Steady-state Erosion Research Articles

Erosion behaviour of HVOF sprayed WC.Co-NiCrAlYSi (35%-65%) coatings

In the present study, WC.CO-NiCrAlYSi(35%-65%) cermet coatings were deposited on a Fe-based super alloy designated as SS316 (Midhani Grade) to reduce the damage caused by erosion boiler applications. Erosion studies were conducted on uncoated as well as HVOF coated steels. The erosion experiments were carried out using an air-jet erosion test rig according to ASTM G-76 standard at a velocity of 30 m/s and at different impingement angles of 30°, 60° and 90°. Alumina particles of size ranging between 50 and 80 μm were used as erodent. Analysis of weight-loss data and Volumetric steady state erosion rates for different coatings and substrate alloys are evaluated. The bare SS316 steel followed ductile erosion mode where as WC.CO-NiCrAlYSi(35%-65%) coating exhibited brittle behaviour respectively. Selection and/or Peer-review under responsibility of The First Materials Research Society of Thailand International Conference.

Improvement of solid particle erosion resistance of helicopter rotor blade with hybrid composite shield

In the present study, the solid particle erosion behavior of polyurethane (PU) tape (3M-8663) material, bidirectional carbon fiber reinforced epoxy (CF/EP) and glass fiber reinforced epoxy (GF/EP) composites has been characterized experimentally and numerically. In the experimental part, steady-state erosion rates of aforementioned materials have been evaluated at different impact angles (20°, 30°, 45°, 60°, and 90°) and different impact velocities (70, 110, 150, and 190 m/s), and compared with those of stainless steel (SS304) and pure nickel materials (Ni) which are commonly used for erosion shield of helicopter rotor blades. Tests were conducted at room temperature using silica (SiC) particles (average diameter of 175 µm) as an erodent. Erosion behaviors on the shield surface of the same materials were investigated numerically under different impact velocities (110, 150, 190, and 230 m/s) for a pitch angle of 0°. Numerical erosion simulations were realized with commercial ANSYS-Fluent software using the finite volume method, an erosion model, and a discrete phase method with the Eulerian-Lagrangian approach. The experimental results showed that the GF/EP and the CF/EP composites indicated the maximum erosion rate at the impact angles ranged from 60° to 90°, whereas the PU tape material exhibited the maximum erosion rate at the impact angle of 30°. The results also showed that the PU tape surface clearly provided much better erosion resistance than the GF/EP and CF/EP composite surfaces, and the hybrid erosion shield having the PU/SS304 surface significantly improved the erosion resistance of the helicopter rotor blade up to the impact velocity of 150 m/s. A good agreement was also observed between the experimental and the numerical results.

Valley formation on early Mars by subglacial and fluvial erosion

The southern highlands of Mars are dissected by hundreds of valley networks, which are evidence that water once sculpted the surface. Characterizing the mechanisms of valley incision may constrain early Mars climate and the search for ancient life. Previous interpretations of the geological record require precipitation and surface water runoff to form the valley networks, in contradiction with climate simulations that predict a cold, icy ancient Mars. Here we present a global comparative study of valley network morphometry, using a principal-component-based analysis with physical models of fluvial, groundwater sapping and glacial and subglacial erosion. We found that valley formation involved all these processes, but that subglacial and fluvial erosion are the predominant mechanisms. This is supported by predictions from models of steady-state erosion and geomorphological comparisons to terrestrial analogues. The inference of subglacial channels among the valley networks supports the presence of ice sheets that covered the southern highlands during the time of valley network emplacement. Some valleys in the southern highlands of Mars may have formed by subglacial erosion, consistent with a cold and icy early Mars, according to a statistical analysis of valley morphometry.

