early diagenesis in deep sea turbidites the imprint of paleo oxidation zones sediment cores up to 35 m long have been recovered from turbidite sequences in the madiera abyssal plain and the southern nares abyssal plain detailed geochemical analyses of these sediments si al fe mn ca organic and inorganic carbon and associate pore waters nitrate ammonia silicate fe2 mn2 and alkalinity provide representative profiles of both steady state and nonsteady state diagenetic reactions initiated by oxidation and reduction processes models demonstrate that chemical transport in the pore water system is diffusion dominated over periods of a few thousands of years to several hundreds of thousands of years mn and fe mobilized in the subsurface mildly reducing sediments are precipitated as easily reducible oxyhydroxides in the near surface oxidized sediments nonsteady state profiles show the influence of episodic and rapid turbidite deposition and the imprint of oxidation zones that developed as the result of oxygen diffusion into the upper portions of turbidites during intervals of slow pelagic deposition the time required for development of oxidation zones between turbidites ranges from 2 0 to 15 ka in the madeira abyssal plain and from 0 2 to 2 4 ka in the southern nares abyssal plain paleo oxidation zones can be recognized in old turbidites by distinct changes in color between lower and upper portions of the deposit in the basal unoxidized portion of the turbidite the sediments are characteristically dark green gray or brown in the paleo oxidized zone the sediments are pale green blue or yellowish brown these zones in both the madeira and southern nares abyssal plains contain distinctly less organic c and carbonate in the paleo oxidized zone as compared with the unoxidized sediments depletion of carbonate content in the oxidized zones in the southern nares abyssal plain is particularly significant in that as much as 80 of the initial carbonates have been lost also the relative amounts of weak acid soluble fe and mn are generally less in the paleo oxidized zones due to the initial oxidation of metal carbonate and metal hydroxide forms to easily reducible oxide forms which are then subsequently solubilized under the mildly reducing conditions at depth in the sediment column

sandy contourite drift in the late miocene rifian corridor morocco reconstruction of depositional environments in a foreland basin seaway abstract the rifian corridor was a seaway between the atlantic ocean and the mediterranean sea during the late miocene the seaway progressively closed leading to the messinian salinity crisis in the mediterranean sea despite the key palaeogeographic importance of the rifian corridor patterns of sediment transport within the seaway have not been thoroughly studied in this study we investigated the upper miocene sedimentation and bottom current pathways in the south rifian corridor the planktic and benthic foraminifera of the upper tortonian and lower messinian successions allow us to constrain the age and palaeo environment of deposition encased in silty marls deposited at 150 300 m depth there are i 5 to 50 m thick mainly clastic sandstone bodies with unidirectional cross bedding and ii 50 cm thick mainly clastic tabular sandstone beds with bioturbation mottled silt lack of clear base or top and bi gradational sequences furthermore seismic facies representing elongated mounded drifts and associated moat are present at the western mouth of the seaway we interpret these facies as contourites the products of a westward sedimentary drift in the south rifian corridor the contourites are found only on the northern margin of the seaway thus suggesting a geostrophic current flowing westward along slope and then northward this geostrophic current may have been modulated by tides by comparing these fossil examples with the modern gulf of cadiz we interpret these current dominated deposits as evidence of late miocene mediterranean overflow into the atlantic ocean through the rifian corridor this overflow may have affected late miocene ocean circulation and climate and the overflow deposits may represent one of the first examples of mainly clastic contourites exposed on land

reworked tsunami deposits by bottom currents circumstantial evidences from late pleistocene to early holocene in the gulf of cadiz abstract younger sand layers ysls have been identified in drill cores of a late glacial to early holocene muddy contourite succession from the gulf of cadiz in this study we evaluate the grain size characteristics of the ysl which display bi gradational grading with inverse grading from silt to fine or medium grained sand followed by normal grading from fine or medium grained sand to silt radiocarbon dating shows that the ysl formed at three distinct times 1 the bolling allerod sites u1387 and u1386 2 the younger dryas site u1390 and 3 the beginning of the boreal site u1389 ichnological analyses and radiocarbon dating of cores from drill site u1389c indicate that the ysls consist of reworked materials deposited at a high sedimentation rate the results of sedimentological analyses ichnological treatment spatial distributions and radiocarbon dating of the ysls suggest that the possibility of an origin of the ysls is tsunami related but later reworked by bottom current however the source areas of the sandy sediments remain unclear although our results show them to be variable and area dependent some sandy deposits are transported by the mediterranean outflow water mow from the proximal sector of the gulf of cadiz contourite depositional system cds which is close to the strait of gibraltar however in other cases it is more probable that local gravity flows which are the result of instability on adjacent margins provide the sandy material

trace fossils biology and taphonomy 1990 special topics in palaeontology 3 280 pp e17 95 pbk e40 00 hbk unwin hyman london isbn 004445 6867 pbk 3035 hbk

high resolution image treatment in ichnological core analysis initial steps advances and prospects abstract ichnological studies have become popular during the last decades particularly those associated with the development of two major concepts the ichnofacies model and ichnofabric approach they have driven ichnology into diverse fields of earth sciences including paleoecology sedimentology paleoceanography and basin analysis as well as applied fields for the oil and gas industry and aquifer characterization whereas early ichnological analyses focused on outcrops later the number of ichnological studies on well cores increased noticeably still ichnological research on cores is hampered by certain limitations i e mainly narrow exposed surface and the characterization of ichnological properties is complicated when cores are involved to facilitate ichnological analysis in cores from modern deposits several techniques among them x rays magnetic resonance and computed tomography have been used with the development of computer software a new high resolution image treatment has emerged as a powerful tool in different branches of ichnological studies especially for cores from modern marine deposits because applications are numerous and perhaps not familiar to all the scientific community this paper provides an overview of the usefulness of image treatment in ichnological analysis its first steps and subsequent development the novel techniques most recently used in the study of cores from modern marine deposits and some challenges for future research

applying deep learning for identifying bioturbation from core photos advances and availability of deep learning software have recently allowed the development testing and deployment of automated image classification schemes for sedimentary features from core images the development of these methods is especially relevant for extracting useful geological features from otherwise unused core photos this paper demonstrates and tests the use of a deep learning workflow for the automated extraction of bioturbation data from a core photo dataset the proposed workflow includes extracting image tiles from core photos along a grid and referencing each tile with collected sedimentary data each labeled image tile is then used as a training and testing input for a machine learning algorithm this method allows users to quickly generate thousands of labeled training images to demonstrate and test this workflow a dataset collected using pychno an open source software specifically designed to collect sedimentary data from core photos the resulting dataset comprising 13 545 tiles of 128x128 pixel resolution is used to train a deep learning algorithm to automatically predict if a core photo contains evidence of bioturbation the trained model was able to predict whether or not an image demonstrated evidence of bioturbation with up to 88 accuracy the workflow demonstrates one of many possible applications for automatically extracting biogenic or physical sedimentary structure data from core photos models built using this approach can be used to seed wells from a given area or interval which can therefore significantly increase the value of core photo datasets with relative ease

