change in climate ocean and ice sheet conditions in the ross embayment antarctica at 6 ka evidence from the ross embayment antarctica suggests an abrupt cooling and a concomitant increase in sea ice cover at about 6000 sp 6 ka stable isotope delta d concentrations in the taylor dome ice core at the western edge of the ross embayment decline rapidly after 6 ka and continue to decline through the late holocene methanesulfonic acid concentrations at taylor dome show opposite trends to delta d sediment cores from the western ross sea show a percentage minimum for the sea ice diatom fragilariopsis curta between 9 and 6 ka when taylor dome delta d values are highest followed by an increase through the late holocene radiocarbon dates from raised beach deposits indicate that the retreat of ice shelves in the ross embayment ceased atabout 6 ka coincident with the environmental changes inferred from the sediment and ice core records the similarity in timing suggests an important role for climate in controlling the evolution of ice shelf margins following the end of the last 9 glaciation

timing of millennial scale climate change at siple dome west antarctica during the last glacial period using atmospheric methane and the isotopic composition of o2 as correlation tools we place the dd record of ice from the siple dome west antarctica ice core on a precise common chronology with the gisp2 greenland ice core for the period from 9 to 57 ka the onset of major millennial warming events in siple dome preceded major abrupt warmings in greenland and the pattern of millennial change at siple dome was broadly similar though not identical to that previously observed for the byrd ice core also in west antarctica the addition of siple dome to the database of well dated antarctic paleoclimate records supports the case for a coherent regional pattern of millennial scale climate change in antarctica during much of the last ice age and glacial interglacial transition

rare earth element geochemistry of colour lake an acidic freshwater lake on axel heiberg island northwest territories canada a lake column profile was collected in 24 m of water from colour lake axel heiberg island northwest territories canada in early june of 1991 beneath 1 8 m of lake ice the rare earth element ree concentrations of the acidic fresh waters of colour lake were analyzed along with the major solute chemistry in order to investigate ree distribution and speciation in the low ph waters previous studies indicate the lake is dominated by ca2 mg2 and so42 and has no measurable carbonate alkalinity shale normalized ree patterns for the lake waters are all enriched in the middle ree s mree s as compared to the light ree s lree s and heavy ree s hree s dissolved ree concentrations in colour lake e g 2 3 22 nmol kg 1 for nd mean value of 20 nmol kg 1 are typically less than values obtained for the acid saline waters of the lake tyrrell playa system in australia as well as the slightly acidic groundwaters of the carnmenellis region of england but greater than ree concentrations measured in the alkaline saline waters of mono lake california u s a the speciation of the ree s in colour lake was modelled based on the major solute chemistry using a combined specific ion interaction and ion pairing model these calculations suggest that in the relatively high sulfate low ph waters of colour lake the ree s exist as either free metal so42 or f complexes our calculations indicate that so42 complexes dominate over the free metal and fluoride species for the majority of the ree s in the lake water and that in general for acidic high sulfate waters sulfate complexes with the ree s may increase the dissolved concentrations of the ree s over natural waters where relatively low sulfate concentrations prevail

long term bedload mobility in gravel bed rivers using iron slag as a tracer abstract bedload dispersion is evaluated in gravel bed rivers using slag elements from ironworks established along rivers in the ardenne region between the fourteenth and the nineteenth centuries large quantities of slag were dumped close to these rivers or even directly into the channels for centuries slag elements were dispersed in the bedload and transported by floods of varying importance consequently slag may be considered as a reliable tracer to analyze bedload dispersion over several centuries the size of slag elements was studied along 16 ardenne rivers the longitudinal size trend of the largest slag particles allows the effective competence of these rivers to be determined between 19 and 129 mm for rivers where specific stream power for the bankfull discharge ranges between 20 and 134 w m a direct relationship doesn t exist between these two parameters as the size of slag elements must be considered with regard to the d 50 of the bed selective transport was analyzed directly downstream of the input sites the sorting distance varies from river to river and depends on the velocity of the coarse elements introduced into the river since the inception of the iron industry downstream of two metallurgic sites the slag propagation fronts were located as the periods of activity at these sites are known from historical studies the virtual velocity of bedload movement in these rivers was estimated to be 2 4 km century

formation of alunite jarosite and hydrous iron oxides in a hypersaline system lake tyrrell victoria australia abstract alunite kal 3 so 4 2 oh 6 and jarosite kfe 3 so 4 2 oh 6 are common weathering products of aluminosilicates and pyrite long range transport of the constituents forming these minerals and the subsequent deposition of alunite and jarosite in an evaporite setting have not been previously documented such conditions for the occurrence of alunite and jarosite were investigated in a hypersaline system where acid groundwater enriched in k al fe iii and so 4 enter a saltplaya lake sediment cores were studied by thin section xrd and sem eds groundwater and pore water chemistries were also analyzed the results show that alunite and jarosite occur together or as individual layers and cements within the top 20 cm of the sediments where the groundwater is most concentrated due to evaporation hydrous fe oxides also occur as cements or vein fillings with the alunite and jarosite but are distributed throughout the 70 cm sediment column studied the results are consistent with a model in which alunite and jarosite precipitate as a result of the evaporation of water thermodynamic modeling indicates that the pore water in the playa sediments maybe in equilibrium with alunite jarosite and hydrous fe oxides

major features of glaciochemistry over the last 110 000 years in the greenland ice sheet project 2 ice core major chemical species cl no3 so42 na nh4 k mg2 ca2 and 18o covering the last 110 000 years from the greenland ice sheet project 2 gisp2 ice core were utilized in this study in order to reconstruct the soluble chemistry of the atmosphere over greenland and interpret major climate events that have affected the region during the holocene the major chemical species and 18o do not display any significant relationship however a strong inverse correlation was found between concentrations of the major chemical species and 18o a proxy for temperature during the last glacial period suggesting that in general during periods of decreased temperature there is an increase in atmospheric chemical loading examination of changes in major chemical composition over the last 110 000 years of the gisp2 ice core reveals that during the holocene the atmosphere was acidic during inters t adials the atmosphere was neutral or alkalescent and during stadials the atmosphere was alkaline in addition the relative abundance of major chemical species varied during the holocene stadials and interstadials during the holocene nh4 and no3 are the dominant cations and anions while ca2 and so42 are the dominant cations and anions during the stadials and inters t adials this suggests that source regions or types differed between the holocene and the last glacial period in addition changes in chemical composition and changes in chemical ratios also indicate that source regions differed during the holocene stadials and interstadials twenty four previously identified dansgaard oeschger stadial interstadial events dansgaard et al 1993 were in the gisp2 chemical series the duration of the stadials is inversely correlated with variations in sea level over the last glacial period i e the more extensive the northern hemisphere ice sheet the longer the duration of the stadial there is also a close correspondence between the duration of interstadials and the timing of heinrich events massive icebergs discharged into the ocean in the gisp2 ice core long up to 2000 years warm periods follow each heinrich event suggesting perhaps that enhanced deep water circulation is re initiated following heinrich events

response of a gravel bed river to dam closure insights from sediment transport processes and channel morphodynamics this work deals with the impacts of dams on large gravel bed rivers in terms of altering coarse transport regimes and the relationship with river morphodynamics using data collected by a tracer based monitoring program carried out in a 4 km long study sector of the parma river italy located downstream from a relatively recently established dam we applied a virtual velocity approach to estimate the coarse bed material load at four river cross sections monitoring and calculation results provided new insights into the impacts of the dam on streambed material mobility and the sediment regime over the 17 month calculation period a longitudinal gradient of effects was observed along the study sector sections located closer to the dam are characterized by more evident impacts due to deficits in coarse sediment input from upstream sediment mobility here is strongly altered especially in the highly armored main channel and the overall bed material load is extremely low a partial recovery of sediment dynamics was observed at the sections located further from the dam where estimates indicate higher sediment yield the observed longitudinal trend in the coarse sediment transport regime matches the morphology as the river shifts downstream from a sinuous configuration with alternate bars to a wandering one the novel insights into alteration of coarse sediment dynamics and the relationship with river morphodynamics are potentially applicable to many other fluvial contexts affected by similar impoundments

