excess 210pb inventories and fluxes along the continental slope and basins of the gulf of papua 1 sediment samples were collected from continental slopes and marginal basins in the gulf of papua and analyzed for excess 210pb to elucidate transport processes of fine grained particles to this region estimated excess 210pb fluxes of 1 0 12 8 dpm cm 2 a 1 were derived from measured seabed inventories highest sediment accumulation rates 0 28 0 35 cm a 1 were measured along the northeastern shelf edge and they decrease in seaward directions and along isobaths to the southwest the excess 210pb flux could result from either focused deposition of high 210pb activity sediments from the continental shelf and upper slope or scavenging of 210pb brought landward from deep sea waters this sediment flux is concentrated in the northeastern gulf of papua where the shelf is narrow and calcium carbonate contents are lowest analysis of sedimentary fabric and 210pb distributions in cores suggests sediment delivery to the slope occurs on a 100 year timescale as both diffuse hemipelagic deposition as well as turbidity flows the flux of sediment in turbidity flows is not well constrained but may be producing additional deep sea accumulation in the moresby trough as well as export from the study area

the younger dryas termination and north atlantic deep water formation insights from climate model simulations and greenland ice cores results from the gisp2 and grip ice cores show that the termination of the younger dryas yd climate event in greenland was a large and extremely fast climate change a reinitiation of north atlantic deep water formation following a shutdown and its associated winter release of heat to the atmosphere has been suggested as the most likely cause of this climate transition to test this idea two general circulation model experiments using genesis have been completed for yd time 12 000 calendar years ago one with low heat flux in the nordic seas 10 w m deep water shutdown and one with high nordic sea heat flux 300 w m active deep water formation comparison of greenland climate differences between these experiments with the ice core records shows that when deep water is turned on much of the yd termination warming is achieved the increase in precipitation is underestimated because of a model tendency to overestimate summertime precipitation which obscures the dominantly wintertime response to the specified forcing the winter storm track shift toward greenland contributes much of the climate change at the yd termination

sources and accumulation of sediment and particulate organic carbon in a subarctic fjard estuary 210pb 137cs and δ13c records from lake melville labrador the sources and distribution of sediment and particulate organic carbon oc to lake melville labrador were characterized to better understand impacts from climate and hydrological changes to the system mass accumulation rates mars across the lake melville system lms were established from 15 sediment cores collected in 2013 and 2014 by fitting excess 210pb 210pbex profiles to a two layer advection diffusion model mars validated using 137cs varied between 0 04 and 0 41 g cm 2 a 1 and overall decreased with increasing distance from the churchill river which drains into goose bay a western extension of lake melville the churchill river is the greatest source of sediment to the system but surprisingly mars were greatest in western lake melville rather than goose bay reflecting the contribution of fine material carried eastward in the churchill river plume and inputs from nearby tributaries a comparison of 137cs and 210pbex inventories to expected atmospheric fallout 1 5 and 23 6 disintegr

hydrated silicate minerals on mars observed by the mars reconnaissance orbiter crism instrument phyllosilicates a class of hydrous mineral first definitively identified on mars by the omega observatoire pour la mineralogie l eau les glaces et l activitie instrument preserve a record of the interaction of water with rocks on mars global mapping showed that phyllosilicates are widespread but are apparently restricted to ancient terrains and a relatively narrow range of mineralogy fe mg and al smectite clays this was interpreted to indicate that phyllosilicate formation occurred during the noachian the earliest geological era of mars and that the conditions necessary for phyllosilicate formation moderate to high ph and high water activity were specific to surface environments during the earliest era of mars s history here we report results from the compact reconnaissance imaging spectrometer for mars crism of phyllosilicate rich regions we expand the diversity of phyllosilicate mineralogy with the identification of kaolinite chlorite and illite or muscovite and a new class of hydrated silicate hydrated silica we observe diverse fe mg oh phyllosilicates and find that smectites such as nontronite and saponite are the most common but chlorites are also present in some locations stratigraphic relationships in the nili fossae region show olivine rich materials overlying phyllosilicate bearing units indicating the cessation of aqueous alteration before emplacement of the olivine bearing unit hundreds of detections of fe mg phyllosilicate in rims ejecta and central peaks of craters in the southern highland noachian cratered terrain indicate excavation of altered crust from depth we also find phyllosilicate in sedimentary deposits clearly laid by water these results point to a rich diversity of noachian environments conducive to habitability

late quaternary sediments and chronology of the northeast labrador shelf karlsefni trough saglek bank links to glacial history core hu87033 015 an 11 m long giant piston core from the western end of karlsefni trough was taken only 25 km from the coast of northernmost labrador the regional acoustic framework was established via a high resolution deep towed huntec dts seismic survey we recognized four acoustic facies that are associated with designated and recovered major lithologic units the ages of these units were determined from 13 accelerator mass spectrometry 14 c dates from marine biogenic carbonates these results suggest that glacial ice was present on the shelf from at least the mid wisconsinan and that the basal sequence contains reworked glacial marine diamicton furthermore our data provide the first evidence that the northern labrador inner shelf was ice free by ca 11 14 c ka the bulk of the postglacial deposition was around 8 2 ka and consists of increased detrital carbonate deposition the deposition of this detrital carbonate is age equivalent with dc 0 on the southeastern baffin shelf and in the north atlantic