the spatial distribution and source of arsenic copper tin and zinc within the surface sediments of the fal estuary cornwall uk abstract estuarine sediments commonly form major sinks for contaminants released during industrial activity many industrial processes lead to the release of metals initially in solution which can then be adsorbed on to for example fe hydroxides or clay minerals however in the mining industry there are two major contaminant waste streams 1 metals discharged in solution via mine drainage and 2 particulate grains of the ore forming or related minerals released after ore processing the release of particulate waste can have a major long term impact on environmental geochemistry in this study we have mapped the distribution of arsenic copper tin and zinc within the surficial sediments of the fal estuary cornwall uk an area that drains a historically important polymetallic mining district there are clear spatial variations in the contaminants with the highest levels 2800 p p m as 5000 p p m cu 3000 p p m sn and 6000 p p m zn within restronguet creek on the western side of the estuary mineralogical studies show that small 20 m grains of detrital arsenopyrite chalcopyrite cassiterite and sphalerite are very abundant within the surface sediments most of the sulphide grains are fractured but mineralogically unaltered although some grains show alteration rims caused by oxidation of the sulphides the geochemistry and mineralogy are indicative of sediment supply from the discharge of particulate waste into the estuary during historical mining activity subsequently this particulate waste has been largely physically and biologically reworked within the surface sediments although considerable effort has been made to minimize contaminants released via mine drainage into the estuary the potential flux of contaminants present within the intertidal and subtidal sediments has not been addressed benthic invertebrates living within the area have adapted to be metal tolerant and it is likely that the dominant source of bioavailable metals is a result of alteration of the particulate mine waste present within the intertidal and subtidal sediments

the skaergaard layered series part vi excluded trace elements in contrast to the smooth trends of major elements and mineral principal minerals of the skaergaard layered series my purpose here is to examine the corresponding excluded compositions the excluded trace elements in the skaergaard layered series have an irregular distribution that does not conform to the elements and their relations to progressive differentiation of the skaergaard magma the principal conclusion that normal trends of rayleigh type fractionation their concentrations are about constant or even decline through the lower and middle will emerge is that the trends of enrichment of these elements differ markedly from those of the major elezones before increasing sharply to reach maximum concentrations 100 200 m above the sandwich horizon as in the case of ments possibly because their distribution was affected by a build up and eventual exsolution of volatile comincluded elements the relative concentrations of excluded elements in coexisting phases deviate widely from those predicted by exponents in the magma it will also be shown that the observed partition coefficients differ widely from those perimentally determined partition coefficients under presumed magmatic conditions this is seen most clearly in the immiscible predicted from experimental studies several earlier studies addressed various aspects of the melanogranophyres and conjugate ferrogabbros although the major elements conform to the experimentally determined relations for skaergaard trace elements haskin and his co workers haskin haskin 1968 paster et al 1974 were the first immiscible liquids the trace elements do not they follow a totally independent trend the abrupt increase in the concentrations of to attempt to reconcile the distribution of excluded trace elements with earlier interpretations of trace element excluded elements in the upper part of the intrusion could plausibly be attributed to an addition of new magma or to a density inversion behavior during crystallization and differentiation of the layered series other previous work has been sumthat resulted in upward migration of a late liquid or fluid but these possibilities are inconsistent with the compositional and spatial marized by wager brown 1968 and more recently by mcbirney 1996 1998a relations of the upper parts of the intrusion although a late residual liquid certainly migrated upward the most likely explanation for the structural form of the intrusion and its principal units illustrated in simplified form in fig 1 have already the observed distribution of excluded elements is that the partition coefficients were altered by volatile components which gradually been described at length mcbirney 1989 1995 1996 boudreau mcbirney 1997 mcbirney nicolas 1997 increased during the early stages of crystallization then began to exsolve near the top of the middle zone sonnenthal mcbirney 1998 and need not be repeated apart from minor differences noted in the appendix the distribution and selection of samples as well as the methods by which they have been analyzed are essentially the same as those described in part v of this

geochemical characteristics of contaminated surficial sediments in halifax harbour impact of waste discharge analyses of 274 surface sediment samples collected from halifax inlet between 1986 and 1990 permit assessment of the chemical environmental quality of this major east coast canadian harbour contamination of the marine sediments is due to discharge of untreated sewage and industrial waste directly into the harbour and leaching of solid waste deposits on land concentrations of total cu pb zn hg and cd in the uppermost 2 cm of sediments on the sea floor ranks halifax harbour among the most contaminated marine areas in the industrialized world statistical factor analysis has been used to identify five types of sediments based on sedimentological and geochemical characteristics the dominant factor type accounts for 41 of the chemical variance and represents sediments that are highly contaminated with metals and organics derived from sewage effluents and waste deposits more than 50 of the total cu zn and pb in the sediments is potentially reactive as reducible or oxidizable metal a simple two laye

the influence of dissolved fesi3o3 oh 08 on chemical equilibria in pore waters from deep sea sediments abstract pore water extracted from unconsolidated fine grained sediments from the southern sohm abyssal plain contain dissolved iron at concentrations greater than 100 m in glacial age sediments deeper than 2 0 m below the sea floor slightly reducing conditions pe and elevated dissolved sio 2 concentrations 300 m coincide with dissolved iron concentrations which are 2 to 4 orders of magnitude greater than would be predicted by conventional phase equilibria it is proposed that this fe exists in a fesi 3 o 3 oh 8 aq form and when its solubility is exceeded fe oh 3 or fesio 3 can be precipitated

the cumulate paradigm affirmed mcbirney and hunter s conclusion that the cumulate paradigm or theory is an impediment to progress is unjustified because they did not demonstrate that the original cumulate terminology cannot be adapted neither did they question the fundamental cumulate assumption of bottom upward solidification for many large mafic intrusions because the decoupling of mineral modal and whole rock chemical compositions may reflect either the failure of cumulate theory or may be an artifact of sampling of large mafic intrusions on scales smaller than the scale of the heterogeneities produced by the irregular distribution and migration of intercumulus liquids we conclude that a compelling case to abandon cumulate theory has not been made we suggest that the determination of whether cumulus and intercumulus phases were in equilibrium with each other and whether disequilibrium textures might yield a complete record of the crystallization history of the cumulus plagioclase are likely to be among the approaches that wil

a 20th century record of climatologically modulated sediment accumulation rates in a canadian fjord abstract the geochronology of a gravity core collected from an anoxic high sedimentation rate 2 5 cm yr setting near the head of the saguenay fjord in quebec has been established for the period 1900 1979 to a resolution of better than 1 yr using a constant flux 21 pb model interannual variations of the sedimentation rate of between 28 and 50 are caused by rapid inputs of coarse silt and fine sand during spring freshet events a significant correlation between sand percentage and sediment accumulation rate reflects the increase in stream competence during the spring freshet the sand percentage parameter can be used in conjunction with sediment size parameters to estimate temporal variations in river discharge intensity between 1914 and 1979 sediment accumulation rates were about 60 higher during the spring and summer compared to fall and winter seasons both the magnitude of the saguenay river spring discharge and the quantity of precipitation stored as snow decrease through the 20th century suggesting that the freshet intensity was governed largely by natural rather than anthropogenic e g dam construction factors a direct correlation between sand flux peak river discharge and a snow storage parameter provides a link between sediment texture and climate detailed analyses of the grain size distributions for dated core intervals offer a method for the reconstruction of a proxy record of paleodischarge for the saguenay river spring freshets

