some observations on suspended sediment dynamics in storbregrova jotunheimen observations are reported of the dynamics of suspended sediment transport in the meltstream of storbreen in the jotunheimen fine sediment is transferred from the subglacial to the proglacial environment during low flow meltdominated periods and then removed from the catchment during high flow rainfall controlled events both diurnal and storm period sediment load discharge relationships involve clockwise hysteresis but separate multivariate rating curves define variations of load with streamflow according to 1 the relative importance of meltwater and rainfall runoff and 2 changes in the sediment source areas contributing to the stream at different times particle size variations in the suspended sediment also reflect varying source area influences

minor and trace element export from a glacierized alpine headwater catchment haut glacier d arolla switzerland major ion concentrations in meltwaters draining glacial environments have been widely reported however concentrations of minor and trace elements have received scant attention this study presents trace and minor element variations in bulk meltwaters draining haut glacier d arolla switzerland based on twice daily sampling throughout the 1999 ablation season which represents the most detailed meltwater quality dataset to date in order to assess the mode of export from the catchment these elements are partitioned into i dissolved and ii particulate associated minor and trace element components a computer based speciation model phreeqci was applied to the bulk meltwater data suggesting that ba be cd cu li rb and sr exist primarily as mobile monovalent or divalent dissolved cations which may be involved in interactions with suspended sediment surfaces conversely the model predicts the precipitation of fe al mn and cr oxi hydroxides suggesting these species may be predominantly transported as colloids which may remove other minor and trace elements from solution by co precipitation reactions laboratory leaching experiments on suspended sediments and fresh rock powder suggests that minor and trace element concentrations may also be influenced by oxy hydroxide precipitation and adsorption desorption reactions with suspended sediment surfaces the quantity and transport mode of trace and minor elements may influence their bioavailability downstream of glacierized headwater catchments further the enrichment of many dissolved minor and trace elements in meltwaters compared with world stream waters coupled with the timing of water and sediment delivery during the summer months may have implications for downstream aquatic environments copyright 2001 john wiley sons ltd

the evolution of illite to muscovite an example of the behaviour of isotopes in low grade metamorphic terrains abstract a review of the possibilities and limitations of the use of radiogenic isotopes in low grade terrains i e in the temperature range below the blocking temperature of potassic white mica is discussed using a background of a data base of over 500 isotope analyses on more than 250 illitic muscovitic samples published in various papers special stress is laid on the main problems 1 distinction between detrital and neoformed minerals 2 the slow evolution of minerals without pronounced breaks and 3 retention problems of radiogenic daughter products a brief description of low grade metamorphism is given and criteria enabling a subdivision into low to very low grade metamorphism are discussed comprising illite crystallinity mineralogy fluid inclusions and coal rank measurements the useful type of lithologies for this kind of work ranges from shales slates through volcaniclastic tuffs with high primary glass contents and limestone dolomites marbles to mylonites it can be concluded that carefully selected illitic muscovites yield geologically meaningful ages provided that more than one isotopic method is applied

palaeostress analysis a contribution to the understanding of basin tectonics and geodynamic evolution example of the permian cenozoic tectonics of great britain and geodynamic implications in western europe abstract microtectonic analysis in association with tectonic sedimentological observations enables us not only to define palaeostress tensors but also to date each of them such a study carried out in central and northeastern england and in southernmost wales has permitted us to point out several tectonic stages during the permian cenozoic period 1 inferred from syn sedimentary faulting in the late permian series the permian early triassic tectonic regime is characterised by a nnw sse oriented extension 2 during the late triassic to the early late jurassic an e w to ene wsw oriented extension was acting as suggested by syn sedimentary normal faulting in keuper lias and middle dogger sediments and post sedimentary normal faulting in oxfordian sediments 3 the following tectonic event probably started during the malm and was particularly active during the early cretaceous it was characterised by a n s to nne ssw oriented extension and was associated with an e w to wnw ese oriented strike slip tectonic regime transtension 4 a locally observed nw se oriented transpressional strike slip tectonic regime is thought to correspond to the laramide inversion phase of the middle paleocene 5 the later tectonic event is characterised by a n s oriented transpressional strike slip regime and affects a paleocene tholeiitic dyke cleveland dyke it is supposed to be synchronous with the so called eocene pyrenean to the early miocene helvetic compressional stages these paleostress tensors are compared with others defined in france the benelux countries and germany and are also collated to the tectonic evolution of oil basins assessed from geophysical analyses these comparisons raise discussions about the paleostress distribution within the geodynamic evolution of the west european shelf

the krunkelbach uranium deposit schwarzwald germany correlation of radiometric ages u pb u xe kr k ar 230 th 234 u pitchblendes and secondary uranium minerals from the krunkelbach vein type uranium deposit in southwest germany were investigated by the u xe kr u pb and 234 u 230 th methods and by microprobe analysis both u pb and u xe kr results indicate a late carboniferous formation age of 295 or 7 ma for all veins of the deposit and an episodic pb loss during the tertiary 50 or 8 ma 234 u 230 th dating yields quaternary formation ages of 250 to 350 ka kiloyears for five secondary u minerals u pb isotope investigations on three of these samples show a strong component of inherited radiogenic pb which means that during the quaternary pitchblende oxidation pb was not completely separated from u the three isotopically dated events probably correlate with three generations of fluid inclusions the carboniferous hydrothermal veins were formed from low salinity solutions at temperatures of 100 degrees to 300 degrees c uranium probably was derived from leaching of magmatic uraninite in the brhalde granite by near surface oxidizing ground waters and later precipitated due to mixing with hot strongly reducing solutions or by reaction with a previously deposited reduced ore assemblage a gap of 30 to 40 m g between granite emplacement and pitchblende formation indicates that circulation of hydrothermal fluids in the late carboniferous early permian probably was caused by a high regional heat flow rather than by magmatic heat during the formation of the rhinegraben in the early tertiary barite fluorite and calcite but not ore minerals were deposited from highly saline na ca cl brines of 150 degrees to 200 degrees c these brines leached radiogenic and fissiogenic uranium daughters from the pitchblendes and there are indications of minor uranium remobilization eight illite samples from hydrothermally altered wall rocks yield k ar ages of 119 to 208 ma these values are interpreted as mixing ages of the u pb and u xe kr documented carboniferous and tertiary events although a mesozoic event not recorded in the other isotopic systems cannot be ruled out with certainty in the late tertiary early quaternary the present hydrological conditions were installed with infiltration of oxygen rich meteoric waters causing uranium remobilization and precipitation of secondary uranyl minerals i e phosphates arsenates silicates and tungstates yielding 230 th 234 u ages of at least 250 ka