patterns and mechanisms of fluvial sediment flux and accumulation in two subarctic fjords nachvak and saglek fjords nunatsiavut canada recent marine sedimentary deposits and river discharge in two subarctic fjords in nunatsiavut northern labrador canada have been studied to elucidate patterns and mechanisms of fluvial sediment transfer and accumulation in the fjords to further our understanding of the longer term sedimentary record multibeam and sub bottom acoustic data and sediment cores were collected in nachvak and saglek fjords within canada s torngat mountains national park as part of the most extensive study of the park s marine resources to date cores were subsampled for x radiography grain size and 210pb 137cs geochronology muddy basin sediments within each fjord are bioturbated indicating circulation of oxygenated bottom water depositional fluxes and inventories of 210pb indicate efficient marine scavenging of 210pb by fine suspended sediments in nachvak fjord with small rivers and steep presently glaciated catchments postglacial and recent sediment accumulation rates are similar implying relatively constant se

calcium sulfate veins characterized by chemcam curiosity at gale crater mars the curiosity rover has analyzed abundant light toned fracture fill material within the yellowknife bay sedimentary deposits the chemcam instrument coupled with mastcam and chemcam remote micro imager images was able to demonstrate that these fracture fills consist of calcium sulfate veins many of which appear to be hydrated at a level expected for gypsum and bassanite anhydrite is locally present and is found in a location characterized by a nodular texture an intricate assemblage of veins crosses the sediments which were likely formed by precipitation from fluids circulating through fractures the presence of veins throughout the entire similar to 5 m thick yellowknife bay sediments suggests that this process occurred well after sedimentation and cementation lithification of those sediments the sulfur rich fluids may have originated in previously precipitated sulfate rich layers either before the deposition of the sheepbed mudstones or from unrelated units such as the sulfates at the base of mount sharp the occurrence of these veins after the episodes of deposition of fluvial sediments at the surface suggests persistent aqueous activity in relatively nonacidic conditions

sediment and particulate organic carbon budgets of a subarctic estuarine fjard lake melville labrador abstract sediment and particulate organic carbon poc budgets constructed for oceanic regions provide a means to quantify the burial of poc providing a baseline against which future change can be measured here we developed the first mass balance budgets of sediment and poc terrestrial and marine for the lake melville system lms goose bay and lake melville in central labrador using previously published data 210pb based mass accumulation rates river discharge and total suspended solids together with measurements of oc and 13c signatures within dated sediment cores collected from the lms basins and water from main tributaries and groswater bay a two end member mixing model was used to establish fractions of terrigenous and marine poc overall our mass balance budgets show that the churchill river is the major supply of sediment 16 7 7 8 108 kg y 1 and pocterr 18 4 6 6 106 kg y 1 to the lms accounting for 47 and 56 of the total input to the system respectively although the churchill river drains directly into goose bay along with the smaller goose river the majority of sediment 12 9 7 8 108 kg y 1 and pocterr 11 8 7 0 106 kg y 1 is transported eastward through the surface water plume into lake melville inputs of pocmar from autochthonous primary production estimated by applying an empirical relationship between sediment surface flux of pocmar and water depth to goose bay 1 8 106 kg y 1 and lake melville 98 3 4 7 106 kg y 1 increase with increasing distance from the churchill river to investigate the potential changes to the sediment load of the churchill river to the lms following impoundment at muskrat falls we calculated the sediment increase using the median reservoir shoreline erosion potential this approach showed that the delivery of sediment and pocterr to the lms by the churchill river may double during the two years following impoundment of the lower churchill river

geomorphic tectonic control of sediment discharge to the ocean the importance of small mountainous rivers analysis of data from 280 rivers discharging to the ocean indicates that sediment loads yields are a log linear function of basin area and maximum elevation of the river basin other factors controlling sediment discharge e g climate runoff appear to have secondary importance a notable exception is the influence of human activity climate and geology on the rivers draining southern asia and oceania sediment fluxes from small mountainous rivers many of which discharge directly onto active margins e g western south and north america and most high standing oceanic islands have been greatly underestimated in previous global sediment budgets perhaps by as much as a factor of three in contrast sediment fluxes to the ocean from large rivers nearly all of which discharge onto passive margins or marginal seas have been overestimated as some of the sediment load is subaerially sequestered in subsiding deltas before the proliferation of dam construction in the latter half of this century rivers

