how accurate are 234th measurements in seawater based on the mno2 impregnated cartridge technique in the past decade a mno2 impregnated cartridge technique has been widely used to extract 234th from seawater one of the inherent assumptions associated with this technique is that all th species in the dissolved phase are subject to extraction by the mno2 cartridges in this study an intercalibration between the cartridge technique and a small volume mno2 coprecipitation technique was carried out to test this assumption we demonstrated that the collection efficiency for 234th could be substantially overestimated by the mno2 cartridge technique this may be the result of organic complexation of a significant portion of 234th in seawater causing this fraction of th to pass through the mno2 cartridges the overestimate in collection efficiency may explain the deep water 234th deficit observed in some oceanographic settings e g the gulf of mexico the middle atlantic bight and the gulf of maine sensitivity tests show that using the cartridge technique can yield 234th based particulate organic carbon export rates that are overestimated by factors of up to 10 furthermore the frequent observed disagreements between th fluxes recorded by shallow sediment traps and estimated using the cartridge method may be ascribed at least partially to this methodological issue

reply to comment by chin chang hung et al on how accurate are 234th measurements in seawater based on the mno2 impregnated cartridge technique

small scale modeling of onshore seismic experiment a tool to validate numerical modeling and seismic imaging methods the seismic imaging methods currently in the development stage need to be tested for experimental validation under controlled conditions yet natural media are very complex and moreover the parameters along the measurement profile prove difficult to evaluate independently of the seismic method itself to satisfy this need the ultrasonic measurement laboratory musc presented in this research has been devised to experimentally model seismic field measurements by using reduced scale models this facility is composed of small scale models of the underground an optical table with two moving arms a laser interferometer and adapted piezoelectric transducers used as the seismic sources the source system has been adapted to simulate the behavior of a point surface seismic source this is essential to reproduce the spatial energy distribution of a surface seismic source and supersedes the sources used in the past for other reduced scale seismic experimental models the comparisons of experimental data coll

ultrasonic velocity and anisotropy of hydrocarbon source rocks an experimental study of the physical properties of black kerogen rich shales also including maturation analysis scanning electron microscope sem observations and physical modeling revealed fairly peculiar petrophysical parameters specifically these rocks have very low porosity and density but most importantly both p and s ultrasonic velocities normal to bedding are extremely low whereas they are much higher parallel to bedding giving rise to a strong anisotropy even at high confining pressures we found that these parameters primarily reflect kerogen content microstructure and maturation level of these rocks we found also that microcracks inferred from ultrasonic velocity measurements occur only in mature shales these microcracks are parallel to the bedding plane and further enhance strong intrinsic anisotropy notably at low effective pressure our results show that on a small scale kerogen rich shales are transversely isotropic rocks and can be effectively modeled using the thin laye

a model for seismic velocity and attenuation in petroleum source rocks petroleum source rock is modeled as a viscoelastic transversely isotropic medium composed of illite smectite and organic matter the wave velocities and attenuation of petroleum source rocks are obtained as a function of excess pore pressure initial kerogen content and water saturation the model generalizes a previous approach based on a pure elastic formulation of backus averaging and introduces the pressure effect and the presence of fluids oil and water the model allows the simulation of different maturation levels induced by pore pressure changes caused by the conversion of kerogen to oil the higher the oil saturation the higher the maturation level assuming that the source rock has a very low permeability the excess pore pressure can be calculated as a function of the conversion factor then the bulk modulus and density of the kerogen oil mixture are obtained with the kuster and toks oz model assuming that oil is the inclusion in a kerogen matrix finally backus averaging of this mixture with the illite smectite layers gives the complex stiffnesses of the transversely isotropic and anelastic medium computed p and s velocities and quality factors parallel to bedding are higher than those normal to bedding with attenuation anisotropy higher than stiffness anisotropy in particular for the north sea kimmeridge shale and at maximum anisotropy p and s parallel velocities are approximately 0 7 km s higher than the corresponding p and s normal velocities the maximum attenuation and stiffness anisotropies are obtained for 18 and 30 volumetric kerogen content respectively both velocities and quality factors decrease with increasing kerogen content at a given pore pressure the decrease in wave velocity is 2 km s for p waves and 1 km s for s waves when kerogen increases from zero to 100 moreover anisotropy increases and velocities decrease with increasing pore pressure i e with higher kerogento oil conversion finally the presence of water affects the normal bedding velocity i e higher water saturation implies lower velocities