the evidence for paraglacial sedimentation and its temporal scale in the deglacierizing basin of small river glacier canada abstract spatially sampled suspended sediment data from extra channel surfaces of different ages during rainfall events were used to infer the timescale of landscape adjustment to little ice age lia deglacierization at small river glacier canada surface ages were determined by aerial photograph interpretation turbidimeters were installed in three ephemeral channels on young mature and old surfaces and their response to rainfall events of different magnitudes recorded results showed young ice proximal surfaces exposed since 1977 were increasingly vulnerable to mobilization during rainfall events a suspended sediment response from old surfaces exposed since 1910 was recorded for only three events with 5 and 30 year return periods the intensity and duration of rainfall events therefore had to increase in magnitude to mobilize sediment on surfaces of increasing maturity hysteresis in the channel suspended sediment response further confirmed the dependence of surface response on rainfall event magnitude the rapid temporal decline in surface response indicated that surface armoring or sediment exhaustion is stabilizing surfaces within decades of exposure from the lia maximum ca 1910 at small river glacier however further perturbation for example by glacial advance or extreme climatic events would likely modify the pattern of suspended sediment yields by changing terrain surface mobilization thresholds and reconfiguring channel sediment stores we therefore suggest that it is difficult to determine when paraglacial sedimentation ceases to influence suspended sediment yields and therefore significantly limiting the usefulness of the term to describe the period of suspended sediment yield adjustment following deglacierization

inclined k ar illite age spectra in brittle fault gouges effects of fault reactivation and wall rock contamination k ar clay fraction ages of brittle faults often vary with grain size decreasing in the finer size fractions producing an inclined age grain size spectrum k ar ages and mineralogical characterization of gouges from two normal faults in the kongsberg silver mines southern norway suggest that inclined spectra derived from brittle fault rocks reflect the mixing of inherited components with authigenic mineral phases the ages of the coarsest and finest fractions constrain faulting at c 260 270 ma and reactivation around 200 210 ma respectively this study demonstrates how wall rock contamination influences the k ar age of the coarsest size fractions and that authigenic illite and k feldspar can crystallize synkinematically under equivalent conditions and thus yield the same k ar ages

particle size analysis of the sediment suspended in a proglacial stream glacier de tsidjiore nouve switzerland hourly at a point samples of suspended sediment taken from the outflow stream of glacier de tsidjiore nouve switzerland over a 60 day sampling period n 1440 are shown to be dominantly composed of silt sized particles particle size sem and xrd analyses indicate a subglacial provenance for the suspended sediment temporal variations in particle size and sorting correspond poorly to fluctuations in water discharge being dominated by erratic hour to hour fluctuations and clockwise hysteresis over diurnal flow events examination of grain size and sorting dynamics over snowmelt and icemelt related ablation events during precipitation events and during glacier drainage events enables some inferences to be drawn regarding sediment source areas and supply regimes we conclude that although the bulk of the suspended sediment in the proglacial stream of glacier de tsidjiore nouve is derived directly from subglacial sources with occasional contributions from the valley train during rapid snowmelt and heavy rainfall periods a portion of the suspended load undergoes intermittent flush fall transfer through the proglacial zone which acts as a sediment source during rising flows and as a sink during periods of waning flow

hydroclimatic influence on particle size distribution of suspended sediments evacuated from debris covered chorabari glacier upper mandakini catchment central himalaya abstract sediments released from high altitude glaciers exhibit varying evacuation patterns and transport characteristics owing to the presence of thick debris cover over the glacier despite the recent needs for integrated hydrometeorological studies in the himalaya little is known about the impacts of suspended sediment on hydropower generation reservoir sedimentation and abrasion of turbine components present study involves analysis of particle size distribution of suspended sediments to understand sediment evacuation patterns and transport characteristics in variable energy conditions during the ablation season peak suspended sediments were evacuated during extreme rainfall events the estimated seasonal modern sediment erosion rate varies from 0 6 to 2 3 mm y 1 for the study period 2009 2012 the analysis shows dominance of medium silt sized to fine sand sized particles having sediment size of 0 0156 0 25 mm corresponding to 70 80 without any significant seasonal variation these transported sediments show that they are poorly sorted coarser in nature with a nearly symmetrical to coarse skewed texture and kurtosis analysis suggesting mesokurtic distribution of sediments the particle size fraction ranges between 4 65 and 5 23 which is dominantly medium to coarse silty in texture results indicate that suspended sediments are evacuated in highly variable energy conditions through subglacial transport pathways because of increase in availability of meltwater with the progressive ablation season bulk geochemical characterization has been carried out to differentiate the source of suspended sediments and intensity of weathering chemical index of alterations cia values of sediment flux range from 54 68 to 55 18 compared to the upper continental crust ucc 50 indicating moderate intensity of weathering mean seasonal 2009 2012 elemental fluxes and their contribution to the suspended sediment flux reflect that si and al are responsible for about 85 of the total detrital elemental flux trace elements show high concentrations of radioactive elements like u th pb and rb that suggest their high anomalous presence in the catchment lithology an overall study indicates that the hydroclimatic conditions over the debris covered glacier play a dominant controlling factor in erosion transportation and evacuation of suspended sediments during the ablation season

particle size characteristics of suspended sediment transported in meltwater from the gangotri glacier central himalaya an indicator of subglacial sediment evacuation abstract proglacial meltwater streams draining out of the himalayan glaciers carry considerable amounts of suspended sediment with a variety of particle sizes because of the supraglacial englacial and subglacial debris as well as formation of sediments from erosion by the movement of the ice this paper examines particle size transported in the proglacial meltwater stream of gangotri glacier for seven consecutive melt seasons may october 2000 2006 in order to provide information on i temporal variations in the particle size distribution ii texture and mineralogy of the sediments and iii origin and evacuation pattern of the sediments our results indicate dominance of silt size 0 002 0 06 mm particles 71 followed by sand size 0 06 0 6 mm particles 24 and clay size

compositional variation within some glauconites and illites and implications for their stability and origins textural mineralogical and chemical data are presented for glauconites and illites from the lower cretaceous glauconitic sand formation alberta canada single crystal analyses by scanning transmission electron microscopy stem indicate that both glauconite 29 analyses and illite 44 analyses correspond very closely to ideal dioctahedral structures al dominates the octahedral sheet in illite very extensive a1 for feiii substitution was also found in some of the glauconites much more than previously recorded the dioctahedral mica structure is clearly very stable and flexible with respect to a1 for feiii substitution iron poor glauconites were found associated with pyrite we believe that glauconites tend to lose iron progressively during burial diagenesis especially where pore water iron activities are low high hs activity and low eh it seems probable that a1 for si tetrahedral substitution also takes place during diagenesis with consequent loss of swelling properties this is the same trend which is responsible for conversion of smectite to illite glauconite forms only where sediments reside for lengthy periods at the interface between oxidizing and reducing environments where fe3 is transiently available in solution related marine and terrestrial nontronites also form only in similar interface environments

saturated hydrocarbon biomarkers in oils of late precambrian age from eastern siberia abstract large quantities of petroleum derived from source rocks of late precambrian early cambrian age have been discovered in the lena tunguska region of eastern siberia over the last twenty five years we have examined three oils with presumed late precambrian vendian source rocks from this region for c 15 saturated hydrocarbon biomarkers using gas chromatography gc and gas chromatography mass spectrometry gc ms our results show these oils to have many characteristics in common with other oils of similar age from eastern siberia and oman amongst the compounds detected in the three oils analyzed were 1 n alkanes which show a marine derived distribution 2 centrally branched monomethyl alkanes 3 acyclic isoprenoids pr ph 1 4 tricyclic and tetracyclic terpanes 5 hopanes 6 c 29 unrearranged steranes and 7 c 30 nuclear steranes all of these compounds with the exception of the 4 methylsteranes which on current biochemical knowledge are unexpected in oils of this age can be assigned a prokaryotic source this and other evidence such as the lack of diasteranes suggest microorganism were the major contributors to organic matter deposited as part of a carbonate source rock

