chemical weathering indices applied to weathering profiles developed on heterogeneous felsic metamorphic parent rocks abstract chemical weathering indices are commonly used for characterizing weathering profiles by incorporating bulk major element oxide chemistry into a single metric for each sample generally on homogeneous parent rocks weathering indices change systematically with depth however the weathering of heterogeneous metamorphic rocks confounds the relationship between weathering index and depth in this paper we evaluate previously defined chemical weathering indices for their suitability in characterizing weathering profiles developed on felsic heterogeneous metasedimentary bedrock from coweeta hydrologic laboratory north carolina usa among the weathering indices evaluated here the weathering index of parker wip is the most appropriate for application to weathering profiles on heterogeneous and homogeneous parent rock because the wip includes only the highly mobile alkali and alkaline earth elements in its formulation it yields values that differ greatly from those of the parent rock in addition the wip allows for aluminum mobility unlike other weathering indices these characteristics combine to make the weathering index of parker the most applicable index for studying the weathering of heterogeneous metasedimentary rocks however the wip should be applied judiciously as alkali and alkaline earth metals may be readily depleted during weathering in addition to reflecting weathering the chemical index of alteration cia chemical index of weathering ciw plagioclase index of alteration pia and vogt s residual index v may be sensitive to subtle geochemical changes such as hydrothermal alteration along a fault and or alteration at the water table weathering indices that include iron in their calculations were not included in this study because they do not distinguish between ferric and ferrous iron the oxidation state and distribution of iron in a weathering profile is influenced by the proportion of oxidation states in the pre weathered metamorphic rock and interaction with groundwater during weathering

processes influencing tidal mixing in the region of sills 1 a non hydrostatic model in cross sectional form with idealized topography representing a sill and forced by a barotropic tidal flow is used to examine the role of a hydraulic transition and internal lee waves in determining mixing in the sill region calculations using smooth topography show that unsteady lee waves are generated on the sill slope during flood tide these waves propagate toward the sill when the tide reverses leading to enhanced mixing in the sill region the addition of small scale topography on the leeside of the sill changes the lee wave distribution with an associated increase in mixing depending upon wavelength and amplitude of topography calculations show the importance of the hydraulic transition lee waves and small scale topography in determining mixing in sill regions compared to smooth large scale topography

the neoproterozoic ottfjallet dike swarm of the middle allochthon traced geochemically into the scandian hinterland western gneiss region norway the ottfjallet swarm of late neoproterozoic mafic dikes cutting neoproterozoic sandstones became a key 30 years ago to the tectonics of the scandian caledonides the sandstones were deposited in basins related to opening of lapetus and intruded by dikes in distal parts of the baltoscandian margin close to the developing spreading axis the sandstones and underlying basement rocks were transported from west of the present norwegian coast to as far east as western sweden during the silurian devonian scandian orogeny the sandstones with dikes make up the sarv nappe up to 2 km thick in sweden and the quartzites and amphibolites of the saetra and equivalent nappes in norway these form the upper part of the middle allochthon the lower part of the middle allochthon includes middle proterozoic basement gneisses and rapakivi granites containing mafic rocks in some places the dike bearing quartzite is a key unit due to contrast with similar rocks lacking dikes at lower tectonic levels derived from inboard parts of baltica the saetra nappe and equivalents are well constrained on lithotectonic grounds in norway at oppdal leksdal and orkanger it was also suspected to occur in deep narrow synclines in the western gneiss region where interlayered feldspathic quartzite and amphibolite are in correct tectonostratigraphic sequence locally with a total thickness of only 1 to 3 m and locally with dikes converted to eclogite to test correlations 127 samples of mafic rocks were collected from 14 areas west and southwest of trondheimsfjord into the western gneiss region toward alesund samples include mafic rocks in quartzites and others some clearly dikes from the underlying 1190 ma rapakivi granite augen gneiss of the risberget nappe and adjacent basement gneisses typical saetra dikes in the oppdal quarries and mafic rocks from other quartzites and related rocks have la n sm n ratios of 1 0 to 1 8 and nb la ratios of 0 8 to 1 4 oppdal group most ree patterns are moderately lree enriched with no or very small mostly negative eu anomalies all have similar multi element patterns typically with small positive p anomalies negative zr hf anomalies and an absence of nb ta anomalies showing that the dikes are unrelated to arcs and have no notable continental crust component a subset of saetra risberget and basement dikes is distinguished by higher la n sm n ratios of 1 8 to 2 5 but otherwise has very similar characteristics ystland group these data support correlation of the saetra nappe quartzite and dikes into highly deformed parts of the western gneiss region and correlation of nearby dike rich parts of basement gneiss with the middle allochthon one sample in quartzite at ura at an unusual tectonostratigraphic position has la n sm n 0 7 nb la 0 6 and a multi element pattern different from saetra dikes suggesting it is unrelated to the ottfjallet dikes non saetra like amphibolites also occur in the risberget nappe and have la n sm n ratios of 1 4 to 3 all nb la ratios 0 6 and multi element patterns with sharp negative anomalies for nb ta p zr hf and ti these are probably mesoproterozoic magmas and cumulates emplaced into the rapakivi granite protolith of the augen gneiss

constraints on the preservation of diamict facies melt out tills at the margins of stagnant glaciers abstract this paper reviews the formation and preservation of diamict facies melt out till generated in situ by the downwasting of stagnant ice at the margins of continental glaciers melt out tills are commonly envisaged as being the product of the top supraglacial or bottom subglacial melt of stagnant debris rich glacier ice but such deposits are relatively uncommon in modern glacier environments where they are thin laterally discontinuous and have a low preservation potential theoretical considerations of the distribution of englacial debris in continental ice sheets show that only the glacier margin is likely to contain the necessary volumes of englacial debris for melt out to be a significant diamict forming process however the application of thaw consolidation theory to the formation of such deposits shows that substantial porewater pressures and self sediment deformations can be induced during melt out especially in matrix rich debris the classic melt out mechanism widely invoked in the literature since 1875 and involving passive in situ aggregation from thawing englacial debris can be seen to operate under restricted conditions diamict facies produced by melt out are likely to form spatially disjunct and laterally discontinuous elements within complex and ice marginal stratigraphics the melt out process is not a mechanism whereby regionally extensive diamiet ite units can be deposited across glaciated basins

rates of weathering rind formation on costa rican basalt weathering rind thicknesses were measured on 200 basaltic clasts collected from three regionally extensive alluvial fill terraces qt 1 qt 2 and qt 3 preserved along the pacific coast of costa rica mass balance calculations suggest that conversion of unweathered basaltic core minerals plagioclase and augite to authigenic minerals in the porous rind kaolinite allophane gibbsite fe oxyhydroxides is iso volumetric and ti and zr are relatively immobile the hierarchy of cation mobility ca na k mg si al fe p is similar to other tropical weathering profiles and is indicative of differential rates of mineral weathering anorthite albite hypersthene orthoclase apatite alteration profiles across the cm thick rinds document dissolution of plagioclase and augite and the growth of kaolinite with subsequent dissolution of kaolinite and precipitation of gibbsite as weathering rinds age the rate of weathering rind advance is evaluated using a diffusion limited model which predicts a parabolic rate law for weathering rind thickness rr as a function of time t rr t and an interface limited model which predicts a linear rate law for weathering rind thickness as a function of time rr kappt in these rate laws is a diffusion parameter and kapp is an apparent rate constant the rate of advance is best fit by the interface model terrace exposures are confined to the lower reaches of streams draining the pacific slope near the coast where the stream gradient is less than 3 m km and terrace deposition is influenced by eustatic sea level fluctuations geomorphological evidence is consistent with terrace deposition coincident with sea level maxima when the stream gradient would be lowest assigning the most weathered regionally extensive terrace qt 1 mean rind thickness 6 9 0 6cm to oxygen isotope stage ois 7 ca 240 ka and assuming that at time 0 rind thickness 0 it is inferred that terrace qt 2 rr 2 9 0 1 cm is coincident with stage 5e ca 125 ka and that qt 3 rr 0 9 0 1 cm is consistent with ois 3 ca 37 ka these assignments yield a value of kapp of 8 6 10 13 cm s 1 r 2 0 99 only this value satisfies both the existing age controls and yields ages coincident with sea level maxima using this value elemental weathering release fluxes across a weathering rind from qt 2 range from 6 0 10 9 mol si m 2 s 1 to 2 5 10 11 mol km 2 s 1 the rate of rind advance for the costa rican terraces is 2 8 10 7 my r 1 basalt rind formation rates in lower temperature settings described in the literature are also consistent with interface controlled weathering with an apparent activation energy of about 50 kj mol 1 rates of rind formation in costa rica are an order of magnitude slower than reported for global averages of soil formation rates copyright 2004 elsevier ltd

