Relative Erosion Research Articles

Soil erosion in relation to climate change and vegetation cover over the past 2000 years as inferred from the Tianchi lake in the Chinese Loess Plateau

Understanding the response of past soil erosion to climate change and human disturbances is quite essential for managing and preventing soil erosion in the future. Here, we report a high-resolution soil erosion sequence during the past 2000 years based on grain-size data from a sediment core GS07A in Tianchi Lake in the Chinese Loess Plateau. These grain-size data are analysed by end-member modelling and further deciphered by detailed modern investigations of surface sediments, surface soils, and modern dust samples aided by published grain-size distribution characteristics of different depositional provenances and processes. Six strong soil erosion periods, including more than 20 serious soil erosion events, are inferred at 150–300 CE, 450–750 CE, 900–1100 CE, 1200–1400 CE, 1650–1800 CE, and 1950–2000 CE. These soil erosion records correspond well with intensive flood events in downstream rivers and the neighbouring Longxi area documented from the historical literature, suggesting that regional high-intensity rainfall or flood events are the main cause of soil erosion. Vegetation cover in the catchment also influenced soil erosion: light vegetation cover aggravated soil erosion even in the periods with a low frequency of flooding, while heavy cover reduced soil erosion even in the periods with a high frequency of flooding. Our results highlight the role of sustainable land use and vegetation restoration around the catchment in controlling soil erosion in the Chinese Loess Plateau.

The results of water droplet erosion tests of ion-plasma coatings formed on titanium Ti-6Al-4V alloy samples manufactured by using 3D-printing and traditional technological process

The paper presents the results of erosion tests and metallographic studies of titanium alloy samples manufactured by using 3D printing and traditional technological methods without coatings and with various types of ion-plasma coatings. As a result of the tests, the kinetic curves of erosion wear of the studied alloys and coatings were obtained, showing that the best type among those considered is a DLC (Diamond Like Carbon) coating, which increases the relative erosion resistance of uncoated samples in incubation period duration of the water droplet erosion process by not less than in 1.8 times.

An analytical model for estimation of internal erosion rate

ABSTRACTEstimating erosion rate of solid particles in a porous medium is of interest to geotechnical engineers; which use analytical or numerical models for this purpose. Constitutive law of erosion is a key component in the development of such models. These models estimate the solid erosion rate as a function of various modelling parameters such as fluid velocity and time.Using the principles of dimensional analysis, a constitutive law is proposed for assessment of the rate of erosion in relation to the fluid velocity and a dimensionless proportionality constant called the erosion coefficient,. Based on physics of the erosion process, experimental observations and approximation theory, is expressed as a function of grain density, particle Reynolds number and porosity variation. Then, the proposed constitutive model is combined with the principle of conservation of mass to arrive at an analytical model for estimation of internal erosion rate.The analytical model shows that the erosion rate has a non-linear direct relationship with fluid velocity and a non-linear inverse relationship with time. The proposed analytical model is calibrated and validated using experimental data available in the literature. The validation results show that the model estimations of erosion rate can closely reproduce experimental data.

Randomised study of the effects of fluoride and time on in situ remineralisation of acid-softened enamel

ObjectivesThis single-centre, randomised, crossover study used a short-term in situ dental erosion remineralisation model to explore the remineralisation of acid-softened enamel in the 4-h period immediately following brushing with an anti-erosion, dentin hypersensitivity test dentifrice containing 1150 ppm fluoride (as sodium fluoride [NaF]) or a placebo dentifrice with no fluoride.Materials and methodsFifty participants wearing a palatal appliance holding surface-softened bovine enamel specimens brushed their natural teeth with their assigned dentifrice. Specimens were removed at 5-, 10-, 15-, 30-, 60-, 120- and 240-min post brushing. Enamel remineralisation effect was evaluated at each timepoint by percent surface microhardness recovery (%SMHR) and enamel fluoride uptake (EFU). After a second in vitro erosive challenge, the percent relative erosion resistance (%RER) was calculated.ResultsStatistically significant differences in %SMHR were observed for the test dentifrice compared with the placebo dentifrice from the 60-min timepoint onwards (all p < 0.02; mean difference of 8.66 [95% CI 3.46, 13.87] at 60 min). At each specimen removal time, %RER and EFU were statistically significantly higher for the test dentifrice compared with the placebo dentifrice (p < 0.0001 for all). No treatment-related or serious adverse events were reported.ConclusionsThe NaF-containing anti-erosion, dentin hypersensitivity dentifrice improved remineralisation of acid-softened enamel starting at 60 min of intra-oral exposure. It also improved enamel erosion resistance and fluoride uptake as early as 5 min after exposure to fluoridated dentifrice slurry.Clinical relevanceBrushing with a NaF-containing dentifrice can rapidly improve remineralisation, enamel erosion resistance and fluoride uptake.

