foreland thrusts and olistromes on the pre sahara margin of the variscan orogen morocco east of the tizi n test fault one aspect of the southern margin of the north african variscan belt is illustrated in the tineghir traverse it is characterized by appalachian type foreland thrusts pushed southward upon the edge of the sahara platform at the end of the collisional late namurian folding phase this thrust belt is superimposed on a continental paleoslope recorded by huge devonian dinantian olistostromes

the tectonic frame of the variscan alleghanian orogen in southern europe and northern africa abstract by confronting different geological and geophysical data we attempt to reconstruct the variscan alleghanian orogenic belt with especial emphasis on the links between iberia northwest africa and northeast america the northern iberia transect corresponds to the rifted margin of gondwana inverted during the variscan orogeny and overthrust in its westernmost sector by a pile of allochthonous units some of them with oceanic affinity and witnessing an orogenic suture the southern iberia section reveals two sutures at both boundaries of a terrane closely tied to gondwana namely the ossa morena zone the southern boundary of this zone i e the contact with the south portuguese zone is enhanced by amphibolites with oceanic affinity and probably represents the suture of the rheic ocean the moroccan variscides can be divided into i a western external zone namely the coastal block and the central massif ii an internal zone namely the eastern meseta iii an eastern external zone represented in the anti atlas region and iv the african cratonic foreland since neither ophiolites nor eclogites crop out along this transect of the orogen we consider it to be an incomplete transect lacking the main suture zone rheic ocean stratigraphic and faunal affinities between the moroccan meseta on the one hand and the central iberian western asturian leonese and cantabrian zones of iberia on the other hand suggest that they may well have been part of a common pre orogenic domain at the margin of gondwana on the contrary there are no counterparts in morocco for the ossa morena zone thus the northern iberia palaeogeographic zones would prolong in the moroccan meseta through an eastward arcuate structure while the suture of the rheic ocean would do so offshore morocco in our reconstruction an avalonian spur grand banks indentor which included the caledonian sehoul block in northern morocco and the crust of the south portuguese zone in sw iberia played an important role on the kinematic evolution of the orogen as well as on the final configuration of the suture of the rheic ocean this suture would mould around the avalonian spur being laterally translated to southeastern nova scotia newfoundland

distribution of zooplankton biomass at three seamounts in the ne atlantic abstract during different seasons of the years 2003 2005 in the ne atlantic zooplankton were sampled with a mocness multiple opening closing net and environmental sensing system mesh size 333 m above the slopes and summits of seine sedlo and ampere seamounts and at remote reference sites outside the influence of the seamounts far field wet weights of different zooplankton size classes 2 cm were measured night and day hauls were analysed in order to detect diel vertical migrations of the zooplankton as well as a possible trapping effect due to the shallow topography biomass concentrations independent of daytime season and summit height were reduced above the summits at all three seamounts compared to the slope and far field sites no trapping effect or retention of biomass was apparent above the seamounts the vertical distribution patterns of the size class 0 5 cm were nearly absent above the summits of seine and ampere seamounts but considerable numbers were found above the slopes and at the far field sites possible explanations for the observed distribution patterns of zooplankton biomass and size classes are discussed including retention and lateral advection due to the hydrography at the seamounts as well as predation by resident seamount fish

deep sea fluid and sediment dynamics influence of hill to seamount scale seafloor topography abstract deep sea sediments play a central role in a wide range of subject areas a number of important controls on the formation of sedimentary deposits have been studied however to date the impact of submarine landscape geometry as a possible control has received comparatively little attention this seems to be particularly true for intermediate scale topographic features such as abyssal hills knolls and seamounts that can be found in many regions of the global seafloor recent estimates suggest that in the deep open oceans away from continental margins there might be as many as 25 106 abyssal hills knolls and seamounts despite this large number very little is known about how they influence environmental complexity and patchiness biogeochemical fluxes and the formation of sedimentary records this paper reviews the currently known types of fluid flow interactions with abyssal hills knolls and seamounts that could potentially influence the way sediments are formed the main types of relevant flow components are quasi steady to eddying background flow internal lee and near inertial waves barotropic and baroclinic tides and seamount trapped waves previous studies looking into systematic links between fluid dynamics and sediments at hills knolls and seamounts are reviewed finally a case study is presented which aims to combine our current knowledge and investigate whether a given combination of recent fluid flow components leaves a detectable imprint in the recent sediments on and around a short seamount the main conclusions and implications are as follows 1 topographically generated flow field geometries that are composed of a number of different prevailing fluid flow components can be reflected and detected in properties of the underlying sediments 2 tidal and other higher frequency lee wave near inertial components of deep ocean currents can be essential for locally driving total current velocities across threshold values for non deposition erosion resuspension of freshly deposited deep sea sediments moreover there is evidence suggesting that not only maximum current speeds but also intensities of higher frequency tidal and or near inertial current direction variability might control sediment dynamics and sediment formation this relativises the view that current speed is the main or even only controlling factor for sediment dynamics and sediment formation 3 when it comes to the reconstruction of paleo flows these findings imply that certain sedimentary records may well reveal more about variability in the higher frequency flow components than about variability in the basin scale net flow component that often is the focus of paleoceanographic studies 4 single core paleo records from hill seamount or similarly controlled sediment deposits may be biased due to the asymmetry of flow fields around these topographic features to arrive at unbiased paleo records for non fluid dynamic parameters the influence of the flow field geometry would have to be removed from the record first 5 it seems the mechanistic understanding of hill and seamount related flow topography interactions and their links to sediment dynamics is approaching a level that may a facilitate improved interpretation of topographically controlled sedimentary paleo records b help fill in the knowledge gap that exists for functional deep sea biodiversity at intermediate space scales and c improve predictive capabilities for exploration of economically relevant iron manganese fe mn crusts on seamounts

fold interference patterns in the late palaeozoic anti atlas belt of morocco we document two phases of folding within the central part of the late palaeozoic anti atlas chain of morocco a first generation of sw ne folds involve a horizontal shortening of 10 20 accommodated by polyharmonic buckle folding of contrasting wavelengths in ordovician jbel bani quartzites and devonian jbel rich carbonates a second generation of folds with similar style and wavelengths in an e w direction lead to complex interference patterns dome and basins are developed within the jbel rich and within lower cambrian dolomites both folding phases are related to thick skinned uplift of precambrian basement in a laramide style in contrast to the typical rocky mountain foreland style however cover deformation in the anti atlas is mostly decoupled from the undying basement along thick incompetent horizons such as the lower cambrian lie de vin and silurian shales

