mass and heat flux of volcanic gas discharging from the summit crater of iwodake volcano satsuma iwojima japan during 1996 1999 abstract volcanic gas of iwodake has been discharged continuously from high temperature 900 c maximum fumaroles and a degassing vent which formed on the central floor of the summit crater after 1994 although most of the high temperature fumaroles located on the crater wall before 1991 many fumaroles appeared on the crater floor associated with the vent opening suggesting a shift of thermal activity from the peripheral to the central crater a large amount of volcanic gas has been discharged from the fumaroles and vent since heat has been transferred from ascending gas to the surrounding soil a region showing a surface temperature anomaly has developed around the fumaroles and vent to quantify iwodake thermal activity heat and volcanic gas mass fluxes were estimated during 1996 1999 using infrared thermal images and plume velocity and temperature data which were observed by a pitot tube and thermocouple the estimated gas mass flux was compared with the cospec data to investigate the accuracy of our estimation the gas mass flux had been decreased from 230 kg s in october 1996 to 30 kg s in november 1999 although the vent diameter had increased from 20 to 70 m during the same period this mass flux variation had indicated the decline of degassing rate the degassing depth was estimated from the volcanic gas mass flux and temperature the depth showed a tendency of magma head migration to shallower depth during 1996 1999 which was consistent with the drastic change of the surface manifestation

broadband seismic experiment at merapi volcano java indonesia very long period pulses embedded in multiphase earthquakes abstract multiphase mp and low frequency lf earthquakes with spectral peak amplitudes at 3 4 and 1 hz respectively are two common types of shallow volcanic earthquakes previously recognized at merapi volcano their mechanisms are poorly understood but mps have been temporally associated with lava dome growth we conducted a seismic experiment in january february 1998 using four broadband seismographs to investigate the nature of seismic activity associated with dome growth during our experiment merapi experienced mild dome growth with low level seismic activity we compare our data to that recorded on a local short period sp network with the following preliminary results mp and lf events as recorded and classified on the short period network instruments were recognized on the broadband network frequency spectrograms revealed similar patterns in the near summit region at widely separated broadband stations higher frequency spectra than previously recognized were identified for both mp and lf events and were strongly attenuated as a function of radial distance from the source thus the spectral characteristics of these events as recorded on far field stations are not fully indicative of the source processes in particular many events classified as lf type appear to have much high frequency energy near the source this aspect of these so called lf earthquakes and their association with very long period vlp pulses suggests that many events identified in the far field as lf events are in actuality a variety of the mp event and involve similar source processes broadband records indicated that simple large amplitude vlp pulses were embedded in mp and lf wavetrains from event to event these pulses were similar in their waveforms and had periods of 4 s vlp events embedded in lf and mp earthquakes were located using particle motions the epicenters were clustered in a central region of the dome complex and preliminary source depths were within about 100 m of the dome surface suggesting a source region deep within the dome or the uppermost conduit a similar source location was established by study of mp high frequency onsets our broadband data suggests that we have recorded both elastic seismic waves and a simple embedded pulse that is interpreted to represent a surface tilt at the seismometer site the inferred tilt indicates an inflation and subsequent deflation possibly caused by a gas pressure pulse or episodic shallow magma transport with stick slip movement of the conduit wall

broadband measurements of the sources of explosions at stromboli volcano italy during september october 1997 21 three component broadband seismometers were deployed on stromboli volcano at radial distances of 0 3 2 2 km from the active crater to investigate the source mechanisms of strombolian explosions in the 2 50 s band the very long period vlp signals associated with explosions are consistent with two stationary sources repeatedly activated in time vlp particle motions are essentially linear and analyses of semblance and particle motions are consistent with a source centroid offset 300 m beneath and 300 m northwest of the active vents similar vlp waveforms are observed at all 21 stations indicating that the seismograms are source dominated the vlp ground displacement response to each explosion may be qualitatively interpreted as 1 pressurization of the conduit associated with the ascent of a slug of gas 2 depressurization of the conduit in response to mass withdrawal during the eruption and 3 repressurization of the conduit associated with the replenishment of the source with fluid

direct rate measurements of eruption plumes at augustine volcano a problem of scaling and uncontrolled variables the march april 1986 eruption of augustine volcano alaska provided an opportunity to directly measure the flux of gas aerosol and ash particles during explosive eruption most previous direct measurements of volcanic emission rates are on plumes from fuming volcanoes or on very small eruption clouds direct measurements during explosive activity are needed to understand the scale relationships between passive degassing or small eruption plumes and highly explosive events conditions on april 3 1986 were ideal high winds clear visibility moderate activity three measurements were made 1 an airborne correlation spectrometer cospec provided mass flux rates of so2 2 treated filter samples chemically characterized the plume and 3 a quartz crystal microcascade impactor provided particle size distribution atmospheric conditions on april 3 caused the development of a lee wave plume which allowed us to constrain a model of plume dispersion leading to a forecast map of concentrations of so2 at greater distances from the vent on april 3 1986 the emission rate of so2 at augustine was 24 000 t d one of the largest direct volcanic rate measurements yet recorded with a cospec the results coupled with analytical results from samples simultaneously collected on filters allow us to estimate hcl emissions at 10 000 t d and ash eruption rate at 1 5 106 t d based on other data this ash eruption rate is about 1 50 of the maximum rate during the march april activity filter samples show that the gas aerosol proportions for sulfur and chlorine are about 10 1 and 4 1 respectively by contrast measurements of augustine s plume together with ground based gas sampling in july 1986 when the volcano was in a posteruptive fuming state are 380 t d so2 and approximately 8000 t d hcl with no ash emission the observations of large cl releases at augustine support the cl abundance conclusions of johnston 1980 based on study of melt inclusions in the 1976 lavas the results reinforce the need for more measurements during eruptions and for better understanding of scaling of volcanic emissions of various eruptive components

