cold water coral habitats of rockall and porcupine bank ne atlantic ocean sedimentary facies and benthic foraminiferal assemblages the extent of the cold water coral mounds in the modern ocean basins has been recently revealed by new state of the art equipment however not much is known about their geological extent or development through time in the facies model presented here seven different types of seabed substrate are distinguished which may be used for reconstruction of fossil coral habitats the studied substrates include off mound settings foram sands hardgrounds dead coral debris and substrates characterized by a variable density of living coral framework whereas sediment characteristics only provide a basis for distinguishing on and off mound habitats and the loci of most prolific coral growth benthic foraminiferal assemblages are the key to identifying different mound substrates in more detail specific foraminiferal assemblages are distinguished that are characteristic of these specific environments assemblages from off mound settings are dominated by attached epifaunal species such as cibicides refulgens and cibicides variabilis the attached epibenthic species discanomalina coronata is also common in off mound sediments but it is most abundant where hardgrounds have formed in contrast the settings with coral debris or living corals attract shallow infaunal species that are associated with more fine grained soft sediments the typical living coral assemblage is composed of cassidulina obtusa bulimina marginata and cassidulina laevigata the abundance of these species shows an almost linear increase with the density of the living coral cover the benthic foraminifera encountered from off mound to top mound settings appear to represent a gradient of decreasing current intensity and availability of suspended food particles and increasing availability of organic matter associated with fine grained sediment trapped in between coral framework

210pb derived sediment accumulation and mixing rates for the washington continental slope abstract total sediment accumulation rates g yr in four canyons indenting the washington continental shelf are about twice those on the nearby open slope even though canyons comprise less than 40 of the depositional area of the entire slope this is because 210 pb derived sediment accumulation rates g cm 2 yr for astoria and quinault canyons are 3 4 times greater than those for willapa and grays canyons and intermediate open slope areas supporting the hypothesis that columbia river derived solids are preferentially transported to these two canyons quinault canyon currently appears to be accumulating solids at rates much greater than its low long term accumulation rate which is attributed to turbidity currents transporting solids down this canyon roughly every 500 years the following four different approaches all show that mixing may cause 210 pb derived sediment accumulation rates for slope and canyon sediments to be 2 3 times higher than true accumulation rates 1 comparison between accumulation rates calculated from 210 pb profiles with and without surface zones in which mixing has obviously affected 210 pb distributions 2 comparison between 210 pb derived and independently determined long term accumulation rates 3 comparison between 210 pb derived accumulation and modern columbia river discharge rates 4 comparison between two and three layer steady state one dimensional diffusion advection decay models mixing coefficients for surface sediments calculated using a one dimensional two layer vertical eddy diffusion model show large differences within the region with most in the 3 30 cm 2 yr range mixing rates are several times larger in canyon sediments from 0 2 1 1 km water depth probably due to physical reworking processes erroneously neglected mixing at depth of no more than 5 of that calculated for the surface mixed layer can cause the 2 3 fold calculated overestimation of true sediment accumulation rates and 2 4 fold calculated underestimation of true mixing coefficients

climate of the past 2500 years in the gulf of taranto central mediterranean sea a high resolution climate reconstruction based on δ18o and δ13c of globigerinoides ruber white we present a high resolution isotope stratigraphy based on globigerinoides ruber white over the past 2500 years in the gulf of taranto central mediterranean g ruber white reflects summer conditions in the gulf of taranto but is influenced by two major surface water masses the western adriatic current wac and the ionian surface water isw and their variations on a decadal to multicentennial scale our analysis of the 13c and 18o of g ruber white allows the distinction of several climatic periods the roman warm period rwp 450 0 bc with relatively wet and warm conditions and a higher influence of the wac the roman classical period rcp ad 1 200 characterized by salinity increase resulting from circulation changes the dark ages cold period dcp ad 500 750 where wetter conditions in the gulf of taranto region are coherent with an increase dominance of the wac the medieval warm period mwp with wet and warm conditions in the first and a gradual drying in the second half and finally the transition from the mwp to the little ice age lia which is characterized by continuing dry conditions

solar forcing of nile discharge and sapropel s1 formation in the early to middle holocene eastern mediterranean we present high resolution records for oxygen isotopes of the planktic foraminifer globigerinoides ruber 18oruber and bulk sediment inorganic geochemistry for holocene age sediments from the southeast mediterranean our 18oruber record appears to be dominated by nile discharge rather than basin scale salinity temperature changes nile discharge was enhanced in the early to middle holocene relative to today the timing of the long term maximum in nile discharge during the early holocene corresponds to the timing of maximum intensity of the indian ocean influenced southwest indian summer monsoon sim this coincidence suggests a major influence of an indian ocean moisture source on nile discharge in the early to middle holocene while presently the atlantic ocean is the main moisture source nile discharge was highly variable on multicentennial time scale during the early to middle holocene being strongly influenced by variable solar activity this solar driven variability is also recorded in contemporaneous sim records however not observed in an atlantic ocean derived west african summer monsoon record from the holocene this supports the hypothesis that the indian ocean moisture source predominantly controlled nile discharge at that time solar driven variability in nile discharge also influenced paleoenvironmental conditions in the eastern mediterranean bulk sediment ba al and v al used as indicators for export productivity and redox conditions respectively varied both in response to solar forcing on multicentennial time scales we suggest that changes in nile discharge on these time scales have been concordant with nutrient inputs to and shallow ventilation of the eastern mediterranean