evaluation of trace element concentration acid leachable in sediments from river panuco and its adjacent lagoon areas ne mexico a set of forty one surface sediment samples were collected in river panuco and its adjoining lagoon areas in ne mexico to identify the enrichment pattern of trace elements the samples were analyzed for sediment texture carbonates organic carbon and acid leachable trace elements altes using autoclave method fe mn cr cu ni co pb zn cd v be ba sr as geochemical results of fe cr ni co v and sr in zone 1 indicate that erosion in the upland region sierra madre oriental mountains is very high the above feature is supported by the supremacy of finer sediments 82 12 carbonates 44 67 and organic carbon 10 74 which are brought down from the drainage basin the overall average concentration of altes mn 607 g g 1 cu 28 29 g g 1 ni 16 56 g g 1 pb 46 11 g g 1 cd 1 81 g g 1 and zn 92 18 g g 1 indicates higher values than the lowest effect level lel and effects range low erl of environmental indicators the results suggest that they are due to the increase in oil refineries metal based industries shipping activities and the effluent input which could enter the biological cycle and might create human health problems

rapid fluctuations in the deep north atlantic heat budget during the last glacial period 1 our understanding of past ocean climate interactions has been hampered by a paucity of proxy reconstructions of physical ocean circulation parameters here we present the first detailed record of deepwater temperature variability that resolves dansgaard oeschger climate fluctuations during the last glaciation results indicate a positive coupling between abrupt temperature changes over greenland and in the deep north atlantic that was mediated by perturbations to the atlantic overturning circulation the occurrence of sharp warming events at the center of the heinrich stadials 4 and 5 further indicates that the response of the ocean interior was less static across these major climate events than has been previously apparent

four climate cycles of recurring deep and surface water destabilizations on the iberian margin centennial climate variability over the last ice age exhibits clear bipolar behavior high resolution analyses of marine sediment cores from the iberian margin trace a number of associated changes simultaneously proxies of sea surface temperature and water mass distribution as well as relative biomarker content demonstrate that this typical north south coupling was pervasive for the cold phases of climate during the past 420 000 years cold episodes after relatively warm and largely ice free periods occurred when the predominance of deep water formation changed from northern to southern sources these results reinforce the connection between rapid climate changes at mediterranean latitudes and century to millennial variability in northern and southern polar regions

ichnological analysis of pleistocene sediments from the iodp site u1385 shackleton site on the iberian margin approaching paleoenvironmental conditions ichnological analysis focused on trace fossil assemblages and an ichnofabric approach with special attention to cross cutting relationships tiering relative abundances and bioturbation degrees has been used to assess environmental parameters affecting the pleistocene macrobenthic tracemaker community at the iodp expedition 339 site u1385 shackleton site on the iberian margin the trace fossil assemblage consists of abundant planolites frequent yet sparsely distributed palaeophycus thalassinoides and thalassinoides like structures and taenidium and localized zoophycos and chondrites other ichnotaxa such as phycosiphon and scolicia are rare this assemblage is typical of the zoophycos ichnofacies though the distal expression of the cruziana ichnofacies has a similar composition ichnofabrics reveal variable substrate colonization with well defined cross cutting relationships and tiering distribution differentiated ichnofabrics are green mottled ichnofabric planolites ichnofabric taenidium and planolites ichnofabric thalassinoides like and palaeophycus ichnofabric planolites and thalassinoides thalassinoides like ichnofabric zoophycos ichnofabric and chondrites ichnofabric usually showing gradual transitions a multi tiered assemblage can be envisaged with differentiation of the shallowest biodeformational structures shallow planolites palaeophycus and even taenidium middle thalassinoides thalassinoides like structures and lower zoophycos and chondrites tiers according to the ichnological data a general context of good bottom and pore water oxygen conditions and organic matter availability can be interpreted but localized dysaerobic intervals might be related with the record of zoophycos and chondrites a constant rate of sedimentation shows only minor variations as revealed by ichnofabric succession soupy soft and stiffgrounds are interpreted as inducing changes in ichnological features salinity and temperature have a minor incidence on the macrobenthic tracemaker community causing only small changes in the trace fossils

assessing the anthropocene with geochemical methods anthropogenic chemical contamination is one of the most evident signals of human influence on the environment the large amounts of industrially produced pollutants that have been introduced over decades into air soil and water have caused modifications to natural elemental cycling anthropogenic contamination usually leads to enrichment in many elements particularly in industrial areas thus certain elements and their isotopes can be used as geochemical tracers of anthropogenic impact some human induced changes in the environment may be regarded as a secondary effect of pollution such as acidification which causes increased geochemical mobility of several trace elements in surficial deposits methods used by geochemists to assess the scale of anthropogenic influence on the environment include calculations of anthropogenic influence on the environment via enrichment and contamination factors geoaccumulation index and pollution load index the use of geochemical background levels for delineating between natural and anthropogenic pollution is important a historical perspective of anthropogenic contamination allied with isotopic and geochemical signatures in dated sediment cores may be applied to help define the anthropocene human influence on the environment has been complex encompassing different environmental compartments air water soil and scales of changes local regional global the earth is a dynamic system and geochemical dynamics are best illustrated by consideration of element cycling although anthropogenic pollution sources have contributed to chemical changes in the atmosphere hydrosphere pedosphere and biosphere their impact on the total environment is best preserved in sediments which are often referred to as archives of contamination choi wania 2011 significant evidence of a distinctive anthropocene signal can be found in recent sedimentary deposits that have been impacted by anthropogenic activity and dated sediment cores can be used to reconstruct the chronology of contamination buckley et al 1995 in assessing the anthropocene it is important to quantify the human influence on the environment the results of this influence recorded in sediments can be evaluated using different approaches and criteria depending on the nature of the signal mechanical biological or chemical fig 1 zalasiewicz et al 2011a b price et al 2011 vane et al 2011 schrag 2012 geochemical methodology may help discriminate natural and anthropogenic sources of a given substance in the environment some of the methods and concepts e g anomaly background concentrations geochemical calculations and geochemical tracers traditionally used in geochemical exploration and further adapted to the needs of environmental geochemistry have found application in the study of anthropogenic contamination reimann de caritat 2005 reimann et al 2005 galuszka 2007 galuszka migaszewski 2011 these methods may be extended in assessment of the anthropocene anthropogenic anomalies and geochemical background concept geochemical anomalies can be defined as abnormal concentrations of elements in earth materials compared with background levels allaby allaby 1999 anomalous concentrations of elements are both of natural origin e g via oreforming processes weathering of ore bodies or mineralized rock formations sorption by mineral phases volcanic and hydrothermal activity and of anthropogenic origin mcqueen 2009 of the different types of geochemical anomalies fig 2 the positive anthropogenic anomalies of regional scale may provide a useful marker for the anthropocene selinus esbensen 1995 identification of geochemical anomalies requires knowledge of the normal or average distribution of elements in the environment which is usually referred to as a geochemical background lower and upper limits of the geochemical background from waters c n zalasiewicz j a williams m ellis m a snelling a m eds a stratigraphical basis for the anthropocene geological society london special publications 395 http dx doi org 10 1144 sp395 5 the geological society of london 2013 publishing disclaimer www geolsoc org uk pub ethics range are considered thresholds of negative depletion in an element and positive enrichment in an element anomalies fig 3 historically the search for positive anomalies has been essential to mineral exploration and in the 1960s geochemists established several methodologies for separating anomalies from the geochemical background hawkes webb 1962 miesch 1967 many fig 1 types of human induced changes their possible effects and sedimentary record fig 2 systematics of geochemical anomalies a ga uszka et al