geochemistry and isotope chemistry of michigan basin brines devonian formations detailed chemical and isotope analysis of 87 formation waters collected from six devonian aged units in the michigan basin are presented and discussed in terms of the origin of the dissolved components and the water total dissolved solids in these waters range from 200 000 to 400 000mg 1 upper devonian formations produce dominantly nacacl brine while deeper formations produce canacl water ratios of cl br and na br along with divalent cation content mcl2 indicate that these brines are derived from evapo concentrated seawater other ion concentrations appear to be extensively modified from seawater values by water rock reactions the most important reactions are dolomitization which explains the ca content of the brines and reactions involving aluminosilicate minerals stable isotope 18o and d compositions indicate that water molecules in the deeper formations are derived from primary concentrated seawater isotope enrichment by exchange with carbonates and perhaps gypsum cannot be discounted isotope values indicate water in the upper devonian formations is a mixture of seawater brine diluted with meteoric derived water dilution has predominantly occurred in basin margins two scenarios are presented for the origin of the brines in the devonian formations 1 they originated when the devonian sediments and evaporites were first deposited or 2 they are residual brine liberated from the deeper devonian and possibly silurian salt deposits

influence of hydrogeology microbiology and landscape history on the geochemistry of acid hypersaline waters n w victoria abstract there is now evidence that naturally occurring acid water is more abundant than previously thought and that it has been important in the geologic past understanding the processes leading to the formation of such systems is required to appreciate the role of acid systems in geologic processes and to develop indicators for recognizing the geologic environmental importance of these systems in the past this paper characterizes the hydrogeology hydrogeochemistry microbial biogeochemistry and landscape attributes of acid groundwater surface water systems in australia with an emphasis on a well studied playa lake system lake tyrrell murray valley a model for the origin of these acid brines is presented and the importance of acid brine producing systems is speculated upon data include porewater and groundwater geochemical measurements collected during a 10 day field campaign and results from geochemical modeling and graphics e g piper diagrams and x y plots of seawater evaporation trajectories key characteristics of the system are 1 aquifer materials have low acid buffering capacities 2 saline groundwater flowing onto playa surfaces is an oxic h2so4 solution 3 authigenic minerals include combinations of jarosite kfe3 so4 2 oh 6 alunite kal3 so4 2 oh 6 and fe oxides that can form as evaporite minerals 4 a source for solutes can be marine aerosols and 5 the formation of ironstones groundwater acidification by various processes including sulfide oxidation and ferrolysis and at many different times are the unique aspects for evolution of these acid brines and they can be considered another end member of the eugster jones hardie model for the evolution of brines in closed basins acid hypersaline groundwater and playa systems such as lake tyrrell may be an example of expected changes in the hydrogeochemistry of terrestrial water during late stage continental denudation under arid conditions historically these systems may have been integral to the formation of opal bauxite some low temperature ore deposits of authigenic k feldspars and continental redbeds natural acid saline systems such as those in australia may also be representative of acid saline systems on mars

bedload entrainment travel lengths step lengths rest periods studied with passive iron magnetic and active radio tracer techniques this paper reports results from bedload transport investigations with active radio and passive iron magnetic tracers in the lainbach a step pool mountain river in bavaria southern germany the spatial distributions of the iron tracers after flood events can be best described by exponential or gamma distributions there is some indication of a tendency of size selective transport of the iron tracers but there is also a considerable amount of scatter in the correlations between weight size and travel length owing to the masking influence of other variables such as the shape of the particles and different positions in the river bed the experiments with artificial magnetic tracers showed that elongated pebbles rods had the longest mean transport distance platy ones discs remained relatively close to the starting points the particles from the pool showed the greatest transport lengths and a 100 per cent chance of being eroded the pebble transmitter system petsy consists of transmitters implanted into individual pebbles a computerized receiver a stationary antenna system with an antenna switchboard and a data logging system the particles do not move continuously but in a series of transport steps and non movement intervals a single value for a given size class is not adequate to describe the critical conditions of entrainment under natural circumstances a probability approach is much more suitable the critical unit discharges total discharge divided by active channel width along the measuring reach are dependent on river bed morphology in the steps bedload needs higher unit discharges to be entrained once entrained the transport of bedload is stochastic in nature and the single particle transport is controlled by the step lengths and the duration of rest periods the distributions of both parameters can be approximated by exponential functions applying the stochastic concept proposed by einstein the mean values of the random variables step length and duration of rest period measured with the petsy technique were used for the simulation of spatial distributions of bedload particles from point sources more field and laboratory data are needed to include varying flow and roughness conditions with tracers representing different particle characteristics

radio tracking gravel particles in a large braided river in new zealand a field test of the stochastic theory of bed load transport proposed by einstein hans a einstein initiated a probabilistic approach to modelling sediment transport in rivers his formulae were based on theory and were stimulated by laboratory investigations the theory assumes that bed load movement occurs in individual steps of rolling sliding or saltation and rest periods so far very few attempts have been made to measure stochastic elements in nature for the first time this paper presents results of radio tracing the travel path of individual particles in a large braided gravel bed river the waimakariri river of new zealand as proposed by einstein it was found that rest periods can be modelled by an exponential distribution but particle step lengths are better represented by a gamma distribution einstein assumed an average travel distance of 100 grain diameters for any bed load particle between consecutive points of deposition but larger values of 6 7 m or 150 grain diameters and 6 1 m or 120 grain diameters were measured for two test particle sizes together with other available large scale field data a dependence of the mean step length on particle diameter relative to the d50 of the bed surface was found during small floods the time used for movement represents only 2 7 of the total time from erosion to deposition the increase in percentage of time being used for transport means that it then has to be regarded in stochastic transport models tracing the flow path of bed load particles between erosion and deposition sites is a step towards explaining the interactions between sediment transport and river morphology copyright 2001 john wiley sons ltd

bipolar changes in atmospheric circulation during the little ice age annually dated ice cores from siple dome west antarctica and central greenland indicate that meridional atmospheric circulation intensity increased in the polar south pacific and north atlantic at the beginning 1400 a d of the most recent holocene rapid climate change event the little ice age lia as deduced from chemical concentrations at these core sites the lia was characterized by substantial meridional circulation strength variability and this variability persists today despite strong evidence for an end to lia cooling thus increased late 20th century storm variability may be in part a result of the continuation of these climatic fluctuations

silicic acid leakage from the southern ocean a possible explanation for glacial atmospheric pco2 1 using a simple box model we investigate the effects of a reduced si n uptake ratio by antarctic phytoplankton on the marine silica cycle and atmospheric pco2 recent incubation experiments demonstrate such a phenomenon in diatoms when iron is added hutchins and bruland 1998 takeda 1998 franck et al 2000 the southern ocean may have supported diatoms with reduced si n uptake ratios compared to today during the dustier glacial times petit et al 1999 a similar reduction in the uptake ratio may be realized with an increased production of nondiatom phytoplankton such as phaeocystis our model shows that reduced si n export ratios in the southern ocean create excess silicic acid which may then be leaked out to lower latitudes any significant consumption of the excess silicic acid by diatoms that leads to an enhancement in their growth at the expense of coccolithophorids diminishes caco3 production and therefore diminishes the carbonate pump in our box model the combination of a reduced carbonate pump and an open system carbonate compensation draw down steady state atmospheric co2 from the interglacial 277 to 230 242 ppm depending on where the excess silicic acid is consumed by comparison the atmospheric pco2 sensitivity of general circulation models to carbonate pump forcing is 3 5 fold greater which combined with carbonate compensation can account for peak glacial atmospheric pco2 we discuss the importance of the initial rain ratio of caco3 to organic carbon on atmospheric pco2 and relevant sedimentary records that support and constrain this silicic acid leakage scenario