disintegration of the continental margin of northwestern gondwana late devonian of the eastern anti atlas morocco the devonian early carboniferous sequence in the eastern anti atlas represents a complete record of the last stage of the depositional and tectonic evolution along the northwestern margin of gondwana as a consequence of early variscan block faulting a platform and basin topography was established during the middle and late devonian platforms were covered by condensed cephalopod limestones sedimentation in the basins was mainly argillaceous with calcareous and turbiditic intercalations in the latest famennian early tournaisian the whole area was covered by delta deposits in the south passing into turbidites and olistostromes toward a continental slope farther north this sedimentary and structural evolution reflects the gradual foundering and disintegration of the northwestern continental margin of gondwana prior to the collisional stage in the late visean late carboniferous

directly measured mid depth circulation in the northeastern north atlantic ocean the circulation of water masses in the northeastern north atlantic ocean has a strong influence on global climate owing to the northward transport of warm subtropical water to high latitudes but the ocean circulation at depths below the reach of satellite observations is difficult to measure and only recently have comprehensive direct observations of whole ocean basins been possible here we present quantitative maps of the absolute velocities at two levels in the northeastern north atlantic as obtained from acoustically tracked floats we find that most of the mean flow transported northward by the gulf stream system at the thermocline level about 600 m depth remains within the subpolar region and only relatively little enters the rockall trough or the nordic seas contrary to previous work our data indicate that warm saline water from the mediterranean sea reaches the high latitudes through a combination of narrow slope currents and mixing processes at both depths under investigation currents cross the mid atlantic ridge preferentially over deep gaps in the ridge demonstrating that sea floor topography can constrain even upper ocean circulation patterns

characteristics of surface signatures of mediterranean water eddies in this work we obtain new results on the manifestation of meddies or of other deep eddies at the sea surface further developing the results by bashmachnikov and carton 2012 the quasi geostrophic equations are used to describe a near axisymmetric vortex in the upper ocean forced at its lower boundary by the isopycnal elevation of a moving meddy the solution thus obtained provides a better approximation of the characteristics of meddy surface signals the results show that in subtropics large meddies with dynamic radius rm 30 km are always seen at the sea surface with aviso altimetry that medium size meddies with rm 20 km may be seen at the sea surface only if they are sufficiently shallow and strong while small meddies with rm 10 km generally cannot be detected with the present accuracy of altimetry data the intensity of meddy surface signals decreases to the south with the decrease of the f n ratio the seasonal variation in intensity of the surface signal for northern meddies 45 n is on the order of 2 3 cm but for subtropical meddies 35 n it can be on the order of 5 10 cm the radii of meddy surface signals range from 1 to 2 times the radii of the corresponding meddies for most of the observed subtropical meddies the upper limit should be used numerical experiments show that surface signals of meddies translated with drift are efficiently dispersed by the radiation of rossby waves at the same time for meddies translated by a background current the surface signal does not show strong dissipation

on the role of the azores current in the ventilation of the north atlantic ocean three high resolution ocean circulation models of the north atlantic differing chiefly in their description of the vertical coordinate are used to examine the ventilation of the north atlantic subtropical gyre all the models produce mode waters of realistic densities in the sargasso sea and the european basin but have azores currents of differing strengths which are categorised as strong of realistic transport intermediate and weak these differences have a critical impact upon the ventilation of the gyre most importantly the strong azores current forms an effective barrier to the southward ventilation of eastern north atlantic water from the northern european basin initially driving it southwestwards into the central gyre before turning it back eastwards again in a general cyclonic circulation north of the current the intermediate and weak azores currents instead allow the southward ventilation of this water mass near the european and african coasts the situation in nature appears to be intermediate between these two cases with the azores current acting as a partial block the study also raises the possibility of the azores current forming an advective connection between the sargasso sea mode waters in the western basin and modes of similar densities found in the eastern basin on the southern side of the current although there are high levels of variability in the extent of these lighter modes in the eastern basin in nature this postulate is supported by a number of observational studies in addition the present study also provides some support for the local production of madeira mode water in the eastern basin associated with retroflecting current branches on the southern side of the azores current overall the azores current is therefore likely to have a critical impact upon the ventilation of the subtropical gyre over a large area rather than just locally affecting the potential vorticity and density structure of the upper ocean between subtropical latitudes and the northern european basin the study also contributes to an ongoing community effort to assess the realism of our current generation of ocean models

instability dynamics of a subtropical jet and applications to the azores front current system eddy driven mean flow abstract the azores front is associated with an eastward flowing subtropical jet which coincides with the northern edge of the north atlantic subtropical gyre and forms a southern branch of the gulf stream an intensive study of the eddy driven mean flow induced by the nonlinear instability of the jet has been conducted using a primitive equation numerical model initialized with the summer hydrological fields typical of the azores front the authors show that the mesoscale patterns that appear after a few months are largely determined by baroclinic instability processes the jet and its associated mesoscale turbulence have a strong meridional asymmetry due to the strongly sloping thermocline in general an anticyclonic meander which grows and deforms northwestward generates a pinched off anticyclone while a cyclonic meander which grows and deforms southwestward degenerates in a thin filamental structure that will dissipate before any cyclone can be pinched off the authors propose a mechanism that

interaction of mediterranean water eddies with sedlo and seine seamounts subtropical northeast atlantic abstract during years 2003 and 2004 both sedlo and seine seamounts lying in the area of influence of the mediterranean water outflow in the northeast atlantic were investigated in the framework of the eu funded project oasis analysis of ctd data shows that the levels of major variability in temperature and salinity were confined to the upper ocean layer which is subject to seasonal air sea heat exchange and to the mediterranean water mw level in this paper we concentrate on the latter case and show that the variability observed resulted from mediterranean water eddies meddies colliding with the seamounts combined data from ctd surveys current meter moorings ship mounted adcp and satellite altimetry suggest that during the period of observations there was only one meddy interacting with each of the seamounts on sedlo seamount intensive interaction resulted in the loss by the meddy of about 25 of the salt around the seamount whereas on seine the meddy or portion of it escaped the seamount after performing several rotations around the summit without any significant interaction

devonian extension of the pan african crust north of the west african craton and its bearing on the variscan foreland deformation evidence from eastern anti atlas morocco

