relief inversion in the geomorphological evolution of sub saharan west africa abstract the geomorphology of much of sub saharan west africa is dominated by the presence of plateaux and plains with ferruginous and locally aluminous bauxitic duricrusts the plateaux occur at different elevations and have been correlated as two or more palaeosurfaces across much of the region the duricrusts have generally been considered to be residual formed by conformable erosion and chemical wasting of immediately underlying bedrock this concept has been central to interpretations as diverse as the formation and evolution of the landscape and the development of geochemical exploration models recent regolith landform mapping field observations and experience from mineral exploration in southern mali and burkina faso however demonstrate that the duricrusts are mainly ferricretes i e fe oxide cemented sediments these observations require a re interpretation of the geomorphological evolution of the region during the cenozoic the landscape has evolved by several cycles of weathering and erosion deposition triggered by climatic tectonic or other environmental changes it is proposed that an initial bauxitic lateritic regolith was partly eroded following uplift and or a change to a more arid climate and that the detritus rather than being removed was deposited on slopes and valleys during a subsequent humid period of lateritic weathering fe oxide cementation of this detritus formed ferricrete dehydration and hardening of the ferricrete after further uplift or aridity increased its resistance to erosion resulting in relief inversion with the detritus in turn being deposited downslope this too has been weathered and cemented to form a younger ferricrete the occurrence of ferricrete landforms in adjacent countries noted by field observation and inferred from satellite imagery demonstrates that relief inversion is a very widespread and important phenomenon in southern mali burkina faso and adjacent countries in semi arid west africa

a geophysically constrained litho structural analysis of the eburnean greenstone belts and associated granitoid domains burkina faso west africa abstract interpretation of airborne geophysical data integrated with field structural and lithological observation was successfully employed in the creation of the litho structural framework in a poorly exposed paleoproterozoic granite greenstone terrain of the west african craton the geophysical data portray with sufficient detail all of the lithological units and structural features present the results suggest that the granitoid domains are formed by numerous small to medium sized plutons the existence of several generations of magmatic episodes has a significant impact on the development of a regional tectonic model the magnetic data provided a better definition of the actual pluton shapes and several highly magnetic late orogenic plutons were reliably identified relic f1 fold hinges were recognized in the hounde and boromo greenstone belts the d1 penetrative structures are generally affected by the d2 transcurrent shear zones which often form as well the granite greenstone belt boundaries previously unreported s2 shear zones including the bossie shear zone transecting the sideradougou granitoid domain and abundant small scale shear zones affecting all of the lithologies represent prospective areas for gold exploration airborne gamma ray spectrometry data aided in the mapping process in areas with less regolith cover including erosional ridges and parts of the banfora greenstone belt the magnetic data revealed at least three generations of doleritic dykes crosscutting the western burkina faso

partitioning of seismoacoustic energy and estimation of yield and height of burst depth of burial for near surface explosions explosions near the earth s surface excite both seismic ground motions and atmospheric overpressure the energy transferred to the ground and atmosphere from a near surface explosion depends on yield w as well as the height of burst depth of burial hob dob for above belowground emplacements we report analyses of seismic and overpressure motions from the humble redwood series of low yield near surface chemical explosions with the aim of developing quantitative models of energy partitioning and a methodology to estimate w and hob dob the effects of yield hob and range on amplitudes can be cast into separable functions of range and hob scaled by yield we find that displacement of the initial p wave and the integral of the positive overpressure impulse are diagnostic of w and hob with minimal scatter an empirical model describing the dependence of seismic and air blast measurements on w hob dob and range is determined and model parameters are found by regression we find seismic amplitudes for explosions of a given yield emplaced at or above the surface are reduced by a factor of 3 relative to fully contained explosions below ground air blast overpressure is reduced more dramatically with impulse reduced by a factor of 100 for deeply buried explosions relative to surface blasts our signal models are used to invert seismic and overpressure measurements for w and hob and we find good agreement w errors 30 hob within meters with ground truth values for four noncircular validation tests although there is a trade off between w and hob for a single seismic or overpressure measurement the use of both measurement types allows us to largely break this trade off and better constrain w and hob however both models lack resolution of hob for aboveground explosions

identifying sediment sources in a gullied catchment using natural and anthropogenic radioactivity the ratio of the lithogenic nuclides 226ra and 232th indicates that the major source of sediment in transport in a gullied catchment located in the head waters of whiteheads creek new south wales australia is the gully itself this observation is supported by 7be and 137cs concentrations which indicate that the sediment is derived from erosion of either gully floor or gully wall material while subcatchment 7be and 137cs data show sheet rill and gully erosion are occurring in the upstream catchments sediment from these sources is either being trapped before entering the gully or the volume of sediment is small compared to that derived from the gully itself the differences in the 226ra to 232th ratio between the suspended solids collected on the rising stage and samples of sediment deposited during the falling stage at the outlet of the catchment indicate a change in the source of sediment during storm events the results presented here demonstrate the applicability of radionuclide tracers in providing quantitative estimates of the relative contributions of individual catchments to the sediment moving within a drainage network and in determining whether or not the sediments are mainly derived from subsoil or topsoil sources

classification and snow line detection for glacial areas using the polarimetric sar image abstract snow cover and glaciers are sensitive indicators of the environment the vast spatial coverage of remote sensing data coupled with the tough conditions in areas of interest has made remote sensing a particularly useful tool in the field of glaciology compared to optical images synthetic aperture radar sar data are hardly influenced by clouds this is important because glacial areas are usually under cloud cover the dongkemadi glacier in the qinghai tibetan plateau was selected as the study area for this paper we use polarimetric sar polsar image for classification on and around the glacier the contrast between ice and wet snow is remarkable but it is difficult to distinguish the ice from the ground on sar images due to similar backscatter characteristics in former research in our study we found that this distinction can be achieved by target decomposition support vector machines svms are performed to classify the glacier areas using the selected features the glacial areas are classified into six parts wet snow ice river outwash soil land rocky land and others the polsar target decomposition svms pts method is proven to be efficient with an overall classification accuracy of 91 1 and a kappa coefficient of 0 875 moreover 86 63 of the bare ice and 96 76 of the wet snow are correctly classified the classification map acquired using the pts method also helps to determine the snow line which is an important concept in glaciology

a weathering intensity index for the australian continent using airborne gamma ray spectrometry and digital terrain analysis abstract weathering intensity largely controls the degree to which primary minerals are altered to secondary components including clay minerals and oxides as weathering intensity increases there are changes in the hydrological geochemical and geophysical characteristics of the regolith thus once calibrated weathering intensity can be used to predict a range of regolith properties a weathering intensity index wii over the australian continent has been developed at a 100 m resolution using regression models based on airborne gamma ray spectrometry imagery and the shuttle radar topography mission srtm elevation data airborne gamma ray spectrometry measures the concentration of three radioelements potassium k thorium th and uranium u at the earth s surface the total gamma ray flux dose is also calculated based on the weighted additions of the three radioelements regolith accounts for over 85 of the australian land area and has a major influence in determining the composition of surface materials and in controlling hydrological and geomorphological processes the weathering intensity prediction is based on the integration of two regression models the first uses relief over landscapes with low gamma ray emissions and the second incorporates radioelement distributions and relief the application of a stepwise forward multiple regression for the second model generated a weathering intensity index equation of wii 6 751 0 851 k 1 319 relief 2 682 th k 2 590 dose the wii has been developed for erosional landscapes but also has the potential to inform on deposition processes and materials the wii correlates well with site based geochemical indices and existing regolith mapping interpretation of the wii from regional to local scales and its application in providing more reliable and spatially explicit information on regolith properties are described

contents of natural radioactive nuclides in soil in relation to their surface area concentrations of uranium series nuclides 238u 226ra 210pb thorium series nuclides 228ra 212bi and potassium in soil of a granitic belt were examined in relation to their surface area of soil clay mineral composition and the sio2 and fe contents in soil which is less weathered and has a surface area of around 10 m2 g the 238u 226ra 210pb 228ra and 40k contents increase with an increase the sio2 content related to the elemental compositions of their parents rocks in homologous soils resulting from progressive weathering the 238u 226ra 210pb and 228ra contents are found to increase with increasing surface area for an homologous soil which is free from the clay consisting of three layer units the 40k content decrease with increasing surface area however in an homologous soil which contains a clay consisting of three layer units the 40k content is not surface area dependent

predicting regolith thickness in the complex weathering setting of the central mt lofty ranges south australia abstract we describe a model to predict regolith thickness in a 128 000 ha study area in the central mt lofty ranges in south australia the term regolith encompasses soil a and b horizons and highly weathered bedrock c horizon the thickness of the regolith has a major control on water holding capacity for plant growth and movement of water through the landscape and as such is important in hydropedological modelling and in evaluating land suitability e g for forestry and agriculture thickness estimates also have direct application in mineral exploration and seismic risk assessment geology and landscape evolution within the study area is complex reflecting the variable nature of bedrock materials and the partial preservation of deeply weathered profiles as a consequence of weathering processes dating to the cenozoic or possibly older these characteristics together with strong climatic gradients make the study area an ideal location to understand environmental and landscape evolution controls on weathering depth the area also features weathered landscape analogues to many parts of southern australia we use a digital soil mapping rules based approach to develop a model to predict regolith thickness this model uses statistically based relationships established between 714 regolith thickness measurements and 29 geographic environmental covariates including geology geochemistry terrain and climate themes and with a ground resolution of 10 m accuracy testing based on a 75 25 training test data split on the resulting map established a correlation r 2 of 0 64 this result is encouraging and is a significant advance over regolith depth mapping by traditionally based regolith landscape mapping methods finally it leads the way towards a nationally consistent regolith thickness map for landscape scale environmental simulation modelling and decision support

a novel method for determining residence times of river and lake sediments based on disequilibrium in the thorium decay series sediment fluxes in rivers have proved difficult to measure or model at timescales relevant to land and water resource management decisions determining transport rates and residence times is complicated by the intermittent movement and temporary storage of sediments in natural streams this paper presents a new tool for estimating the residence times of river borne sediments based on the observed disequilibria between the naturally occurring radionuclides 228ra and 232th in the thorium decay series disequilibrium between concentrations of 228ra half life 5 75 years and its long lived parent 232th has been observed in marine environments and in terrestrial freshwaters but has not been previously reported in fluvial sediments or soils here we report 228ra excesses in sandy stream and silty lake sediments from southeastern australia the excess is developed in hillslope soils in the catchment headwaters and begins to decay back to secular equilibrium once the sediment is finally removed from contact with the soil water the short half life of 228ra enables this process to be used to investigate fluvial sediment transfers and alluvial and lacustrine sediment storages over the past 30 years when combined with indicators of sediment source such as 226ra 232th and 230th 232th ratios observation of this excess should provide a useful new tool for examining the residence and transit times of bed load and suspended load sediments in streams and lakes