experiments on dispersion of tracer stones under lower regime plane bed equilibrium bed load transport 1 a common approach for estimating the bed load transport rate in gravel bed streams is to relate it to deterministic channel averaged driving parameters and corresponding resistance properties of the bed material notwithstanding the proven success of this approach in modeling various morphodynamic scenarios it does not contain the mechanics necessary to relate the bulk sediment transport rate to the displacement patterns of individual particles experiments on entrainment transport and deposition of tracer stones in a flume described here were designed to address this issue predictors of statistics of bed elevation fluctuations at short timescales total and elevation specific particle entrainment rates particle step lengths mean and associated probability density function for particle virtual velocity and thickness of the active layer were developed the working hypothesis tested in this paper is that the statistics of tracer displacements can be related to channel averaged hydraulic parameters and thus linked to macroscopic aspects of bed load transport

glacial interglacial variations in methanesulfonate msa in the siple dome ice core west antarctica methanesulfonate msa in the siple dome ice core is a record of the deposition of biogenic sulfur to the west antarctic ice sheet covering the past 100 kyr siple dome msa levels were low during the last glacial maximum and increased to higher holocene levels with a several kyr lag relative to the deglacial warming the positive correlation between msa and temperature at siple dome is similar to that in greenland ice cores renland gisp2 and grip and stands in contrast to the negative correlation observed at vostok east antarctica the siple dome msa data suggest that the sign of the high latitude dust sulfur climate feedback is negative at least for the pacific sector of the high latitude southern ocean these results challenge the idea that fertilization by increased dust deposition led to widespread increased dms emissions from this region of the glacial southern ocean

tracing river gravels insights into dispersion from a long term field experiment abstract sediment dispersion is a fundamental component of the sediment transfer process in gravel bed rivers modeling this process requires an understanding of the collective movement of mixed size clasts this study explores the temporal evolution of gravel dispersion to underscore the importance of field observation in informing modeling efforts magnetically tagged gravels deployed in carnation creek have been monitored repeatedly over 17 years four metrics used to describe the extent of dispersion document that the overall shape in the spatial distribution of grain location changes over time the general trends mask the complexity of the dispersion process expressed by channel sections where tracers are concentrated regardless of grain size the distribution of total grain displacement responsible for dispersion evolves as tracers become well mixed results demonstrate that observations from the field are crucial to the understanding and modeling of sediment dispersion because they provide key insights into the dispersion process that must be known a priori for mathematical modeling and similar observations cannot be collected using laboratory flumes

hydrogeochemistry and weathering on the yilgarn block western australia ferrolysis and heavy metals in continental brines abstract groundwater samples collected from salt lakes over the archean yilgarn block of western australia show the influence of climate on geochemical weathering patterns major element compositions in salt lake groundwaters show little systematic trend but there are marked differences in ph and fe cu and pb concentrations in the alkaline carbonated systems of the arid northeastern part compared to concentrations of the same elements in groundwater systems of the mediterranean type climatic region of the wheatbelt in the southwestern part of the block in this latter region in addition to higher rainfall input the groundwater systems have steeper hydraulic gradients weathering bedrock is closer to the surface and oxidation and hydrolysis of iron ferrolysis is evident in weathering profiles a combination of vertical diffusion and horizontal groundwater flow is thought to be responsible for the development of ferrolysis and acidity in groundwaters in this region anomalously high concentrations of heavy metals particularly lead are observed in some of the acid saline groundwaters the formation of laterite which is a ubiquitous feature of the yilgam block landscape is a process probably closely linked to ferrolysis

observations on sediment mobility in a large gravel bed river article this study investigates sediment mobility in a large gravel bed river tagliamento river northeastern italy field data were used to identify the morphological effectiveness of a range of flows floods with recurrence interval b1 to 3 5 year and for a detailed analysis of the partial transport condition the analyses were carried out on three cross sections where a number of areas representative of different morphological units main and secondary channels low and high bars islands were painted grain size of the painted area was measured using a photographic method monitoring of bed mobility during the study period supplied new photographs of the painted areas measurements of size and travel distance of the mobilized particles and estimate of flow depth after each flood event our analyses have shown that with dimensionless shear stress around 0 073 17 n m 2 the morphological effect over the painted areas was primarily partial transport while with stresses n0 1 25 n m 2 the bed experienced full mobility i e all the painted particles were transported or totally buried full sediment mobility was observed on lower morphological units i e main and secondary channels under floods with very high frequency rib1 y whereas on the low bars full mobility occurred under floods with a recurrence interval slightly n1 year instead fine deposition and partial transport conditions were observed on the higher bars even after the largest of the monitored floods ri 3 5 y the analysis of the partial transport condition relies on more than 3500 measurements of particle travel distance travel distances range from a few centimetres up to 22 m the transported particles were generally finer than the painted sediments and the analysis of the sediment transport ratio revealed that partial transport occurred under equal mobility conditions for particles finer than 32 mm and under size selective mobility for coarser fractions this appears to be corroborated for db32 mm by the insensitiveness of particle transport distance to particle sizes even if the exponent 1 of the relationship between the dimensionless shear stress and the maximum transported diameter would suggest that all fractions are transported under equal mobility conditions

geomorphological control on boulder transport and coastal erosion before during and after an extreme extra tropical cyclone extreme wave events in coastal zones are principal drivers of geomorphic change evidence of boulder entrainment and erosional impact during storms is increasing however there is currently poor time coupling between pre and post storm measurements of coastal boulder deposits importantly there are no data reporting shore platform erosion boulder entrainment and or boulder transport during storm events rock coast dynamics during storm events are currently unexplored here we use high resolution daily field data to measure and characterize coastal boulder transport before during and after the extreme northeast atlantic extra tropical cyclone johanna in march 2008 forty eight limestone fine medium boulders n 46 and coarse cobbles n 2 were tracked daily over a 0 1 km2 intertidal area during this multi day storm boulders were repeatedly entrained transported and deposited and in some cases broken down n 1 or quarried n 3 during the most intense days of the storm eighty one percent n 39 of boulders were located at both the start and end of the storm of these 92 were entrained where entrainment patterns were closely aligned to wave parameters these data firmly demonstrate rock coasts are dynamic and vulnerable under storm conditions no statistically significant relationship was found between boulder size mass and net transport distance graphical analyses suggest that boulder size limits the maximum longshore transport distance but that for the majority of boulders lying under this threshold other factors influence transport distance paired analysis of 20 similar sized and shaped boulders in different morphogenic zones demonstrates that geomorphological control affects entrainment and transport distance where net transport distances were up to 39 times less where geomorphological control was greatest these results have important implications for understanding and for accurately measuring and modelling boulder entrainment and transport coastal managers require these data for assessing erosion risk 2016 the authors earth surface processes and landforms published by john wiley sons ltd

channel reach morphology in mountain drainage basins a classification of channel reach morphology in mountain drainage basins synthesizes stream morphologies into seven distinct reach types colluvial bedrock and five alluvial channel types cascade step pool plane bed pool rime and dune ripple coupling reach level channel processes with the spatial arrangement of reach morphologies their links to hillslope processes and external forcing by confinement ripar ian vegetation and woody debris defines a process based framework within which to assess channel condition and response potential in mountain drainage basins field investigations demonstrate character istic slope grain size shear stress and roughness ranges for different reach types observations consistent with our hypothesis that alluvial channel morphologies reflect specific roughness configurations ad justed to the relative magnitudes of sediment supply and transport ca pacity steep alluvial channels cascade and step pool have high ratios of transport capacity to sediment supply and are resilient to changes in discharge and sediment supply whereas low gradient alluvial channels pool rime and dune ripple have lower transport capacity to supply ra tios and thus exhibit significant and prolonged response to changes in sediment supply and discharge general differences in the ratio of transport capacity to supply between channel types allow aggregation of reaches into source transport and response segments the spatial distribution of which provides a watershed level conceptual model linking reach morphology and channel processes these two scales of channel network classification define a framework within which to in vestigate spatial and temporal patterns of channel response in moun tain drainage basins

