diagenetic mobility of trace elements in sediments covered by a flash flood deposit mn fe and as the vertical distribution and concentrations of fe mn and as were measured in porewaters and sediments recovered with box cores taken each year since the 1996 flood along the main axis of the saguenay fjord and in the baie des ha ha time series analyses reveal that mn remobilization was not significantly affected by the accumulation of the flood deposit authigenic mn oxi hydroxides present at the original sediment water interface and in the flood material were progressively reduced and much of the mn ii diffused to the current interface where it was oxidized and precipitated first order rate constants for the reduction and precipitation of the authigenic mn oxi hydroxides were estimated by fitting the time series data to a diagenetic model on the basis of these rate constants and given that the maximum reactive solid mn remains concentrated in the thin oxic layer near the sediment water interface an upper limit to the biodiffusion coefficient db was also evaluated in contrast to mn fe associated with the authigenic oxi hydroxides at the original interface was mostly trapped as acid volatile sulfides i e avs under the so4 reducing conditions established rapidly after the flood most of the as associated with the authigenic oxi hydroxides at the original buried interface also appears to be trapped with the authigenic sulfides thus limiting its diffusion through the flood deposit

pyrite from concretion pipes in mesozoic shales mineralogical and chemical evidence of hydrothermal origin abstract the origin of mineralized concretion pipes pyrite ba sr sulphates ankerite and other carbonates found in the jurassic black shales of southeastern france the terres noires formation is ascertained in terms of the characteristics of pyrite the morphology 1 is euhedral the habit 2 is cubic or pentagonododecahedral the size of the pipes 3 ranges from a few cubic micrometres to a few cubic centimetres the chemical composition 4 includes 130 700 ppm co 0 7490 ppm ni 100 2490 ppm as up to 9070 ppm cu and up to 300 ppm zn and se sulphur isotopes 34 s cdt 5 7 1 compared to 15 1 17 for jurassic waters and the concentric spatial arrangement of pyrite crystals 5 involves a shale impregnation and is consistent with a synsedimentary exhalation process a hypothetical model of concretion mineralization development is proposed which involves a change from an arseniferous chemistry to a nickeliferous chemistry the concretion pipes could be good indicators of fluid circulations and thermal anomalies in palaeosedimentary environments such as passive continental margins

reconciling regional continuity with local variability in structure uplift and exhumation of the timor orogen abstract along strike variations in orogenic development can be difficult to constrain resulting assumptions projecting similarity or variability along strike can lead to erroneous conclusions at the orogen scale young orogens provide opportunities to document limits of along strike projection and test factors that may control lateral variability here we present new constraints on the history of uplift exhumation and shortening in the timor orogen from west timor indonesia structural mapping documents a foreland thrust stack of jurassic miocene australian margin strata and a hinterland antiformal stack of permo triassic australian continental units duplexed below banda arc lithosphere biostratigraphy within the piggyback central basin reveals earliest deepwater synorogenic deposition at 5 57 5 53 ma uplift from lower to middle bathyal depths at 3 35 2 58 ma and uplift from middle to upper bathyal depths at 2 58 1 30 ma hinterland permo triassic strata yield apatite u th he ages of 0 33 2 76 ma apatite fission track ages of 2 19 3 53 ma and partially reset zircon u th he ages these thermochronology ages are youngest or most strongly reset in the center of the antiformal stack and yield modeled exhumation rates of 0 45 3 31 km myr a balanced cross section reveals a minimum of 300 km of shortening including 210 km of australian continental subduction below the banda forearc when compared to published results from timor leste these data show that the timing of initial collision synorogenic basin uplift and total shortening amount were broadly similar across the island therefore despite along strike changes in orogen morphology and significant small scale spatial variability in deformation first order structural similarity dominates at large scales we suggest that along strike variations in orogen morphology are due to changes in the distribution of deformation within the orogen driven by differences in backstop strength internal wedge strength and basal decollement friction as well as the presence of the wedge top central basin in west timor

selenium profiles in the sediments of the laurentian trough northwest north atlantic abstract the distribution of total selenium in sediments was determined at seven stations along the axis of the laurentian trough the mean content of surface sediment