Mississippi river sediment diversions and coastal wetland sustainability: Synthesis of responses to freshwater, sediment, and nutrient inputs

Management and restoration of coastal wetlands require insight into how inundation, salinity, and the availability of mineral sediment and nutrients interact to influence ecosystem functions that control sustainability. The Mississippi River Delta, which ranks among the world's largest and most productive coastal wetland complexes, has experienced extensive deterioration over the last century due, in large part, to enhanced vulnerability to relative sea-level rise and lateral erosion caused by a combination of natural processes and anthropogenic modifications of hydrology. This land loss crisis has prompted the State of Louisiana to develop a comprehensive restoration plan that includes constructing and implementing a series of large-scale sediment diversions that will reconnect sediment- and nutrient-rich Mississippi River water to adjacent bays, estuaries, and wetlands. Sediment loading through diversions is predicted to enhance the long-term sustainability of coastal wetlands; however, the additive effects of increased inundation, abrubt changes in the salinity regime, and high nutrient loads on wetland plant growth and organic matter (SOM) decomposition rates, which help regulate accretion and elevation change, is uncertain. Therefore, this review attempts to synthesize existing information to inform predictions of the interactive effects of diversions on these drivers of coastal wetland sustainability. The data suggest that sediment deposition within an optimal elevation range will increase the overall productivity of existing wetlands where prolonged flooding does not counter this effect by limiting plant growth. A reduction in salinity may increase plant productivity and cause vegetation shifts to less salt tolerant species, but seasonal swings in salinity may have unforeseen consequences. Nutrient-loading is predicted to lead to greater aboveground productivity, which, in turn, can facilitate additional sediment trapping; however, belowground productivity may decline, particularly in areas where sediment deposition is limited. In areas experiencing net deposition, nutrient-enrichment is predicted to enhance belowground growth into new sediment and contribute to positive effects on soil organic matter accumulation, accretion, and elevation change. Thus, we contend that sediment input is essential for limiting the negative effects of flooding and nutrient-enrichment on wetland processes. These conclusions are generally supported by the biophysical feedbacks occurring in existing prograding deltas of the Mississippi River Delta complex.

Shoreline Evolution of Lagoon Sandy Spits and Adjacent Beaches, Lagoa dos Patos, Brazil

The development of lagoon sandy spits is dependent on sediment supply (mainly through longshore transport) and is often related to erosion of updrift beaches under high-angle waves. This paper provides an understanding of the short- to medium-term shoreline evolution of three symmetrical lagoon sandy spits and the related erosion of the adjacent bay beaches of Lagoa dos Patos, Brazil. To do so, two of the most widely used methods to quantify shoreline changes were applied: the transects-from-baseline method and the change polygon method. A historical analysis of the shoreline movement of approximately three decades (1984–2013), was carried out, aiming to track the source of sediments to the spits. Alternate phases of shoreline stability, deposition, and recession (less frequent) in short time intervals (years) showed correlation with the El Nino–Southern Oscillation and Southern Annular Mode indexes. Shoreline stability along beaches in the medium term (60.4% of Arambare and 73.9% of Graxaim beaches, by the linear regression rate calculation), together with the very low average shoreline change rate of +0.7 m y–1 found using both methods, demonstrates that the sediment supply to the spits has been significantly reduced in the past three decades. Furthermore, the large-scale subaqueous portions of the spits are under wave-induced sedimentary reworking accompanied by the up-building of sandbanks from the submerged bars, followed by its landward migration and merging to the spit's shoreline. These results suggest that the spits of Lagoa dos Patos have their growth limited once the amount of sediment supply has been significantly reduced.