virtual rate and mean distance of travel of individual clasts in gravel bed channels travel distances in gravel bed rivers of tagged particles of various sizes are related to excess stream power estimated for peak discharge mean distance of movement irrespective of grain size is weakly correlated with stream power especially near the threshold of movement there may be several reasons for the weak correlation including variable effects of bed structure varying magnitudes of sediment mobilizing events and sampling problems grain size itself is of marginal significance the virtual rate of travel calculated using total time for which the flow is larger than that needed to initiate clast movement also bears a weak relation to the excess stream power over the period better results are obtained by relating the virtual rate of travel to the first peak of the flow event only this implies that the initial seeding of the tagged particles dominates the observations nonetheless an underlying general relation is indicated by the data which are derived from a wide range of flow regime types

spatial variability and hydrologic evolution of australian lake basins analogue for pleistocene hydrologic change and evaporite formation abstract processes evident in basins across hydrologic gradients from humid to arid regions today provide analogues for systems that may have operated in some individual basins during periods of past hydrologic change thus lakes in humid regions today with low salinity sedimentary facies and with morphology controlled largely by wave action may closely resemble past lacustral pluvial phases experienced in zones which today are relatively arid and saline conversely playas controlled today by groundwater and in some cases subject to defletion may resemble those arid and dune building stages experienced by basins in sub humid regions today as they underwent glacial age desiccation in any such sequence of spatial or temporal gradients from humid to more arid conditions the frequency of basin filling and drying modulates the rate of evaporitive loss of interstitial waters from the exposed basin surface this in turn controls the salinity evolution of the interstitial and local groundwaters the notion of closed systems for terminal lakes while satisfactory for analysis of surface water budgets is quite inapplicable to the evolution of brines where surfacewater groundwater exchange during the high salinity drying stages becomes a controlling factor affecting all salt budgets in these systems evaporites may only be preserved when the sub surface waters have evolved to salinites near saturation for the salts concerned if sub surface waters are frequently diluted by surfacewater groundwater exchange evaporites will not be preserved in the record even though the surface system appears hydrologically closed the process of interstitial water evolution which controls efflorescence deflation and salt weathering exerts a dominating influence on basin geomorphic expression as well as on hydrochemical fractionation

the antarctic ice sheet during the last glacial maximum and its subsequent retreat history a review abstract an emerging body of evidence from studies of the last glacial interglacial cycle suggests that the east and west antarctic ice sheets have not advanced and retreated in concert the west antarctic ice sheet advanced to the outer shelf in most regions during the last glacial maximum lgm the retreat from the shelf commenced shortly after the lgm and continued into the late holocene the west antarctic ice sheet in ross and amundsen seas slid across a deforming bed at least during the final phases of extended glaciation this implies that at this time the ice sheet had a low profile differences in the number and locations of grounding zone wedges and smaller grounding zone features from trough to trough imply that individual west antarctic ice sheet ice streams retreated episodically details concerning the expansion retreat and behavior of the east antarctic ice sheet eais are more sparse the picture emerging is that the eais did not expand to the continental shelf edge during the lgm rather it achieved a maximum extent of a mid shelf position in some locations while in other areas the ice terminus was situated near its present location the timing of retreat along sectors within the eais appears diachronous and in places occurred prior to the lgm the antarctic peninsula shelf contained considerably more ice during the lgm than previously proposed the results presented in this paper support more recent published ice sheet models that call for greater contributions of melting ice from west antarctica including the antarctic peninsula to the post glacial rise in sea level

methanesulfonate in the greenland ice sheet project 2 ice core in this paper we present measurements of methanesulfonate in the greenland ice sheet project 2 gisp2 ice core methanesulfonate is an atmospheric oxidation product of dimethylsulfide the gisp2 methanesulfonate record contains information about the atmospheric loading of biogenic sulfur over the past 110 kyr and its relationship to climate change the gisp2 data set supports the inferences made from the renland ice core from greenland that the glacial atmosphere over greenland had reduced concentrations of biogenic sulfur compared with the present day hansson and saltzman 1993 we conclude that the flux of biogenic sulfur from the north atlantic ocean must have been lower during glacial times and speculate that this decrease may have been related to differences in phytoplankton speciation the data suggest that changes in direct radiative forcing from biogenic sulfur aerosols would act as negative feedback to the glacial interglacial climate cycles in this region

observations on the movement of coarse gravel using implanted motion sensing radio transmitters motion sensing radio transmitters were implanted in cobbles 72 92 mm diameter and placed in a stream in south west idaho for 43 days during a snowmelt period the radios transmit different pulse rates depending on whether the rocks are at rest or in motion every 30 s a datalogger samples the receiver and records the pulse rate of the transmitters such information can be used to assess numerous properties of particle transport that are beyond the capabilities of conventional tracking methods conclusions include i rocks are more likely to move on rising hydrograph limbs than on falling hydrograph limbs ii the average shields parameter is 0 046 iii rocks move only a fraction of the time between initial and final motion during an event iv the distributions of motion and rest periods are best modeled by gamma functions rather than exponential but the distributions approach exponential as the tails are trimmed copyright 2004 john wiley sons ltd

characteristics of water soluble inorganic and organic ions in aerosols over the southern ocean and coastal east antarctica during austral summer 1 to characterize the concentrations and size distributions of water soluble organic and inorganic aerosol species including na non sea salt sulfate nss so42 methane sulfonate msa oxalate and succinate over the southern ocean so and coastal east antarctica cea bulk and size segregated aerosols were collected from 40 s 100 e to 69 s 76 e and between 69 s 76 e and 66 s 110 e during a cruise from november 2010 to march 2011 results show that sea salt was the major component of the total aerosol mass accounting for 72 over the so and 56 over cea the average concentrations of nss so42 varied from 420 ng m 3 over the so to 480 ng m 3 over cea the concentrations of msa ranged from 63 to 87 ng m 3 over the so and from 46 to 170 ng m 3 in cea the average concentrations of oxalate were 3 8 ng m 3 over the so and 2 2 ng m 3 over cea the concentrations of formate acetate and succinate were lower than those of oxalate a bimodal size distribution of aerosol mass existed over cea peaking at 0 32 0 56 m and 3 2 5 6 m msa was accumulated in particles of 0 32 0 56 m over cea high chloride depletion was associated with fine mode particles enriched with nss so42 msa and oxalate higher cation to anion and nh4 nss so42 ratios in aerosols over cea compared to that over the so imply the higher neutralization capacity of the marine atmosphere over cea

ice core evidence for antarctic sea ice decline since the 1950s the instrumental record of antarctic sea ice in recent decades does not reveal a clear signature of warming despite observational evidence from coastal antarctica here we report a significant correlation p

entrainment displacement and transport of tracer gravels the mass and size distribution of grain entrainment per unit bed area may be measured by replacing a volume of the bed with tracer gravels and observing the mass difference before and after a transport event this measure of spatial entrainment is relevant to any process involving size selective exchange of sediment between transport and bed and may be directly used in calculations of sediment transport rate using an elementary relation for fractional transport components presented here this relation provides a basis for evaluating tracer data collected by different methods and may be used to provide physical insight regarding the expected behaviour of tracer grains the variation with grain size of total displacement length l ti depends on the degree of mobilization of the individual fractions on the bed surface l ti is independent of d i for smaller fully mobile sizes and decreases rapidly with d i for larger fractions in a state of partial transport in which a portion of the surface grains remain immobile through the flow event the boundary between fully and partially mobile grain sizes increases with flow strength these inferences are supported by values of l ti calculated from flume experiments and provide a physical explanation for a summary relation between l ti and d i based on field data 1997 john wiley sons ltd