234th 238u disequilibria within the california current1 profiles of dissolved and particulate sup 234 th were determined at several stations within the california current modeling of the disequilibria between the sup 234 th and sup 238 u within the surface waters provides for estimates of the residence time of dissolved thorium with respect to particle scavenging the particle residence time and the particulate sup 234 th flux exiting the surface layer the model derived first order scavenging rate constant for dissolved thorium is observed to be proportional to the rate of primary production particle residence times seem to be governed by the rate of zooplankton grazing and the types of zooplankton present model derived particulate sup 234 th fluxes are in good agreement with direct measurements by sediment traps

seismic wave attenuation in carbonates 1 the effect of pore fluids on seismic wave attenuation in carbonate rocks is important for interpreting remote sensing observations of carbonate reservoirs undergoing enhanced oil recovery here we measure the elastic moduli and attenuation in the laboratory for five carbonate samples with 20 to 30 porosity and permeability between 0 03 and 58 1 mdarcy contrary to most observations in sandstones bulk compressibility losses dominate over shear wave losses for dry samples and samples fully saturated with either liquid butane or brine this observation holds for four out of five samples at seismic 10 1000 hz and ultrasonic frequencies 0 8 mhz and reservoir pressures attenuation modeled from the modulus data using cole cole relations agrees in that the bulk losses are greater than the shear losses on average attenuation increases by 250 when brine substitutes a light hydrocarbon in these carbonate rocks for some of our samples attenuation is frequency dependent but in the typical exploration frequency range 10 100 hz attenuation is practically constant for the measured samples

small phytoplankton drive high summertime carbon and nutrient export in the gulf of california and eastern tropical north pacific summertime carbon nitrogen and biogenic silica export was examined using 234th 238u disequilibria combined with free floating sediment traps and fine scale water column sampling with in situ pumps isp within the eastern tropical north pacific and the gulf of california fine scale isp sampling provides evidence that in this system particulate carbon pc and particulate nitrogen pn concentrations were more rapidly attenuated relative to 234th activities in small particles compared to large particles converging to 1 5 mol dpm 1 by 100 m comparison of elemental particle composition coupled with particle size distribution analysis suggests that small particles are major contributors to particle flux while absolute pc and pn export rates were dependent on the method used to obtain the element 234th ratio regional trends were consistent across measurement techniques the highest c fixation rates were associated with diatom dominated surface waters yet the highest export efficiencies occurred in picoplankton dominated surface waters where relative concentrations of diazotrophs were also elevated our results add to the increasing body of literature that picoplankton and diazotroph dominated food webs in subtropical regions can be characterized by enhanced export efficiencies relative to food webs dominated by larger phytoplankton e g diatoms in low productivity pico nanoplankton dominated regions where small particles are major contributors to particle export findings from this region are compared globally and provide insights into the efficiency of downward particle transport of carbon and associated nutrients in a warmer ocean where picoplankton and diazotrophs may dominate therefore we argue the necessity of collecting multiple particle sizes used to convert 234th fluxes into carbon or other elemental fluxes including 50 m since they can play an important role in vertical fluxes especially in oligotrophic environments our results further underscore the necessity of using multiple techniques to quantify particle flux given the uncertainties associated with each collection method

