structural characterization of natural loess and remolded loess under triaxial tests this paper characterizes the microstructural evolution of saturated natural loess from a site in jingyang china during triaxial test along two stress paths for comparison the same soil in remolded state is also characterized mercury intrusion porosimetry mip scanning electron microscopy sem and environmental scanning electron microscopy esem were used for the microstructure investigation results show that the microstructure of natural loess is similar to that of remolded loess before the consolidated undrained cu triaxial tests including conventional triaxial compression ctc test and reduced triaxial compression rtc test on the contrary their microstructures are different after the tests deeper examination shows that loading led to a significant change of inter aggregate pores without modifying the intra aggregate pores in addition the volume of inter aggregate pores after the rtc test is greater than that after the ctc test under the same consolidation stress the microstructure features of natural and remolded loess after the tests are further used to analyze the macro mechanical behavior for better understanding the relationship between them the results show that it is the cementation bonds of which breakage is influenced by stress path and confining pressure that play important roles in the strength and deformation behavior

a comparison of the finite element method and analytical method for modeling unexploded ordnance using magnetometry unexploded ordnance uxo is military ordnance that was fired dropped or emplaced but failed to function as intended and thus constitutes an explosive hazard uxo is a worldwide problem that kills or maims thousands of civilians each year magnetic surveys are an efficient means of locating uxo containing ferrous metal when geologic conditions are sufficiently free of magnetic soil and rock however discrimination of uxo from non uxo is complicated by the fact that uxo is often associated with high levels of clutter from ordnance fragmentation to date magnetic modeling of uxo has been based on calculations for a simple body of revolution geometry prolate spheroids we conducted an investigation to show how numerical modeling in particular finite element modeling of more realistic geometries compares to prolate spheroid results our results show that the calculated dipole moment response for complex models resembling actual uxo is up to 50 higher than the dipole moments for the prolate spheroid model we also found that altering the shape of a model from a prolate spheroid to a complex shape has a greater effect on dipole moment than maintaining the same shape and altering the volume finally in comparing the surface response from our models to real total field magnetic data we find that complex models more closely match actual field data than prolate spheroid models we suggest that modeling and ultimately discrimination using more realistic uxo shapes could result in significant improvements in distinguishing uxo from magnetic clutter and geology

problems in identifying the effects of structure and critical state in a soil with a transitional behaviour this work shows that some soils with an intermediate behaviour between clays and sands do not have a unique compression line as has also been pointed out by martins et al it has been shown here that a unique critical state line could not be determined for the remoulded soil although the results shown here are for a reconstituted residual soil similar behaviour in compressibility has been found in silts and mixtures of sand and kaolin however it has been found that the critical state framework can be applied using a family of parallel critical state lines depending on the initial specific volume one of the questions raised by this work is how the effects of structure can be quantified if the intrinsic properties of the remoulded material are not unique the compression and critical state lines of the remoulded material are not only non unique but also of a distinctly different gradient from the natural material

magnetostratigraphical dating of loess deposits in china the age of chinese loess deposits has long been disputed biostratigraphical and earlier magnetostratigraphical investigations placed the entire loess formation within the pleistocene the new palaeomagnetic measurements reported here on a bore hole section near lochuan shaanxi province suggest a clearly defined magnetic polarity zonation which extends below the olduvai subchron a late pliocene age of 2 4 myr is assigned to the oldest loess sediments measured the intensity variations of natural remanent magnetization nrm and low field magnetic susceptibility are indicative of climatic changes during loess deposition

influence of structure on the behavior of a saturated clayey loess an intensive experimental investigation by means of triaxial and oedometer tests was performed on a clayey loess that was retrieved from two depths at a location on the southern chinese loess plate

changes in sand content of loess deposits along a north south transect of the chinese loess plateau and the implications for desert variations geological records have shown that the deserts east of the helan mountains in northern china were covered by grass during the holocene optimum whereas during marine oxygen isotope stages 2 and 4 distribution of the deserts was almost the same as at present the wide advance retreat cycles of the deserts may have exerted an important control on grain size changes in the loess of the loess plateau by altering the distance between the source and the accumulation zone of the loess this challenges the widely accepted model that winter monsoon winds were the sole factor responsible for spatial and temporal changes in loess texture to observe spatial changes in sedimentological characteristics of loess during the last glacial interglacial cycle the texture of loess was measured along a north south transect of the loess plateau this transect consists of nine loess sections starting at yulin in the transitional region between the loess plateau and the mu us desert and ending at weinan in the southernmost part of the loess plateau southward changes in sand 63 m content along the transect suggest that variations in desert extent have indeed played a significant role in loess grain size distributions particularly in the northern part of the loess plateau it is proposed that sand content 63 m of loess in the loess desert transitional zone may be used as a proxy indicator for proximity to the desert margin

the mechanics of subglacial sediment an example of new transitional behaviour a series of isotropic compression tests and drained and undrained triaxial compression tests have been performed on glacial sediment from iceland langjokull sediment which is well graded is thou

enhancement of magnetic data by stable downward continuation for uxo application the magnetic method has been proven to be a successful geophysical tool for the detection of unexploded ordnance uxo aeromagnetic surveys are advantageous since they can acquire data over large areas the downside is that magnetic anomalies due to multiple metallic targets can overlap significantly due to flight height restrictions such overlap combined with the acquisition noise may significantly decrease the signal to noise ratio of data these adverse effects can mask the true level of contamination at a site during the initial assessment based on the magnetic method as well as decrease the overall effectiveness of discrimination during the active clearance stage we propose a method to ameliorate these difficulties using stable downward continuation which reconstructs the field at a lower observation height from the observed data the stable algorithm formulates the downward continuation as an inverse problem and incorporates the expected power spectrum of uxo anomalies the power spectrum preserves the spectral properties and subdues the amplification of high frequency noise synthetic and field examples show that the algorithm can reliably reconstruct the magnetic anomaly at the ground surface within the limitation imposed by the noise the reconstructed field exhibits significant enhancement compared to the original data

papoose flat pluton forceful expansion or postemplacement deformation intense solid state deformation in the margin of the papoose flat pluton white mountians california and severe attenuation of nearby wall rocks encouraged earlier workers to suggest that this pluton was emplaced by blistering or in situ radial expansion reexamination of the pluton and wall rocks indicates that many features present in and around the pluton are not compatible with this model these features include the following 1 lack of compositional zoning or magmatic foliations in the pluton 2 lack of high temperature solid state deformation or a transition from magmatic to high temperature solid state flow 3 the presence of widespread moderate to low temperature deformation in the pluton 4 a northwest southeast trending stretching lineation and associated kinematic indicators of sinistral shear everywhere within and adjacent to the western half of the pluton 5 significant cleavage transposition after the growth of porphyroblasts in the contact metamorphic aureole and 6 upright to inclined folds with a steeply dipping axial planar cleavage in wall rocks that postdate aureole cleavages and porphyroblasts many other plutons in the white and inyo mountains also have deformed western or northwestern margins and weakly deformed eastern margins instead of interpreting all of these plutons as post tectonic and inferring that they all expanded in a western direction more the authors suggest that significant cretaceous regional deformation occurred during and after emplacement of these plutons less