Land Degradation by Soil Erosion in Nepal: A Review

Land degradation, particularly soil erosion, is currently a major challenge for Nepal. With a high rate of population growth, subsistence-based rural economy, and increasingly intense rainfall events in the monsoon season, Nepal is prone to several forms of land degradation, such as floods, landslides, and soil erosion. To understand the causes, impacts, and possible management options for soil erosion, a review on the causal factors, status, and amelioration measures for land degradation in Nepal was conducted based on recent information available in national and international journals and grey literature. Intense rainfall and conventional tillage practices coupled with poor soil structure and steep slopes are the main drivers of soil erosion. Soil erosion leads to losses in soil and crop productivity, pollution of land and water resources, and a loss of farm income. Strategies to manage erosion include mulching, cover cropping, contour farming, strip cropping, and conservation agriculture practices, along with bioengineering techniques. Land degradation issues are a prime policy focus in Nepal, including national three- and five-year plans. However, these policies have been generally ineffective in reducing soil erosion, landslides, and floods in relation to the set targets. Realistic plans need to be formulated in Nepal focusing more on capacity enhancement and local participation to actively influence land-degradation processes.

Evaluation of Effect of Different Crop Types On Soil Water Erosion: Case Study of the Myjava Hill Land, Slovakia

The main objective of the study is to model and evaluate the effect of different types of crops on soil water erosion by using the physically-based EROSION-3D model. The EROSION-3D model is based on physical principles and simulates surface runoff, erosion, the deposition of material, and the detachment of soil particles for a single rainfall event. The erosion model was applied to a small catchment of Svacenicky Creek (6.86 km2), which is situated in the Myjava Hill Land in the western part of Slovakia; it is known for its quick runoff responses and related erosion processes. The parts most prone to erosion processes are located in the northern part of the Svacenicky Creek catchment on slopes with a more than 20% angle. Three crop types (winter wheat, silage corn and sugar beets) were chosen in consideration of their growing periods in order to assess the dynamic character of the erosion processes, especially during the growing period of each single crop. The modelling was performed for design rainfall events that were derived separately for each month and which were inputs to the model according to the growing period of the selected crops; six scenarios of the initial soil moisture in a range of 10-40% were designed. The results demonstrated the differences between the erosive effects of the crops selected during their growing periods. Finally, the results were statistically evaluated to determine the differences between the various scenarios of the initial moisture, different rainfall events, and selected crop types.

Long-term erosion of the Nepal Himalayas by bedrock landsliding: the role of monsoons, earthquakes and giant landslides

Abstract. In active mountain belts with steep terrain, bedrock landsliding is a major erosional agent. In the Himalayas, landsliding is driven by annual hydro-meteorological forcing due to the summer monsoon and by rarer, exceptional events, such as earthquakes. Independent methods yield erosion rate estimates that appear to increase with sampling time, suggesting that rare, high-magnitude erosion events dominate the erosional budget. Nevertheless, until now, neither the contribution of monsoon and earthquakes to landslide erosion nor the proportion of erosion due to rare, giant landslides have been quantified in the Himalayas. We address these challenges by combining and analysing earthquake- and monsoon-induced landslide inventories across different timescales. With time series of 5 m satellite images over four main valleys in central Nepal, we comprehensively mapped landslides caused by the monsoon from 2010 to 2018. We found no clear correlation between monsoon properties and landsliding and a similar mean landsliding rate for all valleys, except in 2015, where the valleys affected by the earthquake featured ∼5–8 times more landsliding than the pre-earthquake mean rate. The long-term size–frequency distribution of monsoon-induced landsliding (MIL) was derived from these inventories and from an inventory of landslides larger than ∼0.1 km2 that occurred between 1972 and 2014. Using a published landslide inventory for the Gorkha 2015 earthquake, we derive the size–frequency distribution for earthquake-induced landsliding (EQIL). These two distributions are dominated by infrequent, large and giant landslides but under-predict an estimated Holocene frequency of giant landslides (&gt; 1 km3) which we derived from a literature compilation. This discrepancy can be resolved when modelling the effect of a full distribution of earthquakes of variable magnitude and when considering that a shallower earthquake may cause larger landslides. In this case, EQIL and MIL contribute about equally to a total long-term erosion of ∼2±0.75 mm yr−1 in agreement with most thermo-chronological data. Independently of the specific total and relative erosion rates, the heavy-tailed size–frequency distribution from MIL and EQIL and the very large maximal landslide size in the Himalayas indicate that mean landslide erosion rates increase with sampling time, as has been observed for independent erosion estimates. Further, we find that the sampling timescale required to adequately capture the frequency of the largest landslides, which is necessary for deriving long-term mean erosion rates, is often much longer than the averaging time of cosmogenic 10Be methods. This observation presents a strong caveat when interpreting spatial or temporal variability in erosion rates from this method. Thus, in areas where a very large, rare landslide contributes heavily to long-term erosion (as the Himalayas), we recommend 10Be sample in catchments with source areas &gt; 10 000 km2 to reduce the method mean bias to below ∼20 % of the long-term erosion.

