seismic reflector imaging using internal multiples with marchenko type equations we present an imaging method that creates a map of reflection coefficients in correct one way time with no contamination from internal multiples using purely a filtering approach the filter is computed from the measured reflection response and does not require a background model we demonstrate that the filter is a focusing wavefield that focuses inside a layered medium and removes all internal multiples between the surface and the focus depth the reflection response and the focusing wavefield can then be used for retrieving virtual vertical seismic profile data thereby redatuming the source to the focus depth deconvolving the upgoing by the downgoing vertical seismic profile data redatums the receiver to the focus depth and gives the desired image we then show that for oblique angles of incidence in horizontally layered media the image of the same quality as for 1d waves can be constructed this step can be followed by a linear operation to determine velocity and density as a function of depth numerical simulations show the method can handle finite frequency bandwidth data and the effect of tunneling through thin layers

isotope palaeotemperatures from the tjornes beds in iceland evidence of pliocene cooling abstract the mid pliocene warming episode is well established along the margins of the north atlantic and probably affected areas as far north as iceland rich marine mollusc faunas have been described from the 500 m of pliocene siliciclastic deposits on the tjornes peninsula in northeast iceland the faunal compositions indicate a development from warm water to arcto boreal conditions we have analysed the oxygen isotope composition of 96 well preserved specimens of the bivalves arctica islandica and pygocardia rustica and interpreted the data as palaeotemperatures after corrections for the isotopic composition of pliocene seawater the temperatures are in accordance with other palaeotemperature proxies we interpret our data as reflecting a gradual change from warm water conditions summer temperatures between 10 and 15 c during the deposition of the lower part of the tjornes beds tapes zone and lower part of mactra zone to cold water conditions summer temperatures between 5 and 10 c at the top top of mactra zone and serripes zone the coldest interval is found in the middle of the serripes zone where summer temperatures 5 8 c are comparable to those of the present environment off northern iceland the arrival to tjornes of cold water molluscs of pacific origin postdates the cooling of the seas around iceland we suggest that the cold interval in the serripes zone represents a cooling event prior to the final warm period ca 3 3 3 0 ma dowsett et al 1999 middle pliocene paleoenvironmental reconstruction prism2 us geol survey open file rep 99 53 of the mid pliocene warming

textural differentiation in chronosequences from eastern australia ii evidence from particle size distributions abstract data from particle size analyses were used to determine the relative importance of the four mechanisms proposed to explain the development of strong textural contrast in the end members of four chronosequences the mechanisms proposed were sedimentary layering in situ chemical weathering clay illuviation and physical breakdown depth functions of fine clay total clay ratios and detailed particle size distributions at o intervals from 0 6 m to 2000 m indicated that there had been a marked increase in fine clay in the b horizons of the older soils of each sequence a result consistent with but not proving a clay illuviation hypothesis cumulative particle size distribution indices showed that most profiles had texturally uniform parent materials changes in the ratio fine silt total silt with depth were slight for all but one profile indicating no significant contribution to the clay fraction by in situ chemical weathering of the silt fraction from changes in the depth functions of gravel with time it was concluded that physical breakdown had occurred but that it had not been responsible for the development of the textural b horizon the rate of disintegration was particularly high early in pedogenesis preceding the development of texture contrast breakdown contributed fines to the whole solum and was not generally any more intense in one horizon than another grain counts of rock fragments in the medium sand range lent support to this conclusion changes in the particle size distribution of quartz from 0 2 m to 2000 m indicated that the contribution to the clay fraction from physical disintegration was only slight

subsurface domain interferometric objective functions for target oriented waveform inversion abstractresolving details in subsurface reservoir parameters from surface waveform data is a challenging problem particularly when a reservoir is beneath a complex overburden whose properties are also poorly known we have developed new metrics for detecting and quantifying errors in subsurface models that are well suited for target oriented inversion our metric when combined with state of the art redatuming aims at enabling waveform inversion for target volume parameters with no need to resolve model features elsewhere e g in the overburden we refer to these metrics as interferometric objective functions because they rely on extrapolation from reciprocity integrals commonly used in seismic interferometry as in seismic interferometry wavefield extrapolation retrieves the wave response between two points by combining observed data with an extrapolator that describes the response between the subsurface and the data boundary when the source point is outside a target volume either forward time

18 o modelling of freshwater inputs in baffin bay and canadian arctic coastal waters 18o salinity modelling of marine environments has been proposed for various areas including some arctic seas the present report concerns arctic coastal waters collected along the west coast of greenland northern baffin bay the arctic archipelago and the north shore of alaska measurements of 18o versus salinity allow the identification of three main components marine standard water continental freshwater and sea ice meltwater continental waters may be represented by either glacial meltwater western greenland land drainage mackenzie areas or both quantitative determinations of the respective parts involved in mixed coastal waters imply a precise knowledge of the isotopic characteristics of the local continental waters these determinations may be achieved either numerically or graphically

extending illumination using all multiples application to 3d acquisition geometry analysis recent advances in survey design have led to conventional common midpoint based analysis being replaced by subsurface based seismic acquisition analysis with emphasis on advanced techniques of illumination analysis among them is the so called focal beam method which is a wave equation based seismic illumination analysis method the objective of the focal beam method is to provide a quantitative insight into the combined influence of acquisition geometry overburden structure and migration operators on the resolution and angle dependent amplitude fidelity of the image the method distinguishes between illumination and sensing capability of a particular acquisition geometry by computing the focal source beam and the focal detector beam respectively sensing is related to the detection properties of a detector configuration whereas illumination is related to the emission properties of a source configuration the focal source beam analyses the incident wavefield at a specific subsurface grid point from all available sources whereas the focal detector beam analyses the sensing wavefield reaching at the detector locations from the same subsurface grid point in the past this method could only address illumination by primary reflections in this paper we will extend the concept of the focal beam method to incorporate the illumination due to the surface and internal multiples this in fact complies with the trend of including multiples in the imaging process multiple reflections can illuminate a target location from other angles compared with primary reflections resulting in a higher resolution and an improved illumination we demonstrate how an acquisition related footprint can be corrected using both the surface and the internal multiples