constraining the transport time of lithogenic sediments to the okinawa trough east china sea the transport time of siliciclastic sediments from their continental sites of formation to their final location of deposition on the seafloor is an important parameter bearing on land sea interactions climate variability and understanding of marine sediment record 234u 238u activity ratios of the lithogenic fraction from late quaternary sediment deposited in the okinawa trough east china sea were reported in this study on basis of 234u 238u activity ratios the comminution ages and transport times were calculated using recoil loss factors f derived from different equations based on grain size distribution the transport times were longer approximately 200 100 kyr for the okinawa trough sediments deposited between 27 and 14 ka decreased gradually between 14 and 7 ka and stayed relatively short 100 kyr thereafter mineralogical geochemical and isotopic evidences indicate that changes in sediment transport time correspond well with the shift of sediment provenance predominantly from asia s interior prior to 14 ka to taiwan island after 7 ka this study offers the first and robust constraint on time scale of sediment transport process in east asia marginal sea which is constrained by unique sediment source to sink transport pattern the result illustrates the potential of this approach to decipher climate related changes in the mode of supply of lithogenic sediment to marginal seas it also highlights current difficulties in obtaining quantitative estimates of comminution age mostly because of uncertainties in estimating the recoil loss factor

particle size related mineral magnetic source sediment linkages in the rhode river catchment maryland usa characterization of both the source materials and the bottom sediments of an estuary by magnetic characters on a particle size basis allows the source of the bottom sediments to be determined and indicates a shift in sediment sources corresponding to changing land use patterns the major source of the sediments in the lower part of cores from the middle of the estuary is eroding shorelines soil derived particulates from the uplands dominate the upper part of the cores this change in source occurred in the early part of the 19th century the magnetic character of the most recent sediments suggests a progressive depletion through time of the upland soils in the finest fractions

particle dynamics the continuum of bedrock to alluvial river segments abstract particle dynamics refers to production erosion transport and storage of particulate material including mineral sediment and organic matter particle dynamics differ significantly between the end members of bedrock and alluvial river segments and between alluvial river segments with different grain size distributions bedrock segments are supply limited and resistant to change with relatively slow linear adjustments and predominantly erosion and transport particle dynamics in alluvial segments in contrast are transport limited and dominated by storage of mineral sediment and production of organic matter alluvial segments are resilient to change with relatively rapid multidirectional adjustments and stronger internal influences because of feedbacks between particles and biota bedrock segments are the governors of erosion within a river network whereas alluvial segments are the biogeochemical reactors fundamental research questions for both types of river segments center on particle dynamics which limit network scale incision in response to base level fall bedrock segments and habitat biogeochemical reactions and biomass production alluvial segments these characterizations illuminate how the spatial arrangement of bedrock and alluvial segments within a river network influence network scale resistance and resilience to external changes in relative base level climate and human activities

the importance of surface waves in vibration study and the use of rayleigh waves for estimating the dynamic characteristics of soils vibrations generated during civil engineering work are often dominated by prominent surface waves the propagation of which is strongly influenced by site conditions the effects of soil properties on the shape amplitude and duration of rayleigh waves are shown from synthetic seismograms surface waves are dispersive and may be processed to retrieve the shear characteristics shear wave velocityvs and shear quality factorqs of soil layers a seismic survey was conducted on a site limelette belgium to determine the dynamic characteristics of the ground layers from different seismic methods various refraction profiles and one cross hole test were performed to obtain shear wave velocity profiles the comparison of surface wave inversion method with other techniques shows that the former leads to slightly underestimatedvs values

proximal and remote spectroscopic characterisation of regolith in the albany fraser orogen western australia abstract vast parts of the australian continent are prospective for precious and base metal mineralisation but exploration is hindered by extensive cover of often deeply reaching regolith new operational exploration methods are required that can help to characterise the cover and provide information about bedrock signatures this paper shows how mineral mapping information from a combination of satellite multispectral advanced spaceborne thermal emission and reflection radiometer aster imagery and drill core hyperspectral profiling data hylogging can be used to unravel the regolith stratigraphy and to describe regional variations of regolith landforms delivering important information for mineral exploration the case study is located in the neale tenements in the northeastern albany fraser orogen western australia which is prospective for tropicana style gold mineralisation by interpretation of indicator minerals from hyperspectral drill hole logging data the regolith stratigraphy atop a metamorphic basement comprising saprock ferrugineous saprolite kaolinitic saprolite silcrete and transported cover is recorded in cm detail important mineralogical parameters extracted from the hyperspectral subsurface data and validated by xrd and ftir are 1 the abundance and type of iron oxides 2 the abundance and crystallinity of kaolinite 3 the abundance and composition of primary minerals such as white mica and 4 the abundance of quartz the hylogging data served as ground control points for mineral mapping information provided by csiro s aster geoscience products which are a collection of mineral maps that highlight variations in the abundance type or chemistry of selected mineral groups key aster geoscience products for regolith characterisation were the ferric oxide and aloh abundance and composition images the comparison of the surface with the subsurface data suggests three major different regolith landforms including erosional depositional and relict areas which were used to generate a map showing transported versus relict and erosional areas erosional domains were mapped out in great detail providing important information for exploration in saprolite dominated areas furthermore source areas of transported material could be identified which may help to understand the distribution of geochemical signatures collected during for example geochemical soil sampling projects

identification of lateral discontinuities via multi offset phase analysis of surface wave data surface wave methods are based on the inversion of observed rayleigh wave phase velocity dispersion curves the goal is to estimate mainly the shear wave velocity profile of the investigated site the model used for the interpretation is 1d hence results obtained wherever lateral variations are present cannot be considered reliable in this paper we study four synthetic models all with a lateral heterogeneity when we process the entire corresponding seismograms with traditional f k approach the resulting 1d profiles are representative of the subsurface properties averaged over the whole length of the receivers lines these results show that classical analysis disregards evidences of sharp lateral velocity changes even when they show up in the raw seismograms in our research we implement and test over the same synthetic models a novel robust automated method to check the appropriateness of 1d model assumption and locate the discontinuities this new approach is a development of the recent multi offset phase analysis with the following further advantages it does not need previous noise evaluation and more than one shot only once the discontinuities are clearly identified we confidently perform classical f k dispersion curve extraction and inversion separately on both sides of the discontinuity thus the final results obtained by putting side by side the 1d profiles are correct 2d reconstructions of the discontinuous s wave distributions obtained without any additional ad hoc hypotheses

digital lithology mapping from airborne geophysical and remote sensing data in the melville peninsula northern canada using a neural network approach abstract feedforward neural networks were used to identify bedrock types from satellite images and airborne geophysical data of the melville peninsula northern canada the first experiment on rock outcrop pixels demonstrated that more than 90 classification accuracy was achieved with as few as 150 training samples 0 5 of rock outcrop pixels the second experiment consisted of re building the bedrock geology map based on all pixels except water pixels in the area the results demonstrated that greater than 85 classification accuracy can be obtained with only 150 training samples 0 17 of all pixels in training area tests with more training samples were also performed in both experiments and only a moderately higher accuracy was obtained in both experiments the geophysical data were the controlling factors in the classification the landsat tm data contributed to classification results only for the experiment on rock outcrop pixels

evaluation of salt marsh hydrology using radium as a tracer abstract radium isotopes provide unique and important information concerning water exchange in a salt marsh tidal creek system seasonal radium data collected over five tidal cycles from a creek draining a south carolina salt marsh radium and thorium data from the adjacent marsh sediments and interstitial water radium data from the drainage basin are modeled to yield residence times of water in the upper 10 cm of the marsh sediments ranging from less than one to twenty six hours water residence times derived from chambers which directly measure the flux of ra isotopes to the creek waters agree well with these calculated interstitial water turnover times dissolved radium activities in the tidal creek were greater during the summer than during other times of the year we suspect that seasonal changes in the storage of organic carbon and rates of bioturbation lead to net reduction of radium carrier phases in the marsh sediments during the summer

regolith landform processes and geochemical exploration for base metal deposits in regolith dominated terrains of the mt isa region northwest queensland australia abstract the regolith in the mt isa region of queensland consists of a variety of saprolites and duricrusts developed on proterozoic basement rocks and fresh to weathered mesozoic tertiary and quaternary cover all of which has impeded base metals exploration this paper presents an overview of some of the regolith geochemical work conducted in the mt isa region as part of an industry supported three year crc leme amira project a complex weathering and landscape history has produced a landscape of a continuously exposed and exhumed basement rocks that have undergone varying intensities of weathering and partial stripping b weathered and locally eroded mesozoic cover sequences and c areas with younger transported cover concealing basement and mesozoic cover various regolith sample media have been evaluated at a number of prospects and deposits which represent different regolith landform terrains and landscape history geochemical dispersion processes and models are presented and false anomalies explained where ferruginous duricrust or ferruginous nodular gravel are preserved on weathered bedrock on an eroded plateau they exhibit large 500 m multi element as pb sb dispersion haloes and are useful sampling media dispersion haloes in truncated profiles on weathered bedrock covered with colluvium are restricted are limited to tens of metres from subcrop of the source and contrast to the extensive anomalies in ferruginous duricrust and nodules geochemical exploration in covered areas depends on the possible presence of dispersion through the sediments or leakage along faults or fractures but may be complicated by high metal backgrounds in the sediments themselves some of the most prominent anomalies occur in ferruginous materials and soils representing emergent residual terrain developed on mesozoic sediments these are largely due to weathering of sulfide mineralization that continued during submergence in a marine environment with hydromorphic dispersion into the sediments as they accumulated multi element cu as zn sb au anomalies occur in basal sediments and at the unconformity due to a combination of clastic and hydromorphic dispersion and represent a useful sample target metal rich horizons in weathered sediments higher in the sequence can also be targeted particularly by specifically sampling ferruginous units and fragments however these are less certainly related to mineralization zinc and cu concentrated in fe and mn oxides at redox fronts may be derived by leaching from the sediments with concentration in the sesquioxides and be unrelated to any proximal basement mineralization in all these regolith dominated terrains a clear understanding of local geomorphology regolith framework topography of unconformities and the origins of ferruginous materials is essential to sample medium selection and data interpretation

geochemical balance of lateritization processes and climatic signatures in weathering profiles overlain by ferricretes in central africa a simple geochemical balance of lateritization processes governing the development of several tens of meters of weathering profiles overlain by ferricretes is estimated on the basis of detailed mineralogical and geochemical data the lateritic weathering mantle of the haut mbomou area in central africa is composed of different weathering layers described from the base to the top of vertical profiles as a saprolite a mottled clay layer a soft nodular layer a soft ferricrete and a ferricrete in which kaolinite gibbsite goethite and hematite occur in various quantities incongruent dissolution of kaolinite leads to the formation of gibbsite in the upper saprolite whereas the hematite does not clearly replace the kaolinite according to an epigene process in the upper ferruginous layers of the profiles instead that kaolinite is also transformed into gibbsite according to an incongruent dissolution under hydrated and reducing conditions induced by a relatively humid climatic pattern the respective relations of the silica iron and aluminum balances and the al substitution rate of the hematite on the one hand and of rhg rhg 100 hematite hematite goethite and the kaolinite on the other hand to the consumption or the release of protons h permit differentiation of aggrading ferruginization and degradation processes operating in the different lateritic weathering profiles the al substitution rate of the fe oxyhydroxides varies according to the nature of lateritization processes e g saprolitic weathering and aggrading ferruginization vs degradation the observations and results indicate that the ferruginization process of the weathering materials of parent rocks is not a simple ongoing process as often thought this suggests that the actual lateritic weathering mantle of the haut mbomou area may result from different stages of weathering and erosion during climatic changes