Model for hydrogen accumulation in co-deposited layers

• A model for predicting hydrogen accumulation in co-deposited layers was developed. • The model was successfully verified in regards to the role of substrate temperature for W-D, Mo-D, Al-D co-deposition. • The model was tested against empirical scaling equations for W-D co-deposition. An improved diffusion based model for prediction of the hydrogen content in co-deposited layers depending on the deposition conditions (the properties of the material which is co-deposited with hydrogen, rate of deposition, hydrogen flux and particle energy, substrate temperature) is presented. The model is validated using experimental data for W, Mo and Al, and is compared to empirical scaling equations currently in use. It is shown that a good agreement is observed in regards to hydrogen content vs substrate temperature experimental data, and no disagreement with scaling equations can be seen in regards to the role of hydrogen flux and the rate of deposition. It is shown that the influence of hydrogen particle energy on the hydrogen content requires further investigation. In addition to hydrogen, models for other mobile impurities both in co-deposited layers and in layers under steady-state net erosion conditions are given.

Experimental study of detachment density threshold in L-mode plasmas on EAST

One of the critical challenges for long pulse operation of ITER and future fusion reactors is the excessively high heat and particle fluxes on the divertor targets. The divertor detachment offers an effective way for the control of steady state heat flux and erosion at the divertor target. Dedicated experiments have been systematically performed for both H-mode and L-mode plasmas on EAST with ITER-like W divertor in the last two years to further advance detachment physics understanding. The detachment is identified by the rollover of divertor peak particle flux near the strike point during the density ramping up, which correlates with the reduction of electron temperature down to 5 eV, the increase of Dδ/Dα ratio and radiated power. It has been demonstrated that the more closed divertor has a lower density threshold at the onset of detachment on EAST. Furthermore, the detachment density threshold will be reduced when the strike point moves towards the divertor corner. The onset of detachment exhibits a strong asymmetry between inner and outer targets, with the inner target accessing detachment at lower density due to the lower electron temperature, as expected. The effects of the heating power and plasma current on the detachment onset were also investigated. The experimental results show that the density at detachment onset is lower in L-mode relative to H-mode, and increases with the heating power. The detachment density threshold normalized to the Greenwald density limit is lower at a high plasma current.

Numerical Simulation of Solid Particle Erosion of Epoxy by Overlapping Angular Particle Impacts

The solid particle erosion of polymers occurs in a wide variety of industries and has been extensively studied experimentally. However, numerical models capable of accurately simulating the associated material removal mechanisms and predicting erosion rate do not yet exist. In this paper, a coupled smoothed particle hydrodynamics (SPH)/finite element (FE) model was developed to simulate the erosion of an epoxy by successive overlapping impacts of angular 22 µm, 97 µm and 152 µm silicon carbide particles at various angles of attack. The epoxy was modeled using a strain-rate-dependent elastic–plastic material model that fails at a critical plastic strain. It was found that, once the critical plastic strain was calibrated using a single experiment, the numerical model could predict both the length of the incubation period and the steady-state erosion rate to within 6% and 11%, respectively, of the measured values. It was found that fundamental material removal mechanisms such as cutting, ploughing and the accumulation of plastic deformation due to multiple overlapping impacts were all successfully simulated. Overall, it has been demonstrated that numerical models can be used to investigate the effect of influential parameters on the solid particle erosion of a polymer. This may have important implications for the development of effective methods to improve the erosion resistance of polymers.

Erosion behaviour of boiler component materials at room temperature and 400 °C temperature

Degradation of boiler tube components in Indian thermal power plants is mainly done through solid particle erosion due to exposure in erosive ash environment. Some important parameter such as hardness, erodent velocity, temperature, impact angle, shape and size are majorly affected the erosion wear. In this study, the erosion wear behaviour of SAE 208 grade steel, SAE213-T12 boiler steel, SAE213-T91 boiler steel and IS 2062 structural steel were investigated using an air jet erosion test rig. The erosion tests were carried out at the impact angles of 30° and 90°, impact velocity of 42.3 m/s at room temperature and 400 °C. The position of sample holder was adjusted in such a way that erosion wear scar occur at the central region of the samples. For each experiment, the erosion test was continued until the steady state erosion rate was achieved as per ASTM standard. The variation in erosion rate data has been plotted against cumulative mass of erodent for boiler and structural steel samples. The steady state erosion rates for different steel samples are calculated and compared. The surfaces of tested samples are analyzed using scanning electron microscopy to understand the erosion mechanism. The results showed that the ductile behaviour of erosion mechanism is dominated at both room temperature and 400 °C temperature. Mechanism involved at 90° impact angle is plastic deformation with formation of craters and at 30° impact angle is cutting and ploughing.

