chemical and isotopic characteristics of the didwana rajod h5 chondrite the mineralogical and chemical characteristics of the didwana rajod meteorite are described the mean mineral composition is found to be olivines fo83 2 pyroxenes en83 5wo0 7fs15 8 and feldspar is mainly oligoclase oxygen isotopic analysis shows 18o 3 8 deg and 17o 2 59 deg the nitrogen content of didwana rajod is about 2 ppm with 15n 3 4deg based on microscopic chemical isotopic and electron probe microanalysis the meteorite is classified as h5 chondrite cosmogenic tracks radionuclides and the isotopic composition of rare gases were also measured in this meteorite the track density in olivines varies in a narrow range with an average value of 6 5 0 5 x 105 cm2 for four spot samples taken at the four corners of the stone the cosmic ray exposure age based on neon and argon is 9 8 ma 22na 26al 0 94 is lower than the solar cycle average value of about 1 5 and is consistent with irradiation of the meteoroid to lower gcr fluxes as expected at the solar maximum the track density rare gas isotopic ratios 60co activity and other radionuclide data are consistent with a preatmospheric radius of about 15 cm corresponding to a mass of about 50 kg the cosmogenic properties are consistent with a simple exposure history in the interplanetary space

cosmogenic nuclides in the kirin chondrite abstract radioactive and stable cosmogenic nuclides have been determined in the various fragments of the kirin chondrite h5 experimental results obtained from our samples are described and compared with similar data obtained in other laboratories cosmogenic 54 mn 22 na 60 co 26 al 53 mn 40 k in the metal phase and light noble gases were measured based on these data the irradiation history of this meteorite can be explained in terms of 1 a multi stage exposure which involves a first stage irradiation for 10 7 years and a second stage for about 4 10 5 years and 2 depth effects in the productions of the nuclides in 4 second stage and 2 first stage geometries these conclusions are consistent with those of our previous work which was based on a limited number of samples

simulated headward erosion of bank gullies in the dry hot valley region of southwest china although the development and migration of gully headcuts can increase soil loss and accelerate landscape degradation considerably little attention has been paid to the spatiotemporal variations of the morphological characteristics of bank gully heads in the dry hot valley region of southwest china this study explored the in situ variations in soil loss rates and morphological characteristics in active bank gully heads testing the overland flow discharge with a range of 30 to 120 l min 1 in response to this flow actively migrating headcuts developed with retreat rates ranging from 2 6 to 7 9 mm h 1 all experimental runs resulted in a gradual increase in soil loss volume incision depth and retreat distance over time due to set flow rates for the gully beds and upstream areas of gully heads the soil erosion rates were greatest at the beginning of each run and progressively decreased during the scouring test non steady state soil erosion rates were observed in the headwall for the flow discharge levels examined for this study this was due to an abrupt slope collapse after long term scouring effects as degradation progressed similar trends emerged for temporal variations within the fractal dimensions of topographic surfaces in both the gully heads and upstream areas after the scouring was run for a period of 90 min asymptotic fractal dimensions of topographic surfaces were attained in the upstream areas and gully heads suggesting that steady state morphological characteristics had been realised it should be noted that headwall collapses are typically associated with a substantial increase in sediment yield where no other obvious change in morphological characteristics occurs in the headwall therefore even though a significant difference in the soil erosion rates and fractal dimensions of topographic surface values could be found between the bank gully heads and upstream areas the temporal variation in the morphological characteristics of bank gully heads was similar to those observed in upstream areas where ephemeral gullies developed c 2013 elsevier b v all rights reserved

nitrogen components in primitive ordinary chondrites abstract nitrogen and ar in more than 20 primitive ordinary chondrites were studied by a stepped com bustion method several n carriers that are characterized by n isotopic composition n release pattern and trapped ar release pattern are recognized in the primitive ordinary chondrites large fractions of anomalous n and associated ar are removed by acid treatment in most cases the n isotopic anomalies cannot be explained by known presolar grains with a possible exception of graphite and some of the n isotopic anomalies may be due to unknown presolar grains there is no specific relationship between the type of n carriers contained in an ordinary chondrite and the chemical type h l or ll of the chondrite it is likely that as a result of impacts the carriers of isotopically anomalous n were mixed in various parent bodies as rock fragments rather than as individual fine particles the presence of distinctive n isotopic anomalies in primitive meteorites indicates that the primitive solar nebula may have been heterogeneous either spatially or temporally

capturing gypsum rillenkarren morphometry by a 3d photo reconstruction 3d pr technique abstract rillenkarren are small scale straight narrow solution channels that head at the crest of a bare rock slope and are extinguished downslope in this paper the applicability of 3d photo reconstruction technique of the rock surface is proposed for capturing the rillenkarren morphometry on gypsum at first the measurements are used to assess a relationship between the width depth ratio and the depth of the rillenkarren the exponent of this power relationship resulted different from the theoretical value 0 5 confirming that the cross section profiles of a rillenkarren can have a shape different from parabolic the analysis developed for the cross section area the perimeter and the hydraulic radius established that the formation process is able to deep and enlarge the channel the proposed model of the measured longitudinal profiles confirmed that the profile shape can be characterized by a flex point which divide the upstream concave part from the downstream convex one according to previous studies on soil erosion features rills ephemeral gullies and gullies the relationship between the rillenkarren length and its volume was expressed by a power equation the comparison between rillenkarren and soil erosion features allowed to conclude that a single exponent equal to 1 1 can be applied while the coefficient is characteristic of the feature and represents the influence of channel depth and width finally a model of rillenkarren morphometry deduced applying the dimensional analysis and self similarity was applied to the measurements this analysis demonstrated that a single dimensionless relationship is applicable to rillenkarren and rills ephemeral gullies and gullies assessing that a morphometric similarity exists between these different erosion features

light element geochemistry and spallogenesis in lunar rocks abstract the abundances and isotopic compositions of carbon nitrogen and sulfur were measured in eleven lunar rocks samples were combusted sequentially at three temperatures to resolve terrestrial contamination from indigenous volatiles sulfur abundances in apollo 16 highland rocks range from 73 to 1165 g g whereas sulfur contents in apollo 15 and 17 basalts range from 719 to 1455 g g and correlate with tio 2 content lunar rocks as a group have a remarkably uniform sulfur isotopic composition which may reflect the low oxygen fugacity of the basaltic magmas much of the range of reported 34 s cd values 2 to 2 5 permil is caused by systematic analytical discrepancies between laboratories lunar rocks very likely contain less than 0 1 g g of nitrogen the measured spallogenic production rate 4 1 10 6 g 15 n g sample m y agrees remarkably closely with previous estimates an estimate which includes all available data is 3 7 10 6 g 15 n g sample m y lunar basalts may contain no indigenous lunar carbon in excess of procedural blank levels 0 7 g g highlands rocks consistently release about 1 to 5 g g of carbon in excess of blank levels but this carbon might either derive from ancient meteoritic debris or be a mineralogie product of terrestrial weathering the average measured spallogenic 13 c production rate is 4 1 10 6 g 13 c g sample m y the 13 c spallation exposure ages of rocks 15058 and 15499 are 184 and 135 m y respectively

geomorphic threshold conditions for ephemeral gully incision abstract ephemeral gully erosion in cultivated land is an important source of sediment that is frequently being overlooked and not accounted for in soil erosion studies furthermore little is known about the factors controlling ephemeral gully erosion in this paper the available information on the initiation and location of ephemeral gullies is summarised focusing on the relationship between the upslope drainage area a and the critical slope gradient s cr for ephemeral gully initiation by plotting the non linear relationship between critical slope gradient measured immediately upstream of the incision head and drainage area at the incision head for gullied sites it was possible to draw a straight line on log log paper through the lower most points for each of the available datasets representing a critical slope area relationship for incision consequently below this line no incision occurs this line or critical relation can also be written as a power function between critical slope and area although many factors vary between the different datasets the exponent of the drainage area relationship 0 4 showed very little variation the observed critical slope area relationship can be related to a simple model of channel initiation by overland flow furthermore this relationship can be used to identify potentially unstable sites where control measures should be undertaken