the origin of deep buried channels of elsterian age in northwest germany buried channels cut to a depth of over 100m into the underlying substratum of north germany are almost exclusively of elsterian age evaluation of geophysical well logs in the hamburg area for the first time allows the construction of detailed longitudinal and transverse profiles it can be shown that an apparently chaotic infill known from borehole records in some cases is actually a regular sedimentary sequence fining from proximal to distal channel formation seems to have been the result of catastrophic meltwater release in the marginal parts of the ice sheet the channel infill reflects these episodic outbursts of meltwater during deglaciation the channel remnants became infilled with fine sediments the channels ceased to exist as morphologically detectable forms at the end of the holsteinian stage

a simple model of fjord and coastal circulation interaction abstract the dynamical interaction of a narrow fjord with a wind driven coastal regime is investigated using a linear two layer numerical model the coriolis acceleration is important in the coastal regime but assumed to he unimportant in the fjord dynamical because v 0 for a wide variety of wind conditions bottom topography and model parameters the wind forced coastal circulation with its geostrophic alongshore currants has a strong effect on the circulation within the fjord these geostrophic currents control the free surface and pycnocline displacement at the fjord mouth thereby strongly affecting fjord circulation this mechanism is an alternative to the classical idea of hydraulic control at the mouth by sills or constrictions model simulators also show that the free surface slope is a baroclinic effect and that alongshore and across shore winds affect the fjord differently alongshore winds produce flooding while up and down fjord winds simply sat up the surface we find that offshore win

importance of environment on the order of mineral weathering in olivine basalts hawaii examination of weathering rinds from lava flows on hawaii with backscatter electron microscopy and electron micro probe analysis reveals that olivine weathers more slowly than adjacent clinopyroxene and plagioclase in environments with a paucity of organic acids yet when weathering rinds are in contact with abundant organic acids secreted by lichens olivine weathers before clinopyroxene and plagioclase weathers last the exception to goldich s widely accepted mineral stability series in organic poor environments runs counter to a thermodynamics explanation for the order of mineral weathering and illustrates the importance of the biogeochemical environment

a mechanism governing the estuarine circulation in deep strongly stratified fjords the estuarine circulation in deep strongly stratified fjords is discussed it is argued that a two layer description of the stratification in the fjord is correct in very wide fjords wide compared to the width of the mouth and possibly also in narrow fjords with high runoff and or weak mixing a theory for the thickness and the salinity of the brackish layer in a wide fjord was earlier developed by the present author and published in swedish 1975 and it is presented here among other findings in that theory we may mention that the thickness of the brackish layer is primarily determined by the internal hydraulic control for high specific runoff runoff unit horizontal surface area of the fjord and weak mixing in the other extreme with low specific runoff and strong mixing the thickness of the brackish layer is found to be proportional to the monin obukhov length the circulation in not very wide fjords is also discussed it is found that recirculation in the brackish layer may be expected whereby a two layer description of the flow field breaks down at least locally a critical rayleigh number that seems to control the recirculation of brackish water within the fjord is found a theory for the density difference between the mouth and the head in the brackish layer in the fjord is developed from the critical rayleigh number condition it is found that this density difference normally is proportional to the density difference between the brackish water at the mouth and the underlying sea water provided that the river runoff is not too heavy and or the mixing is not too weak this prediction is confirmed by extensive measurements from the nordfjord

clay mineralogy of weathering rinds and possible implications concerning the sources of clay minerals in soils weathering rinds on volcanic clasts in quaternary deposits in the western united states contain only very fine grained and poorly crystalline clay minerals rinds were sampled from soils containing well developed argillic b horizons in deposits about 105 yr old or more the clay size fraction of the rinds is dominated by allophane and iron hydroxy oxides whereas the b horizons contain abundant well crystallized clay minerals the contrast between the clay mineralogy of the weathering rinds in which weathering is isolated from other soil processes and that of the associated soil matrices suggests a need to reassess assumptions concerning the rates at which clay minerals form and the sources of clay minerals in argillic b horizons this study suggests that crystalline clay minerals form more slowly in weathering rinds than is generally assumed for soil environments and that the weathering of primary minerals may not be the dominant source of crystalline clay minerals in middle to late pleistocene soils

the effect of curvature on weathering rind formation evidence from uranium series isotopes in basaltic andesite weathering clasts in guadeloupe abstract to quantify rates of rind formation on weathering clasts under tropical and humid climate and to determine factors that control weathering reactions we analyzed uranium series isotope compositions and trace element concentrations in a basaltic andesite weathering clast collected from basse terre island in guadeloupe u th and ti elemental profiles reveal that th and ti behave conservatively during rind formation but that u is added from an external source to the rind in the rind weathering reactions include dissolution of primary minerals such as pyroxene plagioclase and glass matrix as well as formation of fe oxyhydroxides gibbsite and minor kaolinite rare earth element ree profiles reveal a significant eu negative anomaly formed during clast weathering consistent with plagioclase dissolution significant porosity forms in the rind mostly due to plagioclase dissolution the new porosity is inferred to allow influx of soil water carrying externally derived dissolved u due to this influx u precipitates along with newly formed clay minerals and oxyhydroxides in the rind the conservative behavior of th and the continuous addition of u into the rind adequately explain the observed systematic trends of 238 u 232 th and 230 th 232 th activity ratios in the rind rind formation rates determined from the measured u series activity ratios with an open system u addition model increase by a factor of 1 3 0 18 0 24 mm kyr from a low curvature to a high curvature section 0 018 0 12 mm 1 of the core rind boundary revealing that curvature affects rates of rind formation as expected for diffusion limited rind formation u series geochronometry thus provides the first direct evidence that the curvature of the interface controls the rate of regolith formation at the clast scale the weathering rates determined at the clast scale can be reconciled with the weathering rates determined at the watershed or soil profile scale if surface roughness equals values of approximately 1300 2200

reflection of the internal tide in upper loch linnhe a scottish fjord abstract results from an observational study of the internal tide of upper loch linnhe a fjord on the west coast of scotland are presented between november 1992 and june 1993 moorings containing current meters measuring velocity temperature and salinity were deployed at two sites in the loch observations of the horizontal velocities show the presence of an energetic first mode linear internal tide at the m 2 frequency with surface amplitudes of up to 0 57 m s 1 cf 0 03 m s 1 for the barotropic component independent evidence of the m 2 internal tide is provided by vertical velocities inferred from salinity and temperature variations in june 1993 an undulating ctd was used to study the horizontal propagation of the semi diurnal internal tide the results show that over the inner reaches of the loch the internal tide behaves as a standing wave with a large proportion of the internal tide energy being reflected at the landward end of the loch using the phase relationship between the velocity components from the mooring data it is demonstrated that there is a significant standing wave component present throughout the 7 month observational period closer to the sill the undulating ctd observations show the formation of an intense hydraulic jump on the flood tide suggesting the area immediately landward of the sill to be a region of complicated dynamics and high dissipation

generation of abnormal trace element abundances in antarctic eucrites by weathering processes abstract based on rees antarctic eucrites can be divided into two groups those showing normal trace element characteristics e g similar to juvinas and those showing abnormal trace element abundances many antarctic eucrite polymict eucrite and basaltic clast samples show the abnormal trace element abundances with ree patterns exhibiting positive ce anomalies sometimes negative ce anomalies positive eu anomalies and low abundances of the remainder of the rees with the lrees generally being at lower relative abundances than the hrees most samples of crystalline clasts from the polymict eucrites lew85300 lew85302 and lew85303 show the abnormal patterns while the glassy matrixes of these meteorites show normal patterns exterior samples generally show more abnormal patterns larger anomalies greater depletions than interior samples from the same meteorites comparison of all basaltic eucrite literature data combined with our data shows that positive and negative ce anomalies and positive eu anomalies are found in about 61 of antarctic eucrite analyses and are virtually unknown in non antarctic eucrite analyses further positive ce anomalies and positive eu anomalies are commonly associated with antarctic eucrites having low ree concentrations consideration of mineral melt partition coefficients shows that it is unlikely that ce anomalies are magmatic features from the hed parent body cerium anomalies on earth are generally restricted to the weathering zone where the relative ease of oxidizing ce to the 4 state allows for fractionation of ce from the 3 rees we believe the unusual ree patterns of abnormal antarctic eucrites arise from weathering effects generated in or on the antarctic ice our suggested scenario involves formation of melt water and its equilibration with the atmosphere which promotes dissolution of ree rich phosphates and oxidation of ce tetravalent ce can then be fractionated from the trivalent ree in solution the details of the weathering process are unclear and will require detailed chemical and sem investigations of eucrites for their elucidation we predict that rapidly chilled eucrites with glassy rather than crystalline mesostases will be more likely to survive the antarctic environment without alteration of their ree patterns occasional s se and k enrichments are likely due to weathering in the antarctic environment as well but these enrichments are not well correlated with ce anomalies