new pterosaur tracks pteraichnidae from the late cretaceous uhangri formation southwestern korea numerous footprints of dinosaurs pterosaurs and birds together with arthropod tracks have been discovered in the upper cretaceous uhangri formation which crops out along the south western coastline of south korea this ichnofauna contains the first pterosaur tracks reported from asia the digitigrade tridactyl manus impressions exhibit features of a typical pterosaur hand print the pes impressions however show features that are different from pterosaur footprints reported pre viously there is no visible trace of impressions of individual digits and the toes are triangular or rounded in shape distally without distinct claw impressions as these features clearly distinguish the uhangri tracks from pteraichnus and purbeckopus we assign them to a new genus haenamichnus which accommodates the new ichnospecies haenamichnus uhangriensis the prints are five to six times larger than those of pteraichnus and are currently the largest pterosaur ichnites known they show virtually no trace of the 5th phalange of the pes indicating that they were made by pterodactyloids moreover features of the tracks suggest that they can be attributed to azhdarchids the commonest pterosaur of the late cretaceous the longest pterosaur trackway yet known from any track site length 7 3 m and consisting of 14 pairs of foot impressions was also found in the uhangri formation and suggests that azhdarchids at least were competent terrestrial locomotors the fossil track site at uhangri represents the first occurrence of the tracks of pterosaurs dinosaurs and web footed birds all on the same level this demonstrates that pterosaurs and birds visited the same habitat but the large size disparity suggests that they occupied different ecological niches

hydrothermal origin of devonian conical mounds kess kess of hamar lakhdad ridge anti atlas morocco various interpretations have been proposed for the origin of peculiar cone shaped finely crystalline devonian carbonate mounds of the hamar lakhdad ridge anti atlas morocco ranging from shallow water reefs to deep water mud mounds formed by biogenic and or hydrodynamic processes this study is the first integrated sedimentological and geochemical analysis of these structures the mounds are cone shaped steep sided circular to subelliptical in plan view and exhibit internal crude bedding parallel to the mound9s outer surface they occur in a cluster of 48 mounds on top of a volcanic massif stable isotope analyses of first stage isopachous nonluminescent cement have yielded marine values in contrast the finely crystalline carbonate that makes up the bulk of the mound and the internally sedimented mud between crusts of early marine cements have significantly lower 18 o values whereas values of 13 c are similar to those of the early marine cement strontium isotope ratios also clearly distinguish the nonluminescent early marine cements from the finely crystalline material the 87 sr 86 sr values for the former 0 707 934 0 709 392 are in or near the devonian marine range whereas the ratios for the latter 0 708 515 0 709 656 indicate a more radiogenic sr source on the basis of their lithology architecture isotope geochemistry and clustered occurrence on top of a volcanic pile we propose that the finely crystalline material that forms the mounds and the intermound beds was precipitated from hydrothermal fluids and that accretion of the material was driven by hydrothermal venting

separation of tidal and subtidal currents in ship mounted acoustic doppler current profiler observations a simple method is developed to analyze current measurements obtained from a moving platform the need for this is motivated by the now common use of the ship mounted acoustic doppler current profiler adcp to acquire absolute velocity data during an oceanographic survey of a given region the full potential of this new measurement technique is severely hindered when the presence of high frequency phenomena e g tidal or inertial motions prevents a clear visualization of the lower frequency current structure of interest our analysis method is based on a spatial interpolation scheme using arbitrary functions that allows for the tidal current time variability which then permits the tide induced motions to be subtracted from the adcp data to yield the subtidal current field the method also allows nearby moored and drifter current measurements if available to be combined with the shipboard adcp observations in a single analysis to obtain the best description of the tidal and subtidal currents to illustrate this method we present results from the analysis of adcp data taken during oceanographic surveys in two different continental shelf regions the east china sea and the amazon shelf a 5 day conductivity temperature depth ctd and adcp survey was made in the east china sea near the mouth of the yellow sea during january 1986 there the currents were essentially barotropic and dominated by the semidiurnal tide the adcp derived cotidal chart for the m2 12 42 hours component agrees well with existing charts derived empirically from sea level observations or from regional numerical models the adcp derived steady flow is also consistent with the observed density field and indicates little flow in or out of the yellow sea and a transport of about 1 sv toward the tsushima strait two ctd adcp surveys lasting 21 and 23 days were conducted over the amazon shelf during march and may 1990 simultaneously moored current observations were also obtained at three locations along a cross shelf array 200 km north of the amazon river mouth for a common period of at least 2 months february 12 to april 13 over the shelf tidal and subtidal currents were comparable in magnitude our analysis indicates that the tidal currents were essentially barotropic semidiurnal and polarized in the cross shelf direction increasing in magnitude toward the inner shelf where current values of more than 2 m s are common the adcp derived steady currents were aligned in the along shelf direction and strongly influenced by the north brazil current nbc during both adcp surveys the northwestward flowing nbc was transporting more than 2 sv over the shelf at depths shallower than 100 m

a census of meddies tracked by floats recent subsurface float measurements in 27 mediterranean water eddies meddies in the atlantic are grouped together to reveal new information about the pathways of these energetic eddies and how they are often modified and possibly destroyed by collisions with seamounts twenty meddies were tracked in the iberian basin west of portugal seven in the canary basin during february 1994 14 meddies were simultaneously observed 11 of them in the iberian basin most 69 of the newly formed meddies in the iberian basin translated southwestward into the vicinity of the horseshoe seamounts and probably collided with them some meddies 31 passed around the northern side of the seamounts and translated southwestward at a typical velocity of 2 0 cm s into the canary basin some meddies observed there were estimated to be up to 5 yr old four meddies in the canary basin collided with the great meteor seamounts and three meddies were inferred to have been destroyed by the collision overall an estimated 90 of meddies collided with major seamounts the mean time from meddy formation to a collision with a major seamount was estimated to be around 1 7 yr combined with the estimated meddy formation rate of 17 meddies yr from previous work this suggests that around 29 meddies co exist in the north atlantic therefore during february 1994 we observed about half of the population of meddies

a reinterpretation of dinosaur footprints with internal ridges from the upper cretaceous uhangri formation korea abstract very unusual dinosaur footprints with radial internal ridges from the late cretaceous of southern korea have been the subject of much controversy all footprints are in black laminated mudstone shale and have gently curved cross sections that show deformation of a flexible substrate by dinosaur footprint registration these peculiar patterns have not been recorded at any other site in the world although natural casts of such features have been reported from a few localities each footprint consists of several sectors or pockets partitioned by conspicuous radial ridges these tracks were first interpreted as sauropod manus only tracks supporting roland bird s swimming sauropod hypothesis however our study casts serious doubt on this theory for two reasons first the footprints sometimes exhibit characteristic features such as ungual digit or heel impressions suggesting that the mysterious traces are those of a tridactyl bipedal dinosaur second the unusual tracks are underprints and the internal ridges are molds of radial cracks on the underside of a sand bed on which large bipeds were walking