paleo oceanographie isotopique des mers post glaciaires du quebec abstract the main hydrological characteristics of the post glacial seas of quebec the gold thwait champlain iberville tyrrell seas and the gulf of laflamme have been investigated by a determination of the isotopic composition 14 c 13 c 18 o of the fauna and sediments of their basins the carbonates are generally depleted in 18 o specially shallow water mollusks which show isotopic compositions as low as pdb 18 o 15 the depletion in heavy isotopes is mainly related to the influx of continental waters particularly glacial meltwater in such basins the isotope geochemistry differs from what is observed in open environments and therefore the standard isotopic paleotemperature technique may not be used directly new data on the isotopic composition of glacial lakes and melting water of the laurentide ice sheet compared with data from present arctic environments have enabled us to calibrate a linear 18 o salinity relationship and to evaluate salinity changes in time and space it is concluded that the present marginal basins of quebec do not show any large differences in either salinity or temperature from the post glacial basins more brackish water has characterized the surficial layers since deglaciation shoaling of the basins due to glacio isostatic rebound later induced local variations in the temperature and salinity the water becoming progressively warmer and more brackish in these basins the geochemistry of carbon is more complex the in situ biological production of co 2 caused large variations in the 13 c content of the carbonates independently of any direct continental influence the observed anomalies in 14 c activity of fossil mollusks are believed to be related to the old water effect and to local influx of dead carbon originating from dissolution by ice meltwater of surrounding carbonate bearing bedrock

parent material controlled subsoil weathering in a chronosequence the allier terraces limagne rift valley france abstract the chronosequence in the allier terraces is subject to erratic changes in parent material composition with time approximately 65 of the total variance in the basaltic elements content in the allier terrace sands can be explained by the combined effect of parent material and time related neoformation of clay in the subsoil it is shown that parent material composition as a function of transport distance strongly influences weathering rate in the allier terrace chronosequence in order to evaluate parent material controlled weathering effects a process model simulation was made based on an exponential decrease of mgo and neoformation of clay long term simulations with this model suggest that parent material controlled subsoil weathering is significant for sediments with easy weatherable fragments after prolonged weathering the role of parent material decreases and becomes untraceable in strongly weathered materials

elastic p and s wave autofocus imaging with primaries and internal multiples conventional seismic imaging methods rely on the singlescattering born approximation requiring the removal of multiply scattered events from reflection data prior to imaging additionally many methods use an acoustic approximation representing the solid earth as an acoustic fluid medium we have developed imaging methods for solid elastic media that use primaries and internal multiples including their ps and sp conversions thus obviating the need for internal multiple removal and improving handling of internal conversions our methods rely on the elastic autofocusing method which estimates full multicomponent elastodynamic green s functions from virtual sources interior to the medium to receivers placed on the surface they require only surface seismic reflection data and estimates of the direct waves from virtual sources interior to the medium both of which are commonly available at the imaging step of seismic processing we tested our methods on a synthetic model with constant p and s velocities and vertical and horizontal density variations by producing for the first time to our knowledge pp and ss images from elastic autofocusing that are compared to reference seismic images based on conventional methods the effects of multiples are greatly attenuated in the images with fewer spurious reflectors than are observed when using born imaging

surface sediment diatom distribution and holocene paleotemperature variations in the greenland iceland and norwegian sea one hundred and four surface sediment samples and two piston cores from the greenland iceland and the norwegian gin sea hopkins 1988 were analyzed diatoms were common to abundant in most surface sediment samples and throughout the holocene q mode factor analysis allowed the definition of six significantly different floral assemblages which explained 91 7 of the total variance mapping of the six factors showed their close affinity to hydrographic regimes these are the norwegian atlantic current assemblage thalassionema nitzschioides paralia sulcata proboscia alata arctic water assemblage thalassiosira gravidaspores sea ice assemblage nitzschia grunowii nitzschia cylindra thalassiosira hyalina arctic norwegian waters mixing assemblage rhizosolenia hebetata f semispina rhizosolenia borealis atlantic assemblage thalassiosira oestrupii and norwegian arctic waters mixing assemblage thalassiosira gravida vegetative cells transfer functions gint2 relating factor distributions to winter february and summer august surface water temperatures were generated the transfer functions have a standard error of estimate of 1 5 c august and 1 0 c february downcore studies of core 52 43 from the norwegian basin and core 57 5 from the iceland plateau revealed diatom abundance and sea surface paleotemperature trends in the area during the holocene the first appearance of diatoms in cores 52 43 and 57 5 occurs within the vedde ash layer 10 600 years b p and the saksunarvatn ash layer 9100 years b p respectively diatom abundances increase steadily throughout the pre boreal atlantic time to 25 and 35 million valves per gram dry sediment in the norwegian basin and iceland plateau cores respectively application of the temperature transfer functions gint2 to the two holocene records revealed higher than present sea surface temperatures during the boreal atlantic chronozones for the iceland plateau and during the middle younger dryas sub boreal chronozones for the norwegian basin core temperatures decreased steadily since then with a slight increase to the present values both the iceland and the norwegian seas experienced a strong influx of temperate atlantic surface waters in the beginning of the holocene sea surface temperatures dropped steadily in the latter part of the holocene as the influx of the atlantic surface waters diminished