south pacific intermediate water oxygen depletion at the onset of the paleocene eocene thermal maximum as depicted in new zealand margin sections 1 extreme global warming and massive input of 13c depleted carbon into the exogenic carbon cycle characterize the paleocene eocene thermal maximum petm circa 55 5 ma previous work indicates that dissolved o2 concentrations dropped in some regions of the ocean during this event but spatial temporal and causal relationships between warming carbon input and o2 deficiency remain elusive we present lithologic carbon isotopic and trace fossil results from outcrops in new zealand that clarify this issue sections exposed at mead and dee streams in eastern marlborough south island contain expanded sedimentary intervals that were deposited before during and after the petm on an upper continental slope the petm in these intervals is characterized by enhanced siliciclastic deposition a hallmark negative carbon isotope excursion and a loss of bioturbation importantly however the latter only occurs during the prominent drop in 13c and not during its recovery our results suggest that south pacific intermediate waters became hypoxic coincident to carbon injection at the start of the petm while higher sea surface temperatures throughout the petm would have decreased the dissolved oxygen content of sinking surface waters we argue here that oxygen depletion was driven by some combination of elevated temperature water column stratification and intermediate water methane oxidation

a near field sea level record of east antarctic ice sheet instability from 32 to 27 myr 1 fossil facies and isotope analyses of an early high paleolatitude 55 s section suggests a highly unstable east antarctic ice sheet from 32 to 27 myr the waxing and waning of this ice sheet from 140 to 40 of its present volume caused sea level changes of 25 m ranging from 30 to 50 m related to periodic glacial 100 000 to 200 000 years and shorter interglacial events the near field gippsland sea level gsl curve shares many similarities to the far field new jersey sea level njsl estimates however there are possible resolution errors due to biochronology taphonomy and paleodepth estimates and the relative lack of lowstand deposits in njsl that prevent detailed correlations with gsl nevertheless the lateral variations in sea level between the gsl section and njsl record that suggest ocean siphoning and antisiphoning may have propagated synchronous yet variable sea levels

chemical evolution of intercumulus liquid as recorded in plagioclase overgrowth rims from the skaergaard intrusion the intercumulus liquid of a crystal mush fills pore spaces and typically solidifies to form overgrowths on cumulus grains and poikilitic post cumulus minerals if the liquid is immobile solidification produces zoned intercumulus minerals as a result of progressive fractionation of the residual liquid convection within the mush results in buffering of the liquid composition and thus limits mineral zonation for fully solidified cumulates fossil changes in liquid composition or porosity are difficult to identify however detailed study of immobile minor components of plagioclase overgrowth rims can provide information about the progressive solidification of intercumulus material ti contents of plagioclase overgrowths in samples from the lowermost parts of the skaergaard intrusion show strong variations with anorthite content with decreasing xan ti concentrations first rise and then fall consistent with changing tio2 contents of the intercumulus liquid during solidification tio2 in plagioclase decreases sharply at an55 reflecting local saturation of fe ti oxides ti in clinopyroxene oikocrysts also falls rimward but zoning in faster diffusing species fe mg is limited other than slight reverse zones that may occur on the plagioclase margins xan falls continuously during crystallization the reverse zoning is interpreted as the result of compaction driven dissolution and reprecipitation of plagioclase the continual decrease in xan is exploited together with back scattered electron images of the cumulates to produce calibrated images showing regions of progressive crystallization this allows the regions crystallizing at each stage of solidification to be visualized these images show that the final remnants of interstitial melt were present in triangular pockets and as thin grain boundary melt films this approach can provide information about the progressive reduction of porosity during cumulate solidification

phase relationships between millennial scale events 64 000 24 000 years ago a core recovered on the iberian margin off southern portugal can be correlated with greenland ice cores using oxygen isotope variability in planktonic foraminifera which closely matches the ice core records of temperature over greenland our age model identifies the base of every interstadial between 64 000 and 24 000 years ago and uses the greenland ice core project grip timescale the oxygen isotope signal in benthic foraminifera on this grip based timescale is quite different from the planktonic record and resembles the temperature record over antarctica when this is synchronized with greenland using the record of methane in the atmospheric air in the polar ice cores we interpret the benthic record as indicating significant fluctuations in ice volume during millennial events and we suggest that antarctic temperature changed as a function of ice volume

plagioclase in the skaergaard intrusion part 1 core and rim compositions in the layered series the anorthite content of plagioclase grains xan in 12 rocks from the layered series of the skaergaard intrusion has been studied by electron microprobe typically 30 core and 70 rim analyses per thin section mean core compositions vary continuously from an66 at the base of the layered series lza to an32 30 at the top on the other hand crystal rims are of approximately constant composition an50 1 from the lza to the lower middle zone mz above the mz core and rim compositions generally overlap profiles across individual plagioclase grains from the lower zone show that most crystals have an external zone buffered at xan 50 1 the simplest explanation for these features is that during postcumulus crystallization in the lower zone interstitial liquids passed through a density maximum this interpretation is consistent with proposed liquid lines of descent that predict silica enrichment of the liquid associated with the appearance of cumulus magnetite

heavy metals content and distribution in the surface sediments of the guangzhou section of the pearl river southern china the long term industrialization and urbanization of guangzhou city may lead to heavy metal contamination of its aquatic sediment nevertheless only few studies have been published on the distribution and contamination assessment of heavy metals in this urban river sediment thus the major objective of this study was to quantitatively assess contamination of heavy metals and their chemical partitioning in the sediments of the guangzhou section of the pearl river gspr surface sediment samples were collected at 10 sites in the main river and 12 sites in the creeks of the gspr the total content of cd was determined by graphite furnace atomic adsorption spectrometry gf aas and content of cr cu pb and zn was determined by inductively coupled plasma atomic emission spectrometry icp aes the chemical partitioning of these heavy metals in the sediments of the main river was determined by the sequential selective extraction sse method results indicated that the average total concentrations of cd cr pb cu and zn in the sediments of the main river were 1 44 63 7 95 5 253 6 and 370 0 mg kg respectively whereas they were 2 10 125 5 110 1 433 7 and 401 9 mg kg in the sediments of the creeks the sediment at m4 and c9 sites was heavily contaminated with about 8 and 11 of toxic unit respectively cr cu pb and zn were mostly bound to organic matter and in the residual phase whereas cd was mostly associated with the soluble and exchangeable phase and the residual phase the mobility and bioavailability of cd zn and cr in the sediments of the main river were relatively higher than cu and pb due to higher levels in the soluble and exchangeable fraction and the carbonate fraction the potential acute toxicity in the sediments of the main river and creeks was mainly caused by cu contamination accounting for 21 7 37 1 and 16 9 46 3 of the total toxicity respectively followed by zn and pb adverse biological effects induced by heavy metals would be expected in the sediments of the gspr therefore the sediments of the gspr especially at m4 and c9 sites need to be remediated to maintain aquatic ecosystem health