the importance of melt tio2 in affecting major and trace element partitioning between fe ti oxides and lunar picritic glass melts abstract lunar mare basalts and picritic glasses have tio2 abundances ranging from less than 1 wt to over 16 any high ti mare basalt or picritic glass petrogenetic model must include fe ti oxides in the mantle source or invoke fe ti oxide assimilation during magma ascent to the lunar surface we conducted partitioning experiments to investigate high field strength element hfse rare earth element ree and transition metal distribution between fe ti oxides and lunar picritic glass melts over a range of melt compositions our results suggest that ilmenite melt and armalcolite melt hfse cr and v partition coefficients dhfse dcr dv are strongly dependent on melt tio2 content whereas ilmenite melt ree partition coefficients appear to be insensitive to melt composition as tio2 increases in picritic glass melts hfse cr and v activities in melt also increase and fe ti oxide melt dhfse dcr and dv decrease the effect of ti on partitioning behavior can be attributed to the formation of fe o ti melt species in high ti melts ilmenite dhfse range from compatible in oxides in equilibrium with low ti melts to incompatible in oxides in equilibrium with depolymerized high ti picritic glass melts dhfse are inversely correlated with tio2 abundance in the melt and become nearly constant for melts with more than 6 8 tio2 we present simple partitioning models that utilize the solubility of ilmenite and armalcolite in melt to effectively predict hfse partition coefficients across a wide range of picritic glass melt compositions the hfse budget of ilmenite cumulates that crystallize from the lunar magma ocean strongly depends on the composition of the magma ocean low ti and high ti lunar basalts can be produced by an ilmenite or armalcolite bearing hybridized mantle source or by assimilation of late stage magma ocean cumulates the dependence of dhfse and dcr on melt tio2 is consistent with the formation of lunar type 1 armalcolite from high tio2 picritic glass melt however lunar type 2 and 3 armalcolite have a more complicated yet undetermined history of formation

signatures of natural catastrophic events and anthropogenic impact in an estuarine environment new zealand the sedimentary record of known natural catastrophic events and anthropogenic activity in an estuarine environment is assessed using sedimentological chemical and geochronological techniques shallow cores collected from intertidal and salt marsh sediments in ahuriri estuary hawke s bay reveal a variety of signatures of natural and human disturbance evidence for the 1931 hawke s bay earthquake which resulted in an uplift of one to two metres in the napier area is given by a change from silt to sand dominated sediment in the lower estuary which is consistent with a shift toward higher energy depositional conditions following uplift however based on physical properties of sediments the 1931 uplift event does not appear to have caused major changes in depositional conditions in the upper estuary similarly no changes were recorded at one site in the lower estuary which seems to represent an area of low energy depositional environment although the 1960 chilean tsunami resulted in structural damage in napier it did not produce any recognisable sedimentological and geochemical signature in the sedimentary record suggesting that the study sites were possibly beyond the limit of sedimentation of the tsunami post european settlement impact is mainly restricted to the lower estuary where increased concentrations of zn cr pb and cu are attributed to industrial discharges evidence of agricultural runoff is shown by an increase in cu concentrations within a fine grained depositional environment that is distal from industrial sources in the town of napier chemical data cl and s suggest a change in the depositional environment in the upper estuary due to increased freshwater influx and or decrease in seawater influence dating by 210pb suggests that this occurred around the middle part of the 19th century and might be attributed to river flooding in the region at that time

trace metal enrichments in portuguese submarine canyons and open slope anthropogenic impact and links to sedimentary dynamics abstract in order to evaluate the role of submarine canyons as transport routes for the particulate matter including anthropogenic trace metals from coastal areas to the deep sea we analysed contents of ca al fe mn zn cr pb ni and cu organic carbon and calcium carbonate in surface sediments and sediment trap particulate material from canyon and open slope areas of the central portuguese continental margin the contribution of trace metals from anthropogenic sources was assessed by comparing present day concentrations and average elemental concentrations for the industrial period last 150 years with pre industrial baseline values baseline elemental concentrations are very similar for the lisbon setubal and nazare canyons but varying degrees of anthropogenic trace metal enrichments are recorded in more recent sediments the upper lisbon and cascais canyons appear the most affected by anthropogenic trace metal deposition excess pb zn and cu amount 55 57 and 21 respectively of total inventories over the last 150 years the upper nazare canyon follows with 42 21 and 17 respectively lower contributions of anthropogenic trace metals were found for the lower reaches of the canyons and adjacent open slopes indicating that the upper canyon areas act as trace metal depocentres whereas dispersal to deeper canyon and slope areas is limited the tagus and to a lesser extent the sado river appear the main sources of pb zn and cu to the canyons but atmospheric dispersal of pb seems also important especially in the southern area anthropogenic enrichment of pb and zn in the cascais and lisbon canyons is comparable to values published for canyons in the nw mediterranean and off taiwan located in close proximity to industrialized areas different from pb and zn present day cu enrichment appears to increase toward deeper water where pelagic sedimentation is predominant suggesting that dispersal of this trace metal is at least partly linked with surface water plankton production

climate controlled multidecadal variability in north african dust transport to the mediterranean high resolution laser ablation inductively coupled plasma mass spectroscopy scanning of resin embedded laminated sediments is used to detail variability in the composition and magnitude of recent eolian dust deposition in the eastern mediterranean the composition of dust accumulating in the anoxic atalante basin varies in response to the strength of the summer blocking mode of mediterranean climate dust sources located upwind on the westerly airflow are favored during phases of weaker blocking hence stronger summer westerlies this mode is in turn correlated to the pronounced multidecadal oscillation in mediterranean sea surface temperature related to the atlantic multidecadal oscillation suggesting that coupled ocean atmosphere dynamics control the large scale transport of dust in the region variable precipitation in dust source regions may also exert an influence on the relative flux of dust from each source and hence the net composition of dust deposited in the basin persistent oscillations in the composition of deeper sediments indicate that the basin offers a high potential archive for reconstruction of climate controlled variability in dust transport prior to the instrumental era