Research on the Optimal Vegetation Cover for Remote Sensing Assessment of Soil Erosion Risk Using the Temporal Matching Relationship between Rainfall and Vegetation

Vegetation cover derived from remote sensing image is widely used for soil erosion risk assessment, but there is no clear guideline to select the most appropriate temporal satellite data. It is common practice that satellite data during growing season are randomly selected and used in soil erosion risk assessment. However, the effectiveness of vegetation in protecting the soil is quite different even if it is the same growing season since vegetation covers change as they grow. This article aims to provide a method of choosing optimal vegetation cover for studying soil erosion risk using remote sensing, that is, the vegetation cover in the most appropriate temporal period. Based on the temporal relationship of the two most active impact factors, rainfall and vegetation, an index of RV is developed and used to indicate the relative erosion risk during the year. The results show that annual variation of rainfall is significant, and vegetation is relatively stable, resulting in their matching relationship is different in each year. The correlation coefficient reaches 0.89 between RV and real sediment transport during the period when rainfall can cause soil erosion. In other words, RV is a good indicator of soil erosion. Therefore, there is a good correlation between RV maximum and the optimal vegetation cover, which can help facilitate erosion research in the future, showing good potential for successful application in other places.

LONG-TERM SUBSIDENCE OF BEACH NOURISHMENT AND DUNE RESTORATION IN CAMINADA HEADLANDS, COASTAL LOUISIANA

Coastal barrier islands are the first line of defense for protecting wetlands, inland bays, and mainland regions from direct effects of wind, waves, and storms. Rosati (2006) indicate that 20 to 40% of the total sand volume can be sequestered and lost from the sandy barrier island through consolidation. As a result, predicting long-term subsurface sediment consolidation is integral to determining the ability of barrier islands to provide coastal protection and resilience to future hazards, such as relative sea level rise, sediment erosion, and hurricanes. This study uses the Caminada Headlands geotechnical investigations and monitoring data to determine empirical correlations for deltaic sediment compressibility and develop a validated and calibrated consolidation and subsidence numerical model for future barrier island restoration projects. With this calibrated model, differential settlements associated with sand fill placement can be estimated to design placement elevations to maintain post-construction topography for ecological habitat and restoration requirements and can be used for future beach restoration projects along barrier island shorelines.

Evaluation of watershed health using Fuzzy-ANP approach considering geo-environmental and topo-hydrological criteria

Assessment of watershed health and prioritization of sub-watersheds are needed to allocate natural resources and efficiently manage watersheds. Characterization of health and spatial prioritization of sub-watersheds in data scarce regions helps better comprehend real watershed conditions and design and implement management strategies. Previous studies on the assessment of health and prioritization of sub-watersheds in ungauged regions have not considered environmental factors and their inter-relationship. In this regard, fuzzy logic theory can be employed to improve the assessment of watershed health. The present study considered a combination of climate vulnerability (Climate Water Balance), relative erosion rate of surficial rocks, slope weighted K-factor, topographic indices, thirteen morphometric characteristics (linear, areal, and relief aspects), and potential non-point source pollution to assess watershed health, using a new framework which considers the complex linkage between human activities and natural resources. The new framework, focusing on watershed health score (WHS), was employed for the spatial prioritization of 31 sub-watersheds in the Khoy watershed, West Azerbaijan Province, Iran. In this framework, an analytical network process (ANP) and fuzzy theory were used to investigate the inter-relationships between the above mentioned geo-environmental factors and to classify and rank the health of each sub-watershed in four classes. Results demonstrated that only one sub-watershed (C15) fell into the class that was defined as ‘a potentially critical zone’. This article provides a new framework and practical recommendations for watershed management agencies with a high level of assurance when there is a lack of reliable hydrometric gauge data.