biogenic magnetite detrital hematite and relative paleointensity in quaternary sediments from the southwest iberian margin magnetic properties of late quaternary sediments on the sw iberian margin are dominated by bacterial magnetite observed by transmission electron microscopy tem with contributions from detrital titanomagnetite and hematite reactive hematite together with low organic matter concentrations and the lack of sulfate reduction lead to dissimilatory iron reduction and availability of fe ii for abundant magnetotactic bacteria magnetite grain size proxies arm and arm irm and s ratios sensitive to hematite vary on stadial interstadial timescales contain orbital power and mimic planktic 18 o the detrital biogenic magnetite ratio and hematite concentration are greater during stadials and glacial isotopic stages reflecting increased detrital magnetite input during times of lowered sea level coinciding with atmospheric conditions favoring hematitic dust supply magnetic susceptibility on the other hand has a very different response being sensitive to coarse detrital multidomain md magnetite associated with ice rafted debris ird high susceptibility and or magnetic grain size coarsening mark heinrich stadials hs particularly hs2 hs3 hs4 hs5 hs6 and hs7 as well as older heinrich like detrital layers indicating the sensitivity of this region to fluctuations in the position of the polar front relative paleointensity rpi records have well constrained age models based on planktic 18 o correlation to ice core chronologies however they differ from reference records e g piso particularly in the vicinity of glacial maxima mainly due to inefficient normalization of rpi records in intervals of enhanced hematite input

quantification of bioturbation in hemipelagic sediments via thin section image analysis traditional ichnofabric descriptive semiquantitative l schemes rely upon subjective estimates of the degree to which original sedimentary fabrics have been disrupted this paper presents an objective method of quantifying bioturbation in hemipelagic sediments based on a thin section image analysis technique in order to perform these analyses optical or backscattered electron micrographs are processed in order to obtain black and white images in these images black pixels are silt size larger grains and the clay size sedimentary matrix are white pixels once the initial processing has been accomplished an index h is defined to quantify the horizontal orientation of the larger grain size fraction of the sediment h is low for bioturbated fabric and high for laminated sediments in hemipelagic suspension deposits h can he used to quantify bioturbation assuming that no other sedimentary processes have disrupted the original depositional fabric the quantitive bioturbation scheme described here is consistent with existing semiquantitative bioturbation schemes in addition it is objective and provides higher resolution descriptions of biological processes that disrupted the sediment after deposition applying this quantitative scheme should refine future paleoecological reconstruction derived from lacustrine and marine successions

electrochemical processes in a crystal mush cyclic units in the upper critical zone of the bushveld complex south africa the upper critical zone ucz of the bushveld igneous complex displays spectacular layering in the form of cyclic units comprising a basal chromitite layer overlain by a sequence of silicate cumulates in the order from bottom to top pyroxenite norite anorthosite electron microprobe and laser ablation inductively coupled plasma mass spectrometry analyses of chromite and silicate minerals in layers between the ug2 chromitite and the merensky reef reveal variations in major and trace element compositions that defy explanation with existing models of cumulate mineral melt evolution the anomalous features are best developed at sharp contacts of chromitite with adjacent anorthosite and pyroxenite cumulates here chromite compositions change abruptly from high and constant mg mg fe 2 and fe 2 fe 3 ratios in chromitite layers to variable and generally lower values in chromite disseminated in silicate layers furthermore the composition of disseminated chromites varies depending on the host silicate assemblage for example in ti v and zn contents importantly the abrupt change in chromite composition across the chromitite silicate layer contacts is independent of the thickness of the chromitite layer and the estimated mass proportions of chromite to intercumulus liquid chemical variations in plagioclase are also abrupt and some are hard to reconcile with conventional models of re equilibration with intercumulus liquid among those features is the decoupling of alkalis from other incompatible lithophile elements in comparison with cumulus plagioclase intercumulus poikilitic plagioclase in chromitite layers is enriched in rare earth elements but strongly depleted in equally incompatible li k and rb strong alkali depletion is also observed in intercumulus pyroxene from ultramafic cumulates and chromitite layers to explain these features we propose a new model of post cumulus recrystallization which intensifies the modal layering in the crystal liquid mush producing the observed sequence of nearly monomineralic layers of chromitite pyroxenite and anorthosite that define the cyclic units the crucial element of this model is the establishment of redox potential gradients at contacts between chromite rich cumulates and adjacent silicate layers owing to peritectic reactions between the crystals and intercumulus melt because basaltic melts are ionic electrolytes with na as the main charge carrier the redox potential gradient induces electrochemical migration of na and other alkali ions selective mobility of alkalis can explain the enigmatic features of plagioclase composition in the cyclic units sodium migration is expected to cause remelting of previously formed cumulates and major changes in modal mineral proportions which may eventually result in the formation of sharply divided monomineralic layers the observed variations in ferric ferrous iron ratios in chromite from the cyclic units and fe distribution in plagioclase imply a redox gradient of

high resolution digital image treatment to color analysis on cores from iodp expedition 339 approaching lithologic features and bioturbational influence abstract color analysis was conducted on selected cores from sites u1385 and u1389 from iodp expedition 339 based on a recently developed high resolution digital image treatment to explore its relationship with lithologic features e g percentage of sand this first step can be of potential usefulness in characterizing discriminating between different types of registered sediments in the iodp expedition 339 turbidites contourites and associated sediments and then for more general studies involving different lithologies sedimentary parameters and ichnological variations differentiation between types of deposits holds particular interest in the context of the mediterranean outflow water mow evolution and related depositional processes whose study was one of the main aims of iodp expedition 339 color characterization was executed on high resolution digital images by applying a method based on adjustment modification including levels brightness and vibrance followed by pixel measurement the applied methodology allows for a precise characterization of colors improving upon previous color descriptions by means of munsell color conducted on board during expedition 339 itself the studied interval is subdivided into four parts based on grain size analysis and color according to pixel values these parts are identified as a 120 b 90 c 140 and d 160 being well correlated with the corresponding lithology parts a and c with similar pixel values correspond to calcareous silty mud mudstone part b would correlate with calcareous silty sand sandstones and part d corresponds to calcareous mud sand content distribution throughout the studied interval bears a close relationship with the differentiated parts a to d intervals having a higher percentage of sand present a lower mean pixel value and darker color whereas the finer grained intervals contain sediments lighter in color represented by higher pixel values however as proved the proposed relationship between color sedimentological features type of sediment must be considered with some caution ichnological analysis reveals the influence of trace fossils on color variations in the sediment regardless of the size of traces and amount of bioturbation the infilling material of trace fossils being the most determinant factor thus lower bioturbated surfaces 6 by small trace fossils chondrites show higher influence on color variations 102 vs 107 than higher bioturbated surfaces 25 by large trace fossils thalassinoides 110 vs 112 due to the color of the infilling material 56 in the case of chondrites and 90 in the case of thalassinoides thus a detailed ichnological analysis should accompany the sedimentological study of deep sea modern cores in order to avoid misinterpretations of the sedimentological parameters involved

