Valley,California

The effects of climate change on eroding landscapes and the terrestrial sedimentary record are poorly understood. Using mountain catchment–alluvial fan systems as simple analogues for larger landscapes, a wide range of theoretical studies, numerical models and physical experiments have hypothesized that a change in precipitation rate could leave a characteristic signal in alluvial fan sediment flux, grain size and down‐system fining rate. However, this hypothesis remains largely untested in real landscapes. This study measures grain‐size fining rates from apex to toe on two alluvial fan systems in northern Death Valley, California, USA, which each have well‐exposed modern and ca 70 ka surfaces, and where the long‐term tectonic boundary conditions can be constrained. Between them, these surfaces capture a well‐constrained temporal gradient in climate. A grain‐size fining model is adapted, based on self‐similarity and selective deposition, for application to these alluvial fans. This model is then integrated with cosmogenic nuclide constraints on catchment erosion rates, and observed grain‐size fining data from two catchment‐fan systems, to estimate the change in sediment flux from canyon to alluvial fan that occurred between mid‐glacial and modern interglacial conditions. In a fan system with negligible sediment recycling, a ca 30% decrease in precipitation rate led to a 20% decrease in sediment flux and a clear increase in the down‐fan rate of fining, supporting existing landscape evolution models. Consequently, this study shows that small mountain catchments and their alluvial fan stratigraphy can be highly sensitive to orbital climate changes over <10⁵ year timescales. However, in the second fan system it is observed that this sensitivity is completely lost when sediment is remobilized and recycled over a time period longer than the duration of the climatic perturbation. These analyses offer a new approach to quantitatively reconstructing the effects of past climate changes on sedimentation, using simple grain‐size data measured in the field.     

Determining the groundwater potential recharge zone and karst springs catchment area: Saldoran region,western Iran

Assessing the groundwater recharge potential zone and differentiation of the spring catchment area are extremely important to effective management of groundwater systems and protection of water quality. The study area is located in the Saldoran karstic region, western Iran. It is characterized by a high rate of precipitation and recharge via highly permeable fractured karstic formations. Pire-Ghar, Sarabe-Babaheydar and Baghe-rostam are three major karstic springs which drain the Saldoran anticline. The mean discharge rate and electrical conductivity values for these springs were 3, 1.9 and 0.98 m³/s, and 475, 438 and 347 μS/cm, respectively. Geology, hydrogeology and geographical information system (GIS) methods were used to define the catchment areas of the major karstic springs and to map recharge zones in the Saldoran anticline. Seven major influencing factors on groundwater recharge rates (lithology, slope value and aspect, drainage, precipitation, fracture density and karstic domains) were integrated using GIS. Geology maps and field verification were used to determine the weights of factors. The final map was produced to reveal major zones of recharge potential. More than 80 % of the study area is terrain that has a recharge rate of 55–70 % (average 63 %). Evaluating the water budget of Saldoran Mountain showed that the total volume of karst water emerging from the Saldoran karst springs is equal to the total annual recharge on the anticline. Therefore, based on the geological and hydrogeological investigations, the catchment area of the mentioned karst springs includes the whole Saldoran anticline.     

Late Miocene to Quaternary slip history across the Qiulitag anticline in the southern Tianshan piedmont

In this study, we reconstruct the Miocene to Quaternary shortening history across the Qiulitag anticline, a complex fault‐bend fold located in southern Tianshan. We studied the Yaha and Kuche sections, where we combined surface structural measurements and seismic imaging to model the stratigraphic horizons. The history of folding was reconstructed based on magnetostratigraphic analyses and eight cosmogenic burial ages in Kuche. Pleistocene deformation rates were also quantified in Yaha based on a deformed fluvial terrace that we dated to ~67 ka using a cosmogenic depth profile. Our results suggest that the fold grew at a mean slip rate of 0.9–1.3 mm/a in both sections but accelerated to ~2.5 mm/a during the Pleistocene in Kuche. These results support a migration of the deformation towards the basin during the Pleistocene and suggest that most of the present deformation in the Tianshan is accommodated across the external structures of the range.     

Paraglacial sedimentation and denudation processes in an Alpine valley of Switzerland. An approach to the quantification of sediment budgets

Abstract

As a result of recent drillings in the Walensee Valley (eastern Switzerland) a new facies model for the Quaternary filling of Alpine valleys has been developed. A detailed lithological model and some new radiocarbon dating allowed the calculation of regional sedimentation and denudation rates and their change during the Late- and Postglacial period. It is shown that these changes follow the paraglacial sedimentation model by Church and Ryder [1]. The absolute quantification of the sediment budgets between the Last Glaciation and today points to denudation rates in the order of 1.5 mm y^?1 for the catchment of the Lake of Walenstadt. This is 50 % higher than suggested from current tectonic and isostatic estimates up to now. In that case present day uplift of the Alps would not be in balance with denudation. © Elsevier, Paris     

Recent insights into the dissolved and particulate fluxes from the Himalayan tributaries to the Ganga River

The Ganga River plays a major role in the transfer of materials from the Indian sub-continent to the Bay of Bengal, both in dissolved and particulate forms. To understand the present elemental dynamics of the Ganga River system, it is important to assess the hydrogeochemical contribution of its tributaries. In this paper, we present an updated database on dissolved and particulate fluxes and denudation rates of the Himalayan tributaries of the Ganga River (Ramganga, Ghaghara, Gandak and Kosi). Dissolved trace element concentrations, their fluxes and suspended sediment-associated elemental fluxes of the Himalayan tributaries have been reported for the first time. Total dissolved flux of the Ramganga, Ghaghara, Gandak and Kosi was estimated as 4, 19.1, 10.3 and 8.8 million tons year^?1 accounting for ~?5.7, ~?27.3, ~?14.7 and ~?12.6%, respectively, of the total annual dissolved load carried by the Ganga River. The total particulate flux of the Ramganga, Ghaghara, Gandak and Kosi was computed as 8.2, 81.6, 30.9 and 19.5 million tons year^?1, respectively. Compared to earlier studies, we have found a significant increase in the total dissolved flux and chemical denudation rate of the studied tributaries. The estimated particulate fluxes were found to be low in comparison to the previous studies. We suggest that a significant increase in the dissolved fluxes and a decrease in the particulate fluxes are an indication of the increasing anthropogenic disturbances in the catchment of these tributaries.