brittle structural facies analysis a diagnostic method to unravel and date multiple slip events of long lived faults abstract regional scale faults typically experience complex long lasting histories commonly recording evidence of multiple reactivation events therefore they contain multiscalar structural domains characterised by varying microstructures mineralogical compositions and kinematics these domains result from differential strain partitioning during the recorded faulting stages and as a result can preserve the isotopic and kinematic signature of the different slip periods their detailed structural analysis integrated with k ar dating of the fault rock assemblage can help to identify these commonly tightly juxtaposed although not coeval domains which we refer herein to as brittle structural facies bsf bsf analysis is pivotal i to understand the structural heterogeneity of fault zones ii the diachronic formation of geometrically and kinematically complex fault cores and iii to reconstruct faults evolution in time and through space following this approach this study relies on meso and microstructural analysis chemical characterisation and k ar dating to unravel the evolution of the laerdal gjende fault lgf southwestern norway the lgf is a multiply reactivated top to the nw extensional fault with a 1 m thick poorly consolidated core we recognised sampled and characterised five bsf i indurated dark reddish gouge ii poorly consolidated cataclasite iii weakly foliated greenish gouge iv clay rich gouge and v a few mm thick clay smear decorating the principal slip surface samples were separated into five grain size fractions from

climate variability on the south eastern tibetan plateau since the lateglacial based on a multiproxy approach from lake naleng comparing pollen and non pollen signals a multi proxy lateglacial environmental record is described from lake naleng 31 10 degrees n 99 75 degrees e 4200 m above sea level situated on south eastern tibetan plateau to gain deeper insights into the hydrological and palaeoclimate development since 17 7 cal ka bp palynological reconstructions of variations in mean annual precipitation map and temperature mat sedimentological data and sediment chemistry including weathering indicators provide a multi faceted picture of local and regional environmental changes since the lateglacial principal component analyses of all parameters provide information on interrelationships between each parameters which help to evaluate their traceability to temperature and precipitation and to estimate their usability as proxy indicators for local and or regional variations during the lateglacial from 17 7 to 14 0 cal ka bp lake naleng experienced cold and dry climate conditions with low biological productivity and supply of unaltered fine grained material due to the high supply of glacier milk during the second half of the lateglacial climate conditions changed abruptly increases in mat from 4 to 2 2 degrees c and map from 500 mm to 820 mm between 14 0 and 13 0 cal ka bp indicate a climate amelioration this time interval can be correlated to the bolling allerod b a warming period in the north atlantic region and is followed by the younger dryas cold reversal indicated by abrupt decreases of mat from 2 2 to 5 degrees c and map from 820 to 650 mm the onset of the holocene at about 11 5 cal ka bp is indicated by rises in reconstructed mat from 5 to about 03 degrees c and map from 600 mm to 950 mm which led to an increased supply of weathered material and higher biological productivity between 5 0 and 3 0 cal ka bp mat increases to about 0 2 degrees c and map rises to maximum values of about 1000 mm followed by slightly decreasing mat and map between 3 0 and 0 cal ka bp the biogeochemical parameters total organic carbon toc c n delta c 13 org and weathering indicators e g the chemical index of alteration cia and sr ba are directly erosion of soils or indirectly changing provenance related to moisture availability on the south eastern tp and shows matching regional climate oscillations since the lateglacial in comparison to other lateglacial records from the tp map reconstructions from lake naleng indicate wetter climate conditions in the south eastern part of the tp and dryer conditions farther away from moisture sources c 2015 elsevier ltd all rights reserved

hydrothermal and unexpected diagenetic alteration in permian shales of the lodeve epigenetic u deposit of southern france traced by k ar illite and k feldspar dating abstract mineralogical and chemical analyses combined with k ar dating of illite and k feldspars were carried out on bulk samples and different fractions from permian shales around the lodeve u deposit to identify diagenetic and hydrothermal alteration episodes and their timing authigenic 2m1 and 1m illite with k ar ages between 270 and 245 ma are the predominant mineral types in the shales they are of early diagenetic origin relative to deposition and formed apparently directly from pyroclastic materials in a lagoonal to deltaic environment under semi arid conditions albite and a first generation of k feldspar developed by a replacement of analcime the k feldspar growing only in the former lagoonal environment that favored also early diagenetic dolomitization at the expense of calcite the hydrothermally altered shales next to the u deposit contain authigenic quartz fe chlorite neoformed illite and a second generation k feldspar with k ar ages beginning at about 220 ma triassic although jurassic and cretaceous ages were also obtained this younger age spectrum jurassic cretaceous is close to previous u pb isotope data from the u deposit probably reflecting several episodes of u mobilization therefore the hydrothermal activity extended episodically from triassic to cretaceous time within the u deposit the hydrothermal temperatures attained locally 220 c as the k ar system of illite from early permian diagenesis is partially reset triassic hot fluids ascended along faults into the northern area of the lodeve basin during an initial rifting of the nearby western tethys ocean further fluid pulses were recorded at lodeve during the opening of the north atlantic and separation of europe from africa jurassic cretaceous which also caused the peak hydrothermal activities in central and western europe as the lodeve area is located between two independently developing oceans it could have been supplied with hot fluids for a long period of time

mesozoic hydrothermal impact on rotliegende and bunter immature sandstones of the high rhine trough and its adjacent eastern area southern black forest germany abstract the mesozoic hydrothermal and geodynamic evolution of a complex region of the european crust is studied here on immature and highly reactive rotliegende and bunter sandstones of the intramontane high rhine trough southern black forest and its adjacent eastern area bounded by the upper rhine graben and the alpine foreland microscopic observations outline varied degrees of illitization of detrital feldspar grains muscovite flakes and illite particles xrd analysis shows that the clay fractions are dominated by illite with minor illite smectite mixed layered minerals of r3 and r1 ordering the chemical composition of these minerals is controlled by precursor minerals since the illitic material inherited its chemical components from detrital muscovite and illite towards the centre of the trough the sandstones were more strongly affected by the hydrothermal impact showing extensive replacement of feldspar grains by al rich illite k ar dating of the authigenic illite type material points to multiple hydrothermal alteration episodes a late jurassic event at 147 ma seems to have affected extensively the study area especially towards the centre of the trough at the periphery of the trough relics of an early jurassic activity are likely preserved an additional early cretaceous hydrothermal event seems to have occurred locally near schopfheim and next to the rhine graben boundary fault long before its main rifting phase the 147 ma event was obtained also nearby in the previously investigated breisgau schramberg offenburg teinach and baden baden troughs and is characteristic for the black forest and some other areas outside this region it concludes obviously a period of regional hydrothermal activities between 160 and 145 ma whereas the early jurassic and cretaceous signatures are also known throughout central and western europe suggesting repeated fluid pulses the hydrothermal flows were controlled by reactivated basement faults due to periods of extensive reorientation of the tectonic stress during the break up of pangaea illitization was triggered by hot and low saline solutions of about 180 c and eq whereas a later fluid pulse of about 80 c and 20 wt nacl eq caused quartz overgrowth fluid flows delivered by the long lasting orogeny of the nearby alps were probably limited towards the black forest becoming part of the european margin of the tethys in the mesozoic the pre alp area evidently developed a separate fluid flow system