enrichment and toxicity of trace metals in near shore bottom sediments of cuddalore se coast of india in order to identify contaminating trace metals and their sources studies on trace metals are often included in routine environmental monitoring programs twenty five near shore bottom sediment samples from the inner shelf region near cuddalore of the bay of bengal were analysed for sediment texture organic matter carbonate caco3 concentrations and total trace metal concentrations ttms fe mn cr cu ni co pb zn and cd in order to evaluate geochemical processes such as enrichment and their origin the presence of carbonates 2 5 5 8 indicates the dominance of calcareous shells in the region a relatively high percentage of organic matter 0 2 3 9 is attributed to the predominance of finer sediments entering through the minor rivers high concentrations of ttms in fine and organic rich sediments are influenced by municipal and industrial sources which contention is well supported by correlations of ttms concentrations with fe mn fractions geoaccumulation index igeo calculations indicate that cr cu ni pb and cd concentrations are above the values expected from their presence in the discharge of effluents from the industrial zones bordering the shoreline comparing the findings of the present study with those from different parts of the world cr cu ni pb appear to be enriched in the sediments of the region

centennial scale surface hydrology off portugal during marine isotope stage 3 insights from planktonic foraminiferal fauna variability 1 the marine isotopic stage 3 mis3 at ocean drilling program odp site 1060 gulf stream shows both sharp onset and end of interstadials the existence of very short lived warm events during stadials and points to differences in detail between the sea surface temperature sst record from the western north atlantic and the atmospheric temperature record inferred from 18o in greenland ice investigating mis3 and obtaining comparable data from other locations appears crucial the eastern atlantic provides well documented records of climate changes we have selected a core from off portugal and use it to examine dansgaard oeschger events d o at centennial scale resolution 139 years on average between two data points we have obtained a faunal data set for core md01 2444 37 n 10 w 2600 m water depth and use a group of species globigerina bulloides globigerinita glutinata as a proxy of upwelling intensity driven by trade winds intensity changes we tentatively relate the variation of this group to a north atlantic oscillation like phenomenon nao off portugal we observe that it resembles the rainfall index in the caribbean as recorded at odp site 1002 cariaco basin which traces the intertropical convergence zone itcz location through changes of terrigenous inputs the driest intervals itzc to the south at site 1002 correspond to intervals of increased upwelling in md01 2444 as well as the driest periods identified during stadials on similar cores in the area because the itzc to the south is consistent with an el nino southern oscillation enso situation our study suggests a positive correlation between enso like conditions and nao like conditions at a millennial timescale during interstadial intervals when increased wetness over cariaco is recorded itcz to the north and the upwelling in md01 2444 is decreased we see from both ssts and faunal tropical indicators that md01 2444 site is warm in addition interstadials are equally warm through each so called bond cycle this contrasts with the greenland ice core project grip record where interstadial peaks are successively cooler through each bond cycle this record confirms a link between tropical climate linked to itcz position and the climate of southern europe at millennial timescales in spite of showing a very good correlation with polar latitudes grip through 18o on globigerina bulloides in addition because the warmest ssts and the 18o on g bulloides are so remarkably different our work points to changes in seasonality as a strong control over the climatic pattern of the north atlantic area and the marked influence of winter conditions

zoophycos in deep sea sediments indicates high and seasonal primary productivity ichnology as a proxy in palaeoceanography during glacial interglacial variations trace fossils provide valuable palaeoenvironmental information in hemipelagic settings this is particularly true in the case of zoophycos an easily recognizable trace fossil in core at iodp site u1385 zoophycos was found throughout an interval representing 1 5 ma covering 45 glacial interglacial cycles mediated by obliquity 41 ka and short term eccentricity 100 ka zoophycos is most common in sediments deposited during glacial times and when the sedimentation rate was intermediate and primary production was high and seasonal occurrences of zoophycos elsewhere support a similar relationship with seasonal organic matter deposition this is particularly significant considering that seasonality of organic matter deposition is difficult to decipher from the sediment record zoophycos appears to represent a useful proxy to characterize high and seasonal organic matter deposition and primary productivity in neogene hemipelagic deposits

accumulation of contaminant metals in marine sediments of halifax harbour nova scotia environmental factors and historical trends abstract sediments in halifax harbour have accumulated contaminant metals hg cu zn and pb as a result of discharge of untreated sewage and industrial waste leaching of land fill waste and surface drainage concentrations of contaminants in210pb dated sediment cores became significant about 1880 and rose rapidly after 1900 reaching maximum concentrations in the decades between 1950 and 1980 mean concentrations of hg increased from 0 2 g g 1 in pre 1890 sediments to 1 6 g g 1 in the 20th century similar enrichments for cu changed the concentration from 26 to 88 g g 1 for zn from 90 to 250 g g 1 and for pb the increase was from 12 to 206 g g 1 statistical factor analyses of geochemical data have been used to identify 1 primary contaminants directly associated with waste discharge these include total and organic bound forms of cu zn and pb 2 secondary contamination attributed to leaching and modification of primary contaminants include acid labile forms of zn ni and cu 3 diagenetic modification of buried sediments are identified by total and labile forms of mn 4 dispersion of contaminants from land surface drainage are characterized by fine grained aluminosilicates historical trends in the changing dominance of these environmental factors reflect changes in industrial activity urban growth and changes in the use of metals in paints domestic and industrial chemicals and in the combustion of fuels

present environment of dam lake sambe southwestern japan a geochemical study of bottom sediments geochemical analyses of lakebed and core sediments from lake sambe on the outskirts of oda city in shimane prefecture in southwestern japan were carried out in order to assess the water quality and the concentration and distribution patterns of sixteen elements the lake water showed a stratified condition with respect to dissolved o2 and as fe and mn concentrations in the bottom layers which increased in the summer the chemical composition of the sediments as measured by x ray fluorescence included major and trace elements p ca sc ti v cr fe ni cu zn as sr zr pb and th and total sulfur ts elevated values of as zn v fe p and ts were present in several layers of the upper cores from 0 to 5 cm and other surface sediments increases in the abundances of these metals in lake sediments are probably related to the reducing condition of the sediments fine grained organic rich sediments and post depositional diagenetic remobilization moreover correlations between the concentrations of trace metals and iron in the sediments suggest their adsorption onto fe oxy hydroxides whereas correlations with sulfur indicate that they were precipitated as fe sulfides the average abundances of as pb zn and cu exceeded the lowest effect level and interim sediment quality guideline values that the new york state department of environmental conservation and the canadian council of ministers of the environment determined to have moderate impact on aquatic organisms in addition concentrations of as and zn exceeded the coastal ocean sediment database threshold value indicating potentially toxic levels therefore the presence of trace metals in the lake sediments may result in adverse effects on biota health