societal need for improved understanding of climate change anthropogenic impacts and geo hazard warning drive development of ocean observatories in european seas society s needs for a network of in situ ocean observing systems cross many areas of earth and marine science here we review the science themes that benefit from data supplied from ocean observatories understanding from existing studies is fragmented to the extent that it lacks the coherent long term monitoring needed to address questions at the scales essential to understand climate change and improve geo hazard early warning data sets from the deep sea are particularly rare with long term data available from only a few locations worldwide these science areas have impacts on societal health and well being and our awareness of ocean function in a shifting climate substantial efforts are underway to realise a network of open ocean observatories around european seas that will operate over multiple decades some systems are already collecting high resolution data from surface water column seafloor and sub seafloor sensors linked to shore by satellite or cable connection in real or near real time along with samples and other data collected in a delayed mode we expect that such observatories will contribute to answering major ocean science questions including how can monitoring of factors such as seismic activity pore fluid chemistry and pressure and gas hydrate stability improve seismic slope failure and tsunami warning what aspects of physical oceanography biogeochemical cycling and ecosystems will be most sensitive to climatic and anthropogenic change what are natural versus anthropogenic changes most fundamentally how are marine processes that occur at differing scales related the development of ocean observatories provides a substantial opportunity for ocean science to evolve in europe here we also describe some basic attributes of network design observatory networks provide the means to coordinate and integrate the collection of standardised data capable of bridging measurement scales across a dispersed area in european seas adding needed certainty to estimates of future oceanic conditions observatory data can be analysed along with other data such as those from satellites drifting floats autonomous underwater vehicles model analysis and the known distribution and abundances of marine fauna in order to address some of the questions posed above standardised methods for information management are also becoming established to ensure better accessibility and traceability of these data sets and ultimately to increase their use for societal benefit the connection of ocean observatory effort into larger frameworks including the global earth observation system of systems geoss and the global monitoring of environment and security gmes is integral to its success it is in a greater integrated framework that the full potential of the component systems will be realised highlights societies increasingly depend on timely information on ecosystems and natural hazards data is needed to improve climate related uncertainty and geo hazard early warning observatory networks coordinate and integrate the collection of standardised data ocean observatories provide opportunity for ocean science to evolve

strong current events related to a subtropical front in the northeast atlantic long term temperature and current meter records from moorings in the northern canary basin display strong current events with time scales between one and three months and large vertical scales of several thousand meters the data are compared to hydrographic surveys in the area that show a meandering subtropical front the strong current events are found to be related to the passage of the front through the mooring positions an analysis of composite time series for selected depths indicates cases of westward and of eastward propagation of frontal meanders the frontal pattern is also found in geopotential anomalies inferred from historical xbt data sets suggesting that the front is a persistent feature of the density field in two cases strong current events appear to be related to a mediterranean water lens

mass and nutrient fluxes around sedlo seamount abstract we use data from a hydrographic cruise in november 2003 over sedlo seamount in conjunction with historical hydrographic and altimeter data to describe the circulation patterns near the seamount and within the region a mixing model that incorporates two water types and two water masses assesses the water composition within the region and an inverse model provides estimates of mass transports within different water strata eastern north atlantic central water dominates for the upper neutral density n levels n n 27 7 band in the 27 5 n 27 8 band mediterranean water constitutes slightly more than 10 except in the northwestern portion where this water type is less abundant for 27 7 n 27 9 labrador sea water becomes the predominant water mass the results from the inverse model and direct velocity measurements draw a gross picture of central waters flowing northwest along the northeastern margin of the seamount while the net fluxes of labrador sea water are relatively small the central water flow appears to be topographically guided with a region of high eddy kinetic energy over a spur that stretches southeast from the mid atlantic ridge a gross calculation suggests the existence of significant net nutrient transport into the seamount that would support an enhanced level of primary production

dynamics at an elongated intermediate depth seamount in the north atlantic sedlo seamount 40 20 n 26 40 w abstract observations from a five mooring array deployed in the vicinity of sedlo seamount over a 4 month period together with supporting hydrographic and underway adcp measurements are described sedlo seamount is an elongated intermediate depth seamount with three separate peaks rising from 2200 m water depth to summit peaks between 950 and 780 m depth located at 40 20 n 26 40w currents measured in depth range 750 and 820 m the layer close to the summit depth of the shallowest southeast peak showed a mean anti cyclonic flow around the seamount with residual current velocities of 2 5 cm s 1 significant mesoscale variability was present at this level and this is attributed to the weak and variable background impinging flow stronger more persistent currents were found at the summit mooring as a result of tidal rectification and some weak amplification below 1300 m currents were extremely weak even close to the seabed time series of relative vorticity for the depth layer 750 820 m showed persistent anti cyclonic vorticity except for two periods of cyclonic vorticity a mean relative vorticity of 0 06f f the local coriolis frequency was calculated from a triangle of current meters located at the flanks of the seamount modelling results confirmed that anti cyclonic flow above the seamount was likely due to taylor cone generation driven by a combination of steady impinging and tidally rectified flow the closed circulation pattern over the seamount was found to extend to 150 m above the summit level consistent with simple idealised theory and the supporting hydrographic observations at shallower depths

controls of mud mound formation the early devonian kess kess carbonates of the hamar laghdad antiatlas morocco the origin and development of early devonian late pragian to late zlichovian predominantly uppermost zlichovian as indicated by conodont faunas mud mounds of the hamar laghdad area in the eastern antiatlas morocco are controlled by extrinsic and intrinsic factors extrinsic factors include the existence of a paleohigh lochkovian volcaniclastics unidirectional currents and repeated storm events as well as sea level fluctuations intrinsic biologically induced factors are the preferred growth of organisms on the top and the flanks of the mounds because of more favourable ecological conditions and a rapid synsedimentary lithification of the steep mound flanks by interskeletal cementation of auloporid tabulate corals the mounds developed in an epicontinental basin below the wave base but within the range of storms the formation of the mounds started within the uppermost part of the bedded crinoid facies of the kess kess formation with the hydrological accumulation of a bioclastic pile this elevation became settled by crinoids and high diverse tabulate corals producing bioclastic sediment binding activities of the organisms were missing calcareous algae and stromatoporoids are completely absent baffling by thamnoporid tabulate corals might have occurred locally but was not important for the development of the mounds steep slopes to the north and less steep slopes to the south may be the result of north northwest to south southeast trending currents derived from orientation patterns of orthocone nautiloids in the uppermost beds of the kess kess formation a synsedimentary cementation of the flanks possibly triggered by submarine interskeletal cementation of patchily distributed auloporid colonies protected the bioclastic sediment against redistribution by frequent storms indicated by densely spaced eventstone intervals and partly also by the common stromatactis like structures within the mound facies accumulation of more parautochthonous bioclastic sediment within the mounds as compared to the intermound area therefore is caused by a self sustaining system of hydrologic piling of sediment triggered by storms preferred settlement of organisms upon these piles producing bioclastic sediment and coeval biocementation of the growing mound flanks this model differs from existing mud mound models in the lack or only minor significance of binding and baffling in the lack of mound facies sequences and in the greater importance of extrinsic control factors

