tracing of water masses using a multi isotope approach in the southern indian ocean anthropogenic radionuclides 3 h 14 c and 129i stemmed from nuclear weapons tests were found in 1999 to be very abundant in the surface of the southern indian ocean comparable to those in the subtropical northwest pacific ocean the observed radionuclide variations with latitude longitude in the southern indian ocean are not due to deposition patterns of global fallout but due to transport of water masses from the western pacific through the indonesian seas and different water fronts present in the crozet basin of the indian ocean high radionuclide concentrations observed in the latitudinal belt of 20 40 s are associated with the indian ocean subtropical gyre which acts as a reservoir of radionuclides maintaining their high concentrations on a time scale of several decades 14 c data documents that the southern indian ocean is an important for sink of anthropogenic carbon the isotopic tracers reveal the evidence of the most intense surface gradients and presence of several water masses in the southern indian ocean which makes the region one of the most dynamic places of the world ocean

facies and facies architecture of paleogene floodplain deposits willwood formation bighorn basin wyoming usa abstract paleogene deposits of the willwood formation were analyzed in two areas of the bighorn basin to provide a better understanding of the facies and facies arrangement of floodplain deposits and the various processes that influence floodplain construction and facies variability despite similar facies and facies organization floodplain deposits in the two areas differ in grain size hydromorphy and maturity of the paleosols and scale and organization of ribbon sandstones in the avulsion deposits these differences appear to be controlled by basin position of the study areas and differences in avulsion between the areas two kinds of cumulative floodplain paleosols red and purple paleosols formed on overbank deposits the red paleosols were better drained and formed on less clay rich parent material intense mottling and iron oxide nodules indicate that the purple paleosols which formed on more clay rich parent material were poorly drained the grain size differences reflect basin position in particular distance from a local sediment source avulsion deposits are volumetrically important comprising about half of the floodplain deposits in both areas the avulsion deposits resemble the stage iii splays described by smith et al 1989 smith n d cross ia dufficy j p clough s r 1989 anatomy of an avulsion sedimentology 36 1 24 in terms of characteristics of their ribbon sandstones and the presence of thin sheet sandstones or siltstones paleosols that formed on the fine grained facies show morphologic differences interpreted as developmental differences and attributed to differing rates of avulsion in the two study areas this study shows that avulsion belt paleosols provide a key to understanding avulsion rate in the stratigraphic record other differences between the willwood avulsion deposits in the two areas and between these ancient deposits and the modern avulsion deposits described by smith et al may reflect 1 problems in clearly recognizing ancient avulsion deposits in the field and 2 sampling bias resulting from the areally restricted view provided by the stratigraphic record of an areally extensive modern depositional feature at the same time because exposures are three dimensional the willwood strata reveal aspects of the facies and facies arrangement of avulsion belts not readily observed in the modern ones

preliminary bounds on the expected postclosure performance of the yucca mountain repository site southern nevada on the basis of current data and understanding of site characteristics at yucca mountain the likely performance range of a mined repository for spent nuclear fuel can be calculated low flux through the unsaturated zone results in groundwater travel times to the water table that probably exceed 10 000 years and may exceed 100 000 years far longer than required by the nuclear regulatory commission nrc the low flux will also limit releases of waste from the waste packages probably to annual amounts less than one millionth of the mass of the waste inventory remaining 1000 years after repository closure the corresponding releases of curies would be well within the allowable releases set by the nrc geochemical retardation by sorption and diffusion will slow radionuclide movement relative to groundwater flow by factors of hundreds to thousands for many waste species in combination these site conditions provide a high degree of confidence that no releases to the accessible environment will occur during the first 10 000 years after repository closure the time period for which the environmental protection agency epa has set release limits carbon 14 technetium 99 iodine 129 and various nuclides of uranium sorb poorly on the tuffs along the flow paths and together with uranium daughter products will be the first radionuclides to arrive at the water table the total radioactivity produced by these and later arriving contaminants will remain far below the allowable releases even for periods of millions of years if expected flux conditions prevail if the flux is currently greater than the values inferred from the measured in situ moisture contents of the volcanic rocks or if it were to increase in the future fracture flow and attendant short flow times to the water table could occur even if rapid fracture flow were to occur release of wastes to the accessible environment would probably remain low with respect to the epa s limits because diffusion of radionuclides from the fractures into the rock matrix would ensure slow migration of most of the wastes through the sorbing matrix

a quasi synoptic view of the frontal circulation in the crozet basin during the antares 4 cruise abstract with the major objective of estimating the secondary vertical circulation a fine grid survey of hydrographic and current fields across the crozet basin frontal zone was made as a physical component of the multidisciplinary antares 4 cruise this frontal zone forms the boundary of the antarctic circumpolar current and the agulhas return current with the quasi permanent existence of strong eddy activity prior to any quantitative diagnosis of the vertical circulation from the fine grid data it is necessary to place the mesoscale circulation and its time variability of the survey area within the basin wide context we give a quasi synoptic view of the ambient frontal circulation during the cruise period using satellite derived chlorophyll concentrations and sea surface temperature particular emphasis is placed on evaluation of the degree of synopticity of our fine grid measurements by comparing mesoscale features on satellite images the limited survey area 1 5 latitude 2 longitude lies precisely within the southernmost and easternmost convergent zone of the two current systems cutting across mesoscale meanders having typical wavelengths of 400 km and periods of 4 months both these satellite images and topex poseidon sea surface height data indicate little temporal variability of the survey area during the 14 days of measurement although fortuitous this quasi steady state of circulation enables us to use the ensemble of fine grid data as a set of synoptic data for diagnosing the vertical circulation using quasi geostrophic dynamics preliminary analysis of the horizontal and vertical hydrographic structure of the fine grid hints at the existence of wave like cross frontal intrusions having a mean along front wavelength of about 30 km