the latest cretaceous fauna with dinosaurs and mammals from the haţeg basin a historical overview abstract research on the uppermost cretaceous continental deposits with dinosaur remains from the ha eg basin has behind it a history of more than 110 years the first studies were by franz nopcsa 1877 1933 who published between 1897 and 1929 a series of notes and papers on this fauna including five monographs dedicated to the ha eg dinosaurs nopcsa described 10 vertebrate taxa including dinosaurs crocodilians and turtles from the ha eg basin out of which 6 are still valid he recognized the primitiveness and the small size of most of the taxa from the ha eg palaeofauna characters that he related to the isolated island environment within which this fauna lived for a long time span after nopcsa systematic research on the ha eg fauna was interrupted for many decades being resumed after 1977 when d grigorescu leading a small group of students in geology started to explore the deposits outcropping along the sibisel valley near s npetru village from where nopcsa made most of his collection of fossil bones since then the fieldwork continued every summer until now numerous remains of dinosaurs crocodiles and turtles being unearthed the list of the maastrichtian fauna from ha eg currently includes 56 taxa from all vertebrate classes more than half of the recorded taxa were discovered in micropalaeontological samples through screen washing the most spectacular discoveries made after 1977 include a large variety of small theropods several sites with dinosaur egg clutches one of these also yielding hatchling remains one of the largest pterosaurs in the world representing a new genus and species hatzegopteryx thambema and several taxa of multituberculate mammals studies of the ha eg fauna were not restricted to systematic palaeontology but also covered all the fields that contribute together to an accurate reconstruction of the environment within which the maastrichtian fauna existed this overview includes a list of contributors to the actual knowledge on the ha eg fauna during the last 30 years divided by fields of scientific interest

oceanic versus continental influences over the last 7 kyrs from a mid shelf record in the northern bay of biscay ne atlantic abstract we discuss paleoenvironments of north western france over the last 7 kyrs in terms of i long term changes relative sea level rise and boreal summer insolation ii rapid climate changes millennial scale bond events and multi decadal regimes of the north atlantic oscillation nao and iii growing human impacts in watersheds our study focuses on the cbt cs11 core retrieved in the northern bay of biscay with new high resolution 70 years palynological data dinoflagellate cysts and pollen combined with sedimentological and oxygen stable isotopic records this multiproxy approach enabled us to gain a better understanding of the influence of varying middle to late holocene climate regimes on marine coastal and terrestrial ecosystems as well as on human coastal societies we especially show that the slowdown of the relative sea level rise starting at around 5 9 ka bp led to the stabilization of tidal flats in estuarine environments subsequently increasing river flows to the ocean resulted in a progressive seasonal stratification of the shelf under increasing winter precipitations and establishment of the modern winter thermohaline front at 3 3 ka bp in addition within the 4 2 ka bp interval palynological and sedimentological evidence suggests increasing river discharges in north western france in a context of a weakened atlantic subpolar gyre and recurrent negative nao like conditions finally we identified a major transition at around 1 2 ka bp early middle ages that appears to be linked to a period of maximal anthropogenic landscape opening and soil erosion implying stronger primary productivity in coastal surface waters of the studied region

development of the benethic nepheloid layer on the south texas continental shelf western gulf of mexico abstract a monitoring study of suspended sediment on the south texas continental shelf indicates that a turbid benthic nepheloid layer is regionally persistent a sequence of quasi synoptic measurements of the water column obtained during six cruises in an 18 month period indicates substantial spatial and temporal variability in nepheloidlayer characteristics regionally the thickness of the shelf nepheloid layer increases both seaward and in a convergent alongshelf direction greatest thicknesses occur over a muddy substrate indicating a causal relationship maximum observed local thickness is 35 m which occurs along the southern shelf break analyses of suspended particulate matter in shelf bottom waters indicate mean concentrations ranging from 49 10 4 to 111 10 4 particle counts cc concentrations persistently increase shoreward throughout the region bottom particulate matter is predominantly composed of inorganic detritus admixtures of organic skeletal particles primarily diatoms are generally present but average less than 10 of the total particulate composition texturally the particulate matter in bottom waters is predominantly poorly sorted sediment composed of very fine silt 3 9 7 8 m the variability in nepheloid layer characteristics indicates a highly dynamic shelf feature the relationship of nepheloid layer characteristics to hydrographic and substrate conditions suggests a conceptual model whereby nepheloid layer development and maintenance are the results of the resuspension of sea floor sediment bottom turbulence is attributed primarily to vertical shear and shoaling progressive internal waves generated by migrating shelf water masses especially oceanic frontal systems and secondarily to shoaling surface gravity waves