hydrated mineral stratigraphy of ius chasma valles marineris new high resolution spectral and morphologic imaging of deposits on walls and floor of ius chasma extend previous geomorphic mapping and permit a new interpretation of aqueous processes that occurred during the development of valles marineris we identify hydrated mineralogy based on visible near infrared vnir absorptions we map the extents of these units with crism spectral data as well as morphologies in ctx and hirise imagery three cross sections across ius chasma illustrate the interpreted mineral stratigraphy multiple episodes formed and transported hydrated minerals within ius chasma polyhydrated sulfate and kieserite are found within a closed basin at the lowest elevations in the chasma they may have been precipitates in a closed basin or diagenetically altered after deposition fluvial or aeolian processes then deposited layered fe mg smectite and hydrated silicate on the chasma floor postdating the sulfates the smectite apparently was weathered out of noachian age wallrock and transported to the depositional sites the overlying hydrated silicate is interpreted to be an acid leached phyllosilicate transformed from the underlying smectite unit or a smectite jarosite mixture the finely layered smectite and massive hydrated silicate units have an erosional unconformity between them that marks a change in surface water chemistry landslides transported large blocks of wallrock some altered to contain fe mg smectite to the chasma floor after the last episode of normal faulting and subsequent landslides opal was transported short distances into the chasma from a few m thick light toned layer near the top of the wallrock by sapping channels in louros valles alternatively the material was transported into the chasma and then altered to opal the superposition of different types of hydrated minerals and the different fluvial morphologies of the units containing them indicate sequential distinct aqueous environments characterized by alkaline then circum neutral and finally very acidic surface or groundwater chemistry

postglacial sequence stratigraphy of lake melville labrador abstract in lake melville labrador the quaternary glacimarine sediments reflect a single retreat phase of the laurentide ice sheet during the early holocene based on extensive airgun and high resolution seismic surveys sediment deposits are subdivided into thirteen units that are associated with glacial paraglacial and postglacial styles of deposition their distribution patterns reflect paleo positions of a retreating ice margin during the period between 10 000 and 9000 years before present formation of paraglacial deltas during the early to mid holocene 6 9 ka and postglacial tidal influenced deposition during the late holocene

atmospheric transmission of north atlantic heinrich events this research was supported by the u s geological survey global change program and nsf under grants atm 9523584 atm 9632029 and ear 9725554

modern deposition rates and patterns of organic carbon burial in fiordland new zealand fjords are disproportionately important for global organic carbon oc burial relative to their spatial extent and may be important in sequestering atmospheric co2 providing a negative climate feedback within fjords multiple locally variable delivery mechanisms control mineral sediment deposition which in turn modulates oc burial sediment and oc sources in fiordland new zealand include terrigenous input at fjord heads sediment reworking over fjord mouth sills and landslide events from steep fjord walls box cores were analyzed for sedimentary texture sediment accumulation rate and oc content to evaluate the relative importance of each delivery mechanism sediment accumulation was up to 3 4 mm yr in proximal and distal fjord areas with lower rates in medial reaches x radiograph and 210pb stratigraphy indicate mass wasting and surface sediment bioturbation throughout the fjords sediment accumulation rates are inversely correlated with oc spatial heterogeneity in sediment depositional processes and rates is important when evaluating oc burial within fjords

preservation potential of sedimentary event layers preservation potential of sedimentary event layers e g ash layers or tempestites is a function of net sedimentation rate and biogenous mixing rate previous studies that have used an inverse peclet number to scale the problem in terms of advection or diffusion are in error due to the improper inclusion of the surface mixed layer thickness as the sole length scale herein focus is on time scales if the transit time i e time required to advect the signal through the biologically active zone is less than the dissipation time i e time required to destroy the signal then some fraction of the original signal is preserved a simple quantitative model based on the diffusion analogy of sediment mixing estimates the actual percentage of preserved signal under various combinations of sedimentation rate mixing rate and event layer thickness

reconstructed ice flow patterns and ice limits using drift pebble lithology outer nachvak fiord northern labrador discussion on the basis of their analysis of pebble lithologies and age estimates of marine shells the authors presented an interpretation for late quaternary events in outer nachvak fiord that they sav is incom atible with the late wisconsinan ice model of f k k and osh josenhans et al 1986 clark 1988 we believe that much of their data when reinterpreted do not conflict with our reconstruction and in fact can be accommodated by our reconstruction in contrast our data from nachvak fiord and the adjacent continental shelf are not compatible with their hypotheses nor have they directly addressed these data in their hypotheses in this discussion we will evaluate the clast morphologic and chronologic data used by the authors to develop their hypotheses we also summarize our work related to the glacial history of nachvak fiord and the adjacent shelf for the purpose of discussion and comparison with their hypotheses

the origin and preservation of a major hurricane event bed in the northern gulf of mexico hurricane camille 1969 cores collected from mississippi sound in the gulf of mexico were studied using 210 pbxs and 137 cs geochronology x radiography granulometry and a multi sensor core logger our results indicate the presence of a widespread sandy event layer that we attribute to hurricane camille 1969 an initial thickness of more than 10 cm is estimated from the cores which is large compared to the time averaged apparent accumulation rate of 0 29 0 47 cm y 31 physical and biological post depositional processes have reworked the sandy layer producing a regional discontinuity and localized truncation and resulting in an imperfect and biased record of sedimentary processes during the storm the oceanographic and sedimentological processes that would have produced an event bed during hurricane camille are simulated using a series of numerical models i e 1 a parametric cyclone wind model 2 the swan third generation wave model 3 the adcirc 2d finite element hydrodynamic model and 4 a wave current bottom boundary layer model that is coupled to transport and bed conservation equations trans98 the simulated bed ranges from 5 cm to over 100 cm within a tidal channel near the barrier islands seaward of the islands the bed is more than 10 cm in thickness with local variability the magnitude and local variability of the storm bed thickness are consistent with the observed stratigraphy and geochronology on both the landward and seaward sides of the barriers 2002 elsevier science b v all rights reserved