the comparison of a numerical model to observations of velocity and scalar data in burrard inlet and indian arm british columbia a laterally integrated time dependent numerical model of burrard inlet and indian arm is compared to time series of cyclesonde velocity and scalar data that have 10 m vertical resolution as long as deep water renewal is not occurring the model can reproduce the observed m2 and k1 tidal response in the basin of indian arm also although the rate of freshwater inflow into indian arm and burrard inlet is not large the simulated tidal response is noticeably improved if freshwater inflow is taken into account when deepwater renewal is observed to occur the model also simulates renewal but it does so poorly and the ability of the model to accurately simulate the m2 and k1 tide degrades significantly

sedimentation in glacial environments and the identification of tills and tillites in ancient sedimentary sequences abstract tills and tillites are defined and subdivided into primary tills comprising lodgement tills melt out tills and sublimation tills and secondary tills comprising flow tills and deformation tills they are defined on the basis of their mode of deposition which endows them with their distinctive properties another category of till that of supra till is defined on the basis of its debris source derived supraglacially from valley sides and nunataks which gives these tills a coarse grained character the processes of till deposition and of outwash sedimentation are associated in several recurrent combinations which allow the definition of three principal glacial sediment associations and land systems which define the character of the sequences within which tills tend to occur the criteria which allow tills of different genesis to be identified and to be distinguished from non till diamictons are reviewed there are several features which are uniquely characteristic of till but unfortunately these are few it has been found generally necessary to employ an array of characteristics which though not individually unique to till when taken together can be strong evidence for particular till types the recognition of several typical and repetitive facies sequences which form in the major glacial sedimentary environments can also be important indicators of till genesis

basalt weathering rates on earth and the duration of liquid water on the plains of gusev crater mars where martian rocks have been exposed to liquid water chemistry versus depth profi les could elucidate both martian climate history and potential for life the persistence of primary minerals in weathered profi les constrains the exposure time to liquid water on earth mineral persistence times range from 10 k y olivine to 250 k y glass to 1 m y pyroxene to 5 m y plagioclase such persistence times suggest mineral persistence minima on mars however martian solutions may have been more acidic than on earth relative mineral weathering rates observed for basalt in svalbard norway and costa rica demonstrate that laboratory ph trends can be used to estimate exposure to liquid water both qualitatively mineral absence or presence and quantitatively using reactive transport models qualitatively if the martian solution ph 2 glass should persist longer than olivine therefore persistence of glass may be a ph indicator with evidence for the ph of weathering the reactive transport code crunchflow can quantitatively calculate the minimum duration of exposure to liquid water consistent with a chemical profi le for the profi le measured on the surface of the exposed martian rock known as humphrey in gusev crater the calculated exposure time is 22 k y which is a minimum due to physical erosion if correct this estimate is consistent with short term episodic alteration accompanied by ongoing surface erosion more of these depth profi les should be measured to illuminate the weathering history of mars

mobility and fluxes of major minor and trace metals during basalt weathering and groundwater transport at mt etna volcano sicily abstract the concentrations and fluxes of major minor and trace metals were determined in 53 samples of groundwaters from around mt etna in order to evaluate the conditions and extent of alkali basalt weathering by waters enriched in magma derived co 2 and the contribution of aqueous transport to the overall metal discharge of the volcano we show that gaseous input of magmatic volatile metals into the etnean aquifer is small or negligible being limited by cooling of the rising fluids basalt leaching by weakly acidic co 2 charged water is the overwhelming source of metals and appears to be more extensive in two sectors of the s sw paterno and e zafferana volcano flanks where out flowing groundwaters are the richest in metals and bicarbonate of magmatic origin thermodynamic modeling of the results allows to evaluate the relative mobility and chemical speciation of various elements during their partitioning between solid and liquid phases through the weathering process the facts that rock forming minerals and groundmass dissolve at different rates and secondary minerals are formed are taken into account at mt etna poorly mobile elements al th fe are preferentially retained in the solid residue of weathering while alkalis alkaline earth and oxo anion forming elements as se sb mo are more mobile and released to the aqueous system transition metals display an intermediate behavior and are strongly dependent on either the redox conditions mn cr v or solid surface related processes v zn cu the fluxes of metals discharged by the volcanic aquifer of etna range from 7 0 10 3 t a th to 7 3 10 4 t a na they are comparable in magnitude to the summit crater plume emissions for a series of elements na k ca mg u v li with lithophile affinity but are minor for volatile elements basalt weathering at mt etna also consumes about 2 1 10 5 t a of magma derived carbon dioxide equivalent to ca 7 of contemporaneous crater plume emissions the considerable transport of some metals in etna s aquifer reflects a particularly high chemical erosion rate evaluated at 2 3 10 5 t a enhanced by the initial acidity of magmatic co 2 rich groundwater

a lava flow without a source the cohassett flow and its compositional components sentinel bluffs member columbia river basalt group abstract the eruption of sentinel bluffs member lava flows at approximately 15 5 ma marked the end of grande ronde basalt volcanism the most voluminous period of the columbia river basalt group more than 10 000 km3 of lava erupted from northerly trending feeder dikes in eastern washington and northern oregon and flowed westward down an ancestral paleoslope covering more than 169 700 km2 of the flood basalt province the sentinel bluffs member consists of six phases or types defined by their compositions lava flows having the first compositional type were the most voluminous and reached the pacific ocean the volume of later lava flows having the other compositional types declined with time until the final eruption produced the second largest volume of basalt at the source area compositional variation in sentinel bluffs lava flows is relatively small this homogeneity allows the individual compositional types and thus phases of the eruption to be easily recognized farther west however composition

the effects of weathering on rare earth element y and ba abundances in tertiary basalts from southeastern australia tholeiitic basalts showing anomalously high ba y and rare earth element ree concentrations occur within the tertiary newer volcanic province of victoria and these geochemical characteristics are related to incipient alteration accompanying weathering ree and y released during weathering of basalts are retained either in secondary phosphate or clay minerals and in rocks showing very high ba concentrations the ba is present as baso4 leaching experiments suggest that glassy or fine grained rocks are more likely to release ree y and ba while more extensively altered rocks are likely to hold these elements probably because they substitute in or are adsorbed on clay minerals or because secondary baso4 and ree phosphates are resistant to acid leaching samples taken sequentially across a weathering profile in a tholeiitic basalt flow from fresh to intensively altered rock illustrate that in the very earliest stages of alteration extreme variations in the abundances of ba y and ree can occur this is reflected in the broad patterns of trace element behaviour manifested by an extensive analysed sample suite from the victorian newer volcanic province where there is no correlation between anomalous enrichments in ba y or ree and the level of incipient alteration ba anomalies are not necessarily accompanied by abnormal y and ree behaviour and this is probably because the mobility of each trace element is a function of a the ionic radius and charge of the ionic species it forms in solution b local groundwater parameters such as eh ph groundwater flux and concentrations in the groundwater of species such as so42 and c the secondary mineral assemblages developed in a particular situation sr isotopic compositions are not strongly affected by incipient weathering and do not show significant changes until alteration has progressed to the point where plagioclase begins to break down the study illustrates that relatively slight alteration at the earliest stages of weathering can produce drastic changes in the concentrations of ree y and ba and petrographic assessment of the freshness of samples is not precise enough to eliminate prior to analysis cases where these effects may be manifested where weathering has caused changes in abundance patterns these may be recognised by careful comparisons of appropriate elemental ratios e g ba rb throughout a particular analysed sample suite

a numerical model of stratified circulation in indian arm british columbia a laterally integrated numerical model has been developed for the study of stratified circulation in inlets the model is time dependent and includes advective terms horizontal and vertical turbulent diffusion of momentum and salt and variations in width and depth initial and boundary conditions based on winter measurements in burrard inlet and indian arm were used to study the inlet s response to tidal forcing the friction term was tuned to match calculated and observed dissipation rates evidence for a standing wave pattern in the response of the m2 and k1 tidal constituents is discussed a comparison of model results with cyclesonde current meter time series at two locations in indian arm is consistent with resonance a modal decomposition of the calculated response shows that most of the energy is contained in the barotropic and first baroclinic modes with the former dominating near the sill and the latter dominating in the deep basin second mode energy was significant for the k1 at some locations

