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

relation between soil age and silicate weathering rates determined from the chemical evolution of a glacial chronosequence long term weathering rates rlt were determined from base cation depletion in soil profiles developed on six granitic glacial moraines varying in age from 0 4 to 297 ka in the wind river mountains wyoming weathering rates were found to decrease with soil age t according to the power law equation rlt 15 t 0 71 where rlt is in meq m 2 yr 1 and t is in ka comparable data from the literature are consistent with this function and it is similar to power law equations describing changes in laboratory weathering rates with time on the basis of our study we predict that for a catchment unaffected by anthropogenic inputs and in a steady state with respect to the organic and cation exchange pools rlt should be higher than present day weathering rates derived from stream fluxes rpd by a factor of about 3 4

soil profiles as indicators of mineral weathering rates and organic interactions for a pennsylvania diabase abstract basaltic bedrock dissolves quickly and its weathering rate is therefore important towards controlling the composition of natural waters soil formation and co 2 concentrations in the atmosphere despite its importance however few reports of basalt or diabase and gabbro weathering rates exist in the literature and most have been measured in laboratory dissolution experiments or based on watershed studies here using elemental profiles measured through regolith on a jurassic diabase dike in south central pennsylvania we calculate time integrated log dissolution rates mol m 2 s 1 of the primary minerals plagioclase 14 9 s 1 and augite 14 8 and of smectite 17 6 a secondary clay mineral formed in the soil characteristic patterns in elemental profiles are consistent with preserved signatures of corestone formation elemental and mineral signatures of the soils relative to the parent rock are compared to predictions from citrate containing basalt column dissolution experiments depletion of apatite and of al fe mn ti p y ni cr sc v ga cu zn and la are observed in the upper meter of the profile relative to the parent rock

the illusion of diffusion field evidence for depth dependent sediment transport soil covered upland landscapes are common in much of the habitable world and our understanding of their evolution as a function of different climatic tectonic and geologic regimes is important across a wide range of disciplines erosion laws direct quantitative study of the processes shaping earth s surface and form the basis of landscape evolution modeling but are based on limited field data here we use in situ produced cosmogenic 1 0 be and 2 6 al concentrations from granitic saprolite to quantify an exponential decline in soil production with increasing soil thickness for a new field site in point reyes california results are similar to soil production functions from two different previously studied field sites and are used with extensive measurements of soil thickness to quantify depth integrated sediment transport flux plots of calculated sediment fluxes against the product of soil depth and hillslope gradient provide the first field based evidence that soil transport is a nonlinear depth dependent function data from all sites suggest that the widely used linear diffusion equation is only appropriate for shallow gradient convex up regions while the depth dependent transport law is more broadly applicable quantifying both the mobile soil thickness and landscape morphology is therefore critical to understanding how landscapes evolve

a simple geomorphic based analytical model for predicting the spatial distribution of soil thickness in headwater hillslopes and catchments 1 soil thickness acts as an important control for headwater hydrologic processes yet its spatial distribution remains one of the least understood in catchment hydrology analytic methods are desirable to provide a simple way for predicting soil thickness distribution over a hillslope or a catchment in this paper a simple geomorphic based analytical model is derived from the dynamic equations of soil thickness evolution in areas with no tectonic uplift or lowering since the recent geological past the model employs terrain attributes slope gradient curvature and upstream contributing area as inputs on grid based dems for predicting soil thickness evolution over time the analytic model is validated first on nine abstract hillslopes through comparing 10 kyr simulation results between our proposed model and the numerical solution the model is then applied to predict soil thickness evolution over 13 kyr in the 7 9 ha shale hills catchment one of the critical zone observatories in the u s located in central pennsylvania field observed and model predicted values of soil thickness are in good agreement with a root mean squared error of 0 39 m r2 0 74 and absolute errors 0 10 m in 70 of 106 sample points moreover our model verifies that terrain shape and position are the first order control on soil thickness evolution in the headwater catchment therefore the derived geomorphic based analytical model can be helpful in understanding soil thickness change over geological time and is useful as a simple tool for deriving spatially distributed soil thickness needed for hydrologic modeling

low temperature aqueous alteration of basalt mineral assemblages of deccan basalts and implications for mars spectra of basalt samples were dominated by fe 2 crystal field transitions with weak alteration bands near 1 4 and or 1 9 mm reststrahlen bands in mid infrared showed the convolution of plagioclase and pyroxene features typical of basalts saprolite samples were incompletely leached and their spectra were dominated by complex al and fe mg bearing smectite clays and retained no original mafic signatures xrd and mossbauer detected pyroxene and plagioclase not visible by reflectance spectroscopy in some saprolite samples zeolites were present throughout the saprolite the laterite was the most leached horizon and all analyses showed kaolinite and iron oxide assemblages this kaolinite and hematite association would be expected if kaolinite on mars formed through leaching under conditions similar to those on earth and has implications for abundant freshwater on the martian surface

dual phase mass balance modeling of small mineral particle losses from sedimentary rock derived soils abstract losses of small mineral particles can be a significant physical process that affects the elemental composition of soils derived from sedimentary rocks shales in particular contain abundant clay sized minerals that can be mobilized by simple disaggregation and solutional weathering is limited because the parent rock is composed primarily of recalcitrant minerals previously subjected to continental weathering here the dual phase mass balance model is employed to quantify losses of small mineral particles as water dispersible colloids wdcs from three previously studied soil profiles along a hill slope at the susquehanna shale hills critical zone observatory ssho wdcs were isolated from soil in the laboratory to determine their mineralogical and elemental compositions clay minerals dominated wdcs including illite vermiculite and chlorite inherited from the parent shale along with neoformed kaolinite quartz present in bulk soil was generally excluded from wdcs elements of low solubility and or bound in recalcitrant forms like rb in illite were employed in tracer ratios in the dual phase model aluminum ga and rb were enriched in wdcs and zr and hf were partially excluded six different combinations of elements into tracer ratios al zr ga zr rb zr al hf ga hf rb hf each yielded similar model results mass losses of wdcs were large ranging from 68 7 to 15 5 relative to soil parent material in different parts of the profiles mass losses via solution were smaller ranging from 7 2 to a gain of 6 1 in part of one profile losses of wdcs account for 90 of total mass loss surpassing chemical dissolution and therefore dominate the weathering portion of denudation at ssho zirconium concentrations were 97 158 ppm in the generally 1 m wdcs suggesting colloidal zr bearing phases model quantified losses of zr via wdcs were large with a median loss of 41 relative to parent material such losses indicate systematic underestimates of weathering by traditional mass balance that uses zr as an index element losses of ca mg and k via wdcs exceeded losses via solution countering assumptions of base cation losses primarily via mineral dissolution the results illustrate a geochemical fingerprint of physical weathering and the ability of the dual phase model to quantify that weathering process

87sr 86sr ca sr and ge si ratios as tracers of solute sources and biogeochemical cycling at a temperate forested shale catchment central pennsylvania usa plant uptake and biological cycling processes are commonly the largest flux of nutrients in terrestrial ecosystems hydrologic and other losses are offset by inputs from atmospheric deposition and weathering this multi tracer study investigates these effects using 87sr 86sr ca sr and ge si ratios from solid soil profiles and bedrock biological leaves and sap waters and water pore ground stream waters samples to study ca sr ge and si sources and cycling in a forest catchment underlying gray shale in the temperate climate of central pennsylvania leaves and sap waters were found to have similar ge si ratios 1 mol mol which is consistent with biological fractionation occurring at the root soil water interface ge si ratios in soil porewaters were higher near the surface and increased over the growing season suggesting plant preferential uptake of si over ge ca sr ratios in oak leaves 1360 40 mol mol were significantly higher than those in maple leaves 650 20 mol mol ca sr ratios were also generally higher in leaves than in sap waters which are consistent with preferential sr adsorption or sr uptake during transpiration 87sr 86sr ratios in both leaves and sap waters were similar for a given site implying that trees access similar pools of sr and ca although there are site to site differences additionally 87sr 86sr ratios in plant tissues were most similar to shallow pore waters 0 50 cm suggesting that mineral nutrients are obtained by trees from the near sub surface 87sr 86sr ratios in soil solutions from ridgetop and swale sites are best explained by mixing sr derived from shale and atmospheric deposition valley bottom soil reservoirs and stream and groundwater samples include sr and ca derived from dissolution of two isotopically distinct generations of carbonates a preliminary estimate of the sr and ca stream fluxes and isotopic mass balances imply propagation of a carbonate weathering front of ca 300 m myr 1 a value larger than previously reported for regolith weathering advance rates calculated based on cosmogenic nuclides and u series isotopes the data for ca sr si and ge in soil soil solutions and stream waters reflect the interaction of slower weathering processes with rapid biologically driven cycling between soils and biomass

weathering of rock to regolith the activity of deep roots in bedrock fractures abstract many areas in the world are characterized by shallow soils underlain by weathered bedrock but root rock interactions and their implications for regolith weathering are poorly understood to test the role of tree roots in weathering bedrock we excavated four pits along a catena in a shale dominated catchment at the susquehanna shale hills critical zone observatory sshczo in central pennsylvania we measured a variety of biological physical and chemical properties including 1 root density distribution and respiration 2 soil gas and 3 elemental compositions mineralogy and morphology of soil rock and rock fracture fill at ridge top mid slope toe slope and valley floor sites as expected root density declined rapidly with depth nevertheless fine roots were present in rock fractures even in the deepest least weathered shale sampled 180 cm below the land surface root densities in shale fractures were comparable between the ridge top and mid slope pits however they were significantly lower in the toe slope despite increasing rock fracture densities which is likely due to a shallower water table depth at the downslope site average root respiration per mass of dry root tissue in rock fractures was comparable to rates in the soil thus the total flux of co2 from root respiration tracked root densities decreasing with depth potential microbial respiration estimated as the laboratory c mineralization potential was about an order of magnitude lower than measured root respiration in both the soil and shale fractures roots were only observed in large aperture 50 m shale fractures that were filled with particulate material the fill in these fractures was mineralogically and geochemically similar to the lowest soil horizons with respect to clay composition element mobility extractable dissolved organic c doc inorganic n species and potentially mineralizable c and n while total c and total n values for the fracture fill were similar to the shale bedrock in the bulk soil depletion profiles al fe k mg and si relative to unweathered shale reflected characteristic weathering of illite and vermiculized chlorite to kaolinite and are similar between soils and fracture fill such similarities indicate that the fracture coatings are likely the result of pedogenic processes that occur at depth in the fractures rather than translocation of soil particles downward into the fractures overall our data suggest that roots and fill in shale fractures down to 180 cm are qualitatively similar to those in surface soil horizons thus the deepest manifestation of the chemical depletion profiles observed in the pits consists of the rock fracture fill and this fill is present at low concentrations with similarly low concentrations of fine roots

chemical weathering of a marine terrace chronosequence santa cruz california i interpreting rates and controls based on soil concentration depth profiles abstract the spatial and temporal changes in element and mineral concentrations in regolith profiles in a chronosequence developed on marine terraces along coastal california are interpreted in terms of chemical weathering rates and processes in regoliths up to 15 m deep and 226 kyrs old quartz normalized mass transfer coefficients indicate non stoichiometric preferential release of sr ca na from plagioclase along with lesser amounts of k rb and ba derived from k feldspar smectite weathering results in the loss of mg and concurrent incorporation of al and fe into secondary kaolinite and fe oxides in shallow argillic horizons elemental losses from weathering of the santa cruz terraces fall within the range of those for other marine terraces along the pacific coast of north america residual amounts of plagioclase and k feldspar decrease with terrace depth and increasing age the gradient of the weathering profile bs is defined by the ratio of the weathering rate r to the velocity at which the profile penetrates into the protolith a spreadsheet calculator further refines profile geometries demonstrating that the non linear regions at low residual feldspar concentrations at shallow depth are dominated by exponential changes in mineral surface to volume ratios and at high residual feldspar concentrations at greater depth by the approach to thermodynamic saturation these parameters are of secondary importance to the fluid flux qh which in thermodynamically saturated pore water controls the weathering velocity and mineral losses from the profiles long term fluid fluxes required to reproduce the feldspar weathering profiles are in agreement with contemporary values based on solute cl balances qh 0 025 0 17 m yr 1 during saturation controlled and solute limited weathering the greater loss of plagioclase relative to k feldspar is dependent on the large difference in their respective solubilities instead of the small difference between their respective reaction kinetics the steady state weathering rate under such conditions is defined as r q h m sol m total 1 s v b s the product of qh and the ratio of solubilized to solid state feldspar msat mtotal define the weathering velocity the weathering gradient bs reflects the kinetic rate of reaction where sv is the volumetric surface area of the residual feldspar both this rate expression and the spreadsheet calculations produce similar plagioclase weathering rates r 5 14 10 16 mol m 2 s 1 which agree with those reported for other environments of comparable climate and age weathering dependent concentration profiles are commonly described in literature the present paper provides methods by which these data can yield a more fundamental understanding of the weathering processes involved