206pb 230th 234u 238u and 207pb 235u geochronology of quaternary opal yucca mountain nevada abstract u th pb isotopic systems have been studied in submillimeter thick outermost layers of quaternary opal occurring in calcite silica fracture and cavity coatings within tertiary tuffs at yucca mountain nevada usa these coatings preserve a record of paleohydrologic conditions at this site which is being evaluated as a potential high level nuclear waste repository the opal precipitated from groundwater is variably enriched in 234u measured 234u 238u activity ratio 1 124 6 179 and has high u 30 313 ppm low th 0 008 3 7 ppm and low common pb concentrations measured 206pb 204pb up to 11 370 it has been demonstrated that the laboratory acid treatment used in this study to clean sample surfaces and to remove adherent calcite did not disturb u th pb isotopic systems in opal the opal ages calculated from 206pb 238u and 207pb 235u ratios display strong reverse discordance because of excess radiogenic 206pb derived from the elevated initial 234u the data are best interpreted using projections of a new four dimensional concordia diagram defined by 206pb 238u 207pb 235u 234u 238uactivity and 230th 238uactivity ages and initial 234u 238u activity ratios have been calculated using different projections of this diagram and tested for concordance the data are discordant that is observed 207pb 235u ages of 170 32 2 to 1772 40 ka are systematically older than 230th u ages of 34 1 0 6 to 452 32 ka the age discordance is not a result of migration of uranium and its decay products under the open system conditions but a consequence of noninstantaneous growth of opal combined u pb and 230th u ages support the model of slow mineral deposition at the rates of millimeters per million years resulting in layering on a scale too fine for mechanical sampling in this case u pb ages provide more accurate estimates of the average age for mixed multiage samples than 230th u ages because ages based on shorter lived isotopes are nonlinearly biased by younger mineral additions use of the combined u th pb technique to date yucca mountain quaternary opals significantly extends the age range beyond that of the 230th u dating method and shows that selected fracture pathways in the unsaturated zone felsic tuffs of yucca mountain have been active throughout the quaternary

radium precipitation and extreme 238u series disequilibrium along the dead sea coast israel abstract very intense gamma ray emissions produced by nuclides in the 238 u decay series were measured in active and relict spring deposits along the dead sea coast precipitates of ra near sites of modern springs provide a local source of rn to coexisting waters relict spring deposits representing prior dead sea levels contain high concentrations of ra the ra in both cases has been derived from the dead sea waters or from the dead sea in combination with a ra component from the primary spring water and coprecipitated with hydrous oxides of mn and fe the metal oxides precipitated in response to the mixing of the fresher spring waters with the dead sea brine

the influence of organic debris on channel morphology and bedload transport in a new zealand forest stream the behaviour and form of and bedload sediment transport through a 3 5 m wide forest stream have been monitored for nearly three years bedload transport is highly episodic and spatially variable and is controlled less by water discharge than by sediment availability organic debris in the channel creates temporary base levels and sites at which coarse sediment may remain stored for long periods collapse or disruption of log and debris jams makes sediment available for transport in only a small proportion of the runoff events that are actually competent to move the material even then sediment travels only a short distance before being redeposited frequently behind debris accumulations further downstream rates of sediment transport during a given runoff event can vary markedly over short distances along the stream again depending on whether sediment was made available for transport by log jam collapse upstream organic debris is therefore a major constraint on the application of physical laws and theories to explaining sediment movement in and the morphology of this stream

boolean and fuzzy methods for identifying lateritic regoliths in the brazilian amazon using gamma ray spectrometric and topographic data abstract airborne gamma ray spectrometry is relatively well understood when associated with rocks but the response and radioelement distribution in weathered materials is less known this work used airborne gamma ray spectrometry and altimetry to identify domains with higher probability of occurrence of lateritic crust and dismantling products in an area located in the west of the brazilian amazon map algebra was used through the boolean and fuzzy techniques to create predictability digital models highlighting favorable areas for the occurrence of lateritic crusts the index overlay method was used in the boolean technique the fuzzy technique used the fuzzy algebraic product operator fuzzy algebraic sum operator and fuzzy gamma operator both models showed good correlation between the favorability predicted and the presence of crusts in the field however the fuzzy model showed higher correlation and highlighted areas not identified by the boolean model in contrast the boolean model allowed the visualization of the areas related to the influence of each variable or its possible combinations individually on the final map thus the identification of lateritic crusts based on mathematic models applied to altimetric and airborne gamma ray spectrometric data is a new tool that will contribute significantly to geological mapping and to the understanding related to the response and radioelement distribution in weathered materials

landform classification from a digital elevation model and satellite imagery the iranian soil and water research institute has been involved in mapping the soils of iran and classifying landforms for the last 60 years however the accuracy of traditional landform maps is very low about 55 to date aerial photographs and topographic maps have been used for landform classification studies the principal objective of this research is to propose a quantitative approach for landform classification based on a 10 m resolution digital elevation model dem and some use of an advanced spaceborne thermal emission and reflection radiometer aster image in order to extract and identify the various landforms slope elevation range and stream network pattern were used as basic identifying parameters these are extractable from a dem further aster images were required to identify the general outline shape of a landform type and the presence or absence of gravel this study encompassed a relatively large watershed of 451 183 ha with a total elevation difference of 2445 m and a variety of landforms from flat river alluvial plains to steep mountains classification accuracy ranged from 91 8 to 99 6 with an average of 96 7 based upon extensive ground truthing since similar digital and aster image information is available for iran an accurate landform map can now be produced for the whole country the main advantages of this approach are accuracy lower demands on time and funds for field work and ready availability of required data for many regions of the world

california integrated seismic network cisn local magnitude determination in california and vicinity determining local magnitude m l in a manner that is uniform and internally consistent for earthquakes throughout california and the vicinity is an important component of the california integrated seismic network cisn we present a new local magnitude attenuation function and corresponding station adjustments that are valid throughout california the new attenuation function is an analytic function of the radial hypocentral distance between 1 and 500 km associated station adjustments are also available for 1185 horizontal seismometer and accelerometer channels from five seismic networks operating in california the new attenuation function and adjustments provide several advantages to cisn they allow a more robust m l computation the m ls are more consistent between northern and southern california than they have been in the past and because adjustments are now available for more station network channel location codes sncls m ls can be computed for small earthquakes in more locations than was previously possible in addition to describing our method for calibrating the new cisn m l we also present a tool for adding adjustments for new or upgraded stations

west african lateritic pediments landform regolith evolution processes and mineral exploration pitfalls this paper is a contribution to the understanding of surface dynamics of tropical shields over geological timescales emphasis is put on the fundamental and applied implications of regolith production and dispersion processes through the formation dissection and preservation of landforms it is based on the case study of sub saharan west africa which recorded neogene 24 3 ma stepwise dissection of its topography through the emplacement of three lateritic pediment systems which still occupy most of its surface pediments are erosional transportation slopes having been weathered and duricrusted pediment regolith associations therefore depend on the parent rock transport dynamics and preservation of the material having transited on their surface as well as on the intensity of their weathering duricrusting iron oxy hydroxide cemented clastic sediments detrital ferricretes and unconsolidated clastic sediments are the dominant outcropping material and as such represent a challenge for mineral exploration that relies on surface geochemical sampling to detect metal concentration in the bedrock landform regolith mapping beyond the scale of modern interfluves combined with paleolandscape reconstitution are relevant to provide exploration guides for i interpreting geochemical anomalies on pediments ii tracing their potential source when they have been transported on pediments and iii targeting suspected ore bodies concealed beneath pediment s past and present latitudinal climatic zonation of pedimentation and weathering patterns suggests a gradation of pedimentation process across the intertropical zone and explains why pediments may have been overlooked in equatorial environments with implications for mineral exploration successive pediment systems adapted to uneven knickzone bearing river networks producing a spatially consistent and reduced 80 m stepping pattern of pediments independent from elevation or distance to base level pediments pediplains are therefore not proxies of uplift and their preservation over geological timescales typifies regions submitted to 10 m my erosion rates the identification and study of lateritic pediments bear important implications on shield sediment routing systems and a better access to the bedrock and its resources which may still be underestimated in the tropics

modes tempo and spatial variability of cenozoic cratonic denudation the west african example 1 quantifying long term erosion of tropical shields is crucial to constraining the role of lateritic regolith covers as prominent sinks and sources of co 2 and sediments in the context of long term cenozoic climate change it is also a key to understanding long term landform evolution processes operating over most of the continental surface and their control onto the sediment routing system we study the surface evolution of west africa over three erosion periods 45 24 24 11 and 11 0 ma recorded by relicts of three subcontinental scale lateritic paleolandsurfaces whose age is bracketed by 39 ar 40 ar dating of lateritic k mn oxides denudation depths and rates compiled from 380 field stations show that despite heterogeneities confined to early inherited reliefs the subregion underwent low and homogeneous denudation 2 20 m ma 1 over most of its surface whatever the considered time interval this homogeneity is further documented by a worldwide compilation of cratonic denudation rates over long term intermediate and modern cenozoic time scales 10 0 10 7 yr these results allow defining a steady state cratonic denudation regime that is weathering limited i e controlled by the thickness of the lateritic regolith available for stripping steady state cratonic denudation regimes are enabled by maintained compartmentalization of the base levels between river knick points controlled by relief inheritance under such regimes lowering of base levels and their fossilization are primarily imposed by long term eustatic sea level fall and climate rather than by epeirogeny the expression of steady state cratonic denudation regimes in clastic sedimentary fluxes remains to be investigated components 9 200 words 13 figures 2 tables