ephemeral gully erosion in southern navarra spain abstract ephemeral gully erosion is a common type of water erosion in the loamy soils formed on the miocene marls of southern navarra a study has been conducted to describe the different types of ephemeral gullies and to determine their origin evolution and importance as sediment sources three main types were identified according to their origin classic ephemeral gullies formed within the same field where runoff starts drainage ephemeral gullies collecting the runoff from another upstream area and discontinuity ephemeral gullies due to some abrupt slope change in the landscape during 2 consecutive years of normal precipitation ephemeral gully erosion has caused significant soil losses locally over 2 66 kg m 2 yr 1 which is above tolerable levels in each year one short and intense rainfall event has been responsible for almost all soil losses from ephemeral gullies the main cause of gully formation is the lack of any proper waterway for conveying water excess conventional tillage practices provoked gully occurrence while the maintenance of stubble or vegetation cover completely prevented their formation although farmers refill gullies every year they reappear at the same position if no preventive measures are taken early winter has been the most critical period for gully formation when the soil is wetter and the surface cover is scarce but a strong summer thunderstorm also caused severe gully erosion in unprotected soils two simple topographic indices based on the area and the slope of the watersheds are useful to describe total soil losses

experimental investigation of morphological characteristics of rill evolution on loess slope abstract the development of rill is the result of a complex interaction of soil properties with high spatial and temporal variability the rill morphology may act as a determinant as well as a stochastically driven process the description of their complex morphology requires geostatistics and nonlinear theories a study of the morphological characteristics of rill evolution was performed via indoor soil pan rainfall simulations experiments were run with loessial soil bulk density of 1 25 g cm 3 under a rainfall intensity of 90 mm h with a 20 slope gradient a detailed scan of the slope topographic analysis and statistical analyses were the main methods utilized in the study statistical analyses showed that characteristic parameters exhibited differences in the expression of the dynamic change of soil loss according to the comparison of quantitative methods we found that the fractal dimension can reflect the complexity of rill network but it is not able to reflect the dynamic changes of the erosion process perfectly in contrast geomorphologic comentropy is sensitive to the dynamic changes of soil erosion intensity and its variation can reflect the dynamic changes of erosion perfectly the topological parameters can reflect the degree of stability in the rill network structure but it is not suitable for reflecting the dynamic changes of erosion intensity the geomorphologic comentropy was evaluated as the most appropriate characterization parameter for the rill morphology description

assessment of gully erosion in eastern ethiopia using photogrammetric techniques abstract eastern ethiopia is severely affected by soil erosion as it is revealed by the commonly occurring deep and wide gullies these gullies are dynamically expanding into agricultural lands at an alarming rate they are also the chief sources of sediment causing siltation of lakes that are valuable sources of both drinking and irrigation water in the alemaya and harar areas a quantitative assessment of gully dynamics and the associated soil loss and a prognosis of areas susceptible to further gullying were deemed crucial aerial photographs from two different dates 1966 and 1996 with approximate scales of 1 45 000 were used to study the development and dynamics of gullies as indicated by volume changes between the two dates they were digitized at a pixel size of 20 m digital elevation models dem with grid widths of 20 and 2 m were derived from stereo image pairs separately gully breaklines and borderlines were measured for the identified gully systems gully profiles were positioned at regular intervals of 20 m along the gully length giving rise to gully sections that are portions of a gully between neighbouring profiles gully volume was computed for every gully section soil loss was estimated from the computed gully volumes using soil bulk density it showed that soil loss per unit of gully surface is very high 1 7 tons m 2 of gully surface over the 30 years time period indicating the severity of gully erosion in the subcatchment there was significant agreement between breakline measured and field measured gully depth and width for selected points this is an indication of the potential of the method for reliable gully volume estimation and hence quantification of soil loss due to gully erosion the possibility of predicting hill slope areas susceptible to further gullying based on the topographic attributes such as specific contributing area and local slope from an interpolated detailed dem with 2 m resolution was tested it was found that wetness index alone or a combination of the wetness index and the compound topographic index at the threshold values established in literature would give better results as viewed from better connectivity of flow lines and higher conformity of the predicted susceptible areas to natural gully headcut and expansion in a landscape reality

compositional differences in enstatite chondrites based on carbon and nitrogen stable isotope measurements carbon and nitrogen abundance and isotopic compositions from four eh4 one eh5 five el6 chondrites and one aubrite were determined by using stepped pyrolysis n only and combustion n and c extractions in attempts to distinguish the components present carbon contents range from 0 15 to 0 70 wt with no systematic relationship between carbon content and meteorite group or petrologic type whole rock 13c values range from 28 5 to 4 1 most c occurs as graphite and when temperature steps above 700 c are considered there is a difference between eh4 5 13c 9 1 to 5 8 and el6 chondrites 13c 6 7 to 4 2 carbon in bustee aubrite is isotopically lighter 13c 24 than in any enstatite chondrite nitrogen occurs as osbornite sinoite and in isostructural substitution for oxygen in silicate lattice sites nitrogen abundances and isotopic compositions are more variable than c due to the heterogenous distribution of n bearing minerals three el6 s containing osbornite have higher n concentrations than other type 6 enstatite chondrites sinoite where present is depleted in 15n relative to osbornite nitrogen in the bustee aubrite has a similar abundance and 15n value to those of el6 s again dominated by the presence of osbornite in addition to the refractory c and n bearing minerals there is also organic material largely terrestrial contamination and evidence for at least two exotic components the first is a host for xe hl and is characterized by 13c 47 and 15n 73 whereas the second is less well defined but is marked by 15n 269

iridium emissions from kilauea volcano during may 1983 gas and particulate samples were collected at the cooling vents of kilauea volcano in hawaii three vents on the southeast rift zone were sampled using base treated filter packs to absorb acidic gases and teflon filters for particles the samples were analyzed for 40 elements by nondestructive neutron activation analysis as with other volcanoes the chalcophilic and volatile elements were enriched by up to seven orders of magnitude relative to the erupted basalt unlike the case of other volcanoes iridium was observed to be highly enriched 105 fold at the two higher temperature vents and the degree of enrichment appears to be related to both high temperatures and high fluorine content of the gases estimates of the emission rates of ir during eruptions of kilauea based on the measurements reported here and those of the hawaiian volcano observatory yield an emission rate of about 3 g ir per 106 m3 of magma this rate amounts to only about 0 3 of the ir present in the magma that is being released by the volcano this previously unidentified ir source to the atmosphere and ocean may have a significant influence on the geochemical cycle of ir on the earth the uniqueness of kilauea in its emissions of ir is probably related to the deep source of magma which contains significant levels of ir 0 32 ppb and high levels of the halogens f and cl

microanalysis of nitrogen isotope abundances association of nitrogen with noble gas carriers in allende current research efforts to explore and account for the distribution of nitrogen isotope abundances in the ancient and present day solar wind and in meteorites often require measurement of nitrogen abundances and isotopic compositions in very small samples of rare extraterrestrial materials isotopic analysis of 1 g of n2 is possible with modern techniques of dynamic mass spectrometry but even this high sensitivity is a limiting factor for certain critical samples we have utilized a statistically operated mass spectrometer coupled to an ultrahigh vacuum gas extraction and processing system to lower this limit by approximately four orders of magnitude quantities of n2 ranging from 100 ng to 100 pg are measurable with permil to percent precision in isotope ratios nitrogen and all noble gases evolved during stepwise combustion of fine grained matrix material separated from the allende meteorite have been meausred simultaneously in a pilot experiment using this technique isotopically heavy h xe ccf xe and isotopically light n are co sited in a carbonaceous carrier phase supporting a nucleosynthetic origin for15n depleted nitrogen in allende the great isotopic uniformity of trapped ar in all carrier phases indicates that simple physical mass fractionation in gravitational escape of volatiles from the primitive nebula cannot have played a significant role in generating the nitrogen compositions observed in solar system matter

field investigation of rill and ephemeral gully erosion in the sparacia experimental area south italy abstract this paper reports the results of a field investigation aiming at characterizing the morphology and hydraulics of both rills and ephemeral gullies egs monitored at sparacia experimental area sicily italy the comparison between rill and interrill erosion measurements showed that sediment delivery processes occurred in some erosive events and that the rill erosion rate was dominant in many cases the measurements were used for testing both the empirical relationships between the channel rill egs and gully length and its eroded volume and among the morphological variables length width depth and volume describing the channelized process finally the rill and egs hydraulic geometry was modelled by three well known power equations relating the discharge with the mean flow velocity with the flow depth and with the width of each channel segment respectively the rill measurements also showed that the flow velocity was affected by the rill segment slope while the flow depth and width were controlled by the plot slope therefore three equations taking into account these slope effects were proposed to estimate the hydraulic characteristics of the rills monitored at the sparacia area