compositional heterogeneity of the ancient martian crust analysis of ares vallis bedrock with themis and tes data 1 themis multispectral and thermophysical information combined with tes hyperspectral and albedo data is used as a powerful high spectral spatial resolution tool to investigate the mineralogic heterogeneity of ancient martian crust exposed in ares vallis bedrock three major spectral units are present in the upper ares vallis region 1 a regional unit that is composed primarily of a high silica si o 0 35 component with lesser amounts of plagioclase and pyroxene and is associated with channel wall rock and surrounding plains 2 a pyroxene and olivine rich rock unit exposed as a 250 m thick contiguous layer in the wall rock of ares vallis as well as in isolated exposures in the plains outside of the channel and 3 a unit composed of plagioclase pyroxene and lesser high silica component s si o 0 35 that primarily occurs as low albedo sand the spatial and stratigraphic distribution of these units suggests that the pyroxene and olivine enriched unit may be extrusive and or intrusive in origin indicating that this region experienced either a single stage or repeated episodes of olivine enriched magmatism during the first 1 5 gyr of crust formation this olivine enrichment may have been caused by a larger degree of mantle partial melting facilitated by higher mantle temperature melting from a more depleted mantle source and or less olivine fractionation relative to regional rock parent magmas the olivine rich unit is similar in thermophysical character to previously published olivine bearing terrains on mars but the derived modal mineralogy consists of 20 more pyroxene and less plagioclase than those terrains

loess stratigraphy in central china abstract loess sequences in central china provide a detailed record of climate changes during the last 2 5 million years at least 44 major shifts from glacial to interglacial conditions occurred during this time in china prolonged loess deposition lasting more than 40 millennia occurred eleven times with only four of these intervals in brunhes chron the climate oscillations took place with increased frequency between 2 4 and 0 5 ma compared to the last half million years major shifts toward cooler and drier climates occurred at about 2 4 ma 1 2 ma and 0 5 ma while less pronounced shifts are dated to 1 65 ma 0 8 ma and 0 2 ma three of the last four reversals of the earth s magnetic field whose lithostratigraphic position has been detail are recorded in a glacial deposit the low field magnetic susceptibility of loess and soils which reflects the concentration of ultrafine magnetite is related to the degree of pedogenesis and serves as a proxy measure of climate the accumulation rate of the magnetite was fairly constant throughout the last 1 2 million years and can serve as a measure of time susceptibility records from localities near xifeng and luochuan located 160 km apart are compared and used to define informal lithostratigraphic units in the loess plateau of china

multispectral remote sensing as stratigraphic and structural tool wind river basin and big horn basin areas wyoming stratigraphic and structural analyses of the wind river basin and big horn basin areas of central wyoming are in progress one result has been the development of an approach to stratigraphic and structural analysis that uses photogeologic and spectral interpretation of multispectral image data to characterize the attitude thickness and lithology of strata new multispectral systems that have only been available since 1982 are used with topographic data to map upper paleozoic and mesozoic strata exposed on the southern margin of the bighorn mountains landsat acquired thematic mapper tm data together with topographic data are used to map lithologic contacts measure dip and strike and develop a stratigraphic column that is correlated with conventional surface and subsurface sections aircraft acquired airborne imaging spectrometer ais and thermal infrared multispectral scanner tims data add mineralogic information to the tm column including the stratigraphic distribution of quartz calcite dolomite smectite and gypsum results illustrate an approach that has general applicability in other geologic investigations that could benefit from remotely acquired information about areal variations in attitude sequence thickness and lithology of strata exposed at the earth s surface application of our methods elsewhere is limited primarily by availability of multispectral and topographic data and quality of bedrock exposures

how unique are spectral signatures abstract recent improvements in instrumentation have made possible the acquisition of high spectral resolution image data corresponding to spectral reflectance signatures it would seem that sufficiently high spectral resolution of order 0 01 m would be adequate to permit unique discrimination of virtually any soils vegetation types and rocks but we show by example that this is not necessarily the case

hydroconsolidation and subsidence of loess studies from china russia north america and europe abstract various approaches to the widespread problem of the hydroconsolidation and subsidence of loess have been suggested these include considerations of rheology thermodynamics phase movements particle packing interparticle bonding pore structure and distribution catastrophe theory topology and simple structural frameworks chinese north american and most european investigators tend to concentrate on mechanisms of loess collapse the russian literature however retains an extra dimension two approaches the syngenetic and the epigenetic approach to the formation of subsiding loess have been defined in the literature most investigators follow a syngenetic approach which appears to be a consequence of the aeolian idea of loess deposition some russian writers in contrast promote an epigenetic approach in which collapsibility can develop in an originally noncollapsible material which can then suffer from hydroconsolidation and subsidence the basis of the phenomenon is a change in the packing structure of the major loess particles and this can be modelled using simple monte carlo methods to develop appropriate structures this paper aims to review the work done on this important subject serious investigation of hydroconsolidation and subsidence of loess began in the early nineteen forties fifty years ago and this has been reported in a piecemeal manner a detailed critical review of this diverse work is now overdue and this is presented herein in the light of recent work in the united kingdom an attempt is made to describe the process in a phenomenological and a structural sense inherent in this the role of n ya denisov as subsidence pioneer is considered

temperature and emissivity retrieval from remotely sensed images using the grey body emissivity method the problem of extracting temperature and emissivity information from thermal infrared multispectral radiance data is of great importance in remote sensing applications the earth surface temperature is a relevant parameter for climatology meteorology oceanography fire mapping wind field determination and energy balance at the atmosphere earth interface in addition ground emissivity is very important for lithological mapping geological inspection petrography the dating of lava flows etc a new method for emissivity and temperature retrieval has been developed in the authors laboratory which is based on the assumption that emissivity is a slowly varying function of wavelength it is shown that this assumption holds true for many kinds of natural targets the resulting model is called grey body emissivity and may be used to retrieve the emissivity of soils and other natural materials the problem with using an effective wavelength or a bandwidth integral in order to represent the sampled radiance is discussed thus leading to the implementation of two algorithms for the grey body emissivity it is demonstrated that one of them extensively discussed throughout the paper provides the maximum likelihood values for temperature and emissivity the other reveals two drawbacks it produces noisy processed images and works well only for target temperatures greater than 274 k comparisons with other models are carried out utilizing remotely sensed images laboratory measurements and numerical simulations the main approximations and the resulting errors contained in the considered models are briefly discussed the influence of the atmospheric effects on utilized remote sensing data is taken into account finally the authors investigate the emissivity dependence on the viewing angle theoretical predictions which rely on fresnel s and kirchhoff s laws are compared with the emissivity maps extracted from tims images over sea starting from the image data alone the procedure allows them to compute the refraction index and the absorption coefficient of the concerned marine water

age relationship of basaltic and andesitic surface compositions on mars analysis of high resolution tes observations of the northern hemisphere 1 previous mars global surveyor thermal emission spectrometer tes results have identified two principal surface compositions on mars basaltic surfaces are found primarily in the southern highlands while andesitic surfaces are found in the northern lowlands and in smaller concentrations distributed throughout the southern highlands in 1 pixel per degree composition maps the exact boundary between the basaltic and andesitic compositions is obscured by large amounts of equatorial surface dust in this work high resolution tes surface spectral data are used to identify and characterize isolated regions of basalt within the equatorial dust regions and northern lowlands generally between 20 s 60 n 0 360 w in an effort to better understand the nature of the boundary between the two compositions the purpose of refining this boundary is to more accurately determine the relationship of the compositional dichotomy with global surface morphology and derived crustal thickness results show that the basaltic surface composition is closely associated with the ancient cratered terrain morphology but is not well correlated with crustal thickness the northern extent of the tes basalt composition is also established with four exceptions there are no significant concentrations 30 surface cover of basalt greater than 400 km2 in area within the northern plains three are located within or adjacent to knobby terrain which has been suggested to be erosional remnants of the cratered highlands the fourth exception is in milankovic crater and may represent a local basalt flow or basaltic material excavated during crater formation results from this work suggest that there is a stratigraphic relationship between the basaltic and andesitic surface compositions with younger andesitic materials overlying older basaltic materials throughout the equatorial and northern plains regions