significance of weathering and regolith landscape evolution for mineral exploration in the ne albany fraser orogen western australia abstract the albany fraser orogen afo southeast western australia is an underexplored deeply weathered regolith dominated terrain that has undergone complex weathering associated with various superimposed climatic events for effective geochemical exploration in the afo integrating landscape evolution with mineralogical and geochemical variations of regolith and bedrock provides fundamental understanding of mechanical and hydromorphic dispersion of ore and pathfinder elements associated with the different weathering processes in the neale tenement northeast of the afo a residual weathering profile that is 20 55 m thick was developed under warm and humid climatic conditions over undulating proterozoic sheared granitoids gneisses schists and au bearing mafic rocks from the base the typical weathering profile consists of saprock lower ferruginous saprolite upper kaolinitic saprolite and discontinuous silcrete duricrust or its laterally coeval lateritic residuum these types of duricrusts change laterally into areas of poorly cemented kaolinitic grits or loose lateritic pisoliths and nodules lateritic residuum probably formed on remnant plateaus and was transported mechanically under arid climatic conditions over short distances filling valleys to the southeast erosion of lateritic residuum exposes the underlying saprolite and together with dilution by aeolian sands constitutes the transported overburden 2 25 m thick the reworked lateritic materials cover the preserved silcrete duricrusts in valleys the lower ferruginous saprolite and lateritic residuum are well developed over mafic and sulphide bearing bedrocks where weathering of ferromagnesian minerals and sulphides led to enrichment of fe cu ni cr co v and zn in these units kaolinitic saprolite and the overlying pedogenic silcrete are best developed over alkali granites and quartzofeldspathic gneisses which are barren in au and transition elements and enriched in silica alumina rare earth and high field strength elements a residual au anomaly is formed in the lower ferruginous saprolite above a au bearing mafic intrusion at the hercules prospect south of the neale tenement without any expression in the overlying soil 2 000 m 2 000 250 m 250 53 m 53 2 m and

source parameter estimation for large bermed surface chemical explosions abstract near source accelerograms 0 2 to 2 0 km range were acquired from a series of bermed surface charges 0 075 to 1 65 kilotons detonated in alluvium at a test site near yuma arizona the areal extent of the explosion test beds radii from 18 to 54 m affords the unique opportunity to study wave propagation from and source parameters of large surface explosions at near source ranges p and sv rayleigh phases are identified using particle motions rayleigh waves at an intermediate range transition to a combination of higher mode and fundamental mode rayleigh waves at the farthest range the power law decay rates for body waves radial at r 1 8 and vertical at r 1 4 and surface waves radial at r 1 0 and vertical at r 0 8 are further indication of complex propagation effects in the shallow alluvial geology as a result of this complexity and the two orders of magnitude range of explosive yields available seismic source parameters are obtained with full waveform spectral ratios source corner frequency is proportional to the radius of the explosion test beds and long period level relative moment scales linearly with yield spectral ratio yield estimates using smaller explosions as standard or calibration events gave absolute yield estimates within 6 to 35 of the true yield with a linear scaling law the precision of individual yield estimates is reflected by multiplicative errors of 1 11 to 1 17 full waveform spectral ratio corner frequency estimates compare favorably with reglonal p wave corner frequencies and validate the use of the spectral ratio technique for near source seismic data

modeling surface waves from aboveground and underground explosions in alluvium and limestone the may 2012 humble redwood iii hriii experiment series in new mexico provides a unique dataset to study surface wave generation from explosions conducted above and underground for different rock types four 90 6 kg trinitrotoluene equivalent explosions were detonated either at 2 m height of burst hob or 7 m depth of burial dob at separate alluvium and limestone test sites for the alluvium site data from a temporary seismoacoustic network show that fundamental mode surface waves graphic 1 from the 7 m dob in alluvium shot were four to five times larger than the above alluvium shot the graphic 2 amplitudes from the 7 m dob limestone shot were 15 times larger than graphic 3 recorded from the collocated 2 m hob shot to model these differences in graphic 4 we generated 1d velocity models for both test sites using observed surface wave dispersion we considered two different methods for synthetic seismogram generation for the aboveground shots we have coupled near field blast wave pressures and shapes with source medium properties to model seismic data at distance for the underground shots we use explosion source theory to estimate a moment for scaling explosion synthetics for both above and underground shots the synthetics provide excellent fits to the observed 1 5 hz graphic 5 data this modeling provides a viable technique to predict peak particle velocities for surface and aboveground explosions in different rock types that can be used to estimate combined seismoacoustic yields online material movies of four explosions studied in this paper 1 embed inline graphic 1 gif 2 embed inline graphic 2 gif 3 embed inline graphic 3 gif 4 embed inline graphic 4 gif 5 embed inline graphic 5 gif

determining the origins and history of sedimentation in an underground river system using natural and fallout radionuclides abstract natural and anthropogenic radionuclides were used to characterize the source of sediment reaching the underground river in the karst system at jenolan new south wales australia it was found that the relationship between 226 ra and 232 th concentrations in both spatially averaged soil samples and transported sediments distinguished between two of the most likely source subcatchments sedimentary sequences collected from within the underground system showed that contemporary deposition was made up of an equal mixture of sediment from these two sources however at least three earlier deposition periods were also identifiable each with different relative contributions from the source catchments the first appearance of 137 cs in the sedimentary sequence and correlations with historical information provided a chronology for these changes and it is concluded that the contemporary phase was initiated in the early 1950s most probably by forestry activities this work demonstrates that natural radioactivity can be used as a tracer of the origins of sediment providing an important new approach to problems in sediment supply transport and deposition

chemical and physical erosion rhythms of the west african cenozoic morphogenesis the 39 ar 40 ar dating of supergene k mn oxides chemical weathering and mechanical erosion are first order processes of long term tropical morphogenesis which is still poorly deciphered for lack of time constraints we address this issue by laser probe 39ar 40ar dating of generations of cryptomelane k1 2mn8o16 nh2o from the manganese ore deposit of tambao in northern burkina faso this mn deposit results from the supergene weathering of carbonate and silicate mn protores underneath lateritic palaeolandsurfaces it consists of an upper cryptomelane rich domain and a lower domain where pyrolusite b mno2 is the dominant mn oxide the oldest 39ar 40ar ages 59 45 ma are obtained on surface outcrops while the youngest ones characterize deep oxidation fronts 3 4 2 9 ma apparent correlations of 39ar 40ar age groups with d18o and eustatic curves allow definition of the different stages of morphogenesis paleocene eocene ages 59 45 ma bracket a greenhouse period propitious to bauxitic weathering the lack of significant ages between 45 and 29 ma characterizes a period dominated by mechanical erosion during which detrital sediments including lateritic materials were accumulated in intracratonic basins allowing the exhumation of a new lateritic landsurface two major weathering periods separated by a second erosion episode 24 18 ma are also depicted at the end of oligocene 29 24 ma and lower to mid miocene 18 11 5 ma in the upper domain during which newly shaped land surfaces conspicuously weathered the shorter weathering and erosion episodes recorded in the lower domain from 18 to 2 9 ma led to the final geomorphic changes that were conducive to the formation of glacis the preservation of old cryptomelane 59 45 ma in the upper part of the ore deposit indicates a cenozoic denudation limited to the erosion of previous bauxites and partly of ferricretes

quantitative analysis of land surface topography land surface topography significantly affects the processes of runoff and erosion a system which determines slope aspect and curvature in both the down slope and across slope directions is developed for an altitude matrix also the upslope drainage area and maximum drainage distance are determined for every point within the altitude matrix a fortran 66 program performs the analysis

determination of earthquake energy release and ml using terrascope we estimated the energy radiated by earthquakes in southern california using on scale very broadband recordings from terrascope the method we used involves time integration of the squared ground motion velocity and empirical determination of the distance attenuation function and the station corrections the time integral is typically taken over a duration of 2 min after the p wave arrival the attenuation curve for the energy integral we obtained is given by q r cr n exp kr r 2 2 h ref 2 with c 0 49710 n 1 0322 k 0 0035 km 1 and h ref 8 km where is the epicentral distance a similar method was used to determine m l using terrascope data the station corrections for m l are determined such that the m l values determined from terrascope agree with those from the traditional optical wood anderson seismographs for 1 5 6 5 m l saturates the ratio e s m 0 m 0 seismic moment a measure of the average stress drop for six earthquakes the 1989 montebello earthquake m l 4 6 the 1989 pasadena earthquake m l 4 9 the 1990 upland earthquake m l 5 2 the 1991 sierra madre earthquake m l 5 8 the 1992 joshua tree earthquake m l 6 1 and the 1992 landers earthquake m w 7 3 are about 10 times larger than those of the others that include the aftershocks of the 1987 whittier narrows earthquake the sierra madre earthquake the joshua tree earthquake and the two earthquakes on the san jacinto fault the difference in the stress drop between the mainshock and their large aftershocks may be similar to that between earthquakes on a fault with long and short repeat times the aftershocks which occurred on the fault plane where the mainshock slippage occurred had a very short time to heal hence a low stress drop the repeat time of the major earthquakes on the frontal fault systems in the transverse ranges in southern california is believed to be very long a few thousand years hence the events in the transverse ranges may have higher stress drops than those of the events occurring on faults with shorter repeat times such as the san andreas fault and the san jacinto fault the observation that very high stress drop events occur in the transverse ranges and the los angeles basin has important implications for the regional seismic potential the occurrence of these high stress drop events near the bottom of the seismogenic zone strongly suggests that these fault systems are capable of supporting high stress that will eventually be released in major seismic events characterization of earthquakes in terms of the e s m 0 ratio using broadband data will help delineate the spatial distribution of seismogenic stresses in the los angeles basin and the transverse ranges

a new procedure for gridding elevation and stream line data with automatic removal of spurious pits abstract a morphological approach to the interpolation of regular grid digital elevation models dems from surface specific elevation data points and selected stream lines is described the approach has given rise to a computationally efficient interpolation procedure which couples the minimization of a terrain specific roughness penalty with an automatic drainage enforcement algorithm the drainage enforcement algorithm removes spurious sinks or pits yielding dems which may be used to advantage in hydrological process studies the drainage enforcement algorithm has also been found to significantly increase the accuracy of dems interpolated from sparse but well chosen surface specific elevation data moreover it facilitates the detection of errors in elevation data that would not be detected by more conventional statistical means and forms a sound physical basis for cartographic generalization