A global erodibility index to represent sediment production potential of different rock types

Erosion drives landscape evolution and is fundamental for understanding the interplay between climate and tectonics as well as land-ocean matter fluxes. Large scale erosion models are an important part of the suite of Earth system models. However, their representation of the sediment production potential of different rock types is very limited. A new global erodibility index is proposed herein. It depicts the relative erosion potential of different lithological classes in the Global Lithological Map (GLiM). The erodibility index was developed by correlating observational hillslope data against climatic and tectonic setting. Hillslope data were compared for different lithological classes in regions of similar uplift across a range of landscapes. An erodibility index was defined for each lithological class, based on the relative hillslope compared to that of acid plutonic rocks in the respective area, which are here used as base lithology. The erodibility indices of different lithological classes fall within three groups: low erodibility - 1.0 for acid plutonic rocks, metamorphic rocks, and carbonate sedimentary rocks, 1.1 for acid volcanic rocks, 1.2 for mixed sedimentary rocks; medium erodibility - 1.5 for basic plutonic rocks and siliciclastic rocks of all grain sizes, 1.4 for basic volcanic rocks; high erodibility – 3.2 for unconsolidated sediments. This erodibility index is the first estimate of sediment production potential of different rock types aimed at regional to global scale application. The erodibility index presented here can help improve our understanding of global erosion and landscape evolution. A new lithology erodibility layer, the global erodibility index dataset (GEroID), is produced and used as input in a global sediment flux model (WBMsed) to demonstrate a potential utilization of the new dataset. Using an updated lithological map paired with the new erodibility index yields improved regional model results compared to the original model input.

A review on rain erosion protection of wind turbine blades

Surface erosion of wind turbine blades, which are a key component of wind turbines, plays an important role in reducing the output power and service life of the blades. Rain erosion is also detrimental to wind turbine blades. In this review, the research progress on rain erosion is analyzed from the aspects of protection technology, rain erosion mechanism and related rain erosion tests and simulations. A comprehensive protective coating can be obtained by modifying or combining resins with different properties. Investigation of the rain erosion mechanism should consider the influence of the acidity of rain on the organic coatings. The rain erosion device should be more in line with the natural environment, and the dual structure of the substrate composite and surface coating of the blades should be fully considered as well in the rain erosion simulation.

Does Pebble Abrasion Influence Detrital Age Population Statistics? A Numerical Investigation of Natural Data Sets

AbstractPebble abrasion is a key factor controlling the release of minerals into sand, but few attempts have been made to model how it could influence the liberation of minerals into the size fraction used in detrital geochronology. We perform a series of experiments with an abrasion model to test this influence using natural and synthetic data sets. Our results demonstrate that pebble abrasion can change the zircon mixing proportions of upstream source units as well as the age distribution of mixed fluvial sands. This change is particularly significant when there is strong contrast in rock resistance within the watershed. Pebble abrasion is one of many factors that can change the mixing proportion of sands, including hillslope gravel supply, erosion rates, and mineral fertility. In our study case (Marsyandi watershed, Himalaya), the abrasion model predicts age distributions that are statistically indistinguishable from those predicted by a no‐abrasion model. However, the relative erosion rates estimated by our model largely differ from the results of a no‐abrasion model and are closer to those from other studies that suggest a strong correlation between modern erosion rates, tectonics, and precipitation intensity in the Marsyandi watershed. These findings highlight that, even in cases where there is no statistical evidence of change between the modeled age distributions, abrasion can affect the erosion rates estimated from them. Therefore, quantifying the influence of abrasion on sand production is an essential step not only to predict mixing proportions but also to accurately retrieve erosion rates from the measured grain age distributions.

Performance evaluation of alumina trihydrate and silica-filled silicone rubber composites for outdoor high-voltage insulations

In recent years, silicone rubber-based composites have been widely investigated for outdoor applications due to their promising insulating properties. However, mechanical, thermal, and tracking properties of pure silicone rubber are very poor, which restrains its application for long-term performance. In this research work, the influence of microsized alumina trihydrate (ATH) and micro/nanosized silica (SiO$_{2})$ fillers on mechanical, thermal, and electrical properties of room temperature vulcanized silicone rubber (RTV-SiR) has been studied. SiR-blends with varying amounts of ATH and SiO$_{2}$ particles were prepared by blending in a two-roll mixing mill, compression molding, and postcuring processes in sequence. In order to evaluate relative tracking and erosion resistance of SiR-blends, an inclined plane test (IPT) was conducted in accordance with the ASTM D2303 standard procedure. Surface temperature distribution was recorded using a Fluke-Ti25 infrared camera during IPT experiments. Thermogravimetric analysis was carried out to analyze the thermal stability of ATH and silica-filled silicone rubber samples. Tensile strength, percent elongation at break, hardness, erosion, tracking resistance, and thermal properties were also investigated and discussed. Results showed that the mechanical, thermal, tracking, and erosion performances of SiR-blends are improved by the incorporation of ATH and silica particles, which is governed by filler type, size, and wt. % in the polymer matrix.