dating errors in high resolution stratigraphy a detailed x ray radiograph and ams 14 c study of zoophycos burrows abstract bioturbation in oxic deep sea settings is often considered if considered at all to consist of a 2 10 cm thick homogenized layer and some easily recognizable distinct burrows which could be avoided when sub sampling the sediment cores however there is one trace that is often difficult to discern in unlithified sediments that manifests transport of considerable amounts of sediment over large vertical distances and that is widely spread in deep sea sediments in all oceans this trace zoophycos is therefore predestined to cause errors and even age reversals in high resolution dating in order to better estimate the size of these age errors we have performed ams 14 c dating of the trace itself and of directly surrounding material in two gravity cores from the portuguese continental slope the results show an age falsification of 1110 2525 years at sedimentation rates of 10 20 cm ka 1 since zoophycos burrows are often poorly or not at all visible in fresh cores all observations of zoophycos were made on x ray radiographs to avoid dating errors of this kind an x ray radiograph study prior to sub sampling is strongly recommended

ichnological analysis of the cretaceous palaeogene boundary interval at the caravaca section se spain abstract ichnological analysis of the cretaceous palaeogene k pg boundary at caravaca betic cordillera southeast spain reveals significant data for the interpretation of the k pg boundary event the uppermost maastrichtian marls below the cretaceous palaeogene k pg boundary at caravaca contains the dark coloured trace fossils chondrites targionii planolites thalassinoides zoophycos and alcyonidiopsis the composition of trace fossil associations in the upper maastrichtian and lower danian marls is generally the same yet much more poorly preserved in the latter showing in general no ichnological evidence of a severe macroinfaunal crisis at the k pg boundary the dark coloured trace fossils penetrate from two bioturbated horizons in the dark boundary layer separated by two horizons with primary lamination the ichnofauna rapidly recovered after the k pg event following deposition of the lower parallel laminated bed 14 mm thick that occurs in the dark boundary layer above the k pg boundary zoophycos is the deepest trace fossil penetrating as far as 90 cm below the k pg boundary probably in stiff or partly firm substrate which was dewatered to some extent during the slow accumulation of the danian dark boundary layer the firmness probably prevented the chondrites trace maker from deeper burrowing the maastrichtian sediments may be contaminated with danian microfossils due to bioturbation

stratigraphic variation in ichnofabrics at the shackleton site iodp site u1385 on the iberian margin paleoenvironmental implications abstract ichnofabric analysis was conducted on cores from site u1385 iodp expedition 339 to interpret paleoenvironmental conditions at the southwest margin of the iberian peninsula during the pleistocene site u1385 provides an important record for the study of orbital and suborbital scale climate variability changes related to ocean atmosphere dynamics and affected environmental parameters a detailed study of the ichnofabric characterization is presented focusing on the types of ichnofabrics relative abundance amount of bioturbation grouping ichnofabric succession transitions and vertical distribution seven ichnofabrics were differentiated green mottled ichnofabric planolites ichnofabric taenidium planolites ichnofabric thalassinoides like palaeophycus ichnofabric planolites thalassinoides thalassinoides like ichnofabric zoophycos ichnofabric and chondrites ichnofabric they exhibit significant differences in terms of ichnofabric features as well as in their stratigraphic distribution the most abundant ichnofabrics are planolites thalassinoides thalassinoides like ichnofabric and green mottled ichnofabrics with a dominance of the middle tier ichnofabrics the degree of bioturbation is moderate with a mean bi around 3 but showing a clear bimodal distribution one group of intervals is characterized by high bioturbation bi 6 while another displays low moderate bi values bi 1 2 in general ichnofabric features confirm generally good environmental conditions oxic environment and high food availability for the macrobenthic tracemaker community especially favorable in the uppermost part of the sediment a complete ichnofabric succession from deep to shallow tier ichnofabrics is commonly registered i e zoophycos ichnofabric or chondrites ichnofabric to planolites thalassinoides thalassinoides like ichnofabric and then either to green mottled ichnofabric or to planolites ichnofabric and then green mottled ichnofabric however there are some intervals where an incomplete succession between deep and shallow ichnofabrics is observed i e chondrites ichnofabric to green mottled ichnofabric or zoophycos ichnofabric to green mottled ichnofabric indicating relevant modifications of environmental parameters such as oxygen or food supply types of ichnofabrics and the bioturbation index show significant short term changes through the studied core such variations are probably correlated to millennial scale climatic perturbations such as glacial terminations and related phenomena heinrich events ice rafting events etc or long term cyclic patterns related to orbital climate variability the patterns could be tied to a significant change in the climate system such as the one associated with the middle pleistocene transition

quantitative estimation of bioturbation based on digital image analysis quantitative determination of modification of primary sediment features by the activity of organisms i e bioturbation is essential in geosciences some methods proposed since the 1960s are mainly based on visual or subjective determinations the first semiquantitative evaluations of the bioturbation index ichnofabric index or the amount of bioturbation were attempted in the best cases using a series of flashcards designed in different situations recently more effective methods involve the use of analytical and computational methods such as x rays magnetic resonance imaging or computed tomography these methods are complex and often expensive this paper presents a compilation of different methods using adobe photoshop software cs6 for digital estimation that are a part of the idiap ichnological digital analysis images package which is an inexpensive alternative to recently proposed methods easy to use and especially recommended for core samples the different methods similar pixel selection method spsm magic wand method mwm and the color range selection method crsm entail advantages and disadvantages depending on the sediment e g composition color texture porosity etc and ichnological features size of traces infilling material burrow wall etc the idiap provides an estimation of the amount of trace fossils produced by a particular ichnotaxon by a whole ichnocoenosis or even for a complete ichnofabric we recommend the application of the complete idiap to a given case study followed by selection of the most appropriate method the idiap was applied to core material recovered from the iodp expedition 339 enabling us for the first time to arrive at a quantitative estimation of the discrete trace fossil assemblage in core samples

evaluation of trace metal enrichments from the 26 december 2004 tsunami sediments along the southeast coast of india the tsunami sediments deposited after the december 2004 tsunami were sampled immediately in the coastal environment of tamil nadu state on the southeast coast of india fifty four sediment samples were collected and 14 representative samples were selected to identify the level of metal contamination in tsunami sediments the results indicate that the sediments are mainly of fine to medium grained sand and contain significantly high contents of dissolved salts in sediments na k ca 2 mg 2 cl in water soluble fraction due to seawater deposition and evaporation correlation of acid leachable trace metals cr cu ni co pb zn indicate that fe mn oxyhydroxides might play an important role in controlling their association between them enrichment of trace metals is observed in all the locations with reference to the background samples high values of trace metals in the southern part of the study area are due to the large scale industries along the coast and they are probably anthropogenic in nature and of marine origin which could cause serious environmental problems

