seasonal and interannual variation of coccolithophore fluxes and species composition in sediment traps north of gran canaria 29 n 15 w abstract coccolithophore flux variations in sediment traps of the time series station estoc european station for time series in the ocean canary islands located 60 nm north of gran canaria were recorded from april 1993 to december 1996 the 20 cup particle traps were deployed at 1000 and 3000 m below sea surface and sampling intervals ranged from eight days to three weeks coccolith and coccosphere fluxes at both trap depths were characterized by a strong seasonality at 1000 m maximum coccolith fluxes were reached during spring from march to april 1995 and from february to march 1996 highest coccolith fluxes of 4538 106 coccoliths m 2 d 1 occurred at the beginning of march 1996 whereas lowest values of 19 8 106 coccoliths m 2 d 1 were recorded in june 1994 total coccosphere fluxes were constantly low during most of the investigated time interval and showed only high values during the main sedimentation phases from january to march 1995 up to 6 2 106 spheres m 2 d 1 and in march 1996 36 4 106 spheres m 2 d 1 at 3000 m water depth the sedimentation pattern was rather similar to the pattern observed at 1000 m maximum coccolith and coccosphere fluxes were also reached during spring time in february 1994 8200 106 and 15 6 10 6 m 2 d 1 respectively and in march 1996 8114 106 and 32 3 10 6 m 2 d 1 respectively however total coccolith flux peaks at 3000 m were about 2 4 times higher compared to the upper traps probably due to horizontal advection from phytoplankton material from north of the study site this effect also influenced the coccolith caco3 flux estimates mean calculated coccolith caco3 fluxes ranged between 3 9 mg m 2 d 1 for the upper traps 1995 1996 and 9 9 mg m 2 d 1 for the lower traps 1996 coccoliths contributed for about 8 78 of the measured total caco3 fluxes the coccolithophore assemblages were dominated by emiliania huxleyi florisphaera profunda and gephyrocapsa ericsonii during the entire sampling period whereas all other species together generally contributed less than 40 to the total assemblages variability of species compositions at either trap depth was very low indicating similar seasonal flux patterns of the different species

accumulation of mineral ballast on organic aggregates 1 to address whether the incorporation of suspended minerals drives the sedimentation of particulate organic carbon in the ocean or vice versa incubations of phytoplankton detritus aggregates were set up in rolling tanks containing seawater and suspended clay illite or calcium carbonate at concentrations ranging between 10 and 50 000 g l 1 the suspended minerals were efficiently scavenged by and incorporated into the organic aggregates the volume and porosity of aggregates decreased with increasing mineral concentrations and at suspended mineral concentrations higher than 500 g l 1 the initially medium sized aggregates were fragmented into thousands of tiny dense aggregates because radius and density have opposite effects on aggregate sinking rates the relationship between aggregate particulate organic carbon poc to mineral ratio and sinking rate is not a straightforward one that necessarily results in higher sinking rates with increased mineral content in these experiments the saturating capacity of organic aggregates for mineral particles appeared to be 97 to 98 weight percent mineral i e a poc to dry weight ratio of 0 02 to 0 03 g c g 1 this parallels the values of 0 05 g c g 1 observed for sinking particles in the deep sea and suggests that it is the flux of poc that determines the flux of minerals to the deep and not the other way around

mixing and the bottom nepheloid layer abstract a close relationship between active mixing and the structure of the bottom nepheloid layer on the oregon shelf is shown by combining mixing information inferred from temperature microstructure with concentration profiles derived from a transmissometer mounted on the microstructure instrument mechanical energy dissipation rates and eddy coefficients are usually consistent with those in an unstratified turbulent boundary layer but an exception was found when stratification due to suspended sediment was required to explain the observations except for this case the suspended particle concentration profiles for observations in approximately 100 m of water are consistent with the assumption of local equilibrium between turbulent diffusion and gravitational settling observations made in deeper 180 200 m water do not show this balance the high gradient region above the nepheloid layer in shallow water impedes diffusion sufficiently that escape of particles by this route is not important winter mixing destroys the layer long before diffusion would this region of low turbulent mixing was not consistently seen in the deeper water where high levels of turbidity were found throughout the water column low density turbidity currents of approximately 1 cm s 1 can be generated by the concentrations found

mechanical and petrophysical properties of north sea shales one of the problems when evaluating potential borehole stability problems in the drilling of hydrocarbon exploration and production wells is the lack of relevant data to describe the lithologies this relates in particular to the shales since these constitute most of the overburden and are also the most troublesome this paper presents a set of data from a variety of deeply cored shales from the north sea the shales have been extensively characterised and span a wide range of both petrophysical and mechanical properties depending on for example burial history and diagenesis special characteristics of shales have been tested and described including pore size distribution permeability anisotropy and temperature dependence appropriate procedures for sample handling testing and interpretation have been developed or modified from other related sciences

a new mechanistic model for organic carbon fluxes in the ocean based on the quantitative association of poc with ballast minerals abstract in simulation studies of the ocean s role in the global carbon cycle predicting the depth distribution for remineralization of particulate organic carbon poc is of particular importance following sarmiento et al global biogeochemical cycles 7 1993 417 most simulation models have the power law curve of martin et al deep sea research 34 1987 267 for this purpose the martin et al curve is an empirical fit to data most of which is from shallow floating sediment traps using such a fit implies that all the information necessary for prediction is contained in the carbon flux itself so that the organic carbon flux f oc z at any depth z can be predicted from the flux of organic carbon f oc z 0 at some near surface depth z 0 here we challenge this basic premise arguing that fluxes of ballast minerals silicate and carbonate biominerals and dust determine deep water poc fluxes so that a mechanism based model of poc flux must simultaneously predict fluxes of both poc and ballast minerals this assertion is based on the empirical observation that poc fluxes are tightly linked quantitatively to fluxes of ballast minerals in the deep ocean here we develop a model structure that incorporates this observation and fit this model to us jgofs eqpac data this model structure plus the preliminary parameter estimates we have obtained can be used to explore the implications of our model in studies of the ocean carbon cycle

patterns of suspended particle distribution and transport in a large fjordlike estuary seasonal and spatial patterns of the distribution and transport of suspended particles in puget sound a large fjordlike estuary are a product of the interaction of the subtidal circulation with surface and bottom particle sources the particle distribution differs from the distribution of hydrographic properties and is characterized by four persistant features 1 a thin 10 m high turbidity surface layer 2 a thick 50 m low turbidity zone centered around the level of no net motion between net seaward and landward flow 3 horizontal particle fronts at the sill entrances and 4 a bottom nepheloid layer maintained by local resuspension removal of particles from the surface waters by advective downwelling at the seaward sill and gravitational settling throughout the basin make puget sound an efficient particle trap particles sedimented on the basin floor are transported preferentially landward by the action of erosion deposition cycles enhanced by fortnightly intrusions of new marine water

coccolithophore carbonate during the last 450 ka in the nw pacific ocean odp site 1209b shatsky rise this study focuses on pleistocene holocene sediments from the shatsky rise ocean drilling program site 1209b nw pacific ocean we quantify the contribution of calcite made by coccoliths in oceanic sediments investigating the role of calcareous nannoplankton during the last 450 ka coccolith carbonate constitutes 60 90 of bulk carbonate coccolith carbonate accumulation rates cars and caco3 fine fraction confirm that coccolithophores are major contributors to the carbonate export and accumulation primary productivity shows highest values from marine isotope stage mis 12 to 8 thereafter although coccolith calcite content remains high other sediment components such as as foraminifera and biogenic opal seem to be favored perhaps related to an increase in fertilization by eolian dust our results demonstrate the important role of coccolithophore production and sedimentation on the regulation of ocean carbonate chemistry on time scales 1000 100 000 years on glacial interglacial scales coccolithophore productivity could have affected deep water saturation by buffering deep sea co2 through increased carbonate dissolution episodes spectral and wavelet analyses are consistent with cars primarily driven by glacial interglacial variability and obliquity controlled changes coccolith based paleoceanographic reconstructions allow us to establish that during the last 450 ka the mid latitudes of the nw pacific are controlled by the dynamics of the el nino southern oscillation perturbations and boreal monsoon system