Geology of the northeastern flank of Apollinaris Mons, Mars: Constraints on the erosional history from morphology, topography, and crater populations

We have utilized THEMIS, MOLA, CTX and HiRISE data sets to investigate the morphologic and topographic characteristics of the northeast flank of Apollinaris Mons, a region with evidence for significant erosion of volcanic deposits. Using ArcGIS software, we mapped the geology of the northeast flank and obtained age estimates using crater size-frequency distributions from crater counts. Of the eight mapped units, three (Apollinaris Mons upper, mid-, and lower flank units) represent volcanic flank materials in various states of preservation. The Late Noachian-Early Hesperian upper flank unit is massive and contains joint-like vertical structures along the scarp faces of two large plateaus whose upper surfaces likely represent the original surface or near-surface deposits of Apollinaris Mons. Downslope-facing plateau scarps have up to 500 m of relief. Positioned below this unit are the mid-flank and lower flank units, each representing eroded surfaces within Apollinaris Mons flank materials that have stabilization ages between the Late Hesperian to Early Amazonian. Mantling material in the region contains cavities and boxwork-like textures that resemble patterns in terrestrial eroded pyroclastic flow deposits. Dome-shaped mounds west of the mapping region have morphologic similarities to terrestrial fumarolic mounds or possibly inverted impact craters. Both the texture and features suggest widespread pyroclastic deposits adjacent to Apollinaris Mons. Using MOLA gridded topography, we estimate that ~308 km3 of materials have been eroded along the flanks of the volcano. Statistical and histogram data from the thickness values of eroded materials shows that up to ~300 m of material has been removed from the majority of flank surfaces. Assuming steady state erosion of flank surfaces, we estimate an area-normalized loss rate of ~0.859 nm/yr for northeast Apollinaris Mons. This erosion rate is within the long-term range for Mars (~0.01–10 nm/yr) as estimated from MER landing site geology by Golombek et al. [2006].

Comparison and Contrast in Soil Depth Evolution for Steady State and Stochastic Erosion Processes: Possible Implications for Landslide Prediction

AbstractThe importance of gradual erosion relative to landsliding depends predominantly on the slope angle. One factor of critical influence in landsliding along with slope angle and slope shape is the soil depth. Understanding soil depth development on steep topography is fundamental for understanding and predicting the occurrence of landsliding at threshold landscapes. We develop a model to predict soil depth that addresses both threshold and gradual processes. If erosion is a gradual process, soil depth increases until the soil production rate no longer exceeds the erosion rate, and steady state is reached. The predicted soil depth (x) is proportional to the ratio of the infiltration to the erosion rate. Identifying a predictive result for erosion as a function of slope angle (S) allows a test of both the erosion and soil production models with field observations. The same theoretical approach to soil production should be applicable when the principal erosion process is shallow landsliding. After landslides, soil recovery initially follows our predicted power law increase in time, though with increasing time background erosion processes become important. At a time equal to a landslide recurrence interval, the soil depth can exceed the steady state depth by as much as a factor 2. By comparing predicted and observed x(S) results, we show that the accessed result for erosion as a function of slope angle is accurate. Soils deeper than the depth predicted at the landslide recurrence interval are beyond the stability limit. This result suggests an important practical relevance of the new soil production function.