internal tides and vertical mixing over the kerguelen plateau within the context of the natural iron fertilization study keops time series measurements of ctd and ladcp profiles at a site 50 6 s 72 e 528 m coinciding with an annual phytoplankton bloom over the kerguelen plateau were made during the january february 2005 keops cruise an important activity of highly nonlinear semidiurnal internal tides having peak to peak isopycnal displacements of up to 80 m is identified these internal tides appear to be a principal agent for promoting elevated vertical mixing indispensable for upward transfer of iron within the seasonal thermocline we estimate local vertical eddy diffusivities of the order of 4 10 4 m2 s 1 using a thorpe scale analysis although this estimate is higher by an order of magnitude than the canonical value o 0 1 10 4 m2 s 1 in the open ocean away from boundaries it is consistent with nonlinear internal wave wave interaction theories as verified by independent diffusivity estimates using the vertical wavenumber spectral methods for shear and strain it is also suggested that the general ocean circulation may play an important role in preconditioning the bloom in that the relatively sluggish circulation over the shallow plateau compared to the much more dynamic neighbouring deep ocean may foster the bloom s observed annual recurrence over the plateau

intensive surveys of the azores front 2 inferring the geostrophic and vertical velocity fields the geostrophic and vertical velocity fields are inferred using density and horizontal velocity data from three seasoar acoustic doppler current profiler surveys of the azores front the analysis is a two step procedure consisting of 1 objective analyses to reflect the observed length scales and 2 dynamical adjustments so that the density field is statically stable and the velocity field is in geostrophic balance the vertical velocity is inferred using a version of the quasi geostrophic omega equation in which the stratification is allowed to vary in the horizontal the resulting vertical velocity peaks at 2 10 4 m s 1 at 200 300 m there is a tendency for the denser water to the north of the front to be downwelled while the warmer water to the south is upwelled the implied heat flux exceeds 10 w m 2 near 100 m depth so the upper 100 m is warmed while the lower water column is cooled tending to stratify the upper ocean ageostrophic horizontal flow is toward the dense side of the front at the surface the dominant terms in the density balance are time rate of change and horizontal advection the inferred circulation cells may be an important mechanism of subduction in the upper ocean

geometry and origin of large scale deformation structures in some ancient wind blown sand deposits large scale deformational features that disrupt the cross bedded strata of some ancient wind blown dune sand deposits jurassic aztec and navajo sandstones u s a can betraced laterally for at least tens of metres information from four exposures leads to an idealized deformation style characterized by 1 a head portion marked by collapse features 2 a middle portion marked by a thrust ramp or a large recumbent fold and 3 a toe portion marked by a planar shear zone with small recumbent folds drag folds and possibly small horizontal shear faults an hypothesis involving earthquake induced liquefaction and collapse of the dunes is proposed sands liquefied during earthquakes cannot support an unequal surface load resulting in the collapse of surface dunes above the liquefied substrate compensatory lateral squeezing of liquefied sand and buried strata produces the shear zone in the toe portion engineering studies suggest that buried strata underlying interdunal lows where over burden stress is least will be most susceptible to liquefaction other considerations suggest that it will be the steeper lee sides of advancing surface dunes that collapse squeezing liquefied sand forward or downwind i e away from the lee slope of surface dunes if the liquefied condition persists load structures can be formed when unliquefied layers founder into the liquefied substrate

sedimentology of cold climate aeolian sandsheet deposits in the askja region of northeast iceland active aeolian sandsheets cover an area of 270 km2 in the askja region of ne iceland the sandsheet is divided into i a deflationary upwind part that is characterised by deflation lags ventifacted boulder fields and restricted aeolian sand patches in the lee of obstacles ii an accumulating central part that is characterised by continuous aeolian sand cover up to 10 m thick where three scales of aeolian ripples are evident along with larger scale forms including longitudinal zibars and iii a downwind part that is currently subject to aeolian bypass with only localised accumulation occurring in topographic hollows between basaltic lava fields trains of aeolian granule megaripples are a characteristic landform of the downwind part of the sandsheet these sinuous crested oblique bedforms attain heights of 0 35 m and downwind spacings of 6 m they are composed principally of low density pebble grade pumice clasts and other reworked volcaniclastic detritus derived from the nearby askja volcanic centre the distribution of landforms across the sandsheet reflects a regional aeolian sediment budget that is controlled by dynamic interactions between glacial ice margin fluvial aeolian and volcaniclastic processes under the influence of a distinctive climatic regime sediment supply at the upwind sandsheet margin adjacent to the dyngjujokull glacier increases during summer periods when rates of glacial ablation are at a maximum longer term controls on sediment supply rate are determined by episodes of glacier surging and retreat and by periodic eruptions of volcaniclastic debris from the askja volcanic centre the availability of sediment for aeolian transport is controlled by the level of the groundwater table the depth and continuity of the permafrost layer in the proglacial area the degree of development of armoured pebble lags and freezing of the sandsheet surface during winter months the transport capacity of the wind varies on a seasonal basis with mean wind velocities and wind gustiness reaching a maximum during winter periods both winter and summer mean wind velocities have been steadily increasing since formal records began in 1969 the suite of aeolian landforms developed within the askja region as defined by sediment texture and composition and bedform scale morphology and spatial distribution reflects a special set of controlling circumstances which mean that the askja sandsheet deposits differ significantly from those described from elsewhere