influence of stratification and topography upon internal wave spectra in the region of sills 1 a non hydrostatic model in vertical cross section form is used to examine the role of sill width and buoyancy upon the energy cascade into the internal tidal band and higher frequencies in sill regions power spectra analysis of computed time series show that as sill width is reduced the energy transfer from the baroclinic tide to its higher harmonics is reduced however there is an increase in energy at higher frequencies corresponding to lee wave periods in addition internal mixing on the lee side of the sill increases the addition of small scale topography on the sill slope produces a similar spectral change in the internal wave distribution and mixing for a narrow sill the addition of a surface buoyant layer with a higher buoyancy frequency significantly reduces the energy cascade to higher frequencies with a corresponding reduction in mixing the associated spectra have characteristics resembling wide sill topography

the rate of inflow and mixing during deep water renewal in a sill fjord we obtained high resolution data on a deep water renewal in the basin of gullmar fjord sweden using an autonomous profiling platform in the middle of the fjord where the platform is anchored renewal starts with the passage of a gravity current front and continues with a steady thickening of the new oxygen rich low nitrate bottom layer and an associated lifting of the old oxygen depleted high nitrate bottom water the basin continuously fills to sill level during a period of 10 d at the mouth of the fjord a three layer structure develops renewal is driven by the density difference between the intermediate water inside and the new deep water outside the fjord the volume flux is well predicted by a hydraulic exchange model in which the upper layer plays a passive role local upwelling and downwelling of the upper halocline cause fluctuating baroclinic currents during renewal but these seem to have little influence on the average volume flux of new deep water entrainment rates are small and the associated volume flux increase seems to be balanced by detrainment

melt out till in the edmonton area alberta canada till at two localities in the edmonton area alberta was formed mainly by passive melt out from glacier ice and not by lodgment by active ice or as a result of supraglacially derived flows this interpretation is based on the implications of in situ stratified glacial sediment below and within till and of large unlithified clasts of sediment derived from subtill deposits the interpretation is also supported by more general regional stratigraphic and structural observations such associated properties as subtill deformation a sharply planar till preglacial sediment contact sole marks and fabric support formation by melt out or illustrate local exceptions to this process regionally consistent preferred orientation of clasts is interpreted to represent preferred englacial orientation collective analysis of the principal eigenvectors of individual englacial fabrics and flow or resedimented till fabrics from a modem glacial environment and similar analysis for till at villeneuve near edmonton show the edmonton till to occupy the intermediate position in terms of orientation strength predicted by the melt out hypothesis in places preferred orientation is considered to have been disturbed by flow and diapirism induced by the process of thaw consolidation thus preferred clast orientation in till may show considerable deviation from a regional trend stratigraphy and sedimentology are used to classify the till and to relate individual exposures to regional environments of deposition

controls on rind thickness on basaltic andesite clasts weathering in guadeloupe abstract a clast of low porosity basaltic andesite collected from the b horizon of a soil developed on a late quaternary volcaniclastic debris flow in the bras david watershed on basse terre island guadeloupe exhibits weathering like that observed in many weathered clasts of similar composition in other tropical locations specifically elemental profiles measured across the core rind interface document that primary minerals and glass weather to fe oxyhydroxides gibbsite and minor kaolinite in the rind the earliest reaction identified in the core is oxidation of fe in pyroxene but the earliest reaction that creates significant porosity is plagioclase dissolution elemental loss varies in the order ca na k mg si al fe p ti consistent with the relative reactivity of phases in the clast from plagioclase pyroxene glass apatite ilmenite the rind surrounds a core of unaltered material that is more spherical than the original clast the distance from the core rind boundary to a visually prominent rind layer l was measured as a proxy for the rind thickness at 36 locations on a slab cut vertically through the nominal center of the clast this distance averaged 24 4 3 1 mm maximum and minimum values for l 35 8 and 20 6 mm were observed where curvature of the core rind boundary is greatest 0 12 mm 1 and smallest 0 018 mm 1 respectively extrapolating from other rinds in other locations the rate of rind formation is estimated to vary by a factor of about 2 from 4 to 7 10 14 m s 1 from low to high curvature the observation of a higher rate of rind formation for a higher curvature interface is consistent with a diffusion limited model for weathering rind formation the diffusion limited model predicts that like rind thickness values of the thickness of the reaction front h for a given reaction defined as the zone over which a parent mineral such as plagioclase completely weathers to rind material should also increase with curvature values of h were quantified as a function of interface curvature using bulk chemical analysis 500

experiments on the production of transverse grain alignment in a sheared dispersion a series of experiments was designed to investigate grain orientation in flows with concentrations of granular solids in the range from 0 5 to 15 fourteen experiments were carried out in which sand sized material was dispersed in liquid plaster of paris and the dispersion allowed to flow down a slope until it came to rest the preferred orientation of the grains was then estimated by measuring the anisotropy of magnetic susceptibility of specimens cut from the solidified flows five of the experiments showed signs of deformation both in the gross characteristics of the flow and in the grain alignment the remaining nine had grain alignment dependent on grain concentration at concentrations of 1 2 and less and 11 1 and more by volume alignment of long axes was parallel to flow these observations were consistent with the existing theories for low concentrations in which preferred alignment is shown to result from the varying rate of rotation of grains in a shearing flow and for high concentrations in which preferred alignment results from the transfer of angular momentum between colliding grains at some intermediate concentrations transverse alignment was observed a theoretical explanation combining the theories of the extreme cases is suggested the observation of transverse alignment is compared with a similar observation in some turbidites

quaternary sediments in central edmonton alberta canada stratigraphy distribution and geotechnical implications abstract borehole logs were used to determine the stratigraphy and distribution of sedimentary units in central edmonton the quaternary sediments overlying upper cretaceous sedimentary bedrock consist of preglacial fluvial sand and some gravel glaciofluvial sand and gravel a glacial diamicton complex composed of melt out and flow diamictons glaciofluvial sand and silt glaciolacustrine silt and clay and minor deposits of postglacial fluvial sand the glacial sediments represent deposition during one major glaciation in the late wisconsinan the diamicton complex has an intermediate stratigraphic position in the quaternary sequence is generally thick and laterally continuous and serves as a satisfactory substrate for many deep foundations and tunnels including part of the light rail transit system seepage and block failures during tunnelling in the diamicton complex are mainly due to abundant saturated sand lenses in the upper part of the complex the lateral continuity of the diamicton complex is interrupted by sand infilling a meltwater channel incised into bedrock tunnelling is difficult and costly within the sand due to seepage and collapse mapping of the meltwater channel and associated outwash deposits allowed adjustment of the tunnel alignment to avoid intersection with the channel over the meltwater channel deposits of outwash sediments and flow diamictons form a broad surface ridge

mineralogy of a soil chronosequence on andesitic lava in humid tropical costa rica abstract we studied a chronosequence of three soils developed on andesitic lavas in humid tropical costa rica in order to investigate mineralogical development and to evaluate the importance of time versus other soil forming factors morphological chemical and mineralogical methods were used to unravel evolution of the soils primary minerals in the

experimental evidence for mobility of zr and other trace elements in soils a soxhlet extraction was carried out over a period of 27 d on a column comprising 3 cm of quartz overlain by 4 cm of soil from the b horizon and then 1 cm of soil from the a horizon of a granitic podzol major and trace elements were leached from the column and accumulated in a reservoir at the base of the column total loss of elements from the soil over the course of the experiment ranged from 0 002 to 1 wt with major elements and the light and heavy rare earth elements ree showing the largest percentage losses zirconium 0 002 and then al 0 008 showed the lowest percentage loss the light ree were leached out of the soil preferentially to the mid ree all elements showed accumulation by a factor of 2 to 11 in the quartz layers at the base of the column particularly in the upper first 1 cm of the quartz major elements were leached from the column at a rate of 0 02 to 0 59 mol h 1 whereas zr nd sm gd dy rb and sr were leached at the rate of 0 5 to 30 10 6 mol h 1 concentrations of other ree in the reservoir increased over the duration of the experiment but they were poorly correlated with time so leaching rates were not calculated normalization of the major element leaching rates to take into account the constant flushing of water through the column the average annual rainfall in the allt a mharcaidh catchment in scotland from where the soil was sampled and the cross sectional area of the soil in the column together with the temperature of the soil in the column 70 c compared with the average annual temperature of the allt a mharcaidh catchment 5 7 c gave major element release rates from the soil of 0 002 to 0 97 meq m 2 yr 1 depending on the choice of ea the dissolution activation energy which are generally less than those measured in the field of 0 1 to 40 9 meq m 2 yr 1 calculations showed that despite the redistribution and loss of zr from the column assumptions of zr mobility would have had a negligible effect on calculated element release rates of na ca fe and mg however significant underestimates of the release of k 5 ti 57 al 5 and si 10 as well as some trace elements e g nd 23 rb 54 sr 24 would have occurred concentrations of ca and sr leached from the column correlated well rsq 0 93 p 0 01 supporting the idea of the use of sr release as a proxy for ca release in weathering rate calculations the release rates and percentage loss of ree from the soil varied between elements indicating that ree distribution patterns of rocks and soils may not be preserved in drainage waters