Paired-cosmogenic nuclide paleoaltimetry

Goal – The reconstruction of past topographies remains challenging and only a few methods allow accurate determination of past surface elevations. We propose here a new technique for deriving paleo-elevations, in which multiple cosmogenic nuclides are measured in the same geological sample exposed at the Earth's surface. This method relies on the altitude dependence of the cosmogenic nuclides' production rates combined with the radioactive decays of nuclides with different half-lives.Theory – The position of the two cosmogenic nuclide exposure curves (26Al/10Be vs10Be or 10Be/21Ne vs10Be) depends on the altitude of exposure. If the studied surfaces have been exposed for sufficiently long durations (>500 ka), or have been affected by low erosion rates (<1 mMa−1), measurement of two cosmogenic nuclides with different half-lives thus allow accurate elevations to be determined with a reasonable uncertainty (<1000 m at 1σ). For shorter exposure durations, the method is able to constrain minimum elevations. The main advantage of the method is that it is only slightly sensitive to erosion: even if the preservation state of the surface is unknown, the bias on the computed elevation remains lower than 1500 m in most cases. The approach can also be applied to previously exposed surfaces that have subsequently been buried, in order to reconstruct the paleo-elevation of a given surface over time ranges of ∼0 to 8 Ma (using the 26Al–10Be pair) and ∼0 to 12 Ma (using the 10Be–21Ne pair).Data comparison – We tested the method using the multiple cosmogenic nuclides dataset available for the western arid tropical Andes. The altitudes computed using the cosmogenic nuclide concentrations agree within uncertainties with the reported sampling altitudes over a range of 0 to more than 4000 m, illustrating the applicability of the method. Altitudes computed under the assumptions of continuous exposure or steady state erosion yields best fits that are statistically in agreement and close to the 1:1 line for both the 26Al–10Be and the 21Ne–10Be dataset. The 21Ne–10Be inventories in samples that have been exposed for more than 5 Ma yield elevations that are several hundreds of meters below their present-day elevations (∼1000 m). This may result from a post 10 Ma uplift of the West Andes, or from an unrecognized exposure underwater, or below a soil cover.Implications – This study may also have implications in other fields that rely on multiple cosmogenic nuclide measurements. The same approach might notably be used to compute the depth of exposure of samples located below the rock surface or underwater. This study may also help to improve the accuracy of the common burial dating method that uses multiple radioactive cosmogenic nuclides. For long pre-burial exposures (>500 ka), or low erosion rates (<1 mMa−1), the values of the pre-burial nuclides ratios indeed depend strongly on the altitude of exposure. It may be important to consider the pre-burial altitude of exposure in order to calculate accurate burial ages.

Parametric Optimization of Erosion Behavior of Marble Dust Filled Aramid/Epoxy Hybrid Composite

The aim of present research work is to study the erosive wear response of epoxy based marble dust filled aramid bidirectional fabric-reinforced polymer composite. In this respect the aramid bidirectional reinforced epoxy based composites are fabricated with varying the proportion of marble dust (0, 10 20 and 30 wt.%). Steady state erosion test is performed on different impingement angle to investigate the erosion behavior of composites. The results reveal that erosive resistance of the composites is increasing with incorporation of marble dust and exhibit semi brittle erosion behavior. To increase the performance of erosive wear resistance of fabricated composites L16 orthogonal array design of taguchi method is implemented. Marble dust content, Impingement angle, erodent size and impact velocity are considered as control factors under the set of design experiments. Impact velocity shows significantly effect on the erosion response of marble dust filled aramid fiber reinforced epoxy composite.

Tribo-performance of Granite Powder Filled Glass-epoxy Composites

This article revealed the fabrication of hybrid composites filled with glass fiber and reinforced with glass fiber in to epoxy resin. Filled composites are fabricated with incorporation of 0, 8, 16 and 24 wt.% granite powder by keeping 40wt.% glass fiber loading constant. It further investigated the physical properties and slurry erosion wear behavior using Slurry Jet Erosion Tribometer (DUCOM TR-411) of these composites and presents a comparative study. The steady state analysis according to ASTM G-73 for erosion revealed positive effect of both the reinforcement. Unfilled epoxy composites showed semi-ductile fracture against the impact of high velocity slurry jet. However, granite powder filled epoxy composites revealed shift semi-ductile to brittle failure under slurry jet impact. As erosion rate is not uniform along the eroded surface, the profile of eroded surface is observed and analyzed. All the different profiles are like round bowl with protruded island at the middle. In addition to steady state erosion wear, experiments are conducted according to Taguchi L16 orthogonal array approach for design of experiments. The results indicate that impact velocity and fiber or/and filler content influence the erosion wear rate significantly.