morphology and influencing factors of rills in the steep slope in yuanmou dry hot valley sw china abstract it is very important to understand rill morphology in order to understand its dynamics to reveal the morphology and influencing factors of rills in the steep slope rss in the yuanmou dry hot valley the total station photogrammetric technique and microtopographic profiler were used to obtain the parameters of the cross sections and longitudinal profiles of the rss and 12 parameters were used to characterize the rill morphology the results show that the morphology of rills clearly varied between each layer the topography soil properties and ferruginous cemented layer all exerted important influences on the rill morphology the average depth decreased with increasing slope length and the depths dominated by silt and sand were larger than that dominated by clay the average width and average width depth ratio increased with increasing slope length and the width and the width depth ratio that was dominated by clay was larger than that dominated by silt and sand the shape ratio of the rill cross section ranged from 0 50 to 0 58 and the shape of the cross section gradually changed from narrow and deep to wide and shallow with increasing slope length concave convex degree tended to be larger in the segment with ferruginous cement in the longitudinal profile the gradient gradually decreased with decreasing slope gradient and increasing slope length the presence of the ferruginous cemented layer and topsoil crust resulted in abnormal changes in the shape of the rill it is helpful to further understand the mechanisms of rill erosion under different conditions

trapped nitrogen in individual chondrules nature of chondrule precursors and clues to formation mechanisms 1 nitrogen amount and isotopic composition have been measured in individual chondrules of six ordinary chondrites oc and two each of carbonaceous cc and enstatite chondrites ec the n ppm 15nt corrected for cosmogenic contribution for the chondrules have ranges of 0 8 to 61 97 to 164 19 to 140 21 to 31 and 2 to 77 27 to 116 among oc ec and cc respectively for oc while n contents of chondrules fall in the range of bulk oc 15n spans a wide range in contrast to the narrow range 25 to 14 for bulk for cc chondrules n contents are lower while 15n is different and heavier than bulk in contrast ec chondrules and bulk have comparable n and 15n values neither n nor 15nt of oc and cc chondrules show any size expected for nebular exchange or chemical mineralogical dependence ruling out the dominance of secondary effects of nebular or parent body origin the range of 15nt among oc and cc chondrules represents 15nt heterogeneity of chondrule precursors and their survival after a high temperature chondrule forming event on the basis of 15n of the chondrules we propose the presence of at least three n components carried by phase q presolar diamonds hl and insoluble organic matter iom the precursors of chondrules from oc and cc are different than the bulk oc and cc which represents the different environment for their formation compared to the bulk oc and cc however for ec chondrules precursors as well as the formation environment are the same as those of enstatite chondrites

testing the ephemeral gully erosion model egem for two mediterranean environments few models can predict ephemeral gully erosion rates e g creams egem the ephemeral gully erosion model egem was specifically developed to predict soil loss by ephemeral gully erosion although egem claims to have a great potential in predicting soil losses by ephemeral gully erosion it has never been thoroughly tested the objective of this study was to evaluate the suitability of egem for predicting ephemeral gully erosion rates in mediterranean environments an egem input data set for 86 ephemeral gullies was collected detailed measurements of 46 ephemeral gullies were made in intensively cultivated land in southeast spain guadalentin study area and another 40 ephemeral gullies were measured in both intensively cultivated land and abandoned land in southeast portugal alentejo study area together with the assessment of all egem input parameters the actual eroded volume for each ephemeral gully was also determined in the field a very good relationship between predicted and measured ephemeral gully volumes was found r2 0 88 but as ephemeral gully length is an egem input parameter both predicted and measured ephemeral gully volumes have to be divided by this ephemeral gully length in order to test the predictive capability of egem the resulting relationship between predicted and measured ephemeral gully cross sections is rather weak r2 0 27 therefore it can be concluded that egem is not capable of predicting ephemeral gully erosion for the given mediterranean areas a second conclusion is that ephemeral gully length is a key parameter in determining the ephemeral gully volume regression analysis shows that a very significant relation between ephemeral gully length and ephemeral gully volume exists r2 0 91 accurate prediction of ephemeral gully length is therefore crucial for assessing ephemeral gully erosion rates copyright 2001 john wiley sons ltd

predicting head cut erosion and migration in concentrated flows typical of upland areas 1 soil erosion due to head cut development and migration can devastate agricultural lands yet current prediction technology does not address this important erosion process here an analytical model of this erosional phenomenon is presented realistic physically based approximations to the laws governing mass momentum and energy transfer in the neighborhood of the scour hole result in closed form predictive algorithms for the magnitude of the plunge pool erosion and the rate of head cut migration the model introduces a special treatment of nonventilated overfall conditions is limited to homogeneous unbounded soil layers and is validated by available experimental measurements

application of the egem model to predict ephemeral gully erosion in sicily italy abstract recent research has shown the importance of ephemeral gully eg erosion in the context of global erosion and at the same time the lack of adequate models to estimate it at present the ephemeral gully erosion model egem is the only conceptual model specifically developed for ephemeral gully erosion estimation the main aim of the paper is to evaluate the performance of egem model adapted to local conditions compared with that of simple empirical equations a data set of 92 ephemeral gullies formed between 1995 and 2000 in a wheat cultivated study area in sicily italy was used for the purpose in order to improve egem performance two important adaptations were made both the rain distribution type and the causative rainfall of the hydrological component of egem were modified to reproduce local conditions the egem assumption of a constant depth for the entire length of the ephemeral gully was also modified egem performance was tested with two different rain distribution types three different causative rainfalls and two different eg depths the adaptation of the egem hydrological component improves the volume prediction with respect to the standard version of egem the improvement is mainly due to the rain distribution type whereas causative rainfall seems to be less important the use of adjusted eg depths is however essential to minimise the errors between measured and predicted volumes the capability of egem to predict the ephemeral gully cross section is weak and non significant relationships were found between measured and estimated width a regression analysis between ephemeral gully eroded volume and different morphological topographical and hydrological parameters confirms the great importance of eg length to explain eroded volume r 2 0 64 for the simple correlation between volume and length considering that the adaptation of the hydrological component and the measurement of eg depths are necessary for the eg volumes estimated by egem to be reliable it seems more simple as suggested by other authors to use empirical relations between eroded volume and length performed in different environments until more precise physically based models are developed

measuring rill erosion at plot scale by a drone based technology the traditional direct method i e metric ruler and rillmeter of monitoring rill erosion at plot scale is time consuming and invasive because it modifies the surface of the rilled area measuring rill features using a drone based technology is considered a non invasive method allowing a fast field relief in the experimental sparacia area a survey by a quadricopter microdrones md4 200 was carried out and this relief allowed the generation of a digital elevation model dem with a mesh size of 1 cm and a resolution elevation equal to 2 mm for three plots l g and c affected by rill erosion at first for the experimental l plot which is 44 m long the rill features were surveyed by a manual method which was carried out by drawing on the pc screen the rill paths obtained by a visual orthophoto interpretation this manual method was not applicable for the plots in which rills of limited depth occurred and were not detectable then for both l plot and the other experimental plots having a length ranging from 22 to 44 m an automatic extraction method of rills from dem was applied using an appropriate calculation routine a vector coverage of transects orthogonal to the main flow direction i e the maximum slope steepness path was generated the intersection of each plot dem with the transect coverage allowed to obtain both the cross sections and the main rill morphological features for the l plot the comparison between the rill morphological features obtained by the two different methods manual automatic was carried out finally the length volume relationship and a dimensionless relationship proposed in literature were tested for all studied experimental plots copyright 2015 john wiley sons ltd

presolar diamond sic and graphite in primitive chondrites abundances as a function of meteorite class and petrologic type abstract acid resistant residues were prepared for eighteen meteorites from seven chondrite classes using improved procedures designed to minimize loss of presolar grains noble gases were measured by stepped pyrolysis and the abundances of five exotic noble gas components were used to determine abundances of diamond sic and graphite diamond separates were prepared to check diamond abundances determined from noble gases diamond and sic were found in unmetamorphosed members of all seven chondrite classes and evidence for graphite was found in orgued ci and ll3 0 3 1 chondrites our data and noble gas and stable isotope data in the literature show that presolar grains were incorporated into all chondrite classes the grains are sited in the fine grained matrix and their abundances within the matrix reflect mainly the degree of metamorphism suffered by the host meteorite the pattern of metamorphic destruction differs from class to class in unequilibrated ordinary chondrites uocs graphite is most easily destroyed followed by sic and then diamond no presolar grains remain in uocs of petrologic type 3 8 whose matrices have been completely recrystallized in eh chondrites diamond and sic survive much more severe metamorphism than in uocs with sic apparently more stable than diamond presolar graphite was not detected in cv3 and c03 chondrites diamond appears to be more stable than sic and graphite again is missing inferred premetamorphic diamond abundances matrix normalized vary by a factor of 2 2 between classes with eh cv and co chondrites having higher initial abundances than orgueil similar diamond sic ratios are observed in most classes and differences in the ratio can be tied to secondary processing suggesting that all chondrite classes sampled the same solar system wide reservoir of presolar grains differences in initial abundances between classes appear to correlate with chemical and physical properties of the host meteorites these bulk properties and variations in presolar grain abundances both may be the result of thermal processing of presolar dust in the accretion disk