source mechanism of vulcanian degassing at popocatepetl volcano mexico determined from waveform inversions of very long period signals 1 the source mechanism of very long period vlp signals accompanying volcanic degassing bursts at popocatepetl is analyzed in the 15 70 s band by minimizing the residual error between data and synthetics calculated for a point source embedded in a homogeneous medium the waveforms of two eruptions 23 april and 23 may 2000 representative of mild vulcanian activity are well reproduced by our inversion which takes into account volcano topography the source centroid is positioned 1500 m below the western perimeter of the summit crater and the modeled source is composed of a shallow dipping crack sill with easterly dip of 10 intersecting a steeply dipping crack northeast striking dike dipping 83 northwest whose surface extension bisects the vent both cracks undergo a similar sequence of inflation deflation and reinflation reflecting a cycle of pressurization depressurization and repressurization within a time interval of 3 5 min the largest moment release occurs in the sill showing a maximum volume change of 500 1000 m3 pressure drop of 3 5 mpa and amplitude of recovered pressure equal to 1 2 times the amplitude of the pressure drop in contrast the maximum volume change in the dike is less 200 300 m3 with a corresponding pressure drop of 1 2 mpa and pressure recovery equal to the pressure drop accompanying these volumetric sources are single force components with magnitudes of 108 n consistent with melt advection in response to pressure transients the source time histories of the volumetric components of the source indicate that significant mass movement starts within the sill and triggers a mass movement response in the dike within a few seconds such source behavior is consistent with the opening of a pathway for escape of pent up gases from slow pressurization of the sill driven by magma crystallization the opening of this pathway and associated rapid evacuation of volcanic gases induces the pressure drop pressure recovery in the magma filling the sill is driven by diffusion of gases from the resulting supersaturated melt into bubbles assuming a penny shaped crack at ambient pressure of 40 mpa the observed pressure and volume variations can be modeled with the following attributes crack radius 100 m crack aperture 5 m bubble number density 1010 1012 m 3 initial bubble radius 10 6 m final bubble radius 10 5 m and net decrease of gas concentration in the melt 0 01 wt

fine grained sediment budget on the continental margin of the bay of biscay abstract under present day conditions rivers are the main source of fine sediments dispersed to the bay of biscay they deliver about 2 5 10 6 t yr 1 of continental fine sediments 60 of which is derived from the gironde estuary of this flux 65 is believed stored on the shelf two kinds of mud fields can be found in the bay of biscay coastal mud and shelf mud belts the total mass of fine sediments stored during the past 2000 years is 3 2 10 9 t consequently about 0 9 10 6 t yr 1 could reach the shelf edge and eventually the open sea from this amount of displaced material and the deposition surface areas an evaluation of sediment fluxes across the margin during the late holocene period is discussed this evaluation is compared with results obtained from ecosysteme du canyon du cap ferret ecofer data from sediment traps and surficial box cores

world wide delivery of river sediment to the oceans new data and new estimates from old data show that rivers with large sediment loads annual discharges greater than about 15 times 10 6 tons contribute about 7 times 10 9 tons of suspended sediment to the ocean yearly extrapolating available data for all drainage basins the total suspended sediment delivered by all rivers to the oceans is about 13 5 times 10 9 tons annually bedload and flood discharges may account for an additional 1 2 times 10 9 tons about 70 of this total is derived from southern asia and the larger islands in the pacific and indian oceans where sediment yields are much greater than for other drainage basins

broadband seismic observation at the sakurajima volcano japan we installed a portable broadband seismometer streckeisen sts 2 at the sakurajima volcano which has been very active in the recent years the recorded seismograms show a wide variety both in temporal and spectral contents of seismic events from explosions to tremors and exhibit the importance of such broadband seismometry at volcanos we present examples of seismograms to show the potential of broadband seismic observation in monitoring volcanic activities

late holocene record from a loire river incised paleovalley french inner continental shelf insights into regional and global forcing factors abstract sediment core kv14bis was retrieved from the fosse du croisic a loire river incised paleovalley located in the inner shelf of the bay of biscay this core 5 4 m length covers the past 2 6 cal kyr bp with high sedimentation rate a multiproxy approach x ray imagery xrf data grain size analyses and benthic foraminiferal assemblages was applied in order to reconstruct the hydrological regime of the loire river during the late holocene this hydrological regime was further linked to climate forcing e g solar activity north atlantic oscillation nao and human activity our data describe a succession of several dry humid periods the humid periods are centered on 2 2 1 3 and 0 5 cal kyr bp and are characterized by high terrigenous flux fine silty sedimentation relatively high organic carbon content and high proportions of the epiphytic foraminiferal species planorbulina mediterranensis this species was probably brought to the study site by the loire river plume attached on floating algae the dry periods are centered on 2 5 1 5 1 2 cal kyr bp and 1900 ce and are characterized by low terrigenous input and high carbonate content due to abundant shell debris during periods of low river runoff deposition of a sand particle population grain size 200 m could indicate increased storminess this latter may have remobilized sediments from shallower depths during these generally dry periods on the continent the overall coherence of our results with several european continental records supports a pluri centennial scale regional climate control of humidity and storminess resembling that of the nao spectral analyses emphasized a possible additional control of solar activity through deforestation and soil erosion early human impact was also probably superimposed on this climatic forcing