Cavitation Erosion Resistance Assessment and Comparison of Three Francis Turbine Runner Materials

Cavitation erosion is the most important erosion mechanism in Francis turbine runner blades. For this reason, knowledge of a material’s ability to resist cavitation is important in defining how suitable it is for use in a Francis turbine. In this study, three Francis turbine materials were subjected to cavitation erosion in a high-speed cavitation tunnel. One of the materials was a low-alloy steel, and the other two were stainless steels. The cavitation tunnel produced an annular cavitation field on one face of a cylindrical specimen. The test specimens underwent cavitation erosion until the erosion had reached a maximum penetration depth of about 0.5 mm. The material surface profiles were measured at regular intervals to calculate volume and mass loss. These losses were compared to those of several other materials that had undergone the same tests with the same setup and operational parameters. The materials were compared according to their steady-state erosion rates. The steady-state erosion rate represents a material’s ability to resist cavitation erosion once cavitation damage has already started to develop. The low-alloy steel eroded four times faster than the two stainless steels. One of the stainless steels tested here (Stainless steel 1) had the lowest erosion rate, along with another previously tested stainless steel. The other stainless steel (Stainless steel 2) had a slightly greater erosion rate than the first, falling into the same class as other lower-grade stainless steels and a nickel aluminum bronze alloy. The results show that in choosing a turbine blade material, stainless steels outperform nonstainless ones. The choice of which type of stainless steel to use is significant in turbines with cavitation problems. The eroded surfaces were analyzed with scanning electron microscopy in order to study the erosion mechanisms, and these studies showed that most of the damage is probably due to low-cycle fatigue.

Sustainable Slopes: Satisfying Rainfall-Erosion Equilibrium and Mechanical Stability

Abstract. While manmade slopes are traditionally constructed with planar cross-sections, natural stable slopes are usually curvilinear with significant concavity of the profile. This concavity occurs as a result of evolutionary processes in which rain-driven erosion and sediment transport are balanced through slope shape adjustments. At the point of equilibrium, a relatively steady concavity with a uniform erosion rate is observed over time. Nevertheless, a true equilibrium state is possible only if mechanical stability is satisfied. In this study, concave profiles in rainfall erosion equilibrium were found based on the principles of the well-known RUSLE2 model. Results showed the existence of a family of steady shapes satisfying the condition of uniform normalized erosion rate. Those steady concave shapes that also satisfied long-term mechanical stability were then investigated. The overall results suggest that concave slopes can be constructed to achieve both minimal steady-state erosion equilibrium and mechanical stability, leading to more natural and sustainable landforms with minimal sediment delivery during initial slope adjustments. Keywords: Concave slopes, Erosion, Sustainable design, Slope stability.

A multiscale model for sediment impact erosion simulation using the finite volume particle method

The erosion of a surface by a sediment-laden flow is an inherently multiscale phenomenon which includes physical interactions covering many orders of magnitude in both length and time scales. Conforming to the nature of the problem, we propose a novel multiscale model for simulating this complex process. On the one hand, a macroscale model encompassing the whole domain of interest solves the turbulent sediment transport problem. On the other hand, a microscale model simulates the sediment impacts against the surface. A sequential multiscale strategy is used to link the submodels, such that the microscale model provides closure to the macroscale model in terms of the calculated steady state erosion rate and restitution coefficients, therefore reproducing the original coupled problem. The proposed methodology is validated against experimental data for the slurry jet erosion of a copper plate at three impingement angles. Both the global erosion rate and the erosion depth profile are predicted with mean relative errors of 18% compared to the corresponding experimental values, achieving a significant improvement over correlation-based approaches.