fluvial aeolian interactions part i modern systems two modern fluvial aeolian depositional systems great sand dunes national monument colorado and the mojave river wash california are remarkably similar in spite of different climates sizes fluvial sediment textures and relative directions of aeolian and fluvial transport dune growth and migration and deflation of blowouts create 8 10 m of local relief in unflooded aeolian landscapes there are six prominent fluvial aeolian interactions 1 fluvial flow extends into the aeolian system until it is dammed by aeolian landforms 2 interdune areas overbank interdunes upstream of aeolian dams and alongside channels are flooded 3 water erodes dunes alongside channels and interdunes 4 flood waters deposit sediment in interdune areas 5 fluvially derived groundwater floods interdunes interdune playas 6 wind erodes fluvial sediment and redeposits it in the aeolian system unique and characteristic sediments are deposited in overbank interdunes and in interdune playas reflecting alternate fluvial and aeolian processes and rapidly changing flow and salinity conditions these fluvial aeolian interdune deposits are characterized by irregular concave up bases and flat upper surfaces containing mudcracks or evaporite cement characteristic low relief surfaces form in aeolian systems as an effect of flooding fluvial deposits are resistant to aeolian deflation aeolian sand is preserved when flood sediments are deposited around the bases of the dunes thus repetitive fluvial and aeolian aggradation tends to be stepwise as interdune floors are suddenly raised during floods the effects of flooding should be easy to recognize in ancient aeolianites even beyond the area covered with overbank muds

some aspects of the geochemistry provenance and palaeoclimatology of the torridonian of nw scotland geochemical data mostly from mudstones are used in an attempt to investigate some aspects of the palaeoclimatology and provenance of the torridonian succession in nw scotland the basal part of the stoer group which has been interpreted as glaciogenic is thought to have formed in a warm arid setting the presence of oscillation ripples and desiccation cracks in mudstones containing isolated clasts is thought to preclude their interpretation as ice rafted debris some aspects of the major element geochemistry of the stoer group mudstones suggest deposition in an environment with little weathering but chemical weathering is inhibited in both frigid and arid settings and sedimentological evidence favours the latter the stoer group mudstones are enriched in mg ca and na relative to the torridon group samples which are much closer in composition to an average shale estimate paas the cr and ni contents of the stoer mudstones are significantly higher than those of the torridon group samples there is however no evidence that enrichment in these elements was due to contamination with volcanic material like that of the stac fada member the scourian basement appears to be an adequate source of the ni and cr in the stoer group sediments th sc ratios are higher in the torridon than in the stoer mudstones this difference is interpreted as indicating that the stoer mudstones were largely derived from local archaean sources but that the torridon group mudstones incorporated materials from a much wider provenance including younger and recycled materials evidence from rare earth elements also provides evidence for different source terrains for the stoer and torridon groups the torridon group mudstones are more weathered have a higher ree content and display a more prominent eu anomaly lower value for eu eu than do the stoer samples these results support evidence from th sc ratios that the torridon group was derived from a more varied recycled and granite rich terrain than the stoer much of which appears to have relatively local provenance the geochemistry of mudstones can shed considerable light on problems of provenance and palaeoclimatology because many useful trace elements tend to be concentrated in such fine grained rocks and some aspects of their major element chemistry may be related to climatic factors

cross frontal exchange of antarctic intermediate water and antarctic bottom water in the crozet basin abstract the hydrographic survey made across the antarctic circumpolar current acc in the southwestern crozet basin during the april may 1993 antares 1 cruise revealed unprecedented strong cross frontal injections of newly formed antarctic intermediate water aaiw into the subtropical zone north of the acc the acc in this area is mostly associated with the subantarctic front saf and subtropical front stf which are tightly merged into one structure bordered to the north with the eastward extension of the agulhas return current the oxygen and salinity extrema of the newly injected aaiw at a depth of 1200 m well north of the stf reach as high as 6 17 ml l 1 and 34 15 these values coincide almost exactly with those in the aaiw source found at a depth of 500 m just south of the saf but surpass considerably oxygen by 1 35 ml l 1 and salinity by 0 23 psu those values corresponding to the old aaiw at the nearby subtropical stations such spectacular cross frontal injections of new aaiw were not continuous in space and time but were found to be rather local intermittent and impulsive this was closely correlated with the highly perturbed meandering frontal zone due to the frequent passages of strong atmospheric depressions during the cruise there is also clear evidence of the northward penetration of antarctic bottom water aabw through the crozet kerguelen gap and its northward flow along the deep western boundary of the crozet basin supporting previous observations moreover our observations indicate more precisely the bottom water pathway which is concentrated against the continental rise west of 56 e following roughly the 4000 m isobath it is concluded that the crozet basin frontal zone acts as a barrier only for the upper layer water masses and that it is dynamically transparent for the cross frontal exchange of intermediate and deeper layer water masses of potential density anomalies greater than 27 1 including aaiw and aabw

pre vegetation fluvial floodplains and channel belts in the late neoproterozoic cambrian santa barbara group southern brazil abstract one key element to the understanding of the dynamics of pre vegetation fluvial systems is the reconstruction of processes operating on their floodplains given that in modern systems channel banks and floodplains are the environments most affected by plant colonization notwithstanding few pre vegetation floodplains have been described and major questions regarding their most basic characteristics are still unresolved in order to address these questions detailed analysis of coeval channel belt fluvial floodplain and alluvial fan deposits from the santa barbara group late neoproterozoic to early cambrian southern brazil was performed while floodplain facies resemble ephemeral stream deposits being coarser grained than modern floodplains and marked by the stacking of flood event cycles channel belt deposits show composite bars which do not present conclusive evidence for high water discharge variation the floodplain deposits show particular features common to other pre vegetation fluvial systems such as better preserved small scale structures lack of bioturbation and abundance of cross laminated sandstones while other features differ from previous depositional models namely abundant mudcracks and evidence of soil formation the lateral variation of depositional systems recorded in the santa barbara group shows contrasting signatures of water discharge variation in sand dominated coeval environments and offers an example of the relation between different alluvial environments before the evolution of land plants