the geometry and emplacement of conical sandstone intrusions conical sandstone intrusions with a geometry comparable with that of many igneous sills have been identified using 3d seismic data from large areas of the north sea and faeroe shetland basins these intrusions are of reservoir scale ranging from 100 to 2000 m or so in diameter 50 300 m in height and 1 80 m in thickness aperture they are concentrated in specific stratigraphic intervals in the cenozoic fills of both basins two geometrical end members are recognised and defined here apical cones and flat based bowls the former consist of inward dipping conical inclined sheets meeting at a prominent apex and the latter of similarly dipping discordant margins climbing from the edges of a concordant sheet both end members are associated with domal folds that are interpreted as resulting from the hydraulic elevation of the overburden during intrusion and which are analogous to similar structures associated with bowl shaped igneous sills measurements of aperture versus distance exhibit systematic relationships with the structural relief of these folds offering a potentially predictive method for estimation of sandstone intrusion aperture and reservoir volume prior to drilling a growth model for these end member geometries is presented drawing on existing theory for igneous sill emplacement aperture versus distance plots x are used to illustrate two contrasting models for aperture inflation during propagation but these require much further data before any specific growth model can be adopted

particle interaction in fjord suspended sediment abstract glacial flour enters the surface layer of howe sound a fjord in southwestern british columbia as a sediment plume which moves quickly down inlet while gradually mixing with the sea water flocculation occurs in the lower brackish waters of the surface layer although mixing and diffusion are the dominant processes for sediment to enter the marine water once in the underlying marine water zooplankton pelletization and biologic agglomeration of inorganic floccules predominate this generates a response in the order of days between the two layers in terms of sedimentation of particulate matter most particles settling in the fjord environment fall as 1 sand and silt grains containing attached clay particles 2 clay clasts possibly related to river mudballs 3 mineral bearing fecal pellets from pelagic zooplankton 4 large grain inorganic and colloidal floccules and 5 inorganic biogenic agglomerates analysis of sediment trap data has led to the following conclusions 1 water turbidity cannot be used to infer the downward flux of particles 2 size distributions of sediment deposited on the sea bed are a function of non lognormal size distributions from particles composing sub laminae

physical modelling of sand injectites abstract sand injectites are structures that result from intrusion of fluidized sand into fractures we have studied them in the tampen spur area of the north sea and have reproduced them experimentally by driving compressed air through layers of sand glass microspheres and silica powder the silica powder was cohesive and capable of hydraulic fracturing whereas the sand and glass microspheres were almost non cohesive and therefore able to fluidize the models were dynamically similar to their natural counterparts for as long as equilibrium was static when the processes became dynamic so that inertial forces were significant the scaling was approximate and the corresponding reynolds numbers differed the experimental apparatus was a square box 1 m 1 m wide resting on a grid of fluid diffusers during the experiments the fluid pressure increased until it attained and surpassed the weight of overburden flat lying hydraulic fractures containing air formed within cohesive and least permeable layers heterogeneities in material properties and layer thicknesses were responsible for localizing fracture networks when any one network broke through to the surface rapid flow of air through the fractures fluidized the underlying mobile materials and even depleted some of the layers some of the fluidized material extruded at the surface through vents forming volcanoes and sheets the remainder lodged at depth forming sand injectites or laccoliths conical sand injectites formed preferentially where layers had high resistance to bending laccoliths formed nearer the surface where overlying layers had low resistance to bending the experimental sand injectites were broadly similar to those in the tampen spur area of the north sea as well as other areas

association of sinking organic matter with various types of mineral ballast in the deep sea implications for the rain ratio 1 we compiled and standardized sediment trap data below 1000 m depth from 52 locations around the globe to infer the implications of the armstrong et al 2002 ballast model to the ratio of organic carbon to calcium carbonate in the deep sea the rain ratio we distinguished three forms of mineral ballast calcium carbonate opal and lithogenic material we concur with armstrong et al 2002 that organic carbon sinking fluxes correlate tightly with mineral fluxes based on the correlations seen in the trap data we conclude that most of the organic carbon rain in the deep sea is carried by calcium carbonate because it is denser than opal and more abundant than terrigenous material this analysis explains the constancy of the organic carbon to calcium carbonate rain ratio in the deep sea today and argues against large changes in the mean value of this ratio in the past however sediment trap data show variability in the ratio in areas of high relative calcium carbonate export mass caco3 mass ratio 0 4 unexplainable by the model leaving open the possibility of regional variations in the rain ratio in the past

coccolith sr ca ratios in the eastern mediterranean production versus export processes abstract samples collected by two sediment traps located southwest of crete in the eastern mediterranean emed 48a 1953 m and 48b 950 m from june 2005 to may 2006 were used to study fluxes of organic carbon carbonate and coccolithophores in combination with the variations of sr ca ratios in different individually picked coccolith species considering the complexity of the emed we validate the use of sr ca ratios as productivity proxy and unravel the varied processes which may influence it we examined the relationship between the seasonal peaks in export fluxes and the sr ca ratio in coccoliths of three upper photic zone coccolithophores species collected in the traps calcidiscus leptoporus helicosphaera carteri and emiliania huxleyi we aimed at testing whether high export fluxes are correlated with high sr ca ratios suggestive of higher nutrient stimulated production or sr ca ratios are unchanged during high export periods suggestive of increased export efficiency or scavenging periods of enhanced trap fluxes in march and june result from surface water blooms recognized in satellite imagery an additional peak flux was found in january but this peak represents re suspended or recycled material in the water column the amplitude of seasonal variations in the sr ca ratios of the three investigated species is small in both traps in the shallow trap a decrease in the sr ca ratio of c leptoporus occurred synchronously with minimal fluxes the other two species were not measured for this period in the deep trap no such decrease in sr ca was observed during minimal fluxes in either c leptoporus or h carteri probably due to a long residence of coccoliths in the water column recycling and low export efficiency absolute sr ca ratios for all species are lower than in other more productive environments like the bay of bengal arabian sea or sargasso sea we conclude that sr ca ratios in coccoliths of surface sediments in the emed reflect mainly spring summer bloom conditions averaged over hundreds to thousands of years in addition the origin of varying calcite thickness in h carteri was investigated the similarity of average sr ca ratios in differently calcified specimens confirms that coccolith thickness variations in this species result from primary biomineralization processes and not from variable overgrowth by low sr abiogenic calcite in the water column or the sediments

calculation of coccolith volume and its use in calibration of carbonate flux estimates abstract estimates of coccolith volume help in determining total coccolith carbonate fluxes and the relative contributions of various coccolith species it is argued here that the best approach to deriving such coccolith volumes is to calculate shape factors k s for each species separately based on reconstruction of cross profiles and to determine mean sizes from measurement of size variation in the sample of interest then volume k s l 3 values of k s are given for the most important extant coccolith species based on reconstruction of cross sections followed by calculation of a volume of rotation using an iterative routine implemented in an image analysis package substantial errors ca 50 are inevitable in such calculations but the resultant data are nonetheless of value coccolith assemblages from north atlantic 47 n 20 w jgofs 1989 sediment trap samples are analysed as a test case calculated coccolith pic fluxes constitute 30 80 of the chemically determined total pic fluxes

the influence of lithogenic material on particulate inorganic carbon measurements of coccolithophores in the bay of biscay following earlier data suggesting a decoupling between coccolithophore abundance and its suggested proxy particulate inorganic carbon pic we investigated this relationship in the bay of biscay northwest european shelf between december 2009 and july 2010 coccolithophore abundance coccolith calcite and pic were determined in surface waters 5 m depth along a transect crossing the bay emiliania huxleyi was the most abundant species of coccolithophore and the main contributor of coccolith calcite 55 64 pic ranged from 0 07 to 11 7 mmol c m 3 and coccolith calcite from 0 002 to 0 27 mmol c m 3 total pic exceeded coccolith calcite in all samples with only 11 of the pic attributed to coccoliths coccolithophores alone could not account for the pic concentrations measured lithogenic particulate matter with calcite and dolomite components was observed in samples across the route and decoupled the relationship between pic and coccolithophore abundance presence of lithogenic material and mesozoic fossil coccoliths in the samples implies sediment resuspension these findings question the suitability of pic as a proxy for coccolithophore abundance and dynamics particularly on or near continental shelves where the resuspension and lateral transport of lithogenic calcite may decouple the potential relationship between pic and coccolithophores