Production of 21Ne in depth-profiled olivine from a 54 Ma basalt sequence, Eastern Highlands (37° S), Australia

In this study we investigate the cosmogenic neon component in olivine samples from a vertical profile in order to quantify muogenic 21Ne production in this mineral. Samples were collected from an 11 m thick Eocene basalt profile in the Eastern Highlands of southeastern Australia. An eruption age of 54.15±0.36 Ma (2σ) was determined from 40Ar/39Ar step-heating experiments (n=6) on three whole-rock samples. A 36Cl profile on the section indicated an apparent steady state erosion rate of 4.7±0.5 m Ma−1. The eruption age was used to calculate in situ produced radiogenic 4He and nucleogenic 3He and 21Ne concentrations in olivine. Olivine mineral separates (n=4), extracted from the upper two metres of the studied profile, reveal cosmogenic 21Ne concentrations that attenuate exponentially with depth. However, olivine (Fo68) extracted from below 2 m does not contain discernible 21Ne aside from magmatic and nucleogenic components, with the exception of one sample that apparently contained equal proportions of nucleogenic and muogenic neon. Modelling results suggest a muogenic neon sea-level high-latitude production rate of 0.02±0.04 to 0.9±1.3 atoms g−1 a−1 (1σ), or <2.5% of spallogenic cosmogenic 21Ne production at Earth’s surface. These data support a key implicit assumption in the literature that accumulation of muogenic 21Ne in olivine in surface samples is likely to be negligible/minimal compared to spallogenic 21Ne.

Using 10Be cosmogenic isotopes to estimate erosion rates and landscape changes during the Plio-Pleistocene in the Cradle of Humankind, South Africa

Concentrations of cosmogenic 10Be, measured in quartz from chert and river sediment around the Cradle of Humankind (CoH), are used to determine basin-averaged erosion rates and estimate incision rates for local river valleys. This study focusses on the catchment area that hosts Malapa cave with Australopithecus sediba, in order to compare regional versus localized erosion rates, and better constrain the timing of cave formation and fossil entrapment. Basin-averaged erosion rates for six sub-catchments draining the CoH show a narrow range (3.00 ± 0.28 to 4.15 ± 0.37 m/Mega-annum [Ma]; ±1σ) regardless of catchment size or underlying geology; e.g. the sub-catchment with Malapa Cave (3 km2) underlain by dolomite erodes at the same rate (3.30 ± 0.30 m/Ma) as the upper Skeerpoort River catchment (87 km2) underlain by shale, chert and conglomerate (3.23 ± 0.30 m/Ma). Likewise, the Skeerpoort River catchment (147 km2) draining the northern CoH erodes at a rate (3.00 ± 0.28 m/Ma) similar to the Bloubank-Crocodile River catchment (627 km2) that drains the southern CoH (at 3.62 ± 0.33 to 4.15 ± 0.37 m/Ma). Dolomite- and siliciclastic-dominated catchments erode at similar rates, consistent with physical weathering as the rate controlling process, and a relatively dry climate in more recent times. Erosion resistant chert dykes along the Grootvleispruit River below Malapa yield an incision rate of ∼8 m/Ma at steady-state erosion rates for chert of 0.86 ± 0.54 m/Ma. Results provide better palaeo-depth estimates for Malapa Cave of 7–16 m at the time of deposition of A. sediba. Low basin-averaged erosion rates and concave river profiles indicate that the landscape across the CoH is old, and eroding slowly; i.e. the physical character of the landscape changed little in the last 3–4 Ma, and dolomite was exposed on surface probably well into the Miocene. The apparent absence of early Pliocene- or Miocene-aged cave deposits and fossils in the CoH suggests that caves only started forming from 4 Ma onwards. Therefore, whilst the landscape in the CoH is old, cavities are a relatively young phenomenon, thus controlling the maximum age of fossils that can potentially be preserved in caves in the CoH.