glacial and periglacial erosion of the appalachians abstract the marine 18 o record indicates that the first ice advance into the appalachians equivalent to that of the late wisconsin occurred in the pliocene at about 2 4 ma only periodic localized glacial and periglacial activity occurred in the northern appalachians from 2 33 to 0 85 ma after 0 85 ma middle to late pleistocene eight out of ten glaciations covered the northern appalachians and brought periglacial conditions to the southern appalachians during the last 850 000 years glaciation extended to the late wisconsin limit within the appalachians for 15 of the time and extended to the early wisconsin limit just north of the appalachians for 25 of the time pleistocene glacial erosion of the appalachians of 120 200 m is necessary to account for the estimated volume of pleistocene ocean sediment derived from the appalachians and the estimated volume of pliocene pleistocene glaciogenic ocean sediment derived from the entire laurentide ice sheet this amount of glacial erosion occurring over the maximum expectable duration of pliocene pleistocene ice cover of 247 000 years yields glacial erosion rates from 0 5 0 8 m ka 1 such depths of erosion by thick warm based ice streams were localized in the lowlands and estuaries of the northern appalachians in the maritimes the presence of thin cold based ice caused minimal erosion of uplands periglacial landforms and tundra boreal forest were distributed throughout the appalachian highlands and the northern coastal plain during the glacial maxima periglacial erosion of 0 15 0 30 m ka 1 near the ice in pennsylvania decline to 0 1 0 2 m ka 1 in the southern piedmont each cold period almost completely renewed the regolith by eroding slopes and filling valleys the cumulative effect of the eight to ten major cold events could have produced as much as a few ten s of meters of periglacial ridge top lowering during the pleistocene both estimated glacial and periglacial erosion rates greatly exceed estimated current fluvial erosion rates therefore glacial and periglacial processes should be considered the dominant processes in shaping the present appalachian landscape the northern appalachians may be evolving towards a form where the landscape provides just the shape necessary to permit the least work conveyance of the ice across the region during glacial maxima the southern appalachians may be evolving towards a form where the landscape provides just the hillslope form necessary to transport the debris provided by periglacial conditions

fast but spatially scattered smectite formation in the proglacial area morteratsch an evaluation using gis proglacial areas in the alps usually cover a time span of deglaciation of about 150 years time since the end of the little ice age in the 1850s in these proglacial areas soils have started to develop due to the continuous retreat of the morteratsch glacier swiss alps the corresponding proglacial area offers a continuous time sequence from 0 to 150 year old surfaces furthermore an optimal digital dataset about the development of vegetation and soils is available for this area the soils have been developing on glacial till having a granitoidic character we investigated the clay mineral assemblage at 35 sites within the glacier forefield smectite can be used as a proxy for weathering intensity in these environments in the proglacial area the smectite concentration in the topsoil steadily increased with time of weathering however this development displayed a strongly scattered trend the complex interplay of biological physical and chemical processes in pedogenesis and clay mineral evolution limits our ability to predict and interpret landscape dynamics we consequently tried to analyse the role of topographic and vegetation modifications on the smectite content sites not or only slightly prone to erosion flattening slope ridge steepening slope ridge or flat morphology promoted the formation of smectite in addition the texture of the soil material influenced soil moisture and hence the degree of weathering and the development of vegetation although vegetation is not a fully independent factor because it is interrelated to the surrounding environmental conditions it seemed to exert its influence on weathering and consequently the formation of smectite green alder stands and grass heath where moister soils develop that have a finer texture or where more organic acids are produced were correlated with a higher smectite content humus forms serve as a proxy for the soil biota and soil organic matter composition at sites having a eumoder and a higher soil organic matter content the smectite concentration was elevated at these sites the production of chelating compounds or organic acids in the soil is believed to promote the development of smectites via an intermediate stage of hydroxy interlayered minerals and the subsequent removal of the hydroxide polymers in this work we have demonstrated that the topographic signature and the effect of vegetation on the formation of smectite and consequent weathering are pervasive our results will serve as a basis for further spatio temporal modelling

regolith production and chemical weathering of granitic rocks in central chile abstract we have evaluated the long term chemical and physical weathering mass balance of an anomalously thick saprolite profile 30 m thickness developed in granitic rocks near curacavi coastal range of central chile the results of geochemical mass balance calculations for the regolith profile point to a moderate depletion for na and sr due to the plagioclase dissolution and precipitation of kaolinite furthermore silicon shows a predominantly constant behaviour along the profile that is indicative of incongruent weathering of plagioclase strongly suggesting that quartz dissolution conditions are not reached in addition low depletion of k mg ca rb and ba in the saprolite indicates a low degree of k feldspar biotite and hornblende weathering denudation rates calculated using cosmogenic 10be data range from 20 to 70 m ma if the saprolite thickness has reached a steady state condition the reported denudation rates lead to mineral residence times in the upper part of the saprolite profile of about 0 5 to 1 8 ma with such duration a higher weathering degree than observed at curacavi would be expected this apparent contradiction might be explained if all of the weatherable plagioclase has been dissolved under the present day precipitation and temperature conditions of the curacavi region therefore we propose that the curacavi profile could be in local equilibrium with respect to the weatherable fraction of plagioclase a local equilibrium regime may be reached when the overall degree of depletion is small in a weathering profile uniform elemental distribution and low weathering degree in the thick weathering profile at curacavi defy the traditional notion of weathering regimes and reveal the importance of exploratory studies in order to better understand weathering process in mediterranean and semi arid climate regions

post alleghanian unroofing history of the appalachian basin pennsylvania from apatite fission track analysis and thermal models results of apatite fission track analyses on 29 ordovician through permian sandstones from the appalachian basin in pennsylvania are presented ages range from 111 17 to 184 10 ma mean track lengths of 10 71 0 29 to 13 10 0 17 m with unimodal negatively skewed length distributions are indicative of slow cooling the data separate into two groups on an age versus mean length plot the younger group 111 144 ma is found in the structural depressions of the anthracite basin and the broad top basin and adjacent appalachian plateau the older group 144 184 ma is found in the structurally higher southwestern appalachian plateau and juniata culmination and adjacent central plateau fission track data suggest that the basin cooled slowly after the alleghanian orogeny with culminations cooling earlier than depressions cooling histories modeled from apatite fission track data with maximum temperatures constrained by vitrinite reflectance indicate cooling beginning soon after the alleghanian orogeny except in the juniata culmination which apparently experienced synorogenic cooling and unroofing during formation of the underlying duplex model cooling histories and available geologic information indicate that the foreland basin did not experience mesozoic reheating unroofing histories were modeled from fission track cooling histories using heat flow estimates and burial depths derived from vitrinite reflectance profiles the models suggest that the unroofing history of the appalachian basin in pennsylvania can be divided into three episodes an initial episode of relatively rapid cooling and unroofing late permian early jurassic is attributed to flexural rebound of the foreland in response to erosional removal of alleghanian topographic load initial unroofing rates are higher in eastern pennsylvania than in the west consistent with a flexural model an episode of little to no unroofing middle jurassic late oligocene began contemporaneously with the inception of drift at the atlantic continental margin at this time unloading of the orogen was replaced by subsidence and sedimentation on the new margin without flexural rebound the driving force for unroofing of the basin was removed and unroofing slowed greatly an episode of rapid unroofing over the full width of the basin occurred from the miocene to the present although the driving mechanism for unroofing at this time has not been identified it is consistent with increased sedimentation rates in the middle atlantic offshore basins for the same period

determining mineral weathering rates based on solid and solute weathering gradients and velocities application to biotite weathering in saprolites abstract chemical weathering gradients are defined by the changes in the measured elemental concentrations in solids and pore waters with depth in soils and regoliths an increase in the mineral weathering rate increases the change in these concentrations with depth while increases in the weathering velocity decrease the change the solid state weathering velocity is the rate at which the weathering front propagates through the regolith and the solute weathering velocity is equivalent to the rate of pore water infiltration these relationships provide a unifying approach to calculating both solid and solute weathering rates from the respective ratios of the weathering velocities and gradients contemporary weathering rates based on solute residence times can be directly compared to long term past weathering based on changes in regolith composition both rates incorporate identical parameters describing mineral abundance stoichiometry and surface area weathering gradients were used to calculate biotite weathering rates in saprolitic regoliths in the piedmont of northern georgia usa and in luquillo mountains of puerto rico solid state weathering gradients for mg and k at panola produced reaction rates of 3 to 6 10 17 mol m 2 s 1 for biotite faster weathering rates of 1 8 to 3 6 10 16 mol m 2 s 1 are calculated based on mg and k pore water gradients in the rio icacos regolith the relative rates are in agreement with a warmer and wetter tropical climate in puerto rico both natural rates are three to six orders of magnitude slower than reported experimental rates of biotite weathering

chemical weathering in a tropical watershed luquillo mountains puerto rico ii rate and mechanism of biotite weathering abstract samples of soil saprolite bedrock and porewater from a lower montane wet forest the luquillo experimental forest lef in puerto rico were studied to investigate the rates and mechanisms of biotite weathering the soil profile at the top of a ridge in the rio icacos watershed consists of a 50 100 cm thick layer of unstructured soil above a 600 800 cm thick saprolite developed on quartz diorite the only minerals present in significant concentration within the soil and saprolite are biotite quartz kaolinite and iron oxides biotite is the only primary silicate releasing significant k and mg to porewaters although biotite in samples of the quartz diorite bedrock is extensively chloritized chlorite is almost entirely absent in the saprolite phyllosilicates phyllosilicate grains are present as 200 1000 m wide books below about 50 cm depth x ray diffraction xrd and electron microprobe analyses indicate that the phyllosilicate grains contain a core of biotite surrounded by variable amounts of kaolinite lattice fringe images under transmission electron microscope tem show single layers of biotite altering to two layers of kaolinite suggesting dissolution of biotite and precipitation of kaolinite at discrete boundaries some single 14 a layers are also observed in the biotite under tem the degree of kaolinitization of individual phyllosilicate grains as observed by tem decreases with depth in the saprolite this tem work is the first such microstructural evidence of epitaxial growth of kaolinite onto biotite during alteration in low temperature environments the rate of release of mg in the profile calculated as a flux through the soil normalized per watershed land area is approximately 500 mol hectare 1 yr 1 1 6 10 9 molmg msoil 2 s 1 this rate is similar to the flux estimated from mg discharge out the rio icacos 1000 mol hectare 1 yr 1 or 3 5 10 9 molmg msoil 2 s 1 indicating that scaling up from the soil to the watershed is possible for mg release the rate of mg release from biotite normalized to brunauer emmett teller bet surface area is calculated using a mass balance equation which includes the density and volume of phyllosilicate grains porewater chemistry and flux and soil porosity the mean rates of biotite weathering calculated from k and mg release rates are approximately 6 and 11 10 16 molbiotite mbiotite 2 s 1 respectively significantly slower than laboratory rates 10 12 to 10 11 molbiotite mbiotite 2 s 1 the discrepancy in scaling down from the soil to the laboratory is probably explained by 1 differences in weathering mechanism between the two environments 2 higher solute concentrations in soil porewaters 3 loss of reactive surface area of biotite in the saprolite due to kaolinite and iron oxide coatings and or 4 unaccounted for heterogeneities in flow path through the soil

