historical development of the gravity method in exploration the gravity method was the first geophysical technique to be used in oil and gas exploration despite being eclipsed by seismology it has continued to be an important and sometimes crucial constraint in a number of exploration areas in oil exploration the gravity method is particularly applicable in salt provinces overthrust and foothills belts underexplored basins and targets of interest that underlie high velocity zones the gravity method is used frequently in mining applications to map subsurface geology and to directly calculate ore reserves for some massive sulfide orebodies there is also a modest increase in the use of gravity techniques in specialized investigations for shallow targets gravimeters have undergone continuous improvement during the past 25 years particularly in their ability to function in a dynamic environment this and the advent of

linking soil element mass transfer to microscale mineral weathering across a semiarid environmental gradient abstract understanding controls on silicate weathering is critical to characterizing critical zone evolution the objective of this study was to investigate how climate vegetation and landscape position control feldspar transformations across a semiarid environmental gradient granitic surface soil and saprock samples were collected from desert scrub and mixed conifer sites within the santa catalina mountain critical zone observatory where mean annual temperature ranges from 24 c to 10 c and mean annual precipitation from 25 to 85 cm quantitative x ray diffraction x ray fluorescence and electron microprobe analyses were employed to quantify elemental changes in bulk soils and across plagioclase grains the chemical depletion of na in bulk soils ranged from 5 4 15 in the desert scrub sites relative to 16 33 in the mixed conifer sites plagioclase grain alteration was classified into unaltered edge and altered sections to compare microscale weathering and elemental variation the na al and si al ratios decreased from unaltered to edge to altered grain sections in the mixed conifer sites whereas the element ratios of the desert scrub system were similar between unaltered and edge grain sections and only exhibited significant decreases in na al and si al ratios between edge and altered materials the microscale depletion of na and si suggested increased silicate weathering in the cooler wetter and more biologically productive mixed conifer system compared to the hot dry desert scrub system the results also demonstrated a topographic control on mineral transformation where increased plagioclase weathering occurred in convergent footslope landscapes with little change in elemental depletion of soils in divergent summit sites

unravelling the development of a spheroidally weathered diorite gabbro santa margarita ecological reserve peninsular ranges southern california usa abstract within santa margarita ecological reserve smer southern california an 108 ma diorite gabbro pluton has weathered spheroidally resulting in the formation of concentric rindlets i e a rindlet zone around an unaltered ellipsoidal core of the parent rock to our knowledge little is known about how spheroidal weathering is produced in mediterranean climates like that characteristic of portions of the peninsular ranges hence we undertook a detailed study aimed at determining the textural and chemical changes associated with the spheroidal weathering of the diorite gabbro pluton the parental spheroidally weathered corestone is characterized by a hypidomorphic granular texture and consists primarily of plagioclase amphibole and biotite along with minor amounts of pyroxene and quartz within the corestone sericite and uncommonly calcite and chlorite replace plagioclase the latter mineral also infrequently replaces portions of amphibole and biotite such alteration products are derived from sub solidus deuteric alteration of the pluton xrd clay mineral analysis of the 13 rindlets indicates the presence of mostly kaolinite and vermiculite and a far lesser volume of green smectite thin section study of rindlet samples suggests that vermiculite is derived from the weathering of biotite the most extensively altered mineral in the rindlet zone such alteration is paralleled by statistically significant losses of k mass across the rindlet zone in addition statistically significant losses of ca and na mass across the rindlet zone likely reflect conversion of sericite to kaolinite in contrast the absence of statistically significant losses of mg fe and mn over most of the rindlet zone implies that fluids were mostly oxidizing and that any mg leached from amphibole was likely fixed within smectite while leached fe and mn precipitated out as oxides or oxyhydroxides though calcite was present in the corestone its absence in the rindlets indicates that fluids were sufficiently acidic to dissolve and remove it previous studies have shown that spheroidal weathering occurs when volume expansion produced by a positive v of reaction builds up internal elastic strain energy in the rock for example this type of reaction occurs when iron oxidizes within biotite resulting in an expansion of d 001 from 10 a to 10 5 a or when biotite is transformed into vermiculite leading to an expansion of d 001 from 10 a to 14 a data presented here suggest that the conversion of biotite to vermiculite and the resulting positive v produced the spheroidal fracturing of the corestone at smer hence these and other data discussed in this paper suggest that the weathering of biotite is the primary driving force in the formation of spheroidally weathered corestone in the mediterranean climate of the peninsular ranges

the atmospheric transport of iodine 129 from fukushima to british columbia canada and its deposition and transport into groundwater the fukushima daiichi nuclear accident fdna released iodine 129 15 7 million year half life and other fission product radionuclides into the environment in the spring and summer of 2011 129i is recognized as a useful tracer for the short lived radiohazard 131i which has a mobile geochemical behavior with potential to contaminate water resources to trace 129i released by the fdna reaching canada pre accident and post accident rain samples collected in vancouver on saturna island and from the national atmospheric deposition program in washington state were measured groundwater from the abbotsford sumas aquifer was sampled to determine the fate of 129i that infiltrates below the root zone modeling of vadose zone transport was performed to constrain the travel time and retardation of 129i the mean pre accident 129i concentration in rain was 31 106 atoms l n 4 immediately following the fdna 129i values increased to 211 106 atoms l and quickly returned to near background levels however pulses of elevated 129i continued for several months the increases in 129i concentrations from both vancouver and saturna island were synchronized and occurred directly after the initial release from the fdna the 129i in shallow 3h 3he age 1 4 years wassenaar et al 2006 groundwater showed measurable variability through march 2013 with an average of 3 2 106 atoms l n 32 that was coincident with modeled travel times for fukushima 129i the groundwater response and the modeling results suggest that 129i was partially attenuated in soil which is consistent with its geochemical behavior however we conclude that the measured variability may be due to fukushima 129i entering groundwater

multidisciplinary study of holocene archaeological soils in an upland mediterranean site natural versus anthropogenic environmental changes at cecita lake calabria italy abstract this paper highlights results of a multidisciplinary and multi analytical study of holocene archaeological soils around cecita lake sila massif calabria southern italy which represents a typical upland mediterranean environment it is focused on assessment of climatic and environmental changes that took place since late neolithic to roman times trying to discriminate natural from anthropogenic signals based on an integration of archaeological geomorphological stratigraphic pedological volcanological and soil charcoal pedoanthracological data the following paleoclimatic environmental reconstruction is proposed a warm and humid seasonally contrasted climate with an overall geomorphological stability suited for soil development characterized the late prehistoric environment holocene climatic optimum dominated by a widespread oak forest the main pedogenetic processes consisted in organic matter accumulation clay illuviation phyllosilicate and short range order mineral neogenesis from weathering of granite and volcanic ash sourced from late pleistocene holocene eruptions of the aeolian islands one or more mid holocene episodes of climate deterioration towards drier conditions indicated by a decrease of clay translocation processes and possible irreversible dehydration of poorly crystalline aluminosilicates into phyllosilicate clay minerals promoted intense land degradation this was in turn enhanced by increasing human activities for settlement and resource exploitation among which deforestation and ploughing for agriculture which led to a shift of the vegetation cover towards a dominant pine forest between 3 ka bp and the roman epoch humid and possibly cooler climatic conditions during the late holocene are indicated by the decrease of clay illuviation coupled with short range order components prevailing over phyllosilicate clays during roman soil formation

weathering of the oporto granite geotechnical and physical properties abstract this paper characterizes the weathering products of the two mica oporto granite in terms of its mineralogical chemical geotechnical and physical properties this information is used to identify a physical property that can be used as an index of the degree of weathering and to estimate other properties in outcrop the oporto granite is always weathered and weathering profiles frequently exceed 20 m within these profiles granitic saprolites are composed of quartz feldspars and some mica with kaolinite and gibbsite as final weathering products the average percentage of secondary minerals determined by bulk x ray diffraction xrd is low in both weathered rock 2 4 and saprolite 8 7 geotechnically the saprolites exhibit no or low plasticity plasticity index pi 12 the skeleton character of the saprolites is reflected in the significant proportion of fines 29 5