thrust wedges and fluid overpressures sandbox models involving pore fluids the well known model for the critical taper of an accretionary wedge includes overpressure as a first order parameter fluid overpressures reduce frictional resistance at the base of a wedge but they also act as body forces on all material particles of the wedge in addition to that of gravity by means of sandbox modeling many workers have tried to verify the predictions of the critical taper model but few of them have so far incorporated true fluid pressures we have used scaled experiments in which compressed air flows through sand packs so as to model the deformation of overpressured wedges a new apparatus provides for a horizontally varying fluid pressure for example a linear variation as in the critical taper model we have done three series of experiments involving horizontal shortening of homogeneous or multilayered sand models for various gradients of fluid pressure as predicted by the critical taper model the apical angle of the resulting wedge depends on the overpressure gradient in homogeneous sand at a high overpressure gradient deformation becomes diffuse and looks ductile in multilayered models detachments form beneath layers of low permeability so that thrusts propagate rapidly toward the undeformed foreland the efficiency of a detachment and its ability to propagate depend not only on the fluid pressure but also on the permeability ratios between the various layers

the mechanics and dynamics of sills in layered elastic rocks and their implications for the growth of laccoliths and other igneous complexes abstract the recent experimental work by kavanagh et al kavanagh j l menand t and sparks r s j 2006 an experimental investigation of sill formation and propagation in layered elastic media earth planet sci lett 245 799 813 shows that lithological discontinuities and rigidity contrasts can control the formation and dynamics of sills at interfaces separating upper rigid strata from lower weaker strata the present paper extends this work and focuses on its implications in terms of the length and time scales associated with the development of laccoliths and other igneous complexes sill formation controlled by rigidity contrasts is shown to provide a growth mechanism for laccoliths the formation of a sill provides favourable rigidity anisotropy for the emplacement of subsequent sills so that laccoliths grow by over accretion under accretion or even mid accretion of successive sills in accord with field data this model predicts that laccoliths grow mainly by vertical expansion representing the cumulative thickness of their internal sills while maintaining a comparatively constant lateral extend the model also predicts that the time scale over which laccoliths form is essentially determined by the cumulative time between successive sill intrusions also sill dynamics are controlled by viscous dissipation of the fluid along their length which have consequences for the size and shape of sills viscously controlled dynamics would enable sills to propagate further and thus to grow thicker than dykes of similar magmas these dynamics would also enable sills to propagate faster and thus to induce non elastic deformations in surrounding rocks that could deviate them from the interface they originally follow this would allow them to feed new sills along other interfaces and could assist in the formation of the step structures and saucer shapes that are commonly observed in sill complexes

coccolithophorids on the continental slope of the bay of biscay production transport and contribution to mass fluxes abstract coccoliths collected by sediment traps deployed on the slope of the bay of biscay northeastern atlantic from june 1990 to august 1991 were examined to determine their contribution to the transport of carbonate on a mid latitude continental margin they also were used as tracers of particle transfer processes on this slope two traps located at 1900 m respectively at 2300 mooring site 1 and 3000 m mooring site 2 water depths provided high resolution 4 7 days time series samples covering a 14 month period at ms2 and a 3 month period at ms1 coccoliths from 28 species were identified over the course of the experiment among which emiliania huxleyi was always dominant relative abundance range 59 93 total coccoliths number fluxes were high but variable ranging from 390 106 to 1610 106 coccoliths m 2 day 1 at ms1 and from 58 106 to 1500 106 coccoliths m 2 day 1 at ms2 the time weighted mean flux calculated for the whole experiment at ms2 was 499 106 coccoliths m 2 day 1 estimate of coccoliths minimal contribution to total carbonate flux at 1900 m depth averaged 12 which represented a weighted mean flux of 7 3 mg m 2 day 1 2 7 g m 2 yr 1 lateral transport of coccoliths resuspended from shelf and or upper slope sediments seems to be the dominant transfer process to depth on this northeastern atlantic slope nevertheless the clear seasonal succession observed in the species composition implies that the deposition resuspension transport sequence is rapid presumably less than a few months several short and unsmoothed signals directly issued from coccoliths bloom events also were recorded in our traps a result that indicates rapid settling rates the overall coccolith sedimentation processes appear as being quite diversified but quantitative and qualitative analyses of aggregates collected by the traps suggest that they are important carriers of coccoliths in this margin environment

a paleoceanographic model for the late campanian early maastrichtian sedimentation in the polish carpathian flysch basin based on nannofossils abstract the study is a qualitative and semi quantitative analysis of calcareous nannofossils in marlstone and calcareous mudstone beds in a 4 6 m thick section of the kropivnik fucoid marls late campanian early maastrichtian in the skole nappe of the polish outer carpathians this turbiditic succession is conspicuous by its short term alternation of marlstone rich and siliciclastic rich packages ca 1 m thick a model for paleoceanographic control on sedimentation is proposed on the basis of nannofossil assemblages in the studied section the nannofossils form assemblages of mixed synsedimentary taxa derived from diverse marine environments differing in trophy water temperature and distance from land the mixing occurred due to submarine resedimentation processes the nannofossils indicate that the siliciclastic rich packages were deposited during periods of lowered water temperature decreased calcareous nannoplankton production and oligotrophic to mesotrophic water conditions which corresponded to the sea level fall and lowstand anti estuarine circulation and downwelling due to arising shelf break front are inferred as the factors responsible for oligotrophy in contrast in the marlstone rich packages the calcareous nannofossils indicate sedimentation during periods of significantly increased calcareous nannoplankton production which corresponded to the sea level rise and highstand the increased nannoplankton production is attributed to estuarine circulation and upwelling the changes in sea level and water circulation conform to the climate changes postulated independently for the late campanian early maastrichtian

effects of acidification and primary production on coccolith weight implications for carbonate transfer from the surface to the deep ocean 1 the coccolithophores are not only an important group of oceanic primary producers they are also one of the main carbonate producers in the ocean because the calcium carbonate plates coccoliths secreted by these unicellular algae are so small and light a few picograms each they cannot be directly weighed with the result that very little is known about the effect of primary production and dissolution on the coccoliths using a new method that allows a rapid estimate of the weight of discrete coccoliths we analyzed the effect of dissolution the results of two acidification experiments using cultured and fossil coccoliths indicate that acidification does not change significantly the weight and size of coccoliths on the basis of these experiments we identify four parameters for identifying the effects of dissolution on a coccolith assemblage these parameters were applied in samples from two sediment trap time series taken at the same tropical atlantic site eumeli but separated by 2000 m water depth there was no evidence of increased dissolution with water depth between 250 and 2500 m this is indicative of the absence of dissolution of coccoliths between the photic zone and the lysocline other studies have identified supra lysoclinal dissolution and we propose that most of this takes place in the photic zone and possibly in the guts of grazers most of the coccolith weight changes observed over the duration of trap deployment were related to the occurrence of two coccolithophore blooms which resulted in significant increases in average coccolith weight of the dominant coccolithophore species during the blooms changes in growth rate and cell density appear to have a significant effect on the weight of coccoliths to test this observation we cultured e huxleyi at different p and n concentrations this test confirmed that coccoliths weigh more when coccolithophore production is highest an important consequence for the carbon pump is that during higher primary production events the coccoliths will increase the ballasting of the aggregates in which they are carried to the seafloor increasing the rate and amount of organic matter sequestered into the deep sea

coccolithophore caco3 flux in the sea of okhotsk seasonality settling and alteration processes abstract coccolithophore fluxes were determined in the sea of okhotsk using samples from a 1 year experiment 12 august 1990 to 12 august 1991 with sediment traps at 258 and 1061 m depth a special study was made on coccolithus pelagicus using fragmentation and the degree of etching as indicators of transport mechanisms a corrosion index for c pelagicus is developed the coccolithophore flux pattern at 258 m depth was characterised by a strong seasonality with flux peaks during autumn 1990 late november to early december and spring 1991 march the assemblage consisted almost entirely of the two species c pelagicus and emiliania huxleyi during autumn coccolithophore transportation to 258 m depth mainly occurred within cylindrical fecal pellets and marine snow aggregates of silicoflagellates and through agglutination on tintinnids grazing caused severe fragmentation of coccoliths and disintegration of coccospheres marine snow aggregates contained many intact coccospheres of c pelagicus during spring coccolithophores were probably removed from the euphotic zone by the ballast effect of sinking diatoms the coccolithophore flux peak in spring occurred immediately after the ice had retreated from the trap station and the trapped assemblage included coccoliths of subtropical species these features indicate drifting from an ice free location to the south or east the coccolith and coccosphere flux at 1061 m was respectively 7 and 12 times lower than at 258 m depth and maximum fluxes were recorded 2 months later increasing carbonate dissolution from 258 to 1061 m depth is expressed in the coccolithophore caco 3 flux reduction of 82 and in the increasing percentage of etched coccoliths of coccolithus pelagicus from 32 to 90