fluvial channel belts floodbasins and aeolian ergs in the precambrian meall dearg formation torridonian of scotland inferring climate regimes from pre vegetation clastic rock records abstract the interpretation of climate regimes from facies analysis of precambrian clastic rocks has been challenging thus far hindering full reconstructions of landscape dynamics in pre vegetation environments yet comparisons between different and co active sedimentary realms including fluvial channelised floodplain and aeolian hold the potential to shed further light on this thematic this research discusses a fluvial aeolian record from the 1 2 ga meall dearg formation part of the classic torridonian succession of scotland tentatively considered to date as a braided fluvial deposit this unit is here reappraised as the record of fluvial channel belts floodbasins and aeolian ergs fluvial deposits with abundant transitional to upper flow regime structures mostly cross beds with tangential sets and plane antidunal beds and simple low relief sediment bars indicate a low sinuosity ephemeral style floodbasin deposits consist of plane and cross beds ubiquitously bounded by symmetrical ripples and rare sediment bars related to the progradation of splay complexes in temporary flooded depressions aeolian deposits occur nearby basement topography and are dominated by large scale pin stripe laminated cross beds indicative of intermountain ergs neither ephemeral fluvial nor intermountain aeolian systems can be considered as reliable indicators of local climate since their sedimentary style is respectively controlled by catchment size and shape and basin topography relative to groundwater tables contrarily the occurrence of purely clastic rather than carbonate or evaporitic floodplain strata can be more confidently related to humid regimes in brief this study provides new insight into an overlooked portion of the torridonian succession of scotland and discusses climate inferences for precambrian clastic terrestrial rocks

architecture of pre vegetation sandy braided perennial and ephemeral river deposits in the paleoproterozoic athabasca group northern saskatchewan canada as indicators of precambrian fluvial style abstract the late paleoproterozoic athabasca basin contains more than 1 5 km of predominantly sandy strata most of which are of braided fluvial origin in the eastern part of the basin at mcclean lake sandstones and minor conglomerates of the read formation at the base of the succession are preserved within a steep walled valley system they consist predominantly of meter scale sheet elements characterized by massive and flat laminated fine to very coarse grained sandstone with minor discontinuous cobble and boulder conglomerate along lower set boundaries these are interpreted as sheet flood and stream flood deposits of a terminal dry land system deposited in an arid climatic setting analysis of closely spaced drill core indicates that late stage run off was confined to small shallow channels typically only a few tens of meters wide and a few meters deep overlying strata of the bird member of the manitou falls formation are predominantly coarse to very coarse grained sandstones with abundant small scale cross stratification and minor granule and small pebble conglomerate at mcclean lake these appear to have been deposited as sheet elements by semi ephemeral to perennial braided rivers under more humid conditions at key lake 160 km to the southwest architectural analysis of a 184 m wide section indicates that at least part of the bird member was deposited in deeper sandy braided rivers characterized by seasonally varied flow the closest modern analogue is the south saskatchewan river in which large simple flow transverse bedforms become exposed and dissected during falling stage and act as nuclei for sand flat development the presence of numerous low relief 4th order surfaces suggests continued reworking of bar tops during rising stage the incremental character of downstream accretionary elements suggests periodic migration of barforms during peak flood stages separated by periods of low flow this indicates similarities with modern perennial braided systems and is counter to the idea that all pre devonian fluvial systems should consist of stacked sheets formed by individual flood events thin gravel layers accumulated as lags on fourth order surfaces with discontinuous mud layers suggesting deposition within temporary ponds in channel thalwegs after major floods strata in overlying units indicate a return to semi perennial conditions

frontal structure water masses and circulation in the crozet basin due to topographic steering by the crozet and kerguelen plateaus the antarctic circumpolar current acc core in the crozet basin area is shifted to its northernmost position in the southern ocean along the southern limb of the south indian subtropical gyre here the jet like current is embedded within a narrow band 26 5 kg m3 in the western half of the basin and heavier mode 26 7 kg m3 in its eastern half these different varieties of crozet basin mode water are closely correlated with the degree of exchange and mixing between subtropical and subantarctic waters along the dynamically active frontal zone the area north of the kerguelen plateau appears to be an important source of water mass modification antarctic intermediate water advected from the west also undergoes there significant modification by intrusions across the frontal zone of fresher oxygen richer colder subantarctic water energetic eddy activities observed along the frontal zone likely enhance such cross frontal exchange of water masses equatorward spreading of the modified thermocline water masses mode water antarctic intermediate water occurs as part of the anticyclonic circulation in the south indian subtropical gyre which is centered within the basin strong injection of north indian deep water into the acc south of amsterdam island is clearly evidenced for the first time this deep oxygen minimum water centered at about 3000 m can be traced to the east of madagascar from where it spreads southward through the eastern part of the crozet basin due to the influence of this water mass north atlantic deep water characteristics of the circumpolar deep water are significantly altered in kerguelen amsterdam passage our results indicate a cyclonic deep level circulation pattern in the crozet basin with a northward flow 9 sv of circumpolar deep water antarctic bottom water as a deep western boundary current and a partially compensating southward flow 3 sv of north indian deep water through the eastern part of the basin it is concluded that the crozet basin constitutes an important passage for the exchange of water masses between the southern ocean and the indian ocean

alluvial facies evolution during the palaeozoic greening of the continents case studies conceptual models and modern analogues the palaeozoic greening of the continents the appearance and expansion of embryophytes land plants in terrestrial environments was arguably the most fundamental phanerozoic change to the earth system thirteen case studies of cambrian to devonian fluvial deposits from north america and europe are documented here to illustrate the evolution of fluvial style during this period during the cambro ordovician prior to the advent of terrestrial vegetation fluvial systems laid down relatively coarse sands with little mud resulting in self formed channels and an architecture dominated by broad sheets of trough cross beds sheet braided style similar deposits formed across a wide range of latitudes and passed basinward into sandy coastal deposits from the mid ordovician onwards an increase in floodplain mudstone corresponds broadly with the appearance of embryophytes which would have progressively enhanced upland weathering mud production and floodplain storage of fines during the late silurian small heterolithic channel bodies with lateral accretion sets provide the first evidence of meandering channels and floodplain mudstones contain more varied palaeosols especially calcretes which appear abundantly for the first time by the early devonian channel deposits comprise sandstone lenses channelled braided style probably due to the increased bank strength and cohesion and reduced potential for sediment sorting imparted by sand mud mixtures muddy coastal deposits are prominent by the upper devonian fluvial deposits commonly contain fossil trees and large mainstem meandering channels with lateral accretion sets indicating that rooted vegetation stabilized channels the advent of stable floodplains with levees crevasse splays and organic litter would have encouraged the diversification of terrestrial invertebrates which left alluvial ichnological signatures from the late silurian onwards