enhanced short term sediment deposition within the nazare canyon north east atlantic abstract in january and may 1999 interface sediments were sampled within the nazare canyon a large submarine canyon that deeply indents the western iberian continental margin ne atlantic at around 39 35n excess 234th profiles were established with high resolution to calculate inventories and bioturbation coefficients a northern transect at 42 n is briefly presented as a reference for the western iberian margin synthesis of these parameters is used to examine short term deposition within the nazare canyon 234thxs was always detected with significant activities on surface in most of the samples along the reference transect and in the adjacent area surface 234th excesses are about 10 20 dpm g 1 in contrast 234thxs reaches very high levels up to 170 dpm g 1 in the canyon there is a large range of variability in inventories and bioturbation rates in relation with depth and location these results show a preferential deposition in the canyon and focus in the upper and middle part of the canyon on a monthly time scale the nazare canyon appears as a significant locus of sedimentation for the western iberian margin

influence of deposition in dam reservoir on the deep marine hemipelagic environment off niigata central japan it has been well known that dam construction on rivers can cause a decrease in sediment supply and serious coastal erosion while influence of dams on the sedimentary environment beyond the coastal area has not been well known the mass accumulation rate mar in the hemipelagic environment 500 700 m water depth off niigata central japan since the early half of the twentieth century was obtained from core samples based on excess 210pb activity decreases in mar during the mid twentieth century were recognized in several core samples located northern off the agano and shinano river mouths using the cic model combining correction for the influence of surface bioturbation based on the ratio of mars decreases in mar were estimated as occurring during 1959 1964 and 1949 1955 these dates correspond with construction of the okutadami dam 1956 1961 possessing the largest capacity and reservoir sediment volume of 3 9 107 m3 in the agano and shinano river systems the other core located nw off the agano river mouth showed constant mar through the mid twentieth century a synchronicity of huge dam construction and decrease in mar in deep marine environment the similarity between silt clay sized grain size of dam reservoir sediment and that seen in the hemipelagic environment and horizontal distribution of decreasing mar in cores according to north northeastward sediment transport on shelf makes it reasonable to interpret that the decrease in mar in hemipelagic environment was caused by entrapment of silt clay grains in the huge dam reservoir

an overview of distal tephrochronology in northern europe during the last 1000 years several tephra layers from the last millennium have been identified in distal peat and lake sediment sequences in northern europe forming a framework of volcanic events of great value for palaeoenvironmental investigations most of the tephras within this framework have an origin in iceland but distal layers from jan mayen have also been identified the predominant transport pathway in an easterly southeasterly direction has led to the deposition of these tephras in a number of terrestrial deposits in northern europe ash from silicic eruptions 63 sio2 dominate at these sites even though many of the documentary records in distal areas report tephra fall from several basaltic eruptions here we provide an overview of the distribution shard concentration and geochemistry of these tephras to highlight the most important isochrones for addressing key dating issues in particular three horizons hekla 1 ad 1104 oraefajokull ad 1362 and askja ad 1875 are found at a number of different locations in northern europe and as such are valuable tie points for improving and validating chronological models and for synchronisation of records spanning the last 1000 years in addition we present new data identifying tephra from the grimsvotn volcanic system within the lomonosovfonna ice cap on svalbard demonstrating that some tephras have been transported 2000 km to as far north as 798 n along a northeasterly trajectory this discovery highlights the potential for utilising tephrochronology as a correlation tool for palaeoarchives located in more northerly areas and the complex nature of fall out from different eruptions copyright 2009 john wiley sons ltd

the relative mobility of natural th pb and po and fallout pu am cs radionuclides in the coastal marine environment results from model ecosystems merl and narragansett bay the relative mobility of nuclides of pb th pu and cs which are widely used as geochemical tracers for sedimentation and bioturbation was investigated in artificial microcosm tanks merl and in narragansett bay their mobility was characterized by their removal rates from the water column their affinity toward particles and their degree of penetration into the surface sediments pb th and pu transport was controlled predominantly by the affinity of these elements to particles and the transport parameters of the particles themselves i e sediment resuspension and mixing rates because of its low distribution coefficient transport of cs was controlled by molecular diffusion through pore water in the winter while in summer cs transport was enhanced due to bioturbation the increase with depth of the cspu ratio in core profiles of merl and narragansett bay sediments is thus caused primarily by the higher mobility of cs

origin and transport of trace metals deposited in the canyons off lisboa and adjacent slopes portuguese margin in the last century abstract submarine canyons play an important role in the transfer of contaminated sediments from shelf areas to the deeper ocean to evaluate the importance of submarine canyons adjacent to the tagus and sado estuaries portuguese margin as sediment pathway major and trace elements 210 pb radionuclides organic carbon calcium carbonate and grain size were analyzed in fifteen short sediment cores from the cascais and lisboa setubal submarine canyons and neighbor slopes at the estremadura spur and off sines mass accumulation rates mar vary between 0 02 and 0 40 g cm 2 y 1 with the highest values in the upper cascais and lisboa canyons mercury and pb enrichment factors exceed 2 and show a continuously increasing trend since 1950 ad in the upper sections of the cascais canyon and in the lisboa setubal canyon system implying an anthropogenic source mercury and pb anthropogenic inventories also present highest values in the canyon heads which is consistent with its proximity to the tagus and sado river mouths to a lesser extent the estremadura and sines slopes and the deeper sections of the canyons also have slightly increasing hg and pb enrichment factor trends towards the present day for these areas with a major influence of pelagic sedimentation we infer atmospheric transport as a complementary source of contaminants therefore our data suggest that although canyons are preferential conduits to transport sediments to the deep sea when compared to the slopes hg and pb derived from human activities have reached both domains with different intensities down to a depth of 2000 mwd

sediment mixing and accumulation rate effects on radionuclide depth profiles in hudson estuary sediments measured anthropogenic radionuclide profiles in sediment cores from the hudson river estuary were compared with profiles computed by using known input histories of radionuclides to the estuary and mixing coefficients which decreased exponentially with depth in the sediment observed sup 134 cs sediment depth profiles were used in the mixing rate computation because reactor releases were the only significant source for this nuclide whereas the inputs of sup 137 cs and sup 239 240 pu to the estuary were complicated by runoff or erosion in upstream areas in addition to direct fallout from precipitation our estimates for the rates of surface sediment mixing in the low salinity reach of the estuary range from 0 25 to 1 cm sup 2 yr or less in some areas of the harbor adjacent to new york city were fine particle accumulation rates are generally 3 cm yr and often as high as 10 to 20 cm yr sediment mixing rates as high as 10 cm sup 2 yr would have little effect on radionuclide peak distributions consequently anthropogenic radionuclide maximum activities in subsurface sediments of the hudson appear to be useful as time stratigraphic reference levels which can be correlated with periods of maximum radionuclide inputs for estimating rates and patterns of sediment accumulation