relationship between coccolith sr ca ratios and coccolithophore production and export in the arabian sea and sargasso sea coccolithophore caco3 production can account for 20 80 of biogenic carbonate exported from the photic zone and coccoliths are a dominant biogenic carbonate in many deep sea sediments a new method for picking individual coccoliths from sediment traps and sediments for analysis using secondary ion mass spectrometry ion probe allows us to make precise sr ca and mg ca determinations on coccoliths from single species even in samples where material is limited there are large biological effects in sr ca partitioning in coccoliths that have been related to variations in coccolithophore productivity in sediment traps from the sargasso sea at bermuda and arabian sea in the somali basin we can identify sr ca variations in several species that are consistent with inferred seasonal variations in coccolithophore productivity in surface waters in the arabian sea coccolith sr ca ratios in calcidiscus leptoporus and helicosphaera carteri are lowest during the nonproductive intermonsoon they are highest during the upwelling of southwest monsoon and during the nutrient entrainment from strong winds of the northeast monsoon these sr ca variations match seasonal trends in coccolith export flux furthermore sr ca variations in c leptoporus are larger and this species also has the greater variation in export flux between southwest monsoon and intermonsoon seasons at bermuda a 1996 fall bloom driven by passage of a warm mode water eddy induced a large increase in sr ca of c leptoporus coincident with an increase of c leptoporus export over an annual series for 2004 highest sr ca ratios of c leptoporus in the summer months match the typical summer peak in surface standing stock of this species and the stimulation of its productivity by mesoscale cyclonic eddies and eddy eddy interactions high sr ca did not coincide with the highest export of c leptoporus coccoliths likely because cyclonic eddies unlike mode water eddies are dominated by small phytoplankton with low export efficiency these data confirm a relationship between coccolith sr ca ratios and productivity sr ca ratios of the smaller and more slowly sinking emiliania huxleyi at bermuda show very small o4 seasonal sr ca variations in contrast nutrientlimited culture experiments for this species reveal significant 435 increases in sr ca with nitrate stimulated growth

210pb derived sediment accumulation and mixing rates for the greater puget sound region abstract recent sediment accumulation rates of 46 1200 mg cm2 yr are calculated from excess 210pb activity profiles in 44 sediment cores from 27 sites in the greater puget sound region rates calculated for nine stations in the deeper waters of central puget sound average 480 mg cm2 yr and are greatest between seattle and tacoma near the southern end of this region the standard error of this mean is 113 mg cm 2 yr magnitudes and geographic trends of 210pb derived accumulation rates agree with limited data on sediment inputs and transport paths their accuracy is further supported by several independent approaches including comparison with particle fluxes collected in year long series of sediment trap deployments at two sites accumulation rates are calculated assuming no mixing beneath surface mixed layers of 2 22 cm sediment mixing coefficients in these surface layers average at least 43 cm2 yr four times greater than those reported in open washington coast sediments the difference is attributed to the greater benthic biomass in puget sound sediments particle residence times in surface mixed layers vary from 1 5 to 68 years and introduce corresponding uncertainties in ages of horizons beneath the mixed layers for most of this region these residence times will cause a 20 30 year time lag in achieving an equivalent response of surface sediment chemical concentrations to changes in concentrations in freshly depositing particles for constituents whose stability and phase associations resemble those of 210pb these time lags limit the ability of sediment chemistry monitoring programs to recognize recent changes in composition and fluxes of chemicals to sediments recent fluxes calculated from the product of surface sediment chemical concentration and accumulation rates will be inaccurate for chemicals if their input concentrations have changed in the last 20 30 years

laboratory apparatus for calibrating optical suspended solids sensors abstract an apparatus for testing and calibrating miniature to medium sized optical suspended solids sensors is described stable suspensions of sedimentary particles ranging in size from 10 6 to 4 10 3 m can be produced in water with concentrations exceeding 100 g 1 1 flow velocities in the test volume can be varied continuously from 0 1 to 1 5 m s 1 and samples of suspensions can be withdrawn directly with a peristaltic pump for gravimetric and particle size analyses the apparatus has been used to evaluate the effects of particle size flow speed and air bubbles on the performance of optical backscatterance sensors and transmissometers

implications of simple flexure theory for the formation of saucer shaped sills saucer shaped dolerite sills have been identified in several sedimentary basins they are characteristically sub circular in plan with an inner sill connected to a steeply inclined arcuate sheet extending upwards from the edge of the inner sill and in some cases have raggedly developed flat outer rims by applying elastic plate theory to the overburden we obtain an expression for the maximum radius of a circular sill in terms of emplacement depth excess magma pressure elastic constants of the overburden and the tensile strain at failure this expression predicts that the radius of the flat base of a saucer shaped sill increases with emplacement depth as observed in the western karoo basin south africa some saucer shaped sills display an elliptical morphology from consideration of the flexural strains around the periphery of a horizontal elliptical sill we infer that saucer shaped elliptical sills have been fed from below by feeder dykes oriented along the major axis of the ellipse flat outer rims would have developed at the final stage of each intrusive episode when the excess magma pressure was decreasing towards equilibrium with the overburden load consequently flexural strains would also have decreased so continued intrusion might preferentially occur along a bedding plane

coccoliths in sediment traps from the norwegian sea abstract the fine fraction of surface sediment samples in the norwegian sea shows an unexpectedly high amount of calcareous nannoplankton investigations using time series sediment traps in the lofoten basin 69 n 1983 84 near bear island 75 n 1984 85 and in the fram strait 78 n 1984 85 provided information about the accumulation of this material in relation to the strong seasonality of biological production coccolith identification and counting by means of a scanning electron microscope indicated that the coccolith assemblages in the traps consist almost entirely of the two speciesemiliania huxleyi andcoccolithus pelagicus these species dominated the flux rate of the nannoplankton carbonate a further eight species only made minor contributions to the flux in the lofoten basin a distinct seasonality could be recognized in both standing crop and carbonate flux also the relationship between the two main species and the proportion of intact coccospheres showed an annual cycle in the sample series of the two northerly traps the seasonality was less distinct in general the coccolith flux decreases towards the north this was particularly evident for the smaller speciese huxleyi while the number of massivec pelagicus coccoliths and so the coccolith carbonate flux diminished only slightly additional investigations on water samples from the norwegian sea revealed species compositions that differed greatly from those in the sediment traps this suggests that selective processes change the relative species proportions during sedimentation

surface water dynamics in the reykjanes ridge area during the holocene as revealed by coccolith assemblages abstract the calcareous nannofossil assemblages from sediment core ds97 2p from the reykjanes ridge have been investigated to document oceanographic changes in surface water during the holocene the recorded variations in coccolithophore species assemblages and accumulation rates indicate that the region was subjected to rapid changes of surface water masses throughout the entire holocene coccolithophore assemblages generally are of low species diversity and consist mainly of emiliania huxleyi and coccolithus pelagicus ssp pelagicus two major events occurred at 8 5 7 ka and at 4 5 3 5 ka showing higher coccolith accumulation rates suggesting that the influence of relatively warm atlantic waters via the irminger current was strong in the investigated area the coccolithophore assemblages have been compared with diatom foraminifer and sedimentological records within the same core these data supported by a comparison with previously published proxy records add credit to the hypothesis that holocene changes did not occur uniformly across the north atlantic the results have highlighted the holocene pattern in the north atlantic as a period influenced by strong regionalism with discrepancies in the hydrographical trends and in the distribution of the planktonic proxies

an in situ erosion rate for a fine grained marine sediment near bottom current and particulate concentration data and a theoretical model of sediment resuspension together have led to inferences about the erosional response of a fine grained sediment to bottom stress tidal boundary layer observations made 5 m from the bottom in the main basin of puget sound washington show that currents with speeds exceeding 40 cm s cause an increase in concentration as much as sixfold from a background level of 1 mg 1 when the erosion rate e is given a power law dependence on bottom stress in accord with laboratory fine sediment entrainment measurements the field data and theoretical model together suggest that 4 0 and 1 7 10 6 g cm2 s uncertainty in these values stemming from a variety of factors is discussed the analysis also points to sediment resuspension of material with relatively large settling velocity ws 0 1 cm s taking place against a background of much finer particles and a depth of sediment reworking of approximately 0 3 mm under typical strong flow conditions comparison of this in situ erosion rate with previous laboratory rate estimates shows it to be comparable to rates measured for some freshwater sediments