a spheroidal weathering model coupling porewater chemistry to soil thicknesses during steady state denudation abstract spheroidal weathering a common mechanism that initiates the transformation of bedrock to saprolite creates concentric fractures demarcating relatively unaltered corestones and progressively more altered rindlets in the spheroidally weathering rio blanco quartz diorite puerto rico diffusion of oxygen into corestones initiates oxidation of ferrous minerals and precipitation of ferric oxides a positive v of reaction results in the build up of elastic strain energy in the rock formation of each fracture is postulated to occur when the strain energy in a layer equals the fracture surface energy the rate of spheroidal weathering is thus a function of the concentration of reactants the reaction rate the rate of transport and the mechanical properties of the rock substitution of reasonable values for the parameters involved in the model produces results consistent with the observed thickness of rindlets in the rio icacos bedrock 2 3 cm and a time interval between fractures 200 300 a based on an assumption of steady state denudation at the measured rate of 0 01 cm a averaged over times longer than this interval the rate of advance of the bedrock saprolite interface during spheroidal weathering the weathering advance rate is constant with time assuming that the oxygen concentration at the bedrock saprolite interface varies with the thickness of soil saprolite yields predictive equations for how weathering advance rate and steady state saprolite soil thickness depend upon atmospheric oxygen levels and upon denudation rate the denudation and weathering advance rates at steady state are therefore related through a condition on the concentration of porewater oxygen at the base of the saprolite in our model for spheroidal weathering of the rio blanco quartz diorite fractures occur every 250 yr ferric oxide is fully depleted over a four rindlet set in 1000 yr and saprolitization is completed in 5000 yr in the zone containing 20 rindlets spheroidal weathering thus allows weathering to keep up with the high rate of denudation by enhancing access of bedrock to reactants by fracturing coupling of denudation and weathering advance rates can also occur for the case that weathering occurs without spheroidal fractures but for the same kinetics and transport parameters the maximum rate of saprolitization achieved would be far smaller than the rate of denudation for the rio blanco system the spheroidal weathering model provides a quantitative picture of how physical and chemical processes can be coupled explicitly during bedrock alteration to soil to explain weathering advance rates that are constant in time

past and recent tritium levels in arctic and antarctic polar caps tritium concentration was measured in snow deposited at the grip site central greenland and at the vostok station east antarctica from snow pits covering the period 1980 1990 the objective of the study was to investigate tritium concentrations in polar regions several decades after the bomb peak of the sixties and to put them in the context of available data for environmental tritium in the arctic and the antarctic over the last five decades the tritium content of the samples was measured by mass spectrometry using the helium 3 regrowth method in antarctica the tritium concentrations are in the range 70 110 tu the comparison of the bomb tritium history at different locations show that tritium levels increase moving inland where vapour pressure becomes extremely low and therefore more sensitive to the intrusion of stratospheric air masses highly enriched in tritium although most tritium fallout occurred in the northern hemisphere the tritium levels in central greenland in the 80 s in the range 10 40 tu are significantly lower than at vostok unlike antarctica no such continental effect is observed in greenland due to the higher water vapour content of the air masses as evidenced by the much higher snow accumulation rate whereas tritium fallout in antarctica appears to occur as a result of direct injections of stratospheric tritium during winter arctic fallout are the result of the dominant spring injection of stratospheric air at mid latitude in line with the deposition of other stratospheric tracers

late neoproterozoic baltic paleosol intense weathering at high latitude the neoproterozoic was a time when repeated global cooling events interrupted by supergreenhouse phases preceded environmental change toward a modern oxygen rich atmosphere and the eventual emergence of animal life cyclically increased atmospheric co2 levels intensified weathering of continental silicates but little is known about the influence of neoproterozoic climates on soil morphogenesis which acts as a direct proxy of conditions at the time of formation however being typically fragmented in time and space these mineralic soils paleosols had a low preservation potential an exceptionally well preserved neoproterozoic deeply weathered paleosol on the baltica paleocontinent provides new information on weathering during the precambrian the kaolinite fe oxyhydroxide composition of this paleosol is indicative of intense weathering in a stable landscape at a time when baltica was positioned between intermediate to high southern latitudes it is plausible that this paleosol developed over long steady state weathering under temperate climatic conditions or alternatively during an intensified weathering event triggered by elevated co2 levels and transient greenhouse climatic conditions at the termination of ediacaran glaciations or possibly the ediacaran shuram wonoka isotope event

weathering profiles and clay mineralogical developments bornholm denmark abstract saprock saprolite associations were studied by field and laboratory methods optical microscopy x ray powder diffraction scanning electron microscopy electron microprobe in order to describe regolith development in the crystalline rocks of the nygard kaolin pit bornholm denmark the clay sequences and stages of porosity development are similar to those observed for reservoir rocks from the utsira high riber et al 2016 the weathering of the parent granite began before the end of the mesozoic two stages of syn pre burial alteration followed by diagenesis during burial and then post uplift weathering have been recognized in stage plagioclase and some biotite biotite vermiculite kaolinite reacted to form elongate booklets of highly ordered kaolinite or smaller blocky pseudohexagonal crystals stage ii represented more extreme weathering developed along local fracture systems the higher potential for fluid flow in the fractures caused highly ordered kaolinite to alter to halloysitic poorly ordered kaolinite plagioclase biotite and k feldspar continued to interact with formation water and formed additional quantities of secondary clay minerals as a consequence of inter intra and trans granular cracks the original rock fabric deteriorated and porosity increased during later burial diagenetic siderite crystals filled voids and chlorite formed at the expense of kaolinite after re exposure calcite precipitated in localized zones smectite formed on a broader scale wherever high ionic strength groundwaters were present a mineralogical key to predicting where high porosity and permeability zones occur is the recognition of halloysitic poorly ordered kaolinite highly ordered kaolinite is abundant but it is ubiquitous siderite chlorite and smectite adversely affect permeability riber l dypvik h sorlie r and ferrell r 2016 clay minerals in deeply buried paleoregolith profiles norwegian north sea clays clay miner doi 10 1346 ccmn 2016 064036

an integrated approach to assess the origins of black films on a granite monument in the present study samples arising from the scaling of a portuguese granite building were examined in an attempt to understand the mechanisms of surface blackening and detachment the building the third order of st francis church is located in the city centre of porto which is an area characterised by moderate motor traffic the mediterranean climate and the facade orientation favoured the proliferation of microorganisms on the third order of st francis church in porto the scientific approach carried out in the south facade revealed that these coloured layers are essentially of biological origin subsequent chemical analysis confirmed microscope observations and pointed out to the presence of organic matter synthesised by cyanobacteria algae and lichens numerous biological marker compounds indicated a significant presence of biogenically derived material suggesting that biological activity was playing a major role in the development of coloured layers and in the detachment processes in this historic building

mineralogy maketh mountains granitic landscapes shaped by dissolution abstract in tectonically quiet regions the shape of the landscape is controlled by the erosion resistance of the rocks erosion largely depends on the release of particles from the weathering rock which in turn requires a degree of dissolution of the more soluble grains the rate of dissolution of the common rock forming minerals allows the construction of a numerical rock weatherability scale rws based on the rock s modal mineralogical analysis applied regionally to three granitic landscape regions of the bega valley of southern new south wales the tate batholith and featherbed volcanics of north queensland and granitoids in the beaufort region of victoria the mean elevation of the larger plutons in each region correlates highly r 0 83 0 93 with their rws variation in composition within a pluton also shows there is a clear connection between changes in rws and relief within the pluton from these results it is apparent that the landscape of such granitic terrains is determined very largely by mineral dissolution rates with plagioclase composition and content being a major factor

sources and reservoirs of anthropogenic iodine 129 in western new york large quantities of iodine 129 have been released during nuclear weapons testing and from nuclear power and fuel reprocessing plants the distribution of this isotope was investigated in 110 surface water and soil samples from western new york where several potential point sources are located and other areas of north america to evaluate its sources transport pathways and reservoirs elevated 129i concentrations associated with a former reprocessing facility at west valley ny can be tracked to lakes erie and ontario via site drainage and for over 200 km via atmospheric transport while only a negligible signal is associated with active power plants in the area the results point to local reprocessing as the major source of 129i in western new york while bomb fallout constitutes less than 0 5 of the signal surface soil is the dominant reservoir for anthropogenic 129i in this region across north america 129i concentrations are lower than in western new york although still significantly higher than expected weapons fallout reprocessing releases are currently seen to be the major source for elevated 129i concentrations on a global scale in contrast to previous suggestions that most anthropogenic 129i was still derived from weapons fallout concentrations of 129i and iodine in surface reservoirs are generally found to be uncorrelated implying that natural iodine and anthropogenic 129i are not yet in equilibrium the results suggest that anthropogenic 129i is cycled between the atmosphere soil vegetation systems more rapidly than natural pre anthropogenic iodine

above the weathering front contrasting approaches to the study and classification of weathered mantle abstract weathered mantle comprises the materials above bedrock and below the soil it can vary in thickness from millimeters to hundreds of meters depending primarily on climate and parent material study of the weathered mantle comes within the realms of four disciplines geology geomorphology soil science and civil engineering each of which uses a different approach to describe and classify the material the approaches of engineers geomorphologists and geologists are contrasted and compared using example papers from the published literature soil scientists rarely study the weathering profile as such and instead concentrate upon soil forming processes and spatial distribution primarily in the solum engineers including engineering geologists study the stability and durability of the weathered mantle and the strength of the materials using sophisticated procedures to classify weathered materials but their approach tends to be one dimensional furthermore they believe that the study of mineralogy and chemistry is not useful geomorphologists deal with weathering in terms of process how the weathered mantle is formed and with respect to landform evolution using a spatial approach geologists tend to ignore the weathered mantle because it is not bedrock or to study its mineralogy and or chemistry in the laboratory i recommend that the approaches of the various disciplines be integrated geomorphologists and geologists should consider using engineering weathering classifications and geologists should adopt a spatial perspective to weathering as should engineers and engineering geologists