apatite fission track thermochronology of the pennsylvania appalachian basin thirty four apatite fission track apparent ages and twenty four track length distributions for ash bed samples from the valley and ridge province and upper devonian to upper pennsylvania sedimentary samples from the allegheny front and allegheny plateau of pennsylvania suggest that these regions represent different thermal uplift regimes as well as different structural provinces the valley and ridge province tioga and kalkberg ash bed samples yield apatite fission track apparent ages and track length distributions that indicate early post alleghanian 285 270 ma cooling and unroofing that began at 250 ma assuming a geothermal gradient of 25 c km 1 a burial depth of at least 3 4 km can be estimated for all the pennsylvania samples at the allegheny structural front and on the western allegheny plateau the apatite fission track apparent ages 150 ma and track length measurements indicate a late jurassic early cretaceous thermal event for these samples possibly resulting from a higher geothermal gradient coinciding with kimberlite intrusion at this time along the greene potter fault zone in northeast pennsylvania on the allegheny plateau the upper paleozoic sedimentary samples yield apatite fission track apparent ages 180 ma narrow track length distributions with long mean lengths 13 14 m and small standard deviations 1 3 m suggest rapid cooling from temperatures 110 c during the middle jurassic early cretaceous for this part of pennsylvania this is consistent with the suggested uplift history of the catskill mountain region in adjacent new york state

preliminary estimates of regolith generation and mobility in the susquehanna shale hills critical zone observatory pennsylvania using meteoric 10be abstract this study seeks to quantify the rate and timing of regolith generation in the critical zone at the susquehanna shale hills critical zone observatory ssho meteoric 10 be depth profiles were determined using measurements from 30 hillslope soil and bedrock core samples in an effort to constrain 10 be inventories the ssho is located in the temperate climate zone of central pennsylvania and comprises a first order watershed developed entirely on a fe rich organic poor silurian aged shale two major perturbations to the landscape have occurred at ssho in the geologically recent past including significant and sustained periglacial activity until after the retreat of the laurentide ice sheet 21 ka and deforestation during early colonial land use bulk soil samples n 16 were collected at three locations along a planar hillslope on the southern ridge of the catchment representing the ridge top mid slope and valley floor rock chip samples n 14 were also collected from a 24 m deep core drilled into the northern ridge top all meteoric 10 be concentration profiles show a declining trend with depth with most of the 10 be retained in the uppermost decimeters of the soil meteoric 10 be inventories are higher at the mid slope and valley floor sample sites at 3 71 0 02 10 10 at cm 2 and 3 69 0 02 10 10 at cm 2 than at the ridge top site 1 90 0 01 10 10 at cm 2 the 10 be inventory at the convex ridge top site implies a minimum residence time of 10 6 ka or if erosion is steady an erosion rate of 19 4 0 2 m my

pore scale heterogeneous reaction rates on a dissolving limestone surface abstract the rate at which limestone dissolves determines the resistance of buildings and monuments to weathering the efficiency of carbon capture in deep geological reservoirs and the processes by which soils rocks and landscapes form and evolve however the normalized rates of mineral dissolution measured in laboratory experiments are often found to be far greater than those measured in field settings here we use atomic force microscopy afm measurements to demonstrate experimentally that the rate of calcite dissolution within micron size pores at the surface of a limestone sample is much lower than the rate of dissolution in the surrounding calcite surface in addition we use numerical simulations to show that this difference cannot be explained using a simple diffusion surface reaction model we suggest that the observed heterogeneous reaction rates could instead be due to the elevated density of reactive high curvature features on the polished surface surrounding the pore these high curvature features can strongly affect local interfacial free energy making such surfaces more prone to dissolution as a result polished surfaces should be more reactive than pore surfaces that have effectively been smoothed during prolonged contact with natural fluids as rate experiments routinely use polished and powdered samples the results may help to explain the widely reported discrepancy between lab and field based dissolution rates

investigating the complex interface where bedrock transforms to regolith abstract the interface where bedrock transforms to regolith is not planar but rather has a roughness that varies with the scale of observation the complexity of this surface is manifested in both element depth and fragment size depth distributions and may sometimes be related to the longitudinal profiles of watershed streams the fractal nature of the bedrock regolith interface means that the interface has a thickness which is 20 m in two ridgetop examples from pennsylvania and puerto rico such weathering thicknesses modeled as a function of one dimensional fluid flow are affected by the balance between rates of weathering and erosion one dimensional models are consistent with weathering advance rates that vary with equilibrium solubility and porefluid velocities and not reaction kinetics however fluid flow is not strictly downward and one dimensional permeability of regolith changes as particle size and bulk density changes with depth thus both downward and lateral flow occurs especially at reaction fronts where reactions change permeability the rate of weathering advance is therefore affected by the 3 dimensional distribution of reaction zones that affect permeability across the watershed quantitative models of such phenomena over a range of spatial and temporal scales are needed

short term soil mixing quantified with fallout radionuclides soil mixing plays a significant role in contaminant transport carbon sequestration and landscape evolution yet the rates and driving mechanisms are poorly constrained here we use depth profiles and advection diffusion modeling of fallout nuclides to quantify differences in short term 7 be and weapons derived isotopes and quantify mixing with a steady state model of vertical 210 pb transport on a forested landscape in the bega valley in southeastern australia and on grasslands in marin county california where bioturbation is documented as the dominant sediment transport mechanism we calculate diffusion like mixing coefficients of 1 2 cm 2 yr 1 in montane forest soils of northern new england we observe little field evidence of short term mixing and find that the traditional advection diffusion model fails to describe 210 pb profiles because nuclide profiles here can be described with a simple model of litterfall organic matter decay and radioactive decay we argue that diffusion like processes are barely active on short time scales and that the advection diffusion model overestimates diffusion like transport while animal bioturbation and soil freezing cycles have little effect on the fate of elements in new england physical soil mixing drives transport at bega valley and marin county we suggest that the absence of soil stirring that we quantify in new england forests may explain the slow physical erosion here 0 2 cm k y relative to the actively bioturbated soils of bega valley and marin county 5 10 cm k y

storage and release of fossil organic carbon related to weathering of sedimentary rocks abstract the biogeochemical carbon cycle which plays an undeniable role in global climate change is defined both by the size of carbon reservoirs such as the atmosphere biomass soil and bedrock and the exchange between them of various mineral and organic carbon forms among these carbon forms fossil organic carbon foc i e the ancient organic matter stored in sedimentary rocks is widely observed in modern environments but is not included in the supergene carbon budget using a digitized map of the world and an existing model of co 2 consumption associated with rock weathering we establish the global distribution of foc stored in the first meter of sedimentary rocks and a first estimation of annual foc delivery to the modern environment resulting from chemical weathering of these rocks results are given for the world s 40 major river basins and extended to the entire continental surface with a mean value of 1100 10 9 t mainly controlled by shale distribution the global foc stock is significant and comparable to that of soil organic carbon 1500 10 9 t the annual chemical delivery of foc estimated at 43 10 6 t yr 1 and controlled by the areal distribution of shales and runoff is of the same order of magnitude as the foc output flux to oceans chemical weathering of bedrock within the amazon basin produces one quarter of the total global flux of foc derived from chemical weathering and thus is expected to govern foc release on a global scale these results raise important questions concerning the role of foc in the modern carbon cycle as well as the origin and the budget of carbon in soils and rivers

regolith evolution on the millennial timescale from combined u th ra isotopes and in situ cosmogenic 10be analysis in a weathering profile strengbach catchment france abstract u th ra disequilibria cosmogenic in situ 10be concentrations and major and trace element concentrations have been analyzed in a 2 m deep weathering profile sampled at the summit of the granitic strengbach catchment france the data have been used to independently estimate both the long term regolith production and denudation rates and the weathering and erosion rates modeling of the 238u 234u 230th 226ra disequilibrium variations in the lower part of the profile yields a regolith production rate of 12 4 mm kyr 30 10 t km2 yr while modeling of the high resolution 10be concentration profile leads to an exposure age of 19 7 2 2 kyr an inherited concentration of 15 000 1 000 at g in quartz and a mean denudation rate of 22 10 mm kyr 37 15 t km2 yr the consistency between production and denudation rates suggests that on a millennial timescale the regolith mass balance at the summit of the catchment is close to a steady state even if the watershed may have been impacted by quaternary climatic changes and by recent anthropogenic perturbations e g 20th century acid rain and recent afforestation efforts the results also indicate that physical erosion is likely the dominant long term process of regolith denudation in the catchment furthermore the comparison of the long term production and denudation rates and of weathering and erosion rates determined from the depth profile analyses with the current weathering and erosion rates estimated at the outlet of the watershed based on monitoring of the water chemistry and sediment fluxes suggests that physical erosion may have varied more than the chemical weathering flux during the last 150 kyr although very few other sites with u series in situ 10be and stream monitoring data are available for comparison the current data suggest that 1 the mass balance steady state of regolith might be commonly achieved in soil mantled landscapes and 2 physical erosion has varied much more than chemical weathering in mid mountain catchments over the last 10 150 kyr these results highlight the importance of the combined analysis of u series nuclides and in situ 10be in the same weathering profile for the determination of key geomorphic parameters which are important to constraining landscape stability and the responses of landscapes to natural or anthropogenic forcing

probing deep weathering in the shale hills critical zone observatory pennsylvania usa the hypothesis of nested chemical reaction fronts in the subsurface weathering is both an acid base and a redox reaction in which rocks are titrated by meteoric carbon dioxide co2 and oxygen o2 in general the depths of these weathering reactions are unknown to determine such depths cuttings of rose hill shale were investigated from one borehole from the ridge and four boreholes from the valley at the susquehanna shale hills observatory ssho pyrite concentrations are insignificant to depths of 23 m under the ridge and 8 9 m under the valley likewise carbonate concentrations are insignificant to 22 and 2 m respectively in addition a 5 6 m thick fractured layer directly beneath the land surface shows evidence for loss of illite chlorite and feldspar under the valley secondary carbonates may have precipited the limited number of boreholes and the tight folding make it impossible to prove that depth variations result from weathering instead of chemical heterogeneity within the parent shale however carbonate depletion coincides with the winter water table observed at 20 m ridge and 2 m depth valley it would be fortuitous if carbonate containing strata are found under ridge and valley only beneath the water table furthermore pyrite and carbonate react quickly and many deep reaction fronts for these minerals are described in the literature we propose that deep transport of o2 initiates weathering at ssho and many other localities because pyrite commonly oxidizes autocatalytically to acidify porewaters and open porosity according to this hypothesis the mineral distributions at ssho are nested reaction fronts that overprint protolith stratigraphy the fronts are hypothesized to lie subparallel to the land surface because o2 diffuses to the water table and causes oxidative dissolution of pyrite pyrite derived sulfuric acid h2so4 plus co2 also dissolve carbonates above the water table to understand how reaction fronts record long term coupling between erosion and weathering will require intensive mapping of the subsurface copyright 2013 john wiley sons ltd

impact of low denudation rates on soil chemical weathering intensity a multiproxy approach abstract quantifying the influence of denudation i e physical erosion and chemical weathering on soil weathering intensity is an important component for a comprehensive understanding of element biogeochemical cycles the relation between the weathering intensity and the denudation rate is not clear and requires further investigation in a variety of climatic and erosional settings here in the betic cordillera southern spain we assess the soil chemical weathering intensity with a multiproxy approach combining different indicators of chemical weathering of the soil the total reserve in bases trb the content in fe oxides the quartz and clay content the soil cation exchange capacity cec and the silicon si isotope composition of the clay sized fraction our multiproxy approach demonstrates that in this semi arid environment at low denudation rates an increasing denudation rate decreases the soil weathering intensity whereas si mobility remains limited our results converge with previous conclusions based on chemical mass balance methods in the same geological setting mass balance methods and particularly chemical depletion fractions cdf are based on the immobility of a refractory element commonly zirconium zr relative to major cations in soils interestingly our study suggests that a weathering index such as the trb may provide a useful complement to assess soil chemical weathering intensity in eroding landscapes where the application of chemical mass balances may be hampered by potential zr mobility in the soil or by heterogeneity of zr concentrations in the bedrock