geochemical correlation in an exhumed submarine channel complex tabernas basin se spain comparison to sedimentological correlation at various length scales abstract whole rock inorganic geochemical data have previously been used to aid characterization and stratigraphic correlation of fossil poor clastic sedimentary deposits although this approach has not yet been calibrated by testing chemostratigraphic correlations against physical stratigraphic correlations from outcrop chemical data from a well exposed siliciclastic succession in a tortonian late miocene submarine slope channel system in the tabernas basin of southern spain were generated using x ray fluorescence supplemented by x ray diffraction sem analysis and light microscopy amongst the 60 elements measured nearly a quarter of them have proved to be useful or reliable for geochemically based correlation at the tested scales 10 m 50 m 100 m these elements are sio2 k2o al2o3 cao and tio2 as well as zr nb th rb cs as and the rare earth elements la nd and ce high resolution bed to bed geochemical correlation is feasible over short distances 10 m geochemical data from sections in beds that are traceable suggest that a given stratigraphic level seems to be geochemically homogeneous with respect to some key elements geochemical data also provide a useful aid for high resolution sedimentary correlation at distances of several tens of meters up to at least 100 m since each individual bed seems to be broadly homogeneous in composition at a larger scale it is possible to discern a provenance signal in geochemical data chemical stratigraphy thus seems to work even in stratigraphically complicated submarine channel complexes

derivation of s and pb in phanerozoic intrusion related metal deposits from neoproterozoic sedimentary pyrite great basin united states the thick 8 km regionally extensive section of neoproterozoic siliciclastic strata terrigenous detrital succession tds in the central and eastern great basin contains sedimentary pyrite characterized by mostly high 34 s values 11 6 to 40 8 70 exceed 10 51 analyses derived from reduction of seawater sulfate and by markedly radiogenic pb isotopes 207 pb 204 pb 19 2 15 analyses acquired from clastic detritus eroded from precambrian cratonal rocks to the east southeast in the overlying paleozoic section pb zn cu ag au deposits associated with jurassic cretaceous and tertiary granitic intrusions intrusion related metal deposits contain galena and other sulfide minerals with s and pb isotope compositions similar to those of tds sedimentary pyrite consistent with derivation of deposit s and pb from tds pyrite minor element abundances in tds pyrite e g pb zn cu ag and au compared to sedimentary and hydrothermal pyrite elsewhere are not noticeably elevated implying that enrichment in source minerals is not a precondition for intrusion related metal deposits three mechanisms for transferring components of tds sedimentary pyrite to intrusion related metal deposits are qualitatively evaluated one mechanism involves 1 decomposition of tds pyrite in thermal aureoles of intruding magmas and 2 aqueous transport and precipitation in thermal or fluid mixing gradients of isotopically heavy s radiogenic pb and possibly other sedimentary pyrite and detrital mineral components as sulfide minerals in intrusion related metal deposits a second mechanism invokes mixing and s isotope exchange in thermal aureoles of pb and s exsolved from magma and derived from decomposition of sedimentary pyrite a third mechanism entails melting of tds strata or assimilation of tds strata by crustal or mantle magmas tds derived or assimilated magmas ascend decompress and exsolve a mixture of tds volatiles including isotopically heavy s and radiogenic pb from sedimentary pyrite and volatiles acquired from deeper crustal or mantle sources in the central and eastern great basin the wide distribution and high density of small to mid sized vein replacement and skarn intrusion related metal deposits in lower paleozoic rocks that contain tds sedimentary pyrite s and pb reflect 1 prolific jurassic cretaceous and tertiary magmatism 2 a regional substrate reservoir of s and pb in permeable and homogeneous siliciclastic strata and 3 relatively small scale concentration of substrate and magmatic components large intrusion related metal deposits in the central and eastern great basin acquired s and most pb from thicker lithospheric sections

capture of arsenic by pyrite in near shore marine sediments abstract evidence of pyrite formation during diagenesis of suboxic sediments in the laurentian trough canada is presented the process is slower than in salt marsh sediments probably due to the low sulfate reduction rate of 2 3 nmol cm 3 day 1 measured in the st lawrence sediments a strong correlation is observed between arsenic and pyrite suggesting the capture of this element in the lattice sites of pyrite with a fe as ratio of 10 3 it is important to consider this association of as with pyrite in the study of the marine geochemistry of fe and as