formation of recent martian gullies through melting of extensive water rich snow deposits the observation of gullies on mars indicates the presence of liquid water near the surface in recent times1 2 which is difficult to reconcile with the current cold climate gullies have been proposed to form through surface runoff from subsurface aquifers1 3 or through melting of near surface ice under warmer conditions4 but these gullies are observed to occur preferentially in cold mid latitudes2 where the presence of liquid water is less likely and on isolated surfaces where groundwater seepage would not be expected making both potential explanations unsatisfactory here i show that gullies can form by the melting of water rich snow that has been transported from the poles to mid latitudes during periods of high obliquity within the past 105 to 106 years refs 5 6 melting within this snow7 can generate sufficient water to erode gullies in about 5 000 years my proposed model for gully formation is consistent with the age and location of the gullies and it explains the occurrence of liquid water in the cold mid latitudes as well as on isolated surfaces remnants of the snowpacks are still present on mid latitude pole facing slopes and the recent or current occurrence of liquid water within them provides a potential abode for life

centrifuge model testing of a loess landslide induced by rising groundwater in northwest china abstract considerable artificial irrigation in the heifangtai area has caused the continued rise of groundwater levels which has resulted in several large scale landslides in the loess platform area considering the no 13 landslide of jiaojia in the heifangtai area as a geological archetype a series of centrifuge tests was conducted to study the deformation and failure characteristics of the slope due to the continuous rise in the groundwater level meanwhile the pore water pressure earth pressure deformation and evolution characteristics of the slope were monitored and recorded in real time furthermore isotropically consolidated undrained triaxial testing icu was conducted to investigate the static liquefaction of loess specimens which was related to the slope instability the centrifuge test results showed that a series of parallel and steep tension cracks at the top of the slope were present before the landslide which was caused by the rising groundwater the icu experimental results showed that as the pore water pressure increased strong strain softening and static liquefaction of saturated loess soils were found which was related to the sudden destruction of the slope

the post yield behaviour of four eocene to jurassic uk stiff clays a detailed study is described of the post yield behaviour of four medium plasticity heavily overconsolidated uk stiff clays sub layers of the stiff to hard gault kimmeridge and oxford clays were identified sampled and tested these along with facies investigated in an earlier london clay study had broadly similar depositional histories the intention in considering a spread of similar sediments from the jurassic to the eocene was to allow any strong effects of geological age or burial depth to be identified a strongly fissured meso structure was present in three of the four clays which had a controlling influence on their effective shear strengths considering that the representative element volume is of paramount importance in measuring the strengths of such soils all four soils were brittle in shear and when sheared to sufficient displacements developed low residual shear strengths the stiff clays were investigated further through comparisons between natural and reconstituted behaviour usi

influence of structure on shear characteristics of the unsaturated loess in lanzhou china abstract loess is typically a kind of soil with metastable structure which makes loess sensitive to collapse and sliding upon wetting such structure has thus profound influence on loess s mechanical behavior however there have been arguments about how the metastable structure influences on loess s mechanical behavior and what the mechanism behind is in this study the influence of structure on shear characteristics of the unsaturated loess in lanzhou city of china was investigated with comparison of variation of shear strength and its parameters between six pairs of the undisturbed and remolded samples it is found that the peak shear strength and strength parameters of the loess significantly reduced once its structure was destroyed while shear behavior of the loess showed little change strength parameter c was much more sensitive to structure of the loess than shear strength reduction of the loess due to change of structure should be largely attributed to breaking up of cementation bonds between particles evidenced by the difference in pore size distribution and microstructure of soil fabrics between the undisturbed and remolded samples the bonds provided by clays and carbonates contributed the most to structure of the loess with minor by soluble salts while matric suction played little role in structure of the loess

remote sensing for exploration an overview background material on measurement techniques and their physical basis as applied to rocks soils and vegetation new developments in high spectral resolution remote sensing for mineralogic and vegetation mapping modified journal abstract

relationships among vegetation climatic zonation soil and bedrock in the central white inyo range eastern california a ground based and remote sensing study to assess the effects of regional climate change using remote sensing methods we conducted integrated geologic botanical and field radiometer baseline studies on the ground in the central white inyo mountains vegetation on contrasting geologic substrates in 58 50 50 m sites was studied annually in early july and in late september 1997 2001 we quantified areal abundances of plant species by using field inventories and ground based values of the normalized difference vegetation index ndvi distributions and abundances of species are complex functions of microclimate elevation slope and facing direction seasonality soil development bedrock lithologies and albedo x ray diffraction studies demonstrate that the soils consist chiefly of in situ weathering components such as illite montmorillonite chlorite quartz carbonates and feldspars soils along higher ridges contain modest amounts of wind blown grains derived from glaciated granodioritic plutons and volcanic roof pendants of the sierra nevada light colored limestone and dolomite support only sparse amounts of sagebrush at any altitude whereas this drought tolerant species is widespread on dark argillite quartzite phyllite and granitic rocks grasses grow luxuriantly on dark granite and quartzite but poorly on carbonate bedrock trees are numerous on carbonate rocks but are uncommon on dark granite and quartzite higher albedo rocks and soils retain moisture better than darker substrates and in general support greater vegetative cover and biomass these studies provided ground control for hyperspectral data collected by er 2 aircraft along three airborne visible and infrared imaging spectrometer aviris flight lines because of the 16 m spatial resolution of the remotely sensed data only plant communities could be mapped from aviris imagery on the basis of the dominant species we identified the following communities shadscale desert scrub pinyon juniper woodlands sagebrush meadows mountain mahogany woodlands aspen woodlands bristlecone pine limber pine woodlands and alpine fell fields when judged by correlation with the 50 50 m ground based inventoried sites botanical community assignments for the june 2000 flight lines achieved an accuracy of 81 in contrast october 1996 assignments were only 65 correct reflecting low sun angle and senesced vegetation

study of the reed dolomite aided by remotely sensed imagery central white inyo range easternmost california remote sensing methods are of great value in assessing the stratigraphy and geologic structure of inaccessible terrains especially where lithologic contrasts are marked in this paper we show that such techniques can be successfully applied to a massive carbonate unit the reed dolomite exposed in the waucoba mountain blanco mountain and mount barcroft quadrangles of east central california airborne ns 001 satellite landsat tm and spot panchromatic imagery combined with conventional geologic mapping were employed to demonstrate that observed spectral variations on false color images were caused by subtle compositional variations of the dolomite based on reflectance differences and field investigations six discrete bedding units were recognized in exposures of th reed dolomite from lower to upper they are 1 very coarse grained granular gray pisolitic blocky dolomite 2 medium grained white oolitic massive dolomite 3 fine to coarse grained light gray oolitic massive crystalline dolomite and rare interbedded rusty quartzarenite 4 medium fine grained cross stratified locally ocherous brown interlayered quartzarenite tan siltstone and sandy dolomite 5 fine grained thin bedded sparsely oolitic buff dolomite and 6 fine grained fissile dull white dolomite subunit 4 and underlying subunit 3 appear to interfinger with subunit 4 representing a more proximal shelf facies in the southeast corner of the mapped area subunit 4 is present and subunit 3 is absent with the situation reversed along the western and northern portions of the range subunit 5 thins to a feather edge on the north near the barcroft granodiorite thickness variations of the different reed stratigraphic entities in the eastern and northern white inyo range may reflect attenuation caused by granitoid intrusion as well as original stratigraphic variations the broad expanse of reed dolomite directly northeast of the sage hen flat pluton is due to north south trending folds details of the white inyo anticlinorium are now better resolved in the central portion of the ra ge where previously undetected folds faults and homoclinal sections are revealed in false color imagery of the macroscopically featureless reed dolomite thickness trends and facies boundaries for the newly recognized subunits trend north south or north northeast throughout the study area locally reflecting the gentle west northwest continental shelf paleoslope of the passive margin of western north america during latest precambrian early cambrian this study is important to petroleum geologists because it demonstrates that detailed stratigraphy and structure can be determined using remote sensing techniques in semiarid regions where massive indistinct carbonate units crop out in some cases no single processing method allows spectral discrimination of all lithostratigraphic entities furthermore the spectral characteristics of a specific unit have been shown to vary even within a single image hence our work underscores the site specific limitations of individual multispectral methods and illustrates why a combination of diverse methods needs to be employed finally geologic lessons learned within the study area may be extrapolated to similar terrains elsewhere within the basin and range province end page 1008