highlights from a seismic broadband array on stromboli volcano an array of nine three component broadband seismometers was deployed in two different configurations on stromboli volcano the analysis of the seismic wavefield related to volcanic explosions revealed some observations which offer a completely new insight into the internal dynamics of a volcano these new observations are restricted to the low frequency range below 1 hz and underline therefore the superiority of broadband recordings over conventional short period observations surprisingly simple wavelets indicate an initially contracting source mechanism gas jets that could not be seen in a short period seismic record at all generate a clear dilatational wavelet in a broadband recording suggesting the same contracting source mechanism the analysis of particle motion and seismic array techniques permits a location of the seismic source we find low frequency signals of 3s and 6s period that are not related to eruptions and do not share a common source with the eruption related events a video recording of visible volcanic activity at the crater region allows one to correlate precisely eruptive features with seismic signals

plume front and suspended sediment dispersal off the yangtze changjiang river mouth china during non flood season abstract a sea survey was conducted in may 2001 using ctd together with direct reading current meter and water sampling to investigate the sediment dynamics off the yangtze river mouth data obtained from five observational sites reveal density flows characterized by the halocline thermocline and associated sharp current velocity gradients that prevail in the study area especially at the freshwater plume front the interaction of the yangtze freshwater plume littoral current and tidal current has generated these density flows particularly the anomalous high speed 140 cm s 1 current recorded at the freshwater plume front during the early flood stage leads to the resuspension of the sediment ssc reaching 0 5 g l 1 off the river mouth during that time period the suspended sediment flux measured at b2 the ideal site for recording frontal processes in the estuary indicates the main trend of southward transport of fine grained sediment up to 60 kg m 2 s 1 at early flood stage and 1 32 kg m 2 s 1 as net flux during two tidal periods it is inferred that the density flow at the plume front plays key roles in dispersing the yangtze fine suspended sediments southward during the non flood season

slope transport of suspended particulate matter on the aquitanian margin of the bay of biscay abstract spatial and temporal characteristics of the water masses and the dispersion of the suspended particulate matter were investigated using current meter hydrographic and nephelometric observations gathered during the ecofer experiment 1989 1991 in the cap ferret canyon on the aquitanian margin of the bay of biscay while characteristics of the deep water masses were stable from one year to another large hydrographic change in the upper 500 m related to winter renewal induced by poleward advection of warm and saline water along the continental slope the slope circulation and seasonal eddy activity appear as important dynamical mechanisms that control the entrainment and the dispersion of the suspended particulate matter from the neritic domain to the deep ocean a predominantly northward along slope current with occasional reversal characterizes this circulation the nephelometric structures also showed seasonal changes in the overall suspended particulate matter content but recurrent features such as the presence of intermediate nepheloid layers at the shelf break depth and various depths along the slope 500 1000 and 2000 m were observed these nepheloid layers extended off the slope to about 10 30 km but especially laterally along the slope their presence indicated that suspended particulate matter exchanges between the shelf and the slope occurred mainly in the head of the canyon and along the southern open slope the intermediate nepheloid layers around 500 m depth detached from the slope particularly in regions where the bottom slope is close to critical for the m2 internal tide

broadband seismic observations at satsuma iwojima volcano japan this paper reports the results of preliminary analysis of broadband seismic observations conducted at satsuma iwojima volcano japan the recorded broadband data show a wide variety of seismic features small m 0 short period volcanic earthquakes characterized by a long 5 s emergent phase and by nearly identical waveforms are located at the very shallow part of the summit crater long period seismic pulses synchronized with a regular amplitude modulation of volcanic tremor have an interval of approximately 46 to 50 min each of the long period pulses has almost identical waveform polarization of the long period events suggests a very shallow source which can be interpreted as a result of a volume expansion mechanism the correlation between the long period seismic pulses and volcanic tremor seems to be associated with magma convection and the degassing process inside the conduit of the volcano