pedosedimentary history and floodplain dynamics of the lower cretaceous upper blairmore group southwestern alberta canada thick alluvial successions in the upper blairmore group in the foothills of southwestern alberta contain few well developed paleosol profiles but abundant evidence of pedogenic modification the pedogenically modified successions are characterized by vertical root traces compound illuvial clay coatings and ferruginous coatings and nodules five representative paleosol successions composed of nine microfacies are analyzed the paleosol successions indicate soil development on more or less continuously aggrading floodplains however locally rates of sedimentation and pedogenesis were highly variable the paleosol successions contain features similar to modern alluvial soils brunisols and luvisols vertical trends within individual paleosol successions preserve the changing paleoenvironmental record at each site the dynamic nature of the floodplain topography is reflected in alternating drainage conditions represented by quasi regular colour banding compound clay coatings and the type and degree of pedogenic development upwards within the paleosol successions overall the paleosols indicate soil development under a warm temperate paleoclimate with seasonal precipitation although representing minor diastems the paleosols formed contemporaneously with sedimentation and are an integral part of the alluvial successions local variations in paleosol development are attributed to variations in sediment supply and water table conditions related to the overall floodplain geomorphology

mineralogy and genesis of planosols under a semi arid climate borborema plateau ne brazil abstract planosols such as those found on the borborema plateau ne brazil form an important class of moderately weathered soils that support subsistence agriculture in underdeveloped regions of africa asia and south america despite its socioeconomic importance the genesis of this soil class has not yet been fully elucidated this study was conducted with the aim of improving knowledge about the genesis of planosols under a semi arid climate three planosol profiles on the borborema plateau in ne brazil were collected classified and described morphologically and the main physical and chemical attributes the pedogenetic forms of iron oxides and the mineralogical compositions of the sand silt and clay fractions were determined the results indicate that a parent materials richer in feldspar and biotite favor the formation of planosols with a higher clay content b the dissolution of primary minerals and the formation of clay minerals known as the argillation process are fundamental for the genesis of bt horizons c depth drainage deficiency leads to hydromorphism an associated gray color and the formation of mottles and d monosialitization and bisialitization processes kaolinite formation and the formation of 2 1 clay minerals respectively prevail in planosols located within landscape positions that have good and poor drainage respectively in addition the present study shows that planosols under a semi arid climate can have a clay fraction consisting predominantly of kaolinite and mineralogical alteration pathways similar to those described in soils under an analogous climate and geology in northwest africa this refutes classical theories that soils with 2 1 clay minerals prevail in warmer and drier regions this study thus provides greater knowledge about the attributes of planosols in dry and poor regions and can be used as a reference in studies on the sustainable use and management of such soils

genesis morphology and mineralogy of planosols developed from different parent materials in southern brazil abstract the genesis of planosols is a complex process since it can involve multiple cycles of soil formation deposition of allochthonous materials and also past climate changes furthermore this subject is still poorly studied in the humid tropics thus hindering a proper appraisal of the potentials and limitations of planosols the objective of this research was to study pedogenetic processes and properties of planosols formed from different parent materials in southern brazil four soils were sampled p1 hypereutric luvic albic planosol developed on lagoon plain sediments p2 orthoeutric luvic albic planosol on holocene alluvial deposits p3 hypereutric luvic albic planosol on granite and p4 orthoeutric luvic albic planosol on gneiss all planosols presented sandy horizons a and e with low ph

pedogenic properties of white clay soils of the three river plain heilongj iang province p r china abstract white clay soils are widely distributed in the heilongjiang province p r china and are of agricultural importance in the province however there is only limited information available on the characteristics and pedogenesis of these soils three representative pedons of white clay soils in the three river plain heilongjiang province were selected to determine physical morphological chemical and mineralogical properties and to relate these properties to the genesis and classification of these soils sr ti and zr were determined by x ray fluorescence to establish parent material uniformity clay minerals were identified by x ray diffraction methods micromorphology of the soils was based on petrographic examination of thin sections lithologic discontinuities were not detected based on the coefficients of variability associated with ratios of zr sr and ti zr within pedons the profiles are characterized by a mollic epipedon an albic e horizon and a thick argillic horizon physical morphological chemical and mineralogical properties indicate that lessivage was a dominant pedogenic process pedogenic fe mn nodules occur in ah and e horizons maximum contents of pyrophosphate extractable fe and al and oxalate and dithionite extractable al occur in bt2 horizons the soils have relatively uniform ph values of about 4 5 5 0 soil vermiculite which had not previously been recognized is common in the clay fraction the clay mineral assemblage is qualitatively similar throughout profiles continuous addition of aerosolic dust rich in mica and lessivage contributed to the quantitative variation in clay minerals within the pedon the white clay soils are classified as mollic planosols in the fao unesco system and typic argialbolls in soil taxonomy