hydrological processes in the tyrrell basin southeastern australia abstract the tyrrell basin in semi arid southeastern australia provides an ideal setting where saline acid groundwaters evaporites redbeds syngenetic sulphides and thick groundwater brine bodies are all present and in many instances are actively forming today the relatively flat landscape and the associated regional groundwater systems with their concomitantly low hydraulic gradients create a setting in which is developed a clearer than normal aerial separation of a wide range of complex interwoven physico chemical processes detailed work in the tyrrell basin over a number of years has enabled the establishment of a hydrogeological framework which forms the basis for unravelling otherwise complicated hydrochemical interactions between groundwater systems and salt lakes indeed the interactions between groundwater flow systems and the regional groundwater discharge landscape in general and the spring zones of salt lakes in particular have important implications bearing upon the solution migration deposition and concentration of salts and metals by regional groundwater systems in arid and semi arid areas

controls on δ 34 s and δ 18 o of dissolved sulfate in aquifers of the murray basin australia and their use as indicators of flow processes the usefulness of stable isotopes of dissolved so4 34s and 18o to study recharge processes and to identify areas of significant inter aquifer mixing was evaluated in a large semi arid groundwater basin in south eastern australia the murray basin the distinct isotopic signatures in the oxidizing unconfined murray group aquifer and the deeper reducing renmark group confined aquifer may be more sensitive than conventional chemical tracers in establishing aquifer connections 34s values in the unconfined murray group aquifer in the south and central part of the study area decrease along the hydraulic gradient from 20 8 to 0 3 the concomitant increasing so4 cl ratios as well as relatively low 18oso4 values suggest that vertical input of biogenically derived so4 via diffuse recharge is the predominant source of dissolved so4 to the aquifer further along the hydraulic gradient towards the discharge area near the river murray 34s values in the unconfined murray group aquifer increase and so4 cl ratios decrease due to upward leakage of waters from the confined renmark group aquifer which has a distinctly low so4 cl and high 34s 14 9 56 4 relatively positive 34s and 18oso4 values and low so4 cl in the renmark group aquifer is typical of so4 removal by bacterial reduction the s isotope fractionation between so4 and hs of 24 estimated for the confined aquifer is similar to the experimentally determined chemical fractionation factor for the reduction process but much lower than the equilibrium fractionation 70 even though the confined groundwater residence time is 300 ka years mapping the spatial distribution of 34s and so4 cl of the unconfined murray group aquifer provides an indicative tool for identifying the approximate extent of mixing however the poorly defined end member isotopic signatures precludes quantitative estimates of mixing fractions

mechanisms of iron photoreduction in a metal rich acidic stream st kevin gulch colorado u s a abstract iron photoreduction in metal rich acidic streams affected by mine drainage accounts for some of the variability in metal chemistry of such streams producing diel variations in fe ii differentiation of the mechanisms of the fe photoreduction reaction by a series of in stream experiments at st kevin gulch colorado indicates that a homogeneous solution phase reaction can occur in the absence of suspended particulate fe and bacteria and the rate of reaction is increased by the presence of fe colloids in the stream water in stream fe photoreduction is limited during the diel cycle by the available fe iii in the water column and streambed the quantum yield of fe ii was reproducible in diel measurements the quantum yield in mol e 1 from 300 to 400 nm was 1 4 10 3 in 1986 0 8 10 3 in 1988 and 1 2 10 3 in 1989 at the same location and under similar streamflow and stream chemistry conditions in a photolysis control experiment there was no detectable production of fe ii above background concentrations in stream water samples that were experimentally excluded from sunlight

sorption of trace metals to an aluminum precipitate in a stream receiving acid rock drainage snake river summit county colorado the quality of water in streams that are contaminated by acid drainage from mines and from the weathering of mineralized rocks improves as the water flows downstream the purpose of this study was to investigate the geochemical processes that occur in one such stream and to determine the fate of the trace metals that are removed from the water the stream chosen for this purpose was the snake river summit county colorado which is affected by natural acid rock drainage ard containing so4 al fe and various trace elements such as zn cu pb ni and others most of the fe in the snake river is removed from solution by the oxidation of fe2 to fe3 and the subsequent precipitation of fe oxyhydroxides that form a massive ferricrete deposit near the springs that feed the river further downstream the snake river ph 3 0 mixes with water from deer creek ph 7 0 thereby increasing its ph to 6 3 and causing so4 rich precipitates of al oxyhydroxide to form the precipitates and associated organic c complexes sorb trace metals from the water and thus have high concentrations of certain elements including zn 540 11 400 ppm cu 34 221 ppm pb 90 340 ppm and ni 11 197 ppm the concentrations of these elements in the precipitates that coat the streambed rise steeply in the zone of mixing and then decline downstream the trace element concentrations of the water in the mixing zone at the confluence with deer creek decrease by 75 or more and are up to 3 orders of magnitude lower than those of the precipitates sorption curves for zn cu pb ni and so4 were derived by stepwise neutralization of a sample of snake river water collected above the confluence with deer creek and indicate that the trace metals are sorbed preferentially with increasing ph in the general order pb cu zn and ni sulfate is removed between ph 4 and 5 to form an al hydroxysulfate and or by sorption to microcrystalline gibbsite the sorption data determined from the neutralization experiment were used to account for the downstream decrease of trace metal concentrations in the precipitates the results of this study demonstrate that the partitioning of trace metals in the snake river is not only a function of ph but also depends on the progressive removal of trace metals as the water of the snake river flows through its confluence with deer creek the chemical composition of the water also determines what compounds precipitate with increasing ph

dating the siple dome antarctica ice core by manual and computer interpretation of annual layering the holocene portion of the siple dome antarctica ice core was dated by interpreting the electrical visual and chemical properties of the core the data were interpreted manuallyandwith acomputeralgorithm the algorithm interpretation was adjusted to be consistent with atmospheric methane stratigraphic ties to the gisp2 greenland ice sheet project 2 ice core 10 be stratigraphic ties to the dendrochronology 14 c recordandthedatedvolcanic stratigraphy thealgorithm interpretation ismorecon sistent andbetter quantifiedthanthe tedious and subjective manual interpretation

extremely acid permian lakes and ground waters in north america evaporites hosted by red beds red shales and sandstones some 275 265 million years old extend over a large area of the north american mid continent1 they were deposited in non marine saline lakes pans and mud flats2 settings that are typically assumed to have been alkaline here we use laser raman microprobe analyses of fluid inclusions trapped in halites from these permian deposits to argue for the existence of highly acidic ph 1 lakes and ground waters these extremely acidic systems may have extended over an area of 200 000 km2 modern analogues of such systems may be natural acid lake and groundwater systems ph 2 4 in southern australia3 4 5 6 7 8 9 both the ancient and modern acid systems are characterized by closed drainage arid climate low acid neutralizing capacity and the oxidation of minerals such as pyrite to generate acidity the discovery of widespread ancient acid lake and groundwater systems demands a re evaluation of reconstructions of surface conditions of the past and further investigations of the geochemistry and ecology of acid systems in general

a switch from si oh 4 to no 3 depletion in the glacial southern ocean 1 phytoplankton in the antarctic deplete silicic acid si oh 4 to a far greater extent than they do nitrate no3 this pattern can be reversed by the addition of iron which dramatically lowers diatom si oh 4 no3 uptake ratios higher iron supply during glacial times would thus drive the antarctic towards no3 depletion with excess si oh 4 remaining in surface waters new 30si and 15n records from antarctic sediments confirm diminished si oh 4 use and enhanced no3 depletion during the last three glaciations the present low si oh 4 water is transported northward to at least the subtropics we postulate that the glacial high si oh 4 water similarly may have been transported to the subtropics and beyond this input of si oh 4 may have caused diatoms to displace coccolithophores at low latitudes weakening the carbonate pump and increasing the depth of organic matter remineralization these effects may have lowered glacial atmospheric pco2 by as much as 60 ppm