relationship between hydrology and seasonal distribution of suspended sediments on the continental shelf of the bay of biscay abstract numerous oceanographic cruises with hydrology water sampling drift current measurements carried out since 1980 on the continental shelf of the bay of biscay together with available noaa avhrr infra red images form the basis of a proposed explanation for the processes responsible for the distribution of suspended sediments on the shelf the seasonal hydrographic structure of continental shelf waters is of paramount importance in sediment distribution in summer there is an horizontal stratification of water masses and suspended sediment distribution is closely related to the thermo haline structure a fresher water mass with less suspended material lies on a thicker and more turbid homogeneous layer during winter when sediment discharge from the rivers often reaches its annual maximum an oceanic thermo haline wedge occurs on the shelf at around 100 m as a result winter turbidity values on the outer continental shelf are low comparable to summer values and a permanent nepheloid layer is never observed the wedge which lasts for several months may act as a filter preventing transport to the slope high turbidities on the external shelf and the continental slope are only measured in spring when the thermo haline wedge disappears it seems possible that during winter time suspended materials brought by rivers are deposited in the grande vasiere the large mud patch it is postulated that the position of this mud patch is linked to the long term stable location of the thermo haline front that separates oceanic waters from the colder and less salty coastal waters

millennial scale holocene hydrological changes in the northeast atlantic new insights from la grande vasiere mid shelf mud belt a mid to late holocene paleohydrological reconstruction from the northeast atlantic is proposed through the study of a high resolution sedimentary record from the northern continental shelf of the

grain size relationship between suspended matter originating in the gironde estuary and shelf mud patch deposits abstract the grain size variations of the elementary fraction without aggregates of gironde suspended matter during its transfer to the shelf were analyzed and compared with those of the surficial sediment of the west gironde mud patch located between water depths of 30 and 70 m which is considered as a preferential deposition area for estuarine suspended matter sm the results made it possible to show that two processes complicate the relationships between the estuary and the shelf a biogenic contribution identified as early as at the gironde outlet corresponding to a mode at 15 20 m in the sm of the turbid plume and an inorganic contribution of a fine grained fraction coming from sandy shelf deposits corresponding to micas with a mode at 50 60 m and settling on the inner part of the mud patch the nourishment of the western and deeper part of this mud patch by estuarine suspended matter is derived from the benthic nepheloid layer in terms of grain size distribution this supply is characterized by the 7 5 m mode which is typical of particulate matter originating in the gironde estuary

the columbia river plume study subtidal variability in the velocity and salinity fields a comprehensive study of the strongly wind driven midlatitude buoyant plume from the columbia river located on the u s west coast demonstrates that the plume has two basic structures during the fall winter season namely a thin 5 15 m strongly stratified plume tending west to northwestward during periods of southward or light northward wind stress and a thicker 10 40 m weakly stratified plume tending northward and hugging the coast during periods of stronger northward stress the plume and its velocity field respond nearly instantaneously to changes in wind speed or direction and the wind fluctuations have timescales of 2 10 days frictional wind driven currents cause the primarily unidirectional flow down the plume axis to veer to the right or left of the axis for northward or southward winds respectively farther downstream currents turn to parallel rather than cross salinity contours consistent with a geostrophic balance in particular during periods when the plume is separated from the coast currents tend to flow around the mound of fresher water at distances exceeding about 20 km from the river mouth the along shelf depth averaged flow over the inner to midshelf is linear and depth averaged acceleration is governed to lowest order by the difference between surface and bottom stress alone in this region along shelf geostrophic buoyancy driven currents at 5 m calculated from surface density and along shelf geostrophic wind driven currents computed from a depth averaged linear model are comparable in magnitude 10 25 cm s 1

sediment entrainment on a wave graded shelf roussillon france abstract the sands of the inner shelf off the roussillon coast of the microtidal golfe du lion display a seaward fining texture and merge in water deeper than 20 30 m with midshelf muds there is a qualitative correspondence between the textural gradient and the seaward attenuating annual surface gravity wave power expended by tangential stress on the shelf surface various equations used to quantify the relation of sediment texture to fluid energy predict the trend of the observed textural gradient but overestimate its value an empirical threshold equation komar and miller 1975a b and a theoretical null point equation johnson and eagleson 1966 give comparable results implying that both may be describing the same state there is a disparity between the predictions of an incipient motion equation johnson and eagleson 1966 and the threshold equation probably because static instability of grains occurs prior to dynamic instability of grains in an increasing fluid velocity field theory forecasts that in water shallower than 30 m the sands are frequently entrained by shoaling waves particularly during the winter months the threshold of movement of sands in 5 m of water is exceeded for more than 40 of the year hence the grain size of the shallow water sands does not reflect the maximum energy level of the environment

intermittent stability and frontogenesis in an area influenced by land runoff a frontal structure in liverpool bay was studied using conductivity temperature depth ctd and current meter data at times of weak vertical mixing by wind and tides a density driven gravity flow induced by river discharge distorts the thermohaline field so that an expanding stratified region develops bounded offshore by a surface front expansion of this frontal structure is increasingly curbed by rotation as a near geostrophic balance is attained owing to friction the space scale and time scale of frontogenesis are somewhat greater than two internal rossby radii and an inertial period respectively at times of increased mixing the frontal structure is destroyed and the enhanced friction between layers inhibits gravity flow hampering the frontogenesis mechanism large variability in mixing conditions results in an intermittent frontal structure