ultrasonic velocities in cretaceous shales from the williston basin compressional and shear wave velocities were measured in the laboratory from 1 bar to 4 kbar confining pressure for wet undrained samples of cretaceous shales from depths of 3200 and 5000 ft in the williston basin north dakota these shales behave as transversely isotropic elastic media the plane of circular symmetry coinciding with the bedding plane for compressional waves the velocity is higher for propagation in the bedding plane than at right angles to it and the anisotropy is greater for the 5000 ft shale for shear waves the sh wave perpendicular to bedding and the sv wave parallel to bedding propagate with the same speed which is about 25 percent lower than that for the sh wave parallel to bedding in general compressional and shear velocities are higher for the indurated 5000 ft shale than for the friable 3200 ft shale all velocities increase with in increasing confining pressure to 4 kbar the 3200 ft shale exhibits velocity hysteresis as a function of pressure whereas this effect is a

export flux of poc in the main stream of the kuroshio 1 particulate organic carbon poc export fluxes were measured using both a drifting sediment trap and a 234th approach ratio of poc 234th multiple 234th flux in the main steam of the kuroshio in august 2006 the poc fluxes measured by sediment traps and the 234th approach at 65 90 120 and 140 m ranged from 20 to 54 mg m 2 d 1 and 26 to 67 mg m 2 d 1 respectively the results show that using poc 234th ratios in intermediate particles 10 53 m and sinking particles is more comparable to the poc flux measured by sediment traps therefore the poc export fluxes within the euphotic zone estimated by sediment trap and 234th approaches are complementary methods for measuring poc flux in the kuroshio

234th balance and implications for seasonal particle retention in the eastern bering sea th abstract as part of the bering ecosystem study bering sea integrated ecosystem research program best bsierp distributions of 234 th in the water column and sediments were measured at approximately 60 stations over the shelf and slope oceanic regions of the eastern bering sea during spring and summer of 2009 and 2010 during this study period the inventory of sediment excess 234 th 234 thxs on the shelf was determined to be 1 3 of the total 234 th deficit in the overlying water column the average focusing factor ffth sediment 234 thxs water column 234 th deficit was 0 3470 23 in addition the export flux of 234 th from the shelf to the slope oceanic region was determined to be on average 30 of the total production of 234 th throughout the shelf taken together these results indicate that 234 th and associated particles are largely retained on the shelf and that shelf sediments represent a sink for particles in contrast the ffth in the slope oceanic region was higher averaging 1 5271 34 the higher ffth at the slope is attributed primarily to enhanced scavenging removal and sediment deposition of 234 th associated with periods of high biogenic particle flux at the marginal ice zone during the spring sea ice retreat a more general conclusion is that the ocean margin of the eastern bering sea may serve as an accumulation area for particles and associated reactive chemicals

the impact of marginal ice zone processes on the distribution of 21opb 21opo and 234th and implications for new production in the bellingshausen sea antarctica abstract the vertical distributions of 21opb 210po and 234th in both dissolved and particulate phases of seawater were measured at five stations along the 85 w meridian in the bellingshausen sea antarctica sea ice conditions during the expedition ranged from fully ice covered fast ice to open water away from the marginal ice zone concurrent primary productivity and algal chlorophyll measurements revealed a band of high productivity at approximately 67 30 s which remained in a rather static location during ice melt back along the transect a progressive increase in removal scavenging and sinking of 210pb 210po and 234th occurred towards the north open water conditions application of a simple irreversible scavenging model and particulate organic carbon and organic nitrogen to radionuclide ratios measured on suspended particulate matter allows the calculation of export production for this region under fast ice conditions some removal of phytodetritus from the euphotic zone was observed 1 2 mgc m 2 day 1 representing a low proportion of the primary production f ratio of 0 02 near the antarctic continental margin upwelling of regenerated dissolved 210po was found at the open water site near the algal band new production had risen to 27 252 mgc m 2 day 1 but a greater proportion of the original primary production was removed by sinking detritus f ratio of 0 03 0 33 comparison of 210po and 234th as tracers of of export production indicates considerable differences with 210po yielding rather lower rates of export flux compared to 234th radionuclide estimates of new production are significantly greater than those obtained by traditional sediment trap methods this may be due to the dynamic nature short duration and spatial variability of algal growth in the southern ocean