the cycle of turbulent dissipation in the presence of tidal straining in regions of large horizontal density gradient tidal straining acts to produce a periodic component of stratification that interacts with turbulent mixing to control water column structure and flow a 25 h series of measurements of the rate of dissipation of turbulent kinetic energy e in the liverpool bay region of freshwater influence rofi have revealed the form of this interaction and indicate substantial differences from regions where horizontal gradients are weak in the rofi system there is a pronounced difference between flood and ebb regimes during the ebb the water column stratifies and strong dissipation is confined to the lower half of the water column by contrast during the flood stratification is eroded with complete vertical mixing occurring at high water and high values of dissipation 3 mw m23 extending throughout the water column the cycle of dissipation is therefore predominantly semidiurnal in the upper layers whereas near the bottom boundary the principal variation is at the m4 frequency as observed in regions of horizontal uniformity toward the end of the flood phase of the cycle tidal straining produces instabilities in the water column that release additional energy for convective mixing confirmation of increased vertical motions throughout the water column during the late flood and at high water is provided by measurements of vertical velocity and the error velocity from a bottom mounted acoustic doppler current profiler

the ciw index a new chemical index of weathering abstract a new chemical index of weathering that can be applied to modern soils and precambrian paleosis is proposed ciw al2o3 the value of this index increases as the degree of weathering increases and the difference between ciw index values of the silicate parent rock and soil or sediment reflects the amount of weathering experienced by the weathered material

trace element mobility during spheroidal weathering of basalts and andesites in hawaii and guatemala abstract trace element mobility has been studied in spheroidally weathered corestone shell complexes developed on late tertiary and quaternary volcanic rocks the parent materials are basalts and andesites related to 1 a subduction zone tecuamburro and moyuta volcanoes guatemala and 2 a hot spot hawaiian islands of oahu maui and hawai i the initial major element compositions are largely preserved in the corestones each corestone sample shows major element abundances characteristic of the different magmatic processes through which the lavas were generated however the changes in trace element compositions due to weathering show similar patterns in the corestone shell complexes independent of the tectonic setting and age element mobility within the different corestone shell complex was determined using an isovolumetric reference frame in this method bulk density is chosen as an independent measure of the extent of weathering based on volumetric concentrations the notion of element immobility cannot be applied to all the corestone shell complexes elements commonly assumed to be immobile e g zr ti and al vary in volumetric concentration for some corestone shell complex despite petrographic evidence of only minor weathering two corestones oahu and tecuamburro have become enriched in ree 3 relative to other lava flows from the same volcanoes and display negative ce anomalies the exfoliated shells from these complexes tend to have lower concentrations of ree 3 and have positive ce anomalies the fractionation of ce from the other rare earth elements ree is inferred to be a manifestation of changes in the valence state of ce from trivalent to tetravalent under oxidizing conditions in settings where the development of corestone shell complex is advanced an acidic solution can mobilize trivalent ree leach them out of more extensively weathered materials and transport them to less acidic portions of the regolith undergoing incipient weathering the precipitation of the ree 3 in the rinds and centers of the corestones are likely due to increases of the ph of the weathering solution systematic weathering induced ree behavior enrichment of most ree with lesser ce enrichment resulting in a negative ce anomaly can be discerned even in corestone samples that exhibit major element abundances and petrographic features otherwise similar to unweathered basalts and andesites

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

on the influence of topographic factors upon the oxygen consumption rate in sill basins of fjords abstract the rate of oxygen consumption has been estimated for 29 different sill basins of fjords all located in a relatively small area of the norwegian west coast it is found that cons the volume mean rate of oxygen consumption in a sill basin i e below the sill level is inversely proportional to the mean depth h b of the sill basin in addition it is demonstrated that cons decreases with increasing sill depth h t in an approximately linear fashion our results are compatible with a regionally horizontally homogeneous and downward decreasing vertical flux of organic carbon based on data from the present set of sill basins an empirical formula has been derived for cons as a function of h t and h b this may be looked upon as a regionally valid empirical fjord model which may be used to determine whether or not the oxygen consumption in a sill basin is normal

internal wave induced dispersion and mixing on a sloping boundary 1 a fluorescent dye tracer was released in a stratified water column above a sloping boundary revealing profound dispersive asymmetry initially the dye spread symmetrically in the vertical until the deeper portion became influenced by the bottom boundary layer bbl the shallower portion then spread rapidly up slope in a thin boundary layer influenced by highly non linear isopycnal distortions the deeper down slope portion of dye subsequently became detached from the boundary and intruded into the basin interior in three distinct layers along isopycnal surfaces the intrusions result from the gravitational collapse of mixing patches created by baroclinic flow over an irregular boundary the vertical separation of the layers matches the inverse topographic wavenumber up slope displacement of the dye is consistent with an advective diffusive balance near the sloping boundary controlled by slope angle and roughness horizontal diffusivities increased from 1 4 m2s 1 to 18 4 m2s 1 during the 4 day experiment

resistance to barotropic tidal flow in straits by baroclinic wave drag energy transfer from barotropic tides to baroclinic motions may take place at the ends of straits connecting stratified basins implying generation of internal waves propagating into the basins different aspects of this have been described in the literature including quantification of the energy transfer studies of the resulting internal tides and the relationship to diapycnal mixing in the basins however the accompanying resistance to oscillatory barotropic strait flows by so called baroclinic wave drag has not been implemented earlier in models for strait flow in the present paper a formulation for the instantaneous baroclinic wave drag force is suggested this leads to a linear relationship between the strait flow and the synoptic sea level difference between the adjacent basins the model is used to study tidal response in land locked basins the response is computed for three fjords where the resistance to the barotropic flow comes essentially from baroclinic wave drag it is concluded that the strait flow model handles baroclinic wave drag in a satisfactory way since the observed responses are well predicted by the model baroclinic wave drag should provide the major resistance to surface tides in the deep ocean which indicates its importance in a wider context several mechanisms may cause resistance to barotropic flow in straits and channels friction against the sea bed is certainly the most commonly considered type of flow resistance it is often modeled with a quadratic relationship between the bottom stress and the barotropic velocity using a drag coefficient to characterize the frictional properties of the sea bed another type of flow resistance is due to large scale longitudinal variations of the vertical cross sectional area of the strait causing contraction followed by expansion of the flow this class of flow resistance appropriately termed barotropic form drag includes the resistance caused by contraction expansion induced by the ends of straits having smaller vertical cross sectional areas than the adjacent basins in the cases of frictional drag and largescale form drag barotropic energy is transferred to turbulence in the bottom boundary layer in the strait and to large scale eddies in the expanding current downstream of the strait respectively the present paper however draws attention to a third class of resistance operating on oscillating barotropic strait flow it is due to generation of baroclinic internal waves in the adjacent stratified basins by the ends of the strait and is

soft zones in the glacial till in downtown edmonton high rise buildings in downtown edmonton have generally been founded on spread footings in glacial till early geotechnical work proposed a geological model comprising uniform very dense basal lodgement till however recent work shows that the till is more complex being variable in both material type and consistency a case history is described that exemplifies this variability it is concluded that early experience with the dense tills has led to an overconfident approach to soil investigation in this area and that a thorough site investigation is required