holocene boreal molluscs in greenland palaeoceanographic implications abstract boreal molluscs now extinct in greenland waters occur as subfossils in west greenland between lat 65 30 and 68 30 n a number of new localities for these warmth demanding molluscs are described and the list of species now comprises the gastropod emarqinula fissura and the bivalvalves heteranomia squamula modiolus arctica islandica panopea norvegica and zirphaea crispata during their time the molluscs formed an isolated northern outpost located in the area which as a result of the complex oceanic circulation today has greenland s highest ocean surface temperatures the occurrences are 14c dated to the interval 8400 4900 yr b p and summer surface temperatures were 1 3 c higher than now for its beginning this period coincides with similar marine optimal periods in east greenland and on the baffin island shelf whereas it took 1000 years before the beginning of warmer than present temperatures on land on the basis of this evidence it is concluded that the rise of sea surface temperatures was afforded by a decrease in inflow of cold polar water and or increase in inflow of warm atlantic water into davis strait rather than climatic change

stable isotope and minor element proxies for eocene climate of seymour island antarctica 1 abundant and well preserved marine macrofossils on seymour island antarctica provide a valuable resource to establish paleoenvironmental conditions at high southern latitudes during the warm paleogene stable isotope minor element and 8 7 sr 8 6 sr compositions have been measured for the aragonite bivalve cucullaea from the eocene la meseta formation the 8 7 sr 8 6 sr stratigraphy suggests an early to late eocene age for the la meseta formation sea surface temperature estimates based on 1 8 o values range from 14 5 to 15 5 c in the early and middle eocene to 10 5 c in the late eocene high resolution sampling along growth structures provides estimates of seasonality in temperature which decrease considerably up section to address the relative contribution of temperature and ice volume or salinity to the 1 8 o record sr ca was measured and evaluated as a potential independent paleothermometer for cucullaea

strontium and oxygen isotopic composition of east greenland rivers and surface waters implication for palaeoenvironmental interpretation abstract isotopic composition of strontium and oxygen and strontium concentrations from 4 hydrographic sites in scoresby sund fjord and 6 rivers draining the adjacent jameson land have been investigated schuchert flod the major river on jameson land erodes a large celestite srso4 deposit dissolved sr in schuchert flod has 87sr 86sr 0 7137 and is responsible for most of the continental sr flux to the fjord the sr isotope data have been used to construct a mixing model for the surface water in scoresby sund fjord salinity s and sr concentrations csr of brackish water from the fjord show conservative mixing between river water and seawater results of the 87sr 86sr salinity mixing model of seawater and fresh water were used to interpret the isotopic composition of sr 87sr 86sr and oxygen 18oc of recent and interglacial eemian 120 ka shallow water bivalve shells from the coast of jameson land because of the high csr in some of the rivers draining jameson land a correlation exists between 87sr 86sr and 18oc of recent and interglacial shallow water bivalve shells from the coast of jameson land higher than seawater 87sr 86sr values in shells from the langelandselv interglaciation can be explained only if the shells were formed close to a sr rich fresh water source which is not present in the langelandselv area today these results suggest that there was a different river and drainage system on the jameson land peninsula during the last interglacial the 87sr 86sr values indicate that shell formation took place in waters with salinities between 20 and 31 in a fjord with less glacial melt water than seen today

lithospheric architecture of the south western alps revealed by multiparameter teleseismic full waveform inversion the western alps although being intensively investigated remains elusive when it comes to determining its lithospheric structure new inferences on the latter are important for the understanding of processes and mechanisms of orogeny needed to unravel the dynamic evolution of the alps this situation led to the deployment of the cifalps temporary experiment conducted to address the lack of seismological data amenable to high resolution seismic imaging of the crust and the upper mantle we perform a 3 d isotropic full waveform inversion fwi of nine teleseismic events recorded by the cifalps experiment to infer 3 d models of both density and p and s wave velocities of the alpine lithosphere here by fwi is meant the inversion of the full seismograms including phase and amplitude effects within a time window following the first arrival up to a frequency of 0 2 hz we show that the application of the fwi at the lithospheric scale is able to generate images of the lithosphere with unprecedented resolution and can furnish a reliable density model of the upper lithosphere in the shallowest part of the crust we retrieve the shape of the fast dense ivrea body anomaly and detect the low velocities of the po and se france sedimentary basins the geometry of the ivrea body as revealed by our density model is consistent with the bouguer anomaly a sharp moho transition is followed from the external part 30 km depth to the internal part of the alps 70 80 km depth giving clear evidence of a continental subduction event during the formation of the alpine belt a low velocity zone in the lower lithosphere of the s wave velocity model supports the hypothesis of a slab detachment in the western part of the alps that is followed by asthenospheric upwelling the application of fwi to teleseismic data helps to fill the gap of resolution between traditional imaging techniques and enables integrated interpretations of both upper and lower lithospheric structures

oxygen and carbon isotope composition of quaternary bivalve shells as a water mass indicator last interglacial and holocene east greenland abstract oxygen and carbon isotope composition of arctic bivalve shells are used in an attempt to reconstruct surface water temperature and salinities in scoresby sund east greenland the oxygen isotope compositions of mya truncata hiatella arctica and tridonta borealis have been compared with present day hydrological parameters modern shells yield oxygen isotope values that on the whole reproduce the environmental temperature and sea water isotopic composition furthermore it is possible to estimate the living depth of the analysed specimens analyses of growth increments from single shells show that there are large variations from year to year in temperature and oxygen isotope composition of the surface waters of scoresby sund and that these variations decrease with depth analyses of holocene shells indicate that the polar current water which flows from north to south along the east greenland coast was also present during the holocene climatic optimum 8000 7000 yr b p analyses of bivalve shells from the last interglacial show that scoresby sund during that time was well circulated and that meltwater from the greenland ice sheet and sea ice meltwater was important for the temperature salinity and isotopic composition of the surface waters