two years in the life of a mediterranean salt lens abstract a lens of mediterranean water meddy was tracked in the eastern north atlantic for two years with sofar floats the meddy was first found between the canary islands and the azores in october 1984 it center moved in an irregular pattern at speeds of a few cm s 1 and translated 1100 km to the south in two years this meddy was surveyed four times by ctd and velocity profilers and once with the microstructure profiler epsonde when observed during the first two surveys the meddy had a core that was stably and smoothly stratified in both salinity and temperature nearly uniform in the horizontal and was saltier than the surrounding ocean by 0 65 psu the meddy was eroded from its edges top and bottom and lost salt and hat with an e folding time of about one year the salinity at the center remained at its original value during the first year and decreased during the second year evidence was seen for mixing by lateral intrusions double diffusion and turbulence the intrusions are thought to

tidally driven vorticity diurnal shear and turbulence atop fieberling seamount abstract fine and microstructure profiles collected over fieberling seamount at 32 26 n in the eastern north pacific reveal a variety of intensified baroclinic motions driven by astronomical diurnal tides the forced response consists of three phenomena coexisting in a layer 200 m thick above the summit plain i an anticyclonic vortex cap of core relative vorticity 0 5f ii diurnal fluctuations of 15 cm s 1 amplitude and 200 m vertical wavelength and iii turbulence levels corresponding to an eddy diffusivity e 10 10 4 m2 s 1 the vortex cannot be explained by taylor proudman dynamics because of its 0 3fn2 negative potential vorticity anomaly the 0 3f fortnightly cycle in the vortex s strength suggests that it is at least partially maintained against dissipative erosion by tidal rectification the diurnal motions are slightly subinertial turning clockwise in time and counterclockwise with depth over the summit plain they also exhibit a fortnightly cycle in their amplitude pointing to

meddy seamount interactions implications for the mediterranean salt tongue abstract a quasigeostrophic point vortex numerical model is used to explore interactions of eddies and seamounts the ultimate objective of this study is to assess the role of meddy seamount interaction as an input to mediterranean salt tongue maintenance secondary objectives are to clarify the dynamics of meddy seamount interaction the results suggest that meddies survive seamount collisions with 60 70 of their initial cores remaining intact as coherent vortices given observed formation rates it appears meddies in their interactions with seamounts inject between one quarter and one half of the salt anomaly necessary to sustain the mediterranean salt tongue other considerations suggest the anomalous mass flux by meddies is comparable to that due to the mean flow in summary meddies are important to the maintenance of the salt tongue although other mechanisms are needed coherent vortex transport of which meddies are one example is a mesoscale process not well described by the downgradient mix

tidal influence on particulate organic carbon export fluxes around a tall seamount as tall seamounts may be stepping stones for dispersion and migration of deep open ocean fauna an improved understanding of the productivity at and food supply to such systems needs to be formed here the 234th 238u approach for tracing settling particulate matter was applied to senghor seamount a tall sub marine mountain near the tropical cape verde archipelago in order to elucidate the effects of topographically influenced physical flow regimes on the export flux of particulate organic carbon poc from the near surface topmost 100 m into deeper waters the comparison of a suitable reference site and the seamount sites revealed that poc export at the seamount sites was 2 4 times higher than at the reference site for three out of five seamount sites the calculated poc export fluxes are likely to be underestimates if this is taken into account it can be concluded that poc export fluxes increase while the passing waters are advected around and over the seamount with the highest export fluxes occurring on the downstream side of the seamount this supports the view that biogeochemical and biological effects of tall seamounts in surface ocean waters might be strongest at some downstream distance from rather than centred around the seamount summit based on measured vessel mounted adcp and modelled regional flow field aviso internal tides at senghor mitgcm flow dynamics it is proposed that tidally generated internal waves result in a screen of increased rates of energy dissipation that runs across the seamount and leads to a combination of two factors that caused the increased poc export above the seamount 1 sudden increased upward transport of nutrients into the euphotic zone driving brief pulses of primary production of new particulate matter followed by the particles export into deeper waters and 2 pulses of increased shear driven aggregation of smaller slower settling into larger faster settling particles this study shows that under certain conditions there can be an effect of a tall seamount on aspects of surface ocean biogeochemistry with tidal dynamics playing a prominent role it is speculated that these effects can control the spatiotemporal distribution of magnitude and nutritional quality of the flux of food particles to the benthic and benthic pelagic communities at and near tall seamounts

can meddies be detected by satellite altimetry geosat exact repeat mission altimeter data have been used to estimate the sea surface height anomaly relative to a 2 year mean reference surface in the eastern north atlantic ocean horizontal maps of the sea surface height anomaly for various periods were constructed by means of an objective analysis procedure the mean sea level was approximated by the dynamic topography from climatological hydrographic data results were compared to the dynamic topography calculated from hydrographic ground truth data sampled during march 1988 on an eddy resolving station network in the iberian basin despite the low signal to noise ratio of the altimeter data in this part of the ocean the agreement of the altimeter signal with hydrographic measurements is found to be significant individual cyclonic and anticyclonic eddies in the mediterranean outflow are identified in the altimetric maps the information visible in the sea surface height is significantly correlated with the dynamic topography of the layer 500 3000 dbar containing the core of the mediterranean outflow and maximum velocities of the baroclinic eddies the successive development of the identified eddies as studied from a sequence of sea surface height maps indicates a slight westward drift of the most pronounced feature with approximately 1 9 cm s propagation velocity the inferred path of that feature is consistent with additional information from moored current meter data

in situ and remote sensing signature of meddies east of the mid atlantic ridge 1 mediterranean water eddies meddies are thought to play an important climatic role nevertheless their dynamics are not sufficiently known because of difficulties encountered in their observation though propagating below the main thermocline a number of pieces of evidence of sea surface manifestation of meddies are collected the present work is based on joint in situ and altimetry data analyses to prove that the meddies can be followed with remote sensing data for long periods of time the in situ observations are based on data from an oceanographic cruise which crossed three meddies and reanalysis of historical data sets including rafos floats paths suggested methodology permitted us to obtain uninterrupted tracks for several meddies for a period from several months to more than 2 years it was found that the dynamically calm region to the north of the azores current presents favorable conditions for meddy tracking the meddy surface signal may become shattered and difficult to follow during interaction with a strong dynamic structures the azores current surface vortexes or peaking topography theoretical considerations support the observations and lead to the conclusion that the dynamic signature of meddies at the sea surface is an intrinsic property of meddy dynamics