210pb as a chronometer and tracer burrinjuck reservoir australia cores taken at burrinjuck reservoir in southeastern new south wales have been dated using the first appearance of opb dating models reproduced the known chronology correlation analysis shows no significant relationship between original pb unsupp concentration and grain size sedimentation rate or loss on ignition differences in sediment source may explain the variations in opb a simple provenance model has been used to interpret the ratio of original opb unsupp 226ra as a tracer of topsoils and subsoils high ratios in the reservoir sediments probably indicate eroded topsoils and low ratios eroded subsoils 37cs charcoal bushfire correlations and annual grass pollen peaks none of the main

temporal merging of remote sensing data to enhance spectral regolith lithological and alteration patterns for regional mineral exploration abstract remote sensing has been widely used to map geological structure regolith materials and hydrothermal alteration minerals in different regions of the world based largely on the spectral characteristics of clay carbonate and iron oxide minerals given that features related to minerals may form very subtle patterns in landsat imagery finding suitable methods for enhancing the spectral information due to alteration minerals has been the subject of much research since the satellites were launched although multispectral sensors such as landsat do not have enough spectral resolution to distinguish between specific minerals effective processing of the data does yield useful images for regional exploration and targeting when combined with a good understanding of the associated landforms aster and various airborne systems can now provide useful high resolution mineral information however the cost and time taken to acquire and process good resolution spectral data should now be balanced against the enhanced spectral discrimination possible using temporal merging or data stacking from the existing landsat data archive dating back to 1972 one critical characteristic of the spectra related to surface mineral composition is its persistence over time this study proposes a further enhancement to the data using temporal merging to create images that are both easier to interpret and more reliable indicators of lithology and alteration the new approach is to select a large number of scenes typically separated by two or more years and to merge the data for each band to give a cumulative spectral signature the technique of stacking landsat data to create a new dataset with much greater spectral depth is termed landsat tm3 or landsat tm temporal merge for terrain mapping this emphasises not only the process used to create the dataset but also the dominant use to which these data are ideally suited namely mapping geological and mineral related terrains

determining the source characteristics of explosions near the earth s surface we present a method to determine source characteristics of explosions near the earth s surface the technique accounts for the reduction in amplitudes as the explosion depth approaches the free surface and less energy is coupled into the ground we apply the method to the humming roadrunner series of shallow explosions in new mexico where the yields and depths are known knowledge of the material properties is needed for both source coupling excitation and the free surface effect although there is the expected trade off between depth and yield the estimated yields are close to the known values when the depth is constrained to the free surface we then apply the method to a regionally recorded explosion in syria we estimate an explosive yield less than the 60 t claimed by sources in the open press the modifications to the method allow us to apply the technique to new classes of events

sediment transfer and transformation of an alluvial valley floor the river south tyne northumbria u k the amounts of alluvial storage and the mechanisms responsible for the dispersal of sediment associated with historic metal mining are examined for a 115 year timespan on a 22 km reach of the river south tyne northern england analysis of lateral and vertical channel change over this period the extent of actively reworked gravels and identification of metals in alluvial units show five sedimentation zones separated by more stable reaches aggradation in the late nineteenth century was followed by a period of storage and local reworking and then incision some reaches show short term storage of sediment injected from tributaries which may be dispersed by floods there is some evidence of transfer of sediment bodies downvalley within sedimentation zones and of a sediment wave movement between zones in lower parts of the south tyne investigated present day incision the variation in the area of actively reworked gravel spreads and the widespread dispersal of fine grained toxic metal mining wastes all have practical implications the intricate response of the channel system to historic changes in sediment supply is not readily described by either a complex response model or a simple translatory wave

integration of landsat tm gamma ray magnetic and field data to discriminate lithological units in vegetatedgranite gneiss terrain abstract image classification of geological units in vegetated granite gneiss terrain from multispectral data is hampered by vegetation cover and limited spectral contrast of its lithological variations in this paper an alternative methodology is presented employing airborne gamma ray spectrometry and magnetic data the methodology includes the selection of combinations of data channels and their transformations to enhance the discriminative power of the lithology classification an analysis of the training set compiled from 2 795 field stations showed that the potassium thorium and uranium gamma ray spectrometry and total and residual magnetic field channels provided an overall classification success rate of 65 for a total of 10 lithological units parametric classifications based on this training set yielded 67 coincidence with the geological map whereas a neural network classifier provided only 23 coincidence exploiting the spatial autocorrelation of the geophysical signatures by adding averaged filtered channels slightly improved the coincidence percentage to 70 and enhanced the continuity of linear enclaves within larger lithological units the contribution of magnetic data to the classification depends on the extent to which the anomaly spectrum and its processed derivatives reflect surface geology we found that both the short and long wavelengths in the spectrum contributed to the classification performance this is explained by the geological structure of the area where both broad and narrow units extend downward subvertically a comparison of our results to regional geological map patterns identified targets for map refinement and exploration

deep learning based approach for landform classification from integrated data sources of digital elevation model and imagery abstract landform classification is one of the most important aspects in geomorphological research dividing the earth s surface into diverse geomorphological types thus an accurate classification of landforms is a key procedure in describing the topographic characteristics of a given area and understanding their inner geomorphological formation processes however landform types are not always independent of one another due to the complexity and dynamics of interior and external forces furthermore transitional landforms with gradually changing surface morphologies are widely distributed on the earth s surface with this situation classifying these complex and transitional landforms with traditional landform classification methods is hard in this study a deep learning dl algorithm was introduced aiming at automatically classifying complex and transitional landforms this algorithm was trained to learn and extract landform features from integrated data sources these integrated data sources contain different combinations of imagery digital elevation models dems and terrain derivatives the loess plateau in china which contains complex and transitional loess landforms was selected as the study area for data training in addition two sample areas in the loess plateau with complex and transitional loess hill and ridge landforms were used to validate the classified landform types by using the proposed dl method meanwhile a comparative analysis between the proposed dl and random forest rf methods was also conducted to investigate their capabilities in landform classification the proposed dl approach can achieve the highest landform classification accuracy of 87 in the transitional area with data combination of dems and images in addition the proposed dl method can achieve a higher accuracy of landform classification with better defined landform boundaries compared to the rf method the classified loess landforms indicate the different landform development stages in this area finally the proposed dl method can be extended to other landform areas for classifying their complex and transitional landforms

lithological mapping of the troodos ophiolite cyprus using airborne lidar topographic data traditional field based lithological mapping can be a time consuming costly and challenging endeavour when large areas need to be investigated where terrain is remote and difficult to access and where the geology is highly variable over short distances consequently rock units are often mapped at coarse scales resulting in lithological maps that have generalised contacts which in many cases are inaccurately located remote sensing data such as aerial photographs and satellite imagery are commonly incorporated into geological mapping programmes to obtain geological information that is best revealed by overhead perspectives however spatial and spectral limitations of the imagery and dense vegetation cover can limit the utility of traditional remote sensing products the advent of airborne light detection and ranging lidar as a remote sensing tool offers the potential to provide a novel solution to these problems because accurate and high resolution topographic data can be acquired in either forested or non forested terrain allowing discrimination of individual rock types that typically have distinct topographic characteristics this study assesses the efficacy of airborne lidar as a tool for detailed lithological mapping in the upper section of the troodos ophiolite cyprus morphometric variables including slope curvature and surface roughness were derived from a 4 m digital terrain model in order to quantify the topographic characteristics of four principal lithologies found in the area an artificial neural network the kohonen self organizing map was then employed to classify the lithological units based upon these variables the algorithm presented here was used to generate a detailed lithological map which defines lithological contacts much more accurately than the best existing geological map in addition a separate map of classification uncertainty highlights potential follow up targets for ground based verification the results of this study demonstrate the significant potential of airborne lidar for lithological discrimination and rapid generation of detailed lithological maps as a contribution to conventional geological mapping programmes

seismic models for near surface explosion yield estimation in alluvium and sedimentary rock author s templeton dc rodgers aj ford sr harben pe ramirez al foxall w reinke re abstract 2018 seismological society of america all rights reserved seismic ground motion data provide valuable constraints on explosion characteristics such as yield and height of burst depth of burial hob dob this study investigated a range of seismic amplitude features and their efficacy in minimizing errors associated with yield estimation using a set of explosion recordings from experiments conducted in alluvium and sedimentary rock geologies we investigated the effectiveness of three different seismic feature types over a range of different frequencies using both velocity and displacement data we investigated the zero to peak ztp amplitude of the first arriving p wave the peak to peak ptp amplitude of the first arriving p wave and the prms amplitude over various time windows starting with the p wave these three basic features were measured on both vertical component only data and the vertical radial vector sum in total there were 56 different combinations investigated our seismic models combine the effects of scaled range and scaled hob dob on the observed seismic features the results show that the vertical radial vector sum of the ztp amplitudes measured on displacement seismograms most consistently produce models with the smallest difference between predicted amplitude values and observed amplitude values when accounting for both alluvium and sedimentary rock lithology the improvement in fit to the data when incorporating the difference in source lithology is significant if an alluvium lithology is assumed for a sedimentary rock lithology the difference in yield could be up to 3 0 times the appropriate yield in the far field

mapping badland areas using landsat tm etm satellite imagery and morphological data abstract soil erosion is the most influential component of land degradation for its strong impacts on both natural and agricultural environments in order to support effective intervention and recovery policies for eroded areas monitoring techniques should take into account the space time variability of the processes involved and make use of assessed mapping methodologies as baseline criteria for studying the dynamics of landform development when using multispectral data for mapping eroded areas low spectral separability is a significant limit in areas with complex features where soil materials are frequently remixed by surface runoff since multispectral satellite images are a valuable data source for multi temporal analyses of erosion processes at the medium scale we assessed how accurately a badland area can be identified from landsat tm and etm data a protocol for an optimal mapping was built up by testing the performance of different supervised algorithms and input layers spectral and morphological tests were carried out in a well known badland area of basilicata italy with an extension of 8000 ha results obtained from the use of spectral bands with and without thermal channel and principal components returned an overall accuracy ranging from 53 for classification on first three components to 72 for classification on all bands from tm with low values for the kappa coefficient 0 30 0 50 showing that the spectral information alone are insufficient to accurately identify badland areas in order to improve mapping we found that the integration of slopes and aspects derived from a digital elevation model dem can overcome problems inherent to the low separability of spectral signatures the use of morphological data was tested for different classification algorithms and integration approaches in discriminating badlands the better performing algorithm was mlc maximum likelihood classifier and the best results were obtained by integrating all seven bands including tir with slope and aspect maps as input within the classifier a 0 85 and k 0 75 for both the sensors we selected such parameters because they play an important role in characterising badlands of study area from a morphological perspective but the proposed approach is also conceptually simple and can be easily exported to other areas the obtained results support the hypothesis that the combined use of remote sensing imagery and auxiliary morphological data significantly improves the mapping of badlands over large areas with heterogeneous features thus providing a useful methodology for long term studies on soil erosion processes

seismo acoustic energy partitioning at near source and local distances from the 2011 sayarim explosions in the negev desert israel the january 2011 calibration explosions at the sayarim military range in the negev desert israel provide a unique dataset to study seismic and acoustic partitioning for surface sources at near source and local distances we present an analysis of the seismic and overpressure acoustic signals generated from two explosions which included 10 240 and 102 080 kg of mainly anfo with some composition b detonated on the surface on 24 and 26 january respectively at different times of the day a temporary seismo acoustic overpressure network was deployed at distances between 0 1 and 39 km to supplement data from permanent stations in israel the near source data confirm the explosions produced overpressure signals consistent with complete and simultaneous surface detonation of 7 4 and 76 8 metric tons of tnt equivalent explosives we observe acoustic amplification at local distances 5 km south of the larger explosion that can be explained by a low altitude southward flowing wind at the detonation time for the smaller shot the southward flow was not present and amplification was not observed in the pressure data we present results of modeling these overpressure data with blast pressure scaling models with and without meteorological data seismic phases generated by the surface shots include p waves fundamental and higher mode rayleigh waves and love waves that appear to have been generated at or very near the explosion source the seismic ground motion is less than would be expected for fully coupled explosions of 7 6 and 76 8 tons and at near source distances 10 km can be modeled well by reducing ground motion predictions from the fuis et al 2001 model by a factor of 4 the results from the sayarim explosions combined with past and future experimental datasets will lead to an improved understanding of the seismo acoustic source function for explosions and energy partitioning between seismic and acoustic waves