pliocene sedimentation in a shallow cool water estuarine gulf murray basin south australia the pliocene norwest bend formation is a well preserved succession of terrestrial and shallow marine deposits in the murray basin south australia sediments in this unit consist of two discrete terrigenous clastic rich decametre scale sequences or informal members which record episodes of marine incursion during the early and late pliocene respectively the base of each sequence is a transgressive lag and or strandline deposit that is transitional upwards into a highstand subtidal terrigenous clastic and cool water carbonate sediment accumulation the top of each sequence is incised by fluvial channels that are filled by river deposits which formed as relative sea level fell and terrestrial environments prograded basinward sedimentological data suggest that gross stratigraphic architecture was primarily determined by glacioeustasy differences in sedimentary style between these two sequences however reflect a major climatic change that took place in southern australia during the mid pliocene the lower quartzose sand member is formed of siliciclastic sediment derived from prolonged deep subaerial weathering and contains a bivalve dominated cool temperate open marine mollusc assemblage these sediments accumulated under an equitable relatively warm humid climate the murray basin during this time because of high fluvial discharge was a salt wedge estuary with typical estuarine circulation in contrast the upper oyster rich member is typified by large monospecific oyster buildups that grew in restricted coastal environments strandline deposits contain a warm temperate skeletal assemblage contemporaneous aeolian sediments accumulated under warm semi arid climatic conditions well developed ferricrete silcrete and calcrete horizons reflect cyclic conditions of rainwater infiltration and evaporation in the seasonally dry climate that typifies southern australia today highly seasonal rainfall produced an estuary that fluctuated annually from being well to partially mixed these pliocene sediments support the notion that mollusc rich facies are the signature of cool water carbonate accumulations in inboard neritic environments unlike bryozoans that dominate the outer parts of cenozoic cool water carbonate shelves molluscs evolved to exploit an array of coastal ecosystems with wide salinity variations and variable sedimentation rates

stratiform copper deposits hosted by low energy sediments ii nature of source rocks and composition of metal transporting water several factors suggest that hematite bearing sediments composed principally of alluvial fan sediments were the source of metal transporting water and of metals in stratiform copper deposits hosted by low energy sediments first such sediments are associated with all examples of larger stratiform copper deposits hosted by low energy sediments second a zonal sequence corresponding to an approximate sulfide solubility product increase is developed laterally into the basin from sandy sediments in contact with the hematite bearing sediments and upward from the contact of the ore hosting sediments with the hematite bearing sediments third the zonal sequence is developed basinward from pinchouts and wedge downs of the hematite bearing sediments and copper mineralization is absent from host horizons where hematite bearing sediments are not developed fourth authigenic mineral assemblages with the exception of hematite sulfides and organic carbon are similar in both the host sediments and in the hematite bearing sediments the authigenic and evaporite mineral assemblages and the nature of associated sediments indicate that most occurrences of the hematite bearing sediments were probably deposited in closed continental basins published sedimentological and paleogeographic analyses show that the rotliegende associated with the kupferschiefer hosted deposits was deposited in a closed continental basin no consistent composition of the hematite bearing sediments is evident although basalt flows or basalt derived clastic components occur in the alluvial fan sediments associated with three of the larger stratiform copper deposits authigenic and evaporite minerals and compositions of modern continental closed basin waters show that the waters originally within the closed basins were na cl so 4 types with variable mg ca and so 4 contents in equilibrium with hematite and with a ph constrained either by carbonate minerals atmospheric carbon dioxide or by quartz microcline muscovite chloride concentrations were likely to have been about six times seawater waters with higher mg and lower ca contents were likely to be associated with alluvial fan sediments containing basalt or dolomite derived clastic components water rock ratios in the alluvial fan sediments were probably 33 percent or less if the 50 cm hypothesis i e that chalcocite in stratiform copper deposits hosted by low energy sediments was precipitated as a result of bacterial sulfate reduction within 50 cm of the surface of the host sediment is true then metal transporting waters were being released from the hematite bearing sediments very early in their burial history if so the metal transporting water was the original closed basin water with a temperature of less than 50 degrees c

comparison of methods for quantifying active layer dynamics and bedload discharge in armoured gravel bed rivers several methods were employed in the ardennian rivers belgium to determine the depth of the active layer mobilized during floods and to evaluate the bedload discharge associated with these events the use of scour chains has shown that the depth of the active layer is systematically less than the b axis of the average particle size d50 of the elements which compose the surface layer of the riffles this indicates that only a partial transport exists during low magnitude floods the bedload discharge has been evaluated by combining data obtained using the scour chains technique and the distance covered by tracers quantities of sediment transported during frequent floods are relatively low 0 02 t km 2 due to the armour layer which protects the subsurface material these low values are also related to the fact that the distance calculated for mobilized bedload only applies to tracers fitted with pit passive integrated transponder tags diameter 20 mm whereas part of the bedload discharge is composed of sand and fine gravel transported over greater distances than the pebbles the break up of the armour layer was observed only once for a decennial discharge during this event the bedload discharge increased considerably 2 t km 2 the use of sediment traps data from dredging and a helley smith sampler confirm the low bedload transport in ardennian rivers in comparison to the bedload transport in other geomorphological contexts this difference is explained by the presence of an armoured layer but also by the imbricated structures of flat bed elements which increase the resistance to the flow finally the use of the old iron industry wastes allowed to quantify the thickness of the bed reworked over the past centuries in the lembree river the river bed contains slag elements up to a depth of about 50 cm indicating that exceptional floods may rework the bed to a considerable depth copyright 2012 john wiley sons ltd

smartrock transport in a mountain stream bedload hysteresis and changing thresholds of motion bedload movement is fundamentally probabilistic our quantitative understanding of gravel transport is particularly limited when flow conditions just exceed thresholds of motion in part because of

groundwater geochemistry and composition of hardpans in southwestern australian regolith the mineralogy and geochemistry of pedogenic and groundwater silcretes and ferricretes and associated groundwater geochemistry were investigated for deeply weathered highly kaolinised lateritic regolith in southwesternaustralia the silcretes and ferricretes form subsurface hardpans and impede movement of the highly saline acidic shallow groundwaters in lower valleys of the subdued ancient landscape these valleys are associated with the discharge of groundwater and the formation of saline seeps which host a variety of secondary minerals including amorphous silica opal ct goethite feooh hematite fe 2 o 3 akaganeite feooh jarosite kfe 3 so 4 2 oh 6 barite baso 4 gypsum caso 4 2h 2 o and halite nacl deep groundwater silcretes are commonly composed of silicified in situ lateritic pallid zone materials and saprolite that have developed from granitic rocks the matrix consists of amorphous silica diffused through a porous kaolin groundmass these materials were initially highly porous but the voids are now mostly occupied by amorphous silica and secondary anatase acid groundwater weathering has resulted in the dissolution of most primary silicates including feldspars and micas which has greatly elevated the concentration of dissolved silicon in groundwater isovolumetric weathering of feldspar initially produced highly porous assemblages of fine grained kaolin and minor halloysite which now contain high concentrations of amorphous silica up to about 50 wt occupying most of the pores alkali feldspars alter to kaolin pseudomorphs that are much more porous than vermicular kaolin pseudomorphs replacing mica minerals consequently these pseudomorphs contain much less amorphous silica geochemical modeling using phreeqc enabled prediction of the saturation state of minerals and indicated the dissolution and precipitation reactions occurring in the regolith groundwater environment acid moderately saline groundwaters were in near equilibrium with respect to amorphous silica while near neutral ph saline groundwaters corresponded to undersaturated conditions for extremely acid groundwaters ph 3 5 phreeqc predicted dissolution of kaolin goethite and hematite which is reflected in the elevated concentrations of iron up to 169 mg l and aluminium up to 389 mg l in the groundwater this study is important for the understanding of how groundwater geochemistry influences the precipitation of cementing minerals that form various hardpans in the southwest australian landscape

tracer pebble movement along a concave river profile virtual velocity in relation to grain size and shear stress over 1400 tracer pebbles 16 256 mm in diameter were tracked for 2 years in six reaches of allt dubhaig scotland a small gravel bed river along which shear stress and bed surface grain size decrease toward a local base level pebble movement was size selective both within and between reaches within reaches the decrease in mean travel distance with increasing grain size is strongest in the coarse tail of the size distribution particle shape has a minor secondary effect a nondimensional grain velocity averaged over the duration of competent flow is used to compare different size classes and reaches over 90 of its variance is explained by relative grain size and reach shields stress the pattern of size selectivity is consistent with single event tracer results elsewhere bedload trap data from our distal reach and the concept of partial mobility it provides a mechanism for strong downstream fining by selective transport and deposition along rivers in which stress declines toward base level the nondimensional prediction equation for grain velocity may be of use in other rivers but requires testing