the cretaceous uhangri formation sw korea lacustrine margin facies the uhangri formation forms part of the cretaceous sedimentary sequence deposited in a series of inland basins in the south western korean peninsula it comprises an approximately 400 m thick epiclastic sequence of conglomerate gravelly sandstone cherty mudstone and black shale the entire sequence can be represented by 16 distinctive sedimentary facies organized into four facies associations facies association i is characterized by thick homogeneous brownish siltstone wedge shaped disorganized conglomerate and thinly interlayered gravelly sandstone units the siltstone units were formed by large floods submerging the alluvial fan fringe floodplain whereas the conglomerate and gravelly sandstone units were deposited by sheetfloods and debris flows facies association ii consists of stratified conglomerate gravelly sandstone laminated sandstone and sandstone siltstone couplets which form fining upward cycles some facies units are low angle trough cross bedded and show broad channel geometries this association represents subaqueous delta lobes fed by high and low concentration turbidity currents in the distal delta realm facies association iii is characterized by wedged conglomerate and gravelly sandstone facies with interfingered massive sandstone bounded by scoured bases it represents a delta front where distributary channels and mouth bars are dominant facies association iv consists of laterally continuous sequence of laminated black shale crudely stratified sandstone and convoluted sandstone cherty mudstone this facies association is suggestive of depositional processes controlled by chemical equilibrium resulting from an interaction between density inflows and lake water the cherty mudstone resulted from inorganic precipitation from siliceous solution provided by acidic volcanism the uhangri sequence generally shows a fining upward trend with a transition from alluvial fan fringe coarse grained subaqueous delta to shallow lake the retrogradation was probably due to continuous subsidence related to continental rifting in the oblique slip mobile zone

vivaldi 1991 a study of the formation circulation and ventilation of eastern north atlantic central water abstract a synoptic hydrographic data set comprising 32 full depth ctd casts and 2500 ctd seasoar profiles to 500 m is used to describe the s properties and circulation of central water east of the mid atlantic ridge and between 39 n and 54 n eastward transport of 20 10 6 m 3 s 1 in the north atlantic current turns entirely northwards to the west of 54 n 20 w this transport consists in the upper layers of western north atlantic water freshened at temperatures below 10 c by mixing with subarctic intermediate water northern and southern branches of the north atlantic current are well defined and both turn northwards west of 20 w a further 10 10 6 m 3 s 1 of eastern north atlantic water forms and recirculates anticyclonically to the west of spain south of the north atlantic current and north of 40 n eastern north atlantic water is most weakly stratified east of 20 w and there is clear correlation between weakly stratified pycnostads and positive salinity anomalies relative to western north atlantic water thus eastern north atlantic water is a winter mode water in which strong winter cooling has increased the density and hence also the salinity anomaly at a given temperature near the southern entrance to the rockall trough there is evidence that salinities are also increased by mediterranean water influence circulation south of the north atlantic current is complex there is no evidence for direct ventilation southwards across 40 n where water properties s potential vorticity and cfc 113 and historical data all indicate westward ventilation east of 24 w with weak southward ventilation occurring further west in the vicinity of the azores the circulation pattern suggested is remarkably similar to that proposed by helland hansen and nansen in 1926 the eastern north atlantic geophysiske publicajoner 4 1 76 with anticyclonic circulation of colder eastern north atlantic water north of 40 n meeting warmer water from south of 40 n circulating cyclonically north of the azores current the distribution of pycnostads and s properties between 20 w and 35 w north of the azores indicates alternate bands of western and eastern north atlantic water moving eastward and westward respectively including evidence for westward motion immediately south of the southern branch of the north atlantic current possibly by westward propagation of anticyclonic eddies containing deep pycnostads

mesoscale eddies in the gulf of aden and their impact on the spreading of red sea outflow water abstract the gulf of aden goa in the northwestern indian ocean is the receiving basin for red sea outflow water rsow one of the world s few high salinity dense overflows but relatively little is known about spreading pathways and transformation of rsow through the gulf here we combine historical data satellite altimetry new synoptic hydrographic surveys and the first in situ direct observations of subsurface currents in the goa to identify the most important processes in the spreading of rsow the new in situ data sets were collected in 2001 2003 as part of the red sea outflow experiment redsox and consist of two ctd ladcp surveys and 49 one year trajectories from acoustically tracked floats released at the depth of rsow the results indicate that the prominent positive and negative sea level anomalies frequently observed in the goa with satellite altimetry are associated with anticyclonic and cyclonic eddies that often reach to at least 1000 m depth i e through the depth range of equilibrated rsow the eddies dominate rsow spreading pathways and help to rapidly mix the outflow water with the background eddies in the central and eastern gulf are basin scale 250 km diameter and have maximum azimuthal speeds of about 30 cm s at the rsow level in the western gulf smaller eddies not detectable with satellite altimetry appear to form as the larger westward propagating eddies impale themselves on the high ridges flanking the tadjura rift both the hydrographic and lagrangian observations show that eddies originating outside the gulf often transport a core of much cooler fresher water from the arabian sea all the way to the western end of the goa where the highest salinity outflow water is found this generates large vertical and horizontal gradients of temperature and salinity setting up favorable conditions for salt fingering and diffusive convection both of these mixing processes were observed to be active in the gulf two new annually appearing anticyclonic eddies are added to the previously identified gulf of aden eddy gae prasad and ikeda 2001 and somali current ring scr fratantoni et al 2006 these are the summer eddy se and the lee eddy le both of which form at the beginning of the summer monsoon when strong southwest winds blowing through socotra passage effectively split the gae into two smaller eddies the se strengthens as it propagates westward deeper in the goa while the lee eddy remains stationary in the lee of socotra island both eddies are strengthened or sustained by ekman convergence associated with negative wind stress curl patches caused by wind jets through or around high orography the annual cycle in the appearance propagation and demise of these new eddies and those described in earlier work is documented to provide a comprehensive view of the most energetic circulation features in the goa the observations contain little evidence of features that have been shown previously to be important in the spreading of mediterranean outflow water mow in the north atlantic namely a wall bounded subsurface jet the mediterranean undercurrent and submesoscale coherent lenses containing a core of mow meddies this is attributed to the fact that the rsow enters the open ocean on a western boundary high background eddy kinetic energy typical of western boundary regimes will tend to shear apart submesoscale eddies and boundary undercurrents even if a submesoscale lens of rsow did form in the goa westward self propagation would transport the eddy and its cargo of outflow water back toward rather than away from its source