benthic foraminiferal thanatocoenoses from the cap ferret canyon area ne atlantic a complex interplay between hydro sedimentary and biological processes abstract benthic foraminiferal thanatocoenoses from the cap ferret canyon area were studied in the 150 m fraction of 4 5 cm deep sediment levels at 13 stations the shallowest station 151 m depth is located at the shelf break close to the canyon head all other stations are located along two bathymetric transects seven stations along the canyon axis between 300 and 3000 m depth and five stations from 300 m to 2000 m depth along the southern flank of the canyon the comparison between the live rose bengal stained and dead assemblages shows that biological i e population dynamic and taphonomic processes i e test destruction transport generate important discrepancies between live and dead assemblages an important question is to what degree post mortem transport and redeposition of foraminiferal tests contribute to the difference between living and dead assemblages the composition of the thanatocoenoses 150 m from the inner continental shelf to the cap ferret canyon axis however transport of tests from outer shelf or upper canyon axis towards deeper sites occurs as indicated by an increase of diversity indices of the dead fauna along the canyon axis moreover some species e g cassidulina carinata are observed in the living fauna restricted to the shallow sites but occur in important amounts in the dead fauna at deeper stations suggesting that these taxa have been transported from upper canyon stations toward deeper sites since cap ferret canyon is inactive in terms of massive sediment transport i e gravity events downslope transport of foraminiferal tests probably takes place in nepheloid layers downslope transports of foraminiferal tests may create important biases for the utilisation of paleoceanographic proxies using the assemblage characteristics and or the geochemical composition of selected species however the study of dead assemblages along a canyon axis can give important clues about the sedimentary dynamics especially an idea of the quantity of reworked foraminifera transported through the canyon axis along the adjacent flank such evidence of downslope transport was not observed despite taphonomic test destruction and biological processes population dynamics the live fauna closely resembles the distribution and the composition of the dead assemblage therefore ecological information obtained from the fossil flank samples can be more reliably used to reconstruct paleoenvironmental conditions

a numerical investigation of choked flow dynamics and its application to the triggering mechanism of long period events at redoubt volcano alaska we use numerical simulations of transonic flow through a crack to study the dynamics of the formation of shock waves downstream from a nozzle like constriction inside the crack the model solves the full set of navier stokes equations in two dimensions via an explicit multifield finite difference representation the crack walls are assumed to be perfectly rigid and elastic coupling to the solid is not considered the simulations demonstrate how the behavior of unsteady shock waves near the walls can produce recurring step like pressure transients in the flow which in turn induce resonance of the fluid filled crack the motion of the shock waves is governed primarily by smooth low amplitude pressure fluctuations at the outlet of the crack the force induced on the walls scales with the amplitude of the shock which is a function of the magnitude of the inlet pressure aperture of the constriction and thickness of the boundary layer the applied force also scales in proportion to the spatial extent of the shock excursion which depends on the fluctuation rate of outlet pressure using the source parameters of long period lp events at redoubt volcano alaska as a guide for our simulations we infer that coupling of the shock to the walls occurs for crack inlet to outlet pressure ratios pi po 2 31 and that the position of the shock front becomes most sensitive to outlet pressure fluctuations for flow regimes with pi po 2 48 for such regimes fluctuations of outlet pressure of up to 0 5 mpa at rates up to 3 mpa s are sufficient to induce pressure transients with magnitudes up to 12 5 mpa over 0 1 2 5 m of the walls within 0 5 s these flow parameters may be adequate for triggering the lp events in the precursory swarm to the december 14 1989 eruption of redoubt according to the flow model the recurrence rate and amplitudes of l p events are inferred to be a manifestation of the response of a shallow hydrothermal reservoir to the sustained injection of superheated steam from a magma column roofing below this reservoir

sediment budget and transfer of suspended sediment from the gironde estuary to cap ferret canyon abstract a study of the particulate organic carbon content the grain size of suspended sediment and turbidity in a transect between the gironde estuary and cap ferret canyon indicates that particles from the gironde river are transferred to near the bottom of the canyon the separation of turbid estuarine water into bottom and surface nepheloid layers takes place in the gironde itself and in the nearshore zone the development of these two separate turbid layers is due to vertical a turbid surface plume and horizontal bottom layer salinity gradients the bottom nepheloid layer is caused primary by a horizontal supply of suspended sediment from the gironde rather than from resuspension or vertical sedimentation as suggested by other workers on the median and outer shelf the distribution of particles in the water column is influenced by thermal stratification the thickness of the bottom nepheloid layer increases from the estuary towards cap ferret canyon as a function of the thickness of the bottom waters detached nepheloid layers are observed at the shelf break coinciding with isopycnal surfaces due to the presence of cold waters in the cap ferret canyon superimposed advective inputs from the northern part of the shelf and resuspension of particles from mud patches contribute to the supply of particles towards the canyon suspended sediment in transit over the shelf break represents 2 3 of the total discharge from the gironde estuary this is a considerable amount as 50 of the suspended sediment is trapped in the west gironde mud patch and another undefined portion of the gironde sediment load is transported along the coast by tidal currents