the post variscan tectonic thermal activity in the southeastern metalliferous province of the french massif central revisited with k ar ages of illite abstract this study deals with k ar data of illite and illite rich mixed layers of cambrian and permian metasediments that were subjected to tectono thermal episodes in the montdardier and mas lavayre ore districts of the southeastern massif central france the objective was to differentiate events that altered the metal rich deposits from those that affected only barren host rocks close to the ores on the basis of combined mineralogical analyses and isotopic determinations of the clay material successive tectono thermal events induced illitization at 288 10 246 9 197 6 176 6 and 107 4 ma and probably at 136 4 ma the lack of major geodynamic activities near the studied ore deposits during these times hypothesizes periodic long distance migrations of fluids in the continental crust to explain their occurrences metals seem to have been concentrated at specific places but apparently they were not deposited or altered during post visean tectono thermal pulses recorded by the associated illite the tectonic thermal history of the les malines district confirms that repetitive geodynamic re activations induced local heat transfers however the episode at 246 9 ma apparently did not affect the earlier deposited ores while that at 35 40 ma found in coffinite at pierre plantees was probably not induced by a thermal event but by an alteration event that did not affect the k ar system of the surrounding clay material

a lateglacial and holocene lake record from the nianbaoyeze mountains and inferences of lake glacier and climate evolution on the eastern tibetan plateau abstract our 12 81 m long record from lake ximencuo provides insight into the lateglacial and holocene evolution of the lake and the nianbaoyeze glacier in its catchment and the regional climate history since 19 kyr lake ximencuo was a permanent deep lake throughout its history in contrast to numerous lakes on the tibetan plateau which experienced shallow lake levels or even desiccation during the lateglacial lake ximencuo was fed by large quantities of meltwater in the lateglacial the existence of glaciated upper catchment areas is apparently a prerequisite for lakes on the tibetan plateau which maintained relatively high water levels during the generally cold and dry periods following the global lgm 21 kyr a minor re advance of the nianbaoyeze glacier was recorded coeval with the greenland stadial 2a 16 4 and 14 5 kyr followed by rapid warming apparently synchronous with the greenland interstadial 1 warmest conditions were recorded at lake ximencuo during the early holocene which was punctured by a remarkable pulse of climate deterioration around 8 3 kyr this spell represents probably the 8 2 kyr event of the north atlantic region suggesting that it had a significant impact on the tibetan plateau colder conditions of longer duration occurred from 4 7 to 3 7 kyr apparently in phase with numerous records signalling colder and drier conditions on the tibetan plateau two minor spells of colder conditions and probably catchment erosion were recorded in the late holocene between 2 0 and 1 4 kyr and between 0 5 and 0 1 kyr with the latter representing the little ice age it is unclear whether human activities may have accelerated or even solely triggered the late holocene erosion events

subglacial hydrology and sediment transport at bondhusbreen southwest norway tunnels driven in rock under the glacier bondhusbreen in norway and thence upward to the ice rock interface provide a rare opportunity to study a subglacial drainage system early in the melt season suspended sediment discharges in the subglacial water channels are large and channels apparently change position these effects are inferred to be a consequence of increased separation of ice from the bed due to increased water pressure water pressures are believed to be high at this time of year because water channels having closed by plastic deformation during the winter when discharges are low are too small to handle the increasing spring discharges water thus backs up in the channel system calculations suggest that further changes in channel position occur as discharges increase because the potential energy released by the water is able to melt ice in the walls of channels faster than it is replaced by inward flow of ice channels can thus trend diagonally across the direction of glacier flow although such changes may occur at any time during the melt season in response to variations in discharge there appears to be a seasonal evolution of the drainage pattern under bondhusbreen that is repeated each year these shifting channel patterns make the engineering task of locating and diverting water beneath glaciers more difficult than anticipated

determining the sources of suspended sediment in a forested catchment in southeastern australia 1 knowledge is scarce regarding the relative contributions from harvested areas and unsealed roads to sediments in forested catchments we investigate the source composition of suspended sediment using sediment tracers and an improved multivariate mixing model sediment samples were collected during six rainfall events geochemical and radiometric tracer properties were corrected for particle size and organic content as well as conservativeness during erosion and sediment delivery the mixing model incorporates variability of the tracer properties using a monte carlo simulation technique mean sediment contribution from the undisturbed forest was 50 70 harvested areas gravel surfaced roads and ungravelled roads contributed 5 15 6 14 and 12 25 respectively the unsealed roads contribute 20 to 60 times more sediment than the undisturbed forest and about 10 times more sediment than the harvested areas on a per unit area basis harvested areas contribute 1 to 5 times greater sediment than the undisturbed forest these results support other studies that identify unsealed roads as important sediment sources in forested catchments

the thermal significance of potassium feldspar k ar ages inferred from age spectrum results 40ar39ar age spectrum analyses of three microcline separates from the separation point batholith northwest nelson new zealand which cooled slowly 5 c ma 1 through the temperature zone of partial radiogenic 40ar accumulation are characterized by a linear age increase over the first 65 percent of gas release with the lowest ages 80 ma corresponding to the time that the samples cooled below about 100 c the last 35 percent of 39ar released from the microclines yields plateau ages 103 99 and 93 ma which reflect the different bulk mineral ages and correspond to cooling temperatures between about 130 to 160 c theoretical calculations confirm the likelihood of diffusion gradients in feldspars cooling at rates 5 c ma 1 diffusion parameters calculated from the 39ar release yield an activation energy e 28 8 1 9 kcal mol 1 and a frequency factor grain size parameter d0l2 5 6 3 9 14sec 1 this arrhenius relationship corresponds to a closure temperature of 132 13 c which is very similar to the independently estimated temperature from the observed diffusion compensation correlation this d0l2 implies an average diffusion half width of about 3 m similar to the half width of the perthite lamellae in the feldspars the range in microcline k ar ages from the separation point batholith is the result of relatively small temperature differences within the pluton during cooling comparison of the diffusion laws determined for microcline with those for anorthoclases and other homogeneous k feldspars e 40 to 52 kcal mol 1 reveals that ar diffusion is more highly temperature dependent in the disordered structural state than in the ordered structural state previously published u shaped age spectra are probably the result of the superimposition of excess 40ar upon diffusion profiles of the kind described here

an inexpensive turbidimeter for monitoring suspended sediment abstract temporal and spatial variability of suspended sediment in proglacial streams means that discrete monitoring is unlikely to characterize suspended sediment patterns accurately continuously recording turbidimeters provide a solution to the temporal problem of sampling however the problem of spatially limited sampling is constrained largely by the cost of establishing networks of commercially available turbidimeters in this paper we present the design and testing of an inexpensive custom built datalogger compatible and rugged infrared nephelometric turbidimeter the hobs laboratory testing showed that the hobs was most sensitive to coarse clay and fine silt fractions the dominant particle sizes transported in proglacial streams further testing showed that the hobs had a non linear but regular response to bulk sediment concentrations from 0 to 3500 mg l 1 with explained variances of 99 2 to 99 8 in the field the hobs showed a linear response up to 2000 mg l 1 and a non linear response up to 10 000 mg l 1 with explained variances between 75 and 83 this variability emphasizes the necessity of individual site specific field calibrations the hobs s sensitivity to a wide range of suspended sediment concentrations is particularly suited for use in proglacial streams where large fluctuations in concentration are likely the generic design low cost and good performance of the hobs suggests potential for application in other environments where distributed monitoring of suspended sediment is of interest