fe cycling in the shale hills critical zone observatory pennsylvania an analysis of biogeochemical weathering and fe isotope fractionation abstract during weathering fe in primary minerals is solubilized by ligands and or reduced by bacteria and released into soil porewaters such fe is then removed or reprecipitated in soils to understand these processes we analyzed fe chemistry and isotopic composition in regolith of the shale hills watershed a critical zone observatory in central pennsylvania overlying iron rich shale of the rose hill formation elemental concentrations were measured in soil from a well drained catena on a planar hillslope on the south side of the catchment based upon x ray diffraction and bulk elemental data loss of fe commences as clay begins to weather 15 cm below the depth of auger refusal more fe iii was present than fe ii in all soil samples from the ridge top to the valley floor both total and ferrous iron are depleted from the land surface of catena soils relative to the bedrock loss of ferrous fe is attributed mostly to abiotic or biotic oxidation loss of fe is most likely due to transport of micron sized particles that are not sampled by porous cup lysimeters but which are sampled in stream and ground waters the isotopic compositions 56 fe relative to irmm 014 of bulk fe and 0 5 n hcl extracted fe operationally designed to remove amorphous fe oxyhydr oxides range between 0 3 and 0 3 with 56 fe bulk extractable values between 0 2 and 0 4 throughout the soils along the catena 56 fe signatures of both bulk fe and hcl extracted fe become isotopically lighter as the extent of weathering proceeds the isotopic trends are attributed to one of two proposed mechanisms one mechanism involves fe fractionation during mobilization of fe from the parent material due to either fe reduction or ligand promoted dissolution the other mechanism involves fractionation during immobilization of fe oxyhydr oxides if the latter mechanism is true then shale which comprises one quarter of continental rocks could be an important source of isotopically heavy fe for rivers

constitutive mass balance relations between chemical composition volume density porosity and strain in metasomatic hydrochemical systems results on weathering and pedogenesis relations characterizing the chemical physical and mechanical changes resulting from metasomatic hydrochemical processes are developed using mass balance models which formally link chemical composition to bulk density mineral density volumetric properties porosity and amount of deformation strain rigorous analysis of aqueous solute transport effects is then made possible in a variety of porous media flow environments including chemical weathering pedogenesis soil formation diagenesis ore deposition and enrichment and metamorphism application of these linear constitutive relations to chemical weathering profiles shows that immobile and locally mobile chemical elements with masses conserved on the scale of soil profiles can be accurately identified from analysis of appropriate data arrays and then used as natural geochemical tracers to infer the nature and extent of hydrochemical weathering processes and volume changes during pedogenesis assumptions commonly made in the past about the supposed immobility of certain elements e g ti and zr become unnecessary quantitative differentiation between the effects of residual and supergene fractionation is then easily made these methods are applied to ni rich laterites developed by weathering of ultramafic rocks showing that during ordinary residual enrichment ni is concentrated by as much as 4 protolith peridotite concentrations this occurs simply by silicate mineral dissolution and removal of chemical elements other than ni e g mg with a corresponding reduction in saprolite density and increase in bulk porosity without significant deformation in contrast laterites with mineable concentrations of ni which are similarly undeformed such as the nickel mountain mine in riddle oregon have experienced in addition to residual enrichment strong supergene enrichment by fractionation of ore elements between a leached zone from which ni is extracted and a complementary enriched zone positioned farther along the direction of ground water flow soil forming processes in podzol chronosequences developed on sandy beach terraces of the mendocino coast of california involved soil column collapse of 60 percent by dissolution of silicate minerals in the albic horizon of al and fe leaching and 70 percent dilation expansion in the overlying organic rich layer by root growth the amount of erosion based upon paleosurface reconstructions using the excess mass of fe al pb ga and cu in the zone of supergene enrichment spodic horizon below the ground water table indicates that subsurface erosion by dissolutional collapse is three times that of surficial erosion finally using published chemical data for ti zr and cr on major bauxite deposits in australia where erosion rates are thought to be low we infer that there may have been major amounts of dissolutional collapse to explain the upwards increase of detrital zircon and rutile in weathering profiles

mineral weathering and elemental transport during hillslope evolution at the susquehanna shale hills critical zone observatory located in the uplands of the valley and ridge physiographic province of pennsylvania the susquehanna shale hills critical zone observatory ssho is a tectonically quiescent first order catchment developed on shales of the silurian rose hill formation we used soil cores augered at the highest point of the watershed and along a subsurface water flowline on a planar hillslope to investigate mineral transformations and physical chemical weathering fluxes about 25 m of bedrock was also drilled to estimate parent composition depletion of carbonate at tens of meters of depth in bedrock may delineate a deep carbonate weathering front overlying this extending from 6 m below the bedrock soil interface up into the soil is the feldspar dissolution front in the soils depletion profiles for k mg si fe and al relative to the bedrock define the illite and chlorite reaction fronts when combined with a cosmogenic nuclide derived erosion rate on watershed sediments these depletion profiles are consistent with dissolution rates that are several orders of magnitudes slower for chlorite 1 5 10 17 mol m 2 s 1 and illite 2 9 10 17 mol m 2 s 1 than observed in the laboratory mineral reactions result in formation of vermiculite hydroxy interlayered vermiculite and minor kaolinite during weathering exchangeable divalent cations are replaced by al as soil ph decreases the losses of mg and k in the soils occur largely as solute fluxes in contrast losses of al and fe are mostly as downslope transport of fine particles physical erosion of bulk soils also occurs results from a steady state model demonstrate that physical erosion accounts for about half of the total denudation at the ridgetop and midslope positions chemical weathering losses of mg na and k are higher in the upslope positions likely because of the higher degree of chemical undersaturation in porewaters chemical weathering slows down in the valley floor and al and si even show net accumulation the simplest model for the hillslope that is consistent with all observations is a steady state clay weathering limited system where soil production rates decrease with increasing soil thickness

geochemical mass balances and weathering rates in forested watersheds of the southern blue ridge ii effects of botanical uptake terms abstract geochemical mass balance methods are commonly used in small watershed studies to estimate rates of primary mineral weathering and soil formation and the contribution of these processes to cation budgets nutrient cycling and landscape susceptibility to acid deposition many researchers employ the balance sheet approach a system of simultaneous linear equations with constant coefficients which represent the steady state behavior of the modelled system most workers also assume that the steady state assumption for the entire system means that botanical factors can be ignored in other words that there is no net elemental transfer between biomass and inorganic compartments of the system however the widely invoked assumption that biomass is at steady state is mathematically a second explicit assumption not a built in mathematical consequence of the assumption of overall steady state the common assumption that the biomass is necessarily at steady state in a steady state system ignores the possibility of uptake of elements into the forest biomass to quantify the implications of the separate mathematical assumptions weathering rates for seven forested watersheds in the southern blue ridge mountains are calculated twice once allowing for net element exchange with biomass and once assuming no net exchange with biomass our calculations show that misunderstanding the mathematical constraints which are built into the most widely used geochemical mass balance equations commonly causes errors underestimates of up to a factor of 4 in the calculated rates of mineral weathering and soil formation this problem is most pronounced for minerals which contain major nutrient elements and for rates calculated from mass balances of those nutrient elements

biogeochemical weathering of serpentinites an examination of incipient dissolution affecting serpentine soil formation abstract serpentinite rocks high in mg and trace elements including ni cr cd co cu and mn and low in nutrients such as ca k and p form serpentine soils with similar chemical properties resulting in chemically extreme environments for the biota that grow upon them the impact of parent material on soil characteristics is most important in young soils and therefore the incipient weathering of serpentinite rock likely has a strong effect on the development of serpentine soils and ecosystems additionally porosity generation is a crucial process in converting rock into a soil that can support vegetation here the important factors affecting the incipient weathering of serpentinite rock are examined at two sites in the klamath mountains california serpentinite derived soils and serpentinite rock cores were collected in depth profiles from each sampling location mineral dissolution in weathered serpentinite samples determined by scanning electron microscopy energy dispersive spectrometry electron microprobe analyses and synchrotron microxrd is consistent with the order from most weathered to least weathered fe rich pyroxene antigorite mg rich lizardite al rich lizardite these results suggest that the initial porosity formation within serpentinite rock impacting the formation of serpentine soil on which vegetation can exist is strongly affected both by the presence of non serpentine primary minerals as well as the composition of the serpentine minerals in particular the presence of ferrous fe appears to contribute to greater dissolution whereas the presence of al within the parent rock appears to contribute to greater stability iron oxidizing bacteria present at the soil rock interface have been shown in previous studies to contribute to the transition from rock to soil and soils and rock cores in this study were therefore tested for iron oxidizing bacteria the detection of biological iron oxidation in this study indicates that the early alteration of these fe rich minerals may be mediated by iron oxidizing bacteria these findings help provide insight into the incipient processes affecting serpentinite rock weathering important to the development of extreme serpentine soils and the biota that grow on them

coupling chemical weathering with soil production across soil mantled landscapes soil covered upland landscapes constitute a critical part of the habitable world our understanding of how they evolve as a function of different climatic tectonic and geological regimes is important across a wide range of disciplines and depends in part on understanding the links between chemical and physical weathering processes extensive previous work has shown that soil production rates decrease with increasing soil column thickness but chemical weathering rates were not measured here we examine a granitic soil mantled hillslope at point reyes california where soil production rates were determined using in situ produced cosmogenic nuclides 10be and 26al and we quantify the extent as well as the rates of chemical weathering of the saprolite from beneath soil from across the landscape we collected saprolite samples from the base of soil pits and analysed them for abrasion ph as well as for major and trace elements by x ray fluorescence spectroscopy and for clay mineralogy by x ray diffraction spectroscopy our results show for the first time that chemical weathering rates decrease with increasing soil thickness and account for 13 to 51 per cent of total denudation we also show that spatial variation in chemical weathering appears to be topographically controlled weathering rate decreases with slope across the divergent ridge and increases with upslope contributing area in the convergent swale furthermore to determine the best measure for the extent of saprolite weathering we compared four different chemical weathering indices the vogt ratio the chemical index of alteration cia parker s index and the silicon aluminium ratio with saprolite ph measurements of the cia were the most closely correlated with saprolite ph showing that weathering intensity decreases linearly with an increase in saprolite ph from 4 7 to almost 7 data presented here are among the first to couple directly rates of soil production and chemical weathering with how topography is likely to control weathering at a hillslope scale copyright 2006 john wiley sons ltd

climate dependence of feldspar weathering in shale soils along a latitudinal gradient although regolith the mantle of physically chemically and biologically altered material overlying bedrock covers much of earth s continents the rates and mechanisms of regolith formation are not well quantified without this knowledge predictions of the availability of soil to sustain earth s growing population are problematic to quantify the influence of climate on regolith formation a transect of study sites has been established on the same lithology silurian shale along a climatic gradient in the northern hemisphere as part of the susquehanna shale hills critical zone observatory pennsylvania usa the climate gradient is bounded by a cold wet end member in wales and a warm wet end member in puerto rico in between mean annual temperature mat and mean annual precipitation map increase to the south through new york pennsylvania virginia tennessee and alabama the site in puerto rico does not lie on the same shale formation as the appalachian sites but is similar in composition soils and rocks were sampled at geomorphologically similar ridgetop sites to compare and model shale weathering along the transect focusing on the low concentration non nutrient element na we observe that the extent and depth of na depletion is greater where mean annual temperature mat and precipitation map are higher na depletion a proxy for feldspar weathering is the deepest reaction documented in the augerable soil profiles this may therefore be the reaction that initiates the transformation of high bulk density bedrock to regolith of low bulk density based on the shale chemistry along the transect the time integrated na release rate qna increases exponentially as a function of mat and linearly with map ny the only site with shale till parent material is characterized by a qna that is 18 times faster than pa an observation which is attributed to the increased surface area of minerals due to grinding of the glacier and kinetically limited weathering in the north a calculated apparent arrhenius type temperature dependence across the transect excluding ny for the dissolution of feldspar na depletion is 99 15 kj mol 1 a value similar to field measured values of the activation energy 14 109 kj mol 1 or laboratory measured values of the enthalpy of the albite reaction 79 8 kj mol 1 observations from this transect document that weathering losses of na from silurian shale can be understood with models of regolith formation based on chemical and physical factors such that weathering progresses from kinetically limited sites wales to al to the transport limited site in puerto rico significant advances in our ability to predict regolith formation will be made as we apply more quantitative models to such transect studies on shales and other rocks types

processes that control mineral and element abundances in shales abstract a shale s composition can be used to infer physical chemical and biological processes that have acted on it over its life history and this knowledge is used to surmise conditions at the time when each process was active this review lists the most important processes that control shale mineral and element abundances during each of the five stages of its life history 1 during weathering transport and deposition the most important processes are chemical weathering hydraulic sorting and mixing adsorption reverse weathering and incorporation of organic matter and biominerals 2 during early diagenesis the most important processes are exchange across the water sediment interface compaction microbial respiration mineral transformations and concretion formation 3 during burial diagenesis the most important processes are compaction catagenesis and metagenesis and mineral transformations 4 during exhumation the most important processes are decompaction brine invasion groundwater penetration and microbial respiration 5 during weathering the most important processes are organic matter oxidation mineral oxidation and hydrolysis groundwater transport and disaggregation this classification of processes provides a way to envision how concurrent and consecutive processes that occurred over a shale s life history have affected its mineralogy and chemical composition