global distribution and long term fate of anthropogenic 129i in marine and surface water reservoirs 1 since the advent of the nuclear age in the mid 1940s the mass of radioactive 129i t1 2 15 7 myr circulating in the earth s hydrosphere has increased nearly fortyfold from its natural background level of 140 kg nuclear fuel reprocessing has been by far the major contributor responsible for releasing 5400 kg of 129i primarily into the north atlantic ocean regional and global trends in the distribution of the 129i inventory are elucidated from an examination of more than 600 determinations of 129i in environmental samples from around the world because the major point sources are located in europe and the united states more than 99 of the present 129i reservoir is distributed in the northern hemisphere where both 129i concentrations and 129i i ratios in rivers lakes and shallow seawater are several orders of magnitude above the preanthropogenic background downwelling in the north atlantic presently provides a major sink for marine 129i however marine upwelling along the margins of the pacific will eventually return part of this anthropogenic input to the ocean surface where it will find its way back into surface waters and the atmosphere iodine 129 has a long half life 15 7 myr and consequently there is also the possibility that climate change will influence the dynamics of iodine transfer in surface reservoirs we model the effect of a collapse in thermohaline circulation and project a concentration increase of more than 3 orders of magnitude in shallow oceans over the 10 000 years that follow if nuclear reprocessing is to continue at the present rate

geotechnical and landslide aspects in weathered granitoid rock masses serre massif southern calabria italy abstract the weathering processes produce important chemical and physical transformations in rock masses producing a decay of their strength and then stability in this study different methodologies were employed to define the physical mechanical properties and the minero petrographical changes at each grade of weathering useful to determine a geological model of the weathered granitoids involved in mass movements the paper focuses on a multidisciplinary research on the weathering profiles of the paleozoic granitoid rocks surrounding the village of fabrizia located in the serre massif southern calabria italy fabrizia lies on an old erosion surface composed of basement rocks made up of weathered granitoids belonging to the serre massif granitoid complex and overlain by thin eluvial colluvial deposits the tectonic uplift of the area combined with mediterranean climatic conditions both active at least since the quaternary are the main causes of the deep weathering of the plutonic rocks the weathered profiles of the granitoid complex have been studied through field observations borehole explorations with geotechnical tests and seismic surveys coupled to minero petrographical analysis and laboratory tests weathered profiles are mainly composed by rock masses varying from completely weathered and residual soil classes v vi to moderately weathered rocks class iii characterized by a progressive increase of geotechnical properties e g seismic wave velocity rock quality designation internal friction angle uniaxial compressive strength with a decrease of weathering the weathered rocks display a wide variety of mass movement landslide types are rockfalls for the fresher rocks class iii translational slides occur between different weathering degrees classes iv and v and rotational slides dominate at the top of the slopes and generally involve the weathering grades from class iv to classes v vi the shallow horizons are composed of thin eluvial colluvial deposits and more weathered granitoids classes v vi that may generate dangerous debris flows or debris avalanches during intense and prolonged rainfall the landslide surface is usually at a depth lower than 2 m in the debris flow type while deeper landslides depth 2 m are rotational and translational types with sliding surfaces occurring mainly in the transition between the classes iv and v the field survey coupled to geotechnical geophysical and minero petrographical data allowed the recognition of the different weathered horizons and relative geotechnical properties useful to the reconstruction of the reliable geological model the model represents an important support for the study of the landslide processes and for a sustainable management of the territory the used approach provided results to set a general reference framework for establishing more precise correlations between mass movement phenomena and weathering processes

volumetric curvature attributes add value to 3d seismic data interpretation horizon based curvature attributes have been used in seismic data interpretation for predicting fractures since 1994 when lisle demonstrated the correlation of curvature values to fractures measured on an outcrop different measures of curvature such as gaussian strike and dip have been shown by different workers to be highly correlated with fractures and many more applications are also possible by definition all such applications need the interpretation of a seismic horizon which may be simple if data quality is good and the horizon of interest corresponds to a prominent impedance contrast

saprolite soil transformations in the piedmont and mountains of north carolina abstract in the piedmont and mountain provinces of north carolina average annual precipitation exceeds evapotranspiration soil solum thickness is usually 1 to 2 m saprolite thickness is variable but related to rock type and geomorphic position slow hydraulic conductivity in the zone between the soil and the saprolite appears to restrict vertical percolation of water thus slowing saprolite weathering on convex slopes in saprolite zones immediately above granitic gneiss often about 5 m below the surface halloysite gibbsite and x ray amorphous aluminosilicate clay are the initial secondary minerals formed halloysite contents increase upward in the saprolite apparently from resilication of gibbsite and the amorphous aluminosilicates in the upper zones of the saprolite the halloysite is recrystallized into kaolinite which is the predominant clay sized mineral in the soil over gabbro and metagabbro rocks the lower zones of the saprolite contain appreciable quantities of smectite vermiculite and where chlorite is present regularly interstratified chlorite smectite although these smectite minerals become partially interlayered with hydroxy aluminum in the overlying soil they p persist as a substantial component of the clay sized fraction saprolite thickness is less than over the granitic rocks increased run off and lateral through flow produced by low hydraulic conductives of smectite rich argillic horizons and convex hill slopes are believed to be responsible for the thin saprolite above mafic bedrock soils and saprolites from biotitic gneiss on upper sideslopes in the mountain physiographic province have mineralogical trends with depth similar to those found over the granitic gneisses of the piedmont gibbsite often constitutes as much as 30 of the clay and contents tend to increase in the deeper saprolite zones biotite sand which is common throughout the soil and saprolite alters to kaolinite sand under the acidic conditions of the saprolite sand sized mica appears resistant to weathering except where there is evidence of physical transport

impact of weathering on ree distribution in soil saprolite profiles developed on orthogneisses in borborema province ne brazil abstract rare earth elements rees are a group of elements from la to lu with high economic value and serve mainly as essential raw material for various high technology items this study explores mineral weathering and the geochemical evolution of regoliths quaternary period derived from orthogneisses late cretaceous period in four sites in borborema province ne brazil providing a new contribution to the understanding of the influence of soil and saprolite attributes on the distribution of rees in the regolith we used optical and electron microscopy to depict the weathering of minerals in the rock saprolite and soil microstructure focusing on the distribution of rees in the regolith depth 3 0 m we also determined the poorly and well crystallized iron oxide contents the clay fraction amount and the total organic carbon content to observe how these attributes influence the distribution of rees in the soil and saprolite the results allowed the classification of weathering for feldspars micas and other primary minerals into four stages based on their degree of alteration and the consequent influence on the geochemistry of the regoliths advancement of the weathering stages revealed the relative increases in fe and ti compared with ca mg na and k from the fresh rock up to the soil horizons and ilmenite and xenotime were the main sources of yb y co and p the patterns of signatures and anomalies were different for light lrees middle mrees and heavy rare earth elements hrees and for regoliths in different metamorphic complexes the lrees related well with the clay fraction amount the poorly crystallized iron oxides and the degree of weathering as estimated by the mineralogical index of alteration mia while the hrees related well with the total organic carbon toc in particular ce was strongly associated with mn oxides possibly due to simultaneous oxidative precipitation

mineral alteration and genesis of al rich soils derived from conglomerate deposits in cabo basin ne brazil abstract in the cabo basin ne brazil conglomerates have given rise to soils with attributes that are rarely observed in humid tropical climates and remain relatively unknown within the scientific community these soils have high levels of al in the exchangeable phase diminishing their agricultural and environmental potential in an underdeveloped region of great socioeconomic importance this paper presents the mineralogy and genesis of soils derived from conglomerates on a slope in the cabo basin with the aim of meeting the demand for studies on al rich soils three soils were classified morphologically described and sampled for the accomplishment of chemical physical and mineralogical analyses including the main exchangeable cations content mineralogy of the sand silt and clay fraction differentiation of the fe and al forms mineral micromorphology and chemical composition of mineral species in addition chemical and physical attributes were used in multivariate analyses the soil mineralogy is associated with the weathering evolution of three mineralogical zones identified in the cr horizons pathways of alteration followed by feldspars and micas resulted in kaolinite smectite and hydroxy al interlayered smectite formation argilification the susceptibility of the conglomerate to weathering constant releases of al from the structure of aluminous minerals low contents of exchangeable bases and consequent low ph values