life on land in the proterozoic evidence from the torridonian rocks of northwest scotland the stoer group and diabaig formation of the torridonian succession in northwest scotland are late mesoproterozoic to early neoproterozoic ca 1200 1000 ma features preserved on the top surfaces of fine to medium grained sandstone beds in a number of stratigraphically and geographically separated localities are attributable to microbially induced sedimentary structures these include wrinkle structures remnants of apparent microbial crusts and indications of original cohesiveness and pliancy in sand sized sediment the surfaces on which the microbial structures formed were exposed subaerially abundant deep desiccation cracks and locally pedogenic structures in alluvial interfluve and lacustrine margin settings and many of the structures developed in areas well away from the perennially wetted regions adjacent to shorelines and fluvial channels thus these features indicate that earth9s biosphere had adapted to and colonized land surfaces many hundreds of millions of years before the dawn of the phanerozoic

linking foraging behaviour to physical oceanographic structures southern elephant seals and mesoscale eddies east of kerguelen islands in the southern ocean mesoscale features such as fronts and eddies have been shown to have a significant impact in structuring and enhancing primary productivity they are therefore likely to influence the spatial structure of prey fields and play a key role in the creation of preferred foraging regions for oceanic top predators optimal foraging theory predicts that predators should adjust their movement behaviour in relation to prey density while crossing areas with sufficient prey density we expect predators would change their behaviour by for instance decreasing their speed and increasing their turning frequency diving predators would as well increase the useful part of their dive i e increase bottom time thereby increasing the fraction of time spent capturing prey southern elephant seals from the kerguelen population have several foraging areas in antarctic waters on the kerguelen plateau and in the interfrontal zone between the subtropical and polar fronts this study investigated how the movement and diving behaviour of 22 seals equipped with satellite relayed data loggers changed in relation to mesoscale structures typical of the interfrontal zone we studied the links between oceanographic variables including temperature and sea level anomalies and diving and movement behaviour such as displacement speed diving duration and bottom time correlation coefficients between each of the time series were calculated and their significance tested with a parametric bootstrap we focused on oceanographic changes both temporal and spatial occurring during behavioural transitions in order to clarify the connections between the behaviour and the marine environment of the animals we showed that a majority of seals displayed a specific foraging behaviour related to the presence of both cyclonic and anticyclonic eddies we characterized mesoscale oceanographic zones as either favourable or unfavourable based on the intensity of foraging activity as identified by the behavioural variables our findings highlight the importance of mesoscale features for top predators behaviour and introduce a new approach for evaluating the importance to the seals of the origin and intensity of these features

determination of the surface geostrophic velocity field from satellite altimetry 1 presently available marine geoid models are not accurate enough to extract the mean surface circulation directly from satellite altimetry a novel method for estimating the mean velocity field of major ocean current systems is derived from the free surface boundary condition with a given quasi geostrophic balance for the horizontal surface flow a scaling analysis of this boundary condition indicates that although the vertical velocity w is mostly balanced by the local change of the free surface t useful information on the mean current is contained in a small ageostrophic departure t w our method consists in the development of a simple algebraic equation with two unknowns and an adjustable parameter associated with t assuming that the latter is proportional to t w most interestingly t and all other coefficients of the equation can be determined from altimetry the altimeter data used is combined topex poseidon ers gridded data and the solution is obtained by least squares minimizing the contribution from the time variable part of the parameter and prescribing the zonal direction of the mean current the method which is found to be particularly useful for quasi zonal high energy current systems has been validated against direct observations in the gulf stream and southern ocean comparisons with direct observations and monte carlo experiments suggest an overall solution error of about 10 cm s 1 once calibrated against regional velocity statistics this method will be able to determine from altimetry the mean or instantaneous surface velocity field down to the frontal scale with a realism that has been inaccessible because of the geoid constraint

the importance of air escape processes in the formation of dish and pillar and teepee structures within modern and precambrian fluvial deposits abstract attributed to escape of water from unconsolidated deposits teepee and dish and pillar structures are common features in the late proterozoic torridonian red bed succession of nw scotland study of the first annual flood on a modern depositional analogue in wadi baysh saudi arabia revealed that a layer of mud initially deposited across the alluvium restricted the escape of air being displaced through the normally unconfined aquifer by waters entering the aquifer from the river channels as air bubbled through high level pool floor muds it generated dish and pillar structures the formation of teepee structures by similarly combined air and water escapes nearer to the channel later in the annual cycle of flooding is foreseen it is suggested that the two sediment structures are generated in response to different parts of the aquifer recharge spectrum the role of air displacement by influent waters is important in the initial phases of structure formation and combined air and water escape creates greater disturbance to the sediments the sedimentary structures formed are not therefore solely due to water escape as has been previously suggested ephemeral seasonal flooding appears to have characterized the deposition of at least the stoer group and diabaig formation sediments in the torridonian