experimental investigations of the weathering of suspended sediment by alpine glacial meltwater the magnitude and processes of solute acquisition by dilute meltwater in contact with suspended sediment in the channelized component of the hydroglacial system have been investigated through a suite of controlled laboratory experiments constrained by field data from haut glacier d arolla valais switzerland the effects of the water to rock ratio particle size crushing repeated wetting and the availability of protons on the rate of solute acquisition are demonstrated these free drift experiments suggest that the rock flour is extremely geochemically reactive and that dilute quickflow waters are certain to acquire solute from suspended sediment these data have important implications for hydrological interpretations based on the solute content of glacial meltwater mixing model calculations geochemical denudation rates and solute provenance studies

chemical and physical characteristics of iron oxides in riverine and glacial meltwater sediments abstract the speciation and grain size distribution of iron have been examined in several riverine and glacial sediments in order to evaluate controls on the concentrations and modes of occurrence of iron oxides in weathering derived particulates three operationally defined fractions have been recognised relating to the reactivity of iron towards dissolved sulphide 1 highly reactive iron fe hr consisting of ferric oxides 2 poorly reactive iron fe pr consisting of magnetite and some sheet silicate iron and 3 unreactive residual silicate iron fe u the finer fractions of each riverine and glacial suite are enriched in fe hr and usually also have higher fe hr fet ratios however coarser fractions may also have elevated fe hr contents and relationships of fe hr to both surface area and al indicate that iron oxides dominantly occur in association with the surfaces of aluminosilicate minerals which are common in finer grained fractions but may also be relatively enriched in coarser fractions a similar range of fe hr surface loadings is evident in the riverine and glacial meltwater suites from 0 6 to 1 8 mg fe m 2 for the riverine sediments and 0 5 to 1 5 mg fe m 2 for the glacial meltwater sediments despite wide variations in catchment bedrock lithology and climatic conditions significantly lower iron oxide loadings 0 1 mg fe m 2 were found in subglacial sediments most fe hr is closely associated with organic c although the latter occurs as blebs or smears rather than continuous coatings e g ransom et al 1997 ransom b bennett r h baerwald r shea k 1997 tem study of in situ organic matter on continental margins occurrence and the monolayer hypothesis mar geol 138 1 9 electron microscope observations show that iron oxides may occur as nanoparticulate 10 20 nm spheres at the edges of sheet aluminosilicate minerals as crystalline oxides infilling surface pits in coarser grained aluminosilicate minerals and occasionally as discrete crystalline oxides the similar occurrences of iron oxides in both riverine and glacial environments indicates that the delivery of reactive iron oxides to the oceans during glacial interglacial cycles will be affected by the masses and grain size characteristics of sediments delivered by glacial and riverine fluxes rather than by differences in iron mineralogy these delivery rates will be modified by behaviour of the oxide nanoparticles during transport from the continents

a major late jurassic fluid event at the basin basement unconformity in western france 40ar 39ar and k ar dating fluid chemistry and related geodynamic context the malm lower cretaceous period is often considered to represent a period of time markedly devoid of crustal deformations and of heat and mass transfers in western france although numerous evidences of such transfers are reported in varied basins from western iberia to western africa migrating evaporitic derived brines and seawater interacted with both the sedimentary cover and the basement in the poitou high located at the boundary between aquitaine and paris basins occurring after sedimentation this activity induced significant alterations of the sediments by dolomitization and silicification and the basement by adularization and locally by concentration of f ba pb zn assemblages that are typical of carbonate hosted metal deposits thus metals were leached from metamorphic granitic basement already weathered and peneplaned during triassic time and were redeposited by brines during this main fluid event the main objective of this study was to decipher the timing of this major fluid heat mass transfer on the basis of 40ar 39ar and k ar dating of epigenetic minerals having similar paragenetic and geochemical signatures over an extended area from the atlantic ocean coast to the french massif central a late jurassic fluid stage 146 156 ma significantly younger than what is generally reported in western europe was obtained this fluid event occurred within a segment of a continental margin that was located away from main rift zones and far more than 500 km from major deformation areas such as the main rift or orogenic zones all over western europe these results yield a new concept based on wide wavelength relationships between fluid movements and geodynamic events affecting both the sedimentary basins and their basements

proglacial erosion rates and processes in a glacierized catchment in the swiss alps in the swiss alps climatic changes have not only caused glacier retreat but also likely increased sedimentation downstream of glaciers this material either originates from below the glacier or from periglacial environments exposed as glaciers retreat and often consist of easily erodible sediment griesgletscher s catchment in the swiss alps was examined to quantify erosion in theproglacial area possible hydrological drivers and contributions of the sub and periglacial sources digital elevation models created from annual aerial photographs were subtracted to determine annual volume changes in the proglacial area from 1986 to 2014 these data show a strong increase in proglacial erosion in the decade prior to 2012 coincident with increasing proglacial area size however examination of the gradient between discharge and sediment evacuation and the modeled sediment transport could suggest that the proglacial area began to stabilize and sediment supply is limited the large influx of sediment into the proglacial reservoir which is roughly 2 5 times greater than the amount of sediment eroded from the proglacial area demonstrates the importance of subglacial erosion to the catchment s sediment budget although far more sediment originates subglacially erosion rates in the proglacial area are over 50 times greater than the rest of the catchment in turn both sub and periglacial processes in addition to constraining sediment supply must be considered forassessing future sediment dynamics as glacier area shrinks and proglacial areas grow

composition and origin of clay minerals in holocene sediments from the south eastern north sea the distribution of clay minerals varies systematically in sediments from holocene core material taken along a profile from the east frisian coast to the doggerbank the proportion of illite increases with distance from the coast at the expense of kaolinite whereas slight variations are seen in smectite and chlorite abundances the chemical composition changes and the k rb ratio and k ar isotopic age of illite increase seawards this trend results from progressive mixing processes of riverine detritus with pleistocene fluvioglacial material reworked during the holocene transgression however the clay fluvial flux only became dominant during the decreasing rate of sea level rise in the late holocene especially near the shore for example modern sediments in tidal flats contain 75 of river borne holocene supplied clay detritus whereas this amount is only 10 in modern marine sediments at the doggerbank