element partitioning in sediment soil and vegetation in an alluvial terrace chronosequence limagne rift valley france a landscape geochemical study abstract the geochemical behaviour of specific elements in fluvial sediments topsoils soil profiles and plant material on a sequence of quaternary alluvial terraces was reconstructed semi quantitatively using indices of accumulation or depletion with respect to abundance in the lithosphere local soils and sediments topsoils of different ages and soil profiles are most clearly differentiated by the degree of leaching of ca mg and some minor elements with respect to less mobile si and ti clay translocation within soil profiles of older terraces leads to accumulation of al and associated elements in deeper horizons and accumulation of fe and mn in pseudogley horizons in the upper part of the clay accumulation layers p k ca mn and zn are strongly concentrated in plant materials relative to the topsoils ca is accumulated more strongly in oak bark than in grasses and the relative accumulation is greater on the older terraces due to the low ca content in their topsoils mn contents of both grasses and oak bark are greater on the older terraces than the younger for most elements topsoil and plant material contents show little correlation probably because plant requirements exert a greater control on element uptake than does availability the results illustrate that landscape geochemical analysis is useful for rapid appraisal of long term landscape processes such as erosion sedimentation weathering and preferential plant uptake

arctic ocean water mass balance from isotope data the distributions of the oxygen 18 and tritium isotopes and of salinity yield a residence time of 10 years for the surface and halocline waters of the arctic basin we find a yearly net production of 0 59 m of sea ice and an input of 1 16 m of freshwater from continental river runoff local precipitation and bering strait salinity deficiency using the basin area value with these numbers gives long term average total net production and transport rates of 0 15 sv of ice and 0 18 sv of meteoric component bering strait water not included if in addition a reasonable depth profile of relative current velocity is assumed for the outflow a yearly input of 2 8 sv of atlantic and bering strait water is needed to replenish the upper and halocline waters these numbers should be good to 20 and are multiyear averages the isotope data clearly indicate that the barents sea is an inflow area for atlantic water to the basin but that net export of ice occurs there

stable isotope profiles of last interglacial pelukian transgression mollusks and paleoclimate implications in the bering strait region abstract the marine paleoclimate during the last interglaciation in the bering strait region is inferred from the stable oxygen and carbon isotope profiles of fossil bivalve mollusks specimens were collected from the marine highstand deposits of the pelukian transgression from the arctic alaskan coastal plain the nome coastal plain st lawrence island and the val katlen suite on the chukotka peninsula as a calibration modern mollusks were obtained from the major water masses in the bering chukchi seas system and from coastal environments near the fossil localities the 18 o composition of the modern mollusks accurately reflects the seawater 18 o differences among the water masses and the ambient temperature range at each site seasonal paleotemperature ranges are estimated from the 18 o profiles of the fossils by comparison with those of the modern specimens a simple model is developed to correct the paleotemperature ranges for the influence of differences in seawater 18 o between water masses and seasonal variations caused by freshwater discharge paleotemperatures calculated for the skull cliff site alaskan arctic coastal plain are close to but slightly cooler than those of modern specimens from peard bay and icy cape the isotopic composition of a pelukian specimen collected near wainwright shows the obvious influence of locally reduced salinities with a correction for lower seawater 18 o this profile yields a summer temperature of 13 c which is 3 c warmer than that from the modern icy cape specimen the isotope records of two specimens from the nome coastal plain suggest salinities that were 3 5 psu lower than the modern eastern bering shelf the paleotemperature range of 0 15 c is consistent with modern conditions in norton sound the character of the isotope profiles of the pelukian specimens from st lawrence island is very different than that of modern specimens near the island but matches the 18 o values of shells from deeper sites in anadyr water this suggests that the fossil mollusks were living in anadyr strait and were transported by a glacial advance from the chukotka peninsula the last interglacial specimens from the val katlen suite have isotope profiles with large seasonal 18 o ranges and the clear influence of a reduced salinity coastal water mass calculated paleotemperatures from the val katlen specimens range from 0 to 13 c differences in the 13 c of shell carbonate between sites appears to reflect the regional distribution of the 13 c of sedimentary organic matter som which is a mixture between terrestrial organic matter mean 13 c of 24 and marine phytoplankton 21 partitioning of 13 c between shallow and deep waters by phytoplankton productivity and remineralization may also affect the regional distribution differences in shell 13 c between taxa may relate to feeding mode and the type and isotopic composition of ingested particles the filter feeders mya and astarte typically have 13 c values 1 2 more positive than the deposit feeders macoma and serripes this effect is attributed to a 13 c difference between marine phytoplankton and som with a component of terrestrial organic carbon

recent freshening in the kara sea siberia recorded by stable isotopes in arctic bivalve shells oxygen and stable carbon isotope records along the growth direction on shells of the bivalve species astarte borealis and serripes groenlandicus reliably record all important aspects of the bottom water hydrography in the shallow southeastern kara sea despite uncertainties about the isotopic range due to sparse sampling and the possibility of growth rate changes changing freshwater supply from the rivers ob and yenisei is the main cause for seasonal temperature and salinity variations near the three sampling locations in 20 to 70 m water depth as suggested by ctd measurements and modeling peak winter salinity of the simulated hydrographic data series and peak winter values in the isotope records follow negative trends which indicate a freshening of the bottom water due to an increasing fraction of river water during the 1990s this freshening affected the whole kara sea and coincided with a lowering of regional air pressure gradients as indicated by the declining arctic oscillation index the resulting weakening of the prevailing southwesterly winds diminished the inflow of saline atlantic derived water from the barents sea through the kara strait in the southwest and additionally reduced the export of river water toward the north and northeast into the arctic basin saline atlantic derived water thus was replaced by freshwater which was successively accumulated in the kara sea and accordingly imprinted on the stable isotope composition of the bivalve shells the 1990s freshening in the kara sea thus may be caused by natural variations rather than being a signal for global change