nature of parent rocks mineralization styles and ore genesis of regolith hosted ree deposits in south china an integrated genetic model abstract regolith hosted rare earth element ree deposits also called ion adsorption or weathered crust elution deposited ree deposits are distributed over jiangxi guangdong fujian hunan guangxi and yunnan provinces in south china in general these deposits can be categorized into the hree dominated type for example the famous zudong deposit in southern jiangxi province and the lree dominated type such as the heling and dingnan deposits in southern jiangxi province most of these deposits form from weathering of biotite and muscovite granites syenites monzogranites granodiorites granite porphyries and rhyolitic tuffs the parent rocks are generally peraluminous siliceous alkaline and contain a variety of ree bearing minerals mostly ree patterns of regolith are inherited from the parent rocks and therefore characteristics of the parent rocks impose a significant control on the ore formation data compilation shows that autometasomatism during the latest stage of granite crystallization is likely essential in forming the hree enriched granites whereas lree enriched granites could form through magmatic differentiation these deposits are normally two to three fold but could be up to ten fold enrichment in ree compared to the parent granites where the maximum enrichment usually occurs from the lower b to the upper c horizon ce shows different behavior with the other rees strongly positive ce anomalies commonly occur at the upper part of weathering profiles likely due to oxidation of ce 3 to ce 4 and removal of ce from soil solutions through precipitation of cerianite vertical ph and redox gradients in weathering crusts facilitate dissolution of ree bearing minerals at shallow level and fixation of ree at depth through either adsorption on clay minerals or precipitation of secondary minerals at the same time mass removal of major elements plays an important role in concentrating ree in regolith combination of mass removal and eluviation illuviation dynamics is the main mechanism for ree accumulation in weathering crusts favorable exogenetic factors facilitate the accumulation of ree in regolith and preservation of the ore bodies these include quasi equilibrium between denudation and exhumation at regional scales local geomorphology dominated by low lying gentle slopes adequate rainfall and favorable groundwater conditions continuous operation of such a dynamic weathering system is essential in the formation of regolith hosted ree deposits

elemental and strontium isotopic geochemistry of the soil profiles developed on limestone and sandstone in karstic terrain on yunnan guizhou plateau china implications for chemical weathering and parent materials abstract the limestone and yellow sandstone soil profiles from sw china were measured for chemical and sr isotope compositions of the bulk soils and their sequential leachates labile carbonate and residue or silicate fraction aiming to characterize the parent materials of the soils to understand the soil weathering and formation processes and to discuss the origin of the red residua terra rossa the studied yellow sandstone soil yellow limestone soil and black limestone soil show different ph values sio 2 contents rb sr abundance ratios and 87 sr 86 sr ratios the sequential leachates of different soil types also have different 87 sr 86 sr and ca sr ratios the major chemical compositions of the studied soil profiles suggest that all the sandstone and limestone soils are developing at a stage that feldspar is exhausting and the clay minerals are changing from smectite to kaolinite and gibbsite as compared with the red residua distributed in the karst region the soils studied here show lower cia values 58 84 but both higher na 2 o k 2 o 0 9 2 7 and na 2 o al 2 o 3 concentration ratios 0 07 0 26 on average suggesting a lower weathering intensity than that of the red residua the depth profiles of soil cia values na 2 o k 2 o and rb sr ratios and 87 sr 86 sr ratios indicate that the weathering intensity is slightly lower for the upper and higher for the deeper soils which suggest that the sandstone and limestone soil profiles were formed through both accumulation and weathering of in situ weathering residue and input of external detritus or soil from upper land during weathering of the soils preferential release of ca and retention of sr in soil result in higher ca sr ratios in both labile and carbonate fractions than those in the residue fractions of all soil profiles the co variations of hf nb and zr nb ratios together with those rb sr and 87 sr 86 sr ratios of limestone soils sandstone soils and the red residua demonstrate that their parent materials are distinct and support the point that the widely distributed red residua is originated from the weathering residua of both carbonate and silicate clastic rocks and further weathering of the weathering residua resulted in intensive release of si na ca and relative enrichment of al k and other immobile elements in the red residua

investigation of shuttle radar topography mission data of the possible impact structure at serra da cangalha brazil the serra da cangalha crater structure in northeast brazil 13 km in diameter has long been widely considered to be a confirmed impact structure based on reports of shatter cone findings only very limited field work has been carried out at this crater structure landsat thematic mapper tm and shuttle radar topography mission srtm data sets for the region around this crater structure are compared here with regard to their suitability to determine first order structural detail of impact crater structures the srtm data provide very detailed information regarding drainage patterns and topography a pronounced central ring of up to 300 m elevation above the surrounding area two comparatively subdued intermediate rings of 6 and 10 5 km diameter respectively and the broad complex crater rim of up to 100 m elevation can be distinguished in the serra da cangalha data the maximum cratering related regional deformation radial and concentric features seems to be limited to a radial distance of 16 18 km from the center of the structure a first comparison of macrostructural information from several impact structures with that from serra da cangalha does not yield firm trends but the database is still very small at this stage the varied nature of the target geology strongly influences the development of structural features in any impact event

volcanic soil formation in calabria southern italy the cecita lake geosol in the late quaternary geomorphological evolution of the sila uplands abstract this paper focuses on the main morphological physical chemical and mineralogical features of an andic like soil widely outcropping in the sila upland plateau of calabria southern italy and its potential role in tephrostratigraphy a multidisciplinary and multiscale approach allowed identification of this soil as a masked distal archive of volcanic products developed on granite rocks and sediments with a coeval pyroclastic input during pedogenesis the study demonstrates that the contribution of volcanic parent materials can be successfully hypothesized and assessed even in the absence limited extent or poor preservation of primary eruptive products the soil has an andisol like appearance despite laboratory data that do not match the entire suite of diagnostic criteria for the andisol taxonomic order geomorphological stratigraphic and pedologic results coupled with tephrostratigraphic and radiometric data concur to suggest a late pleistocene to holocene age of the andisol like soil in particular the rhyolitic chemical composition of small sized glass fragments identified by sem eds analyses indicates soil genesis contributed by volcanic ash probably sourced from aeolian arc explosive activity spanning the last 30 ka accordingly the evidence of limited relict clay illuviation and the specific type of pedogenesis allowing the development of andic properties in turn related to the neoformation of clay minerals from the weathering of volcanic glass are consistent with a climatic shift from a seasonally contrasted to a constantly humid pedoenvironment this change can be ascribed to the lateglacial or early middle holocene to late holocene transition calibrated ams 14 c dates performed on charcoal fragments sampled from three representative soil profiles provide late holocene ages 3136 19 343 16 and 92 24 yr bp in accord with archaeological finds on the basis of the consistent stratigraphic position lateral continuity and wide extent the soil can be considered a good pedostratigraphic marker in the sila highlands and is informally defined as the cecita lake geosol it supplies valuable time constraints for the underlying occasionally overlying deposits and or soils moreover it allows regional scale morphostratigraphic correlations and detailed reconstruction of late pleistocene holocene geomorphic events in calabria a very suitable region for distal tephra deposition in the central mediterranean peri volcanic area the effects of high energy volcanic eruptions are interfingered with or superimposed by other geomorphic processes and climatic or anthropogenic signals

effect of granite crystal grain size on soil properties and pedogenic processes along a lithosequence this study generated new insight into the effect of bedrock grain sizes on pedogenesis under identical topographic and climatic environment the physico chemical and mineralogical properties of two adjacent typic dystrochrepts usda 1999 respectively developed from fine and coarse textured granites were compared this research study was performed in the morvan mountains france analysis of the two underlying bedrocks revealed similar chemical and mineralogical properties with the crystal grain size being the only parameter which differed in these soils bedrock played the key role in the particle size fraction distribution the main factor controlling water retention in the soils weathering reactions of clay minerals were more marked in the fine textured granite soil in this soil both clay mineral swelling and mica transformation into expansible phyllosilicates were greater compared to the coarse textured granite soil in the clay fraction of the fine textured granite soil there were smaller amounts of low crystallised fe and al minerals with higher carbon content in the topsoil as compared to the coarse granite soil the exchangeable cation analysis of the fine textured granite soil revealed a higher proportion of base saturation and a smaller proportion of altit than in coarse textured granite soil which could be explained by preferential leaching of al cations the decrease in exchangeable al the higher swelling of the smectitic layer and the smaller proportion of fe and al oxy hydroxides could be explained by the complexing acid conditions which increased mineral weathering and al leaching the higher water retention increased the time of contact between minerals and the soil solution and the higher carbon content in the topsoil could have enhanced the complexing acid conditions resume d auteur