major element ree and other trace element behavior in amphibolite weathering under semiarid conditions in southern india abstract a body of komatiitic amphibolite an enclave within the archean high grade orthogneisses in southern india shows mild chemical weathering under semiarid conditions along fractures chemical weathering has advanced chemical index of alteration documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepackage ot2 ot1 fontenc newcommand cyr renewcommand rmdefault wncyr renewcommand sfdefault wncyss renewcommand encodingdefault ot2 normalfont selectfont declaretextfontcommand textcyr cyr pagestyle empty declaremathsizes 10 9 7 6 begin document landscape mathrm cia 53 end document cia of fresh documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage

the response of a strongly stratified fjord to energetic tidal forcing abstract the response of upper loch linnhe a strongly stratified scottish fjord to energetic tidal forcing is studied by new analysis of two observational data sets using a ship mounted acoustic doppler current profiler adcp and an undulating conductivity temperature depth ctd we are able to repeatedly sample over a tidal cycle at sufficiently high spatial and temporal resolutions to clearly define the tidal variability in the vertical and horizontal away from the near sill region horizontal velocities are generally orientated along the longitudinal axis of the fjord analysis of the along fjord velocities shows that at the m2 frequency there is a strong 1st mode internal tide with maximum horizontal velocity amplitudes of 23 4 cm s 1 the observed vertical structure of the complex amplitudes of the horizontal velocities are in close agreement with normal mode theory along fjord variations of the fitted amplitude and phase lags from further analysis of the two independent data sets show that the 1st mode internal tide is behaving as a standing wave within the near sill region the circulation is complicated by the formation of a horizontal gyre and a large perturbation in the density field on the flood tide these features are a response to the flood tide currents advecting denser water into the fjord in the form of a strong jet due to the narrow entrance sill being off centre to the axis of the fjord the strong flood tide jet gives rise to eddy formation as the incoming flood tide water is denser than the resident surface water of the fjord the tidal jet sinks and advects the resident water landwards giving rise to the observed density perturbations

deep water renewal in the upper basin of loch sunart a scottish fjord abstract recording current meters were deployed near the surface and bottom in the upper basin of loch sunart during the summers of 1987 1989 and 1990 the measurements revealed frequent though irregular deep water renewal events when the basin water was replaced by density driven intrusions the data suggested that these events were induced by wind enhanced estuarine circulation during periods of low fresh water runoff a semi implicit laterally integrated estuarine model was modified to allow variable vertical grid spacing and to permit the sea surface to move vertically through the grid both modifications being necessary in order to apply the model to the sea loch environment a turbulence closure scheme was also incorporated the model can simulate the evolution of the salinity field over periods of several weeks and was used to examine the mechanisms that induce deep water renewal model results suggested that very weak stratification in the basin is required for renewal to occur and indicated

weathering rind formation in buried terrace cobbles during periods of up to 300ka abstract weathering rinds formed in mesozoic sandstone and basalt cobbles buried in terrace deposits for up to 300 ka have been investigated the aim was to determine the formation process and elemental mass balances during rind development the ages of terraces distributed in the western part of fukui prefecture central japan have been determined as 50 ka 120 ka and 300 ka based on a tephro stratigraphic method detailed investigations across the weathering rinds consisting of microscopic observations porosity measurements and mineralogical and geochemical analyses using x ray diffractometry xrd x ray fluorescence xrf secondary x ray analytical microscopy sxam scanning electron microanalyser sem and electron probe microanalysis epma have been carried out the results revealed that the fe concentrations in the weathering rind of a basalt cobble slightly decreased from the cobble s surface rim towards the unweathered core in contrast in a sandstone cobble formed under the same environmental conditions over the same period of time there is an fe rich layer at some distance below the cobble s surface elemental mass balances across the rinds were determined by using open system mass balance i j calculations and show that the fe was precipitated as fe oxyhydroxides in the basalt cobbles although fe was slightly removed from the rims in sandstone cobbles on the other hand fe migrated along a fe concentration gradient by diffusion and precipitated as fe oxyhydroxide minerals to form the weathering rinds presumably precipitation was due to the relatively higher ph conditions caused by mineral dissolution within the pores principally involving calcite but probably also silicates including feldspar the detailed characterization of the weathering rinds revealed the influence of lithology on the accumulation and dissolution of fe oxyhydroxides causing weathering rinds with different characteristics to develop in different kinds of buried cobbles under the same conditions relatively large climatic changes in the study area did not cause discernable variations in the mean formation rates of the studied rinds which were in the order of 10 8 m a for both basalt and sandstone cobbles these rates are 1 2 orders of magnitude slower than those reported for tropical areas elsewhere most probably due to the lower rainfall in the studied area

slow chemical weathering in a semiarid climate changes in the mineralogy and geochemistry of subaerial lava flows in the deschutes river basin central oregon abstract the progression of mineral alteration and chemical changes of thirteen pairs of fresh and weathered surficial lava samples from the deschutes river basin of central oregon were studied to understand incipient weathering in a semiarid climate samples range from basalt to dacite in composition and quaternary to late miocene in age only the tertiary samples showed significant chemical weathering based on element mobility and mineral alteration the slight climatic variations between tertiary outcrop locations map 38 74 cm yr and mat of 7 2 7 6 c did not correlate with degree of weathering the susceptibility sequence of phases was determined to be glass olivine plagioclase orthopyroxene clinopyroxene fe ti oxides the older weathered samples have experienced significant leaching of mobile cations e g ca mg sr resulting in a lower calculated weathering index the tertiary weathered samples are enriched in ree particularly lree which is attributed to a lree phosphate found in association with allophane clay mineralization in plagioclase these samples also have a negative ce anomaly likely due to its tetravalent state in oxidizing conditions and subsequent lack of mobility in weathering solutions although there is a clear petrographic and chemical distinction between fresh and weathered lavas 2 ma the distinction between fresh and weathered samples is not evident in the quaternary lavas significant element mobility between sample pairs is closely correlated to the breakdown of plagioclase and orthopyroxene and the subsequent secondary mineralization of clays and or lree rich phosphates with the exception of plagioclase all the mineral phases in the deschutes lavas have persistence times or stability of at least one and possibly several orders of magnitude greater than the same phases in soil chronosequences or weathering rinds in more temperate and humid climates as a result elemental release rates and silicate fluxes are much lower under semiarid conditions and their role in the global carbon cycle should be examined more closely

formation of weathering rinds on andesite to explore the mechanisms of weathering rind formation rock properties of an andesite cobble were investigated the andesite cobble studied in this paper was taken from a fluvial terrace which formed around 290 ka bp in the nasuno ga hara area central japan the sampled cobble has a double weathering rind comprising an outer brown zone brown band and an inner pale grey zone white band with thicknesses of 3 mm and 7 mm respectively the boundary between the outer brown band and the inner white band is clearly defined whereas the boundary between the white band and the grey fresh looking interior of the rock is not so clearly defined mineralogical chemical chromatic and mechanical properties of the cobble were investigated in the laboratory the outer zone the brown band is characterized by high brittleness high feo fe2o3 content and low contents of cao mgo na2o and k2o the oxidation of iron accounts for the brown colour of the rind this outer zone is considered to have experienced both oxidation and dissolution the inner zone the white band is characterized by hardness reduction and the dissolution of alkali alkaline earth metals towards the surface of the cobble this inner band is considered to have experienced only dissolution the formation of the weathering rinds can be explained by changes in water movement directions in terrace deposits alkali alkaline earth metals dissolve when water is supplied to a cobble from the surrounding matrix subsequently the dissolved metals move out of the cobble accompanied by outward water movement when the subsurface water table is low the concentrations of cao mgo na2o k2o and al2o3 therefore decrease in both weathering bands but iron tends to remain as ferric hydroxides in the outer brown band processes of dissolution and oxidation have produced the brown band copyright 2001 john wiley sons ltd

glacigenic deposits at the edmonton convention centre edmonton alberta four main stratigraphic units are present at the edmonton convention centre site in downtown edmonton the lowermost sediment exposed is cretaceous sandstone of the horseshoe canyon formation this is overlain by preglacial sands and gravels of uncertain age which contain recumbent drag folds developed by glacial overriding of previously existing periglacial involutions these sediments are surmounted by a glacigenic complex consisting of subglacially modified sand and four till facies formed through passive melt out the uppermost quaternary sediment present is a proglacial lacustrine unit dominated by silts and clays with interbedded diamictons a single glacial episode is recorded in the sediments stratigraphic relationships with other exposures throughout the edmonton region indicate that the glacigenic complex formed during the final ice advance variation in the orientation of glacially induced deformations in the preglacial sands and gravels and the basal glacigenic sand indicate that the directi