compositional data analysis coda as a tool to study the paleo ecology of coccolithophores from coastal neritic settings off central portugal abstract whereas using the species percentages is the standard analytical procedure used to infer species ecological preferences independently of taphonomical effects the closure problem associated with closed number systems and subsequent inconsistency of determining percentages may lead to spurious correlations biased statistical analysis and misleading interpretations to avoid these problems we applied compositional data analysis coda to investigate the paleo ecological preferences and spatial distribution of coccolith assemblages preserved in seafloor sediments using as a case study the central portuguese submarine canyons and adjacent shelf slope areas results from using the isometric log ratio ilr approach from coda are compared with results from using classical analytical methods and further discussed while providing scale invariance and subcompositional coherence coda is revealed to be a consistent statistical tool to infer the paleo ecological preferences of coccolithophores corroborating earlier work based on from percentage determinations results of this study clearly confirmed the coastal neritic distribution of coccoliths from gephyrocapsa oceanica helicosphaera carteri and coronosphaera mediterranea whereas coccoliths from calcidiscus leptoporus umbilicosphaera sibogae umbellosphaera irregularis and rhabdosphaera spp more typically occur offshore differences between canyons and adjacent shelf and slope areas were also confirmed namely the a greater importance of the coastal neritic assemblage possibly resulting from local and persistent nutrient pumping in these areas and b stronger mixing of coccoliths from coastal and oceanic species in upper canyon reaches resulting from the focused coastward advection of more oceanic water masses along their axes unlike the results from both ilr coordinates and the percentage approaches both coccolith concentrations and fluxes showed that spatial trends in which the species ecological inter relationships appear to be masked by taphonomical phenomena especially towards the coast and in the canyons suggesting the two latter approaches are not suitable to perform paleo ecological inferences in more dynamic coastal neritic settings our study suggests that the paleo ecological signal preserved in the studied sediment samples is persistent enough to be revealed by both coda and percentages yet given that coda provides the only statistical solution to coherently draw paleo ecological interpretations from compositional data our recommendation is that coda should always be used to test and validate any ecological signals obtained from percentage distributions

particle mixing rates in sediments of the northeast tropical atlantic evidence from 210pbxs 137cs 228thxs and 234thxs downcore distributions particle mixing rates were estimated from distribution of 137cs and excess activities of 210pb 228th and 234th measured in nine sediment cores taken from the northeast tropical atlantic i e at the three sites of the french eumeli eutrophic mesotrophic and oligotrophic programme at the oligotrophic site activities of 137cs and excess 210pb decrease smoothly with depth on the other hand at the mesotrophic and eutrophic sites 210pbxs and 137cs profiles suggest a mixing process with three different regimes with subsurface sediments being mixed more rapidly than those at the surface bioturbation rates were found to be slowest at the oligotrophic site intermediate at the mesotrophic site and fastest at the eutrophic site these mixing intensities appear closely linked to benthic fauna abundance organic carbon flux to the sediments and primary production in overlying surface waters the use of a multitracer approach for studying sediment particle reworking has allowed bioturbation rates to be better constrained and an assessment of whether radionuclide distributions in surface sediments are in steady state for only one core from the mesotrophic site were surface sediments not in steady state perhaps because of the occurrence of a benthic animal i e a xenophyophore at the surface of this core

pitfalls of normalization of marine geochemical data using a common divisor abstract normalization of trace element contents of sediment through division by the content of an immobile element usually aluminum is common practice in marine geochemical studies this might appear to be a simple way of correcting for dilution by sedimentary phases barren of a particular trace element for instance carbonates or silica and for comparison with its content in a standard clay or shale the purpose of this paper is to revive the awareness of the pitfalls of this practice by giving numerical examples of the often unexpected results of normalization taking a statistical perspective it is first shown that uncorrelated variables acquire spurious correlations when normalized but normalization can also increase decrease change sign of or even blur the correlations between unmodified variables next a number of realistic scenarios are worked out to show that the correlations between normalized element contents still suffer from the closure effect only in a few simple cases it is possible to extract from the normalized data realistic estimates of trace element contents in distinct sedimentary phases such as organic matter this is ascertained from data on copper contents in sediment from the black sea and arabian sea when the coefficient of variation i e standard deviation divided by the mean of the aluminum data is relatively low and much lower than for the original values of the trace elements comparisons of correlations can equally well or even better be made on the basis of the unmodified values then the comparison of trace element data with their values for standard shales is discussed the inherent problem is that the composition of the commonly used standard shale and consequently the reference values of normalized elements are not necessarily representative of the local or regional sediments in the study area also this method falls short of identifying the processes responsible for enrichment or diminution in trace element contents finally consideration is given to some aspects of a proper use of al normalization