fronts transport and weddell gyre at 30 e between africa and antarctica a detailed description of the frontal structure of major currents and estimates of transport between africa and antarctica at 30 e were made on the basis of a finely resolved hydrographic section made during the 1996 civa 2 cruise particular emphasis was put on a refinement of the eastern boundary of the weddell gyre by analyzing also supplementary hydrographic data from the 1993 civa 1 cruise and the best available historical hydrographic data in the weddell and enderby basins contrary to the general belief our results show that the weddell gyre extends far beyond 30 e reaching at least as far east as the enderby land promontory 53 e from this point westward currents along the antarctic continental margin constitute the gyre s southern boundary thus closing the cyclonic circulation of the gyre at its easternmost end as the most convincing evidence for this refined circulation scheme significant westward transport south of 65 s has been identified from the civa 1 acoustic doppler current profiler data we have shown also using an inertial jet model that the blocked feature of the weddell cold regime 57 s to the west of 25 e is due to the topographic control of flow by local bathymetry during the civa 2 cruise 70 of the antarctic circumpolar current acc was concentrated near the polar front 51 s with surface speeds reaching up to 70 cm s 1 the baroclinic current field in the subpolar area south of the weddell front 58 s for civa 2 and 57 s for civa 1 is featureless 3 cm s 1 but yielding a nonnegligible eastward transport of 15 sv 1 sv 106 m3 s 1 this bottom referenced baroclinic transport is entirely compensated by a substantial westward barotropic transport south of 65 s the acc transport across the 30 e section during the civa 2 cruise is estimated to be 160 sv

vorticity and vertical circulation at an ocean front abstract density and velocity data with 4 km horizontal resolution from a survey of a front during fasinex frontal air sea interaction experiment are combined to describe the structure of the top 300 m of the ocean the geostrophic velocity field is derived and is used to examine the relative importance of stratification relative vorticity and twisting terms in ertel s potential vorticity q tenfold isopycnic changes in q are found across a horizontal scale of only 10 km these changes are confined to isopycnals that outcrop from the seasonal thermocline into the mixed layer the ageostrophic velocity field is quantified by solution of the omega equation and vertical velocities of up to 40 m day 1 are found small 40 km surface trapped top 200 m eddies are found to play a crucial role in the transport and effective diffusion of properties across the thermocline out of the mixed layer

3 2ga eolian deposits from the moodies group barberton greenstone belt south africa implications for the origin of first cycle quartz sandstones abstract the 3 2 ga moodies group in barberton greenstone belt south africa contains the oldest recognized evidence for eolian processes on earth these eolian facies indicate that significant wind regimes existed in the archean atmosphere eolian deposits are developed in the lower moodies group in the central part of the belt and consist of stacked inversely graded strata ranging in thickness from 2 to 10 mm individual strata consist of fine to medium grained quartz sandstone at the base that passes vertically into very coarse to coarse grained quartz sandstone strata make up cross bed sets up to 3 5 m thick sets of wind ripple strata are either tabular tangential or in the form of broad troughs this type of inversely graded stratification is the product of wind ripple migration the coarse grain size of the sediment combined with the low angle of inclination of the strata is best interpreted as the product of sand sheet or dune plinth preservation based on the geometry of eolian set boundaries dunes were probably simple barchan form the tens of meters thick eolian deposits are underlain by braided stream deposits composed of subfeldspathic pebbly sandstones the vertical change from braided stream subfeldspathic sandstones to eolian quartz arenites highlights the underappreciated capacity of eolian processes to generate first cycle quartz sandstones on landscapes pre dating the advent of land vegetation

a precambrian proximal ejecta blanket from scotland ejecta blankets around impact craters are rarely preserved on earth although impact craters are ubiquitous on solid bodies throughout the solar system on earth they are rapidly effaced and few records exist of the processes that occur during emplacement of ejecta the stac fada member of the precambrian stoer group in scotland has previously been described as volcanic in origin however shocked quartz and biotite provide evidence for high pressure shock metamorphism while chromium isotope values and elevated abundances of platinum group metals and siderophile elements indicate addition of meteoritic material thus the unit is reinterpreted here as having an impact origin the ejecta blanket reaches 20 m in thickness and contains abundant dark green vesicular devitrified glass fragments field observations suggest that the deposit was emplaced as a single fluidized flow that formed as a result of an impact into water saturated sedimentary strata the continental geological setting and presence of groundwater make this deposit an analogue for martian fluidized ejecta blankets

alluvial eolian and lacustrine sedimentology of a paleoproterozoic half graben baker lake basin nunavut canada the northeast trending baker lake sub basin was a volcanically active half graben during deposition of ca 1 85 1 76 ga baker lake group drainage was oriented along transverse and axial directions with flow to playa lake and deeper perennial lacustrine depocentres basin marginal streamflow dominated alluvial fans were concentrated along the southern margin and provided sediment from archean crystalline basement rocks these fed transverse gravel and sand bed braided streams alluvial dynamics were characterized by channel aggradation and abandonment abandoned channel belts were sites of floodplain and eolian deposition basin axial braided streams fed northeast and southwest to a depocentre near christopher island where eolian playa and lacustrine environments were intimately linked felsic minette flows were initially erupted from localized centres contemporaneous sedimentary deposits typically contain minor volcaniclastic components that increase in abundance basinward voluminous and widespread younger minette flows prograded outward from volcanic centres contributing significant additional basin infill

circulation pathways and transports of the southern ocean in the vicinity of the southwest indian ridge circulation pathways and transports of the antarctic circumpolar current acc and agulhas return current arc around the complex bathymetry of the southwest indian ridge and del cano rise have been established from two hydrographic surveys and two year long moorings after crossing the southwest indian ridge in a 110 sv 1 sv 106 m3s 1 flow concentrated at 48 s the acc fragments before being reconcentrated into several branches by the bathymetry in particular 30 40 sv turns north around the eastern flank of the del cano rise turns west as part of anticyclonic flow round the del cano rise finally returning eastward as part of the crozet front eddy variability from both satellite data and moorings is low over the bathymetry of the del cano rise so the strong currents found between the del cano rise and the crozet plateau are believed to be permanent features this largely barotropic time independent transport is the major pathway for the acc to enter the crozet basin the anticyclonic flow also transfers water from the mozambique basin across the southwest indian ridge to the south side of the del cano rise given the evidence for fragmentation of the acc where it crosses the southwest indian ridge and the concentration of several jets into the crozet front from the acc subtropical front and agulhas return current it is misleading to relate standard frontal definitions such as the polar front and subantarctic front to the major transport pathways