circulation and sedimentation of suspended particulate matter in new zealand fjords abstract circulation in the new zealand fjords is estuarine with a seaward flowing brackish layer overflowing saline water despite an extremely high rainfall 6000 mm yr 1 terrestrial dediment input is low and concentrations of suspended particulate matter spm rarely exceed 1 mg 1 1 the terrestrial influence is barely detectable anywhere in the fjords spm in near surface waters is dominated by phytoplankton in surface waters spm components remain separate as they settle they are clustered into larger groups by agglomeration faecal pelletization and flocculation phytoplankton produce a secondary spm maximum at the top of the deep zone deep waters are barren of living plankton with clustered spm and broken phytoplankton settling from above the low terrestrial spm input and high organic biogenic concentrations are reflected in low sedimentation rates and high organic carbon content of bottom sediments the estuarine stratification is broken up in the fjord entrances by ocean waves which also resuspend sediment off the entrance sills thereby increasing spm concentrations in bottom waters high spm concentrations are found in basins cut off from the main fjord by shallow sills which inhibit deep water renewal

seasonal cycles in biogenic production and export in northern bay of bengal sediment traps sediment traps in the northern and north central bay of bengal are characterized by highly seasonal fluxes and unusually high efficiency of organic carbon export however the mechanism for high export production remains under debate to evaluate the relationships between production in the photic zone and export processes responsible for the fluxes into the traps over an annual cycle we examine a series of indicators of production regime set in surface waters these indicators include communities of planktic foraminifera and coccolithophores stable isotopic chemistry of foraminifera and coccoliths and the sr ca ratios in coccoliths coccolith and foraminiferal assemblages confirm that the bay of bengal is a region of high productivity coccolithophore communities are dominated to an unusually high degree 90 by the lower photic zone dweller florisphaera profunda a species adapted to high nutrient and low light conditions typical of stratified waters like those induced by the strong halocline in the bay of bengal cyclonic eddy pumping and strong winds during the southwest monsoon swm increase the relative abundance of upwelling indicator species like foraminifera globigerina bulloides and the upper photic coccolithophores globigerina oceanica and emiliania huxleyi however while upwelling and eddy pumping do coincide with high opal and coccolith export in both traps peak organic carbon export precedes the onset of eddy pumping and upwelling indicators these data suggest an alternate mode of production in the bay of bengal which is not driven by upwelling but rather high production deeper in the water column probably by taxa adapted to lower light levels in both traps the pulses of organic carbon export coincide with elevated fluxes of planktonic foraminifera which likely reflect increased primary production consequently while major export pulses of organic carbon coincide with pulses of lithogenic export the pulses of organic carbon export are not likely to reflect simple scavenging of suspended organic carbon by lithogenic pulses rather they reflect increased organic carbon production nonetheless some seasonal changes increase in coccolith export efficiency during the swm are suggested by coccolith sr ca ratios in the northern trap coccolith carbonate export is decoupled from the main pulse of organic carbon export consequently ballasting of organic carbon aggregates by coccolith carbonate does not play a major role in the seasonal cycle of organic carbon export from the photic zone to shallow 800 m traps

particle transport processes in a small marine bay particle transport in elliott bay a 20 km2 embayment in puget sound washington was studied in an integrated program employing shipboard ctd transmissometer observations moored sediment traps and moored transmissometer current meter observations surface and bottom high turbidity layers are present throughout the bay during both summer and winter seasons particles added to the surface layer by river input and phytoplankton production are rapidly advected out of the bay and provide only a minor contribution to the local sedimentation rate the benthic nepheloid layer is maintained not by local resuspension but by particles advected into elliott bay with turbid deep water from the adjoining main basin of puget sound a severalfold drop in mean current speed as main basin water enters elliott bay results in increased particle fallout within the benthic nepheloid layer a high sedimentation rate and the embayment functioning as a sink for particles from throughout puget sound

biogeochemical study of a coccolithophore bloom in the northern bay of biscay ne atlantic ocean in june 2004 abstract the present paper synthesizes data obtained during a multidisciplinary cruise carried out in june 2004 at the continental margin of the northern bay of biscay the data set allows to describe the different stages of a coccolithophore bloom dominated by emiliania huxleyi the cruise was carried out after the main spring phytoplankton bloom that started in mid april and peaked in mid may consequently low phosphate po4

emplacement of dikes sills and crustal magma chambers at divergent plate boundaries abstract a model of dike emplacement at divergent plate boundaries is developed which predicts that below the uppermost 1 3 km of the oceanic crust the number and lengths of dikes in any particular swarm should increase but that the thickness should decrease with depth in the crust these predictions are supported by field observations it is proposed that rapid injections of dikes at divergent plate boundaries may temporarily alter the normal stress field in such a way that at a certain level in the crust subsequent dikes change into sills such sills may develop into crustal magma chambers either when many nearby sills combine into a large one or when an initial sill absorbs the magma of many dikes that enter it in a rapid succession while the sill is liquid for the fastest spreading ridges the initial thickness of a sill that is to develop into a crustal chamber need only attain 20 m whereas at the slowest spreading ridges the initial thickness must exceed 170 m because thin sills are much more likely to form than thick sills the probability of sills developing into crustal chambers increases with dike intrusion frequency hence with spreading rate furthermore the model predicts first that with increasing spreading rate the length of the chamber along the ridge axis should increase and second that the most likely site for magma chambers is at depths of 2 4 km both these predictions are supported by available data

factors controlling the flux of organic carbon to the bathypelagic zone of the ocean 1 particle fluxes measured with time series sediment traps deployed below 2000 m at 68 sites in the world ocean are combined with satellite derived estimates of export production from the overlying water to assess the factors affecting the transfer of particulate organic matter from surface to deep water multiple linear regression is used to derive an algorithm suggesting that the transfer efficiency of organic carbon defined as the settling flux of organic carbon normalized to export production increases with the flux of carbonate and decreases with water depth and seasonality the algorithm predicts 80 of the organic carbon transfer efficiency variability in diverse oceanic regions the influence of the carbonate flux suggests that the ballasting effect of this biogenic mineral may be an important factor promoting export of organic carbon to the deep sea by increasing the density of settling particles however the lack of a similar effect for biogenic opal suggests that factors other than particle density also play a role the adverse effect of increasing seasonality on the transfer efficiency of carbon to the deep sea is tentatively attributed to greater biodegradability of organic matter exported during bloom events in high latitude opal dominated regions with high f ratios and seasonality while a higher fraction of net production is exported a higher fraction of the exported organic matter is remineralized before reaching bathypelagic depths on the other hand in warm low latitude carbonate dominated regions with low f ratios and seasonality a higher fraction of the exported organic matter sinks to the deep sea

hydrothermal venting of greenhouse gases triggering early jurassic global warming abstract the climate change in the toarcian early jurassic was characterized by a major perturbation of the global carbon cycle the event lasted for approximately 200 000 years and was manifested by a global warming of 6 c anoxic conditions in the oceans and extinction of marine species the triggering mechanisms for the perturbation and environmental change are however strongly debated here we present evidence for a rapid formation and transport of greenhouse gases from the deep sedimentary reservoirs in the karoo basin south africa magmatic sills were emplaced during the initial stages of formation of the early jurassic karoo large igneous province and had a profound influence on the fate of light elements in the organic rich sedimentary host rocks total organic carbon contents and vitrinite reflectivity data from contact aureoles around the sills show that organic carbon was lost from the country rocks during heating we present data from a new type of geological structures termed breccia pipes rooted in the aureoles within the shale of the western karoo basin the breccia pipes are cylindrical structures up to 150 meters in diameter and are mainly comprised of brecciated and baked black shale thousands of breccia pipes were formed due to gas pressure build up during metamorphism of the shales resulting in venting of greenhouse gases to the toarcian atmosphere mass balance calculations constrained by new aureole data show that up to 1800 gt of co2 was formed from organic material in the western karoo basin about 15 times this amount of co2 27 400 gt may have formed in the entire basin during the intrusive event u pb dating of zircons from a sill related to many of the pipes demonstrates that the magma was emplaced 182 5 0 4 million years ago this supports a causal relationship between the intrusive volcanism the gas venting and the toarcian global warming