the effect of bioturbation in pelagic sediments lessons from radioactive tracers and planktonic foraminifera in the gulf of aqaba red sea abstract studies of recent environmental perturbations often rely on data derived from marine sedimentary records these records are known to imperfectly inscribe the true sequence of events yet there is large uncertainty regarding the corrections that should be employed to accurately describe the sedimentary history here we show in recent records from the gulf of aqaba red sea how events of the abrupt disappearance of the planktonic foraminifer globigerinoides sacculifer and episodic deposition of the artificial radionuclide 137 cs are significantly altered in the sedimentary record compared to their known past timing instead of the abrupt disappearance of the foraminifera we observe a prolonged decline beginning at core depth equivalent to 30 y prior to its actual disappearance and continuing for decades past the event we further observe asymmetric smoothing of the radionuclide peak utilization of advection diffusion reaction models to reconstruct the original fluxes based on the known absolute timing of the events reveal that it is imperative to use a continuous function to describe bioturbation discretization of bioturbation into mixed and unmixed layers significantly shifts the location of the modeled event when bioturbation is described as a continuously decreasing function of depth the peak of a very short term event smears asymmetrically but remains in the right depth when sudden events repeat while the first spike is still mixed with the upper sediment layer bioturbation unifies adjacent peaks the united peak appears at an intermediate depth that does not necessarily correlate with the timing of the individual events in a third case a long lasting sedimentary event affected by bioturbation the resulting peak is rather weak compared to the actual event and appears deeper in the sediment column than expected based on the termination of the event the model clearly shows that abrupt changes can only endure in the record if a thick sediment layer settled on the sediment water interface at once or if bioturbation rates decreased to very low values for a prolonged period of time in any other case smearing by bioturbation makes an abrupt event appear to have started shortly before the real timing and end long after its true termination

estimates of particle flux and reworking at the deep sea floor using234th 238u disequilibrium abstract because of high specific activities of excess234th t1 2 24 1 days on suspended particles in the deep sea this nuclide is potentially an extremely sensitive indicator of particle inputs and dynamics at the seafloor measurements were made at two deep sea sites in order to examine this potential inventories of excess234th at a low current hemipelagic mud site 3990 m in the panama basin were 1 5 september 81 and 2 5 june 82 dpm cm2 the steady state fluxes to the seafloor calculated from these inventories are in rough agreement with radionuclide fluxes measured in sediment traps small scale 100m spatial variability in inventories implies biologically significant heterogeneity in particle inputs sediment from the continental rise site in the northwest atlantic 2800 m a site with higher current velocities than the panama basin had an inventory of 1 9dpm cm2 this inventory is also in rough agreement with predictions made on the basis of nearby sediment trap data particle mixing coefficients of 30cm2 yr calculated at the pacific and atlantic sites are similar to those in shallow water deposits but could reflect disturbance during handling based on210pb data from the panama basin sediment from below 6cm is mixed at a rate 10 slower than the near surface sediment to a depth of at least 20 cm agreement between234th predicted mixing rates at the panama basin site with210pb profiles and in situ experiments with glass bead tracers implies that these rates are real although the diffusion of dissolved234th into deep sea sediments complicates interpretations 234thxs distributions in bottom sediments offer a useful adjunct to sediment traps for investigation of particle dynamics near the deep sea floor

late holocene 0 2 4 ka bp surface water temperature and salinity variability feni drift ne atlantic ocean abstract planktonic foraminiferal mg ca ratios and oxygen isotopic compositions of a spliced sediment record from feni drift ne atlantic ocean box core m200309 and piston core enam9606 trace late holocene sea surface temperature sst and salinity changes over the past 2400 years at this location the variability of sst and oxygen isotopic composition of seawater 18 o w reflects variable northward advection of warm and saline surface waters which appears linked to climate variability over the adjacent european continent our records reveal a general long term cooling trend superimposed on this overall trend partly higher temperatures and salinities from 180 to 560 ad and 750 to 1160 ad may be ascribed to the roman and medieval warm periods respectively subsequently our record displays highly variable surface water conditions the main little ice age sst minimum is restricted to the 15th and 16th centuries ad pervasive multidecadal to centennial scale variability throughout the sedimentary proxy records can be partly attributed to solar forcing and or variable heat extraction from the surface ocean caused by shifts in the prevailing state of the north atlantic oscillation nao high salinities in the 17th and 18th centuries are considered to reflect tropical anomalies linked to a southward shift of the intertropical convergence zone propagating across the north atlantic ocean

the glacial interglacial transition and holocene environmental changes in sediments from the gulf of taranto central mediterranean abstract an extensive high resolution sedimentological geochemical survey was done using geo acoustics xrf core scans icp aes ams 14c dating and grain size analyses of sediments in 11 cores from the gulf of taranto the southern adriatic sea and the central ionian sea spanning the last 16 cal ka bp comparable results were obtained for cores from the gallipoli shelf eastern gulf of taranto and the southern adriatic sea suggesting that the dominant provenance of gallipoli shelf sediments is from the western adriatic mud belt the 210pb and 14c dated high accumulation rate sediments permit a detailed reconstruction of climate variability over the last 16 cal ka bp although the glacial interglacial transition is generally dry and stable these conditions are interrupted by two phases of increased detrital input during the bolling allerod and the late younger dryas the event during the younger dryas period is characterized by increased sediment inputs from southern italian sources this suggests that run off was higher in southern compared to northern italy at approximately 7 cal ka bp increased detrital input from the adriatic mud belt related to sea level rise and the onset of deep water formation in the adriatic sea is observed and is coincident with the end of sapropel s1 formation in the southern adriatic sea during the mid to late holocene we observed millennial scale events of increased detrital input e g during the roman humid period and of decreased detrital input e g medieval warm period these dry wet spells are consistent with variability in the north atlantic oscillation nao a negative state of the nao and thus a more advanced penetration of the westerlies into the central mediterranean that result in wet conditions in the research area concord with events of high detrital input e g during the roman humid period in contrast a positive state of the nao resulting in dry conditions in the mediterranean dominated during events of rapid climate change such as the medieval warm period and the bronze age