summary of collapsible behaviour of artificially structured loess in oedometer and triaxial wetting tests this paper summarizes experimental studies on wetting induced collapsibility in loess using single oedometer double oedometer and triaxial wetting tests artificially structural loess samples with interparticle bonding calcite caco3 and a large void ratio were tested in the laboratory to avoid sampling disturbance of natural loess the comparison between the single and double oedometer tests confirms that the wetting induced deformation is independent of the sequence of wetting and loading the conventional triaxial apparatus was enhanced for investigating the collapse deformation in response to different water content increments when subjected to different stress levels the wetting induced strain subjected to high confining pressure develops in two steps it increases with increasing water content and reaches a relatively stable plateau and then increases rapidly again until a final stable state is reached the initial collapse surface was found by plotting the wetting induced strain vectors obser

littoral survey using the jers ops multispectral sensor example of the mont saint michel bay normandy france a jers 1 ops j p a anese earth renwte sensing satellite optical sensor image was used to make a method ological survey of the mont saint michel foreshore west of france the main objective was to test different procedures for processing m spectral data hetw een 520 nm and 2400 nm so as to re ne the information acquired from other sensor y such as spot xs and landsat tm w hich have a lower spectral and spatial discrimination potential the use of m spectral satellite data enables a rapid reconnaissance of the zone where both sedimen tological and morphological evolution occur according to the tides the ops sensor appears able to detect carbon ate responses channel 6 especially in suspension in the turbid plume of the estuary water jers ops distinguished clearly between clays vegetation and the eflect of phenomena likely to perturb their response mainly moisture characteri ed by channel 5

mixed siliciclastic and carbonate sediments a proposed first order textural and compositional classification sediments that are composed of mixtures of siliciclastic and carbonate material occur in both the modern and the ancient to date there is no commonly used classification of this type of sediment a descriptive first order classification system is proposed here that is applicable to most mixed sediments and their lithified equivalents the sediments are composed of four components 1 siliciclastic sand sand sized quartz feldspar etc 2 mud mixtures of silt and clay 3 allochems carbonate grains such as peloids ooids bioclasts and intraclasts 20 m in size and carbonate mud or micrite 20 m in size these components define a tetrahedra whose subdivision produces eight general classes of mixed sediment the name of a class reflects both the dominant grain type and the most abundant antithetic component for example a rock that contains greater than 50 siliciclastic material of which most is sand sized and subordinate allochems is termed an allochemic sandstone other rock names include micritic sandstone allochemic and micritic mudstone sandy or muddy allochem limestone and sandy or muddy micrite prefixes and adjectives can be added to these terms to include dolomitic sediments conglomeratic textures and biogenic constituents

geotechnical thresholds in the lanzhou loess of china abstract failure of cementation bonds leading to soil structure collapse and slope failure is a major problem encountered in loess slopes in the lanzhou region of china typical physical properties low plasticity indices short range bonds decrease in shear strength upon saturation show little variation throughout the loess strata however important variations in the modes of failure and collapse potential exist which are related to varying thresholds of cementation bond failure and packing transformations when geotechnical thresholds are exceeded metastable loess can rapidly transform from an open to close particle packing a phenomenon enhanced by leaching processes and degradation of cementation bonds geotechnical parameters from laboratory and in situ tests provide an insight into the variation of cementation bond condition which in turn provides enhanced understanding of processes underlying slope instability development and the triggering of catastrophic mass movements in loess

changes in tensile strength and microstructure of loess due to vibration abstract loess soils typically have an open and metastable structure humidification and vibration can modify their microstructure and thus influence their mechanical behavior in the present study to investigate the influence of train vibration on the tensile strength behavior of loess the tensile tests were performed on loess specimens that had been vibrated at a low amplitude for a long period using a modified horizontal extensograph in addition the microstructures of vibrated and non vibrated loess specimens before and after the tensile tests were characterized changes in the loess microstructure due to vibration and that in the tensile test were analyzed the results show that the relationship between uniaxial tensile strength and water content in soil specimen could be represented using a power function the axial displacement at failure varies at the same manner as tensile strength with respect to water content in comparison to intact loess occurrence of less clay bridges and clay buttresses between aggregates or coarse particles is identified in the disturbed specimens while aggregates are seen to be a very little more loose in vibrated specimens after the tensile tests than that before the tensile tests this indicates that vibration reduces the tension resistance and ductility of loess soil structure which could be attributed to loss of bonding strength as a result of breakage of clay cementations and disintegration of aggregates in the tensile test the soil structure goes through two distinct phases of change i e stretching phase and cracking phase in the stretching phase the tensile deformations take place throughout the specimen without altering the contacts between soil particles significantly in the cracking phase weak cementations fail to resist tensile deformation and suffer from breakage once a through crack is developed the specimen breaks in two leading to a catastrophic drop of tensile stress

alteration processes in volcanic soils and identification of exobiologically important weathering products on mars using remote sensing determining the mineralogy of the martian surface material provides information about the past and present environments on mars which are an integral aspect of whether or not mars was suitable for the origin of life mineral identification on mars will most likely be achieved through visible infrared remote sensing in combination with other analyses on landed missions therefore understanding the visible and infrared spectral properties of terrestrial samples formed via processes similar to those thought to have occurred on mars is essential to this effort and will facilitate site selection for future exobiology missions to mars visible to infrared reflectance spectra are presented here for the fine grained fractions of altered tephra lava from the haleakala summit basin on maui the tarawera volcanic complex on the northern island of new zealand and the greek santorini island group these samples exhibit a range of chemical and mineralogical compositions where the primary minerals typically include plagioclase pyroxene hematite and magnetite the kind and abundance of weathering products varied substantially for these three sites due in part to the climate and weathering environment the moist environments at santorini and tarawera are more consistent with postulated past environments on mars while the dry climate at the top of haleakala is more consistent with the current martian environment weathering of these tephra is evaluated by assessing changes in the leachable and immobile elements and through detection of phyllosilicates and iron oxide oxyhydroxide minerals identifying regions on mars where phyllosilicates and many kinds of iron oxides oxyhydroxides are present would imply the presence of water during alteration of the surface material tephra samples altered in the vicinity of cinder cones and steam vents contain higher abundances of phyllosilicates iron oxides and sulfates and may be interesting sites for exobiology

field measurements of induced and remanent moments of unexploded ordnance and shrapnel magnetometry is a widely used technique for clearance of areas contaminated with unexploded ordnance the discrimination of hazardous ordnance from nonhazardous items is possible using apparent remanence if ordnance is shock demagnetized on impact with the ground we developed a mobile device the magnetic remanence interrogation platform mrip for measuring the induced and remanent moments of steel samples the mrip comprises six three component fluxgate magnetometers symmetrically distributed around a rotating sample holder samples are placed on the holder and are slowly spun through two complete rotations the measurement is repeated after the sample is physically rotated by 90deg so that the previous up direction points east the mrip platform was deployed to two field sites at the first site 76 and 90 mm projectiles were measured most had relatively low remanent magnetization relative to the induced suggesting that shock demagnetization occurs variations in the remanent moments of different specimens of 90 mm projectiles were attributed to variations in the type of steel used there was a strong correlation of the direction of remanent and inducing field during burial indicating evidence of shock magnetization and or magnetic viscosity at the second site intact and partial 4 2 in mortars as well as shrapnel base plates and cultural debris were measured most of the base plates and intact mortars had low remanent magnetization whereas the shrapnel and partial mortars tended to have higher remanent magnetization the results indicate that there is an inherent risk in using apparent remanence for discrimination as not all ordnance is demagnetized on impact