recent sedimentation patterns and facies distribution on the poverty shelf new zealand abstract modern sediment dispersal and accumulation on the poverty shelf off the waipaoa river new zealand is investigated using x radiographic radio isotopic and physical property analyses of nearly 200 box and kasten cores collected in january 2005 aboard the r v kilo moana the high yield small mountainous waipaoa river empties onto a tectonically active narrow margin and represents an important analog for shelf sedimentation in similar environments worldwide x radiographs and bulk density measurements from a multi sensor core logger show three distinct facies on the shelf where physical and or biological factors dominate strata formation spatial distribution of these facies delineates a radial pattern with distance from the river mouth from areas dominated by stratified layers on the inner shelf to mottled muds on the outer shelf demonstrating a continuum of controls from wave reworking to episodic and extreme wet event sedimentation despite a tectonic framework that supports rapid accumulation in two recently identified shelf depocenters analysis of short lived 7 be t 1 2 53 days reveals a broad spatial distribution across and along shelf in surface sediments suggesting rapid transport from the waipaoa source however beryllium 7 inventories are consistent with centennial scale trends observed by other researchers using longer lived 210 pb analyses with highest inventories in the shelf depocenters box core bulk density analyses show lower than average bulk densities within these depocenters and higher than average bulk densities on the inner shelf and between the depocenters these observations confirm rapid deposition of low density muds in the depocenters with higher bulk density possibly physically reworked sediments remaining off the mouth of poverty bay and between the depocenters based on this single observational period there appears to be no fundamental difference between seasonal and longer term accumulation patterns on the poverty shelf

quantitative compositional analysis of martian mafic regions using the mex omega reflectance data 1 methodology uncertainties and examples of application abstract the mars express observatoire pour la mineralogie l eau les glaces et l activite omega collected an unprecedented visible and near infrared hyperspectral dataset covering the low albedo regions of mars we investigate the ability to infer modal abundance of surfaces of these regions from a radiative transfer model developed by shkuratov et al shkuratov y starukhina l hoffmann h arnold g 1999 icarus 137 235 246 and adapted to basaltic surfaces by poulet and erard poulet f erard s 2004 j geophys res 109 e2 doi 10 1029 2003je002179 from omega measurements of mafic surfaces we develop several sensitivity tests to assess the extent to which the model can be applied to predict pyroxene composition high calcium phase and low calcium phase abundance of almost neutral components plagioclase in the near infrared wavelength as well as grain sizes by using a library of selected end members results of the sensitivity tests indicate that the scattering model can estimate both abundances and grain sizes of major basaltic materials of low albedo regions within uncertainties 5 to 15 vol the model is then applied to data from dissected cratered terrains located in terra meridiani the derived grain size including uncertainties is in the 50 500 m range this is consistent with the thermal inertia and albedo of this region which indicates a fine sand sized surface with little dust the abundances of plagioclase 43 57 and pyroxenes 35 45 10 including 11 5 of low calcium phase are in good agreement with previous basalt like compositions of low albedo regions from thermal infrared spectral measurements the method presented in this paper will provide a valuable tool for evaluating the modal mineralogy of other mafic regions of mars observed in the near infrared wavelength range

the formation of sedimentary strata in an allochthonous shelf environment the washington continental shelf nittrouer c a and sternberg r w 1981 the formation of sedimentary strata in an allochthonous shelf environment the washington continental shelf mar geol 42 201 232 models of fine scale 120 m shelf regions the inner shelf sand and mid shelf sandy silt are the predominant accretionary deposits on the shelf important sedimento logical observations obtained by boxcoring the upper 1 2 m of these deposits are a progressive decrease in grain size with distance from the columbia b downward coarsening within the seabed c loss of distinct sedimentary structure homogenization of sediment with distance from the columbia non dimensional parameters based on sediment transport and benthic biological studies can be used to relate rates of sediment mixing re working to rates of accumulation these parameters have the potential for quantitative prediction of strata formation from measurements of active processes physical and biological mixing can be assumed to remain relatively constant in an alongshelf direction on the washington shelf and accumulation rate is known from pb 210 geochronology to decrease away from the columbia together these factors tend to increase the ratio of mixing to accumulation with distance from the columbia and predict the sedimentological observations listed above

interannual variations of snowmelt and refreeze timing on southeast alaskan icefields u s a twice daily satellite observations from the special sensor microwave imager ssm i indicate melt onset and refreeze on southeast alaskan icefields melt and refreeze are based on 37 ghz vertically polarized brightness temperatures t b and diurnal amplitude variations dav two types of melt regime have different summer characteristics onset is characterized by increasing average daily t b and a switch from low to high amplitude dav melt timing calibrated using juneau icefield temperatures correlates well with nearby stream hydrographs some pixels maintain high t b throughout the melt season and return to low amplitude dav after melt onset refreeze on these pixels is identified by decrease in t b and accompanying high amplitude dav other pixels maintain high dav throughout the summer indicating nocturnal refrecze fall refreeze is determined by the end of high amplitude dav interannual variability in melt timing and ablation season length is high melt onset and refreeze timing show a regional tendency toward earlier glacier melt onset and longer ablation seasons from 1988 98