annama h chondrite mineralogy physical properties cosmic ray exposure and parent body history the fall of the annama meteorite occurred early morning local time on april 19 2014 on the kola peninsula russia based on mineralogy and physical properties annama is a typical h chondrite it has a high ar ar age of 4 4 ga its cosmic ray exposure history is atypical as it is not part of the large group of h chondrites with a prominent 7 8 ma peak in the exposure age histograms instead its exposure age is within uncertainty of a smaller peak at 30 4 ma the results from short lived radionuclides are compatible with an atmospheric pre entry radius of 30 40 cm however based on noble gas and cosmogenic radionuclide data annama must have been part of a larger body radius 65 cm for a large part of its cosmic ray exposure history the 10be concentration indicates a recent 3 5 ma breakup which may be responsible for the annama parent body size reduction to 30 35 cm pre entry radius

cosmogenic effects in mbale l5 6 chondrite measurements of particle tracks cosmogenic radionuclides and rare gas isotopes in mbale indicate that the meteoroid had a simple one stage exposure for 30 2 ma in interplanetary space on the basis of the measured track production rates and 60co and 26al activities the meteoroid is estimated to be a sphere with a radius of 36 cm the activities of several cosmogenic radionuclides i e 57co 54mn 22na 44ti and 26al in two fragments having different shielding as estimated by their track density and 60co activity provide the depth variation in their production rates cobalt 57 54mn and 22na activities agree with the production that is expected around the maximum of the solar cycle 22 as calculated from the sunspot numbers the u th 4he and k 40ar ages are measured to be 0 54 ga indicating a late thermal event which is in agreement with the thermal history of some other l group chondrites the trapped n has 15n of 57 4 o which is much lighter than the average l group chondrite value this indicates the presence of an isotopically anomalous light n component

measuring rill erosion using structure from motion a plot experiment abstract in this paper the results of a plot experiment on rill erosion are reported the rill network manually incised on the soil and further shaped by a clear inflow discharge was surveyed using the three dimensional photo reconstruction 3d pr technique which allows to obtain a digital terrain model dtm by a large series of oblique images of the channel from consumer un calibrated and non metric cameras the three dimensional 3d dtm and the quasi tridimensional 2 5d model were generated by agisoft photoscan software for a single rill channel the reliability of the 3d image based ground measurements of morphological and hydraulic variables was positively tested by the corresponding measurements carried out on the rill gypsum cast moreover the morphological and hydraulic variables were measured at 11 transects of the plot by a profilometer p the 2 5d and 3d models using the 3d model as reference the analysis showed that the reliability of the measurements by p and 2 5d methods was comparable and the error was generally lower than 15 the rill measurements carried out by the three methods agreed with the available literature measurements and supported the applicability of both the empirical relationship between rill length and its eroded volume and the theoretical dimensionless relationship among the morphological variables describing the channelized erosion process the analysis also showed that the effect of the distance between two consecutive cross sections on the rill volume measurement by 3d model is negligible finally the shaping effect of different flow discharges on three straight rills incised into the plot was tested in particular three increasing flow discharges 0 15 0 35 and 0 5 l s 1 were used sequentially in two rills while the maximum discharge of the sequence 0 5 l s 1 was used into the third rill both the grain size distribution of the eroded sediment and the total amount of soil loss were affected by the discharge sequence

measuring rill erosion by laser scanning abstract this paper reports the results of a field investigation on the rill morphology and the corresponding soil loss using a terrestrial laser scanner tls at the masse experimental station umbria central italy laser scanning is a survey method that allows determining the three dimensional position of a large number of points point cloud through the measurement of angles azimuth and zenith and distances for this paper five scans were made of some rills which formed during particularly erosive rain in the plots of the masse station the point cloud was first interpolated by the natural neighbor method to create a discrete 0 02 m 0 02 m square cell grid digital elevation model dem used for mapping the flow network the same cloud was also used to generate a continuous modeling of the surface by the triangulated irregular network model tin to quantify the total eroded volume and the morphological characteristics of the rill formations three methods were applied to the dem for detecting the channel network the slope method horn 1981 wood 1996 the constant drop method described by broscoe 1959 and the method of landform curvature tarolli et al 2012 the comparison has shown a good agreement between the three methods but broscoe s method seems to be more accurate for rill recognition the morphological characteristics of the rill formations derived by the tin model i e length width depth and volume were compared with the corresponding characteristics obtained manually using a profilometer the analysis showed a good agreement between the width at the top measured by the two methods a general overestimation of the maximum depth and of the cross section areas and an underestimation of the rill length when the manual method is used lastly the comparison between the volumes obtained by the tls survey and by the manual method showed that the total volume calculated by the manual measurements overestimates that evaluated by the tls with a good agreement between these variables

similarity between morphological characteristics of rills and ephemeral gullies in sicily italy this paper reports the results of a field investigation aimed to establish morphological similarity between rills and ephemeral gullies rill measurements were made on 14 plots having a surface area of 22 352 m2 located on a 14 9 slope and on a plot 6 0 m wide and 22 0 m long having a uniform 22 0 slope the plots are located on the experimental station for soil erosion measurements sparacia of the agricultural faculty of palermo university in sicily italy all plots are subjected to natural rainfall the measurements were made immediately following five events between november 2004 and december 2005 the ephemeral gully measurements were made on a cultivated area of about 120 ha located in central sicily which is representative of many soil crop conditions in the mediterranean basin the morphological similarity between rill and ephemeral gully was first tested then a power relationship between rill or gully volume and length theoretically deduced by dimensional analysis and self similarity theory was applied this power relationship needs a different scale factor for rill and gully measurements finally using two dimensionless groups representative of the channel morphology variables the analysis showed that a single relationship can be applied to rill and gully measurements copyright 2009 john wiley sons ltd

cretaceous tertiary boundary event evidence for a short time scale abstract three non meteoritic trace elements sb as and zn are strongly enriched at eleven k t boundary sites along with mainly or partly meteoritic elements ir ni cr fe and co the proportions as sb zn ir are remarkably constant over a 100 fold range in concentration this correlation persists in sub layers of boundary clay and even extends to soot from burned land biomass apparently all the components despite their diverse origins became associated in a single global component prior to deposition no wholly satisfactory source is available for as sb and zn the trace element pattern in volcanic gases does not match that in k t boundary clay with ratios to ir falling short by 1 to 2 orders of magnitude terrestrial rocks do not reach high enough concentrations and modern ocean water contains too little zn but on balance the latter source seems preferable perhaps augmented by volatiles from the impact crater apparently ir bearing ejecta and soot from forest fires coagulated in the stratosphere and then fell out together sweeping out oceanic biomass and anoxically precipiting as sb and zn significantly the amounts of marine and land biomass at the k t boundary correspond to about the steady state global inventory 1 generation and the amounts of as sb and zn are also within a factor of 5 of the global inventory this is expected in a catastrophic but not a gradualist scenario

calibration of manual measurements of rills using terrestrial laser scanning abstract this article reports the results of a field investigation aimed at comparing and verifying the agreement between two methods measuring rill morphological characteristics at the masse experimental area at first the data obtained both with a manual method profilometer and with a terrestrial laser scanner tls were compared the comparison showed that the manual measurements underestimate the width at the top of the cross sections and the length of the rill segments calibration curves were derived for these characteristics and were used to correct the manual data the comparison between the corrected total length and volume and between the morphological characteristics of the measured rills at masse showed that the power relationships available in the literature are valid also for the silty clay soil in masse