taphonomical and palaeoecological investigation of the late cretaceous maastrichtian tustea vertebrate assemblage romania haţeg basin insights into a unique dinosaur nesting locality abstract the tustea vertebrate locality at oltoane hill northwestern part of the ha eg basin romania has provided a rich and diverse assemblage of late cretaceous maastrichtian continental vertebrates more than 800 vertebrate fossils were recovered from this locality the isolated and associated remains represent 21 different taxa including amphibians turtles lizards snakes crocodyliforms pterosaurs dinosaurs and mammals the local assemblage is overwhelmingly dominated by dinosaurs with the rhabdodontid zalmoxes as the most abundant taxon the bonebeds that yielded this fossil material occur in a stacked series of mudstone calcrete units belonging to the middle member of the densus ciula formation the taphonomical investigations suggest that the tustea assemblage is made up of attritionally accumulated politaxic remains and that it is a parautochthonous assemblage with no evidence for significant bone transport or reworking according to the synthesis of all available field data two outstanding fossiliferous levels can be identified within the tustea locality where megaloolithus eggs and hadrosauroid hatchling material are preserved together recognized here as two superposed nesting grounds such co occurrence was considered controversial since there is a long standing and quasi general consensus that eggs of the megaloolithus oogenus were laid by titanosaurian sauropods we present several alternative scenarios to account for the co occurrence of telmatosaurus hatchling remains and megaloolithid eggs in the nesting horizons and explore these alternative hypotheses by weighing the arguments supporting or contradicting them the burden of evidence derived from our sedimentological taphonomical and palaeoecological investigations at tustea is still in favour of the autochthony of the hatchlings preserved within their own nesting grounds whereas there is no such support for a titanosaurian origin of the tu tea megaloolithid eggs

tidal influence on suspended sediment distribution and dispersal in the northern andaman sea and gulf of martaban abstract surface and water column profiles of suspended matter collected during april may 2002 and satellite images were used to study factors influencing suspended sediment concentrations sscs and dispersal in the northern andaman sea and gulf of martaban one of the largest highly turbid areas of the world s oceans perennial high ssc in the gulf of martaban is due to a combination of factors including resuspension of sediments by strong tidal currents shallow bathymetry and seasonal sediment influx from rivers from satellite images it was observed that in the central portion of the gulf of martaban the turbidity front oscillates about 150 km in phase with spring neap tidal cycles and the area covered by the turbid zone ssc 15 mg l 1 increases from less than 15 000 km2 during neap tide to more than 45 000 km2 during spring tide the sediment discharged by the ayeyarwady river is transported mainly eastward along the coast into the gulf of martaban occasionally during the winter monsoon period sediment plumes are seen heading westward into the bay of bengal turbidity profiles show that bottom nepheloid layers are actively transporting some of the sediments into the deep andaman sea via the martaban canyon

ocean noise triggering of rhythmic long period events at deception island volcano 1 we report on swarms of repeating long period lp events with remarkably periodic occurrence at deception island volcano antarctica the lp events show dominant frequencies near 2 hz and characteristic inter event times that range from 10 s to 20 s for individual swarms we observe that lp inter event times are approximate integer multiples of the dominant periods of the oceanic microseism indicating a synchronization of lp activity with the phase of ocean noise we attribute lp periodicity to the coincidence of sustained lp activity in an unstable hydrothermal system and external forcing by ocean noise that introduces periodic pressure variations in volcano fluids we estimate the volumetric strain change generated by the oceanic microseism at the source location and conclude that strain of order 10 7 is sufficient to introduce clear periodicity in the lp sequences and that periodicity increases with increasing strain

sediment transport off the huanghe yellow river delta and in the adjacent bohai sea in winter and seasonal comparison abstract based on the data on the current velocity water temperature salinity turbidity and concentration of suspended sediment collected in november 2006 along three survey transects at three time series ship based stations off the huanghe yellow river delta and at twenty four grid survey stations in the adjacent bohai sea sediment transport off the huanghe delta and in the adjacent bohai sea under winter regime were studied and compared with those from the summer season the homogeneous distribution of salinity temperature and sediment in the water column indicated a well mixed body of water a zone of high suspended sediment concentrations ssc 100 mg l 1 with a width of 35 km was identified along the delta coast two highest ssc centers were found in the surface and middle water layers around the abandoned diaokou huanghe river mouth and the present huanghe river mouth and the third one in the bottom layer around the abandoned qingshuigou huanghe river mouth these three highest ssc centers become major sediment source areas in winter based on the location of the high bottom shear stress zone the prevailing wave directions and the protuberant topography of the river mouths we identified the resuspension origin of the three highest ssc centers caused mostly by the winter storm waves partially by tidal currents suspended sediment flux ssf along the three coastal transects indicated that the sediment in the northwest part of the delta was transported northeastward and southeastward along the coast of the recent delta lobe the ssc and ssf were higher in winter than summer by 1 7 27 1 and 2 122 5 times respectively except around the present river mouth this indicates that the intensity of sediment transport in winter is much stronger than in summer due to the powerful effect of winter storms although the river water and sediment discharges to the sea were much greater in summer the massive huanghe sediment to the sea was accumulated in a narrow coastal area due to weak hydrodynamics in summer and then strongly resuspended mostly by storm waves in winter and transported to the offshore area the coastal area off the huanghe delta acts as a sediment sink in summer and converted to be a sediment source in winter in response to the seasonal variation of the east asian monsoon in this region the erosion accumulation pattern of the huanghe subaqueous delta from 1976 to 2003 illustrates that river laden sediment is deposited mainly in the southern part off the coastal area and it is also the result of intensive southward sediment transport in winter