modeling near infrared reflectance spectra of clay and sulfate mixtures and implications for mars high resolution mapping by visible and near infrared orbital spectrometers has revealed a diversity of hydrated mineral deposits on the surface of mars quantitative analysis of mineral abundances within these deposits has the potential to distinguish depositional and diagenetic processes such analysis can also provide important constraints on the nature of putative global and local scale mineralogical transitions on mars however the ability of models to extract quantitative mineral abundances from spectra of mixtures relevant to sedimentary rocks remains largely untested this is particularly true for clay and sulfate minerals which often occur as fine grained components of terrestrial sedimentary rocks and are known to occur in a number of sedimentary deposits on mars this study examines the spectral properties of a suite of mixtures containing the mg sulfate epsomite mixed with varying proportions of smectitic clay saponite nontronite and montmorrilonite the goal of this work is to test the ability of checkerboard linear and intimate non linear mixing models to obtain accurate estimates of mineral abundances under ideal and controlled laboratory conditions the results of this work suggest that 1 spectra of clay sulfate mixtures can be reproduced by checkerboard and intimate mixing models to within 2 absolute reflectance or single scattering albedo 2 clay and epsomite abundance can be modeled to within 5 wt when particle diameter is optimized and 3 the lower threshold for modeling clay in spectra of clay epsomite mixtures is approximately 10 wt below which the models often fail to recognize the presence of clay

a habitable fluvio lacustrine environment at yellowknife bay gale crater mars the curiosity rover discovered fine grained sedimentary rocks which are inferred to represent an ancient lake and preserve evidence of an environment that would have been suited to support a martian biosphere founded on chemolithoautotrophy this aqueous environment was characterized by neutral ph low salinity and variable redox states of both iron and sulfur species carbon hydrogen oxygen sulfur nitrogen and phosphorus were measured directly as key biogenic elements by inference phosphorus is assumed to have been available the environment probably had a minimum duration of hundreds to tens of thousands of years these results highlight the biological viability of fluvial lacustrine environments in the post noachian history of mars

mars surface diversity as revealed by the omega mars express observations the observatoire pour la mineralogie l eau les glaces et l activite omega investigation on board the european space agency mars express mission is mapping the surface composition of mars at a 0 3 to 5 kilometer resolution by means of visible near infrared hyperspectral reflectance imagery the data acquired during the first 9 months of the mission already reveal a diverse and complex surface mineralogy offering key insights into the evolution of mars omega has identified and mapped mafic iron bearing silicates of both the northern and southern crust localized concentrations of hydrated phyllosilicates and sulfates but no carbonates and ices and frosts with a water ice composition of the north polar perennial cap as for the south cap covered by a thin carbon dioxide ice veneer

paleoclimate of mars as captured by the stratigraphic record in gale crater a kilometers thick sedimentary sequence in gale crater exhibits stratigraphic changes in lithology that are consistent with transitions in aqueous and climatic conditions purported to be global in scale the sequence is divided into two formations where the lower formation exhibits a net transition in mineralogy from clay sulfate to sulfate oxide assemblages and is separated from the overlying upper formation by an erosional unconformity superposition and crater counts suggest strata in the lower formation lie along the noachian hesperian time stratigraphic boundary whereas beds in the upper formation which lack signatures indicative of clay minerals or sulfates are thinner more regularly spaced and clearly younger the observed stratigraphic trends are consistent with the rocks at gale crater recording a global transition from a climate favorable to clay mineral formation to one more favorable to forming sulfates and other salts

near infrared spectral reflectance of mineral mixtures systematic combinations of pyroxenes olivine and iron oxides near infrared spectral reflectance data are presented for systematic variations in weight percent of two component mixtures of ferromagnesian and iron oxide minerals mixtures were chosen for application to the study of the dark materials on mars but the results are equally applicable to mafic and ultramafic assemblages elsewhere in the solar system olivine spectral features are greatly reduced in contrast by admixture of other phases but remain distinctive even for low olivine contents clinopyroxene and orthopyroxene mixtures show resolved pyroxene absorptions near 2 m the addition of limonite greatly modifies pyroxene and olivine reflectance but does not fully eliminate distinctive spectral characteristics using only spectral data in the 1 m region it is difficult to differentiate orthopyroxene and limonite goethite in a mixture additional spectral coverage or other evidence may be required for a unique interpretation all composite mineral absorptions observed in this study are either weaker than or intermediate in strength to the end member absorptions and have bandwidths greater than or equal to those for the end members in general spectral properties in an intimate mixture combine in a complex nonadditive manner with features demonstrating a regular but usually nonlinear variation as a function of end member phase proportions