bedload transport in se asian streams uncertainties and implications for reservoir management article this paper reviews the current state of knowledge regarding bedload transport in se asian streams and presents the results from a case study on bedload transport in a mountain stream in northern thailand together the review and new data help contextualize the paucity of work done in the region in the face of a rapid increase in development and reservoir building throughout se asia data from both the reviewed studies and the case study indicate that bedload transport in many se asian streams e g catchment areas b 100 km 2 i s often much higherthan iscommonly assumed for tropicalstreams i e about 10 of the totalsediment load estimat ed annual bedload proportion was 18 of the total annual sediment load in the 74 km

trouble with diffusion reassessing hillslope erosion laws with a particle based model 1 many geomorphic systems involve a broad distribution of grain motion length scales ranging from a few particle diameters to the length of an entire hillslope or stream studies of analogous physical systems have revealed that such broad motion distributions can have a significant impact on macroscale dynamics and can violate the assumptions behind standard local gradient flux laws here a simple particle based model of sediment transport on a hillslope is used to study the relationship between grain motion statistics and macroscopic landform evolution surface grains are dislodged by random disturbance events with probabilities and distances that depend on local microtopography despite its simplicity the particle model reproduces a surprisingly broad range of slope forms including asymmetric degrading scarps and cinder cone profiles at low slope angles the dynamics are diffusion like with a short range thin tailed hop length distribution a parabolic convex upward equilibrium slope form and a linear relationship between transport rate and gradient as slope angle steepens the characteristic grain motion length scale begins to approach the length of the slope leading to planar equilibrium forms that show a strongly nonlinear correlation between transport rate and gradient these high probability long distance motions violate the locality assumption embedded in many common gradient based geomorphic transport laws the example of a degrading scarp illustrates the potential for grain motion dynamics to vary in space and time as topography evolves this characteristic renders models based on independent stationary statistics inapplicable an accompanying analytical framework based on treating grain motion as a survival process is briefly outlined

the first greenland ice core record of methanesulfonate and sulfate over a full glacial cycle methanesulfonate msa in ice cores has attracted attention as a possible tracer of past oceanic emissions of dimethylsulfide dms after sulfate msa is the second most prevalent aerosol oxidation product of dms but in contrast to sulfate dms oxidation is the only known source of msa the hypothesis by charlson et al 1987 of a climate feedback mechanism with sulfur emissions from marine phytoplankton influencing the cloud albedo adds to the interest in establishing long records of msa and non seasalt sulfate spanning large climatic changes records of msa and non seasalt sulfate covering time periods from a few years to thousands of year have been extracted from antarctic ice cores ivey et al 1986 saigne and legrand 1987 legrand and feniet saigne 1991 mulvaney et al 1992 but only the record from the vostok ice core legrand et al 1991 covers a full glacial cycle the concentrations of msa and non seasalt sulfate in antarctica have been found to increase under glacial conditions here we present the first northern hemisphere record of msa and the first continuous record of non seasalt sulfate both extracted from the renland ice core east greenland the records are extending from the holocene to the eem interglacial 130 000 years b p the contrast to the southern hemisphere records is striking with a decreasing concentration of msa with the advance of glaciation but an increasing concentration of non seasalt sulfate a strong linear relationship is found in the renland ice core between the ratio of msa to non seasalt sulfate and the temperature with higher ratios associated with warmer climatic stages while the opposite relationship to temperature is found in the vostok ice core a more complicated picture is emerging of the use of msa in ice cores as a quantitative tracer which suggests that previous interpretations can have been overly simplistic

dimensionless critical shear stress in gravel bed rivers this paper first compiles critical shear stress values from 26 studies of gravel bed rivers gbrs worldwide the most frequently proposed value of the shields criterion c is 0 045 but three major groups with c values ranging from 0 100 were identified second dimensionless critical shear stresses the shields criterion were evaluated for 14 gbrs 18 sites with watershed areas ranging from 12 to 3000 km2 different approaches were used to identify the initial movement of the bed material painted and pit tag pebbles sediment traps and bedload samplers the shields criterion c was estimated using the total shear stress and the grain shear stress several shear stresses were also estimated using shear velocities for bedload transport we obtained an average shields criterion c of 0 040 the values were higher in small rivers 0 050 than larger rivers 0 030 because of more significant bedform shear stresses the shields criterion c was lower when the grain shear stress was used and only reached 0 019 different values are also proposed in relation to the type of mobilization the c value for partial transport was 0 025 and exceeded 0 040 for full transport usually reached in association with discharges with a 10 year return period the values based on the results of sediment traps and a bedload sampler were greater than those obtained using tracers but these differences are smaller than those usually reported in the literature

evolution of late triassic rift basin evaporites passaic formation newark basin eastern north america the passaic formation of the late triassic newark supergroup is 2700 m thick and was deposited in series of wide deep to shallow lacustrine environments in the newark rift basin eastern north america the passaic formation can be divided into lower middle and upper sections based on depositional structures composition and the distribution and morphology of its evaporites evaporites formed as a result of syndiagenetic cementation and or displacive processes evaporitive minerals now include gypsum and anhydrite although other mineral species such as glauberite may have originally existed most of the evaporites of the passaic formation occur within massive red mudstone and siltstone lithologies in the form of diffuse cements void fillings euhedral crystals crystal clusters and nodules these evaporites grew displacively within the fine siliciclastic matrix as a result of changes in the hydrochemical regimes of the rift basin a well developed upward increase in the amount of evaporite material is present in the passaic formation this resulted from 1 long term progressive increase in aridity and 2 significant increase in evaporation surface area of the basin during its tectonic evolution a nonmarine source for the evaporites is evident from the isotopic data sulphate 34s ranges from 11 to 3 3 cdt while 18o ranges from 15 1 to 20 9 smow indicating derivation from early diagenetic oxidation of organic sulphur and pyrite within the organic rich lacustrine deposits the 87sr 86sr ratios in sulphate are radiogenic average 0 71211 showing the interaction of basin waters with detrital components and that the newark basin was isolated from the world ocean most of the original evaporites show evidence of diagenetic change to polycrystalline and polymineralic pseudomorphs now filled with recrystallized coarse grained anhydrite 1 3 mm size and low temperature albite homogenization temperatures of fluid inclusions within the coarse grained anhydrite indicate crystallization temperatures for anhydrite in the range of 150 to 280 c such elevated temperatures resulted from circulation of hot water in the basin later exhumation of these rocks caused partial to total replacement of anhydrite by gypsum in the upper part of the section the resulting increase in volume due to hydration of anhydrite at shallow depths also emplaced non evaporative satin spar veins fibrous gypsum along bedding planes and in fractures while the local geology of the newark rift basin controlled the distribution of facies the sedimentological development of the passaic formation evaporites resulted from the world wide climatic aridity that prevailed during the late triassic because the newark basin sequence was only covered with about 3 km of sedimentary overburden that correspond to about 100 c and hence suggests that evaporites have experienced alteration by hot fluids 5 as the triassic marks the greatest evaporite formation world wide and profound sense of parched continentality throughout the world existed before the final break up of the pangea the passaic formation evaporites are an example of the influence of these palaeoclimatic conditions at the eastern margin of north america

toward a unified science of the earth s surface opportunities for synthesis among hydrology geomorphology geochemistry and ecology 1 the earth s surface is shaped by the interaction of tectonics water sediment solutes and biota over a wide range of spatial and temporal scales and across diverse environments development of a predictive science of earth surface dynamics integrates many disciplines and approaches including hydrology geomorphology ocean and atmospheric science sedimentary and structural geology geochemistry and ecology this paper discusses challenges opportunities and a few example problems that can serve as pathways toward this integration