magnetic models of unexploded ordnance magnetometry is widely used for the characterization of areas contaminated by unexploded ordnance uxo to successfully discriminate hazardous uxo from nonhazardous clutter requires accurate models of the ordnance response this paper develops an ordnance library with 15 different items using total field magnetic data collected over a test stand the induced and remanent magnetizations were obtained by varying the three dimensional orientation of each item and measuring the magnetic field on a horizontal plane in the dipolar regime replicate measurements using multiple specimens of the same ordnance returned very similar induced magnetizations the fitted moments were used to estimate the detection depths for different sensor noise floors a prolate spheroid with a 3 5 aspect ratio was used to provide a good approximation to the detection depths for many of the ordnance items assuming a 1 nt noise floor these orientation dependent detection depths ranged from 10 to 17 times of the object s diameter

study on shear strength characteristics of loess dam materials under saturated conditions a loess accumulation dam in ansai area yan an shaanxi province is selected as the research object and the remolded soil of the dam body is taken as the test material to conduct the saturated loess indoor triaxial test the test shows that the peak stress of saturated remolded loess increases with the enhancement of confining pressure and dry density and the pore water pressure rises rapidly in the shear of the samples with a dry density of 1 4 1 6 g cm3and gradually flattens out when the samples with a dry density of 1 7 g cm3 in the process of shearing the pore pressure rises rapidly and then decreases as the volume increases the total internal friction angle and effective internal friction angle increase with the augment of dry density and the total cohesion and effective cohesion show a changing trend of first rising then falling and then rising due to the different development of original cohesion sliding friction and rolling friction meanwhile combined with field monitoring it can be determined that the dam a total of three times more obvious damage according to the comparison of field test and laboratory test the concept and calculation method of inspection threshold are put forward

on the behaviour of deep ocean sediments the behaviour of deep ocean sediments from the north atlantic abyssal plains is examined within the context of a recognised framework the sensitivity framework which was developed by cotecchia chandler for structured terrestrial clays the deep ocean sediments have very high sensitivities of the order of those of quick clays but in volumetric compression their destructuration occurs at more moderate rates similar to those usually found in terrestrial clays of medium sensitivities the deep sea sediments were retrieved using different types of sampler which influenced greatly the strength and stiffness of the different samples in particular in the lower quality samples the greater disturbance caused by sampling is responsible for changing their behaviour from brittle to ductile during shearing after compression to stresses post gross yield giving them an apparent insensitivity to shear strains results from numerical analyses using a constitutive model that was developed for structured terrestri

moisture content effect on the creep behavior of loess for the catastrophic baqiao landslide abstract understanding the creeping behavior of loess is of great importance as large scale loess landslides are closely related with creep behavior at present it is still challenging to predict and estimate the long term stability of such landslides this is in a large degree due to the poor understanding of moisture control on creep behavior of loess the purpose of this study is to decipher the loess creep behavior under various moisture contents mcs using loess specimens obtained from baqiao landslide xi an of china using multi loading triaxial creep tests under different mcs of 9 12 15 18 and 21 based on the laboratory test results a series of relationships between the creep rate at the steady state creep stage and the initial strain and initial shear modulus are revealed meanwhile a method for obtaining the long term strength of loess specimens namely the steady state creep rate slope method scrsm is proposed scrsm resolves the issue in several conventional methods such as the isochronous stress strain curve method the tangent method of steady creep rate when mcs are of concern such an improvement is primarily due to a better way of finding the inflection point of the steady state rate it is found that scrsm is robust and accurate to determine the long term strength of loess specimens furthermore we propose a modified burgers model with a newly introduced nonlinear parameter n to overcome deficiencies of conventional creep models this modified burgers model is flexible to fit the creep test curves of loess and can describe the curves at the accelerated creep stage more accurately lastly the main factors triggering the baqiao landslide is analyzed considering stratum lithology rainfall and excavation in general this study provides a basis for understanding the evolutional process of loess landslides as well as guidelines for prevention controlling and prediction of loess landslides

analysis of retrogressive loess flowslides in heifangtai china abstract the heifangtai terrace is located in the arid loess area in northwestern china where a large number of landslides was induced by agricultural irrigation on the terrace resulted in slope retreat at the terrace edge at an estimated rate of 0 024 km 2 yr 1 on the basis of field investigation and monitoring remote sensing and aerial images and laboratory tests we analyzed the characteristics of slope retreat and the failure mechanism of the loess flowslides the retreat of slope is caused by the retrogressive behavior of the loess flowslide of which new failure develops at the backwall of the preceding one the groundwater level variation governs the failure process and mechanism of the flowslides the observed loess flowslides were accompanied by rapid slope deformation high velocity and long runout distance exhibiting liquefaction and fluidization during the movement in the event of a loess flowslide a small scale drained slope failure produces a concave recession first intensifies localized groundwater flow on the slope surface while the flow is being impeded by the deposit which produces an undrained condition with increasing localized pore water pressure and in turn facilitates the subsequent flowslide results of the isotropically consolidated undrained triaxial tests icu and constant shear stress drained triaxial tests csd revealed the strain softening behavior in the saturated reconstituted loess and they showed that the excess pore water pressure is associated with a small axial displacement and possibly facilitated by some alternations in the loess structure at the micro scale

emissivity of terrestrial materials in the 3 5 μm atmospheric window remotely sensed infrared radiance emitted by a surface is a function both of its kinetic temperature and its spectral emissivity consequently assumptions are usually made about the emissivity of earth surface materials to allow their temperatures to be determined or vice versa to increase the accuracy of these assumptions the directional hemispherical spectral reflectance of a wide range of natural earth surface materials has been measured and is summarized here these include igneous metamorphic and sedimentary rocks desert varnish soils vegetation water and ice kirchhoff s law can be used to predict directional spectral emissivity from these data

on the mechanics of structured sands to date the effect of structure on the behaviour of natural sands has focused almost exclusively on the component of bonding and the effect of fabric has been largely overlooked the paper describes a detailed investigation of the behaviour of two natural sands by means of triaxial testing over a wide range of pressures one material had bonding as the principal element of its structure and the other fabric following on from a paper of cuccovillo and coop which examined the influence of the two structural elements on the small strain stiffness the current paper develops a new framework for the yielding and large strain behaviour it is suggested that structure should be considered as an element of the nature of a sand in addition to properties such as mineralogy particle shape and grading the resulting framework is then capable of encompassing the patterns of behaviour seen for both bonding and fabric dominated sands while bonding results in a cohesive mode of shearing it is demonstrated that when

the mechanics of a saturated silty loess and implications for landslides the results from an intensive experimental investigation on a loess that was retrieved from a typical silty loess zone in the north western chinese loess plateau are presented and interpreted triaxial and oedometer tests were performed on intact and reconstituted samples in a saturated condition the soil behavior was found to be strongly affected by structure the compression paths of the intact samples crossed the intrinsic compression line of the reconstituted soil and reached well defined gross yield points after which the compression paths converged towards the intrinsic compression lines two critical state lines were defined for the intact and reconstituted soils in the volumetric plane as a result of a robust element of natural structure comparisons were made with a structured clayey loess retrieved from the south eastern loess plateau it was found that the effects of structure on the behavior of the two loess soils are similar though they are very different in natural properties this indicates that their natural structures might have experienced similar forming processes perhaps related to their common origin catastrophic flowslides commonly occur in the study area and the patterns of behavior observed in the laboratory tests may create some new insights into mechanisms of landslide initiation and subsequent movement as discussed in the study