erosion of a surface vortex by a seamount abstract numerical experiments are carried out on the f plane using a shallow water isopycnal model to analyze the behavior of a surface intensified anticyclonic vortex when it encounters an isolated seamount the advection by the vortex of deep fluid parcels across the isobaths is known to generate deep anticyclonic and cyclonic circulations above and near the bathymetry respectively these circulations are shown to exert a strong shear on the upper layers which causes an erosion of the initial vortex by filamentation the erosion often results in a subdivision of the eddy while the eroded original structure forms a dipole with the deep cyclone and is advected away the filaments torn off from the original core aggregate into a new eddy above the seamount splitting in more than two structures is sometimes observed the erosion process is quantified by the bulk volume integral of the eddy potential vorticity anomaly a sensitivity study to different parameters of the configuration distance between

properties and pathways of mediterranean water eddies in the atlantic abstract data from ship vertical casts nodc data set argo profiling floats coriolis data set and rafos type neutral density floats woce data set are used to study characteristics of meddies in the northeast atlantic in total 241 mediterranean water eddies meddies and 236 parts of float trajectories within meddies are selected for detailed analysis the results suggest that the meddy generation rate at the southern and southwestern iberian peninsula portimao canyon cap st vincent estremadura promontory gorringe bank is 3 times that at the northwestern iberian peninsula porto aveiro canyons cape finisterre and galicia bank meddies generated south of estremadura promontory the southern meddies as compared to those generated north of it the northern meddies have smaller radii smaller vertical extension higher aspect ratio higher rossby number and higher stability stronger potential vorticity anomaly these latter properties result from the southern meddies higher relative vorticity and stronger buoyancy frequency anomaly away from the generation regions meddy drift concentrates along four main paths three quasi zonal paths northern central southern and a path following the african coast coastal the quasi zonal paths are aligned to the isolines of the ambient potential vorticity field several cross path exchanges identified in this work are aligned to topographic rises northward translation of the northern meddies within the north atlantic current to the subpolar gyre is detected within the first 600 km from the coast meddy merger is proved to be a common event this explains the observed difference in radii between the newly generated meddies and those away from the iberian margin the decay of the southern meddies proceeds mainly via the loss of their skirts and does not affect meddy cores until the latest stages the decay of the northern meddies goes in parallel with the decay of their cores in average meddy decay is achieved within 1 2 years although may take over 3 years collisions with the mid atlantic ridge and seamounts sensibly decrease meddy lifetimes meddy decay also speeds up when meddies meet the azores current or the north atlantic current a rapid drop in the number of meddies south of the azores current proves that it represents a dynamic barrier for weak meddies

spreading of labrador sea water in the eastern north atlantic the spreading of labrador sea water lsw in the eastern north atlantic south of 55 n is described on the basis of recent high resolution hydrographic lines and using an inverse model of that basin general circulation the isopycnic salinity anomaly relative to a standard s curve is used to detect the main branches and limits of dominant influence of the intermediate water masses the lsw crosses the mid atlantic ridge at latitudes around 50 n with parts spreading farther eastward and southward one southward pathway along the eastern side of the mid atlantic ridge stands out as an eastern basin counterpart of the western atlantic deep western boundary current an entry into the bay of biscay in its northern part is also evidenced with striking similitudes between two data sets from 1974 and 1989 1990 at the southern limit of the lsw extension in the vicinity of the azores biscay rise a marked front exists basinwide around 1800 m with the more saline deep mediterranean water dmw the inverse model velocity field is consistent with most features of the tracer distributions and allows estimation of lsw transports 6 3 1 2 sv of lsw with salinities lower than 34 94 cross the 35 w meridian eastward between 44 n and 54 n one fourth of which recirculates southwestward in the western basin while another fourth turns northward across 54 n and the remaining half proceeds southward in the eastern basin the model circulation suggests that dmw results from mixing between eastern basin lsw and the overlying mediterranean outflow water most probably through double diffusion we finally describe several mesoscale structures of anomalously high lsw influence south of the lsw dmw front notably one sampled by a rafos float the velocity and potential vorticity fields suggest that these lsw eddies are formed through baroclinic instability at the lsw dmw front

seismites an attempt at critical analysis and classification abstract the main types of seismites are reviewed following the proposed classification and are illustrated by our own case studies the large variety of seismites depends on the sedimentologic hydrodynamic and diagenetic characters of the deposits subject to seismic shocks on a given site generally different types of seismites cane be related to the same seismic event these peculiar but widespread sedimentary structures are not always univocal and may often be related to different causes therefore the structures discussed must necessarily be placed in a detailed geological context

facies patterns and depositional environments of palaeozoic cephalopod limestones abstract in the eastern anti atlas morocco a platform and basin topography was established during the late devonian probably as a result of early variscan tensional tectonics cephalopod limestones were deposited on shallow pelagic platforms platform slopes and shallow slowly subsiding basins on the platform a transition from land areas into nearshore quartzose brachiopod coquinas crinoidal limestones condensed cephalopod limestones and finally into nodular limestones is observed the latter often become disintegrated into incipient debris flows which pass into nodular limestone marl alternations of a shallow basin deeper basins with shale sedimentation lack cephalopod limestones similar facies types also occur in the late devonian of the montagne noire france rheinisches schiefergebirge west germany moravian karst czechoslovakia holy cross mountains poland and in the early carboniferous of the cantabrian mountains spain due to strong late variscan compressional tectonics and limited outcrops detailed facies patterns could not be mapped in these regions but the same facies types as in the eastern anti atlas suggest similar coast platform slope and shallow basin topographies during cephalopod limestone deposition water depth on the platforms was in the order of several tens to about one hundred metres as is inferred from repeated subaerial exposures and distinctive depositional and faunal floral features water depth in the adjacent shallow basins might have reached several hundreds of metres cephalopod limestones represent a typical stage in the evolution of geosynclines characterized by extremely low sedimentation rates 1 5 m m y 1 this stage is preceded by deposition of thick neritic clastics and or carbonates and is succeeded by deposition of deep water clastics or flysch