reconstructing fluid flow events in lower triassic sandstones of the eastern paris basin by elemental tracing and isotopic dating of nanometric illite crystals lower to middle triassic sandstones from eastern paris basin were buried to a maximum depth of 2500 m at a paleo temperature of about 100 c they contain extensive amounts of authigenic platy and filamentous illite particles similar to those reported in reservoirs generally buried at 3000 to 5000 m and subjected to temperatures of 120 to 150 c to evaluate this unexpected occurrence such sandstones were collected from drill cores between 1825 and 2000 m depth and nanometric sized sub fractions were separated the illite crystals were identified by xrd observed by sem and tem analyzed for their major trace rare earth elements and oxygen isotope compositions and dated by k ar and rb sr illite particles display varied growth features in the rock pore space and on authigenic quartz and adularia that they postdate tem eds crystal chemical in situ data show that the illite lath fiber and platelet morphologies correspond at least to two populations with varied interlayer charges between 0 7 and 0 9 in the former and between 0 8 and 1 0 in the latter the fe fe mg ratio being higher in the platelets except for the deeper conglomerate the paas normalized ree patterns of the illite crystals are bell shaped enriched in middle rees ca carbonates and ca phosphates were detected together with illite in the separates these soluble components yield 87sr 86sr ratios that are not strictly in chemical equilibrium with the illite crystals suggesting successive fluids flows with different chemical compositions the k ar data of finer 0 05 m illite separates confirm two crystallization events at 179 4 4 5 and 149 4 2 5 ma during the early and late jurassic the slightly coarser fractions contain also earlier crystallized or detrital k bearing minerals characterized by lower 18o values the 18o of the finest authigenic illite separates tends to decrease slightly with depth from 18 2 0 2 to 16 3 0 2 suggesting different but contemporaneous crystallization conditions deeper in the section the illite platelets and filaments crystallized in changing physical chemical crystallization conditions induced by fluids flows through the host rock pore system these flow events were probably driven by repetitive rifting episodes of the north atlantic ocean although located several hundreds kilometers away from eastern paris basin and or by fracturing events in the nearby basement of the vosges massif complex relationships between geodynamical events thermal anomalies and advective fluids confirm that remote tectonic activities can impact quiescent basins even if located far from tectono thermal activities by discrete and long distance fluid flows

environmental assessment from the sedimentary record of high latitude fiords the sedimentary record of fiords at high latitude where global change may be occurring earliest and will be greatest has the potential for assessment of environmental change at both low resolution the scale of millennia and high resolution decadal to less than daily unlike the lacustrine record which has been used very successfully in these studies the sedimentary processes and thus the sedimentary deposits of fiords differ 1 in the role of salt water in inhibiting mixing and promoting flocculation and through the role of sea ice 2 in the exchange of mass and energy with the much larger ocean beyond and 3 in the role of benthic biota in the sedimentary environment the work reviewed in this paper shows that fiord sediments are being used to assess sedimentary and oceanic processes as well as glacial periglacial and geomorphic history and that they are important proxies for long term climate and hydrology recommendations for advancing this work include long term monitoring of conditions in fiords and their drainage basins so that the transfer relations can be more solidly constructed from the proxy of fiord sediment integration of results from fiords in opposite polar latitudes and among proxies especially from lacustrine and ice core records will produce valuable insights assessment of the range of conditions in fiords from the most polar to temperate regions is important to building models of their processes and understanding of the paleoenvironmental signals that can be interpreted from each type

controls on slope to channel fine sediment connectivity in a largely ice free valley hoophorn stream southern alps new zealand there has been little work to date into the controls on slope to channel fine sediment connectivity in alpine environments largely ice free for most of the holocene characterization of these controls can be expected to result in better understanding of how landscapes relax from such perturbations as climate shock we monitored fine sediment mobilization on a slope segment hydrologically connected to a stream in the largely ice free 8 3 km2 hoophorn valley new zealand gerlach traps were installed in ephemeral slope channels to trap surficial material mobilized during rainfall events channel sediment flux was measured using turbidimeters above and below the connected slope and hysteresis patterns in discharge suspended sediment concentrations were used to determine sediment sources over the 96 day measurement period sediment mobilization from the slope segment was limited to rainfall events with increasingly larger particles trapped as event magnitude increased less than 1 of the mass of particles collected during these events was fine sediment during this period 714 t of suspended sediment was transported through the lower gauging station 60 of it during rainfall events channel sediment transfer patterns during these events were dominated by clockwise hysteresis interpreted as remobilization of nearby in channel sources further suggesting limited input of fine sediment from slopes in the lower valley strong counterclockwise hysteresis representing input of fine sediment from slope segments was restricted to the largest storm event jd2 2009 when surfaces in the upper basin were activated the results indicate that the slopes of the lower hoophorn catchment are no longer functioning as sources of fine sediment but rather as sources of coarse material with flux rates controlled by the intensity and duration of rainfall events although speculative these findings suggest a shift to a coarse sediment dominated slope to channel transfer system as the influence of pre holocene glacial erosion declines copyright 2011 john wiley sons ltd

particle size and mineralogical composition of inorganic colloids in glacier melting water and overlying ice in an alpine glacier oberaargletscher switzerland

composite suspended sediment particles and flocculation in glacial meltwaters preliminary evidence from alpine and himalayan basins research over the last decade has shown that the suspended sediment loads of many rivers are dominated by composite particles these particles are also known as aggregates or flocs and are commonly made up of constituent mineral particles which evidence a wide range of grain sizes and organic matter the resulting in situ or effective particle size characteristics of fluvial suspended sediment exert a major control on all processes of entrainment transport and deposition the significance of composite suspended sediment particles in glacial meltwater streams has however not been established existing data on the particle size characteristics of suspended sediment in glacial meltwaters relate to the dispersed mineral fraction absolute particle size which for certain size fractions may bear little relationship to the effective or in situ distribution existing understanding of composite particle formation within freshwater environments would suggest that in stream flocculation processes do not take place in glacial meltwater systems because of the absence of organic binding agents however we report preliminary scanning electron microscopy data for one alpine and two himalayan glaciers that show composite particles are present in the suspended sediment load of the meltwater system the genesis and structure of these composite particles and their constituent grain size characteristics are discussed we present evidence for the existence of both aggregates or composite particles whose features are largely inherited from source materials and flocs which represent composite particles produced by in stream flocculation processes in the absence of organic materials the latter may result solely from electrochemical flocculation in the meltwater sediment system this type of floc formation has not been reported previously in the freshwater fluvial environment further work is needed to test the wider significance of these data and to investigate the effective particle size characteristics of suspended sediment associated with high concentration outburst events such events make a major contribution to suspended sediment fluxes in meltwater streams and may provide conditions that are conducive to composite particle formation by flocculation copyright 2002 john wiley sons ltd

diurnal dynamics of minor and trace elements in stream water draining dongkemadi glacier on the tibetan plateau and its environmental implications abstract global warming has resulted in rapid glacier retreat on the tibetan plateau tp and the impacts of glacier melting on downstream ecosystems remain largely unknown minor and trace elements in stream water draining dongkemadi glacier dg were examined during the ablation season of 2013 dominant ions and elements are hco 3 ca 2 fe and sr water chemistry is controlled by the weathering of calcite oxidation of pyrite and dissolution of evaporites correlations suggests the hydrological e g meltwater generation and routing water residence time and physicochemical e g sorption precipitation oversaturation controls on species concentrations the distribution of metals is featured by the mixture of soluble metal and non metal ligand complexes and free monovalent and divalent ions downstream increased concentrations and or fluxes of some metals and metalloid e g cr cu and as suggest potential environmental impacts discharge normalized cation denudation rate 372 meq m 3 in the dg basin is larger than those from alpine and polar glaciers suggesting a stronger weathering of carbonate with greater abundance on the tp in comparison to other mountain and polar glacial catchments the maximum fe concentration exceeds the usepa guideline and al zn and pb are close to or of the same order of magnitude as liminal values this implies that the tp may face a challenge of ecosystem health and environmental issue in a warming climate