vertical and horizontal particle transport in the coastal waters of a large lake an assessment by sediment trap and thorium 234 measurements 1 the horizontal and vertical flux of particulate material in the nearshore of southern lake michigan 0 40 m was estimated with the naturally occurring radionuclide 234th horizontal fluxes of 234th supplemented apparent vertical fluxes of 234th in the water column based on local 234th 238u disequilibria by a factor of 7 14 reinforcing the importance of lateral transport in coastal environments calculated onshore transport of particulate material across the 40 m isobath was as high as 1 1 106 kg km 1 d 1 and exceeds estimates of terrigenous riverine and bluff erosion loading estimates of onshore flux of organic carbon exceeded areal primary productivity by as much as 300 and should be considered in nearshore carbon budgets bottom tethered sediment traps placed 5 m above the bottom measured sedimentation rates that were 1 order of magnitude lower than 234th derived mass fluxes from the water column and 2 orders of magnitude lower than 234th derived mass fluxes to the lakebed we ascribe this difference to under collecting by the sediment trap either because of trap hydrodynamics or flux occurring below the trap capture plane cross shore fluxes showed a periodicity of 4 days and correlated strongly with a topographic vorticity wave that is present throughout the year in southern lake michigan the impact of this wave as a driver of bidirectional cross shore flux on biogeochemical cycling and both nearshore and offshore food webs has not yet been explicitly considered

does 234th 238u disequilibrium provide an accurate record of the export flux of particulate organic carbon from the upper ocean the magnitude of the flux of biogenic particulate organic carbon poc exported from the surface waters of the world ocean and remineralized at depth is critical to constraining models of the global carbon cycle yet remains controversial the use of upper ocean sediment traps is still one of the primary tools for determining this export flux although trap fluxes have been shown to vary significantly because of hydrodynamic and sample collection biases over the past decade 234 th increasingly has been used as a tracer to estimate poc export from the euphotic zone by multiplying the depth integrated 234 th flux by the poc 234 th ratio of sinking particles the accuracy of this technique is highly dependent on the natural variability in the poc 234 th ratio and 234 th flux yet the significance of this variability to estimates of poc export remains uncertain based on an analysis of new 234 th and poc data from the labrador sea and a review of 25 previous independent field studies we report that poc export fluxes can vary 2 10 times or more solely because of variability in the poc 234 th ratio and procedures used to estimate the 234 th flux recommended improvements include studies of the biological chemical and physical mechanisms controlling 234 th organic matter interactions in seawater detailed comparisons of poc 234 th ratios in size fractionated and sediment trap material increased spatial and temporal sampling density of 234 th and more standardized procedures to calculate the 234 th export flux

noncontacting benchtop measurements of the elastic properties of shales we evaluated a laser based noncontacting method to measure the elastic anisotropy of horizontal shale cores whereas conventional transducer data contained an ambiguity between phase and group velocity measurements small laser source and receiver footprints on typical core samples ensured group velocity information in our laboratory measurements with a single dense acquisition of group velocity versus group angle on a horizontal core we estimated the elastic constants c11 c33 and c55 directly from ultrasonic waveforms and c13 from a least squares fit of modeled to measured group velocities the observed significant p wave velocity and attenuation anisotropy in these dry shales were almost surely exaggerated by delamination of clay platelets and microfracturing but provided an illustration of the new laboratory measurement technique although challenges lay ahead to measure preserved shales at in situ conditions in the lab we evaluated the fundamental advantages of the proposed method over conventional transducer measurements