holocene environmental history of western ymer o east greenland inferred from lake sediments abstract sediment records from two adjacent lakes on western ymer o east greenland were investigated for chronology lithology biogeochemistry palynology and marine fossils the data indicate that lowland deglaciation in this interior coastal region has commenced prior to 10 000 cal yr bp this suggests a rapid ice retreat after the milne land stade deglaciation was followed by a marine inundation that peaked out between 60 and 120 m above the modern sea level the middle holocene uplift rate in this interior region of east greenland probably was lower and more constant than assumed by previous investigations and as in the central and outer coastal areas the climatic development during the past 8000 years on western ymer o was characterized by an early holocene temperature optimum and a subsequent cooling that culminated during the little ice age the long term temperature changes however had relatively little effect on size variations of a local ice cap that persisted throughout the holocene on northwestern ymer o oscillations reconstructed for this ice cap are due to changes in precipitation

geologic model building in seam phase ii land seismic challenges three digital earth models were designed and constructed during seam phase ii to study exploration challenges at the scale of modern land seismic surveys although built as generic models each was based on one or more related geologic type areas the barrett model represents the seismic anisotropy of complex laminated and fractured shale reservoirs based on the woodford and eagle ford formations and set below a stratigraphic overburden and near surface of a north american midcontinent basin the arid model features the extreme property contrasts of desert terrains in a 500 m thick near surface that juxtaposes hard carbonate bedrock and soft sediments filling karsts typical of the saudi arabian peninsula the foothills model contains sharp surface topography and alluvial fan like sediments above complex fold and thrust structures based on the compressive tectonics of the llanos foothills of south america all three models were built in workflows that combined automated steps with a large measure of manu

hydromorphic and clay related processes in soils from the llanos de moxos northern bolivia abstract the llanos de moxos is one of the largest wetlands in the world more than 100 000 km2 due to seasonal floods the soil parent materials are fine quaternary sediments brought by tributaries of the amazon river forests cover some areas although the dominant vegetation is a pastured savannah and backswamps at present the main land use is a very extensive rangeland and slash and burn agriculture in minor areas we have studied 15 profiles from several sample areas between trinidad and san ignacio field and laboratory studies have been carried out in order to elucidate the soil forming processes taking place and to gain basic knowledge for a sustainable land management coarser soils are located near the present river system or in former riverbank areas often under forest textures here are loam or silty loam silty clay loam being dominant finer soils may have up to 85 clay and are usually under savannah cover illite is the dominant clay mineral in all soils followed by smectite and kaolinite vermiculite is absent quartz is present in a very significant amount in the clay fraction of all studied soils goethite and lepidocrocite are present in all soils lepidocrocite being a good indicator of poor drainage conditions soils are mainly acid but there are soils with calcium carbonate accumulation in the subsoil or even saline soils salitrales soils are flooded for a significant period 3 6 months and bypass flow is very active hydromorphic processes are always present and morphologies include hard and soft iron manganese concretions with diffuse boundaries within peds impregnative fe coatings and fe depletion hypocoatings along pore walls the micromorphological study shows different degrees of hydromorphism some of them associated to the present pore system and some with a palaeo character often disturbed by active slickensides microsparite nodules are also present in some low lying soils the soils present several morphological features related to the mobility of the fine fraction that can be related to drainage conditions as recent clay coatings clay and silt infillings and coatings and clay depleted hypocoatings the most clayey soils show striated b fabrics and frequent slickensides and some others point to ferrolysis as iron depleted hypocoatings and low crystallinity clay coatings along pores although this is not supported by mineralogical data a moderate cation supply probably prevents strong acidification

holocene glacimarine sedimentation inner scoresby sund east greenland the influence of fast flowing ice sheet outlet glaciers abstract holocene glacimarine sedimentation associated with fast flowing outlet glaciers draining the greenland ice sheet is investigated using sedimentary and acoustic data from inner scoresby sund east greenland sedimentation in inner scoresby sund is dominated by three processes which are influenced by differences in proximity to fast flowing outlet glaciers extent of glacier ice cover and fjord bathymetry 1 sediment gravity flow principally in the form of turbidity currents and debris flows 2 suspension sedimentation from turbid meltwater plumes and 3 iceberg rafting these processes result in texturally and sedimentologically heterogeneous lithofacies proportionally fine grained muds laminated stratified and massive facies dominate cores recovered from inner scoresby sund accounting for 80 of the total whereas diamict facies account for only 15 abundant fine grained muds demonstrate that meltwater flux and sedimentation is significant in this high arctic glacimarine environment in settings proximal to fast flowing outlet glaciers with increasing distance from these glacier termini muds are replaced progressively by iceberg rafted coarse grained sediment the dominance of this iceberg rafted sediment in outer scoresby sund reflects both its more distal location from fast flowing glacier termini and the high calving flux associated with these ice masses laminated muds deposited by turbidity currents and suspension settling from overflow plumes in inner scoresby sund are similar to lithofacies produced in temperate and subpolar glacimarine systems this implies a similarity in sedimentation processes and resulting facies across a wide spectrum of climatically glaciologically fast flowing and non fast flowing ice masses and oceanographically variable glacimarine settings recognition of laminated fine grained facies in the geological record therefore does not necessarily indicate a temperate palaeo glacial setting however the predominance of iceberg rafted diamict facies in ice distal sedimentary records suggests the former presence of relatively cold environmental conditions in which iceberg sedimentation played a dominant role