separation of vegetation and rock signatures in thematic mapper and polarimetric sar images abstract a technique for separating classes of surface roughness and vegetation in semiarid regions using polarimetric synthetic aperture radar sar and thematic mapper tm data has been developed we conclude that polarimetric sar data may be used to separate areas with vegetation cover where one suite of model inversions may be applicable for derivation of surface roughness in more vegetated regions visible near infrared nir data will provide a mechanism for determining the relative contribution of vegetation to multiple scattering in the sar data thus the synergistic use of the two data sets provides a more complete characterization of surface units and cover this result while important for geologic interpretations is even more critical when trying to monitor dielectric constant variations related to changes in moisture content of soil and vegetation cover in arid to semiarid regions a strategy for automating a procedure for measurement of surface roughness is proposed

ore detection and grade estimation in the sudbury mines using thermal infrared reflectance spectroscopy this pilot study investigated the usefulness of thermal infrared reflectance tir spectroscopy to estimate ore grade in an underground environment and to separate ore bearing samples from their host rocks work was carried out under laboratory conditions to test the initial concept all samples had naturally broken faces to mimic the situation in a freshly blasted underground opening a total of 26 samples including massive and disseminated ores were collected from eight mines around the sudbury basin in ontario rock surfaces were measured wet and dry to address environmental conditions encountered underground to separate barren rocks from ores and for ore grade estimation an important finding of this research is that in the region of 1319cm 1 most known silicate minerals converge to a common reflectance minima 1 5 but massive and disseminated sulfides have distinctly higher reflectance individual sulfide minerals chalcopyrite pyrrhotite pentlandite however do not reveal diagnostic fea

development and evolution of loess vertical joints on the chinese loess plateau at different spatiotemporal scales abstract the vertical joints of aeolian loess are ubiquitous on the chinese loess plateau clp the distribution variability of which mainly depends on the differences in structural characteristics of loess water drivers e g rainfall or irrigation loess strata e g sedimentary depth and microtopography this study conducted extensive field investigation and experiments to enhance the understanding of morphologies cross scale transformation mechanism and structural bases of loess vertical joints lvjs moreover the development and evolution processes of lvjs were refined by considering loess sedimentary dynamics results show that 1 lvjs are the product of diagenesis in loess strata during loess historical sedimentary process 2 the pore concentration zones and vertical tubular channels in loess are the structural bases of forming original vertical joints ovjs at the micro mesoscale which is supported by the results from the three dimensional computing tomography ct scanning and scanning electron microscopy sem tests and 3 the morphologies of lvjs vary with the microtopography at different spatiotemporal scales and is characterized by the cross scale transformation mechanism i e that they could transform up i e an expansion behavior or down i e a degradation behavior at the micro meso and sub macro scales under the influences of dry wet cycles loess pile thickening and exogenic forces besides we also propose the development and evolution mechanism of ovjs in loess from the viewpoint of unsaturated loess which would help understand the loess anisotropic genesis structural evolution preferential flow and the occurrence of geohazards such as landslides and soil erosion

laboratory study on soil behavior in loess slope subjected to infiltration abstract in recent years heifangtai plateau in gansu province china has received significant attention as a loess region in which landslides frequently occur this study aims to examine the soil behavior and failure mechanism s of loess slopes subjected to water infiltration high quality samples were retrieved behind the failure plane of a landslide in heifangtai three sets of stress path tests were conducted to mimic the process of loess slope failures these tests include undrained compression on anisotropically consolidated saturated samples drained shear by decreasing mean effective stress at constant axial load on saturated samples and wetting by decreasing matric suction at constant axial load on unsaturated samples loess behavior was evaluated in terms of shear strength deformation upon shearing critical state state parameter and soil water characteristic curve three major observations were drawn from the test results first the anisotropically consolidated saturated loess exhibits a noticeable strain softening behavior upon undrained compression the peak shear strength is mobilized at less than 1 axial strain the ultimate shear strength is only 20 30 of the peak value second when subjected to shear by decreasing mean effective stress at constant axial load the saturated loess exhibits sudden failure when the confining stress is low at higher stresses the soil exhibits progressive failure third unsaturated loess deforms progressively when subjected to a reduction in matric suction i e wetting at constant axial load the failure mechanisms of the loess slopes are discussed based on the experimental findings

the structure degradation of a silty loess induced by long term water seepage abstract loess is a typical silt sized aeolian soil that is widely deposited and possesses a fragile soil structure susceptible to collapse upon wetting the instability of shallow loess slopes is well documented but deeper failures triggered by rainfall and irrigation can also occur in the case of long term seepage clay particles and salts have been observed to leach out of the loess slopes this paper presents a systematic laboratory study of the effects of water conditions on the mechanical behaviour of silty loess with isotropic compression and bender element tests carried out on natural and reconstituted loess recovered at 10 m depth from a site in china the results show that saturation causes reduction in both the compression yield stress and small strain stiffness of the soil and that after being exposed to seepage they decrease further the possible mechanism of structure degradation is investigated by means of microscopic and chemical analyses and it is found that seepage will cause the pore ions concentration to reduce with a loss of clay mineral bonding strength resulting in the detachment of silt particles from aggregates this work highlights the importance of monitoring the water outflow in the field at the loess slope edge since it may causes large deformation in the long term

rock type identification in a simulated underground environment using second derivative thermal infrared reflectance spectra this study investigates the usefulness of thermal infrared reflectance spectroscopy tir to map rock faces in an underground environment a laboratory fourier transform infrared ftir spectrometer was used to measure reflectance spectra 500 5000 cm 1 of freshly broken rock surfaces a total of 37 samples covering 10 different rock types including barren silicate rocks and rocks with disseminated sulfides was collected from eight mines around the sudbury basin in ontario freshly broken rock surfaces were measured wet and dry to address environmentalconditionsencounteredunder ground spectral data were processed by the second derivative approach and the spectral angle mapper algorithm sam for rock type identification an average of 77 accuracy was achieved for all rock types the success of this effort implies that hyperspectral analysis using second derivative spectra is effective to remove the effect of liquid water local geometry and disseminated sulfides while preserving diagnostic rock spectral signatures between 700 and 1300 cm 1

measuring glacier surface temperatures with ground based thermal infrared imaging spatially distributed surface temperature is an important yet difficult to observe variable for physical glacier melt models we utilize ground based thermal infrared imagery to obtain spatially distributed surface temperature data for alpine glaciers the infrared images are used to investigate thermal microscale processes at the glacier surface such as the effect of surface cover type and the temperature gradient at the glacier margins on the glacier s temperature dynamics infrared images were collected at cuchillacocha glacier cordillera blanca peru on 23 25 june 2014 the infrared images were corrected based on ground truth points and local meteorological data for the control points the pearson s correlation coefficient between infrared and station temperatures was 0 95 the ground based infrared camera has the potential for greatly improving glacier energy budget studies and our research shows that it is critical to properly correct the thermal images to produce robust quantifiable data