effects of faulting on crustal stresses during mountain formation on io abstract the vast majority of mountains observed on io are tectonic upthrusted blocks a product of compressional forces the mechanism behind their formation is generally understood to be related to io s heat pipe volcanism and crustal subsidence compressional thermoelastic stresses from sustained local or regional shut down of io s heat pipe volcanism could be potentially important orogenic drivers as well kirchoff and mckinnon 2009 formation of mountains on io variable volcanism and thermal stresses icarus 201 598 614 at the same time extensional tectonic features rifts pull apart basins simple graben are found on io furthermore results from a two dimensional finite element model of thrust fault formation in the ionian environment show that natural kinematics of fault motion creates localized regions of near surface extension while compressional stresses at depth are greatly reduced bland and mckinnon 2016 mountain building on io driven by deep faulting nat geosci 9 429 432 in light of these observations and model results we refine our previous one dimensional advective heat pipe model of io s crustal stresses exploring another horizontal boundary strain end member which is the laterally unconfined or integral stress condition first suggested by turcotte 1974 are transform faults thermal contraction cracks j geophys res 79 2573 2577 we also explore the effects of directly incorporating brittle failure limits and liquid sulfur through pore pressure on these failure limits horizontally unconfined vertical boundaries serve as an end member representation for stress release on preexisting faults and in the context of io predict extensional failure in the upper crust in response to deeper compression of either subsidence and or thermal origin including these modifications greatly decreases the size of the region in compressional failure in the lower crust unless the effects of pore sulfur are included as in our previous work the most favorable condition for mountain formation on io is suggested to be a combination of subsidence stress thermal stress from a decrease in volcanic heat piping and crustal thinning due to basal melting

desert flash floods form hyperpycnal flows in the coral rich gulf of aqaba red sea abstract running rivers are very scarce in globally distributed hyperarid and arid coastlines 28 000 km worldwide and it is ephemeral rivers that carry most terrestrial sediment into the sea in these regions however there is very little information regarding the contribution of terrestrial sediment and dynamics of transport of sediment that enter marine basins from these rivers one hyperarid region the gulf of aqaba received an exceptional number of flashflood events during the winter of 2012 2013 the results illustrate for the first time how the high volume of flashflood sediment influences the distribution of coral reefs dwarfs the contribution of airborne dust elevates floodwater densities to produce hyperpycnal flows despite highest ocean salinities and is subsequently transported to the deep basin where it may be preserved as a climate archive

depositional age and triggering event of turbidites in the western kumano trough central japan during the last ca 100 years abstract for correlating a turbidite record with a detailed land record of natural disasters during the last ca 100 years the depositional age of the surface hemipelagic sediments of the kumano trough located in central japan were estimated we attempted to extract mass accumulation rate of hemipelagic fallout from hemipelagic intervals on the basis of 137 cs geochronology x radiograph dry bulk density and grain size distribution based on assumptions of the biogenic mixing effect on the 137 cs appearance horizon and hemipelagite erosion by turbidity current the reconstructed turbidite record from hemipelagic fallout mass accumulation rate is well correlated with the record of major natural disasters in the kumano area based on the correlation most of turbidite layers are flood storm origin except for a well sorted seismo turbidite induced by the tonankai earthquake that occurred the mid 20th century although the wide distribution of a flood induced turbidite layer due to the 19th century tostukawa flood which was a huge disaster in the area caused by heavy rain and dams breaching it does not show a hyperpycnite succession the flood by dams breaching may cause surge like flow angular to subangular sand sized lithic fragments in the turbidite show that sand grains were transported from the kumano river directly plant debris and microfossils are common in both seismo turbidite and flood storm induced turbidites

recent sediment transport and deposition in the nazare canyon portuguese continental margin processes pathways and fluxes of sediment transport and deposition in the nazare submarine canyon portuguese continental margin were investigated by water column profiling of suspended particulate matter recording of near bottom currents and suspended particulate matter fluxes with benthic landers and by analysis of surface sediment cores the results show that fine grained suspended sediment from the adjacent shelf is captured in the upper canyon and actively transported through the canyon to the abyssal plain under influence of tidal currents and intermittent sediment gravity flows tidal currents are actively resuspending and transporting sediment in the upper to middle canyon as reflected by high concentration of suspended particles in bottom waters high horizontal and vertical sediment fluxes in the bottom water layer and high sediment accumulation rate on the seabed diminishing strength of tidal currents leads to focussed sediment deposition in the middle canyon further transport of sediments toward the lower canyon takes place predominantly by sediment gravity flows occurring on yearly or longer timescale turbidity currents strong enough to transport sand sized material to the lower canyon occur only on centennial or longer timescales

particle mixing rates in deep sea sediments determined from excess 210pb and 32si profiles particle mixing rates have been determined for 5 south atlantic antarctic and 3 equatorial pacific deep sea cores using excess 210 pb and 32 si measurements radionuclide profiles from these siliceous calcareous and clay rich sediments have been evaluated using a steady state vertical advection diffusion model in antarctic siliceous sediments 210 pb mixing coefficients 0 04 0 16 cm 2 y are in reasonable agreement with the 32 si mixing coefficient 0 2 or 0 4 cm 2 y depending on 32 si half life in an equatorial pacific sediment core however the 210 pb mixing coefficient 0 22 cm 2 y is 3 7 times greater than the 32 si mixing coefficient 0 03 or 0 07 cm 2 y the difference in 210 pb and 32 si mixing rates in the pacific sediments results from 1 non steady state mixing and differences in characteristic time and depth scales of the two radionuclides 2 preferential mixing of fine grained clay particles containing most of the 210 pb activity relative to coarser particles large radiolaria containing the 32 si activity or 3 the supply of 222 rn from the bottom of manganese nodules which increases the measured excess 210 pb activity relative to 226 ra at depth and artificially increases the 210 pb mixing coefficient based on 32 si data and pore water silica profiles dissolution of biogenic silica in the sediment column appears to have a minor effect on the 32 si profile in the mixed layer deep sea particle mixing rates reported in this study and the literature do not correlate with sediment type sediment accumulation rate or surface productivity based on differences in mixing rate among three antarctic cores collected within 50 km of each other local variability in the intensity of deep sea mixing appears to be as important as regional differences in sediment properties