behaviour of li isotopes during regolith formation on granite massif central france controls on the dissolved load in water saprolite soil and sediment abstract lithium li contents and isotopes were studied in all environments of a small river catchment draining granite in the margeride mountains of the french massif central this covered surface waters primary and accessory minerals of the granites the whole rock and soil and sediment samples developed in the catchment completed with regional data for mineral waters and rainwater the integrated investigation aimed at evaluating the potential of li isotopes as effective tracers of water rock interaction processes within a granitic environment the 7li values and li concentrations were measured on sediment and soil samples following standard acid dissolution procedures and chemical purification of li using the cationic exchange resin protocol in a clean lab lithium isotope compositions were measured with a neptune mc icp ms and li concentrations by icp ms the samples represented different stages of granite weathering including fresh granite weathered rock surface saprolite and sediments in riverbanks and fields bordering the streams the extent of li mobility during granite weathering was first evaluated through determining the percentage change relative to ti with a range from 31 to 66 in the collected samples the weathered rock was depleted by 47 for li with negative 7li values ranging from 1 9 to 3 4 soil to riverbank sediment samples were characterized by less negative 7li values indicating that li is enriched in soil with fractionation of li isotopes and changes of the mineral abundance in the samples to complement this first view we i modelled the theoretical li isotope signature of water interacting with granite using a weathering model based on dissolution ii applied an atmospheric input correction to surface waters iii applied a raleigh equation for modelling the li isotope fractionation when compared with corrected surface water and mineral water and iv compared li isotopes with sr isotope data in a larger weathering framework

role of lichens in weathering of granodiorite in the sila uplands calabria southern italy this paper explores the role of five recurrent epilithic lichen species aspicilia intermutans nyl arnold xanthoparmelia pulla ach o blanco a crespo elix d hawksw lumbsch rhizocarpon lecanorinum anders tephromela atra huds hafellner and lecanora bolcana pollini poelt which encrust granodiorite spheroidal boulders exposed in the sila uplands calabria southern italy in weathering of plutonic rocks in a typical mountainous mediterranean environment a detailed investigation was carried out on the lichen rock interface of each species by comparing them mutually and with lichen free granodiorite samples for this purpose the lichen species were sampled together with the encrusted rock surface for detailed mineral petrographic analyses performed in thin and ultra thin sections optical and scanning electron microscopy of these sections and of bulk samples permitted us to highlight the peculiar modes of physical and chemical attacks of lichen thalli and hyphae on and into the substratum for each species crack systems often parallel to the outer rock surface appear often intruded by hyphae which cause rupture of primary minerals with detachment and progressive incorporation of their fragments into the thallus in particular the species l bolcana and t atra revealed an unexpected partly endolithic behavior presumably enhanced by the presence of rock fractures earlier generated by other physical breakage processes already affecting the spheroidal boulders in the sila mountains dissolution features often affect primary minerals even quartz that may show very peculiar patterns which are suggestive of a biologically induced control various phyllosilicate clay minerals were identified using sem eds microprobe analyses and ft ir spectroscopy which also enabled the identification of possible amorphous silica or quartz micrograins rhizocarpic acid and carotenoid at the encrusted granodiorite interface in contrast neither oxalic acids nor oxalates were detected

insight into radio isotope 129i deposition in fresh snow at a remote glacier basin of northeast tibetan plateau china we present data of 129i deposition in fresh snow in the laohugou glacier basin northeast tibetan plateau in summer 2016 and 2017 and trace its source and elevational distribution in the troposphere our results show that the 129i 127i atomic ratios in the fresh snow on the glacier surface are about 2 orders of magnitude larger than those in the antarctic fresh snow and 4 orders the prenuclear level indicating a predominantly anthropogenic source of the 129i in the mountain glacier environment of northeast tibetan plateau the 129i level in the laohugou glacier basin is 1 2 orders of magnitude lower than at representative european locations and not significantly higher than that observed at other sites in asia the 129i 127i atomic ratio and 129i level show clear increases with elevation from 4 300 to 5 100 m above sea level the 129i in the laohugou glacier basin is probably deposited from the upper troposphere where there exists a local maximum of 129i a conceptual model for interpretation of the observed 129i concentration and profile in laohugou is provided thus this work is of importance in providing a more complete view on the transport dispersion and removal of 129i in the atmosphere

the interplay of geomorphic processes and soil development in an upland environment calabria south italy abstract five representative soil profiles outcropping in the area around the cecita lake calabria south italy were characterised by field work chemical and mineralogical analyses optical and scanning electron microscopy interactions among weathering pedogenesis and geomorphic processes are emphasised in an attempt to link the results obtained at different scales of observation the important role of topography in controlling soil development or removal by erosive processes is discussed in relation to the natural geomorphological context and the effects of human pressure both present day and relict features were recognised in the studied soils and discussed in terms of environmental conditions and climatic changes the chemical composition of volcanoclastic components identified in some soil horizons with andosol like field appearance coupled with pedogenetic features contributed useful chronological constraints for the reconstruction of late quaternary geomorphic events

a case study of a precariously balanced rock its partially exhumed corestone platform and encasing saprock and soil abstract lying between the elsinore and san jacinto faults 0 5 km se of roundtop is a tonalitic corestone perched precariously on an exhumed corestone base such features are referred to as precariously balanced rocks pbrs cosmogenic 10be data listed in an online abstract suggest a tentative exhumation age of the pbr near roundtop at 35 000 years ago the absence of pbrs adjacent to the elsinore and san jacinto faults implies that they were shaken free from their perches during ground shaking alternatively their absence may reflect a more highly fractured and intensely weathered terrane because the weathering histories of pbrs have not been studied previously we analyzed the texture clay mineralogy and geochemistry of the roundtop pbr to answer several basic questions can the characteristics of the regolith that once encased the precariously balanced rock be reconstructed what chemical processes operated in the regolith prior to exhumation and are these processes still occurring following exhumation did new fracture development modify the original regolith to answer these questions we extracted three 1 m long cores from the pbr near roundtop and collected 23 saprock and 9 pebbly sandy loam samples from a trench excavated near the base of the corestone platform plagioclase and biotite alteration along with the concomitant loss of ca na sr ba k mg mn nb and p mass are the primary evidence of weathering intensity within the saprock additionally the presence of mostly kaolinite and lesser quantities of mixed layer biotite smectite in the saprock along with the above observations and data point to significant fluid rock interations during saprock development subsequent formation of pebbly sandy loam appears to have been accomplished primarily through pedoturbation within the uppermost portions of the underlying already weathered saprock and produced little additional chemical weathering hence our data support the general idea that roundtop is an area of weak ground shaking and that since current exhumation little weathering has affected this pbr locality

lithological effects in soil formation and soil slips on weathering limited slopes underlain by granitic bedrocks in japan abstract soil slips occur every few years due to heavy rains on biotite granite gb and hornblende biotite granite ghb slopes in the taga mountains ibaraki prefecture japan the occurrence density of soil slips per unit area is 2 7 times greater in the gb slopes than that in ghb slopes we examined the chemical mineral physical and mechanical properties of two soil profiles on soil slip scars in these slopes to study the effect of bedrock mineral composition on the density of soil slips for a given size of mineral grain the amount of biotite which is susceptible to chemical weathering in granitic bedrocks strongly influenced the density of soil slips in the gb slope the soil layer becomes thinner because of the smaller proportion of biotite in the bedrock this restricts the downward movement of soil water into the material below the slip plane during heavy rainfall the water surface then rises toward the slope surface above the slip plane this promotes soil slips increasing the density of soil slip scars in contrast in the ghb slope with more biotite in the bedrock the soil layer becomes thicker so that soil water moves easily into the material beneath the slip plane this limits the rise of water surface toward the slope surface above the slip plane even during heavy rainfalls there are consequently fewer soil slips and density of soil slip scars

129i in gulf of mexico waters abstract nuclear weaponry and power generation have released far more 129 i onto the earth s surface than was formerly present the effects of this release are clearly visible in the waters of the gulf of mexico far from the major sources new 129 i is found down to at least 500 m and probably to 1000 m surface values are approximately 60 times the pre nuclear era levels the 129 i penetration depth of 470 m agrees well with that determined from bomb fallout isotopes 3 h and 14 c during the 1970s and 1980s in the gulf of mexico and in the western north atlantic at similar latitudes the observed levels exceed amounts expected from globally distributed nuclear test fallout the observed surplus must come primarily from spent fuel reprocessing plants in the eastern north atlantic followed by rapid circulation of the north atlantic gyre and subsequent delivery into the caribbean sea and thence into the gulf of mexico airborne transport also appears significant