quartz concentration as an index of sediment mixing hydraulic mine tailings in the sierra nevada california abstract hydraulic gold mining delivered large volumes of sediment to northern california stream channels from 1853 to 1884 distinctive quartz compositions of this sediment allow development of a sediment mixing index for determination of tailings concentrations in contemporaneous and reworked deposits this index reveals patterns of sediment mixing in the bear river california over the last 100 years a conceptual model summarizes the nature of sediment mixing in the bear river basin through time and space high terrace sediment compositions suggest that hydraulic mining sediment was diluted by about 22 other alluvium as it moved more than 60 km to the sacramento valley this substantial volume of other alluvium was introduced during the mining period by human activities in addition to hydraulic mining sediment compositions in modern low flow channels indicate that most channel reaches within the mining districts remain dominated by tailings due to sustained reworking of stored alluvium tailings are substantially diluted downstream in modern channel deposits however due to trapping of sediment by dams and local erosion of quarternary alluvium

stochastic model for the long term transport of stored sediment in a river channel we develop a stochastic model for the transport of stored sediment down a river channel the model is based on probabilities of transition of particles among four different sediment storage reservoirs called active often mobilized semiactive inactive and stable hardly ever mobilized the probabilities are derived from computed sediment residence times two aspects of sediment storage are investigated flushing times of sediment out of a storage reservoir and changes in the quantity of sediment stored in different reservoirs due to seasonal sediment transport into and out of a reach we apply the model to redwood creek a gravel bed river in northern california although the redwood creek data set is incomplete the application serves as an example of the sorts of analyses that can be done with the method the application also provides insights into the sediment storage process sediment flushing times are highly dependent on the degree of interaction of the stable reservoir with the more mobile sediment reservoirs the most infrequent and highest intensity storm events which mobilize the stable reservoir are responsible for the long term shifts in sediment storage turnover times of channel sediment in all but the stable reservoir are on the order of 750 years suggesting this is all the time needed for thorough interchange between these sediment compartments and cycling of most sediment particles from the initial reservoir to the ocean finally the markov model has adequately characterized sediment storage changes in redwood creek for 1947 1982 especially for the active reservoir the model replicates field observation of the passage of a slug of sediment through the active reservoir of the middle reach of redwood creek in the 18 years following a major storm in 1964 that introduced large quantities of landslide debris to the channel

empirical dependence of seismic ground velocity on the weight of explosives shotpoint site condition and recording distance for seismic refraction data in this study we have constructed an empirical least squares model for maximum seismic ground velocity vertical component as a function of source size and distance from explosions in drillholes and bodies of water this model is intended in part for use in designing explosion seismic experiments in order to produce acceptable signal to noise ratios at larger distances 10 km and to avoid damaging human structures at smaller distances 1 km data consist of velocities recorded by 120 portable seismographs from 159 shots fired by the u s geological survey in alaska and arizona results show that maximum ground velocity amplitude not necessarily first arrival amplitude decreases with distance and the functional dependence changes with distance for example at 3 km amplitudes decrease as r 2 but at 73 km they decrease as r 1 results also show a strong dependence on site conditions at the shotpoint for example a drillhole shot in wet alluvium produces amplitudes that are four times larger than a drillhole shot in dry alluvium ground velocities are proportional to the square root of the weight of explosives

residence time of alluvium in an aggrading fluvial system relationships between the surface area and age of alluvial deposits were used to estimate the residence time of alluvium in the 2205 km2 waipaoa river basin new zealand the contemporary waipaoa river is an efficient transporter of sediment to the continental shelf but the basin has been characterized by rapid channel and valley aggradation in the historic period and by extensive mid to late holocene alluvial storage in the lower reaches the area weighted mean age of alluvial deposits in the lower part of the river basin is 4400 yr these deposits comprise terrace remnants isolated by downcutting and holocene to recent sediments that are potentially remobilizable by the modern river even though the amount of storage is small relative to downstream transport the majority of the potentially remobilizable alluvium is likely to remain in storage for 100 yr and its half life time for 50 per cent removal is 2000 yr within the confines of the flfloodplain the apparent loss of older deposits is due primarily to burial but losses of the most recent deposits are due almost entirely to remobilization 30 40 per cent with the remainder preserved in the alluvial record for at least 104 yr most of this sediment is likely to remain in storage until there is a shift to a degradational state copyright 2006 john wiley sons ltd

geomorphometric analysis for characterizing landforms in morelos state mexico landforms can be described and quantified into simple relief elements by parametrization of digital elevation model dem in this research we investigate the use of morphometric parameters and a new classification scheme to characterize selected elemental forms associated with landforms we apply and test this methodology on a geomorphologically diverse region located in central mexico these simple elements are known as morphometric classes and include ridge plane channel pit peak and pass these classes correspond to real entities and are of practical significance the morphometric classes were grouped according to their areal parameters ridge plane and channel and pointed parameters pit peak and pass which can be used to form the basis of a system of characterization and classification of landforms landform elements display statistically significant compositional differences with respect to their proportions of morphometric classes this in turn can be plotted onto a diagram of characterization and classification known as a double ternary diagram dtd which comprises both areal and pointed parameters and any combination thereof the dtd is useful for studying geomorphological processes wherein areal and point values and properties have expressions which are topographically quantifiable

seismic phases and scaling associated with small high explosive surface shots abstract an analysis of seismic field data from surface shots in two radically different geologic environments shows significantly different seismic phases at the two sites at the first site which has a layered sedimentary section five distinct phases are observed the p wave first arrival a complex wave train consisting of higher mode rayleigh waves a precursor to air blast wave the air blast wave and the air coupled rayleigh waves records from the second site overlying an unlayered mass of igneous rocks show only three distinct seismic phases the p wave first arrival a simple wave train of fundamental mode rayleigh and love waves and an air blast wave peak ground velocity based on the average of the three largest amplitudes in the surface waves preceding the air blast wave scales well with yield for both sites measurements of peak ground velocity may be used to estimate yields of explosive charges at either site within a factor of about 2 if the source distance is known the scaling relationship appears to be valid over a wide range of yields and site geological conditions

thermoluminescence and excess 226ra decay dating of late quaternary fluvial sands east alligator river australia thermoluminescence tl dating was applied to seven samples of siliceous fluvial sands from the east alligator river of northern australia giving ages ranging from modern to 6000 yr b p two methods of estimating the equivalent dose ed total bleach and regenerative were applied to the 90 to 125 m quartz fraction of the samples in order to determine the reliability and internal consistency of the technique high resolution and spectroscopy were used to measure radionuclide contents these measurements revealed an excess 226ra activity compared with 230th this excess decreased with depth and was used directly to derive mean sedimentation rates and thus sediment ages both this method and one 14c date confirmed the validity of the tl values which increased systematically with depth and were consistent with site stratigraphy tl was of limited use in the dating of these late holocene deposits because of age uncertainties of 500 to 1600 yr resulting from a significant residual ed this residual probably resulted from incomplete bleaching during reworking upstream of the sampling site for pleistocene deposits the residual ed will be less significant because of higher total eds and tl dates will be correspondingly more accurate

planation bauxites and epeirogeny one or two paleosurfaces on the west african margin mapping of lateritic bauxites over the west african rifted margin and analysis of the geomorphic properties of these bauxites combined with available geological data lead to a discussion of the presence of either two meso cenozoic planation surfaces or a single eocene surface to account for the morphotectonic and paleoclimatic evolution of the guinean landforms at large scale two stepped bauxitic levels are documented ongoing or episodic uplift following gondwana breakup and meso cenozoic climate change are proposed to have allowed the formation and abandonment of an early mid cretaceous surface today preserved as the higher bauxitic level and the setting of an eocene planation surface bearing a second generation of bauxites making the lower bauxitic level the single eocene surface hypothesis requires that paleogene bauxitization preserved large pre existing relief to explain two stepped bauxitic levels of the same age the two surface hypothesis is favored because it would explain rebauxitization of alluvial pebbles of bauxites under the lower lateritic level

radiometric ages of laterites and constraints on long term denudation rates in west africa in stable cratonic regions most tropical weathering mantles evolve over long time scales and record long term environmental change they may therefore also reflect tectonism and its denudation related signals detected through apatite fission track thermochronology cosmogenic radionuclide dating and the age bracketing of laterites by 4 0 ar 3 9 ar dating of potassium and manganese rich oxides based on an existing cenozoic pedimentation model for the west african craton this study uses the three combined radiometric methods to define rates of cenozoic denudation denudation rates of 2 m m y on the lateritic plateaus in comparison to rates of 7 13 m m y adjacent to them fit ages of 45 50 ma for late stages of bauxite development and 24 25 ma for one phase of lateritization together they support the theory implicit in the landscape model that depths of denudation in cratonic interiors are equal to or not significantly greater than existing elevation differences between lateritic landforms

luminescence and radiocarbon chronologies of playa sedimentation in the murray basin southeastern australia abstract playa lakes are important palaeoenvironmental repositories in arid landscapes as geochemically open and organically poor systems however accurate dating of playa sequences is often hampered this study paired accelerator mass spectrometry radiocarbon ams 14c and optically stimulated luminescence osl ages from four murray basin playa lakes to assess the accuracy of the chronometric techniques in these environments the osl dating directed the sampling strategy which targeted sandier sections of the playa lacustrine sequences these appear to comprise aeolian derived fine quartzose sand ensuring the effective resetting of the luminescence signals prior to deposition in contrast the 14c ages were on bulk organic carbon and not targeted ages are generally in stratigraphic order and span the middle late last glacial and holocene this accords with models of past groundwater hydrology for the playa basins only half of the paired samples are in agreement at 2 precision however with five of the 14c ages older than their corresponding osl ages low organic contents of playa sediments increases the susceptibility of 14c ages to contamination with the incorporation of small amounts of dead carbon into the dated samples possibly accounting for the apparent discrepancies obtaining valid chronologies from arid settings requires close targeting of dated fractions the application of independent techniques is essential for scrutinizing the dating results

automated classification of landform elements using object based image analysis this paper presents an automated classification system of landform elements based on object oriented image analysis first several data layers are produced from digital terrain models dtm elevation profile curvature plan curvature and slope gradient second relatively homogenous objects are delineated at several levels through image segmentation these object primatives are classified as landform elements using a relative classification model built both on the surface shape and on the altitudinal position of objects so far slope aspect was not used in classification the classification has nine classes peaks and toe slopes defined by the altitudinal position or the degree of dominance steep slopes and flat gentle slopes defined by slope gradients shoulders and negative contacts defined by profile curvatures head slopes side slopes and nose slopes defined by plan curvatures classes are defined using flexible fuzzy membership functions results are visually analyzed by draping them over dtms specific fuzzy classification options were used to obtain an assessment of output accuracy two implementations of the methodology are compared using 1 romanian datasets and 2 berchtesgaden national park germany the methodology has proven to be reproducible readily adaptable for diverse landscapes and datasets and useful in respect to providing additional information for geomorphological and landscape studies a major advantage of this new methodology is its transferability given that it uses only relative values and relative positions to neighboring objects the methodology introduced in this paper can be used for almost any application where relationships between topographic features and other components of landscapes are to be assessed