behavior of redox sensitive elements during weathering of granite in subtropical area using x ray absorption fine structure spectroscopy abstract the variation in chemical compositions of regolith along a weathering profile developed on a granite substrate in jiangxi province in southern china was investigated in this paper with the aim to characterize the speciation of redox sensitive elements and to evaluate their mobility and redistribution during chemical weathering mass balance calculations indicate titanium ti is the most immobile element in this weathering profile a new method x ray absorption fine structure xafs spectroscopy was used to determine the speciation of fe and mn along the profile fe k edge x ray absorption near edge structure xanes spectra show fe in saprolith is stabilized mainly in the state of fe iii suggesting fe is as immobile as conservative elements during granite weathering mn k edge xanes spectra show mn iii iv oxides are reduced to mn ii in surface soil where soil organic matter som acts as an important reductant although ce co and v were unable to be analysed by xafs their concentrations have significant correlations with that of mn indicating that the mobilization and redistribution of ce co and v may also be governed by redox condition all in all the results suggest that redox process impacts significantly on the redistribution of mn ce co and v along the profile the successful application of xafs in the study on migration of redox sensitive elements during granite chemical weathering has provided valuable information for the understanding and evaluating the geochemical behavior of elements in the environment

quantification of loss of calcite pyrite and organic matter due to weathering of toarcian black shales and effects on kerogen and bitumen characteristics abstract comparison of geochemical data on posidonia shale early toarcian from a shallow unweathered core and from adjacent weathered exposures of the same fades was performed results revealed that quantitatively the most affected petrographic constituent is pyrite and that organic matter and carbonate were also altered by weathering due to this process of weathering the bulk composition of organic matter especially the molecular composition of soluble organic matter and the fluorescence colour of organic particles are changed estimates of weathering rates reveal that the annual release of sulphur and organic carbon from black shales may significantly add to anthropogenic pollution

sorting and thickness of waste mantle material on a sandstone spur in central pennsylvania abstract utilizing a hammer seismograph and deep soil pits waste mantle material was studied on southwest and northwest aspects of a sandstone ridge in central pennsylvania soils on steep slope gradients 52 on both the sw and nw aspects showed preferred orientation of rock fragments in the direction of the slope aspect layers of 100 sorted and stratified rock fragments and an abrupt change from unconsolidated to underlying consolidated parent material soils on these sites were formed in waste mantle modified by periglacial denudation soils on lower slope gradients did not generally show preferred orientation of rock fragments but showed a gradual change from unconsolidated to consolidated bedrock parent material these sites were dominantly formed in residuum the upper 1 4 m across all sites were modified by periglacial denudation evidenced by lobate solifluction terraces and sub surface and surface rock sorting depth to bedrock ranged from 3 0 to 6 3 m across the srudy area and no strong trends with slope gradient or aspect were noted the differences found in the distribution and orientation of rock fragments and depth of unconsolidated parent materials may be best explained by deep weathering which occurred over many thousands of years followed by severe periglacial frost action and denudation during the last wisconsinan glacial advance steep slopes were eroded and material was deposited on them this material was derived from dominantly residual soil areas upslope with a lower slope gradient

the carbonate system geochemistry of shallow groundwater surface water systems in temperate glaciated watersheds michigan usa significance of open system dolomite weathering we present here a field geochemical study of controls on carbonate weathering within rapidly circulating shallow groundwater surface water systems in the glaciated mid continent region groundwaters and surface waters in three watersheds spanning the upper to lower peninsulas of michigan consist of ca 2 mg 2 hco 3 solutions derived from the open system dissolution of calcite and dolomite in soils developed on mixed mineralogy glacial drift the thermodynamic stabilities of calcite and dolomite both decrease with decreasing temperature with dolomite more strongly affected thus the low mean annual temperature of these temperate weathering environments maximizes the absolute solubility of dolomite as well as its solubility relative to calcite many groundwaters in the study area approach equilibrium with respect to the more soluble dolomite and are moderately supersaturated with respect to calcite groundwaters in each watershed have distinct and relatively narrow ranges of carbon dioxide partial pressure p co 2 values which increase significantly from north to south log p co 2 of 3 0 to 2 2 atm suggesting that there are landscape level differences in carbon transformation rates in soil weathering zones increases in weathering zone p co 2 values produce hco 3 concentrations that vary by a factor of five but the mg 2 ca 2 and mg 2 hco 3 ratios of all groundwaters are similar suggesting relatively constant weathering input ratios of calcite and dolomite although surface waters commonly are between 2 and 10 times supersaturated with respect to calcite the mg 2 hco 3 ratios of surface waters are very close to initial groundwater values suggesting that back precipitation of calcite is not a significant process in these systems the enhanced solubility of dolomite at low temperatures coupled with the landscape level differences in carbon cycling suggest that temperate zone weathering reactions in glaciated terrains are significant contributors to continent scale fluxes of both mg 2 and hco 3

rates and time scales of clay mineral formation by weathering in saprolitic regoliths of the southern appalachians from geochemical mass balance rates of clay formation in three watersheds located at the coweeta hydrologic laboratory western north carolina have been determined from solute flux based mass balance methods a system of mass balance equations with enough equations and unknowns to allow calculation of secondary mineral formation rates as well as the more commonly determined primary mineral dissolution rates was achieved by including rare earth elements ree in the mass balance rates of clay mineral formation determined by mass balance methods have been used to calculate the time needed for a 5 50 g kg 1 change in relative clay abundance in the saprolite at coweeta this corresponds to the response time of the clay mineral to for example a change in climate the 5 change in relative clay abundance is the smallest change that can generally be detected using x ray diffraction xrd response times range from tens of thousands to hundreds of thousands of years extrapolating the coweeta clay formation rates to other southern appalachian regoliths the time required to form measured clay abundances production times in eastern blue ridge and inner piedmont regolith have been calculated the production times of clay mineral assemblages range from 2 k y to 2 m y with mean values ranging from 50 k y to 1 m y the results of this study are consistent with the arguments of thiry 2000 1 that the best resolution of the paleoclimatic record in marine clay rich sediments and mudrocks is 1 or 2 m y 1 ref 107

a reactive transport model for marcellus shale weathering abstract shale formations account for 25 of the land surface globally and contribute a large proportion of the natural gas used in the united states one of the most productive shale gas formations is the marcellus a black shale that is rich in organic matter and pyrite as a first step toward understanding how marcellus shale interacts with water in the surface or deep subsurface we developed a reactive transport model to simulate shale weathering under ambient temperature and pressure conditions constrained by soil and water chemistry data the simulation was carried out for 10 000 years since deglaciation assuming bedrock weathering and soil genesis began after the last glacial maximum results indicate weathering was initiated by pyrite dissolution for the first 1000 years leading to low ph and enhanced dissolution of chlorite and precipitation of iron hydroxides after pyrite depletion chlorite dissolved slowly primarily facilitated by the presence of co2 and organic acids forming vermiculite as a secondary mineral a sensitivity analysis indicated that the most important controls on weathering include the presence of reactive gases co2 and o2 specific surface area and flow velocity of infiltrating meteoric water the soil chemistry and mineralogy data could not be reproduced without including the reactive gases for example pyrite remained in the soil even after 10 000 years if o2 was not continuously present in the soil column likewise chlorite remained abundant and porosity remained small if co2 was not present in the soil gas the field observations were only simulated successfully when the modeled specific surface areas of the reactive minerals were 1 3 orders of magnitude smaller than surface area values measured for powdered minerals small surface areas could be consistent with the lack of accessibility of some fluids to mineral surfaces due to surface coatings in addition some mineral surface is likely interacting only with equilibrated pore fluids an increase in the water infiltration rate enhanced weathering by removing dissolution products and maintaining far from equilibrium conditions we conclude from these observations that availability of reactive surface area and transport of h2o and gases are the most important factors affecting rates of marcellus shale weathering of the in the shallow subsurface this weathering study documents the utility of reactive transport modeling for complex subsurface processes such modelling could be extended to understand interactions between injected fluids and marcellus shale gas reservoirs at higher temperature pressure and salinity conditions

particle fluxes in groundwater change subsurface shale rock chemistry over geologic time abstract most models of landscape evolution posit that particles leave the land surface by physical weathering i e erosion and solutes leave the subsurface by chemical weathering they assume that erosion does not affect the rock and soil chemistry however in this study of a shale catchment we discovered that particles are mobilized out of soil and weathering rock and are transported through the subsurface resulting in changes in the rock and soil chemistry we studied the solute and particle fluxes during six storms in the susquehanna shale hills critical zone observatory in pennsylvania usa and compared those to the record in regolith chemistry the stream s suspended particles primarily consisted of platy shaped m sized illite commonly coated with patchy amorphous submicron sized al fe and si rich oxides the chemistry of the stream particles always differed from that of surface soils except during intense dry season rainstorms stream particles were chemically similar to the laboratory extracted soil colloids at high discharge but to groundwater particles at low discharge implying a central role of flow path variations in controlling subsurface particle transport zr was effectively immobile in shale hills regolith chemistry revealed that the cumulative effects of particle loss to depths of 5 8 m in the fractured bedrock zone were estimated to account for 58 of k and 24 of mg losses in shale landscapes we propose that subsurface particle transport must be considered in landscape evolution models as an important contributor to changes in rock and soil chemistry over geologic time periods

periglacial geomorphology of the appalachian highlands and interior highlands south of the glacial border a review abstract many features reported in the appalachian region have been assigned a paleoperiglacial origin based on field relationships and their similarities with analogs active in present day actuoperiglacial environments these forms include but are not limited to sorted and nonsorted varieties of patterned ground grezes litees block fields block slopes and block streams cryoplanation terraces and hillslope and river terrace landscapes although very small scale features generally less than 1 m in plan or section dimension and some larger forms on steep hillslopes are known to be at least sporadically active today the large scale features discussed here are interpreted as either inactive or truly fossil periglacial phenomena thus they hav implications for paleoclimatic reconstruction and significance as indicators of relative landscape stability since the time s of their development this paper briefly reviews the historical dimension of early researchs work present selected examples of recent results and gives authors conclusions

integration of geochemical mass balance with sediment transport to calculate rates of soil chemical weathering and transport on hillslopes 1 we developed a process oriented hillslope soil mass balance model that integrates chemical and physical processes within hillslope soils the model explicitly factors that soil chemical weathering at any hillslope position is related to the flux of soil eroded from upslope as well as soil production from underlying bedrock the model was merged with measurements of soil elemental chemistry and cosmogenic radionuclide based saprolite to soil conversion rates along a 50 m transect of a semiarid granodiorite hillslope in the southeastern australian highlands inverse modeling results in the simultaneous quantification of the rates of soil chemical weathering and soil transport as a function of hillslope position soil chemical weathering rates per land surface area systematically varied along the transect from losses of 0 035 kg m 2 yr 1 on the ridge to gains of 0 035 kg m 2 yr 1 at the lowest slope position the mass loss via soil chemical weathering would have been overestimated by 40 if the impact of soil transport on soil chemistry was ignored the chemical mobility of elements combined with biological nutrient demand controlled the spatial redistribution of individual elements p and ca were preferentially retained relative to si al and fe within the hillslope base the calculated soil transport rate is linearly related to the product of soil thickness and slope gradient instead of slope alone soil residence time was determined by calculating the time length for a 3 dimensional box volume 1 m2 surface area soil thickness to be entirely removed by mass flux of soil transport 4 ka on the ridge to 0 9 ka at the hillslope base these soil residence times combined with soil chemical weathering rates indicate that a 1 m2 area of soil loses 1 800 kg via chemical weathering while passing through the upslope portion of the hillslope but that it regains 90 kg probably via clay precipitation and biological retention of cations during its passage through the lower segments of the transect this study provides a previously unrecognized linkage between physical soil transport and soil chemical weathering that have implications for hillslope evolution as well as biogeochemistry