validation of accumulation rates in teluk banten indonesia from commonly applied 210pb models using the 1883 krakatau tephra as time marker abstract teluk banten is a tropical shallow marine embayment on the north coast of java close to the krakatau volcanic complex the tsunami generated by the 1883 krakatau eruption resulted in the deposition of a tsunamite tephra layer on the bottom of teluk banten the krakatau event layer has been used as a time marker to validate 210 pb geochronological dating models this validation was performed to answer the question why should we believe excess 210 pb derived mass accumulation rates the commonly used models have therefore been applied to 210 pb activity profiles from 25 gravity cores models that have been validated are the constant flux and constant sedimentation cf cs with and without a surface mixed layer the constant initial concentration cic the constant rate of supply crs and the flux balance model after comparison of the mass accumulation rates mars of the different models with the mars obtained from the krakatau layer the following could be concluded firstly activity profiles without a surface mixed layer gave cf cs mars which were on average a factor 1 4 0 3 n 8 too high including a mixing rate of 0 5 0 4 cm 2 yr 1 into the model could explain this overestimation secondly for 210 pb activity profiles with a surface mixed layer the mars were in good comparison 1 0 0 3 n 12 with the mars derived from the krakatau event layer thirdly increased accumulation instead of reworking had to be the main cause of the comparatively thick upper layer of five cores with very high inventories fourthly assuming a variable accumulation rate and applying the cic model and crs model for these five cores the weighted average cic mars were in general more accurate than the crs mar finally the flux balance model which is not often used gave mars that were a factor 1 3 0 2 n 25 too high the advantage of this model is that it is independent of the profile shape the disadvantage is that a reliable and accurate initial activity over longer time scales has to be obtained

fallout plutonium and natural radionuclides in annual bands of the coral montastrea annularis st croix u s virgin islands abstract we have investigated the banded coral montastrea annularis as a recorder of the history of fallout pu in surface seawater thirty annual growth bands representing growth during coral years 1951 1980 were subsampled from m annularis collected at st croix u s virgin islands coral years begin and end in late summer early autumn and are designated for the calendar year in which they end 239 240 pu was finite in coral years 1954 1980 and the coral pu record is very simply related to the fallout history of 90 sr peaks in coral pu in coral years 1959 and 1964 correspond to fallout peaks in 1959 and 1963 respectively peak broadening and time lags in the coral pu record as compared to the 90 sr fallout record are consistent with retention of fallout pu in surface seawater for about two years characteristic removal time during the period of major fallout and possibly longer thereafter the simplicity of the coral pu record and its close correspondence with fallout history suggest that 239 240 pu was incorporated into the coral skeleton with constant discrimination relative to ca the effects of speciation and oxidation state upon pu incorporation are presently unknown to aid the pu interpretation ca mg sr na and natural radionuclides 238 u 228 ra 232 th and 210 pb were also determined in the annual bands in small samples 0 5 g ca mg and na show correlated variations which could be due to seasonal variability in uptake the 238 u and 228 ra records were generally consistent with uptake at constant discrimination from surface water reservoirs of nearly constant concentration although one sample showed probable diagenetic addition of u 232 th was not detected with certainty this implies that terrigenous particles were not consistently entrapped within the coral skeleton interpretation of 210 pb was difficult because 226 ra was not measured montastrea annularis preserves a record of fallout pu to make this record useful it must be considered in the broadest possible geochemical context

live and dead benthic foraminiferal faunas from whittard canyon ne atlantic focus on taphonomic processes and paleo environmental applications abstract dead benthic foraminiferal assemblages were studied in the 150 m fraction of 4 5 cm deep sediment levels at 18 stations in the whittard canyon area in june 2007 this sediment layer is composed of fairly recent sediment in both canyon branches the population dynamics such as seasonal response to phytodetritus deposition certainly contribute to differences between live and dead faunas for instance bulimina marginata which is usually considered as an opportunistic species is over represented in the dead assemblage the fragility of the tests of some species can explain their total absence in the thanatocoenoses this concerns many organic cemented arenaceous tests miliolid tests sensitive to dissolution and perforate taxa with thin tests furthermore transport e g sediment gravity flows active in both canyon branches leads to an increasing relative contribution of allochthonous individuals originating from outer shelf and upper canyon sites towards the deeper canyon stations consequently the dead faunas do no reflect local environmental conditions the high abundance of transported dead foraminifera in both canyon branches leads to important biases in the foraminiferal assemblage composition but may also significantly bias the interpretation of 13 c 18 o trace elements and 14 c concentration in foraminiferal shells it may therefore strongly complicate the reconstruction of environmental parameters such as bottom water temperature or exported paleoproductivity and radiocarbon dating of the foraminiferal assemblages therefore in both canyon axes the use of dead foraminiferal faunas to reconstruct paleoenvironmental in situ conditions is precluded however the study of dead assemblages in the canyon branches in particular the quantity of allochthonous foraminifera can give important clues about the downslope sedimentary dynamics on both open slopes despite taphonomic test destruction and biological processes population dynamics the distribution and the composition of the live fauna resemble those of the dead assemblage in these areas dead foraminiferal faunas include much less material derived from downslope transport consequently on the open slope dead assemblages appear to better reflect local conditions therefore the ecological information obtained from fossil open slope samples can be more reliably used to reconstruct paleoenvironmental conditions

shallow marine tsunami deposits in teluk banten nw java indonesia generated by the 1883 krakatau eruption teluk banten tb is a tropical shallow marine embayment with coral reef islands close to the krakatau volcanic complex the 1883 krakatau eruption generated a tsunami which had a devastating effect on the neighboring coastal areas the effects of the 1883 krakatau eruption and the associated tsunami on the bottom sediments in tb are assessed using textural compositional and 210 pb geochronological data an important diagnostic criterion consists of the occurrence of tephra conform descriptions of the 1883 eruption tephra the tsunamite consists of a sandy layer with abundant reworked shell and other carbonate fragments coarse components in the tsunamite consist of locally derived material eroded from the seabed land derived components are incorporated in the tsunamite only in close proximity to the coast the tsunamite is thickest in localized areas of the central part of the bay along the northern open sea facing slope of tb the tsunamite is relatively thin 6 7 cm thick but well preserved as little postdepositional modifications have occurred in the eastern bay area recent erosion since the redirection of the ciujung river in the 1920s has removed the krakatau tsunamite along the west coast of tb the only signature of the 1883 krakatau eruption consists of tephra and evidence for a high energy event is lacking presumably the western area was sheltered from the tsunami wave coming from the northwest at the shallower stations with low accumulation rates the tephra has been thoroughly mixed by bioturbation 2003 elsevier science b v all rights reserved