near infrared spectroscopy of lacustrine sediments in the great salt lake desert an analog study for martian paleolake basins the identification and characterization of aqueous minerals within ancient lacustrine environments on mars are a high priority for determining the past habitability of the red planet terrestrial analog studies are useful both for understanding the mineralogy of lacustrine sediments how the mineralogy varies with location in a lacustrine environment and for validating the use of certain techniques such as visible near infrared vnir spectroscopy in this study sediments from the pilot valley paleolake basin of the great salt lake desert were characterized using vnir as an analog for martian paleolake basins the spectra and subsequent interpretations were then compared to mineralogical characterization by ground truth methods including x ray diffraction automated scanning electron microscopy and several geochemical analysis techniques in general there is good agreement between vnir and ground truth methods on the major classes of minerals present in the lake sediments and vnir spectra can also easily discriminate between clay dominated and salt dominated lacustrine terrains within the paleolake basin however detection of more detailed mineralogy is difficult with vnir spectra alone as some minerals can dominate the spectra even at very low abundances at this site the vnir spectra are dominated by absorption bands that are most consistent with gypsum and smectites though the ground truth methods reveal more diverse mineral assemblages that include a variety of sulfates primary and secondary phyllosilicates carbonates and chlorides this study provides insight into the limitations regarding the use of vnir in characterizing complex mineral assemblages inherent in lacustrine settings

the opportunity rover s athena science investigation at meridiani planum mars the mars exploration rover opportunity has investigated the landing site in eagle crater and the nearby plains within meridiani planum the soils consist of fine grained basaltic sand and a surface lag of hematite rich spherules spherule fragments and other granules wind ripples are common underlying the thin soil layer and exposed within small impact craters and troughs are flat lying sedimentary rocks these rocks are finely laminated are rich in sulfur and contain abundant sulfate salts small scale cross lamination in some locations provides evidence for deposition in flowing liquid water we interpret the rocks to be a mixture of chemical and siliciclastic sediments formed by episodic inundation by shallow surface water followed by evaporation exposure and desiccation hematite rich spherules are embedded in the rock and eroding from them we interpret these spherules to be concretions formed by postdepositional diagenesis again involving liquid water

geology geography and humans battle for dominance over the delivery of fluvial sediment to the coastal ocean abstract sediment flux to the coastal zone is conditioned by geomorphic and tectonic influences basin area and relief geography temperature runoff geology lithology ice cover and human activities reservoir trapping soil erosion a new model termed bqart in recognition of those factors accounts for these varied influences when applied to a database of 488 rivers the bqart model showed no ensemble over or underprediction had a bias of just 3 across six orders of magnitude in observational values and accounted for 96 of the between river variation in the long term 30 years sediment load or yield of these rivers the geographical range of the 488 rivers covers 63 of the global land surface and is highly representative of global geology climate and socioeconomic conditions based strictly on geological parameters basin area relief lithology ice erosion 65 of the between river sediment load is explained climatic factors precipitation and temperature account for an additi

sediment deposition in an alaskan fjord controls on the formation and preservation of sedimentary structures in icy bay abstract the formation of sedimentary strata was examined within a temperate fjord icy bay alaska radioisotopes 234th 210pb were used to develop a chronology of sediment deposition and accumulation from cores collected in august 1994 and july 1995 sedimentary structures were described and attributed to specific sedimentologic oceanographic and glacial processes annual sedimentologic processes were summarized by examination of sedimentary structures seen in x radiographs and by developing a monthly chronology using 234th during the months of may july 1995 deposition of sediment varied from highly non steady state at ice proximal stations to steady state at a mid fjord station deposition rates systematically decreased down fjord from 0 3 cm d 1 to 0 02 cm d 1 laminated muds were forming daily in icy bay at upper fjord stations and bioturbated sediments dominated in the lower fjord diamicton beds containing biogenic structures were formed in icy bay during the winter when sediment deposition rates were lower sediment profiles of 210pb activity indicate a non steady state flux of particulate 210pb to the seabed precluding measurement of decadal scale sediment accumulation rates using this isotope the dynamic relationship between deposition rates distance from the glacier terminus and the production of sedimentary structures were explored by examining longer cores kasten piston that contain the history of ice recession in icy bay over the past few decades these cores display changes in strata formation resulting from progressive glacial retreat as indicated by down core increases in the percentage of core length represented by mud layers laminated sediments and the relative concentration of sand to silt

contemporaneous deposition of phyllosilicates and sulfates using australian acidic saline lake deposits to describe geochemical variability on mars 1 studies of the origin of the martian sulfate and phyllosilicate deposits have led to the hypothesis that there was a marked global scale change in the mars environment from circum neutral ph aqueous alteration in the noachian to an acidic evaporitic system in the late noachian to hesperian however terrestrial studies suggest that two different geochemical systems need not be invoked to explain such geochemical variation western australian acidic playa lakes have large ph differences separated vertically and laterally by only a few tens of meters demonstrating how highly variable chemistries can coexist over short distances in natural environments we suggest diverse and variable martian aqueous environments where the coetaneous formation of phyllosilicates and sulfates at the australian sites are analogs for regions where phyllosilicates and sulfates coexist on mars in these systems fe and alkali earth phyllosilicates represent deep facies associated with upwelling neutral to alkaline groundwater whereas aluminous phyllosilicates and sulfates represent near surface evaporitic facies formed from more acidic brines