refractory element mobility in volcanic soils refractory trace element concentrations in strongly weathered hawaiian soils ranging in age from 20 to 4100 ka are highly elevated over parent rock values due to extensive mass loss of more soluble major elements during pedogenesis nb and ta exhibit virtually no mobility soil nb ta ratios are within the range of fresh bedrock even when soil nb concentrations are residually enriched by a factor of 10 in contrast al zr and hf are depleted relative to nb in surface soil horizons but are enriched at depth clearly indicating mobility of these elements variations in th nb ratios in soil profiles indicate significant th mobility within the soil column however mass balance calculations require that accretion of th enriched asian dust has resulted in a net increase in th in some soils soils developed on a 150 ka rainfall gradient show that the mobility and loss of zr increase with mean annual precipitation

chemical weathering rates of a soil chronosequence on granitic alluvium iii hydrochemical evolution and contemporary solute fluxes and rates although long term changes in solid state compositions of soil chronosequences have been extensively investigated this study presents the first detailed description of the concurrent hydrochemical evolution and contemporary weathering rates in such sequences the most direct linkage between weathering and hydrology over 3 million years of soil development in the merced chronosequence in central california relates decreasing permeability and increasing hydrologic heterogeneity to the development of secondary argillic horizons and silica duripans in a highly permeable younger soil 40 kyr old pore water solutes reflect seasonal to decadal scale variations in rainfall and evapotranspiration et this climate signal is strongly damped in less permeable older soils 250 to 600 kyr old where solutes increasingly reflect weathering inputs modified by heterogeneous flow elemental balances in the soils are described in terms of solid state exchange and pore water reservoirs and input output fluxes from precipitation et biomass solute discharge and weathering solute mineral nutrients are strongly dependent on biomass variations as evidenced by an apparent negative k weathering flux reflecting aggradation by grassland plants the ratios of solute na to other base cations progressively increase with soil age discharge fluxes of na and si when integrated over geologic time are comparable to solid state mass losses in the soils implying similar past weathering conditions similarities in solute and sorbed ca mg ratios reflect short term equilibrium with the exchange reservoir long term consistency in solute ratios when contrasted against progressive decreases in solid state ca mg requires an additional ca source probably from dry deposition amorphous silica precipitates from thermodynamically saturated pore waters during periods of high evapotranspiration and result in the formation of duripans in the oldest soils the degree of feldspar and secondary gibbsite and kaolinite saturation varies both spatially and temporally due to the seasonality of plant respired co2 and a decrease in organically complexed al in deeper pore waters k feldspar is in equilibrium and plagioclase is about an order of magnitude undersaturated hydrologic heterogeneity produces a range of weathering gradients that are constrained by solute distributions and matrix and macropore flow regimes plagioclase weathering rates based on precipitation corrected na gradients vary between 3 and 7 10 16 mol m 2 s 1 these rates are similar to previously determined solid state rates but are several orders of magnitude slower than for experimental plagioclase dissolution indicating strong inhibitions to natural weathering partly due to near equilibrium weathering reactions

the co2 consumption potential during gray shale weathering insights from the evolution of carbon isotopes in the susquehanna shale hills critical zone observatory abstract shale covers about 25 of the land surface and is therefore an important rock type that consumes co 2 during weathering we evaluated the potential of gray shale to take up co 2 from the atmosphere by investigating the evolution of dissolved inorganic carbon dic concentrations and its carbon isotopic ratio 13 c dic along water flow paths in a well characterized critical zone observatory susquehanna shale hills catchment in this catchment chemical weathering in shallow soils is dominated by clay transformation as no carbonates are present and soil pore waters are characterized by low dic and ph in shallow soil porewaters the dic dominated by dissolved co 2 is in chemical and isotopic equilibrium with co 2 in the soil atmosphere where pco 2 varies seasonally to as high as 40 times that of the atmosphere the degradation of ancient organic matter is negligible in contributing to soil co 2 the chemistry of groundwater varies along different flowpaths as soil pore water recharges to the water table and then dissolves ankerite or secondary calcite under the valley floor weathering of carbonate leads to much higher concentrations of dic 2500 mol l and divalent cations ca 2 and mg 2 in groundwaters than soil waters the depth to the ankerite weathering front is hypothesized to be roughly coincident with the water table but it varies due to heterogeneities in the protolith composition groundwater chemistry therefore shows different saturation indices with respect to ankerite depending upon location along the valley the 13 c dic values of these groundwaters document mixing between the ankerite and soil co 2 the major element concentrations dic and 13 c dic in the first order stream incising the valley of the catchment are derived from groundwater and soil waters in proportions that vary both spatially and temporally the co 2 degassed slightly in the stream but little evidence of c isotopic equilibration with the atmosphere is observed due to the short length of the stream and short contact time with air the ankerite reaction front also lies close to the pyrite dissolution front pyrite oxidation in bedrock likely released sulfuric acid and played a minor role in the ankerite dissolution shifting groundwater 13 c dic slightly above the expected mixing values at the catchment scale the stream so 4 2 is also dominantly derived from wet deposition as stream has 34 s so4 values around 3 well within the range of acid deposition a mass balance calculation shows that silicate and ankerite dissolution of the rose hill shale at shale hills consumes co 2 at a rate of 44 and 42 48 mol m 2 ky 1 respectively while degradation of ancient organic matter releases co 2 at a rate of 1 3 mol m 2 ky 1 silicate dissolution at the shallow soils is facilitated by low ph and high soil pco 2 as ankerite dissolution and organic matter oxidation are shown to occur early during shale alteration co 2 consumption by shale weathering is thus limited by initiation of rock disintegration e g fractures and exposure of fresh surface area to infiltrating co 2 and o 2 rich water

the role of disseminated calcite in the chemical weathering of granitoid rocks accessory calcite present at concentrations between 300 and 3000 mg kg 1 occurs in fresh granitoid rocks sampled from the merced watershed in yosemite national park ca usa loch vale in rocky mountain national park co usa the panola watershed ga usa and the rio icacos puerto rico calcite occurs as fillings in microfractures as disseminated grains within the silicate matrix and as replacement of calcic cores in plagioclase flow through column experiments using de ionized water saturated with 0 05 atm co2 produced effluents from the fresh granitoid rocks that were dominated by ca and bicarbonate and thermodynamically saturated with calcite during reactions up to 1 7 yr calcite dissolution progressively decreased and was superceded by steady state dissolution of silicates principally biotite mass balance calculations indicate that most calcite had been removed during this time and accounted for 57 98 of the total ca released from these rocks experimental effluents from surfically weathered granitoids from the same watersheds were consistently dominated by silicate dissolution the lack of excess ca and alkalinity indicated that calcite had been previously removed by natural weathering the extent of ca enrichment in watershed discharge fluxes corresponds to the amounts of calcite exposed in granitoid rocks high ca na ratios relative to plagioclase stoichiometries indicate excess ca in the yosemite loch vale and other alpine watersheds in the sierra nevada and rocky mountains of the western united states this ca enrichment correlates with strong preferential weathering of calcite relative to plagioclase in exfoliated granitoids in glaciated terrains in contrast ca na flux ratios are comparable to or less than the ca na ratios for plagioclase in the subtropical panola and tropical rio icacos watersheds in which deeply weathered regoliths exhibit concurrent losses of calcite and much larger masses of plagioclase during transport limited weathering these results indicate that the weathering of accessory calcite may strongly influence ca and alkalinity fluxes from silicate rocks during and following periods of glaciation and tectonism but is much less important for older stable geomorphic surfaces

effects of organic ligands on granite dissolution in batch experiments at ph 6 yosemite granite from the tuolumne river series was dissolved under oxic and anoxic conditions in the presence 0 001 or 0 01 m and absence of organic ligands in batch experiments at ph 6 release of all elements was enhanced considerably in the presence of organic ligands citrate tridentate and gallate tetradentate increased element release to the greatest extent among the aliphatic and aromatic ligands respectively the extent of element mobilization observed for the aliphatic ligands decreased in the order citrate oxalate malonate and for the aromatic ligands gallate salicylate phthalate the effects of the ligands generally followed trends in cation ligand stability constants but aromatic ligands were less effective in element mobilization than aliphatic ligands this was attributed to protonation of the functional groups of aromatic ligands at ph 6 rock dissolution was non stoichiometric regardless of the presence or absence of organic ligands release of p and cu of total element content in the unweathered rock in the presence of organic ligands was considerably greater than that of other elements findings of the present study were compared to the findings of our previous study on dissolution of basalt differences in the mobility patterns of y fe cu ti and zr during dissolution of granite and basalt were observed in basalt release of y was enhanced considerably in the presence of citrate in contrast in the present study release of y from granite with and without citrate was at the detection limit this difference was attributed to the difference in y hosting parent minerals apatite basalt and sphene granite with and without organic ligands no significant differences were observed in the extent of fe released from granite under oxic versus anoxic conditions while the extent of fe release from basalt was considerably greater under anoxic versus oxic conditions with and without organic ligands these differences can be attributed to the difference in major fe hosting phases in the rocks biotite granite versus glass and augite basalt in the granite concentrations of cu released increased considerably in the presence of organic ligands under both oxic and anoxic conditions in contrast concentrations of cu released from basalt were increased considerably only under oxic conditions especially in the presence of organic ligands this difference was attributed to the different extent of fe release from basalt and granite that affected dissolution of cu fe sulfides although both ti and zr can be mobilized in the presence of organic ligands in the rock where zircons hosted zr granite this element was the most immobile while in the rock where fe ti oxides hosted zr basalt ti was the most immobile

a semidiscrete finite volume formulation for multiprocess watershed simulation 1 hydrological processes within the terrestrial water cycle operate over a wide range of time and space scales and with governing equations that may be a mixture of ordinary differential equations odes and partial differential equations pdes in this paper we propose a unified strategy for the formulation and solution of fully coupled process equations at the watershed and river basin scale the strategy shows how a system of mixed equations can be locally reduced to ordinary differential equations using the semidiscrete finite volume method fvm domain decomposition partitions the watershed surface onto an unstructured grid and vertical projection of each element forms a finite volume on which all physical process equations are formed the projected volume or prism is partitioned into surface and subsurface layers leading to a fully coupled local ode system referred to as the model kernel the global ode system is assembled by combining the local ode system over the domain and is then solved by a state of the art ode solver the unstructured grid based on delaunay triangulation is generated with constraints related to the river network watershed boundary elevation contours vegetation geology etc the underlying geometry and parameter fields are then projected onto the irregular network the kernel based formulation simplifies the process of adding or eliminating states constitutive laws or closure relations the strategy is demonstrated for the shale hills experimental watershed in central pennsylvania and several phenomena are observed 1 the enslaving principle is shown to be a useful approximation for soil moisture water table dynamics for shallow soils in upland watersheds 2 the coupling shows how antecedent moisture i e initial conditions can amplify peak flows 3 the coupled equations predict the onset or threshold for upland ephemeral channel flow and 4 the model shows how microtopographic information controls surface saturation and connectivity of overland flow paths for the shale hills site the open source code developed in this research is referred to as the penn state integrated hydrologic model pihm

ree mobility and fractionation during shale weathering along a climate gradient abstract we systematically investigated six soil profiles developed on a climosequence of gray shale to constrain the mobility and fractionation of rare earth elements ree during chemical weathering processes in addition one site developed on black shale marcellus formation was included to document ree behaviors in organic rich versus organic poor shale end members under the same environmental conditions our study shows that ree are mobilized intensively during shale weathering and the extent of depletion is larger under warm humid climates however the integrated release rates calculated from six soil profiles are not directly correlated to mean annual precipitation or temperature instead the primary control might be the ree concentrations in the most reactive minerals ree bearing phases in shale sulfides phosphates and organic matter probably react quickly at first mobilizing ree following that ree are then released more slowly during dissolution reactions of clay minerals consistent with this interpretation black shale weathers much faster and releases more ree than gray shale under the same climate conditions due to the higher organic matter and sulfide contents and lower soil ph ree are not 100 depleted in any of the investigated soil sites in northern sites depletion is minimal whereas in the southern warm and humid sites surface depletion is higher and re deposition is observed at depth retention of ree is likely caused by adsorption to mineral surfaces as ph increases and dissolved organic matter content decreases with depth this case study quantified loss redistribution and fractionation of ree during shale weathering improved our understanding of ree mobility in surficial environments and contributed to the exploration of ree as strategic mineral resources