a robust low cost and well calibrated infrasound sensor for volcano monitoring abstract volcano acoustic signals contain valuable information on shallow magmatic and hydrothermal processes in some cases the detection of acoustic waves is the only clear evidence of the occurrence of volcanic explosions their study is thus complementary to that of seismic signals for this reason acoustic sensors are more and more frequently integrated in volcano monitoring systems as well as in temporary instrumental deployments we have developed a broadband robust and low cost infrasound sensor designed for the detection and analysis of acoustic waves on volcanoes it is based on a microelectromechanical differential pressure transducer mems the reference pressure is balanced with the atmospheric pressure through a pneumatic high pass filter its low corner frequency usually set to 60 mhz can be adjusted from a few to tens of mhz its amplitude range is 240 pa and its sensitivity is 20 mv pa 1 with a noise level 100 hz using two specially designed calibration systems which deliver sinusoidal pressure variations the mechanical elements of the sensor are produced by 3d printer and filled with epoxy resin which guarantees high robustness in the aggressive environment of most volcanoes the sensor dimensions 26x45x80 mm and weight 100 g makes it very easy to handle and install

origin and morphosedimentary evolution of fine grained modern continental shelf deposits the gironde mud fields bay of biscay france the gironde mud fields are thin blankets 4 m that extend from the inner to mid shelf over a restricted area 600 km 2 and overlie palimpsest sands and gravels seaward of the modern gironde estuary south western france the bulk of the mud has accumulated over the last two millennia and reflects the complex interactions of 1 an increasing estuarine supply of suspended particulate matter 2 resuspension of substrate material by storm events and 3 biological mixing the combination of these processes has produced various features within the deposits related to 1 the water depth and distance from source of the fine grained material which are manifested as a proximal distal cross shelf trend from an area of alternating mud sedimentation temporary after large river flows with resuspension by storm events to an area of mud accumulation in deeper water where bioturbation predominates 2 expansions of the mud depocentres over time such that they become more remote from sources of coarser shelf sediment resulting in an upward fining trend the lithofacies of the gironde shelf mud fields exhibit a number of similarities to those of larger scale modern muddy shelves and ancient shallow water mudrocks this work provides a detailed description of a facies model for fine grained shelf sediments deposited under relatively constant sea level

dynamics of mercury species in surface sediments of a macrotidal estuarine coastal system adour river bay of biscay estuarine and coastal surface sediments from the adour estuary and adjacent coastal area south bay of biscay have been investigated to establish mercury species variability in a macrotidal system submitted to contrasted seasonal river discharges and downstream urbanisation surface sediments were sampled during three campaigns in the major sediment deposits of the adour estuary and at selected discharge points concentrations of hg2 and mehg in adour estuarine sediments average 1600 and 1 3 pmol g 1 and range from 2 to 7300 pmol g 1 and from 0 5 to 8 0 pmol g 1 respectively the concentrations of inorganic ionic mercury hg2 and monomethylmercury mehg in the surface sediments display large seasonal variation being one order of magnitude higher in june 2001 for hg2 and in october 2000 for mehg the results show that hg2 can be accumulated in the estuarine sediments after seasonal river inputs and both remobilised and methylated during dry period mercury species concentrations in coastal sediments collected in june 2001 assessed the impact of estuarine inputs on the nearby coastal area except direct anthropogenic discharge points the variability and transfer of hg2 and mehg in surface sediments of the whole estuarine coastal macrotidal system can be depicted by simple geochemical parameters of the bulk sediments such as grain size distribution organic carbon and total sulphur

moment tensor analysis of near field broadband waveforms observed at aso volcano japan abstract locations and focal mechanisms of long period volcanic events observed at aso volcano japan are determined by waveform inversion near field broadband three component seismograms of four to seven stations are simultaneously inverted in the time domain in order to find the six component seismic moment tensor a linear inversion is performed at each point of a 3d grid located under the volcano in order to constrain the centroid position and the focal mechanism of the source the complete displacements including near field waves in a homogeneous half space for a general point source are taken into account inversions of 43 long period tremors and six phreatic eruptions exhibit mainly an isotropic mechanism with a minor deviatoric component that may originate from a north south trending crack these events are all located in a small region at about 1 3 km depth beneath the active crater the high accuracy both of locations a few hundred meters and of focal mechanisms given by the inversion is partly attributed to the rapid variation of the amplitude of the static displacement seen in the long period part of the near field seismograms