volumetric wavefield recording and wave equation inversion for near surface material properties volumetric recording of the seismic wavefield implies that the local receiver group or array approximately encloses a volume of the earth we show how volumetric recording can be used to measure several spatial derivatives of the wavefield by making use of the full elastic wave equation the free surface condition on elastic wavefields and derivative centering techniques analagous to lax wendroff corrections used in synthetic finite difference modeling these derivative estimates can be inverted for p and s velocities in the near surface directly beneath the receiver group the quantities estimated are the effective velocities of the p and s components experienced by the wavefield at any point in time hence the velocity estimates may vary with both wave type and wavelength the estimates may be useful to aid statics estimation and are exactly the effective velocities required for separation of the wavefield into p and s and up and down going components

holocene hydrographical changes of the eastern laptev sea siberian arctic recorded in δ18o profiles of bivalve shells oxygen isotope profiles along the growth axis of fossil bivalve shells of macoma calcarea were established to reconstruct hydrographical changes in the eastern laptev sea since 8400 cal yr b p the variability of the oxygen isotopes 18o in the individual records is mainly attributed to variations in the salinity of bottom waters in the laptev sea with a modern ratio of 0 50 salinity the high resolution 18o profiles exhibit distinct and annual cycles from which the seasonal and annual salinity variations at the investigated site can be reconstructed based on the modern analogue approach oxygen isotope profiles of radiocarbon dated bivalve shells from a sediment core located northeast of the lena delta provide seasonal and subdecadal insights into past hydrological conditions and their relation to the holocene transgressional history of the laptev sea shelf under the assumption that the modern relationship between 18ow and salinity has been constant throughout the time the 18o of an 8400 cal yr old bivalves would suggest that bottom water salinity was reduced and the temperature was slightly warmer both suggesting a stronger mixture of riverine water to the bottom water reconstruction of the inundation history of the laptev sea shelf indicates local sea level 27 m below present at this time and a closer proximity of the site to the coastline and the lena river mouth due to continuing sea level rise and a southward retreat of the river mouth bottom water salinity increased at 7200 cal yr b p along with an increase in seasonal variability conditions comparable to the modern hydrography were achieved by 3800 cal yr b p

properties and genesis of argialbolls in the usa abstract the presence of an albic horizon below a mollic epipedon has long puzzled pedologists the purpose of this study was to utilize data from the natural resources conservation service nrcs databases and the published literature to develop a weight of evidence assessment of how albolls form in the usa there are 69 albolls soil series in the nrcs database all of which are argialbolls these soils contain horizons with the following mean thickness and standard deviation mollic epipedon 29 11 cm albic 18 9 cm and argillic 75 37 cm argialbolls comprise 18 078 km2 in the usa 0 02 of total land area 70 of which occur in north dakota south dakota missouri and iowa argialbolls are somewhat poorly drained poorly drained or very poorly drained 78 and 81 of the argialbolls are very deep 1 5 m silty alluvium and loess comprise 86 of the parent materials the dominant vegetation is grassland 64 sedges 16 or savanna 16 ninety percent of the argialboll soil series are in the fine or fine silty particle size classes 62 have a mesic soil temperature regime 36 have an aquic soil moisture regime and 64 have a smectitic soil mineral class the argialbolls have formed under modern conditions where development of a smectitic rich argillic horizon has led to reducing conditions during which fe and mn concentrate as concretions in the albic horizon that underlies the mollic epipedon

ikaite tufa towers in ikka fjord southwest greenland their formation by mixing of seawater and alkaline spring water abstract ikka fjord in southwest greenland is the type locality for ikaite a metastable hexahydrate of calcium carbonate here ikaite forms submarine tufa columns rising up to 18 m above the fjord bottom the columns are spectacular examples of abiogenic carbonate precipitation in a cold seawater environment and so far represent the only known formation of ikaite in seawater we have analyzed the 2h 13c 14c 18o and 87sr contents and major element and minor element compositions of ikaite and of the different water types in and around ikka fjord in order to understand the formation of the ikka columns water from inside the columns is fresh but alkaline rich in ions of sodium bicarbonate and carbonate and has a stable isotope composition identical to precipitation falling on the nearby gronnedal ika igneous complex and we conclude that the tufa columns form over submarine springs issuing from the bottom of ikka fjord dissolution of unidentified sodium carbonate minerals in carbonatites in the igneous complex probably accounts for the peculiar chemistry of the springs ikaite supersaturation and precipitation is controlled by mixing of spring water and seawater at the cold 6 c fjord bottom and precipitation is accelerated by the formation of hydrated caco3o aq ion pairs while phosphate ions in the spring water act as inhibitor for precipitation of anhydrous carbonates we propose that the spring water seeps in ikka fjord literally create their own conduits in the form of the vertical chimney like columns with ikaite forming continuously at the tops of the columns the only limits to upward growth are winter ice and the fresh water layer capping the fjord during summer

shells of the bivalve astarte moerchi give new evidence of a strong pelagic benthic coupling shift occurring since the late 1970s in the north water polynya climate changes in the arctic may weaken the currently tight pelagic benthic coupling in response to decreasing sea ice cover arctic marine systems are expected to shift from a sea ice algaebenth