an in situ record of major environmental transitions on early mars at northeast syrtis major the noachian hesperian transition on mars was a period marked by changes in volcanic processes and styles of aqueous alteration understanding the timing and nature of environmental change requires the exploration of units recording both sets of processes herein we report the compositional stratigraphy of distinctive noachian to hesperian units along the northeastern margin of the syrtis major volcanic flows a layered polyhydrated sulfate bearing unit with jarosite ridges has been discovered beneath the syrtis major lava flows and above the regionally extensive stratigraphy of noachian plains units reported previously sequential clay carbonate and sulfate bearing units formed in situ and record a transition from alkaline ph to acidic ph waters the sequence is chronologically bookended by the isidis impact and syrtis major flows and is one of the most temporally constrained and well preserved stratigraphic sections from early mars available for landed exploration

late holocene environment and climatic changes in ameralik fjord southwest greenland evidence from the sedimentary record sedimentological and geochemical xrf data together with information from diatom and benthic foraminiferal records of a 3 5 m long gravity core from ameralik fjord southern west greenland is used for reconstructing late holocene environmental changes in this area the changes are linked to large scale north atlantic ocean and climate variability ams 14c dating of benthic foraminifera indicates that the sediment core records the last 4400 years and covers the termination of the holocene thermal maximum htm the late htm 4 4 3 2 ka bp is characterized by high accumulation rates of fine silty sediments related to strong meltwater discharge from the inland ice the htm benthic foraminiferal fauna demonstrates the presence of well ventilated saline bottom water originating from inflow of subsurface west greenland current water of atlantic irminger sea origin the hydrographic conditions were further characterized by limited sea ice probably related to a mild and relatively windy winter climate af

hydrous minerals on mars as seen by the crism and omega imaging spectrometers updated global view 1 the surface of mars has preserved the record of early environments in which its basaltic crust was altered by liquid water these aqueous environments have survived in the form of hydrological morphologies and alteration minerals including clays and hydrated salts because these minerals probe on earth aqueous environments compatible with biotic activity understanding their formation processes on mars is of great exobiological relevance and also offers insight into earth s now erased ancient water environments using remote sensing we conducted a large scale investigation of the distribution composition age and geomorphic settings of hydrous minerals on mars providing a sharpened global view of the early aqueous environments and their evolution with time aqueous alteration seems to have produced clays on a planetary scale but these are found to be restricted to the oldest observable terrains on mars 4 gyr however very diverse aqueous environments have also been found which suggest widespread complex aqueous settings from the surface to kilometric depths and spanning over 1 gyr by building a robust statistical sample of detections the global trends inferred here attempt to provide a broad view of our current understanding of hydrous minerals on mars and provide context for more localized in depth analyses collectively these trends suggest that at least transient conditions have existed on mars which may have been favorable for pre biotic to biotic activity

significance of early diagenetic water rock interactions in a modern marine siliciclastic evaporite environment salina ometepec baja california although marine brines are a significant component of pore waters in sedimentary basins there are few geochemical studies of modern analogues of such systems especially in siliciclastic settings for these reasons we chose the evaporite associated siliciclastic sediments deposited in the salt flats of the salina ometepec baja california for an integrated investigation of sediment pore water and overlying brine geochemistry here the detrital components include quartz k feldspar plagioclase chlorite biotite and smectite and authigenic minerals are dominated by halite gypsum and k rich magnesium smectite thermal and saline stresses on the sediments of the salina ometepec keep both organic and inorganic carbon concentrations in the sediments unusually low relative to other coastal marine environments sediment pore waters exhibit little microbial sulfate reduction and dissolved inorganic c contents are also very low as a result we did not observe carbonate and sulfide mineral authigenesis in the salina ometepec sediments instead pore water geochemical evolution is largely controlled by evaporative concentration of seawater evaporite mineral dissolution and recrystallization and diagenetic alteration of detrital aluminosilicates evaporite mineral recycling affects the compositional evolution of surficial brines even before they infiltrate the sediment specifically na and cl concentrations are increased owing to halite dissolution we see significant br enrichment relative to expected seawater evaporation trends in near surface pore water secondary to dissolution of k and mg salts because bacterial sulfate reduction is inhibited in the salina ometepec sediments sulfate concentrations are more accurate indicators of the degree of evaporation than br a usually conservative element during geochemical reactions pore waters exhibit down core increases in dissolved mg2 k and batchmode documentclass fleqn 10pt legalpaper article usepackage amssymb usepackage amsfonts usepackage amsmath pagestyle empty begin document h 4 sio 4 0 end document over the upper 1 m authigenic k rich mg smectite formation is promoted by the concurrent processes of brine concentration selective dissolution of k and mg bearing salts and dissolution of detrital aluminosilicates pore waters at a depth of 1 m have 87sr 86sr ratios that require input of sr that is less radiogenic than that of gulf of california seawater this sr is likely derived from weathering of detrital aluminosilicates from nearby volcaniclastic sources these results show that significant chemical interactions among marine brines evaporite minerals and detrital aluminosilicates can occur relatively soon after sedimentation

elemental geochemistry of sedimentary rocks at yellowknife bay gale crater mars sedimentary rocks examined by the curiosity rover at yellowknife bay mars were derived from sources that evolved from an approximately average martian crustal composition to one influenced by alkaline basalts no evidence of chemical weathering is preserved indicating arid possibly cold paleoclimates and rapid erosion and deposition the absence of predicted geochemical variations indicates that magnetite and phyllosilicates formed by diagenesis under low temperature circumneutral ph rock dominated aqueous conditions analyses of diagenetic features including concretions raised ridges and fractures at high spatial resolution indicate that they are composed of iron and halogen rich components magnesium iron chlorine rich components and hydrated calcium sulfates respectively composition of a cross cutting dike like feature is consistent with sedimentary intrusion the geochemistry of these sedimentary rocks provides further evidence for diverse depositional and diagenetic sedimentary environments during the early history of mars