topographic controls on the depth distribution of soil co2 in a small temperate watershed accurate measurements of soil co2 concentrations pco2 are important for understanding carbonic acid reaction pathways for continental weathering and the global carbon c cycle while there have been many studies of soil pco2 most sample or model only one or at most a few landscape positions and therefore do not account for complex topography here we test the hypothesis that soil pco2 distribution can predictably vary with topographic position we measured soil pco2 at the susquehanna shale hills critical zone observatory sshczo pennsylvania where controls on soil pco2 e g depth texture porosity and moisture vary from ridge tops down to the valley floor between planar slopes and slopes with convergent flow i e swales and between north and south facing aspects we quantified pco2 generally at 0 1 0 2 m depth intervals down to bedrock from 2008 to 2010 and in 2013 of the variables tested topographic position along catenas was the best predictor of soil pco2 because it controls soil depth texture porosity and moisture which govern soil co2 diffusive fluxes the highest pco2 values were observed in the valley floor and swales where soils are deep 0 7 m and wet resulting in low co2 diffusion through soil profiles in contrast the ridge top and planar slope soils have lower pco2 because they are shallower 0 6 m and drier resulting in high co2 diffusion through soil profiles aspect was a minor predictor of soil pco2 the north i e south facing swale generally had lower soil moisture content and pco2 than its south i e north facing counterpart seasonally we observed that while the timing of peak soil pco2 was similar across the watershed the amplitude of the pco2 peak was higher in the deep soils due to more variable moisture content the high pco2 observed in the deeper wetter topographic positions could lower soil porewater ph by up to 1 ph unit compared to porewaters equilibrated with atmospheric co2 alone co2 is generally the dominant acid driving weathering in soils based on our observations models of chemical weathering and co2 dynamics would be improved by including landscape controls on soil pco2

frontogenesis and frontal arrest of a dense filament in the oceanic surface boundary layer the evolution of upper ocean currents involves a set of complex poorly understood interactions between submesoscale turbulence e g density fronts and filaments and coherent vortices and smaller scale boundary layer turbulence here we simulate the lifecycle of a cold dense filament undergoing frontogenesis in the presence of turbulence generated by surface stress and or buoyancy loss this phenomenon is examined in large eddy simulations with resolved turbulent motions in large horizontal domains using sim 10 10 grid points steady winds are oriented in directions perpendicular or parallel to the filament axis due to turbulent vertical momentum mixing cold filaments generate a potent two celled secondary circulation in the cross filament plane that is frontogenetic sharpens the cross filament buoyancy and horizontal velocity gradients and blocks ekman buoyancy flux across the cold filament core towards the warm filament edge within less than a day the frontogenesis is arrested at a small width approx 100 text m primarily by an enhancement of the turbulence through a small submesoscale horizontal shear instability of the sharpened filament followed by a subsequent slow decay of the filament by further turbulent mixing the boundary layer turbulence is inhomogeneous and non stationary in relation to the evolving submesoscale currents and density stratification the occurrence of frontogenesis and arrest are qualitatively similar with varying stress direction or with convective cooling but the detailed evolution and flow structure differ among the cases thus submesoscale filament frontogenesis caused by boundary layer turbulence frontal arrest by frontal instability and frontal decay by forward energy cascade and turbulent mixing are generic processes in the upper ocean

a mathematical model for steady state regolith production at constant erosion rate it has been hypothesized that many soil profiles reach a steady state thickness in this work such profiles were simulated using a one dimensional model of reaction with advective and diffusive solute transport a model rock is considered consisting of albite that weathers to kaolinite in the presence of chemically inert quartz the model yields three different steady state regimes of weathering at the lowest erosion rates a local equilibrium regime is established where albite is completely depleted in the weathering zone this regime is equivalent to the transport limited regime described in the literature with an increase in erosion rate transition and kinetic regimes are established in the transition regime both albite and kaolinite are present in the weathering zone but albite does not persist to the soil air interface in the weathering limited regime here called the kinetic regime albite persists to the soil air interface the steady state thickness of regolith decreases with increasing erosion rate in the local equilibrium and transition regimes but in the kinetic regime this thickness is independent of erosion rate analytical expressions derived from the model are used to show that regolith production rates decrease exponentially with regolith thickness the steady state regolith thickness increases with the darcy velocity of the pore fluid and in the local equilibrium regime may vary markedly with small variations in this velocity and erosion rate in the weathering limited regime the temperature dependences for chemical weathering rates are related to the activation energy for the rate constant for mineral reaction and to the h of dissolution while for local equilibrium regimes they are related to the h only the model illustrates how geochemical and geomorphological observations are related for a simple compositional system the insights provided will be useful in interpreting natural regolith profiles copyright 2010 john wiley sons ltd

lunar impact basins and crustal heterogeneity new western limb and far side data from galileo multispectral images of the lunar western limb and far side obtained from galileo reveal the compositional nature of several prominent lunar features and provide new information on lunar evolution the data reveal that the ejecta from the orientale impact basin 900 kilometers in diameter lying outside the cordillera mountains was excavated from the crust not the mantle and covers pre orientale terrain that consisted of both highland materials and relatively large expanses of ancient mare basalts the inside of the far side south pole aitken basin 2000 kilometers in diameter has low albedo red color and a relatively high abundance of iron and magnesium rich materials these features suggest that the impact may have penetrated into the deep crust or lunar mantle or that the basin contains ancient mare basalts that were later covered by highlands ejecta

from a black to a gray box a mass balance interpretation of pedogenesis we utilize chemical elements as tracers in a mass balance analysis that provides functional relationships among soil chemical composition bulk density and volume change in relation to parent material these analytical functions are based on the principle of conservation of mass and include a term quantifying mass flux into out of the soil and between horizons we apply the technique to the oldest member of a chronosequence developed on marine terraces in northern california it is an alfisol that evolved from beach sand to its present state nearly one third of its weight is composed of secondary clay minerals in about 240 ky aside from large increases in organic carbon desilication is the dominant factor in soil evolution 29 50 83 g cm 2 si was leached from the beach sand during pedogenesis the rate of desilication is roughly 2 1 t km 2 yr 1 0 21 g cm 2 ky 1 an order of magnitude slower than that implied by the si denudation rate calculated for the mattole river watershed weathering of primary minerals and synthesis of secondary minerals is relatively well advanced suggesting that the rate of desilication may be declining the local beach is composed of quartz and sodic plagioclase with smaller amounts of chlorite mica and kaolinite the soil has substantially different mineralogy sand is dominated by quartz and clay is dominated by kaolinite halloysite chloritic intergrades and gibbsite bases are also leached though the total mass was much less 57 2 55 g cm 2 of na in the beach sand was lost as plagioclase weathered by focusing on elemental and mineralogical gains and losses we emphasize the essential connection between the pedologic environment and the external hydrochemical environment

behavior of re and os during low temperature alteration results from himalayan soils and altered black shales re os analyses were performed on five soil profiles developed on silicate lithologies in the narayani drainage basin of the himalayas as well as on several altered black shales and associated alteration phases the results indicate that all of these samples have lost large amounts of re this re loss approached 100 in the black shale derived soils which also most probably lost substantial quantities of os the near constancy of os and re concentrations with depth indicates that this loss occurred quite early in the alteration process rather than progressively during the course of soil development a slight decrease in 187os 188os was observed toward the surface of the two black shale soil profiles possibly indicating a minor preferential mobility of radiogenic 187os for this lithology in the black shale derived saprolite and soils the loss of re and os was related to the loss of organic carbon the importance of this phase is underscored by the fact that organic material separated from a black shale sample accounted for nearly all of the os contained in the whole rock analysis of alteration phases from the surface of a weathered black shale showed that os liberated during alteration was partially reprecipitated in fe oxides with os isotopic compositions very similar to that of the original rock whereas re was removed with the fluid phase these results demonstrate the disproportionately large role that black shale weathering may play in determining the re and os contents of continental runoff and thus ultimately of seawater but they also emphasize the possible complexity of this process the data suggest that a large fraction of the os contained in black shales is released during chemical alteration which is apparently not the case for most other silicate rocks therefore the potential contribution of black shales to the dissolved os budget of runoff and river water may be even greater than that expected from the high os concentrations of these rocks the extent to which this os will affect the seawater os composition depends on how efficiently it is recaptured by secondary phases such as fe mn oxides in situ or during transport these results also underscore the high mobility of re with respect to os at every stage in the erosional process thus explaining the order of magnitude increase in re os ratio from the black shale source rocks to seawater

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

magnesium isotope fractionation during shale weathering in the shale hills critical zone observatory accumulation of light mg isotopes in soils by clay mineral transformation abstract magnesium isotopic ratios have been used as a natural tracer to study weathering processes and biogeochemical pathways in surficial environments but few have focused on the mechanisms that control mg isotope fractionation during shale weathering in this study we focus on understanding mg isotope fractionation in the shale hills catchment in central pennsylvania mg isotope ratios were measured systematically in weathering products along geochemical pathways of mg during shale weathering from bedrock to soils and soil pore water on a planar hillslope and to sediments stream water and groundwater on a valley floor significant variations of mg isotopic values were observed 26mg values 0 6 to 0 1 of stream and soil pore waters are about 0 5 to 1 lighter than the shale bedrock 26mg values of 0 4 consistent with previous observations that lighter mg isotopes are preferentially released to water during silicate weathering dissolution of the carbonate mineral ankerite depleted in the shallow soils but present in bedrock at greater depths produced higher mg2 concentrations but lower 26mg values 1 1 in groundwater 1 5 lighter than the bedrock 26mg values 0 2 to 0 4 of soil samples on the planar hillslope are either similar or up to 0 2 lighter than the bedrock hence a heavy mg isotope reservoir complementary to the lighter mg isotopes in soil pore water and stream water is missing from the residual soils on the hillslope in addition soil samples show a slight but systematic decreasing trend in 26mg values with increasing weathering duration towards the surface we suggest that the accumulation of light mg isotopes in surface soils at shale hills is due to a combined effect of i sequestration of isotopically light mg from soil water during clay dissolution precipitation reactions and ii loss of isotopically heavy particulate mg in micron sized particles from the hillslope as suspended sediments this latter mechanism is somewhat surprising in that most researchers do not consider physical removal or particles to be a likely mechanism of isotopic fractionation stream sediments 26mg values of 0 3 to 0 5 accumulated on the valley floor are 0 2 heavier than the bedrock and are thus consistent with that mobile particulates are the heavy mg isotope reservoir our study provides the first field evidence that changes in clay mineralogy lead to accumulation of lighter mg isotopes in residual bulk soils this example also demonstrates that transport of isotopically distinct fine particles from clay rich systems could be a new and important mechanism to drive the mg isotope compositions of silicate weathering residuals this mechanism drives fractionation in an opposite direction as might be expected from previous studies i e residual soils are driven to lighter mg values and sediments become isotopically heavier

modelling chemical depletion profiles in regolith abstract chemical or mineralogical profiles in regolith display reaction fronts that document depletion of leachable elements or minerals a generalized equation employing lumped parameters was derived to model such ubiquitously observed patterns c c 0 c 0 c x 0 c x 0 exp ini k x 1 here c cx 0 and co are the concentrations of an element at a given depth x at the top of the reaction front or in parent respectively ini is the roughness of the dissolving mineral in the parent and k is a lumped kinetic parameter this kinetic parameter is an inverse function of the porefluid advective velocity and a direct function of the dissolution rate constant times mineral surface area per unit volume regolith this model equation fits profiles of concentration versus depth for albite in seven weathering systems and is consistent with the interpretation that the surface area m2 mineral m 3 bulk regolith varies linearly with the concentration of the dissolving mineral across the front dissolution rate constants can be calculated from the lumped fit parameters for these profiles using observed values of weathering advance rate the proton driving force the geometric surface area per unit volume regolith and parent concentration of albite these calculated values of the dissolution rate constant compare favorably to literature values the model equation useful for reaction fronts in both steady state erosional and quasi stationary non erosional systems incorporates the variation of reaction affinity using ph as a master variable use of this model equation to fit depletion fronts for soils highlights the importance of buffering of ph in the soil system furthermore the equation should allow better understanding of the effects of important environmental variables on weathering rates