3d volumetric multispectral estimates of reflector curvature and rotation one of the most accepted geologic models is the relation between reflector curvature and the presence of open and closed fractures such fractures as well as other small discontinuities are relatively small and below the imaging rangeofconventionalseismicdata dependingonthetectonic regime structural geologists link open fractures to either gaussian curvature or to curvature in the dip or strike directions reflector curvature is fractal in nature with different tectonic and lithologic effects being illuminated at the 50 m and1000 m scales untilnow suchcurvatureestimateshave been limited to the analysis of picked horizons we have developed what we feel to be the first volumetric spectral estimates of reflector curvature we find that the most positive and negative curvatures are the most valuable in the conventional mapping of lineations including faults folds and flexures curvatureismathematicallyindependentof andinterpretatively complementary to the well established coherence geometric attribute we find the long spectral wavelengthcurvatureestimatestobeofparticularvalueinextracting subtle broad features in the seismic data such as folds flexures collapse features fault drags and under and overmigrated fault terminations we illustrate the value of these spectral curvature estimates and compare them to other attributes through application to two land data sets a salt domefromtheonshorelouisianagulfcoastandafractured karsteddatavolumefromfortworthbasinofnorthtexas

sunshading geophysical data using fractional order horizontal gradients the interpretation of linear features in geophysical imagery is of considerable importance because they can correspond to dykes faults or other geologic discontinuities one popular tool commonly used for their enhancement is sunshading which considers the data values as if they were a topographic surface that is illuminated by a light source or sun which has a specified azimuth and elevation the reflectance of the light by the surface is calculated and imaged features whose strike direction is orthogonal to the sun azimuth reflect the light strongly and are consequently enhanced while those lying parallel to the sun direction do not reflect the light and become less apparent as a result the reflectance algorithm uses the first horizontal gradients of the data calculated in two orthogonal directions horn 1982

weathering of granites in a temperate climate nw portugal granitic saprolites and arenization abstract saprolites or in situ weathering products from granitoid rocks of northwest portugal were studied by means of x ray diffraction xrd of their clay fraction and observations of polished thin sections combined with transmission electron microscopy tem scanning electron microscopy with energy dispersive spectrometer sem eds microanalyses their principal features are 1 depths of more than 10 m 2 mean material loss of 40 as calculated by an isovolumetric method 3 low clay content mean value of 7 and a high degree of mineralogical evolution the clay fraction is characterized by a predominance of kaolinite and gibbsite with subordinate 2 1 minerals illite chlorite vermiculitic mixed layers vermiculite the significance of the secondary minerals in granitic saprolites from northwest portugal is compared to published data from atlantic europe this allows the definition of a climatic zonality for weathering products and identifies arenization as an important weathering process

aorounga and gweni fada impact structures chad remote sensing petrography and geochemistry of target rocks shuttle radar topography mission data was used to investigate the aorounga and gweni fada impact structures in chad as part of a new remote sensing study we believe the results of various data treatments provide extensive new perspective on the macro structural and topographic divisions for these two impact structures our remote sensing studies indicate revised diameters of aorounga and gweni fada of 16 and 22 km respectively we selected samples from these two structures for their petrographic geochemical and rb sr and sm nd isotopic characteristics in samples from both structures evidence for shock metamorphism was found in the form of single or multiple sets of planar deformation features in quartz which confirms the impact origin for both the aorounga and gweni fada structures the crystallographic orientations of pdfs indicate maximum shock levels of 20 30 gpa for samples from the central parts of both structures the pdf orientations are characteristic for the orientations observed elsewhere in shocked sandstones with the higher angles in the orientation histograms being fairly abundant geochemically the rocks are typical upper crustal sandstones

effects of slope orientation on pedogenesis of altimontane soils from the brazilian semi arid region baturite massif ceara given the importance of climate conditions for the development of soils studies on climosequences are a valuable tool to predict the influence of climate change on weathering rates and on soil formation processes the baturite massif a humid enclave located in the brazilian semi arid region has unique characteristics that cause a disproportional distribution of rainfall the eastern and northern slopes receive more than 1 600 mm year of rainfall whereas the southern and western slopes have semi arid characteristics with rainfall of less than 600 mm year eight soil profiles were selected to investigate the influence of these distinct climates on soil formation to achieve this physical chemical morphological mineralogical and micromorphological data were determined and analyzed in the humid slope predominate soil processes include melanization brunification intense leaching acidification and alitization with intensified weathering in higher altitudes in contrast the environment in the dry slope favored the occurrence of soils with a higher base status high activity clays low al saturation and bisialitization processes coexisting with monosialitization mainly in the soils located at lower altitudes micromorphological data indicate that clay illuviation is not the main process responsible for the enrichment of clay in the subsurface horizons the contrasting environmental conditions with different mineralogical composition seem to be an important indicator of weathering intensity and pedoenvironmental conditions

application of laser ablation icp ms and traditional micromorphological techniques to the study of an alfisol sardinia italy in thin sections insights into trace element distribution abstract an innovative methodological approach is proposed in this study based on the chemical analysis of different portions of soil horizons illuvial pedofeatures pedogenic matrix and skeletal parent rock fragments by laser ablation inductively coupled plasma mass spectrometry la icp ms associated with traditional micromorphological optical and scanning electron microscopy techniques validation of the la icp ms technique provides in situ accurate and reproducible rsd 13 18 analysis of low concentration trace elements and rare earth elements ree in soil samples 0 001 0 1 ppm analyses were carried out on thin sections prepared from undisturbed soil samples collected from three different bt argillic i e clay illuviated horizons in an alfisol from the muravera area southeastern sardinia italy the main aims were i to develop and test the reliability of a la icp ms analytical method on soil thin sections and ii to explore the idea that concentrations of trace and rare earth elements in the different portions of a soil profile can be used to investigate their distribution as a response to pedogenetic processes the three horizons show similar features particularly in terms of element concentrations and patterns by comparing the concentration of ree and other trace elements in the clay coatings the soil matrix and the skeletal rock fragments in the same horizon a general enrichment trend is observed from the parent rock to the pedogenic matrix up to the illuvial pedofeatures suggesting a prominent role of pedogenetic processes in element fractionation and distribution during weathering in particular the highest concentration of trace elements and specifically ree in clay coatings which represent the most mobile solid phase in the soil profile indicates that the former can be used as a reliable indicator of soil weathering if a preliminary assessment of the presence of clay coatings is achieved in addition the discontinuous trend of some trace elements among soil features of different horizons is consistent with field evidence of slope dynamics marked by an erosive and depositional discontinuity along the soil profile

geomorphic inferences from regolith thickness chemical denudation and crn erosion rates near the glacial limit boulder creek catchment and vicinity colorado granitic regolith developed in the boulder creek catchment and adjacent areas records a history of deep weathering some of which may predate quaternary time field and well log measurements of weathering chemical denudation and rates of erosion derived from 10be cosmogenic radionuclide crn data help to quantify rates of landscape change in the post orogenic rocky mountains the density of oxidized fractured bedrock ranges from 2 7 to about 2 2 g cm 3 saprolite and grus have densities between 2 0 and 1 8 g cm 3 and 30 soil samples averaged 1 6 0 2 g cm 3 highly weathered regolith in 540 wells averages 3 3 m thick mean depth to bedrock in 1661 wells is 7 m and the weathered thickness exceeds 10 m in relatively large local areas east of the late pleistocene glacial limit thickness of regolith shows no simple relationship to rock type or structure local slope or distance from channels catchments in the vicinity of the boulder creek have an average crn erosion rate of 2 2 0 7 cm kyr 1 for the past 10 000 to 40 000 yr annual losses of cations and sio2 vary from about 2 to 5 g m 2 over a runoff range of 10 to nearly 160 cm using measured rates in simple box models shows that if a substantial fraction of void space is created by volume expansion in the weathering rock materials 7 m of weathered rock materials could form in as little as 230 kyr if density loss results mainly from chemical denudation and some volume expansion however the same weathering profile would take 1340 kyr to form rates of erosion measured by crn could be balanced by the rate of soil formation from saprolite if the annual solute loss from soil is 2 0 g m 2 and 70 of the density decrease from saprolite to grus and soil results from strain saprolite however forms from oxidized bedrock at a far slower rate and rates of saprolite formation cannot balance soil and grus losses to erosion the zone of thick weathered regolith is likely an eroding relict landscape the undulating surface marked by relatively low relief and tors is not literally a topographic surface of eocene oligocene or miocene age unless it was covered with deposits that were removed in pliocene or quaternary time

gneiss saprolite weathering and soil genesis along an east west regolith sequence ne brazil abstract the pressure to increase biomass production worldwide has pushed the boundaries of agricultural lands towards fragile soils this process is particularly intense in pernambuco state ne brazil pernambuco features a moisture gradient with soils developed from similar gneisses resistant structures within the rock influenced the internal movement and distribution of water consequently influencing regolith genesis this paper presents the mineralogical characteristics of three regolith profiles with shallow soils here assumed to be soils in which the top of the cr horizon is at a depth of 1 5 m or less along a transect at 8 s and discusses their weathering and pedogenetic processes samples were investigated via optical microscopy and scanning electron microscopy sem x ray diffraction xrd and total chemical analysis by inductively coupled plasma atomic emission spectrometry icp aes the presence of weathering resistant quartz veins and planes in the rock structure played a central role in controlling the water dynamics and the advancement of the weathering front therefore desilication was dominantly controlled by the pore network hence the weathering indexes did not differ appreciably among the climatic zones and both 1 1 and 2 1 type clays were found in all profiles although the amount of clay minerals that formed and the degree of dissolution of the primary minerals varied among the climate types from an agricultural perspective the thinness of these soil profiles and the presence of leucocratic layers are the main drawbacks of the regoliths whereas the capacity to supply plant nutrients via primary mineral dissolution near the root zone can be an advantage