Variability of Surface Erosion and Particle Size Distribution in Relation to Slope Aspect and Gradient in a Semi-Arid Region in West of Zanjan

Variability of Surface Erosion and Particle Size Distribution in Relation to Slope Aspect and Gradient in a Semi-Arid Region in West of Zanjan

Rain erosion resistance of injection moulded and compression moulded polybutylene terephthalate PBT

Offshore wind turbine rotor diameters still increase. Blade tip velocities are up to 110 m/s, giving rise to more severe raindrop impact conditions and related erosion of the wind turbine blades. In the current work droplet impingement erosion tests were performed for injection moulded and compression moulded polybutylene terephthalate PBT. The measured incubation periods were compared to an extended and improved fatigue based erosion model.The developed erosion test set-up was based on a high water pressure nozzle system spraying water drops at a stationary PBT surface. Model results with thermoplastic materials simulating heavy rain conditions with a droplet size of 1.8 mm and an impact velocity of 120 m/s are shown. Model results with PBT materials simulating the used test conditions are shown and compared with the measured incubation periods. Although a reasonable similarity between test results and model calculations for the injection moulded PBT was found, the absolute value of the incubation period predicted by the model for compression moulded PBT differed substantially. This probably resulted from the lower confidence level of the S-N curve for the compression moulded PBT. The droplet impingement measurements and model predictions both showed a substantially higher incubation period for injection moulded PBT compared to compression moulded PBT.

CONSTRUCTION OF SLURRY JET EROSION TESTER AND THE EFFECT OF PARTICLE SIZE ON SLURRY EROSION

A Jet erosion tester is designed and used to study the relative erosion behavior of high chromium white cast iron (ASTM 532A) at specific concentration of silica sand as an abrasive material, 45° impact angle and two size of abrasive particles. A slurry pot was used which contains two propellers rotated at the speed required for uniform distribution. The test specimens are mounted on test fixture which is fixed and has a provision to move in different angular position to find out the wear for different angles. Two different experiments are conducted preliminarily by using silica sand as abrasive with particle size of 400-600 µm and 600-800 µm. Impact angle of 45° and solid abrasives of 20% wt. concentration are used as fixed parameters for 10 hours. It was found that the erosion resistance decreases with increasing the abrasive particle size.

Downstream evolution of the thermochronologic age signal in the Brahmaputra catchment (eastern Himalaya): Implications for the detrital record of erosion

The Namche Barwa massif in the eastern Himalayan syntaxis is characterized by very rapid exhumation and provides a significant proportion of the sediment flux carried by the Brahmaputra River. We present new detrital zircon fission-track (ZFT) and muscovite 40Ar/39Ar (MAr) data from modern sediments of rivers draining the eastern Himalaya. The cooling-age populations for both thermochronometers contain a characteristic <2 Ma signature related to the rapid exhumation of Namche Barwa, which can be traced hundreds of kilometers downstream from their source into the Brahmaputra foreland, despite dilution from downstream tributary catchments. To estimate present-day erosion in the catchments, we apply a mixing model based on linear inversion of the binned age distributions. The inversion predicts relative erosion rates in the syntaxial region that are an order of magnitude higher than those in upstream catchments, and about twice as high as those in the southern Himalayan catchments, consistent to first order with previous estimates of erosion-rate patterns in the eastern Himalaya. A comparison of the observed downstream evolution of age distributions with a sediment-flux model suggests that the ZFT signal can be explained by dilution from Himalayan tributaries only, whereas the MAr signal is also affected by selective sequestering (possibly through winnowing) of micas as they are transported downstream. Nevertheless, thermochronological ages <2 Ma provide a diagnostic signal of syntaxial exhumation in the sedimentary record of the eastern Himalaya; this study suggests the most robust signal to be recorded in the most proximal deposits with respect to the syntaxis.