deposition rates mixing intensity and organic content in two contrasting submarine canyons the hydrographically different conditions characterising the western iberian margin ne atlantic and the gulf of lions mediterranean may play an important role in determining the biogeochemical characteristics of the sediments to investigate this we compared the nazare and cap de creus canyons and their respective adjacent open slopes in terms of the organic carbon corg contents chlorophyll a chl a concentrations c n and chl a phaeopigment ratios and also in terms of modelled mixing intensities chl a and 210pb deposition and background concentrations in sediments chlorophyll a and 210pb profiles were fitted simultaneously with a reactive transport model to estimate mixing intensity deposition and background concentrations further to account for the possibility that the decay of chl a may be lower in the deep sea than in shallow areas we estimated the model parameters with two models in one approach model 1 the temperature dependent decay rate of chl a as given by sun et al sun m y lee c aller r c 1993 laboratory studies of oxic and anoxic degradation of chlorophyll a in long island sound sediments geochimica et cosmochimica acta 57 147 157 for estuaries was used in the other approach model 2 an extra parameter was estimated to derive the chlorophyll a degradation rate an f test taking into account the different number of parameters in the models was used to single out the model that significantly fitted the data best in most cases the model parameters were best explained with model 1 indicating the empirical relationship by sun et al 1993 is a valid means to estimate the chlorophyll a degradation rate in deep sea sediments to assess the robustness with which the model parameters were estimated we provide a first application of bayesian analysis in the modelling of tracers in sediments bayesian analysis allows calculating the mean and standard deviation for each model parameter and correlations among parameters the model parameters for stations for which 210pb and chlorophyll a profiles were available were robustly fitted as evidenced by an average coefficient of variation of 0 22 corg contents chl a concentrations chl a phaeo ratios mixing intensities depositions and background concentrations of chl a and 210pb indicated that the cap de creus canyon and adjacent slope were less active in terms of organic matter accumulation and burial than the nazare canyon and respective open slope

manzala lagoon nile delta egypt modern sediment accumulation based on radioactive tracers this study was undertaken to determine whether recent anthropogenic changes in the nile basin have affected the modern rate of sediment accumulation in the nile delta excess 210pb 137cs and 239 240pu were used to develop a sediment chronology for a core from central manzala lagoon the delta sector which has had the highest average rate of sediment accumulation during the holocene to about 0 7 cm year 1 excess 210pb was detected in the top 32 cm of the core yielding an accumulation rate of 1 2 cm year 1 higher than the mean rate for the holocene a high 137cs 239 240pu ratio requires a reactor source possibly chernobyl for these nuclides low concentrations of excess 210pb and weapons fallout nuclides precluded recognition of changes in sediment accumulation rate in manzala lagoon during this century and may limit the use of tracer radionuclides for modern sediment chronology in the nile delta

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

recent sedimentation and sediment accumulation rates of the ba lat prodelta red river vietnam abstract the ba lat river is the major distributary of the red river system in north vietnam to assess the recent to subrecent depositional processes in the ba lat prodelta a detailed sediment analysis was conducted bottom samples were collected during two field surveys one in the dry season winter and one in the wet season summer a steep frontal prodelta slope is characterized by very rapid sedimentation tens of cm per year of muddy sediments under influence of the turbid river plume beyond direct influence of the river plume the bottom slope decreases and bottom transport by the prevailing southward directed currents becomes important coarse grained tempestites alternate with the dominating muddy sediments downcore changes in the 234 th activities indicate that the subaqueous delta progrades to the southwest with erosion and reworking of older sediments occurring north of the present outlet the southwestward progradation is also encountered in the trend of 210 pb activities indicating that this process has continued for at least 100 years avulsion of the ba lat outlet in 1973 has led to a decrease in sedimentation rates north of the ba lat outlet

mixing depths and sediment accumulation rates on an arid tropical shelf based on fine fraction 210pb analysis abstract continental shelves in arid tropical settings present particular challenges to 210pb based analysis of sedimentation rates and surface mixing owing to the combination of coarse sediment deep and year round bioturbation and lower atmospheric flux of 210pb the modern continental shelf at the northern terminus of the hyper arid gulf of eilat aqaba goe receives flood runoff of siliciclastics producing a mixed seabed with 20 carbonate that is dominated by larger benthic foraminifera and mollusks focusing analysis on only the fine fraction of deep penetrating cores 70 cm from 15 to 40 m water depths yields reliable 210pb profiles in contrast to analysis of bulk sediment graphical abstract sedimentation rates increase offshore five fold from 0 01 0 04 cm y in 15 m water depth to 0 21 0 27 cm y in 30 40 m depths reflecting offshore redistribution of flood delivered siliciclastic sediments away from the wadi mouth a result also supported by an offshore increase in the inventory of excess 210pb in contrast the thickness of the surface mixed layer sml decreases from 30 cm to 20 cm with proximity to anthropogenic stressors channelized flood runoff historic release of sewage and operation of fish cages which we attribute to the suppression of macrobenthic burrowers the rate of sedimentation on the gulf shelf away from dynamic bypassing in the 15 m shoreface is comparable to other tropical carbonate shelves rich in large benthic foraminifera and is higher than rates documented on the adjacent slope increasing confidence in this approach to 210pb analysis using only the fine fraction analysis of the fine fraction rather than bulk sediment would be a useful adjustment to 210pb methodology in any area with scarce fine grained sediment