sill processes related to deep water renewal in a fjord observations of the gravitational circulation over the sill at the entrance to puget sound indicate a fortnightly modulation of the two layer flow with a corresponding variation in stratification gravitational circulation and stratification reach a maximum during neap tides and a minimum during spring tides the modulation appears to be a function of the turbulence generation by tidal flow over the sill which varies as a function of tidal amplitude the enhanced gravitational circulation during neap tides augments the flux of dense water across the sill region and episodes of bottom water renewal in puget sound result intrusions of dense water in the main basin of the sound show a fortnightly periodicity with a phase lag appropriate for the propagation of an internal bore from the sill region commencing at the neap tide observations indicate that the intrusions take the form of gravity currents propagating at approximately 20 cm s 1 down the main basin the detailed dynamics of the turbulent mixing processes that modulate the onset of inflow were not resolved in this study but the integrated effect of tidal mixing on the low frequency circulation is clearly demonstrated

the fate of coccoliths at 48 n 21 w northeastern atlantic abstract as part of the joint global ocean flux study program jgofs north atlantic bloom experiment nabe coccolithophore fluxes were recorded over one year period from april 1989 to april 1990 three vertically moored sediment traps synchronized on a 14 day interval were deployed at 48 n 21 w at three water depths at 1 2 and 3 7 km sea floor at 4 4 km we present the results on the vertical variability of coccolith and coccosphere fluxes through the water column calcium carbonate was the largest component of the total mass flux followed by particulate organic matter and opal coccolith and coccosphere seasonal fluxes followed the seasonality of the biogeochemical particle fluxes at all three depths with maxima occurring during the spring particle bloom the decrease in correlation between coccosphere and coccolith fluxes with depth from r 0 98 at 1 km depth to 0 60 at 3 7 km depth documents that disaggregation of the coccospheres occurs during settling in the deeper part of the water column between 1 and 3 7 km water depth annual coccosphere and coccolith fluxes were 1 5 108 and 0 9 10 11 m 2 year 1 respectively at 1 km depth or 3 1 108 and 1 4 10 11 m 2 year 1 including the spring 1990 episode for the 3 7 km trap the corresponding values were 0 5 108 and 1 1 1011 0 6 108 and 1 1 1011 including the partially recorded spring 1990 episode the slight increase in coccolith numbers with water depth can be explained by coccosphere disintegration and lateral influx nevertheless selective dissolution of delicate coccolith species from 1 to 3 7 km water depth occurs e g relative abundances of oolithothus fragilis coccoliths decrease from 3 at 1 km to less than 0 5 at 3 7 km water depth emiliania huxleyi gephyrocapsa muellerae calcidiscus leptoporus and coccolithus pelagicus constitute from 65 at 1 km depth to 95 at 3 7 km depth of the total coccolith assemblages the same four coccolith taxa dominate the fossil assemblages in the underlying surface sediments selective dissolution continues in the sediments most notably the abundance of the solution resistant species c leptoporus increases from 10 to 15 in the trap samples to 15 40 in the sediments annual flux of calcium carbonate in sediment trap samples accounts for about 60 of the total annual mass flux with the coccolith fraction m being about 45 of the annual carbonate flux mean value of 41 at 1 km and 50 at 3 7 km water depth the correlation between the m caco 3 and the calculated coccolithophore and calcisphere caco3 fluxes decreases with depth r 0 92 at 1 km and r 0 86 at 3 7 km indicating that partial dissolution and fragmentation of the delicate less calcified coccolithophore and planktic foraminifera species occurs during settling this fine fragmentation of biogenic caco3 can contribute to the m fraction causing the decrease of correlation with the calculated caco3 fluxes being based only on the flux of intact coccoliths and calcispheres

a top down and bottom up comparison of paleoproductivity proxies calcareous nannofossil sr ca ratios and benthic foraminiferal accumulation rates we investigate whether a relationship exists between organic matter production at the sea surface recorded by nannofossil carbonate sr ca and its consumption on the seafloor measured by benthic foraminiferal accumulation rates bfar a mid pliocene 3 67 3 90 ma section of ocean drilling program site 926 in the northwestern tropical atlantic was sampled where previous work established that the calcareous nannoplankton assemblages vary with insolation linked changes in surface water productivity our results reveal that coarse fraction nannofossil sr ca varies with changes in assemblage composition and may be predominantly controlled by the geochemistry of the warm water oligotrophic genus discoaster bfar also have a positive relationship with sr ca and discoaster abundances implying times of relatively low surface water nutrients coincide with enhanced bfar this result is opposite of what one would expect given the assumption of a direct relationship between primary and export production we speculate that the bfar are stimulated by enhanced organic carbon export associated with ballasting by nannofossil assemblages dominated volumetrically by large robust taxa such as discoaster species these results highlight the complexity of interpretations of bulk nannofossil sr ca ratios as well as bfar data with respect to paleoproductivity

coccolithophore export production species composition and coccolith caco3 fluxes in the ne atlantic and abstract coccolithophores were examined in two sediment traps deployed for one year april 1989 to april 1990 at approximately 1 km water depth in the subtropical ne atlantic at 34 n 21 w station nabe 34 and in the temperate ne atlantic 48 n 21 w station nabe 48 as part of the jgofs north atlantic bloom experiment nabe at both stations maximum coccolith and coccosphere fluxes were recorded during local spring bloom periods the average coccolith and coccosphere fluxes at nabe 34 were 1 12 10 9 m 2 d 1 and 4 90 10 6 m 2 d 1 respectively at this station coccoliths from 51 taxa were identified a marked seasonal change was noticed in relative abundances of emiliania huxleyi and deep photic zone species e huxleyi dominated during spring while in late autumn the coccolith assemblage was dominated by florisphaera profunda and the coccosphere assemblage by g flabellatus and algirosphaera spp emiliania huxleyi was the most abundant species in the overall coccolith and coccosphere assemblages with 69 and 64 respectively at nabe 48 the average daily fluxes were significantly lower with 3 88 10 8 coccoliths m 2 d 1 and 8 45 10 5 coccospheres m 2 d 1 and only 36 taxa were recorded in the trap samples emiliania huxleyi was the dominant species in the coccolith assemblage throughout the year with 72 and showed maximum fluxes during spring 1990 coccolithus pelagicus exhibited a distinct seasonal pattern with maximum fluxes in early june 1989 probably related to the development of a mesoscale cyclonic eddy in the vicinity of the trap site holococcolithophore fluxes were highest during maximum sea surface temperatures in summer the coccosphere assemblage was dominated by gephyrocapsa spp syracosphaera spp and e huxleyi estimated caco3 fluxes of coccoliths coccospheres and calcareous dinophytes were compared with the caco3 content in the fine m fraction the annual mass estimated caco3 flux of coccoliths and coccospheres was 5 1 g m 2 yr at nabe 34 and 2 7 g m 2 yr at nabe 48 and that of calcareous dinophytes 0 9 and 0 1 g m 2 yr respectively these summed mass estimated values contributed on average only 55 at nabe 34 and 60 at nabe 48 to the fine fraction caco3

formation of conical fractures in sedimentary basins experiments involving pore fluids and implications for sandstone intrusion mechanisms large sand intrusions often exhibit conical morphologies analogous to magmatic intrusions such as saucer shaped or cup shaped sills whereas some physical processes may be similar we show with scaled experiments that the formation of conical sand intrusions may be favoured by the pore pressure gradients prevailing in the host rock before sand injection our experiments involve injecting air into a permeable and cohesive analogue material to produce hydraulic fractures while controlling the pore pressure field we control the state of overpressure in the overburden by applying homogeneous basal pore pressure and then adding a second local pore pressure field by injecting air via a central injector to initiate hydraulic fractures near the injection point in experiments involving small vertical effective stresses small overburden or high pore fluid overpressure the fracturing pressure lambda fract is supralithostatic and two dipping fractures are initiated at the injection point forming a conical structure from theoretical considerations we predict that high values of lambda fract are due to strong cohesion or high pore fluid overpressure distributed in the overburden such conditions are favoured by the pore pressure stress coupling induced by both pore pressure fields the dips of cones can be accounted for elastic stress rotation occurring around the source contrary to magmatic chamber models the aqueous fluid overpressure developed in a parent sandbody and prevailing before the formation of injectites may diffuse into the surrounding overburden thus favouring stress rotation and the formation of inclined sheets far from the parent source for experiments involving higher vertical effective stresses thick overburden or low pore fluid overpressure the fracturing pressure is lower than the lithostatic stress and a single fracture is opened in mode i which then grows vertically at a critical depth the fracture separates into two dilatant branches forming a flat cone we make use of a p i v particle imaging velocimetiy technique to analyse plastic deformation showing that these inclined fractures are opened in mixed modes close to the surface they change into steep shear bands where fluids can infiltrate the final morphology of the fracture network is very similar to the common tripartite architecture of various injection complexes indicating that different mechanisms may be involved in the formation of dykes feeder dykes under the sill zones may open as tensile fractures while overlying dykes may be guided by the deformation induced by the growth of sills these deformation conditions may also favour the formation of fluid escape structures and pockmarks c 2011 elsevier b v all rights reserved