facies model for fluvial systems in the seasonal tropics and subtropics facies models that summarize the deposits of fluvial systems are well established for humid climate settings and for desert environments but the deposits of rivers in the sub humid and semiarid seasonal tropics have been largely ignored our observations and data from modern streams and recent deposits in northeastern australia show how such rivers with extremely variable discharge have distinctive deposit characteristics that are substantially different from conventional fluvial facies models these properties include 1 erosionally based channel fill lithosomes that exhibit complex lateral facies changes with 2 abundant pedogenically modified mud partings 3 complex internal architecture that may lack the macroform elements typical of other fluvial sediment bodies 4 an abundance of sedimentary structures formed under high flow stage and 5 an abundance of in situ trees that colonize channel floors and are adapted to inundation by fast flowing water we illustrate examples of this fluvial style from the rock record and set out a new facies model the recognition of such a distinctive fluvial character and of changes in character through vertical successions will aid paleoclimate and reservoir analysis

dissolved iron in the vicinity of the crozet islands southern ocean the annual phytoplankton bloom occurring north of the crozet plateau provides a rare opportunity to examine the hypothesis that natural iron fertilization can alleviate high nutrient low chlorophyll hnlc conditions normally associated with the southern ocean therefore during crozet natural iron bloom and export experiment crozex a large multidisciplinary study performed between november 2004 and january 2005 measurements of total dissolved iron dfe0 2 m were made on seawater from around the islands and atmospheric iron deposition estimated from rain and aerosol samples dfe concentrations were determined by flow injection analysis with n n dimethyl p phenylenediamine dihydrochloride dpd catalytic spectrophotometric detection dfe concentrations varied between 0 086 and 2 48 nm with low values in surface waters enrichment of dissolved iron 1 nm at close proximity to the islands suggests that the plateau and the associated sediments are a source of iron waters farther north also appear to be affected by this input of coastal and shelf origin although dissolved iron concentrations decrease as a function of distance to the north of the plateau with a gradient of 0 07 nm km 1 at the time of sampling using lateral and vertical diffusion coefficients derived from ra isotope profiles and also estimates of atmospheric inputs it was then possible to estimate a dfe concentration of 0 55 nm to the north of the islands prior to the bloom event which is sufficient to initiate the bloom the lateral island source being the largest component a similar situation is observed for other sub antarctic islands such as kerguelen south georgia that supply dissolved iron to their surrounding waters thus enhancing chlorophyll concentrations

stratigraphic evolution of an aeolian erg margin system the permian cedar mesa sandstone se utah usa the permian cedar mesa sandstone of south east utah is a predominantly aeolian succession that exhibits a complex spatial variation in sedimentary architecture which in terms of palaeogeographic setting reflects a transition from a dry erg centre through a water table controlled aeolian dominated erg margin to an outer erg margin subject to periodic fluvial incursion the erg margin succession represents a wet aeolian system accumulation of which was controlled by progressive water table rise coupled with ongoing dune migration and associated changes in the supply and availability of sediment for aeolian transport variation in the level of the water table relative to the depositional surface determined the nature of interdune sedimentary processes and a range of dry damp and wet flooded interdune elements is recognized variations in the geometry of these units reflect the original morphology and the migratory behaviour of spatially isolated dry interdune hollows in the erg centre locally interconnected damp and or wet interdune ponds in the aeolian dominated erg margin and fully interconnected fluvially flooded interdune corridors in the outer erg margin relationships between aeolian dune and interdune units indicate that dry damp and wet interdune sedimentation occurred synchronously with aeolian bedform migration temporal variation in the rates of water table rise and bedform migration determined the angle of climb of the erg margin succession such that accumulation rates increased during periods of rapidly rising water table whereas sediment bypassing zero angle of climb occurred in the aftermath of flood events in response to periods of elevated but temporarily static water table during these periods in the outer erg margin the expansion of fluvially flooded interdunes in front of non climbing but migrating dunes resulted in the amalgamation of laterally adjacent interdunes and the generation of regionally extensive bypass flood supersurfaces a spectrum of genetic depositional models is envisaged that accounts for the complex spatial and temporal evolution of the cedar mesa erg margin succession

sedimentary facies in an extensional and deep lacustrine depositional system the pliocene tiberino basin central italy abstract the tiberino basin was formed during plio pleistocene extensional tectonic activity in central italy the pliocene sediments that fill this structure consist predominately of fine grained clastic lithofacies deposited in a lacustrine system four facies associations have been distinguished facies association a was deposited in a deep offshore lacustrine environment and consists of massive laminated bluish gray marly clays that lack benthonic fauna but have preserved organic matter leaves wood this facies association is the main lacustrine deposit whereas the other three represent marginal facies facies association b is interpreted as a delta system deposit it has gilbert type sandy gravel bodies with foresets up to 50 m high and prodelta bodies consisting of laminated to massive marly clays that alternate with sandy and gravelly mud strata association c corresponds to a coastal environment where two sub environments are recognized 1 a wave dominated coastline characterized by interbedded muddy and sandy strata with sedimentary structures attributed to hummocky cross stratification and 2 clayey silts and lignites interpreted as a coastal wetland a spectacular fossil forest is preserved in situ within this unit association d formed on the distal part of a muddy alluvial fan consists of sheet flood clayey sandy silts that alternate with incipient paleosols rare ribbon channel fills are also present paleoenvironmental reconstruction indicates that the tiberino basin was occupied by a narrow deep meromictic lake during the pliocene the size shape depth and sub environment distribution of this lake were controlled by tectonic phenomena such as the high subsidence rate which caused the lake to be large and deep only in the few coastal areas that had high sedimentary input were wetland or alluvial fan deposits formed