234th in surface waters distribution of particle export flux across the antarctic circumpolar current and in the weddell sea during the geotraces expedition zero and drake abstract as part of the geotraces polarstern expedition antxxiv 3 zero and drake we have measured the vertical distribution of 234th on sections through the antarctic circumpolar current along the zero meridian and in drake passage and on an ew section through the weddell sea steady state export fluxes of 234th from the upper 100 m derived from the depletion of 234th with respect to its parent 238u ranged from 621 105 to 1773 90 dpm m 2 d 1 this 234th flux was converted into an export flux of organic carbon ranging from 3 1 to 13 2 mmol c m 2 d 1 2 1 9 0 mmol c m 2 d 1 using poc 234th ratio of bulk respectively 50 m suspended particles at the export depth 100 m non steady state fluxes assuming zero flux under ice cover were up to 23 higher in addition particulate and dissolved 234th were measured underway in high resolution in the surface water with a semi automated procedure particulate 234th in surface waters is inversely correlated with light transmission and pco2 and positively with fluorescence and optical backscatter and is interpreted as a proxy for algal biomass high resolution underway mapping of particulate and dissolved 234th in surface water shows clearly where trace elements are absorbed by plankton and where they are exported to depth quantitative determination of the export flux requires the full 234th profile since surface depletion and export flux become decoupled through changes in wind mixed layer depth and in contribution to export from subsurface layers in a zone of very low algal abundance 54 58 s at the zero meridian confirmed by satellite chl a data the lowest carbon export of the acc was observed allowing fe and mn to maintain their highest surface concentrations an ice edge bloom that had developed in december january in the zone 60 65 s as studied during the previous leg had caused a high export flux at 64 5 s when we visited the area 2 months later february march the ice edge bloom had then shifted south to 65 69 s evident from uptake of co2 and dissolved fe mn and 234th without causing export yet in this way the parallel analysis of 234th can help to explain the scavenging behavior of other trace elements

elastic anisotropy of shales accompanying the resource potential of gas shales is a new interest in understanding the physical and petrophysical properties of shales shale by geochemical or stratigraphic measures is arguably the most common lithology encountered in sedimentary basins despite this shales remain little studied while engineers and explorationists focused on conventional reservoirs geophysicists did this knowing full well that often a reflection coefficient from a reservoir was controlled by the shale properties of the cap rock we compensated for this ignorance by arguing that shales are deposited in deepwater environments in which lateral and vertical changes are slow and therefore inconsequential we further compounded this ignorance by assuming that the shales were isotropic an example of the consequences of this ignorance was clearly documented by margesson and sondergeld 1999 engineers share culpability for this ignorance too since most of the drilling problems occur in shales and most of the lithologies d

geochemical signature related to lipid biomarkers of anmes in gas hydrate bearing sediments in the ulleung basin east sea korea abstract the emission of methane as a greenhouse gas is controlled by the anaerobic oxidation of methane aom which plays an important role in the biogeochemical methane cycle during the second ulleung basin gas hydrate drilling expedition ubgh2 the distribution of lipid biomarkers and their compound specific stable carbon isotope ratios related to methane were investigated in venting and non venting sites ubgh2 3 ubgh2 10 of gas hydrate bearing sediments in the ulleung basin the objective of this study was to understand the microbial signatures related to methane cycling in organic rich sediment in a marginal sea east sea japan sea of the western north pacific the concentrations of methane related specific biomarkers archaeol and sn 2 hydroxyarchaeol at the sulphate methane transition zone smtz sediment depth in ubgh2 3 1 2 mbsf in ubgh2 10 6 8 mbsf are typically higher than in other sediment sections and their 13 c valuesare apparently depleted 73 3 to 102 7 in the ubgh2 3 and ubgh2 10 study sites however the 13 c values of archaeol and sn 2 hydroxyarchaeol between 59 6 and 66 5 are not depleted with the increased methane concentration in the sediments below the smtz in ubgh2 3 compared to the 13 c values about 60 of in situ methane this suggests that methane production processes should be dominant in the deeper sediment sections 2 7 3 8 mbsf rather than methane consumption by anaerobic methanotrophs anmes at the corresponding sediment depths there were also higher 13 c values 47 to 32 for archaeol and sn 2 hydroxyarchaeol in the 3 6 mbsf sections at ubgh2 10 suggesting the prevalence of methanogenic activities however the 13 c values 89 0 to 92 2 of archaeol and sn 2 hydroxyarchaeol were unexpectedly depleted in the deeper sediment section 5 2 mbsf of the venting site ubgh2 3 indicating that the past aom occurred under low sulphate concentrations in the corresponding pore water this study used the biomarker ratio sn 2 hydroxyarchaeol archaeol of archaea as a tool to demonstrate the different anme communities which was supported by 16s rrna analysis in the sediments of venting and non venting sites ubgh2 3 ubgh2 10 consequently the biochemical signatures of methanotrophic and methanogenic activity were found at varying sediment depths at both sites