very long term incision dynamics of big rivers constraining large scale incision dynamics of shield and post rift margin domains is key to understanding the sediment routing system over the overwhelming part of the continental surface based on dated and regionally correlated incision markers from west africa we reconstruct for the first time the entire paleo long profiles of big rivers such as the niger at ca 24 11 and 6 ma as well as the eocene topography those rivers have dissected the results provide boundary conditions and calibration for surface process models and paleodrainage dynamics though spatially and temporally variable incision remained mostly below 10 m my with a mean around 5 m my the spatial stability of both the river outlets and divides imposed maintenance or increasing concavity of the river long profiles through time resulting from spatially contrasted adjustment of river segments bounded by recurrent lithogenic knickzones that persisted since 24 ma drainages evolved preferentially by very slow slope decrease or uniform incision in between the stationary knickzones of evolving amplitude with apparently no relation to base level change therefore knickzone height or position may not simply reflect the transient response of big rivers to base level fall as predicted by stream power incision river models this may also challenge uplift histories of deep continental interiors retrieved from river long profiles inversion relying on such models very slow incision allowed amplification of the hoggar hot spot swell and flexural uplift of the continental margin to be recorded by river long profiles emphasizing the potential of big non orogenic rivers as gauges of dynamic topography

a regolith depth map of the australian continent abstract the regolith is defined as weathered in situ and transported material overlying unweathered bedrock as fresh bedrock exposures form a small proportion of the landscape regolith is common in australia and varies in depth from less than a metre in upland settings to many hundreds of metres e g the cenozoic basins because of crucial fluxes in gases water nutrients and dissolved salts and variation in permeability and connectivity knowledge of the nature and depth of regolith is important to many land based industries including agriculture and forestry the minerals industry sees regolith as a barrier to discovery of mineralised rock at depth or as a host of minerals in economic concentrations there are clearly a range of important characteristics of regolith depth and therefore the quantity of regolith is fundamental for resource inventory and biophysical modelling applications a method is described that maps the depth of regolith with estimates of mapping uncertainty to the moderately weathered saprock boundary for the whole of australia our approach draws on an extensive legacy of publically available drillhole data of variable attribute consistency and applies an environmental correlation style of digital mapping prediction that utilises relevant spatial covariates e g terrain analysis climate and gamma radiometric datasets from the original database of 350 000 records we filtered and harmonised a useable dataset of 128 000 records key predictive datasets used in the depth model included weathering intensity lithology age distance to out crop elevation and relief shallowest cover corresponded to high relief erosional landscapes and deepest corresponded to cenozoic basin sediments the final map with a ground resolution of approximately 90 m 3 arcsec was generated using 100 bootstrap model iterations the reliability of the model was assessed using measures of r square 0 38 lin s concordance 0 51 mean error 5 73 m and root mean squared error 24 56 m calculated on a withheld test dataset the regolith depth map is consistent with known areas of deep in situ weathering and accumulation of recent sediment associated with the distribution of cenozoic basins and provides a testable estimate in areas with little drilling or survey history the predictive modelling approach provides a framework to further build and improve regolith depth prediction across varying spatial scales where sufficient quality drillhole data and environmental predictors exist and set priorities for new data acquisition

geomorphometric feature analysis using morphometric parameterization and artificial neural networks this paper presents a semi automatic method using an unsupervised neural network to analyze geomorphometric features as landform elements the shuttle radar topography mission srtm provided detai

bosumtwi impact structure ghana evidence for fluidized emplacement of the ejecta the about 10 5 km diameter bosumtwi impact crater is one of the youngest large impact structures on earth the crater rim is readily noticed on topographic maps or in satellite imagery it defines a circular basin filled by water lake bosumtwi and lacustrine sediments the morphology of this impact structure is also characterized by a circular plateau extending beyond the rim and up to 9 10 km from the center of the crater about 2 crater radii this feature comprises a shallow ring depression also described as an annular moat and a subdued circular ridge at its outer edge the origin of this outermost feature could so far not be elucidated based on remote sensing data only our approach combines detailed topographic analysis including roughness mapping with airborne radiometric surveys mapping near surface k th u concentrations and field observations this provides evidence that the moat and outer ring are features inherited from the impact event and represent the partially eroded ejecta layer of the bosumtwi impact structure the characteristics of the outer ridge indicate that ejecta emplacement was not purely ballistic but requires ejecta fluidization and surface flow the setting of bosumtwi ejecta can therefore be considered as a terrestrial analog for rampart craters which are common on mars and venus and also found on icy bodies of the outer solar system e g ganymede europa dione tethys and charon future studies at bosumtwi may therefore help to elucidate the mechanism of formation of rampart craters

yield and emplacement depth effects on acoustic signals from buried explosions in hard rockyield and emplacement depth effects on acoustic signals from buried explosions in hard rock

uranium series chronology and environmental applications of speleothems an increasing number of scientists recognize the value of speleothems1 as often extremely well preserved archives of information about past climate vegetation hydrology sea level nuclide migration water rock interaction landscape evolution tectonics and human action well constrained data are required to document past changes reconstruct past patterns and predict future responses of the earth system at a wide range of spatial and temporal scales speleothems are particularly useful in this regard because they can be found in many locations of the globe sampled at high resolution and reliably dated using high precision uranium series techniques speleothems are bodies of mineral material formed in caves as the result of chemical precipitation from groundwater flowing or dripping in a cave most speleothems are composed of calcite formed by slow degassing of co2 from supersaturated groundwater but aragonite and gypsum forms are also common particularly near cave entrances where evaporative effects are important a host of different speleothem types decorate the walls ceilings and floors of caves and their mineralogy and morphology is a function of fluid flow and chemistry of waters feeding a particular location as well as the ambient conditions temperature chemistry light in the air or water filled void subaerial forms include the familiar stalagmites stalactites draperies flowstones subaqueous forms include rimstone pools rafts mammillary calcite wall coatings and dog tooth spar for an extensive review of the types of speleothem that have been observed see hill and forti 1997 speleothems are used in a multitude of ways to explore past environmental conditions perhaps the most fundamental of which is their very presence or absence deposition of speleothems relies on sufficient water supply and soil co2 to enable dissolution and transport of reactants in the vadose zone to underlying caves in arid or glacial times conditions may not have been favorable for speleothem formation

integrating airborne multispectral imagery and airborne lidar data for enhanced lithological mapping in vegetated terrain practical and financial constraints associated with traditional field based lithological mapping are often responsible for the generation of maps with insufficient detail and inaccurately located contacts in arid areas with well exposed rocks and soils high resolution multi and hyperspectral imagery is a valuable mapping aid as lithological units can be readily discriminated and mapped by automatically matching image pixel spectra to a set of reference spectra however the use of spectral imagery in all but the most barren terrain is problematic because just small amounts of vegetation cover can obscure or mask the spectra of underlying geological substrates the use of ancillary information may help to improve lithological discrimination especially where geobotanical relationships are absent or where distinct lithologies exhibit inherent spectral similarity this study assesses the efficacy of airborne multispectral imagery for detailed lithological mapping in a vegetated section of the troodos ophiolite cyprus and investigates whether the mapping performance can be enhanced through the integration of lidar derived topographic data in each case a number of algorithms involving different combinations of input variables and classification routine were employed to maximise the mapping performance despite the potential problems posed by vegetation cover geobotanical associations aided the generation of a lithological map with a satisfactory overall accuracy of 65 5 and kappa of 0 54 using only spectral information moreover owing to the correlation between topography and lithology in the study area the integration of lidar derived topographic variables led to significant improvements of up to 22 5 in the overall mapping accuracy compared to spectral only approaches the improvements were found to be considerably greater for algorithms involving classification with an artificial neural network the kohonen self organizing map than the parametric maximum likelihood classifier the results of this study demonstrate the enhanced capability of data integration for detailed lithological mapping in areas where spectral discrimination is complicated by the presence of vegetation or inherent spectral similarities

geomorphological mapping with a small unmanned aircraft system suas feature detection and accuracy assessment of a photogrammetrically derived digital terrain model abstract small unmanned aircraft systems suas are a relatively new type of aerial platform for acquiring high resolution remote sensing measurements of earth surface processes and landforms however despite growing application there has been little quantitative assessment of suas performance here we present results from a field experiment designed to evaluate the accuracy of a photogrammetrically derived digital terrain model dtm developed from imagery acquired with a low cost digital camera onboard an suas we also show the utility of the high resolution 0 1 m suas imagery for resolving small scale biogeomorphic features the experiment was conducted in an area with active and stabilized aeolian landforms in the southern canadian prairies images were acquired with a hawkeye rq 84z areohawk fixed wing suas a total of 280 images were acquired along 14 flight lines covering an area of 1 95 km2 the survey was completed in 4 5 h including gps surveying suas setup and flight time standard image processing and photogrammetric techniques were used to produce a 1 m resolution dtm and a 0 1 m resolution orthorectified image mosaic the latter revealed previously un mapped bioturbation features the vertical accuracy of the dtm was evaluated with 99 real time kinematic gps points while 20 of these points were used to quantify horizontal accuracy the horizontal root mean squared error rmse of the orthoimage was 0 18 m while the vertical rmse of the dtm was 0 29 m which is equivalent to the rmse of a bare earth lidar dtm for the same site the combined error from both datasets was used to define a threshold of the minimum elevation difference that could be reliably attributed to erosion or deposition in the seven years separating the suas and lidar datasets overall our results suggest that suas acquired imagery may provide a low cost rapid and flexible alternative to airborne lidar for geomorphological mapping

multiple influences on regolith characteristics from continental scale geophysical and mineralogical remote sensing data using self organizing maps we investigate the characteristics of regolith through the application of statistical learning to diverse layers of terrestrial continental scale remote sensing data this combination allows us to explore the multiple influences of bedrock climate biota landscape and time on regolith development and properties an interdisciplinary geoscience modeling problem from a wide variety of available data for australia we select remotely sensed geophysical geomorphological and mineralogical inputs with good spatial coverage we use self organizing maps som a topologically constrained unsupervised statistical learning algorithm to characterize the geophysical and mineralogical signatures of regolith and bedrock regolith materials cover more than 80 of the australian continent range in age from precambrian to quaternary and vary in thickness from less than a meter to more than a kilometer the diversity of regolith cover type and character across australia provides an opportunity to demonstrate knowledge discovery from remote sensing data the outputs of our som analysis are combined with ground observations from locations showing naturally occurring anomalous concentrations of nickel tin and uranium we identify a minimum number of natural clusters indicating subtle but significant differences in regolith and bedrock mineralization characteristics our results show that som identifies spatially contiguous regions representing unique regolith and bedrock materials in the yilgarn craton we observe key differences in landscape character density of the crust and relative abundance of radioactive elements and alumino silicate and ferric oxide minerals these properties discriminate between nickel prospective residual deeply weathered regolith formed on mafic and or ultramafic bedrock and uranium prospective cainozoic paleochannels containing felsic bedrock source materials national scale data are publicly available for many continental regions as in the australian example and our approach has general applicability we demonstrate that remote sensing data may be used to understand the regolith revealing the interplay between environmental history and bedrock character at regional scales and differences between residual and transported regolith provenance of source materials and their relative ages