aeolian architecture bedform climbing and preservation space in the cretaceous etjo formation nw namibia sets of aeolian cross strata within the cretaceous etjo formation of nw namibia are bounded by a hierarchy of surfaces the origin of which are ascribed to one of four processes related to aeolian bedform and erg behaviour the base of the main aeolian succession is characterized by a basin wide erosional supersurface that formed in response to a period of aeolian deflation before the onset of the main phase of erg building interdune migration surfaces formed by draa migration are planar in sections parallel to the palaeowind and are inclined at up to 5 in an upwind direction sw perpendicular to the palaeowind interdune surfaces form 500 m wide troughs signifying crestline sinuosity within the original bedforms superimposition surfaces are inclined at 5 10 in a downwind direction and indicate the migration of crescentic oblique dunes over larger slipfaceless transverse draa reactivation surfaces associated with minor changes in dune slipface orientation are distinct from other bounding surface types because overlying cross strata lie parallel to them rather than downlap onto them analysis of the geometry of these bounding surfaces together with the orientation of the cross strata within the sets that they bound has enabled the detailed morphology of the original bedforms to be reconstructed the maximum preserved thickness of individual aeolian sets varies systematically across the basin from 52 m in the basin depocentre to only 8 m at the basin margin the set architecture indicates that this spatial variation is primarily the result of decreased angles of bedform climb at the basin margin rather than the presence of smaller bedforms similarly a temporal reduction in the angle of climb rather than a reduction in bedform size is considered to be responsible for an upward decrease in preserved set thickness reductions in bedform climb angle reflect progressive loss of accommodation space as the accumulating erg filled the basin

137cs water profiles in the south indian ocean an evidence for accumulation of pollutants in the subtropical gyre abstract the 137 cs seawater transect along the 20 s latitude in the indian ocean sampled during the round the globe beagle2003 blue ocean global expedition clearly shows a presence of two cores of higher 137 cs concentrations at 100 e and 55 e in water column depths between 100 and 200 m the subsurface maximum of 137 cs activity concentration 2 1 mbq l observed near 100 e is the highest level found in southern hemisphere seawater which is comparable to the maximum 137 cs concentration observed in north pacific surface water this transect represents the first high density sight of 137 cs distribution in south indian ocean waters the estimated 137 cs water column inventories up to 1240 bq m 2 normalized for the 1000 m water depth along the 20 s latitude are by a factor of three higher than would be expected from global fallout in the south indian ocean the estimated residence time of 137 cs in surface waters of the south indian ocean 30 years is by about a factor of two higher than for the north pacific the 137 cs data confirm a transport of surface waters from the north pacific via indonesian seas to the south indian ocean and to the subtropical gyre the subtropical gyre is an important reservoir of anthropogenic pollutants that have been transported from the north pacific and indian oceans to the south on a time scale of several decades

transport and scavenging of pu in surface waters of the southern hemisphere oceans abstract the distribution of 239pu in atlantic and indian ocean waters about four decades after their main injection from atmospheric nuclear weapons tests is discussed recent data obtained in the framework of the shots southern hemisphere ocean tracer studies projects are evaluated and compared with previous investigations seawater samples were collected during the round the globe beagle2003 blue ocean global expedition along the 30 s transect in the atlantic and the 20 s transect in the indian ocean the results indicate transport of surface waters labelled with 239pu from the western north pacific via the indonesian seas to the south indian ocean and then to the south atlantic ocean along the whole beagle2003 sampling route the atlantic ocean has the lowest 239pu content due to its particle scavenging on the long way from the western north pacific on the other hand concentrations of the conservative 137cs tracer are in all three oceanic basins comparable the primary productivity reflected by the chlorophyll content in surface waters has similar longitudinal distribution as 239pu radioactive and chlorophyll tracers revealed that the most important current system in each southern oceanic basin is represented by the subtropical gyre while the main streams of the gyres maintain high concentrations of tracers inside the loops the tracer concentrations are the lowest

fluvial features on titan insights from morphology and modeling fluvial features on titan have been identified in synthetic aperture radar sar data taken during spacecraft flybys by the cassini titan radar mapper radar and in descent imager spectral radiometer disr images taken during descent of the huygens probe to the surface interpretations using terrestrial analogs and process mechanics extend our perspective on fluvial geomorphology to another world and offer insight into their formative processes at the landscape scale the varied morphologies of titan s fluvial networks imply a variety of mechanical controls including structural influence on channelized flows at the reach scale the various morphologies of individual fluvial features implying a broad range of fluvial processes suggest that paleo flows did not occupy the entire observed width of the features disr images provide a spatially limited view of uplands dissected by valley networks also likely formed by overland flows which are not visible in lower resolution sar data this high resolution snapshot suggests that some fluvial features observed in sar data may be river valleys rather than channels and that uplands elsewhere on titan may also have fine scale fluvial dissection that is not resolved in sar data radar bright terrain with crenulated bright and dark bands is hypothesized here to be a signature of fine scale fluvial dissection fluvial deposition is inferred to occur in braided channels in paleo lake basins and on sar dark plains and disr images at the surface indicate the presence of fluvial sediment flow sufficient to move sediment is inferred from observations and modeling of atmospheric processes which support the inference from surface morphology of precipitation fed fluvial processes with material properties appropriate for titan terrestrial hydraulic equations are applicable to flow on titan for fully turbulent flow and rough boundaries for low reynolds number flow over smooth boundaries however knowledge of fluid kinematic viscosity is necessary sediment movement and bed form development should occur at lower bed shear stress on titan than on earth scaling bedrock erosion however is hampered by uncertainties regarding titan material properties overall observations of titan point to a world pervasively influenced by fluvial processes for which appropriate terrestrial analogs and formulations may provide insight