oxygen isotope composition and rate of growth of patella coerulea monodonta turbinata and m articulata shells from the western coast of sicily abstract the oxygen isotope composition of carbonate from the outermost portions of patella coerulea monodonta turbinata and m articulata shells has been measured from april 1979 to july 1981 with an interval during the summer of 1980 and correlated with the ambient temperature carbonate from m turbinata has yielded values that on the whole reproduce the environmental temperature range acceptably p coerula and m articulata indicate precipitation taking place at temperatures lower than those measured in seawater this is particularly acceptuated in summer this pattern does not necessarily exclude shell carbonate from precipitating under equilibrium conditions with seawater rather it indicates a higher calcification rate in medium warm periods for m turbinata with slower precipitation in winter and in medium cold periods for p coerulea and m articulata with slow calcification and even short interruptions during the warmest spells in summer

soil formation in a quaternary terrace sequence of the allier limagne france macro and micromorphology particle size distribution chemistry abstract soil formation in a terrace chronosequence of nine gravelly quaternary terraces was studied based on macro and micromorphological mineralogical chemical and physical characteristics based on textural characteristics the c horizon of the youngest soil appears to be representative for the parent material of lower b and c horizons in the youngest soils and of all horizons in older soils the parent materials contain a volcanic and a granitic component with increasing age of soils the following stages of soil formation were observed holocene soils on lowest terraces show evidence for mixing of sedimentary layers by biological activity resulting in texturally homogeneous a and b horizons in the absence of periglacial processes soil formation in holocene and in late pleistocene terraces took place under continuously well drained conditions late pleistocene soils on higher terraces show effects of clay illuviation with prominent weathering features in a horizons middle and early pleistocene soils on the highest terraces were influenced by periglacial conditions and display effects of various cycles of soil forming processes alternated with periglacial processes increasing in complexity with age weathering of all minerals except quartz neoformation of clay and clay illuviation has resulted in distinct differentiation between sandy a and e horizons and a clayey b horizon periglacial processes during the quaternary weathering clay formation and clay illuviation have caused a considerable compaction and decreased water permeability this has resulted in imperfect drainage now reflected by abundant locally cemented iron and manganese oxide segregations in the surface horizon typical for surface water gley with evidence of ferrolysis ferrolysis the increased weathering of clay under influence of alternating oxidation reduction in the seasonally waterlogged surface soil may have further contributed to the marked textural change between a and e versus b horizons easily weatherable minerals observed in strongly leached surface layers of older end members of the terrace sequence might be attributed to aeolian volcanic inputs the holocene and late pleistocene soils are intensively used as arable land as a result of the continuously well drained conditions on account of the poor drainage the middle and early pleistocene soils are used mainly for grassland and forest

ice sheet and ocean interactions margin of the east greenland ice sheet 14 ka to present diatom evidence seven marine sediment cores were collected from the kangerdlugssuaq trough off the southeast coast of greenland the trough cuts across the continental shelf from the fjord mouth to the upper slope in denmark strait and provides a sedimentary environment sheltered from the east greenland current flowing along the shelf the cores have been 14c dated accelerator mass spectroscopy dates and analyzed for diatom accumulation rates and changes in floral composition it was found that the shelf probably was not glaciated by grounded ice but occupied by an ice shelf and or permanent sea ice between 14 000 years b p and the present average retreat rates of glacial permanent sea ice were circa 60 m yr between circa 13 500 and 11 000 years b p the retreat rates increased to about 150 m yr between 11 000 to 10 000 years b p the increase is unexpected because this correlates with fairbanks 1989 projected low glacial meltwater discharge for the same time which is coeval with the younger dryas several events of sea surface warming cooling took place on the outer shelf from 12 000 to 9000 years b p followed by cooling to the present with a possible warming between 3000 4000 years bp on the inner shelf pulses of warm cool surface water occurred from 9000 to 6000 years b p which was succeeded by surface water cooling until present

carbon and oxygen stable isotope values in shells of mytilus edulis and modiolus modiolus from holocene raised beaches at the outer coast of the varanger peninsula north norway the amplitudes of isotopic temperatures based on the stable isotope values of the calcite in profiles from shells of mytilus and modiolus from holocene raised beaches earlier dated and in recent modiolus shells were shown to correspond to the observed annual amplitude of the surface water in the area the relation between 13c and 18o values shows that the ocean water has been mixed with fresh water from the rivers at the coast where the molluscs lived the isotopic temperatures were therefore based on this ratio no clear differences in annual temperatures could be demonstrated within the period studied of about 4500 years

genesis of two planosols in the massif central france abstract two planosols developed on gravelly quaternary sediments of the river allier in the limagne rift valley massif central france were studied parent material contained in addition to a granitic component large amounts of volcanic particles morphological chemical mineralogical and physical properties of both profiles were investigated to indicate some of the changes which have taken place during pedogenesis both profiles were characterized by pronounced textural contrasts between sandy a and e horizons and clayey b horizons soil formation rather than a transient depositional environment is thought to be responsible for this marked textural change clear dissolution features of all mineral grains except quartz and increasing amounts of volcanic fragments with depth suggested weathering increasing ratios of mobile basic cations to tio 2 with increasing depth corroborated this observation the presence of non laminated isotropic and anisotropic limpid clay coatings were also evidence of in situ mineral weathering in both profiles kaolinite predominated as clay mineral and increased towards the surface micromorphological observations of microlaminated dusty and impure clay coatings in b horizons of both profiles were clear signs of clay illuviation bulk densities were high in lower e horizons and upper b horizons field observations and micromorphological data showed clear signs of periglacial features the combination of pedogenic and periglacial processes has apparently lead to a considerable compaction abundant cemented iron and manganese features predominantly occurring in e horizons suggested surface water gleying micromorphological observations of illuviation coatings in b horizons and of fine material in a and e horizons demonstrated grainy aspects suggesting ferrolysis