deep weathering of granitic rocks a case of tunnelling in nw spain abstract this paper highlights a case of extensive development of saprolith from granitic bedrock in nw spain the weathering front at the study area extends to more than 250 m in depth the drilling of a railway tunnel madrid galicia high speed line through the bedrock and saprolith resulted in significant technical issues and economic losses cross sections revealing the 3d complexity of saprolith development are mainly based on fieldwork boreholes laboratory tests and the excavation works saprock is always observed overlying unweathered igneous bedrock two saprolite facies one clay rich and the other clay poor overlie the saprock the recognition is based on several criteria these deposits gradually thicken from the boundaries between the granitoid and metasedimentary roof pendants factors controlling saprolith development are discussed and the chemical and mineralogical changes and trends that occur are described variations in some geotechnical properties and the loss of quality of the rock masses from an engineering perspective are also quantified

weathering profiles in granitoid rocks of the sila massif uplands calabria southern italy new insights into their formation processes and rates abstract in this paper we characterized several weathering profiles developed on granitoid rocks in the sila massif upland calabria southern italy integrating detailed macro and micromorphological observations with physico mechanical field tests and petrographic mineralogical and geochemical analyses we focused our attention on the main weathering and pedogenetic processes trying to understand apparent discrepancies between weathering grade classes based on field description and geomechanical properties and two common weathering indices such as the micropetrographic index ip and the chemical index of alteration cia our results showed that sericite on plagioclase and biotite chloritization that represent inherited features formed during late stage hydrothermal alteration of granitoid rocks may cause an overestimation of the real degree of weathering of primary mineral grains under meteoric conditions especially in lower weathering grade classes moreover the frequent identification of fe mn oxides and clay coatings of illuvial origin rather than or in addition to those formed in situ both at the macro and microscale may also explain an overestimation of the weathering degree with respect to field based classifications finally some apparent inconsistencies between field geomechanical responses and chemical weathering were interpreted as related to physical weathering processes cryoclastism and thermoclastism that lead to rock breakdown even when chemical weathering is not well developed hence our study showed that particular caution is needed for evaluating weathering grades because traditional field and geochemical petrographic tools may be biased by inherited hydrothermal alteration physical weathering and illuvial processes on the basis of chronological constraints to soil formation obtained from a 42 ka old volcanic input mixed to granite parent materials detected in the soil cover of the sila massif upland a first attempt to estimate soil formation rates was achieved for different depths of corresponding weathering profile zones soil formation rates ranged from 0 01 0 07 mm a 1 for a and bw horizons weathering class vi to 0 04 0 36 mm a 1 for the underlying saprolite c and cr layers class v by comparing these results with the corresponding erosion rates available in the literature for the study area that range from

weathering and pedogenesis in the sila grande massif calabria south italy from field scale to micromorphology abstract weathering and soil features in the upland landscapes developed on granitic terrains of the sila grande massif calabria south italy have been studied in this work the attempt to link field scale and micromorphological observations in order to better understand the main weathering processes and their controlling factors is revealed to be very powerful six soil profiles in the area around the cecita lake representative of different geomorphological units were characterised by field work optical microscopy and sem eds analysis a strong influence on weathering and pedogenesis by micro scale features of primary minerals and parent rock fabrics is shown key roles are played also by relief in the development and preservation or stripping of regolith soil mantles in relation to natural and man induced phenomena by time controlling rates and degree of development of the main weathering features by climate in terms of type and intensity of dominant processes

mechanisms of granite alteration into grus karkonosze granite sw poland abstract granitic gruses are usually considered as a product of deep weathering but the influence of hydrothermal fluids was also noticed in this work a wide range of mineralogical and chemical methods performed on 43 samples from three representative outcrops and a reference site is used to determine the influence of hydrothermal and weathering fluids on the development of granitic gruses from the coarse grained karkonosze granite four types of altered granites have been distinguished including compact and friable granite typical grus and localized heavy altered zones mineralogical observations such as complete albitization of plagioclase and crystallization of secondary quartz revealed an important role of hydrothermal alteration at the early stage of grusification the origin of smectite and alteration of biotite into muscovite are likely to be connected with circulation of hydrothermal fluids too grusification sensu stricto was primarily caused by vermiculitization of biotite which resulted in volumetric expansion and the development of transmineral microcracks with non accordant pore surfaces thus it requires hydrothermal alteration to be relatively minor confined to postmagmatic changes since more advanced alteration of biotite into muscovite rather than vermiculite arrests further development of microcracks and leads to the development of friable granite

an unusual occurrence of probable pleistocene corestone within a cretaceous dioritic enclave peninsular ranges california abstract we here document an unusual occurrence of probable pleistocene corestone within an 5 m by 5 m dioritic enclave contained within a cretaceous tonalitic pluton santa margarita ecological reserve sw california the enclave lies within 3 5 km of the seismically active 1 5 2 ma elsinore fault zone and may have been subjected to 70 90 ground shaking events since 22 000 18 000 years ago the studied corestone is elliptical with major axis measuring 55 cm and minor axis 26 cm in length it is surrounded by a discontinuous 7 cm thick rind that breaks apart under slightly greater finger pressure than does the surrounding saprolite in order to assess changes in the physical and chemical properties of the corestone rind and saprolite we collected along an 66 5 cm long traverse 4 samples from the corestone 1 from the rind and 5 from the saprolite for bulk and grain density porosity and major and trace element analyses textural and clay mineral data along with the redistribution of elemental mass indicate that the weathering of biotite and to much lesser degrees apatite and the an rich cores of plagioclase played critical roles in the production of saprolite especially in a narrow 20 cm wide zone adjacent to the rind of the corestone within this zone bulk densities reach their minimum values while porosities and positive volume strains reach their maximums in addition the maximum loss of k fe mn and ca mass occurred just inside this region and is paralleled by the highest cia values and highest additions of si and rb mass in contrast the masses of na and sr are progressively increased and decreased respectively along the entire sampling traverse while the loss of mg ti and p mass is episodic with the greatest losses occurring within the narrow zone adjacent to the rind and at the end of the traverse the above observations indicate that the conversion of biotite to expandable mixed layered clay minerals aided by the alteration of the an rich cores of plagioclase produced sufficient stress on grain boundaries that a weakening or loss of intercrystalline cohesion occurred however unlike the well documented isovolumetric development of saprolite in other areas at the study site saprolitization was accompanied by a volume expansion we speculate that repeated ground shaking in response to earthquakes generated in the nearby elsinore fault zone may be responsible for this difference important byproducts of ground shaking would include additional weakening or loss of intercrystalline cohesion and the production and enhancement of new and older fluid pathways respectively the fact that the most intensely altered material at the study site lies adjacent to the boundary between the rind and saprolite suggests that this interface acted to guide fluid flow around the corestone and rind and into the adjacent saprolite where elemental mass was redistributed down various paths leading to the underlying water table most of the leached elemental mass was removed from the area of the sampling traverse but small increases in si rb and na mass suggest redistribution of these elements from elevated areas outside the area sampled during this study the result of the above complex set of processes is a variably porous and chemically altered saprolitic enclave that is still undergoing modification as it adjusts to the vicissitudes of the paralithic environment and continuing ground shaking during earthquakes generated along the elsinore fault

determination of natural and anthropogenic 129i in marine sediments sup 129 i concentrations in two sediment cores from the continental slope near cape hatteras were determined with tandem accelerator mass spectrometry tams the natural sup 129 i sup 127 i ratios in these cores are approximately 10 sup 12 the input of anthropogenic sup 129 i has increased this ratio to values close to 10 sup 10 at the surfacee of the sediments the observed natural level of sup 129 i is about two orders to magnitude above the current detection limit with tams which opens up to possibility for applications of sup 129 i in the marine system such as dating of sediments and crude oils and tracing of slow water movement in sediments

geophysical evidence for a pre impact sudbury dome southern superior province canada new filtering of aeromagnetic images of the sudbury area indicates the existence of a large elliptical feature that appears to underlie the deformed sudbury structure in the region of the exposed levack gneiss complex such that the two features have long axes which are significantly orthogonal to one another a north south oriented ellipse appears to be crosscut by that of the sudbury structure and does not correspond to known local lithological or structural trends the magnetic images combined with existing tectonic petrological geothermometric and geobarometric and geochronological data are used to suggest the existence of a pre impact crustal dome in the southernmost abitibi subprovince probably related to ca 2450 ma rifting and magmatism in the area this is consistent with existing petro logical and tectonic evidence from a variety of sources although the doming is itself unrelated to the ca 1850 ma sudbury event it may have affected the thermal regime existing at the time of impact which would have profound implications for the subsequent evolution of the sudbury igneous complex resume un nouveau filtrage d images aeromagnetiques de la region de sudbury montre l existence d un gros ele ment elliptique qui semble reposer sous la structure deformee de sudbury dans la region de l affleurement du complexe gneissique de levack les axes longs des deux elements sont relativement orthogonaux l un par rapport a l autre une ellipse orientee nord sud semble etre recoupee par l ellipse de la structure de sudbury et ne correspond pas a des ten dances structurales et lithologiques locales connues les images magnetiques combinees aux donnees tectoniques pe trologiques geothermometriques geobarometriques et geochronologiques existantes sont utilisees pour suggerer l existence d un dome crustal pre impact dans la partie la plus au sud de la sous province de l abitibi probablement relie au magnetisme et a la distension survenus dans la region il y a 2450 ma cela concorde avec les evidences pe trologiques et tectoniques existantes provenant de diverses sources bien que la croissance du dome ne soit pas en soi reliee a l evenement de sudbury 1850 ma cette croissance peut avoir affecte le regime thermique existant au moment de l impact ce qui aurait eu des implications profondes sur l evolution subsequente du complexe igne de sudbury traduit par la redaction prevec et al 9