dating multistage paleofluid percolations a k ar and 18o 16o study of fracture illites from altered hercynian plutonites at the basement cover interface poitou high france isotopic age determination of fluid events in basement fractures is of prime importance for the reconstruction of paleo hydraulic regimes however material from fracture or wall rock is not generally easily dated in the case of fractures filled by minerals such as phyllosilicates it can be expected that subsequent fluid circulation may cause partial alteration or recrystallization of the previous phyllosilicates disturbing the isotope signature using a specific methodology including the extraction process without contamination of the finest 0 2 m authigenic fractions identification of clay fractions by x ray diffraction xrd scanning electron microscopy and electron microprobe analysis of stable isotope composition d h 18o and k ar dating fluid event ages can be estimated this methodology was applied to the northwestern margin of the french massif central where basinal brines have interacted with the sedimentary cover infra toarcian formations and the fractured hercynian crystalline basement during periods of unknown age precipitates from brines sealed most basement fractures as carbonates and a recrystallization of early hercynian phengite chlorite into illite and illite smectite minerals occurred in the earlier fractures xrd patterns show that the clay fraction is dominated by illite and ordered mixed layer minerals having a relatively high amount of illite i s r3 in the shallowest samples beneath the paleo surface a late assemblage is identified as a mixture of i s minerals a part of them being characterized by significant amounts of swelling layers i s r0 the d values of the clay fractions are fairly constant around 50 10 but 18o values of the same clay fractions display a wide range from 8 to 18 smow the study of the size fractions between 2 and 0 2 m reveals a correlation between k ar ages and 18o values which cannot be related to a change in the relative amounts of clay minerals deep fractures at depths of 570 and 923 m are characterized by 18o values around 10 3 0 4 smow and old ages ranging from 253 to 272 ma the finest fractions 0 2 m of clays located at shallow level 300 m beneath the paleo surface yield the highest 18o values 15 7 18 2 and the youngest k ar dates 188 to 198 ma these dates are likely to record the extensional episode and thermal anomaly related to the rifting of central atlantic ocean c 190 ma the other important thermal extensional episode which affected the aquitaine basin namely the opening of the gascogne gulf at c 120 ma is not detected by the k ar method on the clay fractions we believe that resetting of clay type k ar ages linked to recrystallization was favoured in the upper part of the basement where the ancient hercynian clay minerals were destabilized by subaerial low temperature alteration during permo triassic times from a methodologic point of view the analytical characterization of several size fractions of clays from reactivated fractures using both stable isotope geochemistry and k ar isotope geochemistry can be considered as a powerful tool for dating fluid events when no suitable material for conventional methods is available

marine biotic signals across a late eocene impact layer at massignano italy evidence for long term environmental perturbations the eocene oligocene transition marks the passage from greenhouse conditions to an icehouse state with progressive global cooling starting in the early middle eocene the late eocene presents substantial evidence for extraterrestrial impacts whose effects on living organisms and climatic changes are still not completely clear a high resolution microfloral and faunal investigation has been carried out in a 4 m thick segment of the massignano global stratotype section and point for the eocene oligocene boundary the studied interval includes a late eocene 35 7 0 4 myr old impactoclastic layer containing several cosmic signatures the impact event recorded at massignano had no abrupt dramatic effects on marine biota in terms of extinction however significant quantitative changes in the calcareous plankton and dinoflagellate cyst assemblages occurred 60 kyr after the impact event the observed pattern is intepreted as reflecting a long term re organization of water structure

processes of debris comminution in the glacial environment and implications for quarts sand grain micromorphology abstract studies of till composition rock crushing and abrasion experiments and detailed consideration of the mechanics of the comminution processes which occur in the subglacial environment suggest that monomineral quartz sand grains are mostly produced by the brittle fracture of larger particles abrasive wear is an inefficient mechanism for producing and modifying quartz sand grains because of the relatively great hardness of quartz viewed under the scanning electron microscope surface textures of subglacially derived quartz sand grains are typically those associated with brittle fracture of quartz since the release of quartz sand grains from bedrock by mechanical weathering may also involve brittle fracture grains which have been passively transported through a glacier may exhibit similar textures to those actively produced in the glacial environment hence the examination of the surface textures of quartz sand grains under the scanning electron microscope is unlikely to be a satisfactory technique for the discrimination of active and passive transport paths through glaciers

contrasting sterane signatures in neoproterozoic marine rocks of australia before and after the acraman asteroid impact abstract organic matter preserved in marine mudstones from three late neoproterozoic depocentres the officer and amadeus basins and the adelaide fold belt was examined using standard microscopic and geochemical methods including gas chromatography mass spectrometry gc ms total organic carbon toc contents of these sediments are typically low

permian climate development in the northern peri tethys area the lodeve basin french massif central compared in a european and global context abstract the lodeve basin which contains an exceptional long and nearly uninterrupted profile of early to late permian continental red beds is well correlated to the other european permocarboniferous basins together they cover the time span from the late pennsylvanian to the permian triassic boundary although these basins were placed within the equatorial belt for the whole permian several climatic changes are recorded in the sediments terrestrial sedimentation is governed by the interaction of climate and tectonics as well as by volcanism to a variable degree therefore small scale climatic variations of the milankovitch band are hardly discernable and if so they could not be correlated between different basins indeed larger scale climatic shifts could be identified it is shown that the shift from the carboniferous icehouse to the mesozoic warmhouse was a multi stage process this global warming resulted in a general aridisation of northern pangea indicated by outspreading playa and sabkha red beds aeolianites and evaporites several short phases of increased humidity interrupted this trend indicated by wet red beds lake sediments and coal deposits in central and southern europe these wet periods are traceable within the late stephanian lower rotliegend gzhelian asselian topmost lower rotliegend asselian sakmarian upper rotliegend i late artinskian early kungurian and upper rotliegend ii zechstein wuchiapingian the aridisation of the northern pangea which accelerated near the sakmarian artinskian transition is attributed to a reorganisation of the major ocean currents cold water currents along the western flank of the pangea indicated by the permian chert event blocks moisture transport from west onto the continent during roadian and wordian the onset of an additional cold water current along the cimmerian continents blocks moisture transport from the east both phenomena together are responsible for the maximum of aridity at the early to middle permian transition additionally the equatorial climate has been affected by an increasing seasonality within the late pennsylvanian and permian caused by the wide shifting of the zone of inter tropical convergence itc over the equator based on a new reconstruction of the pangean assembly in this paper climatic changes in the permian are interpreted and causes of the arid humid arid shifts are examined phases of higher humidity are often related to events of global impact like the waxing and waning of the gondwanan glaciation obtained in the south african karoo basin dwyka group but also regional events had strong climatic influence the zechstein transgression in the northern and southern permian basin as well as the bellerophon transgression of the southern alps caused the wet phase in the wuchiapingian