cu isotopes and concentrations during weathering of black shale of the marcellus formation huntingdon county pennsylvania usa abstract the complex weathering processes which govern the production of soil from bedrock have proven difficult to understand for many lithologies weathering of black shale is of particular interest because it releases organic carbon and heavy metals as solutes and therefore impacts the health of terrestrial and aquatic ecosystems to understand black shale weathering a geochemical survey was initiated for soils developed on shales of the marcellus formation at a zero order catchment at a satellite site of the susquehanna shale hills critical zone observatory located in jackson corner pennsylvania this formation is an organic and metal rich carbonaceous shale that underlies much of new york pennsylvania ohio and west virginia in this paper we focus on the effects of weathering on variations of cu isotopes in the shale cu concentration data for soil were normalized using ti concentrations to document the mobility of cu relative to bedrock at both the ridgetop and valley floor depletion profiles for cu are documented in the soils the cu in the soils is depleted in 65 cu average 65 cu 0 5 0 2 compared to the parent material average 65 cu 0 03 0 15 consistent with loss of cu from soils the pore waters contain 10 ppb cu on average and are enriched in the heavy isotope average value 65 cu 1 14 0 44 rayleigh fractionation models using the concentration and isotope data of the soils are consistent with pyrite weathering and loss of cu from the ridgetop but downslope transport and cu re precipitation at the valley floor

worldwide distribution of continental rock lithology implications for the atmospheric soil co2 uptake by continental weathering and alkalinity river transport to the oceans 1 the silicate rock weathering followed by the formation of carbonate rocks in the ocean transfers co2 from the atmosphere to the lithosphere this co2 uptake plays a major role in the regulation of atmospheric co2 concentrations at the geologic timescale and is mainly controlled by the chemical properties of rocks this leads us to develop the first world lithological map with a grid resolution of 1 1 this paper analyzes the spatial distribution of the six main rock types by latitude continents and ocean drainage basins and for 49 large river basins coupling our digital map with the gem co2 model we have also calculated the amount of atmospheric soil co2 consumed by rock weathering and alkalinity river transport to the ocean among all silicate rocks shales and basalts appear to have a significant influence on the amount of co2 uptake by chemical weathering

geochemical behaviors of different element groups during shale weathering at the susquehanna shale hills critical zone observatory major and trace element concentrations were measured in bedrock regolith and stream sediments from a first order catchment developed entirely on grey shale in central pennsylvania usa these elements can be classified into five major groups based on statistical data analysis the presence of different elemental groups is due to the mineralogical origin cycling processes and geochemical properties of these elements during soil formation a better understanding of the behaviors of these elements during chemical weathering would allow for their possible use as natural tracers in critical zone processes

variations in weathering processes and rates with time in a chronosequence of soils from glen feshie scotland chemical and mineralogical characteristics have been determined for a chronosequence of six soil profiles ranging in age from 80 13 000 years bp developed on river terraces in the western cairngorms of scotland the c horizons are similar chemically and mineralogically and the soils have similar pedogenetic histories exchangeable ca and mg decrease with time and base saturation decreases exponentially from 24 6 in the ah horizon of the youngest profile to 2 8 in the comparable horizon of the 10 000 year old profile according to the chronofunction y 3 372 22 612 exp 0 0007365t long term weathering rates of base cations calculated from the loss of these cations relative to zr appear to decrease exponentially with time but this may be due to the method of calculation the magnitude of loss of base cations decreases in the sequence na k mg ca but when the relative mobilities of these elements are considered the loss is in the order mg na ca k this reflects the dissolution of chlorite and loss of mg and the more rapid weathering of plagioclase feldspar and loss of na and ca particularly in the coarse sand fraction than k feldspar the clay fractions although 2 of all horizons also show distinct patterns with age in that chlorite and mica are less abundant in older soils and vermiculite is more abundant the latter phase often having hydroxyaluminium polymers in the interlayer region the chemical and mineralogical trends in the soil sequence are closely associated and are induced by pedogenic weathering

extent and isotopic composition of fe and mo release from two pennsylvania shales in the presence of organic ligands and bacteria abstract isotopic fractionation of fe and mo during weathering could contribute toward the isotopic signatures of river and ocean waters to investigate weathering processes batch experiments were carried out at ph 6 under oxygenated conditions to investigate the influence of a nitrogen fixing soil bacterium and organic ligands on the extent and isotopic signature of fe and mo release from two pennsylvania shales with different mineralogies an olive to grey shale rose hill and a black shale marcellus results of these studies showed that fe and mo were mainly released from illite chlorite vermiculite and fe oxides in the rhs and from pyrite in the ms dissolution rates of the clays estimated from our batch experiments are broadly consistent with published estimates release of fe from both shales was only enhanced by the hydroxamate siderophore desferrioxamine b dfam in contrast none of the treatments enhanced release of mo furthermore release of this metal was measurable only for the black shale for both shales fe that was released in the presence of dfam was depleted in 56 fe as compared to the bulk rock in contrast leachate solutions were enriched in the heavier mo isotope as compared to the bulk marcellus in all experiments with and without organic ligands and the bacterium the isotopic fractionations in fe and mo are broadly consistent with previously reported fractionation effects during sorption onto precipitating fe mn oxides the observed mo isotope fractionation is also consistent with all published studies of rivers i e riverine mo is enriched in heavy mo isotopes the observed fe isotope fractionation is likewise consistent with published studies for some rivers i e riverine fe is sometimes depleted in 56 fe our experimental results are consistent with sorption of fe and mo onto fe oxyhydr oxides during weathering as a possible explanation for the isotopic signatures of these metals in many rivers

quantification of chemical weathering rates across an actively eroding hillslope abstract chemical weathering rates for landscapes are difficult to quantify because the timescales over which weathering occurs are often unknown in this study we use timescales defined by prior cosmogenic nuclide analyses and a suite of geochemical measurements to calculate weathering rates in saprolite and soil and to determine how these rates vary across an eroding hillslope we also estimate the relative contributions of solute and erosional mass loss to landscape lowering analyses were conducted on a soil mantled hillslope developed on a granodiorite pluton in southern nsw australia mass loss in solution accounts for 35 to 55 of the total mass loss from the hillslope saprolite close to the soil saprolite boundary is less weathered at the ridge than at distance from the ridge the calculated flux of silica from the saprolite is 5 tons km 2 yr 1 and does not vary with distance from the ridge or overlying soil thickness the assumption of steady state but spatially variable erosion rates with a temporally constant thickness of soil and saprolite allows us to calculate the downslope variation in the rate of solute losses soil silica weathering rates initially increase from 12 tons km 2 yr 1 at the ridge crest to 20 tons km 2 yr 1 on the convex region of the hillslope and then decrease to 13 tons km 2 yr 1 by the time soils have been transported 45 50 m soils closer to the surface are more weathered than deeper soils this geochemical stratification suggests that the soil column does not become thoroughly vertically mixed as soils move down slope dependence of solute loss on transport distance may explain the previously noted discrepancy between the observed soil thickness and that predicted based on curvature variation of solute loss with transport distance may also contribute to the linear dependence of soil thickness on distance from the ridge

genesis of soils and landscapes in the ridge and valley province of central pennsylvania abstract the characteristics and properties of the soils on the ridge tops footslopes and adjacent limestone valley areas in the ridge and valley of central pennsylvania have been strongly influenced by their parent material and geomorphic history the ridge top soils have developed in sandstone colluvium which mantles sandstone residuum the upper part of the original residual ridge top soil was truncated during late wisconsinan time and then covered with local colluvium or it was cyroturbated these sandstone parent materials have been stable since the late wisconsinan and have sandy skeletal dystrochrepts and haplorthods developed in them the haplorthods are minor soils and are associated with local concentrations of coniferous vegetation during the late wisconsinan the sandstone colluvium also moved downslope and was mixed with bedrock and residual material from shale and limestone and deposited on the footslope over a pre wisconsinan soil developed in older colluvium or limestone residuum the footslope surface colluvial soils vary in texture and drainage because of their parent material their location in discharge areas and fragipan development the age of the brown surface colluvium is considered late wisconsinan and the age of the pre wisconsinan buried soils is not known the buried soil s bright red rubified color and argillic horizon indicate a much greater degree of soil development than noted in the brown surface colluvium and its age may be correlated with isotope stage 6 the soils developed at the surface in the colluvium are mainly ultisols although some poorly drained soils particularly in limestone material are alfisols the ultisols are parent material ultisols and the poorly drained alfisols have a high base status in their parent material or were recharged with bases from the groundwater the soils of the limestone valleys are developed in residuum the residuum accumulated from the insoluble residues after the caco 3 was leached from the bedrock if the residuum is thick 2 to 3 m the soils date back many hundreds of thousands of years but are still classified as hapludalfs in addition to being old the surface of the hapludalfs has been modified by periglacial truncation and the addition of eolian materials these processes have given the upper 50 cm of the hapludalfs a late wisconsinan age but the bulk of the b horizon is many thousands of years older eolian material has also been added to the ridge top soils as well as the colluvial soils the mineralogy of all the soils in this landscape including the buried paleosols does not show significant clay mineral weathering this appears anomalous considering the degree of oxidation of the buried paleosols and the limestone soils and their estimated age

learning to read the chemistry of regolith to understand the critical zone the base of the critical zone includes the mantle of altered soil and rock regolith that changes in response to chemical physical and biological processes occurring at earth s surface these processes are recorded in the chemistry of the regolith and this long term record can often be deciphered for example on eroding ridgetops where flows are generally downward for water and upward for earth material element concentrations vary with depth to constitute depletion addition depletion enrichment and biogenic profiles models can be used to explore the records of mineral dissolution atmospheric input coupled dissolution precipitation and biolifting documented in these profiles these models enable interpretation of the effects of time climate rates of erosion and human and other biotic impacts on the profile patterns by testing quantitative models against the long term record of information in regolith we will learn to project changes arising from human and natural perturbations of the critic

weathering of phosphorus in black shales 1 rock weathering is the ultimate source of phosphorus p to the oceans where p can be a limiting nutrient for biological production in this paper p weathering is examined in soil chronosequences formed in weathering profiles on the organic rich woodford shale new albany shale and green river shale at all sites organic p and inorganic p concentrations reveal that p weathering is far from complete prior to erosion carbon c p ratios decrease significantly from unweathered shale to the weathered shale at all sites which is driven by loss of total organic c with weathering here we characterize organic phosphorus across a weathering profile from the woodford shale using solid state cpmas 31p nmr spectroscopy techniques revealing that p esters are the dominant forms of p during all stages of weathering certain p esters appear to be resistant to chemical weathering during the millions of years between deposition uplift and erosion possibly representing a significant long term global sink for p

climatic and tectonic controls on chemical weathering in the new zealand southern alps abstract climatic and tectonic controls on the relative abundance of solutes in streams draining the new zealand southern alps were investigated by analyzing the elemental and sr isotope geochemistry of stream waters bedload sediment and hydrothermal calcite veins the average relative molar abundance of major cations and si in all stream waters follows the order ca2 50 si 22 na 17 mg2 6 k 5 for major anions the relative molar abundance is hco3 89 so42 7 cl 4 weathering reactions involving plagioclase and volumetrically small amounts of hydrothermal calcite define the ionic chemistry of stream waters but nearly all streams have a carbonate dominated ca2 and hco3 mass balance stream water ca sr and 87sr 86sr ratios vary from 0 173 to 0 439 mol nmol and from 0 7078 to 0 7114 respectively consistent with the ionic budget these ratios lie solely within the range of values measured for bedload carbonate ca sr 0 178 to 0 886 mol nmol 87sr 86sr 0 7081 to 0 7118 and hydrothermal calcite veins ca sr 0 491 to 3 33 mol nmol 87sr 86sr 0 7076 to 0 7097 streams draining regions in the southern alps with high rates of physical erosion induced by rapid tectonic uplift and an extremely wet climate contain 10 more ca2 and 30 more sr2 from carbonate weathering compared to streams draining regions in drier more stable landscapes similarly streams draining glaciated watersheds contain 25 more sr2 from carbonate weathering compared to streams draining non glaciated watersheds the highest abundance of carbonate derived solutes in the most physically active regions of the southern alps is attributed to the tectonic exhumation and mechanical denudation of metamorphic bedrock which contains trace amounts of calcite estimated to weather 350 times faster than plagioclase in this environment in contrast regions in the southern alps experiencing lower rates of uplift and erosion have a greater abundance of silicate versus carbonate derived cations these findings highlight a strong coupling between physical controls on landscape development and sources of solutes to stream waters using the southern alps as a model for assessing the role of active tectonics in geochemical cycles this study suggests that rapid mountain uplift results in an enhanced influence of carbonate weathering on the dissolved ion composition delivered to seawater