morphometric and hydraulic geometry assessment of a gully in sw spain abstract gully erosion represents one of the most significant types of land degradation in the mediterranean areas giving place to important on and off site effects in this paper a second order gully located in sw spain is analyzed along the gully 28 cross sections were established and measured with a leica tcrm1102 laser total station approximately every 6 months from 2001 to 2007 the sections were located at variable distance placing them in areas where active erosion was evident in total 13 field measurements were carried out and the geometric characteristics of 28 cross sections were obtained morphometric analyses were carried out in both the main gully and a tributary reach by applying an empirical relationship between channel length and eroded volume morphometric variables of the gully sections were combined into two dimensionless groups and a morphological similarity between different linear erosion landforms rills ephemeral and permanent gullies was obtained then the coefficient of variation of the calculated volumes was used to compare the instability between the main gully and the tributary reach finally the hydraulic geometry of the gully was assessed by calibrating three empirical power equations which relate bankfull discharge with mean flow velocity cross sectional depth and width the hydraulic characterization of the main gully and the tributary reach was investigated for each field survey and a different behavior was detected the hydraulic analysis also demonstrated that higher values of discharge provide better predictions of flow velocity the size of the main and tributary gullies affects the discharge width relationship and that gully depth is the variable which can be predicted with the highest accuracy

assessment of soil losses by ephemeral gully erosion using high altitude stereo aerial photographs the objective of this study is to explore in a critical way the potential of high altitude stereo aerial photographs for the assessment of ephemeral gully erosion rates on 28 may 1995 an intensive rainfall event 30 mm h 1 during 30 min return period 3 years occurred in central belgium ephemeral gullies formed within an area of 218 ha study area 1 were mapped and measured both in the field and by high altitude aerial photos taken at the same time comparison of these two methods shows that if only one of the two surveying techniques had been used only 75 per cent of the total ephemeral gully length would have been detected so that the combination of aerial and field data leads in fact to the best possible determination of total gully length within the selected area a correction factor c is proposed so that the results of an ephemeral gully erosion survey based on high altitude stereo aerial photos can be adjusted for the undetected gullies next a sequential series of high altitude stereo aerial photographs taken in six different years was analysed in order to determine ephemeral gully erosion rates in three selected study areas study areas 2 3 and 4 selection criteria were chosen so that these three areas were similar to study area 1 and representative for the cultivated areas in central belgium where intense soil erosion regularly occurs ephemeral gullies were mapped and their total length was measured from the aerial photos using a mean gully cross section of 0 2635 m2 determined in study area 1 the average eroded volume is 1 89 m3 ha 1 in six months for study area 1 0 86 m3 ha 1 in six months for area 2 1 44 m3 ha 1 in six months for area 3 and 2 37 m3 ha 1 in six months for area 4 according to the correction factor c these mean ephemeral gully erosion volumes have to be increased by 44 per cent the ephemeral gully erosion rates based on high altitude stereo aerial photos correspond well with the results of other surveys carried out in the belgian loess belt copyright 1999 john wiley sons ltd

precursors of mars constraints from nitrogen and oxygen isotopic compositions of martian meteorites we present an approach to assess the nature of materials involved in the accretion of mars by the planets nitrogen 15n and oxygen 17o isotopic compositions as derived from data on martian meteorites 15n for mars has been derived from nitrogen and xenon systematics while 17o has been taken from the literature data these signatures indicate that mars has most probably accreted from enstatite and ordinary chondritic materials in a ratio of 74 26 and may not have a significant contribution from the carbonaceous ci cm or cv chondrites this is consistent with the chromium isotopic e53cr signatures of martian meteorites and the bulk planet fe si ratio for mars as suggested by the moment of inertia factor i mr2 obtained from the mars pathfinder data further a simple homogeneous accretion from the above two types of materials is found to be consistent with the planets moment of inertia factor and the bulk composition of the mantle but it requires a core with 6 7 wt si which is consistent with the new results from the high pressure and temperature melting experiments and chemical data on the opaque minerals in enstatite chondrites

chemostratigraphy across the cretaceous tertiary boundary and a critical assessment of the iridium anomaly the elevated concentration of iridium one of the platinum group elements pge at the cretaceous tertiary boundary is still the most generally accepted evidence that a large bolide struck the earth at the time of the end cretaceous mass extinctions new chemostratigraphic data for cross boundary sections from both hemispheres are not easily explained in terms of such an impact event for example the observation that the pge patterns show marked differences between the hemispheres the new constraints indicate that models of mantle derived pge should be seriously considered and that pge anomalies might not be as useful as previously thought as unambiguous identifiers of large impact events in the earth s history

the value of a physically based model versus an empirical approach in the prediction of ephemeral gully erosion for loess derived soils abstract a data set on soil losses and controlling factors for 58 ephemeral gullies has been collected in the belgian loess belt from march 1997 to march 1999 of the observed ephemeral gullies 32 developed at the end of winter or in early spring winter gullies and 26 ephemeral gullies developed during summer summer gullies the assessed data have been used to test the physically based ephemeral gully erosion model egem and to compare its performance with the value of simple topographical and morphological indices in the prediction of ephemeral gully erosion analysis shows that egem is not capable of predicting ephemeral gully cross sections well although conditions for input parameter assessment were ideal some parameters such as channel erodibility critical flow shear stress and local rainfall depth showed great uncertainty rather than revealing egem s inability of predicting ephemeral gully erosion this analysis stresses the problematic nature of physically based models since they often require input parameters that are not available or can hardly be obtained with respect to the value of simple topographical and morphological indices in predicting ephemeral gully erosion this study shows that for winter gullies and summer gullies respectively over 80 and about 75 of the variation in ephemeral gully volume can be explained when ephemeral gully length is known moreover when previously collected data for ephemeral gullies in two mediterranean study areas and the data for summer gullies formed in the belgian loess belt are pooled it appears that one single length l volume v relation exists v 0 048 l 1 29 r 2 0 91 these findings imply that predicting ephemeral gully length is a valuable alternative for the prediction of ephemeral gully volume a simple procedure to predict ephemeral gully length based on topographical thresholds is presented here secondly the empirical length volume relation can also be used to convert ephemeral gully length data extracted from aerial photos into ephemeral gully volumes

solar and galactic cosmic ray records of the fermo h chondrite regolith breccia we demonstrate the presence of solar flare as well as neutron capture effects in the isotopic composition of rare gases in the fermo regolith breccia acquired on its parent body based on the measurements of tracks rare gases and radionuclides the track density along a 3 2 cm long core decreases by a factor of about 6 and by more than a factor of 13 within the meteorite indicating small 2 9 cm and asymmetrical ablation rare gases show a large trapped component the isotopic ratios particularly 20 ne 22 ne 11 and 20 ne 36 ar 10 are indicative of a solar component the galactic cosmic ray exposure age is determined to be 8 8 ma activities of a dozen radionuclides ranging in half life from 16 day 48 v to 0 73 ma 26 al are consistent with their expected production rates track rare gas and radionuclide data show that the meteoroid was a small body 120 kg and had a simple one stage exposure history to cosmic rays in the interplanetary space however 82 kr and 128 xe show an excess due to neutron irradiation on the parent body of the meteorite the presence of solar gases and the neutron capture effects indicate several stages of irradiation on the parent asteroid the chemical composition of fermo confirms that it belongs to the h group of ordinary chondrites with lithic clasts having varying compositions 15 n is found to be 8 3 1 2 0 close to the typical values observed in h chondrites

nitrogen isotopic compositions of iron meteorites abstract iron meteorites analyzed in this study have nitrogen concentrations 70 g g and 15n from 90 to 150 although the iron meteorites have a large range of 15n most have values more negative than 50 the nitrogen isotopic compositions were established by cosmochemical processes and were little modified by fractional crystallization or other chemical processes within the parent bodies the data do not suggest the existence of a well mixed solar nebular reservoir for nitrogen as was already inferred from data from stony meteorites the range of 1100 observed for 15n in bulk meteorites is probably too large to be accounted for by physical and chemical mass dependent fractionation processes in the solar nebula and thus reflects nebular inhomogeneities of nucleosynthetic origin nitrogen isotopes may serve as fingerprints for different reservoirs preserved in various parent bodies in a manner similar to that observed for oxygen isotopes in stony meteorites and oxygen bearing phases of stony irons