deep weathering along a granite ridgeline in a subtropical climate abstract bulk chemical composition and mineralogy were examined in three soil profiles and a deeper 11 meter profile weathering on a granite ridgeline under subtropical climate conditions in south china the weathering sequence is delineated by mineralogy and major element variations apatite biotite hornblende and plagioclase dissolve early during weathering resulting in nearly 100 ca and na loss and significant mg fe and p depletion at depth the k feldspar reaction front begins at the depth of depletion of plagioclase leading to a loss of 80 of the k at the land surface near the bottom of the ridgeline and almost 100 at the top dissolution of quartz and other silicates releases about 60 of si in the profiles kaolinite is the dominant clay mineral and it transforms to gibbsite in the uppermost layer the soil horizon upper 100 cm is the zone dominated by pedogenic processes including active biological activity physical erosion and influx of high concentrations of atmospheric components especially co2 and o2 the pedogenic processes are characterized by low ph 4 54 to 5 85 high clay content kaolinite 6 16 wt gibbsite 2 8 wt and total organic carbon content 0 13 3 93 and intensive fracturing and dissolution of quartz and k feldspar compared with the lower horizons accumulation of organic material and resistant minerals downslope is attributed to down ridge movement of water termed here interflow and weathering products in the uppermost 100 cm down the ridgeline using a mass balance model calculation for the catena that assumes steady state soil thickness at all sites the bottom profile shows the highest apparent total chemical weathering loss rate 14 g m 2 y 1 whereas the middle position shows the highest physical erosion loss rate 44 g m 2 y 1 sio2 accounts for about 84 of the chemical weathering outflux from the soil horizons along the ridgeline hillslope chemical weathering rates at the bottom of the hillslope may be accelerated by high concentrations of organic material and by dissolution of kaolinite this study demonstrates that mineral reaction fronts in granite become separated over depth intervals of meters and that elemental fluxes and release mechanisms vary with position along a ridgeline catena

geochemical features of rocks stream sediments and soils of the fiume grande valley calabria italy the role of both natural weathering and anthropogenic pollution in controlling the distribution of major oxides and several trace elements in soils stream sediments and rocks of the fiume grande catchment was evaluated the contents of major oxides and trace elements in soils appear to be governed by weathering and pedogenetic processes although the use of fertilizers in agriculture could also partly affect k2o and p2o5 contents stream sediments have concentrations of major oxides except cao very similar to soils as relevant amounts of soil materials are supplied to the stream channels by erosive phenomena in contrast stream sediments have concentrations of cr co ni zn as and pb significantly higher than those of soils probably due to different conditions and rates of mobility of these elements within the three considered matrices and or disposal of wastes in the drainage network comparison of the concentrations of phes in soils with the maximum admissible contents established by the italian law shows that these limits are too restrictive in some cases and too permissive in other ones the approach of setting these limits with no consideration for the local geological geochemical framework may lead to improper management of the territory and its resources

natural iodine 129 as an environmental tracer abstract iodine 129 t 1 2 16 my is a naturally occurring tracer which can be used to study hydrologic and geologic processes on time scales up to 100 my the pre bomb atmospheric ratio 129 i i should have been constant in time and space and is the starting value in ground water recharge subsequent ratio changes in ground water should be determined by isotope contributions from three sources recharge water iodine leached from the formation and in situ uranium fission the mathematical expression of these time dependent processes forms the basis for dating and tracing applications the expected behavior of natural 129i in ground water is compared to results from field studies ground water samples from the great artesian basin australia provide an estimate of the atmospheric equilibrium ratio 6 10 13 down gradient changes in water up to 1 my old suggest that subsurface production can be significant the usefulness of 129i as an indicator of brine source and age is verified in brines collected in and around louisiana salt domes the method leads to ages of 7 and 9 my for two brine pockets trapped within jurassic salt and 32 to 40 my for oil field brines in miocene sands adjacent to the domes the results demonstrate the capability of tandem accelerator mass spectrometry to measure as few as 107 atoms of 129i in 10 mg i with 10 precision although such atom sensitivity can be achieved otherwise the accelerator technique is necessary to measure naturally low pre 1945 cosmogenic isotope ratios

lithologic control on soil texture heterogeneity abstract parent material is a soil forming factor which specially in temperate climates influences soil hydraulic properties as direct measurements of the soil hydraulic properties are laborious time consuming and expensive this work explores the influence of geological material on soil hydraulic properties using the balanced entropy index bei as a particle size distribution descriptor which was shown to be useful in the estimation of soil water retention properties the studied geological materials correspond to the phyllites quartz phyllites metagreywackes quartzites schists and granites in the northern part of portugal the source of information used to carry out this study was the soil map of the studied region scale 1 25 000 non parametric kruskal wallis tests followed by multiple comparisons between pairs of group medians using bonferroni significant differences bsd were applied to determine if soil texture heterogeneity measured using the bei significantly varied between the lithological groups under study results clearly show how the type of rock controls the bei of the overlying soils in the studied area further implications of this result are discussed in the text

prehistoric dark soils sediments of central sudan case study from the mesolithic landscape at the sixth nile cataract the so called lake or swampy dark colored deposits along or to the west of both the white and main niles which were not historically inundated by the nile as a whole have been recorded recently in association with mesolithic occupation what are the possible formation processes of these deposits and what is their potential for understanding the environmental record in relation to mesolithic occupation new insight into this issue might be brought to the forefront by the findings in the rocky cities area at the south western edge of jebel sabaloka by the sixth nile cataract in central sudan the study deposits were evaluated in terms of sedimentology micromorphology chemical composition grain size and magnetic parameters the properties detected in the study section correspond to no less than three different phases of development the lowermost part represents a saprolite horizon of granitic rocks exposed to weathering during the wet period which resulted in alkaline conditions 1st phase of formation process the occurrence of shells of bulinus forskalii retrieved from the uppermost layer suggests that there was an anoxic environment in the past which may be linked to the conditions of the present day sahel and subsequent attraction of this area for occupation during the mesolithic period deposition of the acidic colluvia from the surrounding granitic rocks in this environment resulted in post depositional processes involving fe and mn impregnation leading to the black coloring 2nd phase of the formation process the third phase of the formation processes is connected with the development of recent aridisols

the historical development of the magnetic method in exploration the magnetic method perhaps the oldest of geophysical exploration techniques blossomed after the advent of airborne surveys in world war ii with improvements in instrumentation navigation and platform compensation it is now possible to map the entire crustal section at a variety of scales from strongly magnetic basement at regional scale to weakly magnetic sedimentary contacts at local scale methods of data filtering display and interpretation have also advanced especially with the availability of low cost high performance personal computers and color raster graphics the magnetic method is the primary exploration tool in the search for minerals in other arenas the magnetic method has evolved from its sole use for mapping basement structure to include a wide range of new applications such as locating intrasedimentary faults defining subtle lithologic contacts mapping salt domes in weakly magnetic sediments and better defining targets through 3d inversion these new applications have increased the method s utility in all realms of exploration in the search for minerals oil and gas geothermal resources and groundwater and for a variety of other purposes such as natural hazards assessment mapping impact structures and engineering and environmental studies

129i and 36cl concentrations in waters of the eastern clear lake area california residence times and source ages of hydrothermal fluids abstract the clear lake area of northern california is the location of hot spring activity some of which is associated with the formation of au and hg deposits we measured 129 i i and 36 cl cl ratios in nine warm springs formation springs six cold springs with elevated levels of cl and i mineral springs and five springs of recent meteoric origin dating of the i in the formation waters indicated that sources of i in these waters are formations with minimum ages between 60 and 80 ma this age range is in good agreement with the ages of the franciscan complex and the great valley sequence the dominant formations in this area because the mineral waters are essentially formation waters diluted with meteoric water i in these waters is of the same origin residence times of the waters were calculated based on the build up of129i and 36cl as a consequence of the presence of u and th in the crust the residence time of the formation waters in the great valley sequence the location for most of these springs was probably not longer than 84 000 yr the concentrations found for 36cl and 129i in the mineral waters indicate that these waters have residence times of similar magnitude in formations such as the franciscan complex or the clear lake volcanics which have slightly higher levels of u and th than the great valley sequence