diurnal hydrological physicochemical controls and sampling methods for minor and trace elements in an alpine glacial hydrological system summary we present diurnal i 0 45 and 0 1 m pore size filtered and ii operationally defined labile particulate associated major minor and trace element concentrations and fluxes in glacial outflow waters draining haut glacier d arolla switzerland we use speciation modelling phreeqci and water suspended sediment interaction experiments are utilised under conditions analogous to the subglacial channellised hydrological system in order to assess controls on and the most suitable sampling methods to investigate short term variations in the mode of major minor and trace element species export from a glacierised headwater catchment 0 45 m pore size filtered major ions sr and u are exported in glacial outflow waters predominately as mobile monovalent or divalent ions or as carbonate complexes and are controlled by hydrological variations over diurnal cycles exhibiting an inverse concentration with increasing meltwater discharge conversely 0 45 m pore size filtered concentrations of most minor and trace elements e g fe mn co ba and pb exhibit variations that are not strongly inter correlated with meltwater discharge or suspended sediment concentrations ssc over diurnal periods the use of 0 45 and 0 1 m pore size filter membranes indicates that significant colloidal material is not passing through the 0 45 m pore size filters and these unsystematic variations are not a result of colloid measurement speciation modelling applied to meltwaters and observations during water rock interaction experiments suggest that these unsystematic temporal variations reflect physicochemical controls this includes sorption and the oversaturation and precipitation of fe and al oxi hydroxides and the co precipitation of other species diurnal ph variations appear important in controlling such short term physicochemical controls which limits such species use for hydrological investigations the percentage of total elemental fluxes exported as the labile particulate associated flux paf for each minor and trace element changes dramatically between and during the diurnal cycles reflecting species specific sensitivity to hydrological and physicochemical controls hydrological interpretations of hydrochemical data must be made carefully when using chemical determinations by icp ms since we demonstrate that measurements will comprise of any material that passes through the filter this can lead to higher concentration measurements than if determined by ion chromatography which measures truly ionic dissolved species

jurassic lake t oo dichi a large alkaline saline lake morrison formation eastern colorado plateau a large alkaline saline lake lake t9oo9dichi9 occupied the entire eastern part of the colorado plateau region during deposition of the brushy basin member of the upper jurassic morrison formation the lake extended from near the site of albuquerque new mexico to near the site of grand junction colorado and occupied a region that encompassed the san juan and ancestral paradox basins making it the largest ancient alkaline saline lake known the lake was typically shallow and frequently evaporated to dryness although the water table was probably never far beneath the surface intermittent streams carried detritus from source areas to the west and southwest far out into the lake basin a reflection of a low depositional gradient and the ephemeral nature of the lake prevailing westerly winds carried silicic volcanic ash to the lake basin from an arc region to the west and southwest a lateral hydrogeochemical gradient characterized by increasing salinity and alkalinity from the margin of the lake to the center developed in pore waters of the lacustrine sediments and resulted in alteration of the ash to a variety of authigenic minerals that define concentric zones within the lake basin the basinward progression of diagenetic mineral zones is smectite clinoptilolite analcime potassium feldspar albite a concomitant lateral zonation of mixed layer illite smectite developed from highly smectitic in the outermost zones to highly illitic in the central zone authigenic albite and illitic mixed layer clay minerals previously thought to require elevated temperatures for formation crystallized during early diagenesis at syndepositional temperatures in the lacus trine sediments of lake t9oo9dichi9 this study presents evidence for a syndepositional origin for both of these minerals these findings have important implications in terms of limiting the use of these minerals as geothermometers recognition of alkaline saline lake deposits in the morrison formation significantly alters interpretations of depositional environments of this formation and it also has important implications for paleoclimatic interpretation late jurassic climate was apparently much more and than had previously been thought in fact sedimentologic evidence suggests that the lake basin was typically dry for extended periods and enjoyed only brief wet intervals this conclusion has important consequences for environmental interpretation of the habitat that was favorable for large herbivorous dinosaurs which thrived in the late jurassic

the fossil geothermal system of the baden baden trough northern black forest f r germany abstract limnic sediments of the upper carboniferous lower permian and triassic from the baden baden trough were hydrothermally altered during the jurassic concentric alteration halos each having a characteristic mineral composition were formed from center to margin zones of sericitization albitization and weak alteration covering an area of 100 km2 are evident these zones indicate decreasing hydrothermal influence whereby the solutions must have risen in the center the chemistry of mica changing systematically from a muscovitic toward an illitic composition also reflects this trend the boron content increases from 75 to 205 ppm the estimated maximum alteration temperature ranges between 240 and 290 c these remarkable changes are obviously early manifestations of geothermal events related to the development of a continental rift rhine graben

fluid origin and migration of the huangshaping w mo polymetallic deposit south china geochemistry and 40ar 39ar geochronology of hydrothermal k feldspars abstract the huangshaping deposit is a world class w mo pb zn cu polymetallic deposit that formed during the jurassic magmatic event in the central nanling region south china in order to reveal the three dimensional development of mineralization and alteration in this complicated fluid rock system four typical hydrothermal k feldspar samples were collected from potassic alteration zones at different elevation levels around main w mo ore bodies followed by precise trace element analysis and 40 ar 39 ar dating the results show that these k feldspars have a pronounced lanthanide tetrad effect with high contents of ga ta nb u y and hree but low concentrations of ba sr eu and zr suggesting a hydrothermal origin additionally correlation between the ca cl k ratios and the apparent ages suggest that metasomatic fluids played an important role in the formation of the hydrothermal k feldspars the plateau 40 ar 39 ar ages which represent the timing of potassic alteration vary from 152 9 0 5 to 154 3 0 6 ma spatially showing younger trends from north to south and from shallow to deep these dates correspond to the previous published molybdenite re os data variations in different elevation levels which record the mineralization event with relatively older ages ranging from 153 8 to 159 4 ma combined with the spatial relation analysis among samples the fluid migration rates associated with the mineralization and alteration are calculated at 10 100 m ma 1 thus we propose a fluid downward migration model for the huangshaping polymetallic deposit

geochemical events documented in inorganic carbon isotopes abstract screening of sampling and analytical data is crucial for the detection of real global shifts in marine 13c against the noise of diagenesis the real global shifts of 13c are of two types 1 long term secular shifts caused by changes in the fractional burial of organic carbon and 2 transient shifts caused by abrupt changes of biological productivity in the surface photic zone both are applicable to stratigraphic correlation but differ in their application to modelling of changes in oceanographic or atmospheric composition a recent compilation found 34 carbon isotope events in the phanerozoic and neoproterozoic equally distributed among positive and negative shifts this in itself attests to a variety of proximate causes of the shifts

abundance and geochemical significance of c2n dialkylalkanes and highly branched c3n alkanes in diverse meso and neoproterozoic sediments several series of branched alkanes with quaternary carbon centers have been detected by gc ms in the saturated hydrocarbon fractions of neoproterozoic sedimentary rocks associated with fossilised microbial mats officer basin south australia and of shallow water carbonates spitsbergen east greenland and baffin island canada a series of 5 5 diethylalkanes was predominant in most of these sediments and was typically accompanied by related series in lower abundance which based on mass spectral characteristics are tentatively assigned as 6 6 diethylalkanes 5 butyl 5 ethylalkanes and 6 butyl 6 ethylalkanes each series displays strong odd or even carbon number preferences several of the sediments contained additional series of structurally undefined c3n alkanes notable for very negative retention time factors which become more negative with increasing molecular weight indicating that branching increases with each c3 addition the strongly sequential carbon preference of the respective c2n and c3n branched alkane series and a predominantly light 13c signature of the 5 5 diethylalkanes cf co occurring n alkanes are consistent with an origin from organisms with a distinct physiology and or carbon source the relatively wide occurrence and high abundance of these branched alkanes in proterozoic sediments containing benthic microbial mats suggests a relationship with specific paleoenvironmental conditions for example strong water column redox gradients that may have been more prevalent than in the phanerozoic