basalt weathering across scales abstract weathering of silicate minerals impacts many geological and ecological processes for example the weathering of basalt contributes significantly to consumption of atmospheric carbon dioxide co2 and must be included in global calculations of such consumption over geological timeframes here we compare weathering advance rates for basalt wd where d and indicate the scale at which the rate is determined and surface area measured respectively from the laboratory to the watershed scales data collected at the laboratory weathering rind soil profile and watershed scales show that weathering advance rate of basalt is a fractal property that can be described by a fractal dimension dr 2 3 by combining the fractal description of rates with an arrhenius relationship for basalt weathering we derive the following equation to predict weathering advance rates at any spatial scale from weathering advance rates measured at the bet scale w d k 0 a d r 2 e e a r t here k0 is the pre exponential factor 1 29 107 mm3 mm 2 yr 1 ea is the activation energy 70 kj mol 1 and a is a spatial constant related to the scale of measurement of bet surface area 10 7 mm the term a d r 2 is the roughness the roughness fractal dimension can be conceptualized as a factor related to both the thickness of the reaction front and the specific surface area within the reaction front however the above equation can also be written in terms of a surface fractal dimension and the hypothetical average grain radius these fractal dimensions provide insight into reaction front geometry and should vary with lithology once the surface area discrepancy has been accounted for using this method we find a one to two order of magnitude range in weathering advance rates measured at any scale or temperature that can be attributed to factors such as changes in erosional regime parent lithology mechanism climate composition of reacting fluid and biological activity our scaled equation when used to predict global basalt co2 consumption based upon global lithologic maps yields an uptake flux 1 75 1013 mol co2 yr 1 within the predicted error of fluxes estimated based upon riverine measurements

the simulation of deep water exchange in a fjord indian arm british columbia canada abstract a numerical model is used to simulate deep water renewals that were observed to occur in burrard inlet indian arm over a time period of about 100 days during winter 1984 85 the renewals bottom water flowing from burrard inlet into indian arm occurred or intensified during neap tide and caused a steady increase in the density near the bottom in indian arm the model successfully reproduces the renewal events for a simulation time of at least 85 days it uses a mellor yamada level two turbulence closure scheme for which the local turbulent energy production is balanced by local dissipation and for which the turbulent length scale is prescribed the length scale varies linearly with depth near the surface and bottom and is constrained to never be larger than 1 20 of the water depth and 2 the ozmidov length scale a lower bound is imposed on the vertical diffusion coefficients that depends on the brunt vaisala frequency n its magnitude for a given n is different in burrard inlet and in

laurentide glaciation in west central alberta a single late wisconsinan event the grande prairie region in west central alberta shows evidence of late wisconsinan laurentide glaciation in the form of a widespread till containing abundant erratic clasts derived from the canadian shield two sections located on the smoky river at watino and on the simonette river 80 km to the southwest expose sediment lying stratigraphically below the till a similar sequence is exposed in both localities 5 10 m of coarse quartzite gravel overlain by a thick sequence of sand and silt the gravel contains no laurentide erratics and is thus preglacial the contact between the basal gravel and the overlying sand and silt is sharp and conformable 14c dates from the base of the simonette section and throughout the watino section suggest a middle wisconsinan age thus the sediment exposed is interpreted as a conformable middle wisconsinan sequence the sedimentary sequences were deposited in a moderate to low energy braided stream system flowing towards the north the general fining up trend in the

a numerical model of the circulation in knight inlet british columbia canada abstract during spring 1988 a period of low freshwater runoff and summer 1989 a period of high freshwater runoff month long observations of velocity temperature and salinity were made throughout the water column in knight inlet both up inlet and down inlet of the sill measurements were made at depths of 2 4 6 9 and 12 m using s4 current meters at depths down to about 200 m using profiling current meters and at depths deeper than 200 m using aanderaa current meters anemometers were deployed at two locations along the inlet a laterally integrated two dimensional numerical model of the inlet that uses the mellor and yamada level 2 5 turbulence closure scheme and that accounts for the combined influence of the winds tides and freshwater runoff has been used to produce 30 day simulations of the velocity and density field in the inlet the vertical coordinate is transformed in the model so that very fine vertical resolution can be attained near the surface even though the tidal range is larg

partition of energy loss from the barotropic tide in fjords abstract as the barotropic tide propagates into and out of a fjord it loses energy to friction internal tides and high frequency internal waves estimates of these losses for three british columbia fjords using current meter data indicate that friction is negligible in two but important in one inlet the length and depth of the sill determines the importance of friction when friction is not important most of the energy lost goes into the internal tide but less than half of this energy propagates away from the sill simple models of the internal tide predict the correct energy transfer to satisfy an energy budget but do not agree with observations of the internal tidal energy flux away from the sill energy loss from the internal tide in or near the generation zone would account for the discrepancy the energy flux of the high frequency internal wave field is relatively small about 2 of the energy lost

chemical weathering in a tropical watershed luquillo mountains puerto rico i long term versus short term weathering fluxes abstract the pristine rio icacos watershed in the luquillo mountains in eastern puerto rico has the fastest documented weathering rate of silicate rocks on the earth s surface a regolith propagation rate of 58 m ma 1 calculated from iso volumetric saprolite formation from quartz diorite is comparable to the estimated denudation rate 25 50 ma 1 but is an order of magnitude faster than the global average weathering rate 6 ma 1 weathering occurs in two distinct environments plagioclase and hornblende react at the saprock interface and biotite and quartz weather in the overlying thick saprolitic regolith these environments produce distinctly different water chemistries with k mg and si increasing linearly with depth in saprolite porewaters and with stream waters dominated by ca na and si such differences are atypical of less intense weathering in temperate watersheds porewater chemistry in the shallow regolith is controlled by closed system recycling of inorganic nutrients such as k long term elemental fluxes through the regolith e g si 1 7 10 8 moles m 2 s 1 are calculated from mass losses based on changes in porosity and chemistry between the regolith and bedrock and from the age of the regolith surface 200 ma mass losses attributed to solute fluxes are determined using a step wise infiltration model which calculates mineral inputs to the shallow and deep saprolite porewaters and to stream water pressure heads decrease with depth in the shallow regolith 2 03 m h2o m 1 indicating that both increasing capillary tension and graviometric potential control porewater infiltration interpolation of experimental hydraulic conductivities produces an infiltration rate of 1 m yr 1 at average field moisture saturation which is comparable with libr tracer tests and with base discharge from the watershed short term weathering fluxes calculated from solute chemistries and infiltration rates e g si 1 4 10 8 moles m 2 s 1 are compared to watershed flux rates e g si 2 7 10 8 moles m 2 s 1 consistency between three independently determined sets of weathering fluxes imply that possible changes in precipitation temperature and vegetation over the last several hundred thousand years have not significantly impacted weathering rates in the luquillo mountains of puerto rico this has important ramifications for tropical environments and global climate change

glacial sedimentary processes and environmental reconstruction based on lithofacies glacigenic sediments exposed in pits around villeneuve near edmonton alberta are subdivided into facies based on grain size sedimentary structure glacially induced deformation and faulting and groove marks two diamicton facies are recognised one of which is interpreted as a primary till deposited directly from glacier ice and the other as a product of mass movement the diamicton facies are closely associated with current bedded facies interpreted as fluvioglacial deposits the stratigraphic sedimentological and tectonic aspects of these fluvial deposits suggest subglacial deposition in channels and cavities at any one place the glacier appears to have alternated between being attached to the bed causing thrusting and sole marking and being separated from the bed by a cavity in which fluvial and mass movement sediments accumulated the net result is a highly complex and laterally variable stratigraphy produced by a single glacial advance the correct interpretation of such sequences is essential if lithostratigraphy is to be used to establish glacial history in addition the interpretations presented here have implications regarding the formation of soft zones in till they indicate that the soft zones are beds of sorted sediment redeposited by mass movement

yttrium the immobility mobility transition during basaltic weathering trace elements have been used as provenance indicators of igneous rocks for many years even though the conditions under which they remain immobile during subaerial weathering have not been thoroughly defined we have used a novel geochemical and quantitative mineralogical data set of variably weathered basaltic rocks from northeast ireland to investigate the immobility of various elements titanium and niobium seem to be the most immobile of all elements relative to these elements zirconium is predominantly depleted but is also locally enriched yttrium displays a marked depletion from the early stages of weathering during the growth of clay minerals yttrium zirconium and their ratios with other elements should thus be used with caution as provenance indicators unless the rocks show no detectable signs of weathering