a three dimensional time dependent approach to calibrating sediment trap fluxes we conducted an experiment to test explicitly the accuracy of upper ocean sediment trap fluxes using the particle reactive radionuclide 234th t1 2 24 1 days two independent vertex style multitrap arrays were used for collection of sinking particles at 95 m and 97 m depths over a four day period in may 1992 at the u s joint global ocean flux study bermuda atlantic time series study bats site samples for total 234th were collected every 8 m between the surface and 96 m and immediately combined for analysis to obtain the vertically integrated activity of 234th we collected a total of 27 samples over the four day period the234th samples were collected daily at each of the two traps and every other day on a 6 6 km grid to characterize the entire source region for particles collected in the traps in situ flow sensors at one trap array indicated low horizontal shear at the trap mouth 5 10 cm s compared to normal values at bats the predicted 234th flux from the watercolumn profiles was not significantly different from zero 30 140 disintegrations per minute m2 d the measured trap 234th flux at both arrays was significantly higher 290 15 dpm m2 d we hypothesize that upper ocean traps at bermuda may overcollect during low flux periods and undercollect during high flux periods thus recording a biased signal of the true particle flux

seismic anisotropy of shales the seismic properties and preferred clay mineral orientation of a suite of shales are investigated using laboratory velocity measurements as a function of confining pressure x ray diffraction techniques and electron microprobe backscatter bse imaging the velocity measurements indicate that these shales are transversely isotropic with the main symmetry axis perpendicular to bedding anisotropy at elevated pressures caused mainly by preferred orientation of clays illite parallel to bedding ranges from 20 vp and 19 vs for a sample of new albany shale to 30 vp and 35 vs for a sample of chattanooga shale the degree of clay mineral alignment in the shales is constrained by orientation indices produced using simple x ray diffraction techniques a strong positive correlation is found between the degree of preferred orientation as expressed in the orientation indices and seismic anisotropy bse images of the shale fabrics confirm in a qualitative manner the results of the x ray study to investigate wave propagation in the shales elastic constants of each sample are calculated and used to produce phase and group wave velocity surfaces which describe variation in velocity as a function of angle to the bedding normal the calculated velocity surfaces constrained by independent velocity measurements display a lack of shear wave splitting at near normal incidence in even the most anisotropic shales for the highly anisotropic chattanooga shales group velocity surfaces differ significantly from corresponding phase velocity surfaces

the mechanism for antarctic intermediate water renewal in a world ocean model abstract realistic representation of the low salinity tongue of antarctic intermediate water aaiw has been achieved in a coarse resolution ocean general circulation model the authors find that this water mass is not generated by direct subduction of surface water near the polar front instead the renewal process is concentrated in the southeast pacific ocean off southern chile the outflow of the east australian current progressively cools by heat loss to the atmosphere and freshens by assimilation of polar water carried north by the surface ekman drift during its slow movement across the south pacific toward the aaiw formation zone further deep warm advection near chile enables more convective overturn resulting in very deep mixed layers from which aaiw is fed into the south pacific and also into the malvinas current along with this isolated region of aaiw renewal the model relies on alongisopycnal mixing of fresh surface water from the polar front to capture a realistic circumpolar tongue