late quaternary chronology and environments of square lake torngat mountains labrador sediment pollen and diatom records from square lake a small lake dammed by a segment of saglek moraine cover the period of deposition of and deglaciation from the saglek moraine the basal radiocarbon date 18 210 1900 years bp is on sediment contaminated by reworked pollen and is thus a maximum age however the date was measured on organic carbon recovered from glaciolacustrine couplets associated with deposition of the saglek moraine and thus establishes a late wisconsinan age for the saglek moraine vegetation on the ice free upland surrounding square lake at this time was a sparse tundra vegetation dominated by grasses and herbs the absence of diatoms indicates perennial lake ice cover a major transition is recorded by pollen and diatoms at 8 5 ka vegetation probably remained sparse tundra but birch and willow may have arrived in the area by 8 ka diatoms are first dominated by alkaliphil species reflecting continued influence of glaciolacustrine sedimentation an abrupt change in depos

the effect of sediment mixing on pb 210 accumulation rates for the washington continental shelf abstract nine cores from the washington continental shelf were examined by radiochemical techniques in order to evaluate the effect of mixing on the calculation of sediment accumulation rates from pb 210 profiles th 234 profiles indicate mixing coefficients of 140 cm 2 yr 1 for the seabed offshore from the columbia river and 47 cm 2 yr 1 for the seabed of the mid shelf silt deposit 75 km north of the columbia river these large mixing coefficients demonstrate that particles can penetrate to the base of the intensely mixed surface layer 10 cm within one year after emplacement at the seabed surface observed depths of cs 137 penetration within the seabed are compared with depths predicted from the surface mixed layer thickness and the pb 210 accumulation rate the observed and predicted depths agree well at all but one station at this station a combination of th 234 co 60 pb 210 and cs 137 profiles suggests that active mixing occurs below the intensely mixed surface layer the agreement of pb 210 and cs 137 data at the other stations however indicates a general absence of deep mixing on the washington shelf thus the apparent accumulation rates calculated from pb 210 profiles below the intensely mixed surface layer on the washington shelf generally reflect the true rates of sediment accumulation

mineralogy of a mudstone at yellowknife bay gale crater mars sedimentary rocks at yellowknife bay gale crater on mars include mudstone sampled by the curiosity rover the samples john klein and cumberland contain detrital basaltic minerals calcium sulfates iron oxide or hydroxides iron sulfides amorphous material and trioctahedral smectites the john klein smectite has basal spacing of similar to 10 angstroms indicating little interlayer hydration the cumberland smectite has basal spacing at both similar to 13 2 and similar to 10 angstroms the larger spacing suggests a partially chloritized interlayer or interlayer magnesium or calcium facilitating h2o retention basaltic minerals in the mudstone are similar to those in nearby eolian deposits however the mudstone has far less fe forsterite possibly lost with formation of smectite plus magnetite late noachian early hesperian or younger age indicates that clay mineral formation on mars extended beyond noachian time

holocene climate history of the nunatsiavut northern labrador canada established from pollen and dinoflagellate cyst assemblages covering the past 7000 years this study documents the past 7000 years of holocene climatic history for labrador and nunatsiavut using a sedimentary sequence of more than 8 m retrieved in nachvak fjord one of the northernmost fjords of nunatsiavut using a multi proxy approach combining a solid accelerator mass spectrometry ams 14c chronology and the fossil assemblages of pollen grains and dinoflagellate cysts dinocysts we were able to compare terrestrial and marine records in an effort to obtain a better understanding of the mid to late holocene climate history of the nunatsiavut records begin at the end of the deglaciation and showed a general delay in the sequence of climate events which followed both in terrestrial and marine realms the presence of pentapharsodinium dalei in great abundance in nachvak fjord revealed a strong influence of the north atlantic ocean and the labrador sea until 3000 yr bp afterward its rather fast disappearance marked the increased influence of arctic waters the last 1000 years show clim

239 240pu and excess210pb inventories along the shelf and slope of the northeast u s a abstract sedimentary pu and excess 210 pb inventory data are examined from a large number of sites along the u s north atlantic shelf and slope from these data an estimate can be made of the magnitude and location of pu and 210 pb accumulation in this region a major feature of the data is a decrease in the pu and 210 pb inventories with water depth which appears to reflect a decrease in the net scavenging of these elements off shore when pu and 210 pb inventories are summed over water depths less than 4000 m in the north atlantic shelf and slope region the sediments can account for 24 8 of the expected pu and 83 15 of the expected 210 pb inputs at water depths greater than 4000 m in this region we find a greater deficiency in the measured inventories of both 210 pb and pu which cannot be accounted for in the shallower sediments this suggests that the northwest atlantic continental margin is not a major site of pu or 210 pb removal and storage when compared to atmospheric in situ and lateral inputs of these radionuclides