thermal infrared remote sensing and kirchhoff s law 1 laboratory measurements by the end of this century the earth observing system eos will provide worldwide thermal infrared multispectral images of the earth presenting geologists with a new kind of remote sensing data for interpretation thus it has become essential to understand the spectral emittance behavior of terrestrial surface materials perhaps the most fundamental question to be answereed is the extent to which such materials follow kirchhoff s law epsilon 1 r under laboratory and field conditions especially when a sample displays a thermal gradient we present the first rigorous quantitative comparison of directional and hemispherical reflectance and directional emittance of rock and soil samples in the laboratory with thermal gradients induced by heating them from below and allowing them to radiate to a colder background the results show that only an extemeley low density sample composed of fine particles sifted into a fairy castle structure displays a thermal gradient steep enough within the infrared skin depth to cause significant 6 departure from kirchhoff s law there is no detectable effect on the more normal terrestrial samples such as soils and rocks measured in the laboratory even when semitransparent coatings are involved thus both emittance and reflectance measurements can be used to calculate sample emissivity for most terrestrial surface materieals however the effect on kirchhoffian behavior of different field environments which may induce a steeper thermal gradient in particulate samples has yet to be determined and some low density surface materials like newly fallen snow frost and efflorescent salts on playas have yet to be measured in emittance

emission spectroscopy of clay minerals and evidence for poorly crystalline aluminosilicates on mars from thermal emission spectrometer data 1 to understand the aqueous history of mars it is critical to constrain the alteration mineralogy of the martian surface previously published analyses of thermal infrared 6 25 m remote sensing data of mars suggest that dark regions have 15 20 clay minerals however near infrared 1 3 m spectral results generally do not identify widespread clay minerals thermal infrared detections of clays on mars are difficult to interpret owing in part to the relative paucity of published spectral analyses of clay minerals and clay bearing materials using similar spectra thermal infrared emission spectra in this study we present an analysis of the thermal emission spectral features 6 25 m or 400 1650 cm 1 of a suite of clay mineral reference materials and clay bearing rocks linking their spectral features to the crystal chemical properties of the clays on the basis of this context provided by the emission spectral analysis of clay minerals and clay bearing rocks we reconsider the evidence for clay minerals on mars from thermal emission spectrometer tes results we propose that global scale clay abundances determined from tes probably represent a geologically significant surface component though they may actually correspond to poorly crystalline aluminosilicates with similar si o ratios to clay minerals 0 3 0 4 rather than well crystalline clays if clay minerals or clay like materials on mars are poorly crystalline and or dessicated they may be detectable in the thermal infrared but not easily detected with near infrared data sets

discrimination and classification of buried unexploded ordnance using magnetometry magnetic surveys are quite successful at locating buried steel objects including unexploded ordnance uxo however many of the anomalies apparent in a magnetic image of a contaminated area are from metallic debris shrapnel and geological variations in ferromagnetic concentration observations are usually made in the far field of the object so that in most cases we can only recover the dipole moment of a buried item due to self demagnetization effects the magnitude and direction of induced magnetism varies significantly with ordnance orientation this results in an infinite number of ordnance like objects that can reproduce a given dipole moment to discriminate we define a library of ordnance items expected to occur in the area and find how closely each recovered moment matches one of the uxos in this library we define the size of this mismatch as the remanent magnetization and produce a prioritized dig list on the assumption that items with lower remanence are more likely to be uxo such a ranking scheme proves to be very effective when implemented at two sites in montana the analysis reveals that live site and emplaced uxo have significantly different remanence and implies that previous tests of magnetic discrimination performance on seeded sites have been overly pessimistic

uxo detection by multiscale potential field methods the choice of an effective interpretative methodology in terms of management costs timing reliability safety and efficiency is a key issue for the identification of unexploded ordnance uxo among geophysical methods magnetometry plays an important role in detection and interpretation of uxo objects we present a study aimed at the identification and characterization of buried uxo in rohoznik slovakia by a multiscale analysis on high resolution magnetic data the area is located close to a former army shooting range and is characterized by several buried uxo when a uxo hits the ground but does not explode the impact causes a re organization of the magnetic domains within the armature shock demagnetization due to shock demagnetization the object gets a magnetization oriented in the direction of the actual earth magnetic field furthermore the elongated shape of the uxo of rohoznik causes their anomalies to be oriented along the longitudinal axis of the projectiles our multiscale analysis was performed through methods such as depth from extreme points dexp and the multi ridge method the upward continuation employed by these two methods allowed reducing the influence of the high frequency noise related to non uxo buried iron objects also the use of high order derivatives in the multiscale approach decreased interference effects related to close by sources and avoided any pre filtering our approach was first validated on a test site located close to rohoznik where unexplored projectiles were buried with different orientations at a known depth then we focused on the real data of the former army shooting range for all our analyses we employed a structural index value of 2 5 which was estimated through the scaling function analysis and the derivative euler deconvolution algorithm both the dexp and multi ridge depth estimation methods proved to be effective and rapid with respect to more expensive and time consuming methods such as inversion our analysis revealed average depths for the analysed uxos matching rather well with what was found by subsequent excavations with a maximum discrepancy of a few decimetres

reflectance spectroscopy in the visible and near infrared 0 35 2 55 µm applications in carbonate petrology reflectance spectroscopy in the visible and near infrared 0 35 to 2 55 m offers a rapid inexpensive nondestructive tool for determining the mineralogy and for investigating the minor element chemistry of the hard to discriminate carbonate minerals and can in one step provide information previously obtainable only by the combined application of two or more analytical techniques when light interacts with a mineral certain wavelengths are preferentially absorbed the positions and widths of absorptions due to vibrations of the carbonate radical and the positions and shapes of absorptions due to transition metal cations if present can be used to determine mineralogy relative intensities of absorptions due to transition metal cations can be used to determine concentration of these cations because absorptions due to fe2 and mn2 occur in different regions of the spectrum the presence of one cation does not interfere with analysis for the other detection limits for mn2 are about 0 1 wt mn and for fe2 are about 0 01 wt fe this technique is also very sensitive to the presence of water and indicates that aqueous fluid inclusions are nearly ubiquitous in carbonate minerals and rocks spectra indicate that inclusions are particularly abundant in skeletal carbonates and that the quantity of inclusions in skeletal material varies from one type of organism to another spectra indicate that inclusions are lost during diagenesis of skeletal material providing a new criterion for diagenetic studies

precise emissivity of rock samples to differentiate among geological materials and vegetation using thermal infrared spectra radiometric measurements require corrections for local temperature variations and reflected radiation a laboratory technique is described for the determination of spectral emissivity signatures for natural geological samples using a fourier transform infrared spectrometer and the self emission of the scene the approach described does not require control of the sample temperature a quantitative assessment of uncertainties is presented comparison of the emissivity measurements from natural geological specimens with hemispherical reflectance data gave an average difference of about 0 01 in emissivity except near strong features of the spectra the technique is applicable to field measurements of high emissivity objects

spectral reflectance characterization 0 4 to 2 5 and 8 0 to 12 0 mu m of phanerozoic strata wind river basin and southern bighorn basin areas wyoming abstract reflectance spectroscopy a useful analytical tool available to geologists for over 100 years has not been widely used in petrologic or stratigraphic studies of sedimentary rocks we are routinely using laboratory spectral reflectance data covering the 0 4 to 12 0 m wavelength interval in an investigation of the stratigraphic and structural evolution of the wind river and bighorn basin areas wyoming two types of laboratory spectral reflectance measurements were made on 192 weathered outcrop bedrock and core samples 1 hemispherical reflectance from 0 4 to 2 5 m 229 spectra and 2 biconical reflectance from 8 0 to 12 0 m 84 spectra results show stratigraphic variations in the spectral properties of sedimentary rocks as encountered in the field sample mineralogy was determined using x ray diffraction and interpretation of spectra the mineralogy lithology and stratigraphic distribution of samples are diverse and representative of phanerozoic siliciclastic and carbonate strata encountered in foreland sedimentary basins spectra were sorted into 36 distinct groups according to the presence or absence of 68 visible and infrared reflectance features many spectral features can be assigned to specific molecular phenomena and allow rapid determination of specific minerals minerals detectable spectrally include gypsum kaolinite smectite analcime goethite jarosite calcite dolomite and feldspar results are contributing to our understanding of the depositional history of the wind river and bighorn basin areas more importantly results suggest that laboratory field and remote reflectance spectroscopy have more general geologic applicability in studies of sedimentary rocks reflectance spectroscopy can augment conventional laboratory and field methods for petrologic analysis correlation interpretation of depositional environments and construction of facies models