fall recovery and characterization of the novato l6 chondrite breccia the novato l6 chondrite fragmental breccia fell in california on 17 october 2012 and was recovered after the cameras for allsky meteor surveillance cams project determined the meteor s trajectory between 95 and 46 km altitude the final fragmentation from 42 to 22 km altitude was exceptionally well documented by digital photographs the first sample was recovered before rain hit the area first results from a consortium study of the meteorite s characterization cosmogenic and radiogenic nuclides origin and conditions of the fall are presented some meteorites did not retain fusion crust and show evidence of spallation before entry the meteoroid was 35 5 cm in diameter mass 80 35 kg with a cosmic ray exposure age of 9 1 ma if it had a one stage exposure history a two stage exposure history is more likely with lower shielding in the last few ma thermoluminescence data suggest a collision event within the last similar to 0 1 ma novato probably belonged to the class of shocked l chondrites that have a common shock age of 470 ma based on the u th he age of 420 220 ma the measured orbits of novato jesenice and innisfree are consistent with a proposed origin of these shocked l chondrites in the gefion asteroid family perhaps directly via the 5 2 mean motion resonance with jupiter novato experienced a stronger compaction than did other l6 chondrites of shock stage s4 despite this a freshly broken surface shows a wide range of organic compounds less

update on terrestrial ages of antarctic meteorites abstract cosmic ray produced 36 cl half life 3 01 10 5 years has been measured in 90 antarctic meteorites by accelerator mass spectrometry the terrestrial ages of the meteorites were calculated from the results after excluding possible paired objects 138 terrestrial ages from 18 different locations are available from 14 c 81 kr and 36 cl measurements for application to antarctic meteorite and glaciological studies the terrestrial ages of allan hills meteorites vary from 2000 years to 1 million years and are clearly longer than those of yamato meteorites and other antarctic meteorites the oldest allan hills meteorites were found close to the eastern edge and in the southeast of the main icefield among all antarctic meteorites measured to date only l and ll chondrites have terrestrial ages older than 370 000 years

nitrogen isotopes in bulk ordinary chondrites nitrogen isotopic compositions of twenty one ordinary chondrites were measured using a stepwise combustion technique we observed a good correlation between the abundances of cosmogenic15n and cosmogenic 38ar we obtained a relationship between the abundances of these two cosmogenic nuclides as follows 15nc atoms g 16 0 3 7 38arc atoms g using this relationship the cosmogenic nitrogen production rate in l chondrites is calculated to be 5 0 1 2 10 12 g 15n g myr assuming the cosmogenic38ar production rate given by eugster 1988 this value is consistent with the production rate on the lunar surface estimated by becker et al 1976 isotopic ratios of trapped nitrogen in ordinary chondrites seem to be heterogeneous among both unequilibrated and equilibrated meteorites heterogeneity among the latter are well observed in this study the isotopic ratios of the trapped components seem to differ by more than 110 ranging from 18 observed in guaren a h6 to 95 observed in jilin h5 a lack of correlation between nitrogen abundances and isotopic ratios indicates that differences in nitrogen isotopic ratios are not produced by mass dependent isotopic fractionation an inverse correlation between nitrogen abundances and the degree of thermal metamorphism is observed among most of the unequilibrated chondrites nitrogen abundances decrease from 8 25 p p m to 1 p p m with increasing petrographic subtype from 3 4 3 9 the nitrogen abundance in equilibrated chondrites is generally higher than the amount expected by extending the trend observed among unequilibrated ones this is probably because contaminating nitrogen masked the trend at small amounts of trapped nitrogen

assessing the susceptibility to water induced soil erosion using a geomorphological bivariate statistics based approach the aim of this study was the assessment at basin scale of the susceptibility to water induced soil erosion processes i e gully erosion and sheet rill erosion using geomorphological analysis geographical information systems gis and bivariate statistics the study was carried out in a watershed located in southern italy a detailed analysis of the pre existing literature led to select lithology land use slope angle and slope aspect as soil erosion determining factors dfs as they are non redundant and affect both the soil forming processes that control soil erodibility and the erosive power of running waters water produced erosional landforms such as gullies and areas severely affected by sheet rill erosion were surveyed and mapped using classical techniques of geomorphological analysis the gis processing of the geomorphological data allowed calculating the areal density of these landforms in each df class weighting values wi corresponding to the susceptibility level of each df class were calculated using bivariate statistics finally gis overlay procedures of the thematic maps previously reclassified on the basis of the calculated wi allowed to produce two susceptibility maps i e gully erosion and sheet and or rill erosion susceptibility map the soil geomorphological coherence of the produced results has been checked and widely discussed in the framework of the pre existing literature both the geomorphological coherence of the calculated wi and the results of the validation procedure suggested a good reliability of the method which is also relatively easy to apply and update

testing gis morphometric analysis of some sicilian badlands abstract calanchi badlands are erosion landforms characterized by areas with scarce or absent vegetation steep slopes knife edge divides and high erosion rates they are originated by a combination of morphogenetic processes partly similar to those shaping bigger fluvial landforms and therefore can be considered as field laboratories this paper presents the results of an investigation carried out in two badland sites located in sicily where the geometry of 25 calanchi has been characterized using digital elevation models having a mesh size equal to 2 m for each landform a power length volume relationship is established this relationship demonstrates that length of calanchi channels can be used as a reliable predictor of eroded volume as already verified for smaller linear erosion landforms such as rills ephemeral and permanent gullies moreover length volume width and depth of calanchi are combined into two dimensionless groups allowing to establish a morphological similarity between rills ephemeral permanent gullies and the studied badlands furthermore the hack s law which relates channel length to drainage basin area is applied to the 25 calanchi basins obtaining an exponent of this power law smaller than 0 5 this result indicates that basins do not become necessarily more elongate with increasing size finally the relationships between maximum length and width of the landforms are analyzed demonstrating that calanchi basins become wider and not longer and narrower when evolving and increasing their size

fall classification and cosmogenic records of the sabrum ll6 chondrite the petrographic and chemical characteristics of a fresh indian meteorite fall at sabrum are described its mean mineral composition is defined by olivine fa31 4 orthopyroxene fs25 1 wo2 0 clinopyroxene wo45en45 6fs9 4 and plagioclase an10 6ab83 6or5 8 the meteorite shows moderate shock features which indicate that it belong to the s4 category based on mineralogical and chemical criteria the meteorite is classified as ll6 brecciated veined chondrite several cosmogenic radioisotopes 46sc 7be 54mn 22na and 26al noble gas he ne ar kr and xe nitrogen isotopes and particle tracks density have been measured concentrations of cosmogenic 21ne and 38ar indicate that its cosmic ray exposure is 24 8 ma small amounts of trapped kr and xe consistent with petrologic class 5 6 are present the track density in olivines is found to be 1 3 0 3 x 10 6 cm 2 activities of most of the short lived isotopes are lower than those expected from solar cycle variation 22na 26al 1 12 0 02 is found to be significantly anomalous being approximately 25 lower than expected from the climax neutron monitor data these results indicate that the cosmic ray flux during the terminal segment of the meteoroid orbit was low the activities of 26al and 60co and the track density indicate small meteoroid size with radius 15 cm

petrography classification oxygen isotopes noble gases and cosmogenic records of kamargaon l6 meteorite the latest fall in india a single piece of meteorite fell on kamargaon village in the state of assam in india on november 13 2015 based on mineralogical chemical and oxygen isotope data kamargaon is classified as an l chondrite homogeneous olivine fa 25 0 7 and low ca pyroxene fs 21 0 4 compositions with percent mean deviation of 2 further suggest that kamargaon is a coarsely equilibrated petrologic type 6 chondrite kamargaon is thermally metamorphosed with an estimated peak metamorphic temperature of 800 c as determined by two pyroxene thermometry shock metamorphism studies suggest that this meteorite include portions of different shock stages e g s3 and s4 stoffler et al 1991 however local presence of quenched metal sulfide melt within shock veins pockets suggest disequilibrium melting and relatively higher shock stage of up to s5 bennett and mcsween 1996 based on noble gas isotopes the cosmic ray exposure age is estimated as 7 03 1 60 ma and nitrogen isotope composition 15n 18 also correspond well with the l chondrite group the he u th and k ar yield younger ages 170 25 ma 684 93 respectively and are discordant a loss of he during the resetting event is implied by the lower he u and th age elemental ratios of trapped ar kr and xe can be explained through the presence of a normal q noble gas component relatively low activity of 26al 39 dpm kg and the absence of 60co activity suggest a likely low shielding depth and envisage a small preatmospheric size of the meteoroid 10 cm in radius the kr isotopic ratios 82kr 84kr further argue that the meteorite was derived from a shallow depth