trace metals in holocene coastal peats and their relation to pyrite formation nw germany abstract three drill cores from the marshlands of nw germany which cover the entire holocene were analyzed at high resolution for bulk composition al fe selected trace metals and stable sulfur isotopes the drill cores contain two lithological types of peat i basal peats overlying pleistocene sands and ii intercalated peats situated between clastic sediments of predominantly marine origin the peat layers are characterized by distinct enrichments in pyrite due to microbial sulfate reduction under almost open system conditions with respect to seawater sulfate as shown by sulfur isotope partitioning the main fe source seems to be the freshwater environment the determination of dissolved and particulate fe of channels and small rivers close to the study area revealed a 50 fold higher fe content of the freshwater environment when compared with north sea water pyrite enrichments are explained by two scenarios i pyrite formation coincides with fen reed peat growth basal and intercalated under the influence of a brackish water zone salinity app 5 15 and ii pyrite was formed after peat growth in the lowest limnic basal peat intervals maximum pyrite accumulation ts 28 occurs in latter peats that contain thin clastic layers as a result of tidal channel activities after peat formation the occurrence of clastic layers may have favoured the inflow of saline groundwater the peat layers are also characterized by enrichments in redox sensitive trace metals as mo re u and cd whereas co cr cu mn ni pb tl and zn reflect the geogenic background leaching experiments have shown that as co cu mo re and tl are predominantly fixed as sulfides and or incorporated into pyrite the remaining trace metals show no distinct trends only cr reveals a strong relation to the lithogenic detritus seawater is the dominating source for as cd mo re and u the remaining trace elements seem to have a freshwater source similar to fe in contrast to the distribution of pyrite highest amounts of redox sensitive trace metals are seen in fen reed peats basal and intercalated that were formed under a direct influence of seawater and brackish water respectively therefore we suggest that saline groundwater entering the basal peats was probably depleted in redox sensitive trace metals e g owing to microbially induced reduction of trace metals and subsequent precipitation as sulfides or fixation by organic matter

the origin and economic potential of sandstone hosted disseminated pb zn mineralization in pyritic shale horizons of the mid proterozoic newland formation montana usa pyritic shale horizons of the newland formation belt series mid proterozoic show striking similarities to proterozoic pyritic shales elsewhere that are host to major lead zinc deposits such as mt isa and mcarthur river however in contrast to these deposits the pyritic shales of the newland formation contain only minute quantities of lead and zinc elevated concentrations of lead and zinc are only found in pore spaces of intercalated sandstone beds petrographic and geochemical data indicate that pyritic shale deposition and elevated lead zinc concentrations in sandstone beds are unrelated that base metal mineralization is controlled by initial porosity and that iron and base metals were derived from different sources

stratigraphy and paleomagnetism of the jaw face section wellsch valley site saskatchewan the basal part of jaw face section at the wellsch valley site some 50 km north northwest of swift current saskatchewan contains mammalian fossils that are considered to be late blancan to early irvingtonian in age it has been sampled for paleomagnetic studies through a thickness of 11 m the section above 8 8 m has normal polarity that below has reversed polarity a tephra which has yielded a minimum fission track age of 0 69 0 11 ma lies within the reversely magnetized part near the top of the fossiliferous zone and just below the reversal at the 8 8 m level therefore the change from normal to reversed polarity at the 8 8 m level is probably the brunhes matuyama reversal at 0 73 ma earlier studies have indicated that the jaramillo 0 9 0 97 ma and olduvai 1 67 1 87 ma normal polarity subzones occur within the lower predominantly reversed part of the jaw face section in this more detailed study we find no evidence of these normal subzones we suggest that earlier results could have been