Numerical Simulation and Experimental Validation of Granite Powder Filled Jute Epoxy Composite for Slurry Jet Erosive Wear

Abstract In the polymer composite the benefits of utilizing the excellent wear resisting properties in terms of light weight structural design are immediately apparent. Hence, the focus of this study is to propose new sets of unfilled and particulate filled treated jute epoxy composites. Therefore, initially five different weight percentages of alkali treated jute epoxy composites are fabricated (10, 20, 30 40 and 50 wt.%) and studied their slurry erosive wear in experimentally at different operating conditions such as by varying impact velocity and impingement angle by keeping all other factors constant. The steady state erosion results for jute epoxy composites shows better wear resistant behavior for 40 wt.% jute fiber loading. Hence, for further fabrication of series of hybrid composite 40 wt.% jute fiber is kept constant and granite powder is varied in three different (8, 16 and 24 wt.%) weight percentages. The granite filler content in the jute epoxy composite played a major contribution for slurry erosion resistance. Finally, the obtained experimental results are compared with simulated model results by using a computational fluid dynamics tool. The eroded samples are observed through scanning electron microscope to study the wear mechanism.

The evolution of eastern Sichuan basin, Yangtze block since Cretaceous: Constraints from low temperature thermochronology

In Yangtze block (South China), there is a well-developed Mesozoic thrust system extended through the Xuefeng and Wuling mountains in the southeast to the Sichuan basin in the northwest. We present 11 apatite fission-track (AFT) data and 11 (U–Th–Sm)/He ages to unravel the low temperature thermal history of a part of the system located in the eastern Sichuan basin. The fission-track data are interpreted using a grain-age deconvolution algorithm with inverse thermal modeling of track length, grain ages and mineral composition proxy data. Results suggest that apatite fission-track ages range between 99.3±8.1 and 51.0±4.0Ma, and the apatite (U–Th–Sm)/He ages between 58.3±3.5Ma and 14.2±0.9. The spatial distribution of these ages shows a trend decreased from SE to NW gradually, which supports the idea of a prolonged, steady-state rock uplift and erosion process across the eastern Sichuan basin. Thermal history modeling of the combined FT and (U–Th–Sm)/He datasets reveal a common three stage cooling history: (1) initial stage of rapid cooling that younger to the east during pre-Cretaceous, (2) following by a period of relative (but not perfect) thermal stability at ∼65–50°C, (3) and then a new rapid cooling stage that initiated in all samples between ∼15 and 20Ma. The first rapid cooling at a rate of ⩾1.5°C/Ma is associated with coeval tectonism in nearby regions, which result in folds and faults of the eastern Sichuan basin. Early-mid Cenozoic thermal stability is contributed to the extension widely occurring in the eastern China continent at which the average cooling rate decreased to ∼0.16°C/Ma. Causes for speculative accelerated cooling after ca. 20–15Ma with a rate of ⩾1.2°C/Ma may be a far-field effect of upward and eastward growth of the Tibetan Plateau but could also be related to climate effects. In a whole, this paper analyzes the several Mesozoic and Cenozoic tectonic events influence to the patters of regional denudation.

Erosion rate in the Shapotou area, northwestern China, constrained by in situ-produced cosmogenic 21Ne in long-exposed erosional surfaces

Erosion at the Earth's surface is a major factor controlling the landscape evolution. Cosmogenic nuclides provide a valuable tool for the quantitative study of surface erosion. We employ cosmogenic nuclide 21Ne analysis to quantify the average erosion rate in the Shapotou area, at the northeastern margin of the Tibetan Plateau, based on the steady-state erosion model. A series of erosional surfaces on the river terraces generated by the Yellow River incision offer us a new approach to determine whether the cosmogenic 21Ne nuclide inventory has reached equilibrium between nuclide production and loss by surface erosion. Using the steady-state 21Ne concentration, the average erosion rate in this area is determined to lie between 0.54 ± 0.11 cm ka−1 and 0.72 ± 0.21 cm ka−1. A depth profile of the subsurface cosmogenic 21Ne concentrations provides additional evidence for the validity of our steady-state erosion model. Our results reveal that the erosion rate in this area lags significantly behind the incision rate of the Yellow River, which increased the local relief in the Shapotou area.