hydraulics and erosion in eroding rills rills often act as sediment sources and the dominant sediment and water transport mechanism for hillslopes six experiments were conducted on two soils and a uniform sand using three experimental methodologies the results of this study challenge the assumption often used in hydrologic and erosion models that relationships derived for sheet flow or larger channel flow are applicable to actively eroding rills velocity did not vary with slope and reynolds number was not a consistent predictor of hydraulic friction this result was due to interactions of slope gradient flow rate erosion and the formation of rill roughness bed structures and head cuts a relationship for rill flow velocities was proposed stream power was found to be a consistent and appropriate predictor for unit sediment load for the entire data set while other hydraulic variables were not the data for stream power and sediment load fit the form of a logistic curve r2 0 93 which is promising relative to recently proposed erosion models which are based on probabilistic particle threshold theory

martian atmosphere like nitrogen in the orthopyroxenite alh84001 abstract isotopic and elemental compositions of nitrogen neon and argon in the martian meteorite alh84001 were studied two whole rock samples of alh84001 57 were analyzed with detailed stepped combustion experiments from 200 to 1200 c with every 100 c and 200 c respectively with laser ablation experiments for melting the samples nitrogen with 15 n 418 44 and 366 15 after correction for cosmogenic nitrogen were obtained at 800 c which are the highest 15 n values ever found among shergottites nakhlites chassignite meteorites the heavy nitrogen in alh84001 may have the same origin as that in the glass portions of two shergottites eeta79001 and zagami and is likely to have been derived from the martian atmosphere however when and in which phase martian atmosphere like nitrogen was trapped in alh84001 is still unknown one possibility inferred from the released temperatures is that nitrogen is sited in maskelynite on the plot of 15 n versus ar n diagrams of 15 n vs 40 ar 14 n and 36ar 14 n the data points for alh84001 in this study form a linear trend which apparently differs from that defined by glass portions of the shergottites eeta79001 and zagami the present trend also differs from the trend seen by grady et al for alh84001 the 40 ar 14 n and 36 ar 14 n ratios obtained in this work are relatively smaller than those of the shergottites on such plots indicating the following possibilities 1 martian atmospheric ar n ratio changed throughout geologic time e g 4 ga without a large change in 15 n that is alh84001 trapped ancient martian atmospheric nitrogen and ar n ratio was initially lower or 2 different trapping sites or mechanisms between alh84001 and the shergottite glasses made an apparent difference in the ar n ratio and elementally fractionated gases were trapped in alh84001 in the case 1 either increase in ar concentration in the martian atmosphere due to preferential ar degassing from the martian interior or preferential escape of atmospheric nitrogen must have occurred nitrogen with 15 n from 13 to 5 and with 15 n 200 were released at low and high temperatures respectively the former may have been derived from the martian lithosphere or terrestrial atmosphere and the latter must be of cosmogenic nitrogen the largest amount of 40 ar was released at temperatures similar to the largest release of heavy nitrogen of 800 c according to reported k abundance in alh84001 the majority of 40 ar in our samples is considered to be of radiogenic origin

the k kakangari chondrite grouplet abstract the kakangari lew 87232 and lea co 002 chondrites have a similar set of petrologic and oxygen isotopic characteristics that distinguishes them from other chondrite groups they are here established to constitute a single chondrite grouplet the k after kakangari chondrites the k chondrites have 1 high matrix abundances 33 77 vol as do carbonaceous chondrites 2 metal abundances 6 10 vol that are similar to the h group ordinary chondrites 3 average mafic silicate compositions average kakangari olivine fa2 2 enstatite fs4 4 that indicate an oxidation state intermediate between h and e chondrites 4 matrix that differs from that in other chondrite groups in being enstatite rich with compositions more mg rich average fs3 than those in the chondrules 5 refractory lithophile element abundances

rill network development and sediment budgets threshold conditions for rill incision are well known but few studies have examined the effect of network geometry on water and sediment fluxes within an evolving rill system this paper reports the first in a series of studies designed to identify the influence of soil properties on rill network and confluence geometry and on water and sediment fluxes in rill systems the object of this study was to prepare detailed rill network water and sediment budgets identifying important sources and sinks simulated rainfall experiments were carried out on a canadian silt loam soil in a 7 1 m 2 4 m flume on a 5 slope rill networks of varying complexity developed which were ultimately constrained by flume boundaries sediment and water fluxes and hydraulic conditions were measured within networks and at a terminal weir networks evolved by initial knickpoint incision in the lower flume as flow shear velocities reached critical levels of 4 5 5 cm s 1 followed by headward migration and tributary development microtopography determined tributary location but the timing and intensity of development were controlled by the incision and migration rate of the main channel which changed local thalwegs and base levels raising shear velocities on side slopes above critical levels sediment discharge at the weir broadly reflected rill incision intensity and transport limited conditions but as active incision moved headward the linkage became attenuated and identification of discrete erosional incidents e g local bank collapse in the signal of the weir record became very difficult detailed water and sediment budgets showed much more complex patterns of localized incision and deposition within networks strongly influenced by local changes in thalweg and in water discharge due to seepage or return flow and by the effect of confluences on hydraulic conditions results indicate the value of detailed sediment budgets in interpreting weir water and sediment flux records and the necessity of linking such measurements for erosion plots and hillslope segments to rill network characterization experimental results are consistent with a simple model of rill system evolution based on channel incision headward migration and the critical shear velocities for rill initiation copyright 2000 john wiley sons ltd

testing the use of an image based technique to measure gully erosion at sparacia experimental area the first part of this investigation was aimed at testing the use of a three dimensional 3d digital terrain model dtm and a quasi tridimensional 2 5d digital elevation model dem obtained by a large series of oblique images of eroded channels taken from consumer un calibrated and non metric cameras for two closed earth channels having a different sinuosity the ground measurement of some cross sections by a profilometer p was carried out the real volume of each channel was also measured by waterproofing it by a plastic film and filling it with a known volume of water the comparison among the three methods 3d 2 5d and p pointed out that a limited underestimation of the total volume always occurs and that the 3d method is characterized by the minimum difference between measured and real volume this preliminary analysis allowed to conclude that 3d model can be used as benchmark and the 2 5d model is accurate enough to describe the investigated earth channels in the subsequent part of the investigation the three ground measurement methods were applied for surveying of an ephemeral gully eg channel at the sparacia area using the 3d model as benchmark the morphological and hydraulic variable values of the 24 surveyed cross sections determined by both 2 5d model and profilometer were compared this comparison showed that the estimate error is generally less than 10 the eg measurements carried out by the three methods agreed with the available literature measurements and supported the applicability both of the empirical relationship between eg length and its eroded volume and the theoretical dimensionless relationship among the morphological variables describing the channelized erosion process finally it was demonstrated that the effect of the distance interval on the eg volume measurement by 3d and 2 5d models is negligible for the investigated eg

cerium a chemical tracer for paleo oceanic redox conditions abstract the ce anomalies found in marine carbonates provide a sensitive indicator for the study of paleo oceanic redox conditions the dependency of cce the observed ce concentration and cepo04 the activity of the cepo4 complex to the po2 ph and pco2 of seawater can be used for deciphering some aspects of the paleo ocean chemistry and is log c ce log cepo 0 4 13 2 0 25 log p o 2 3 0 ph 1 95 0 25 log p o 2 1 50 log p co 2 1 50 log ca the ph which is related to pco2 and po2 are major factors for controlling the ce concentration in seawater therefore ce anomalies ceas ce observed ce interpolated between la and pr or nd serve as indicators for ph or pco2 or po2 changes nearly uniform ce abundances found in pacific 5000 m water columns piepgras and jacobsen 1988 and the ceas in ichthyoliths can be explained using this model a general cea shift in sediments from d s d p holes 525a 530a b 516 516f suggest that the entire south atlantic water redox condition changed from reducing to oxidizing at 56 my in the north atlantic the galicia margin samples show a redox change between 132 148 my indicating active surface currents between the atlantic ocean and the shallow sea off the iberian peninsula the carbonate samples from d s d p hole 316 in the central pacific yielded an average cea of 0 15 0 01 which is 2 3 the ceas observed in deep pacific seawater by piepgras and jacobsen 1988 the relative enrichment of ce in these samples is ascribed to coprecipitation of ce oh 4 onto fe mn o coatings the striking similarities in the trace element profiles of ree sc hf th and ceas and the low u abundances 0 08 ppm in many marine carbonates indicate insignificant ce redox and trace elemental concentration changes for the pacific ocean over the past 95 my no significant ce redox change occurred in the pacific ocean within k t boundary one 240 my china limestone deposited under oxic sedimentary conditions yielded a cea of 0 53 calculations indicate a pco2 of 1 9 present value prevailed over the 240 my tethyan ocean u th ratios and low u concentrations are diagnostic indicators for obtaining reliable ceas in marine carbonates and perhaps for biogenic apatites and conodonts as well