pyritization of trace metals in anoxic marine sediments the pyritization of reactive trace elements in different anoxic marine sediments was investigated to determine the importance of factors such as h2s reactive fe pyrite content and salinity in controlling this process the areas studied included anoxic sulfidic sediments baffin bay a hypersaline coastal lagoon from texas and green canyon a hemipelagic oil seepage area anoxic nonsulfidic sediments with high sedimentation rates atchafalaya bay mississippi delta system hemipelagic anoxic nonsulfidic sediments with low sedimentation rates gulf of mexico shelf and slope and orca basin an euxinic hypersaline basin and organic rich marsh sediments atchafalaya bay results indicate that the degree of trace metal pyritization dtmp of all trace metals except cd increased with increasing degree of pyritization dop irrespective of the type of sedimentary environment involved however for as hg and mo the dtmpdop values were generally above the 1 1 ratio line whereas the transition metals co cu mn and ni displayed a close to linear increase in dtmp with dop and moderate incorporation into pyrite chromium and the class b metals pb and zn were also gradually incorporated into the pyrite phase but without reaching the dtmp levels exhibited by the transition metals cadmium was not incorporated to a significant extent these results are consistent with the chemical attributes of these different classes of trace elements availability of dissolved trace metals and organic matter content are apparently important factors controlling the incorporation of co cr cu and ni into pyrite in anoxicsulfidic fe poor and h2s rich environments

the denholm landslide saskatchewan part ii analysis a procedure incorporating geological evidence with analytical methods was developed for the back analysis of a multiple retrogressive landslide in cretaceous clay shale the slide mass apparently inactive extends 2 km back from the toe at the river and is seated on a shear zone 100 m deep at the main scarp historical evidence of the slope movement was established from radiocarbon dating of the river alluvium over which the landslide moved the geometry of the landslide when the factor of safety was near unity was determined from historic and stratigraphic evidence and sensitivity analyses the stratigraphy of the slide mass showed that the beds are stretched with very little vertical displacement indicating a mainly translational mechanism along a nearly horizontal shear zone apparently movement has taken place at a slow but steady rate over 11 000 years resulting in a horizontal displacement of 390 430 m at the toe the landslide therefore was analyzed as a series of sliding blocks with a common f

high resolution reconstruction of a holocene coastal sequence nw germany using inorganic geochemical data and diatom inventories abstract holocene deposits of the nw german coastal plain consist of many different lithological facies for example tidal flats brackish water sediments and peat beds the effects of the holocene sea level rise on palaeoenvironmental conditions of this coastal sequence were studied by inorganic geochemical methods in conjunction with diatom analyses three hundred samples from two parallel sediment cores which cover the entire nw german holocene were taken at high resolution and were examined for major and minor elements and bulk parameters selected samples were analysed for redox sensitive trace elements and ree distribution reactive iron and bulk sediment 34 s 32 s ratios chemical parameters for example si al and ca sr ratios and total organic carbon toc contents correlate with depositional factors such as wave energy and lithofacies changes which allow a detailed reconstruction of the palaeoenvironment diatom analyses reveal information about changes between marine brackish and limnic conditions and serve to reconstruct palaeosalinity early diagenetic effects are evident in the toc rich intervals most peat layers are affected by sulphate reduction and resulting pyrite formation as well as by enrichments in redox sensitive trace elements the highest enrichments are seen for as mo re and u indicating a distinct seawater influence s isotope ratios of peat samples are compatible with pyrite formation under both open and closed system conditions depending on exposition to seawater the inorganic geochemical and diatom data suggest limnic conditions at the base of the sequence and repeated changes towards marine conditions within the overlying clastic units on the other hand data obtained from the clastic units yield evidence of a recurrent succession from open to restricted marine brackish lagoonal and finally fen environments clastic sediments overlying peat layers correlate with the increase of marine derived geochemical signatures and pelagic diatoms attest transgressive overlaps the analyses suggest that major controls on the palaeoenvironments were i climate related oscillations of the coast line and ii the morphology of the coastal region allowing marine incursions even into distal semi terrestrial lowlands