quantification of bioturbation in hemipelagic sediments via thin section image analysis research methods papers abstract traditional ichnofabric descriptive semiquantitative schemes rely upon subjective estimates of the degree to which original sedimentary fabrics have been disrupted this paper presents an objective method of quantifying bioturbation in hemipelagic sediments based on a thin section image analysis technique in order to perform these analyses optical or backscattered electron micrographs are processed in order to obtain black and white images in these images black pixels are silt size larger grains and the clay size sedimentary matrix are white pixels once the initial processing has been accomplished an index h is defined to quantify the horizontal orientation of the larger grain size fraction of the sediment h is low for bioturbated fabric and high for laminated sediments in hemipelagic suspension deposits h can be used to quantify bioturbation assuming that no other sedimentary processes have disrupted the original depositional fabric the quantitative bioturbation scheme described here is consistent with existing semiquantitative bioturbation schemes in addition it is objective and provides higher resolution descriptions of biological processes that disrupted the sediment after deposition applying this quantitative scheme should refine future paleoecological reconstruction derived from lacustrine and marine successions

introducing fiji and icy image processing techniques in ichnological research as a tool for sedimentary basin analysis abstract in recent years image treatment has been appraised as a very powerful tool to facilitate ichnological analysis especially in marine cores of modern sediments supporting the determination of certain ichnological features however it is still a new approach and detailed research is necessary to encounter a faster and more efficient method the present study focuses on two image processing techniques fiji and icy and their comparison with a refined version of the well established high resolution image treatment strengths and weaknesses of the methodologies for the determination of three main features were explored i visibility of trace fossils ii quantification of the percentage of bioturbated surface and iii penetration depth estimation refined high resolution image treatment gives the best results for enhanced visibility of trace fossils whereas fiji is found to be a sound and rapid option one disadvantage shared by fiji and icy is the binary character of the produced images which may impede later ichnotaxonomical differentiation both fiji and icy fiji are rapid alternatives for quantifying the bulk amount of bioturbated surface the magic wand method refineedge based on high resolution image treatment provides good results regardless of the contrast of the images and it additionally allows for a more detailed quantification the semi automatic character of icy favors quick estimation of penetration depth and facilitates differentiation between distinct tracemaker communities based on a rapid quantification of pixel values thus fiji and icy methods offer good results and are much less time consuming than high resolution image treatment they are proposed as faster alternatives for the estimation of ichnological features especially useful at the beginning stages of research when a large number of samples must be analyzed

burrowed matrix powering dual porosity systems a case study from the maastrichtian chalk of the gullfaks field norwegian north sea abstract chalk reservoirs are commonly modelled as dual porosity systems in which a very porous but low permeable matrix is intersected by highly permeable vugs and fractures from which oil and gas can be produced the gullfaks field in the norwegian north sea contains such a reservoir which is producing from maastrichtian chalk in addition to the conventional triassic and jurassic siliciclastic reservoirs however in comparison to the prolific chalk fields in the southern north sea e g ekofisk valhall chalk reservoirs in the northern part e g oseberg and gullfaks fields experience challenged production due to reservoir presence and quality related to depositional facies and structural conditions analyses of cores from three wells in the maastrichtian shetland group of the gullfaks field reveal that this interval is completely bioturbated during several stages e g mottling with diffuse bioturbated texture in an early softground stage that became subsequently overprinted by more discrete burrows with active and passive fill and different rock properties during the stiffground and firmground stages of the ooze a rich and moderately diverse trace fossil assemblage consists of abundant zoophycos common chondrites taenidium thalassinoides and virgaichnus and rare nereites planolites spirophyton and teichichnus ichnological features allow the differentiation of five recurrent ichnofabrics thalassinoides zoophycos chondrites nereites and zoophycos taenidium ichnofabrics with variable influence on porosity and permeability the thalassinoides ichnofabric in chalk has the highest impact on improving reservoir quality whereas zoophycos and partly chondrites ichnofabrics in marly chalk and chalky marlstone respectively contribute to creating potential reservoir zones if burrow density is high enough thin section analysis of the different ichnofabrics illustrates the negative or positive effect of burrows on porosity distribution whereas micro ct imaging reveals an intriguing system of partly open micro burrows e g virgaichnus within the matrix which serves as source for porosity this burrow porosity provides a connection in the matrix that hosts open vugs and fractures thus improving oil production

time dependent modeling of fallout radionuclide transport in a drainage basin significance of slow erosional and fast hydrological components abstract the sediment depth distributions of 238pu 239 240pu 241am and 137cs have been measured in a sediment core from the saguenay fjord quebec canada which has been dated to better than 1 yr resolution over the past 100 yr using 210pb the historical record of fallout radionuclide fluxes to the sediments has been estimated using a 210pb constant flux model and variations in the flux distributions have been directly related to changes in the atmospheric input function rates of radionuclide transport through the drainage basin have been predicted using a two component time dependent model composed of terrestrial soil and water phases the latter including catchment basins upstream of the fjord the residence times of 137cs and 239 240pu in the soil component are 1000 and 3000 yr respectively while both radionuclides have equivalent residence times of 1 yr in the water column component the atmospheric burn up of a nuclear powered snap 9a satellite in 1964 has resulted in a well defined 238 pu 239 240 pu horizon appearing in the sediments at the 1967 1968 level the magnitude and timing of the snap 9a derived 238pu distribution are in agreement with the drainage basin model predictions and confirm the absence of post depositional remobilization of pu in these anoxic sediment regimes theoretical estimates of the change in the 241 am 239 240 pu activity ratio in sediments deposited since the 1950 s determined using the drainage basin model are in agreement with the experimental results and indicate that the initial 241 pu 239 240 pu activity ratio for the 1950 s weapons tests was 15 or more while the later weapons tests were characterized by an activity ratio closer to 12

composite ichnofabrics and tiering of burrows infaunal communities in marine environments typically are tiered that is different taxa live at different depths within the sediment tiered suites of biogenic structures yield complex biogenic sedimentary fabrics ichnofabrics with the traces of deep burrowing organisms overprinted on those of shallow burrowing organisms careful analysis of crosscutting relationships of burrows in such composite ichnofabrics allows reconstruction of the tiered nature of fossil endobenthic communities it is important to recognize that the best preserved and most prominently displayed trace fossils in most assemblages usually represent the deepest tier thus they were farther removed from the sea floor and therefore less indicative of actual sea floor conditions than the more poorly preserved traces of the shallower tiers on which the deeper traces are juxtaposed

atmospheric carbon dioxide concentration across the mid pleistocene transition the dominant period of pleistocene glacial cycles changed during the mid pleistocene from 40 000 years to 100 000 years for as yet unknown reasons here we present a 2 1 million year record of sea surface partial pressure of co2 pco2 based on boron isotopes in planktic foraminifer shells which suggests that the atmospheric partial pressure of co2 pco2 was relatively stable before the mid pleistocene climate transition glacial pco2 was approximately 31 microatmospheres higher before the transition more than 1 million years ago but interglacial pco2 was similar to that of late pleistocene interglacial cycles 450 000 years ago these estimates are consistent with a close linkage between atmospheric co2 concentration and global climate but the lack of a gradual decrease in interglacial pco2 does not support the suggestion that a long term drawdown of atmospheric co2 was the main cause of the climate transition