variability of subtidal current structure in a fjord estuary puget sound washington simultaneous observations of currents and water properties were made in a section across east passage in puget sound over a 31 day period between march and april 1983 these observations supplemented with ctd profiles shore based wind data and far field current measurements were used to describe the cross channel variability of subtidal currents the mean circulation consisted of seaward flow in the near surface and landward flow below 7 m with a core of maximum velocity at mid depth volume transport was 22 000 m3 s topographic effects force most of the seaward compensating flow through an adjacent channel creating a clockwise circulation around an intervening island empirical orthogonal function analysis was used to describe the spatial structure of current fluctuations at subtidal time scales three circulation modes are evident 1 a near surface upper 20 m wind driven shear 2 a near bottom layer 150 200 m dominated by density currents that propagate up estuary after generation during neap tidal mixing at the entrance sill to puget sound and 3 an intermediate layer 25 75 m influenced by partial refluxing of colvos passage water and modulated at fortnightly periods by nonlinear mixed tides these current observations are the first to show recirculation of seaward flowing water from colvos passage to landward flow in east passage

large scale conical sandstone intrusions and polygonal fault systems in tranche 6 faroe shetland basin abstract kilometre scale sandstone intrusions are important components of many deep water clastic systems they result from the remobilisation and injection of sand during early stages of burial and are commonly found in fine grained mudrocks containing a pervasive polygonal fault network this paper uses three dimensional seismic data from the faroe shetland basin on the uk atlantic margin calibrated to nearby wells to examine the relationship between an extensive system of large downward tapering conical sandstone intrusions to the pervasive polygonal fault network present within the surrounding encasing host mudstones the intrusions were injected upwards during the late miocene through eocene oligocene claystones with a pre existing polygonal fault network to form conical bodies up to 300 m high within the 700 m thick claystone sequence this study shows that polygonal faults and the discordant limbs of conical sandstone intrusions form two distinct dip populations with little overlap that have average dips of 58 and 26 respectively polygonal faults display decreasing dip with increasing depth however conical sandstone intrusion dip is uniform throughout the eocene oligocene succession these observations lead us to conclude that the geometry of conical sandstone intrusions is not greatly affected by the presence of a pre existing polygonal fault network nor is it affected by increased overburden pressure with depth therefore the 10 50 dip range displayed by the limbs of conical sandstone intrusions observed within the study area is a fundamental property of conical sandstone intrusions the presence of a widespread region of conical sandstone intrusions in the faroe shetland basin has important implications for vertical fluid migration in the region the eocene oligocene claystones in the region have very low permeability but the presence of large scale conical sandstone intrusions and any possible feeder systems is likely to provide high permeability fluid conduits through this sequence in effect the otherwise good regional caprock provided by the eocene oligocene claystone sequence is breached by a network of sandstone intrusions possibly resulting in reduced hydrocarbon trapping potential beneath the seal

coccolithophore export production during the 1997 1998 el nino event in santa barbara basin california the response of coccolithophore export production to non el nino and el nino conditions was monitored during a two year period 26 march 1996 3 april 1998 in the centre of the santa barbara basin 34 14 n 120 02 w california borderland during the 1997 1998 el nino the seasonal cycle of the surface water conditions was altered by the presence of a relatively warm low nutrient and low salinity water mass throughout the studied period the total mass flux is dominated by lithogenic components with terrigenous input being highest during el nino period although the annual biogenic sediment fluxes were largely dominated by silica with diatoms as the major contributor to the opal flux the coccolith flux was high during the entire studied period during winter 1998 carbonate fluxes were unusually high for this time of the year moreover a strong positive correlation between organic carbon and opal flux indicates that siliceous phytoplankton production is the most important factor controlling organic carbon flux in the santa barbara basin a positive correlation between carbonate and organic carbon fluxes existed indeed during the final phase of el nino when the correlation between organic carbon and opal fluxes is poor the sinking coccolithophore assemblage was dominated by emiliania huxleyi followed by florisphaera profunda umbilicosphaera sibogae gephyrocapsa oceanica helicosphaera carteri gephyrocapsa muellerae and calcidiscus leptoporus the intensification of el nino 1997 1998 conditions altered the typical hydrographic structure of the santa barbara basin weakening the spring upwelling as reflected by reduced diatom fluxes in contrast the coccolith flux was relatively high during el nino particularly for the tropical species g oceanica that showed a pronounced increase in its flux when the spring upwelling was reduced under el nino conditions in addition we have found that this species has a strong correlation with nitrite phosphate and iron availability in surface water

mixing and cycling of uranium thorium and 210pb in puget sound sediments abstract activity profiles of excess 234 th excess 210 pb 232 th 230 th 234 u and 238 u and 228 232 th ratios determined in eight box cores of sediment from six sites in central puget sound provide new insights into the dynamic nature of solid phase mixing in surface sediments the exchange of 228 ra and other soluble species across the sediment water interface and the cycling of u th and 210 pb in this coastal zone comparison of excess 234 th inventories in sediments with its production rate in the overlying water column indicates a mean residence time of at most 14 days for particles in the central puget sound water column surface sediment horizons with excess 234 th have no excess 228 th which might be used to ascertain sediment accumulation rates over the past decade instead deficiencies of 228 th due to loss of soluble 228 ra from pore water to the overlying water persist to 20 30 cm revealing that exchange of soluble chemicals between pore and overlying waters reaches these depths in the extensively bioturbated sediments of puget sound solid phase u isotope concentrations tend to increase by up to a factor of two with depth in sediments as a result of dissolved u being biologically pumped down into sediments where it is partially removed when conditions become mildly reducing 232 th and 230 th activities and 230 232 th ratios are constant with depth in sediments indicating constant detrital phase compositions and essentially no authigenic 230 th steady state 210 pb depositional activities in and fluxes to puget sound sediments average only about onehalf those for sediments of the open washington coast north of the columbia river mouth primarily because of a much lower supply of dissolved 210 pb in sea waters adverting into puget sound excess 234 th profiles in sediments reveal much more detail about the depth dependency dynamic nature and recent history of solid phase mixing processes than excess 210 pb profiles at least six of eight 234 th profiles show that mixing within the 210 pb defined surface mixed layer is depth dependent in three profiles 234 th derived mixing rates are fastest several centimeters below the sediment water interface indicating greater macro benthic activity at these depths depth dependent mixing coefficients derived from the best fit of a four layer advection diffusion decay model to the 234 th data are consistent with 210 pb profiles determined for the same sediments strongly suggesting that 234 th and 210 pb are mixed equivalently and in a multilayered manner

accumulation rates of recent sediments in puget sound washington abstract sixteen profiles of unsupported 210pb activity from long cores along the axis of the main basin of puget sound show that bottom sediments are accumulating at rates of 0 26 0 03 to 1 20 0 16 g cm 2 yr 1 these rates and seven others published earlier suggest that highest accumulation occurs nearly midway along the length of this tidal current dominated basin bioturbated surface layers of cores are as deep as 40 cm but biologic mixing rates are poorly determined individual 210pb accumulation rates along the axis of the main basin range from approximately one to five times greater than the predicted areal average accumulation rate based on estimates of recent sediment input from adjoining rivers and shorelines