pyrite geochemistry in the toarcian posidonia shale of south west germany evidence for contrasting trace element patterns of diagenetic and syngenetic pyrites authigenic pyrite grains from a section of the lower toarcian posidonia shale were analysed for their trace element contents and sulphur isotope compositions the resulting data are used to evaluate the relationship between depositional conditions and pyrite trace element composition by using factor analysis trace elements in pyrite may be assigned to four groups i heavy metals including cu ni co pb bi and tl ii oxyanionic elements as mo and sb iii elements partitioned in sub microscopic sphalerite inclusions zn and cd and iv elements related to organic or silicate impurities ga and v results indicate that trace element contents in pyrite depend on the site and mechanism of pyrite formation with characteristic features being observed for diagenetic and syngenetic pyrites diagenetic pyrite formed within anoxic sediments generally has a high heavy metals content and the degree of pyritization of these elements increases with increasing oxygen deficiency similar to the degree of pyritization of reactive fe the highest gradient in the increase of the degree of trace element pyritization with bottom water oxygenation was found for the elements ni cu mo as tl in contrast syngenetic pyrite formed within a euxinic water column typically is enriched in as mo and sb but is low in heavy metals and the geochemical variation reflects changes in sea water composition

the geochemistry of primary and weathered oil shale and coquina across the julia creek vanadium deposit queensland australia a significant resource of vanadium and molybdenum exists near julia creek australia where the middle cretaceous organic rich toolebuc formation lies between 0 and 25 m of the surface we present and discuss a comprehensive geochemical study of the toolebuc formation and its enclosing stratigraphy near julia creek to understand this ore deposit v and mo contents in fresh facies are strongly associated with total organic carbon toc contents but not with al or caco3 this suggests that v and mo were originally concentrated in the organic fraction however chemical extractions using h2o2 indicate that mo was originally concentrated in pyrite the data also suggest that v was mobilised from organic matter during early diagenesis and became associated with clays as little v was extracted by h2o2 in the fresh samples toc contents in the toolebuc formation were removed during weathering residually enriching trace metals including v and mo and as a result the toc relationship with v and mo disintegrates with weathering both v and mo predominantly became associated with iron oxide hydroxide phases and possibly other unidentified phases as these elements in the weathered facies were highly soluble in the sodium citrate sodium dithionite digestion large shale hosted v and mo deposits such as julia creek offer a potentially viable alternative to the currently mined magnetite hosted deposits a thorough understanding of the formation and host mineral phases for v and mo of these shale deposits however is critical to ensure that these valuable metals can be feasibly extracted

paleomagnetic evidence for multiple late cenozoic glaciations in the tintina trench west central yukon canadathis article is a companion paper to duk rodkin et al also in this issue the tintina trench in west central yukon has preserved an extensive record of late cenozoic preglacial glacial and interglacial deposits these deposits comprise multiple sequences of tills outwash loesses and paleosols the sediments that were laid down directly by ice tills are of both local montane and regional cordilleran provenance the tintina trench area was impacted repeatedly by montane ice from the southern ogilvie mountains to the northwest 2500 m above sea level asl and also repeatedly along its southern extent by cordilleran ice from the selwyn mountains to the east 2759 m asl the latter forming the continental divide in this region we report here the magnetostratigraphy of three sections rock creek 64 13 n 139 07 w west fifteenmile river 64 29 n 139 55 w and east fifteenmile river 64 23 n 139 48 w the majority of the units identified at these sections record late pliocene to mid pleistocene glaciations although relatively thin surficial sequences of late mid