234th in different size classes of sediment trap collected particles from the northwestern pacific ocean abstract 234 th a surface area specific particle reactive radionuclide has been used to estimate particulate organic carbon poc export fluxes based on the poc 234 th ratio of sinking particles and the 234 th flux in the ocean the poc 234 th ratios from large particles 50 m are conventionally considered to represent sinking particles collected by sediment traps but this assumption has not been thoroughly tested more recently hung and gong 2010 separated sinking particles from the northern south china sea where diatoms are the most dominant group using different nitex screens and found that small 234 th and poc flux however the size distribution of sinking particles has seldom been measured in picoplankton dominated oligotrophic and upwelling conditions here we used nitex screens to separate sinking particles in oligotrophic and upwelling regions additionally images of selected bulk sinking particles not subject to sequential filtration were directly taken by scanning electron microscopy sem to determine the size distribution of sinking particles within the trap collected 234 th pool in the upwelling area the 1 10 and 10 50 m fractions had on average the highest amounts of 234 th while poc did not show significant variations among the different size fractions in the oligotrophic region the 10 50 and 1 10 m fractions had on average the highest amounts of 234 th while the 150 and 10 50 m had elevated shares of poc results thus demonstrate that 234 th was mainly carried by the smaller 234 th flux can be a major fraction of the total sinking flux of this isotope and thus particles smaller than 50 m cannot be ignored because the poc 234 th ratio that is often used is that of large 50 m particles obtained from pump systems not traps

detection of rapid deposition of sea ice rafted material to the arctic ocean benthos using the cosmogenic tracer 7be abstract during three icebreaker cruises in the arctic ocean under different sea ice conditions in 2002 undisturbed benthic surface sediments were collected and assayed for the presence of a short lived t1 2 53 d particle reactive cosmogenic radionuclide 7be that is solely derived from atmospheric deposition under largely ice covered conditions in may june 2002 we did not detect this radionuclide in benthic surface sediments despite significant inventories present in ice rafted snow on the overlying sea ice mean 86 8 bq m 2 32 0 sd n 9 during the july august 2002 shelf basin interactions sbi cruise aboard the uscgc healy and during a simultaneous cruise of the ccgs sir wilfrid laurier on the bering and chukchi shelf which occupied the same general region following retreat and dissolution of arctic ice cover the 7be present in this snow as well as surface deposition on to the sea ice free water surface was detected in many benthic surface sediments including some as deep as 945 m in barrow canyon inventories of 7be in sediments were as high 60 bq m 2 as the entire decay corrected inventory present earlier in some snow samples collected on the sea ice cover other deposition indicators such as the inventories of sediment chlorophyll sediment oxygen respiration rates and 234th derived export fluxes also showed post ice melt particle deposition and vertical transport but in most cases the 7be deposition was not tightly correlated with these other indicators suggesting that 7be sedimentation may not be controlled by the same processes our observations indicate that materials in sea ice including contaminants particulate organic and mineral matter originating from atmospheric deposition or entrained in continental shelf sediments and rafted onto sea ice can be rapidly transported to depth the re distribution of these materials as sea ice drifts and eventually melts has the potential for impacting arctic ocean biogeochemical cycles and contaminant concentrations in areas of the arctic remote from the original point of deposition

experimental laboratory determination of the dynamic elastic properties of wet drained shales the ultrasonic anisotropic elastic properties of drained saturated shales were measured as a function of confining pressure two shales were characterized in this study a jurassic outcrop shale retrieved under the sea in a saturated state and a kimmeridge clay shale cut from a north sea borehole both shales were highly anisotropic both texturally as revealed by scanning electron microscopy analysis and elastically as measured ultrasonically in the laboratory the strongest anisotropy was seen in the kimmeridge clay shale where up to 38 compressional wave anisotropy thomsen s parameter e and up to 58 shear wave anisotropy thomsen s parameter were observed in addition for both shales e and were found to decrease as a function of increasing confining pressure with the pore pressure drained to atmosphere while the anellipticity deviation of the slowness surfaces from ellipses was found to be positive and decreased as a function of increasing confining pressure accompanying these changes in elastic properties was a decrease in porosity with increasing confining pressure from 10 5 to 8 5 for the jurassic shale the decrease in overall anisotropy of the shales with increasing confining pressure was found to be consistent with theoretical modeling of shale properties where the shale anisotropy and anellipticity were predicted to decrease as a function of decreasing fluid filled porosity