coccolithophore export in three deep sea sites of the aegean and ionian seas eastern mediterranean biogeographical patterns and biogenic carbonate fluxes abstract coccolithophore export fluxes were investigated via the analysis of sinking matter obtained from eastern mediterranean time series sediment traps moored in three open sites of the north eastern mediterranean sea located in the athos basin of north aegean m2 site cretan sea of south aegean m3 site and at ionian sea nestor site the aim of our study was to determine the spatial temporal and seasonal variability in coccolithophore fluxes as well as to estimate coccolith biogenic carbonate contribution to the sedimentation process data from an additional time series sediment trap located in the southwestern black sea were also considered for the comparison of the oligotrophic eastern mediterranean setting with the eutrophic black sea coccolithophore fluxes revealed a highly seasonal pattern during february march in the north aegean peak in late february 2015 85 6 x 105 coccospheres m 2 day 1 27 9 x 108 coccoliths m 2 day 1 during march may in the cretan sea peak in late march 2015 33 7 x 105 coccospheres m 2 day 1 19 5 x 108 coccoliths m 2 day 1 and during february march and may june in the ionian sea peak in late may 2012 14 3 x 105 coccospheres m 2 day 1 1 53 x 108 coccoliths m 2 day 1 the recorded maxima coincide with low sea surface temperatures increased precipitation and high pic fluxes coccosphere fluxes were dominated by emiliania huxleyi comprising 70 of the total abundance in the north aegean and 50 in the cretan and ionian seas syracosphaera pulchra was also prominent in the study sites where its abundance reached 14 in the north aegean and 10 in the cretan and ionian seas respectively florisphaera profunda represented one of the major taxa in the coccolith fluxes of all three eastern mediterranean sites 25 in north aegean 20 in cretan and ionian seas while algirosphaera robusta and umbilicosphaera sibogae were the most abundant among the minor taxa the north aegean sea exhibited a considerably higher coccolith flux when compared to other sediment traps due to the prominent seasonal peak of e huxleyi during winter february march 95 of the total abundance in contrast to the eastern mediterranean sediment traps the time series data from the black sea showed presence of monospecific e huxleyi assemblage increasing its abundance during late september november max 320 x 105 coccospheres m 2 day 1 at least 7 79 x 108 coccoliths m 2 day 1 coccolith flux derived only from coccospheres converted to coccoliths in the eastern mediterranean biogenic carbonate fluxes followed the general pattern of the total mass flux in all investigated areas with the black sea coccolithophore caco3 flux being the lowest due to low the e huxleyi coccolith mass overall in the north aegean sea coccolithophore fluxes are strongly dependent on surface waters nutrients enrichment due to winter vertical water column mixing riverine inputs and black sea water inflows while the fertilization and or formation of fast sinking aggregates due to episodic dust input event are affecting the coccolithophore fluxes in the cretan and ionian seas the intercomparison of the coccolith export fluxes in the studied ne sw mooring transects implies a north south and east west decreasing pattern depending on the variable oceanographic regimes and the associated environmental factors controlling the investigated areas

global cyclostratigraphy a model of carbonate growth patterns abstract cyclostratigraphy is the study of cyclic depositional patterns produced by climatic and tectonic processes a global scale quantitative cyclostratigraphic model is described which simulates carbonate growth patterns controlled by tectonic and climatic processes the model uses seven factors simulating the effects of physical and chemical environments on the deposition rates of carbonate accumulations these factors are sea level change the rate of basement subsidence food supply influence of nutrients available sunlight temperature salinity and dissolved oxygen the factors are considered as functions of climatic and tectonic processes the model also integrates milankovitch induced short term climatic changes with the long term tectonic evolution of basins to examine the potential carbonate accumulation patterns the two dimensional computer model results provided here show that 1 carbonate growth patterns in different climates and under different tectonic processes can be modelled quantitatively 2 carbonate production increases towards the equator decreasing latitude as the temperature and nutrition supply increase in tropical belts and production changes because of expansion or contraction of the tropical belt in different climatic periods 3 when matched with the turbidity the model describes different carbonate accumulation patterns in different climatic patterns 4 at either abnormally high or low salinity carbonate accumulation rates decline sharply and the salinity becomes normal away from the strand line and 5 cyclic sea level changes cause a cyclic change of carbonate accumulation a case study is presented from the upper pennsylvanian of texas the simulation results indicate that carbonate growth patterns observed from field well or seismic data are accurately modelled by the quantitative procedure given here

sinking of coccolith carbonate and potential contribution to organic carbon ballasting in the deep ocean abstract there exists a great need to better understand the controls on organic carbon sequestration to the deep sea by virtue of its role in modulating atmospheric co 2 concentrations recent studies suggest that organic fluxes to the oceanic interior are higher in regions dominated by carbonate sedimentation thus also concluding that relatively heavy carbonate particles are an effective mineral ballast for organic carbon caco 3 production in the pelagic ocean is mainly mediated by foraminifera and coccolithophores but the precise role of these carbonate producers as mineral ballast for organic carbon in the ocean has not yet been tested here we evaluate sediment trap flux data from an array of 13 moorings 15 traps situated in diverse conditions and with global coverage all for organic carbon flux calculated coccolith carbonate flux and fine fraction flux when available discrepancies are recorded between the amount of carbonate fine fraction and calculated coccolith carbonate and there is the need to determine the origin of the unknown caco 3 in the fine fraction the coccolith carbonate flux magnitude is determined not only by the coccolith flux number but also by the carbonate mass of the key species for example very abundant coccolithophore species such as emiliania huxleyi have a very low species specific carbonate mass and are therefore of lower carbonate flux significance than expected intuitively among the main coccolith carbonate species contributors in our sediment trap sites are calcidiscus leptoporus and helicosphaera carteri in that these are all relatively massive compared to their numerical abundances we observed generally positive correlations between calculated coccolith carbonate and organic carbon daily fluxes suggesting that on a global basis there is a ballasting mechanism at work seemingly most efficiently with c leptoporus in the carbonate dominated north atlantic a fairly constant global relationship between annual fluxes of calculated coccolith carbonate and organic carbon implies some uniformity in the pic poc rain ratio however improvements in coccolith carbonate estimation are needed to not only understand this ratio currently but also to help understand future sequestration of organic carbon to the oceanic interior

late quaternary sea surface conditions in the laurentian fan evidence from coccolith and dinocyst assemblages abstract the analyses of coccoliths and dinocysts from the images core md95 2033 collected on the laurentian fan 44 39 87n 55 37 21w water depth 1412 m in the northwest north atlantic provide a new dataset to assess the magnitude of climatic changes during the holocene with a millennial time resolution coccolith and dinocyst data were combined to reconstruct changes in past sea surface conditions in addition the dinocyst assemblages were used to reconstruct the sea surface temperature sst and salinity sss based on the modern analog technique the distribution of the coccolith and dinocyst assemblages suggests a succession of climatic events during the late quaternary and early holocene linked to change in the influence of the labrador current and or the st lawrence river discharge the dinocyst assemblages recorded a thermal optimum during the mid holocene in the late holocene coccolith concentrations show two peaks at 2 3 and 1 1 ky which coincide with the presence of species with different ecological properties likely due to the localized influence of the slope water jet swj current the presence of this current has played a role in the development of the coccolith and dinocyst assemblages and sst fluctuations especially in the last 2 ky overall the interaction between the st lawrence river the swj the lc and the nac has all controlled the sss ssts and the development of the coccolith and dinocyst assemblages confirming a significant regionalism of the entire area

release of methane from a volcanic basin as a mechanism for initial eocene global warming a 200 000 yr interval of extreme global warming marked the start of the eocene epoch about 55 million years ago negative carbon and oxygen isotope excursions in marine and terrestrial sediments show that this event was linked to a massive and rapid approximately 10 000 yr input of isotopically depleted carbon it has been suggested previously that extensive melting of gas hydrates buried in marine sediments may represent the carbon source and has caused the global climate change large scale hydrate melting however requires a hitherto unknown triggering mechanism here we present evidence for the presence of thousands of hydrothermal vent complexes identified on seismic reflection profiles from the voring and more basins in the norwegian sea we propose that intrusion of voluminous mantle derived melts in carbon rich sedimentary strata in the northeast atlantic may have caused an explosive release of methane transported to the ocean or atmosphere through the vent complexes close to the palaeocene eocene boundary similar volcanic and metamorphic processes may explain climate events associated with other large igneous provinces such as the siberian traps approximately 250 million years ago and the karoo igneous province approximately 183 million years ago