residence times of alluvium in an east texas stream as indicated by sediment color abstract the relationships between sediment production storage and transport in fluvial systems are complex and variable key issues in addressing these relationships are the residence times of sediment delivered to the channel and the proportion derived from recent upland erosion as opposed to remobilized alluvium the systematic changes in iron geochemistry often experienced by sediments deposited in an anaerobic environment such as a stream channel or waterlogged floodplain are used here as an indicator of residence time over contemporary time scales in areas such as east texas where upland soils are high in iron oxide content these changes are reflected in soil color alluvium with red yellow or brown colors indicating ferric oxidized iron and sufficient organic matter for reduction to occur indicates a short 1 year sediments with the longest residence times in alluvial environments 1 year will not oxidize on exposure to the atmosphere due to the loss of iron while those with ferrous iron remaining will experience oxidation and color change on exposure in loco bayou texas these indicators of residence time are shown to be generally consistent with other field evidence of erosion and sedimentation further the color indicators correctly indicate the residence time in several cases where the latter is known from field observations

neogene cratonic erosion fluxes and landform evolution processes from regional regolith mapping burkina faso west africa the regionally correlated and dated regolith paleolandform sequence of sub saharan west africa offers a unique opportunity to constrain continental scale regolith dynamics as the key part of the sediment routing system in this study a regolith mapping protocol is developed and applied at the scale of southwestern burkina faso mapping combines field survey and remote sensing data to reconstruct the topography of the last pediplain that formed over west africa in the early and mid miocene 24 11 ma the nature and preservation pattern of the pediplain are controlled by the spatial variation of bedrock lithology and are partitioned among large drainage basins quantification of pediplain dissection and drainage growth allows definition of a cratonic background denudation rate of 2 m my and a minimum characteristic timescale of 20 ma for shield resurfacing these results may be used to simulate minimum export fluxes of drainage basins of constrained size over geological timescales background cratonic denudation results in a clastic export flux of 4 t km 2 year which is limited by low denudation efficiency of slope processes and correlatively high regolith storage capacity of tropical shields these salient characteristics of shields surface dynamics would tend to smooth the riverine export fluxes of shields through geological time

geomorphological signatures classification of aggregated slope unit objects from digital elevation and remote sensing data the concept of a geomorphological signature is developed for classifying and mapping slope units with an automated procedure for analysing digital elevation and remote sensing data slope units are extracted from a digital elevation model dem using a break of slope rule on downslope profiles each slope unit is an aggregated object of contiguous pixels and is summarized with five suites of variables shape topography topographic variability spectral characteristics and variability in spectral characteristics the variables are derived from the dem and a corresponding spot satellite image a ten class scheme is used to classify slope units for a study area in southwest yukon canada discriminant analysis results show the power of various combinations of variables to distinguish the classes with a maximum classification accuracy of 90 per cent training signatures are employed for classifying the entire study area to produce a map with 88 5 per cent accuracy the study shows that generating extensive geomorphological signatures for aggregated slope unit objects is a valuable exercise for discrimination and mapping 1998 john wiley sons ltd

sources of alluvium in a coastal plain stream based on radionuclide signatures from the 238u and 232th decay series ratios 226 ra 232 th 226 ra 230 th and 230 th 232 th channel alluvium indicates a transition from interfluve surface to subsoil sources during flood subsoil 34 to 91 over about 8 km and bank full stages subsoil 9 to 74 over about 12 km with distance downstream these results indicate strong coupling between hillslope and channel processes reflecting land use change from forested to agricultural concentrated in lower loco bayou this methodology shows that sediment sources can be differentiated based upon landscape placement where lithologic contrast is absent the geochemistry long halflives and fractionation of 238 u and 232 th decay series radionuclides during pedogenic and fluvial processes in humid climates suggest that these methods are applicable in a wide variety of fluvial systems index terms 1040 geochemistry isotopic composition chemistry 1803 hydrology anthropogenic effects 1815 hydrology erosion and sedimentation 1824 hydrology geomorphology 1625 keywords natural radionuclides fingerprinting alluvium source apportioning

automated regolith landform mapping using airborne geophysics and remote sensing data burkina faso west africa abstract we have studied the regolith landform distribution in the area of gaoua western burkina faso using an integration of geophysical and remote sensing data concentration maps of k th u as well as their ratios were computed from airborne gamma ray spectrometry data to assess the geochemical composition of the regolith the mineralogy of the surfaces was mapped via the analysis of multispectral aster and landsat scenes pauli decomposition data retrieved from polarimetric alos palsar and radarsat 2 images were included to characterize the surface properties of the regolith material morphometric variables such as slope curvature and relative relief were derived from the srtm digital elevation model to quantify the topographic parameters of the different regolith landforms an artificial neural network implementation advangeo was then employed to extract four basic regolith landform units from the satellite and airborne data relic ferruginous duricrusts rich in hematite and goethite belonging to the high glacis erosional surfaces represented by rock outcrops and suboutcrops alluvial sediments and soft pediment materials of the middle and low glacis were mapped successfully in the region the results were compared with the existing geomorphological maps an independent visual classification and field observations we found that the distribution and shape of the iron rich duricrusts are more accurate than portrayed in the current maps the best results with an overall accuracy of 94 21 and a kappa value of 0 92 were obtained for a dataset consisting of gamma ray spectrometry data combined with derivatives of the srtm digital elevation model augmented by landsat and polarimetric radar data the approach demonstrates for the first time the potential of machine learning in regolith landform mapping the proposed combined analysis of airborne geophysics and remote sensing data can be adopted easily in other regions with similar long term lateritic weathering histories worldwide

combining digital elevation data srtm aster high resolution satellite imagery quickbird and gis for geomorphological mapping a multi component case study on mediterranean karst in central crete abstract remote sensing data have become more and more popular for geomorphological investigations because their steadily increasing level of detail and accessibility opens up new potentials in this context this paper examines the application and quality of digital elevation models srtm and aster dems high resolution satellite imagery quickbird and gis techniques for the detection and mapping of karst landforms mainly enclosed depressions at different scales in the ida mountains of central crete besides discussing methodological issues and evaluating suitability potentials we conducted an exemplary case study based on spatial analysis of the regional karst morphology different input datasets and processing methods are applied gis based analysis land cover classification raster calculations etc in order to carry out an area wide surveying and mapping of karst depressions the findings are supported and validated by auxiliary field studies due to the level of detail and occasional data errors an exclusive use of satellite imagery or digital elevation models for automatic karst landform detection performs insufficiently our results demonstrate that mapping karst features through remote sensing is significantly dependent on scale of interest existing environmental conditions and data quality a semi automatic data integration approach on the basis of digital datasets generated by combined satellite image processing and dem analysis yields the best results especially when indirect karst indicating variables like iron oxide rich sediments are included as detection criteria the multi component application presented in this paper provides a time saving and effective tool for meso to macro scale object detection and extensive study areas however the potential of fully automated karst feature mapping still needs to be explored in future work concerning the spatial dimension of karstification in central crete the gis based results allow differentiating further geomorphological characteristics e g by indicating a significant altitudinal change of karst forms within the study area size and shape of depressions dolines uvalas and poljes vary considerably due to the geological setting climatic impacts neotectonics and elevation

uranium series isotopes in river materials insights into the timescales of erosion and sediment transport abstract the uranium series isotope signatures of the suspended and dissolved load of rivers have emerged as an important tool for understanding the processes of erosion and chemical weathering at the scale of a watershed these signatures are a function of both time and weathering induced fractionation between the different nuclides provided appropriate models can be developed they can be used to constrain the residence time of river sediment this chronometer is triggered as the bedrock starts weathering and the inferred timescale encompasses the residence time in the weathering profile storage in temporary sediment deposits e g floodplain and transport in the river this approach has been applied to various catchments over the past five years showing that river sediments can reside in a watershed for timescales ranging from a few hundreds of years iceland to several hundreds of thousands of years lowlands of the amazon various factors control how long sediment resides in the watershed the longest residence times are observed on stable cratons unaffected by glacial cycles or more generally climate variability and human disturbance shorter residence times are observed in active orogens andes or fast eroding recently glaciated catchments iceland in several cases the residence time of suspended sediments also corresponds to the time since the last major climate change the u series isotope composition of rivers can also be used to predict the river sediment yield assuming steady state erosion is reached by comparing this estimate with the modern sediment yield obtained by multi year sediment gauging it is clear that steady state is seldom reached this can be explained by climate variability and or human disturbance steady state is reached in those catchments where sediment transport is rapid iceland or where the region has been unaffected by climate change and or human disturbance u series are thus becoming an important tool to study the dynamics of erosion

seismic and infrasonic eruption tremors and their relation to magma discharge rate a case study for sub plinian events in the 2011 eruption of shinmoe dake japan

disequilibrium of holocene sediment yield in glaciated british columbia it is generally supposed that specific sediment yield the quantity of sediment passing a monitored river cross section per unit area drained upstream of that section declines as the area drained increases1 3 part of the sediment mobilized from the land surface is supposed to go back into storage at field edges and on footslopes and floodplains in contrast we show here that data from british columbian rivers reveal a pattern of increasing specific sediment yield at all spatial scales up to 3 104 km2 this results from the dominance of secondary remobilization of quaternary sediments along river valleys over primary denudation of the land surface the result controverts the conventional model which has been derived from studies of small highly disturbed agricultural catch ments the rivers are still responding to the last glaciation giving a landscape relaxation time greater than 10 kyr this holds pro found implications for geomorphological theory and for studies of erosion

an analysis of the effects of site geology on the characteristics of near field rayleigh waves abstract an approximate analytical model is presented for describing the effects of site geology on the near field rayleigh wave ground motions induced by atmospheric explosions the model is based on an airy phase approximation to the time domain displacement corresponding to the exact frequency domain solution results of numerical simulations are presented which indicate that the amplitude duration and dominant frequency of the rayleigh wave ground motions are strongly dependent on the variation of shear wave velocity with depth at the site the approximate model is tested over a range of site conditions and it is demonstrated that the dependence of the rayleigh wave characteristics on site geology predicted by the more complex exact model can be accurately described by a remarkably simple set of analytic approximations