subaqueous outwash deposits in the ingraham ridge chazy new york a 1 5 km segment of ingraham ridge a stratified sand and gravel ridge in northeastern new york is composed dominantly of subaqueous outwash deposits the core of the ridge segment may include subordinate subglacial tunnel deposits the subaqueous outwash is composed mainly of interbedded sediment gravity flow bar dune and ripple deposits that occur in channels sheetlike cross stratified and cross laminated deposits also are common particularly on the distal western margin of the ridge segment the ridge segment is draped by glaciolacustrine laminated sand silt and clay and glaciomarine massive mud westward decrease in grain size and scale of sedimentary structures is attributed to confining ice walls of an asymmetric embayment sediments are deformed in part by the melting of adjacent and buried ice the ridge was modified during champlain sea regression and the reworked deposits were colonized by shallow water organisms reworking may have been minor and the broad low morphology of the ridge

towards a weathering model of mount lamington ash papua new guinea abstract the mount lamington ash halo has been studied at six sites both close to and distant from the volcano negligible alumina occurs in the seepage waters from the ash and so alumina is assumed constant during weathering in andesitic ashes weathering to allophane an approximation to a first order reaction was found in 1968 and is confirmed here with given infiltration and silica concentration the weathering rate constant decreases with increasing content of weathering minerals and increasing thickness of ash being weathered the rate constant also increased with increasing infiltration and decreasing median size of the ash the total weathering rate is the product of the thickness percentage of ash being weathered and the weathering rate constant the total weathering rate is the same for thick less weathered proximal ashes as it is for the thin more weathered distal ashes first order kinetics imply a high rate of leaching decreasing with time but continual burial under new ash at a nearly constant rate leads to linear leaching of the upper part of the profile the leaching rate decreases exponentially with depth and appears to ignore buried topsoil barriers it is possible to construct weathering models exploring the rate constant and to link it with leaching rates two thirds of the loss on weathering is silica and there is a total leaching rate of 3 4 mg sio 2 cm 2 year 1 as on basalt in hawaii and on andesite in st vincent water analyses show silica concentrations in the ash of 17 35 ppm and in draining streamlets of 9 20 ppm measured concentrations agree with calculated concentrations from the weathering data silica concentrations are similar in other humid tropical rivers

water mass modification in an arctic fjord through cross shelf exchange the seasonal hydrography of kongsfjorden svalbard 1 kongsfjorden and the west spitsbergen shelf is a region whose seasonal hydrography is dominated by the balance of atlantic water arctic waters and glacial melt regional seasonality and the cross shelf exchange processes have been investigated using conductivity temperature depth ctd observations from 2000 2003 and a 5 month mooring deployment through the spring and summer of 2002 modeling of shelf fjord dynamics was performed with the bergen ocean model observations show a rapid and overwhelming intrusion of atlantic water across the shelf and into the fjord during midsummer giving rise to intense seasonality pockets of atlantic water from the west spitsbergen current form through barotropic instabilities at the shelf front these leak onto the shelf and propagate as topographically steered features toward the fjord model results indicate that such cross front exchange is enhanced by north winds normally atlantic water penetration into the fjord is inhibited by a density front at the fjord mouth this geostrophic control mechanism is found to be more important than the hydraulic control common to many fjords slow modification of the fjord water during spring reduces the effectiveness of geostrophic control and by midsummer atlantic water intrudes into the fjord switching from being arctic dominant to atlantic dominant atlantic water continues to intrude throughout the summer and by september reaches some quasi steady state condition the fjord adopts a cold or warm mode according to the degree of atlantic water occupation horizontal exchange across the shelf may be an important process causing seasonal variability in the northward heat transport to the arctic

overturning and dissipation caused by baroclinic tidal flow near the sill of a fjord basin abstract dissipation time series and moored velocity and density time series on the inner slopes of the gullmar fjord sill showed that the internal tides generated at the sill radiated to the head of the fjord were reflected and then radiated back to the sill where they dissipated their energy mainly below sill level a large amount of the dissipation was caused by a transitional flow at a particular phase of the internal tide when the bottom layer descended down the sill slope and had to pass a constriction set up by a submarine hill the inward baroclinic bottom layer flow transformed into a supercritical bottom jet which separated from the bottom just downstream of the constriction a large fraction of the dissipation took place in the successive rebounding region the hydraulic jump above the bottom jet where overturns of the same size as the vertical extent of the rebounding region were observed more than half of the dissipation was happening in the bottom boundary layer below the jet durin

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

a numerical study of the tidal circulation and buoyancy effects in a scottish fjord loch torridon 1 the tidal and buoyancy driven circulation in loch torridon a scottish fjord is investigated using a three dimensional hydrostatic primitive equation model the predictions from the model have been quantitatively compared to available data gathered between 1998 and 2001 the model performed well in reproducing the tidal characteristics and density evolution of the fjord over the 3 month simulation period results show that tidal currents are dominated by the constraint imposed on the flow by the shallow sill separating the upper and middle basins the flow is strongly accelerated during flood and ebb tides and significant residual currents are generated that may influence exchange and residence times of the middle basin a strong baroclinic response to the flow over the sill is predicted throughout the fjord with a propagating linear m2 tide displacing isopycnals vertically by up to 32 m at the sill the formation of stationary lee waves on both flood and ebb tides is predicted with the wave generated during flood tide being notably larger as the growth of the ebb wave is inhibited by deep dense water this allows more energy to transfer into the seaward propagating internal tide as the tidal flow weakens the lee waves propagate over the sill and upstream estimates of the total vertical turbulent buoyancy flux in the fjord are made and the distribution of mixing over a tidal cycle is shown vertical mixing is seen to be highly spatially and temporally variable and strongly linked to the presence and dissipation of lee waves near the sill

a model study of density intrusions into and circulation within a deep silled estuary puget sound a laterally averaged hydrodynamical model is used to investigate episodic intrusions of denser more oceanic water across the shallow double silled entrance of puget sound and the resulting circulation within the interior deep basin tidal freshwater discharge and wind effects are also encompassed in model results model simulations were made of the 4 month period from december 1983 through march 1984 during that period hourly measurements of currents and salinity were made at the estuary entrance and on four moorings in the interior basin the first 60 days of salinity data were used with the model to choose rates of vertical turbulent mixing and the lag times between fresh water appearance at river gauges and its arrival in the main basin of the sound comparison of model results with the full 120 days of salinity and velocity data shows that the model incorporates the important circulation features of this estuary the model was then used to study intrusions and mixing in the sill region the model identifies these factors as controls on the occurrence and strength of intrusions the trans sill salinity gradient the intensity of tidal stirring and mixing over the sills the supply of fresher surface water resulting from river runoff and the winds time series of salinities in the interior basin show local maxima following local maxima in the trans sill salinity difference vertical transport in the sill region at both tidal and subtidal time scales is dominated by advection rather than diffusion though much of the vertical exchange occurs over the shallower sill a depth depression between the two entrance sills appears to be the site of significant overturning downwelling of surface water occurs on the landward side of both sills substantial freshening of the interior basin occurs during the winter months because river discharges are large and are stirred downward in the sill region to be entrained into landward bottom flows extraordinarily large river discharges can suppress the effect of large trans sill salinity differences with the effect of weakening potential intrusions winds can indirectly influence intrusions by longitudinally positioning fresher river influenced surface water in the sill region winds can directly influence intrusions via bottom compensation flows in admiralty inlet with northward winds encouraging intrusions and by changing salinities at the entrance to the sound and thus the trans sill salinity gradient

response of benthic fauna and changing sediment redox profiles over a hypoxic gradient the koljofjord is an enclosed stratified fjord on the swedish west coast with hypoxic anoxic bottom water during most of the year in the winter 1999 2000 the water in the entire fjord was re oxygenated after a period of stagnation but the following summer oxygen concentrations declined to below 1 ml l 1between 20 and 40 m depths the objectives of this study were to investigate the structure of benthic communities along a depth gradient of declining oxygen concentrations and the impact of fauna on sediment redox conditions the vertical distribution of the fauna in the sediment was restricted to the upper few centimetres dominant species at most stations were the burrower capitella capitata and the tube builder pseudopolydora antennata the species found in the fjord are probably not particularly tolerant towards hypoxia but they have life history traits that facilitate a rapid colonization following improved oxygen conditions the depth of the redox potential discontinuity rpd layer a recognizable division zone between oxidized sub oxic and reduced chemical conditions is dependent on infaunal activity e g burrows tubes and feeding voids measurement of apparent rpd arpd from sediment profile images spis compared well to electrode measurement of rpd we conclude that a digital analysis of arpd from images has many advantages compared to rpd measurements by electrodes