intense pyrite formation under low sulfate conditions in the achterwasser lagoon sw baltic sea in comparison to similar low sulfate coastal environments with anoxic sulfidic sediments the achterwasser lagoon which is part of the oder estuary in the sw baltic sea reveals unexpectedly high pyrite concentrations of up to 7 5 wt pyrite occurs mainly as framboidal grains variable in size with diameters between 1 and 20 m pyritization is not uniform down to the investigated sediment depth of 50 cm the consumption of reactive fe is most efficient in the upper 20 cm of the sediment column leading to degrees of pyritization dop as high as 80 to 95 sediment accumulation in the achterwasser takes place in high productivity waters the content of organic carbon reaches values of up to 10 wt indicating that pyrite formation is not limited by the availability of organic matter although dissolved sulfate concentration is relatively low 2 mmol l in the achterwasser the presence of h2s in the pore water suggests that sulfate is unlikely to limit pyrite authigenesis the lack of free fe ii in the pore waters combined with the possibility of a very efficient transformation of fe monosulfides to pyrite near the sediment water interface suggests that pyrite formation is rather controlled by i the availability of reactive fe which limits the fes formation and by ii the availability of an oxidant which limits the transformation of fes into pyrite the ultimate source for reactive fe is the river oder which provides a high portion of reactive fe 65 of the total fe in the form of suspended particulate matter the surficial sediments of the achterwasser are reduced but are subject to oxidation from the overlying water by resuspension oxidation of the sediments produces sulfur species with oxidation states intermediate between sulfide and sulfate e g thiosulfate and polysulfides which transform fes to fes2 at a significant rate this process of fes recycling is suggested to be responsible for the formation of pyrite in high concentrations near the sediment surface with dop values between 80 and 95 even under low sulfate conditions a postdepositional sulfidization takes place in the deeper part of the sediment column at 22 cm depth where the downward diffusion of h2s is balanced by the upward migration of fe ii the vertical fluctuation of the diffusion front intensifies the pyritization of sediments we suggest that the processes described may occur preferentially in shallow water lagoons with average net sedimentation rates close to zero such environments are prone to surficial sediment resuspension initiating oxidation of fe sulfides near the sediment water interface subsequent fes2 formation as well as postdepositional sulfidization leads to a major pyrite spike at depth within the sediment profile

terrestrial sedimentary pyrites as a potential source of trace metal release to groundwater a case study from the emsland germany abstract pyrite is a common minor constituent of terrestrial freshwater sediments and a sink for trace elements different amounts and morphological types framboids and euhedral crystals of sedimentary pyrites were found in the heavy mineral fraction of cores obtained from several drillholes located in the emsland region nw germany their trace element contents were investigated to assess their potential for groundwater contamination after oxidation e g induced by dewatering or autotrophic denitrification nickel arsenic and cadmium were found in significant concentrations in pyrite geochemical modeling showed that elevated trace metal concentrations in groundwater potentially exceeding drinking water standards should preferentially occur in a less than 1 m thick zone situated around the depth of the redoxcline where nitrate is reduced by pyrite this was confirmed by depth specific groundwater sampling in the emsland and by previously published studies the absolute concentration of released trace metals depends on their content in the pyrite but also strongly on the nitrate load of groundwater

arsenic mobilization in the hyporheic zone of a contaminated stream arsenic behavior was examined in a contaminated stream by sampling the dissolved 0 45 m arsenic and metals in surface water shallow hyporheic zone water and adjacent ground water surface water was oxic and slightly basic and ground water was anoxic and acidic hyporheic zone water had ph values of 6 7 dissolved oxygen concentrations mostly between 0 and 3 mg l 1 and mean concentrations of most metals inbetween surface and ground water sample concentrations however arsenic and iron were enriched in the hyporheic zone most of the hyporheic zone dissolved arsenic was in the form of as iii which is considered to be more toxic to some organisms than as v in the oxic surface water 20 of the total dissolved as was found to occur in its reduced form we hypothesize that upon burial and reduction of fe oxyhydroxides in the streambed sediment bound arsenic is transferred into the dissolved phase as as iii and it is subsequently released into the surface water where it does not immediately reoxidize a continual flux of reduced as to the surface water maintains as iii concentrations above that expected in oxygenated surface waters

evidence for early pleistocene glaciation from borecore stratigraphy in north central alberta canada pleistocene sediments collected in north central alberta canada were subsampled and studied for paleomagnetic remanence characteristics a magnetostratigraphy has been established for sediments previously assumed to represent multiple continental laurentide glaciations but for which no geochronology was available based on the quaternary record elsewhere in alberta and saskatchewan it was thought that some of these sediments were deposited during pre late wisconsinan glaciations the quaternary sedimentary successions of north central alberta have a thickness up to 300 m within buried valleys and are composed of diamicts interbedded with glaciolacustrine and outwash sediments most of the sampled units are not accessible from outcrop and their sedimentology and stratigraphy is derived from core data only in 4 of 16 borecores sampled to date diamict that correlates with the bronson lake formation till is reversely magnetized indicating an early pleistocene age this formation is underlain by eithe