a simulation of rill bed incision processes in upland concentrated flows abstract quantifying rill bed incision provides fundamental information for process based erosion modeling while the morphodynamic and hydrodynamic mechanism in bed incision processes are still unclear thus experiments were conducted to examine rill bed incision processes in upland concentrated flows dems 2 mm 2 mm resolution obtained by photogrammetry were used for rill bed morphology analysis rill channel 2 0 m long 0 08 m wide and 0 15 m deep with two slope gradients 15 and 20 were subjected to four overland flow rates 1 0 2 0 3 0 and 4 0 l min 1 the results showed that sediment delivery rill bed incision rate and average rill depth increased with inflow rate and bed slope sediment delivery increased from 0 060 to 0 226 kg min 1 per 1 l min 1 inflow increment and from 0 043 to 0 207 kg min 1 when bed slope increased from 15 to 20 in a well developed rill channel rill bed incision could be divided into three phases pre headcut formation dominated by rill flow shear stress headcut incision dominated by headcut advancing and post headcut incision dominated by rill flow shear stress headcut incision phase which only accounted for 65 of rill bed sediment in the pre headcut formation phase rill flow velocity shear stress and stream power increased with increases of inflow rate and slope gradient conversely flow velocity showed no evident trend with increased inflow rate and bed slope during headcut incision phase initial headcut advancing rate could be predicted by a non linear function based upon soil characteristics rill flow shear stress and headcut height sediment delivery showed a power function with the product of inflow rate and squared bed slope because rill bed incision is dominated by headcut advancement and incision practices for controlling headcut initiation should be implemented to decrease hillslope soil loss

gully erosion susceptibility assessment by means of gis based logistic regression a case of sicily italy article i nfo article history this research aims at characterizing susceptibility conditions to gully erosion by means of gis and multivariate statistical analysis the study area is a 9 5 km 2 river catchment in central northern sicily where agriculture ac tivities are limited by intense erosion by means of field surveys and interpretation of aerial images we prepared a digitalmap of thespatial distribution of 260 gulliesinthestudy area inaddition fromavailable thematicmaps a 5 m cell size digital elevation model and field checks we derived 27 environmental attributes that describe the variability of lithology land use topography and road position these attributes were selected for their potential influence on erosion processes while the dependent variable was given by presence or absence of gullies within two different types of mapping units 5 m grid cells and slope units average size 2 66 ha the functional re lationships between gully occurrence and the controlling factors were obtained from forward stepwise logistic regression to calculate the probability to host a gully for each mapping unit in order to train and test the predictive models three calibration and three validation subsets of both grid cells and slope units were randomly selected results of validation based on roc receiving operating characteristic curves attest for acceptable to excellent accuracies of the models showing better predictive skill and more stable performance of the susceptibility model based on grid cells

distribution morphology and influencing factors of rills under extreme rainfall conditions in main land uses on the loess plateau of china abstract rill erosion is one of the main forms of soil erosion of the hillslopes on the loess plateau of china few studies have evaluated the effects of land use on the distribution and morphology of rills under extreme rainstorms a total of 50 rill survey sites were selected in a typical watershed of the loess plateau of china to investigate the rill distribution and morphology of three land uses fallow land fl slope farmland sf and annual grassland ag under extreme rainstorm conditions called 7 26 rainstorm seven parameters rill width rill depth width depth ratio cross section area rill density degree of rill dissection and rill erosion modulus were used to characterize rill morphology and the basic soil and vegetation properties bulk density particle size distribution and vegetation coverage and topographic factors slope length gradient direction were measured it was found that rills developed on three land uses and those with widths ranging from 5 to 20 cm accounted for 80 rills developed on fl were deeper than those on sf and ag almost all rills on fl had a depth of 5 20 cm 90 3 while the depth of rills on sf and ag were mainly smaller than 15 cm 91 5 and 91 9 respectively in addition to width rill depth and cross section area of sf and ag were also significantly less than those of fl sf and fl had a relatively high width depth ratio and dissection degree however land use had no significant effect on rill density crop plantations sf and grass restoration ag significantly reduced rill erosion modulus 28 70 and 45 07 reduction respectively land use topography soil and vegetation factors significantly affected rill morphology p 0 001 based on redundancy analysis rda and can explain 48 0 of the total variability of rill morphology with slope length vegetation coverage and slope gradient having the greatest influences most of the rill morphological parameters significantly decreased as the vegetation coverage increased but they significantly increased with increasing slope length and slope gradient this study clearly illustrates the severe rill erosion caused by this rainstorm and indirectly indicates that crop harvesting fl aggravates rill erosion and that revegetation ag can effectively contain rill erosion therefore rehabilitation efforts should be focused on revegetation grassland and or woodland on steep slopes to control soil erosion

a new empirical model for estimating calanchi erosion in sicily italy abstract calanchi plural of calanco are typical badland landforms of the italian landscape they consist of dense networks of v shaped valleys with a sparse or absent vegetation cover which frequently develop on unconsolidated or poorly consolidated clayey deposits in this paper the dimensional analysis and the incomplete self similarity theory were used to deduce a model relating the volume of sediments eroded from the calanchi area to a set of geometric attributes of their tributary areas the morphometric characteristics of 209 calanchi basins were used to calibrate and validate the model the predictive skill of the model was assessed by calculating the mean square error and the nash sutcliffe model efficiency coefficient the model was found to provide a reliable prediction of eroded volume from basins entirely covered by calanchi landforms as well as from basins only partially affected by badland erosion processes furthermore as the residuals between the calculated and the measured volume of the eroded material are normally distributed the deterministic model may be considered complete meaning that no other variables are necessary to explain the studied physical process in other words the model is able to predict erosion volume in calanchi landforms from a deterministic point of view

geochemistry of some k t sections in india abstract a number of marine as well as continental k t sections in india particularly around the deccan volcanic regime have been analyzed to obtain concentration profiles of some platinum group and other trace elements specifically to search for anomalous levels of iridium except for the um sohryngkew river usr section in meghalaya where iridium is found to occur at an anomalously high level in the k t boundary layer all other sections show low levels in the range of 10 to 120 pg g the iridium profile in the usr section is characterized by a sharp peak of 12 1 ng g in a 1 5 cm thick limonitic layer superimposed on a broad band of 0 2 ng g extending over a 50 20 cm thick section beyond which ir decreases to the base level of 0 02 ng g both in the tertiary as well as in the cretaceous high ir is accompanied by high os but the os ir ratio in the peak 0 37 is different from the os ir ratio of 2 measured in the broad band the ir profile in the usr section seems to be consistent with fallout of cometary debris preceding and following the main impact the measurements at other sites in the deccan suggest that the iridium inventory of the deccan is too low to account for the high iridium observed in the ktb layer all over the world but may be sufficient to give rise to its enhancement adjacent to the ktb peak

measurements of rill and gully erosion in sicily this article reports the results of a field investigation aimed to characterize the morphology of both rills monitored at sparacia experimental area and two ephemeral gullies egs located in the tremamargi basin sicily italy at first the available literature data together with the measurements carried out in this investigation were used to show that the eg length is a key parameter for the estimation of the eroded volume then the comparison among the pairs length and volume corresponding to measured rills egs and gullies showed that the exponent of the power relationship is independent of the channelized erosion type rill eg and gully while a different scale factor has to be used for each erosion process finally a single relationship applicable to all channelized erosion processes was deduced applying the dimensional analysis and the self similarity theory copyright 2011 john wiley sons ltd

a radiometric age for the cretaceous tertiary boundary based upon k ar rb sr and u pb ages of bentonites from alberta saskatchewan and montana bentonites associated with coal seams at the north american cretaceous tertiary k t boundary in the red deer valley of alberta in the frenchman valley of saskatchewan and near hell creek montana were dated by the k ar rb sr and u pb methods based upon palynological stratigraphic correlation and the presence of a sharp iridium anomaly the three sampled bentonite horizons all occur less than 1 m above the established k t boundary there is evidence of possible systematic errors giving dating results outside nominal statistical error values despite possible constant errors the weighted mean of nine average dates is calculated as 64 3 1 2 ma 2 standard deviation an unweighted averaging produces a grand mean age of 64 4 1 2 ma