determination of martian meteorite lithologies and mineralogies using vibrational spectroscopy we have acquired thermal infrared emission spectra of four martian meteorite samples alh77005 nakhla zagami and eet79001 representing three major lithologies iherzolite clinopyroxenite and basalt the spectra of these meteorites are significantly different from each other and we can distinguish the three lithologies easily on the basis of their spectral morphologies using a linear deconvolution model the modal mineralogies of alh77005 nakhla and zagami were derived from their spectra to within 2 19 of the modes derived by optical methods for zagami and eet79001 the correct mineral types were identified as present using the linear method although an exact spectral match using available end member spectra was not obtained probably due to the lack of a pigeonite end member spectrum or shock effects in the meteorites the meteorite spectra we have acquired will be used for comparison with data to be returned by the thermal emission spectrometer tes on the mars global surveyor orbiter and would also be useful for comparing to future rover or lander based thermal ir spectra based on our results comparisons of mineral end member and meteorite spectra with tes spectra of coarse regolith and rocky regions should aid identification and mapping of martian surface lithologies and unit mineralogy

rootless cones on mars a consequence of lava ground ice interaction fields of small cratered cones on mars are interpreted to have formed by rootless eruptions due to explosive interaction of lava with ground ice contained within the regolith beneath the flow melting and vaporization of the ice and subsequent explosive expansion of the vapour act to excavate the lava and construct a rootless cone around the explosion site similar features are found in iceland where flowing lava encountered water saturated substrates the martian cones have basal diameters of c 30 1000 m and are located predominantly in the northern volcanic plains high resolution mars orbiter camera images offer significant improvements over viking data for interpretation of cone origins a new model of the dynamics of cone formation indicates that very modest amounts of water ice are required to initiate and sustain the explosive interactions that produced the observed features this is consistent with the likely low availability of water ice in the martian regolith the scarcity of impact craters on many of the host lava flows indicates very young ages suggesting that ground ice was present as recently as less than 10 l00 ma and may persist today rootless cones therefore act as a spatial and temporal probe of the distribution of ground ice on mars which is of key significance in understanding the evolution of the martian climate the location of water in liquid or solid form is of great importance to future robotic and human exploration strategies and to the search for extraterrestrial life

resurfacing history of the northern plains of mars based on geologic mapping of mars global surveyor data 1 geologic mapping of the northern plains of mars based on mars orbiter laser altimeter topography and viking and mars orbiter camera images reveals new insights into geologic processes and events in this region during the hesperian and amazonian periods we propose four successive stages of lowland resurfacing likely related to the activity of near surface volatiles commencing at the highland lowland boundary hlb and progressing to lower topographic levels as follows highest elevations indicated stage 1 upper boundary plains early hesperian 2 0 to 2 9 km stage 2 lower boundary plains and outflow channel dissection late hesperian 2 7 to 4 0 km stage 3 vastitas borealis formation vbf surface late hesperian to early amazonian 3 1 to 4 1 km and stage 4 local chaos zones early amazonian 3 8 to 5 0 km at acidalia mensa stage 2 and 3 levels may be lower 4 4 and 4 8 km respectively contractional ridges form the dominant structure in the plains and developed from near the end of the early hesperian to the early amazonian geomorphic evidence for a northern plains filling ocean during stage 2 is absent because one did not form or its evidence was destroyed by stage 3 resurfacing remnants of possible amazonian dust mantles occur on top of the vbf the north polar layered deposits appear to be made up of an up to kilometer thick lower sequence of sandy layers early to middle amazonian in age overlain by late amazonian ice rich dust layers both units appear to have outliers suggesting that they once were more extensive

evidence for recent climate change on mars from the identification of youthful near surface ground ice ground ice in the crust and soil may be one of the largest reservoirs of water on mars1 2 3 near surface ground ice is predicted to be stable at latitudes higher than 40 ref 4 where a number of geomorphologic features indicative of viscous creep and hence ground ice have been observed5 mid latitude soils have also been implicated as a water ice reservoir6 the capacity of which is predicted to vary on a 100 000 year timescale owing to orbitally driven variations in climate7 it is uncertain however whether near surface ground ice currently exists at these latitudes and how it is changing with time here we report observational evidence for a mid latitude reservoir of near surface water ice occupying the pore space of soils the thickness of the ice occupied soil reservoir 1 10 m and its distribution in the 30 to 60 latitude bands indicate a reservoir of 1 5 6 0 104 km3 equivalent to a global layer of water 10 40 cm thick we infer that the reservoir was created during the last phase of high orbital obliquity less than 100 000 years ago and is now being diminished

analysis of terrestrial and martian volcanic compositions using thermal emission spectroscopy 1 determination of mineralogy chemistry and classification strategies we have examined and applied existing classification schemes for volcanic rocks and developed new schemes using thermal emission spectra of terrestrial volcanic rocks laboratory thermal infrared spectra 5 25 m at 2 cm 1 spectral sampling deconvolved modal mineralogies and derived mineral and bulk rock chemistries were used to distinguish basalt basaltic andesite andesite and dacite modal mineralogies derived from linear deconvolution of terrestrial volcanic rocks were compared to modes measured by an electron microprobe phase mapping technique to determine the accuracy of linear deconvolution in modeling specific mineral abundances one standard deviations of the absolute differences between modeled and measured mineral abundances range from 2 4 to 12 2 vol with an average standard deviation of 4 8 vol being in agreement with average uncertainties calculated in previous studies weighted average compositions of feldspars in the deconvolution generally overlap the measured ranges of plagioclase compositions and the presence of low calcium and high calcium pyroxenes was correctly identified bulk chemistries of volcanic rocks were derived with a relatively high degree of accuracy 1 standard deviations ranging from 0 4 to 2 6 vol by combining the compositions of spectrally modeled phases in proportion to their relative abundances in a particular sample these data were collectively used to examine existing and develop new volcanic rock classification schemes however no single classification scheme was effective in accurately classifying all samples multiple steps of classification were required to distinguish volcanic rocks reflecting the mineralogic diversity and continuum of compositions that exists in volcanic rock types in a companion paper hamilton et al this issue these schemes are applied to the classification of martian surface compositions

experimental study on the shear behavior of loess and paleosol based on ring shear tests abstract landslide hazards frequently occur in the chinese loess plateau every year causing devastating casualties damage to engineering structures and reduction in land resources this work presents an experimental investigation of four samples retrieved from jingyang in the southeast of the chinese loess plateau using ring shear tests and microscopic observation in an attempt to explore the shear behavior of loess and paleosol under the larger deformations that are involved in landslide hazards the results of ring shear tests reveal that the loess and paleosol samples exhibited different strength characteristics the residual strength envelopes could be assumed to be a straight line and the overconsolidated state had negligible influence on the residual shear strength after the shear experiment shear bands were studied from both macroscopic and microscopic perspectives macroscopic observation and mechanical analysis indicate that all samples developed a main horizontal failure plane related to the maximum shear stress while loess samples also developed en echelon failure planes tilting from the horizontal at angles of 14 18 which are interpreted as coulomb slip planes scanning electron microscopy reveals that the particles inside shear bands tend to be re oriented particle crushing occurred in the shear process which was also verified by particle size distribution analysis