measuring gravel transport and dispersion in a mountain river using passive radio tracers random walk models of fluvial sediment transport recognize that grains move intermittently with short duration steps separated by rests that are comparatively long these models are built upon the probability distributions of the step length and the resting time motivated by these models tracer experiments have attempted to measure directly the steps and rests of sediment grains in natural streams this paper describes results from a large tracer experiment designed to test stochastic transport models we used passive integrated transponder pit tags to label 893 coarse gravel clasts and placed them in halfmoon creek a small alpine stream near leadville colorado usa the pit tags allow us to locate and identify tracers without picking them up or digging them out of the streambed they also enable us to find a very high percentage of our rocks 98 after three years and 96 after the fourth year we use the annual tracer displacement to test two stochastic transport models the einstein hubbell sayre ehs model and the yang sayre gamma exponential model gem we find that the gem is a better fit to the observations particularly for slower moving tracers and suggest that the strength of the gem is that the gamma distribution of step lengths approximates a compound poisson distribution published in 2012 this article is a us government work and is in the public domain in the usa

bedload hysteresis in a glacier fed mountain river sediment transport during flood events often reveals hysteretic patterns because flow discharge can peak before counterclockwise hysteresis or after clockwise hysteresis the peak of bedload hysteresis in sediment transport has been used in the literature to infer the degree of sediment availability counterclockwise and clockwise hysteresis have been in fact interpreted as limited and unlimited sediment supply conditions respectively hysteresis has been mainly explored for the case of suspended sediment transport but it was rarely reported for bedload transport in mountain streams this work focuses on the temporal variability of bedload transport in an alpine catchment saldur basin 18 6 km2 italian alps where bedload transport was monitored by means of an acoustic pipe sensor which detects the acoustic vibrations induced by particles hitting a 0 5m long steel pipe runoff dynamics are dominated by snowmelt in late spring early summer mostly by glacier melt in late summer early autumn and by a combination of the snow and glacier melt in mid summer the results indicate that hysteretic patterns during daily discharge fluctuations are predominantly clockwise during the snowmelt period likely due to the ready availability of unpacked sediments within the channel or through bank erosion in the lower part of the basin on the contrary counterclockwise hysteresis tend to be more frequent during late glacier melting period possibly due to the time lag needed for sediment provided by the glacial and peri glacial area to be transported to the monitoring section however intense rainfall events occurring during the glacier melt period generated predominantly clockwise hysteresis thus indicating the activation of different sediment sources these results indicate that runoff generation processes play a crucial role on sediment supply and temporal availability in mountain streams

the regolith in australia abstract australian regolith materials are described many of which are complex much australian regolith dates back to the tertiary mesozoic or earlier there is a progressive change in the nature of alluvium through the tertiary aridity revealed through sand dunes and evaporites is confined to the quaternary ferricretes and silcretes are formed on lower slopes often followed by inversion of relief tectonic isolation of australia as well as climatic change is responsible for the change in the nature of terrestrial sediments since the cretaceous

a stable isotope investigation of groundwater surface water interactions at lake tyrrell victoria australia herczeg a l barnes c j macumber p g and olley j m 1992 a stable isotope investigation of groundwater surface water interactions at lake tyrrell victoria australia in w b lyons d t long a l herczeg and m e hines guesteditors the geochemistry of acid groundwater systems chem geol 96 19 32 the stable isotope composition of regional groundwaters around lake tyrrell victoria indicates that the groundwaters are derived entirely from meteoric water that has undergone some degree of evaporation during recharge seepage waters at the western margin of lake tyrrell victoria have a characteristic chemical and isotopic signature of regional groundwater flowing from the northeast and east on a transect of shallow groundwaters across the lake the isotopic composition is increasingly enriched in the heavy isotopes toward the centre of the lake but define a steeper slope on a dd djso plot than that of the regional groundwaters the stable isotopic compositions of the shallow groundwaters within the seepage zone are typical of those due to evaporative enrichment currently occurring with a small component of vertical mixing with the deeper reflux brines reflux brines below the lake are relatively more enriched in tso than the brines forming now at the lake surface the reflux brines appear to have undergone several cycles of evaporation and admixture of regional groundwater as have waters within the mixing zone between regional groundwater and reflux brines

hydrochemistry on the yilgarn block western australia ferrolysis and mineralisation in acidic brines abstract in the southeastern part of western australia internal drainage and a semi arid climate have resulted in extensive development of playas the brines beneath the playas wedge outwards and force local infiltration to crop out at playa margins as discharge zones the discharging water contains dissolved fe2 oxidation and hydrolysis ferrolysis of which generates very acidic water ph 2 8 at least some of the alkalinity generated by the original reduction of fe3 has been sequestered as subsurface calcrete within local soils the acidity causes the dissolution of kaolinite which is abundant in playa sediments and as a thick capping on weathered bedrock giving water with a low ph and high concentrations of dissolved al and si evaporation and mixing with playa brines containing high concentrations of k and so4 causes alunite to precipitate as ph rises from a minimum of 2 8 at chlorinities of 1 to 2 m to 6 at chlorinities of 4 8 m the alunite deposits formed by this process are many orders of magnitude larger than occurrences elsewhere in the world the large scale mobilisation of si during this process may be one mechanism for the formation of silica cemented rocks silcrete that are widespread in the australian regolith

spatial variations in water composition at a northern canadian lake impacted by mine drainage abstract release of acid drainage from mine waste disposal areas is a problem of international scale contaminated surface water derived from mine wastes orginates both as direct surface runoff and indirectly as subsurface groundwater flow at camp lake a small canadian shield lake that is in northern manitoba and is ice covered 6 months of the year direct and indirect release of drainage from an adjacent sulfide rich tailings impoundment has severely affected the quality of the lake water concentrations of the products from sulfide oxidation are extremely high in the pore waters of the tailings impoundment groundwater and surface water derived from the impoundment discharge into a semi isolated shallow bay in camp lake the incorporation of this aqueous effluent has altered the composition of the lake water which in turn has modified the physical limnology of the lake geochemical profiles of the water column indicate that despite its shallow depth 6 m the bay is stratified throughout the year the greatest accumulation of dissolved metals and so 4 is in the lower portion of the water column with concentrations up to 8500 mg l 1 fe 20 000 mg l 1 so 4 30 mg l 1 zn 100 mg l 1 al and elevated concentrations of cu cd pb and ni meromictic conditions and very high solute concentrations are limited to the bay outside the bay solute concentrations are lower and some stratification of the water column exists identification of locations and composition of groundwater discharge relative to lake bathymetry is a fundamental aspect of understanding chemical evolution and physical stability of mine impacted lakes

the incidence and nature of bedload transport during flood flows in coarse grained alluvial channels a continuous record reveals that the incidence of bedload in a coarse grained river channel changes from flood to flood long periods of inactivity encourage the channel bed to consolidate sufficiently so that bedload is largely confined to the recession limb of the next flood wave but when floods follow each other closely the bed material is comparatively loose and offers less resistance to entrainment in this case substantial amounts of bedload are generated on the rising limb this is confirmed by values of bed shear stress or stream power at the threshold of initial motion which can be up to five times the overall mean in the case of isolated floods or those which are the first of the season this produces a complicated relationship between flow parameters and bedload and explains some of the difficulties in establishing bedload rating curves for coarse grained channels besides this the threshold of initial motion is shown to occur at levels of bed shear stress three times those at the thresholds of final motion this adds further confusion to attempts at developing predictive bedload equations and clearly indicates at least one reason why equations currently in use are unsatisfactory bedload is shown to be characterized by a series of pulses with a mean periodicity of 1 7 hours in the absence of migrating bedforms it is speculated that this well documented pattern reflects the passage of kinematic waves of particles in a slow moving traction carpet the general pattern of bedload including pulsations is shown to occur more or less synchronously at different points across the stream channel