cephalopod limestone deposition on a shallow pelagic ridge the tafilalt platform upper devonian eastern anti atlas morocco as a result of early variscan tectonic movements and of differential subsidence a platform and basin topography was created along the northern margin of the sahara craton during the late devonian in the moroccan anti atlas mountains the tafilalt platform is an approximately n s running ridge which developed since the late middle devonian it separated a slowly subsiding shallow basin in the east tafilalt basin from a rapidly subsiding furrow in the west mader basin platform deposits are characterized by highly reduced thicknesses shallow subtidal to supratidal deposits in the late frasnian and by unconformities at the lower upper frasnian and the frasnian famennian boundaries after a local transgression over emergent areas in the north water depth probably never reached more than several tens to about 100 m in the lower famennian cephalopod limestones of this age deposited on the platform represent a very diverse facies pattern comprising quartz rich brachiopod coquinas crinoidal limestones thick bedded cephalopod limestones and nodular limestones sedimentation rates ranged from 1 to 5 mm 1000 yr in the late famennian more uniform marl and nodular limestone facies suggest slightly deeper environments platform margins are characterized by higher rates of subsidence debris flow deposits and slump structures in the relatively shallow tafilalt basin marls with intercalated nodular limestones were deposited in the mader basin sandy and calcareous turbidites suggest deeper water conditions in the late devonian during the strunian tournaisian the whole area was overwhelmed by a thick deltaic sequence the general facies distribution is in agreement with depositional models of other upper devonian and lower carboniferous cephalopod limestones in the european variscan orogenic belts in all these cases condensed cephalopod limestones occupy a distinct palaeogeographic position in predictable facies sequences that reflect pre orogenic phases in the variscan geodynamic cycle moreover close parallels exist with condensed sequences in the triassic and jurassic that occur in a very similar position within the alpine orogenic cycle

hercynian compressional deformations of the ahnet mouydir basin algerian saharan platform far field stress effects of the late palaeozoic orogeny n s to nw se trending faults and reverse faults occur within the palaeozoic ahnet mouydir basin of the algerian saharan platform located to the east of the west african pan african suture zone deformation and stratigraphic analysis show that this basin underwent a nne ssw to ene wsw shortening at about the carboniferous permian transition or more probably during the early permian a brief review of the more or less synchronous deformations registered in the neighbouring regions and more specifically around the west african craton illustrates the mechanical coupling between intraplate tectonics and the hercynian plate margins orogenies

on the origin of the azores current the azores current south of the azores archipelago is part of the subtropical north atlantic gyre using an international hydrographic data set we analyze mean and seasonal geostrophic transport fields in the upper 800 m of the ocean in order to determine the origin of the azores current in the western basin and seasonal changes in the related flow geostrophic currents are obtained by using the method applied by stramma 1984 in the eastern basin the azores current is found to originate in the area of the southwest newfoundland rise figure 10 in winter an almost uniform current connects this region of origin with the azores current while a branching into two current bands is observed in summer with the southern band forming a marked cyclonic loop within the upper 800 m all of the transport in the northern band and about 70 of the transport in the southern band recirculates in the eastern basin additionally expendable bathythermograph data from the azores current region indicate an increase of eddy potential energy from winter to summer

the water masses of the central north atlantic in 1983 84 abstract hydrographic surveys carried out in 1983 84 along both sides of the mid atlantic ridge between 24 and 53 n provide a detailed description of the well known north atlantic water masses with particular emphasis on their meridional distribution and zonal dissymetry in the upper layers the dense horizontal sampling resolves the several narrow gulf stream extensions into the ocean interior giving the image in the central water density range of a mosaic of mode waters separated by fronts at intermediate depths a vertical shear in the distributions of the mediterranean water and labrador sea water stands out both water masses having their lower part displaced southwards relative to their upper parts bottom waters containing nearly 20 percent of pure antarctic bottom water are observed at 50 n in the eastern basin in contrast with the western basin where proportions greater than 10 percent were found only south of 36 n along our section this water mass analysis also gives indications that stron

the madeira mode water quasi homogeneous layers in vertical profiles of temperature and salinity in the eastern north atlantic near madeira indicate the existence of a subtropical mode water in the eastern basin temperature sections show a maximum horizontal extent of at least 500 km the frequency distribution analysis of homogeneous layers in a historical xbt dataset shows a mode water formation region near and to the north of madeira this mode water is found at increasing depths and displaced to the west and southwest during the course of the year after its formation by wintertime convection it disappears almost completely due to mixing before the next winter volume estimates suggest that this madeira mode water in the eastern atlantic accounts for 15 20 of the total central water formation in the corresponding density range as obtained from tracer studies in the north atlantic gyre

physical oceanography of the azores front abstract there is a considerable body of evidence for the existence of a permanent front sw of the azores surveys in the summer of 1981 show the structure to penetrate to a depth of 2 000 m and suggest that its meandering is related to the alignment of the atlantis gt meteor seamount chain the total volume transport above 2 000 m is between 10 and 12 106 m3 s 1 towards the east the main water mass contrasts across the front are confined to the upper 400 m of the water column only a small change in mediterranean water strength was seen across the front satellite tracked drogued buoys seeded into the front showed surface speeds of up to 40 cm sec 1 and revealed the formation of a closed cold core eddy some 100 115 km in diameter which propagated westward at 2 2 km day 1 over a 200 day period sea surface temperature contrasts across the frontal boundary are small and together with frequent cloud cover prevent the detection of the front and associated eddies by satellite infra red imagery the front apparently marks the eastward extension of the southern branch of the gulf stream recirculation and the northern limit of the 18 c water mass eddies formed at the front could propagate westward into the interior of the sargasso sea but have not yet been observed to cross the mid atlantic ridge

yeosu dinosaur track sites of korea the youngest dinosaur track records in asia abstract eighty two dinosaur trackways were newly discovered in upper cretaceous lacustrine deposits on islands in the vicinity of yeosu korea most dinosaur tracks occur in marginal lake deposits with polygonal desiccation cracks the dinosaur tracks at the yeosu site include 65 ornithopod trackways 16 theropod trackways and one sauropod trackway the prevalence of ornithopod tracks and the limited occurrence of sauropod tracks at the yeosu site evidently reflect decreased sauropod diversity in the upper cretaceous all ornithopod trackways represent bipeds and most of the ornithopod tracks are similar to caririchnium from other sites of the korean peninsula all fossil wood specimens collected in the study area represent conifers three species of cupressaceous and two species of taxodiaceous conifers and a new species except for one which is a discotyledon it is thus inferred that the southwestern part of the korean peninsula was primarily covered with mesic forests with taxodiaceous trees during the late cretaceous the k ar age of the yeosu tracksite is determined as 81 65 ma camapnian to maastrichtian it indicates that the yeosu track site contains the last records of dinosaurs living in asia consequently semi arid palaeoclimatic conditions together with a large lake as a persistent water source and rich vegetation of gymnosperm trees as food resulted in the preservation of abundant dinosaur tracks in the upper cretaceous on the korean peninsula

hydrological and dynamical characterization of meddies in the azores region a paradigm for baroclinic vortex dynamics the structure des echanges mer atmosphere proprietes des heterogeneites oceaniques recherche experimentale semaphore oceanographic experiment surveyed a 500 500 km2 domain south of the azores from june to november 1993 and collected hydrological data float trajectories and current meter recordings this data exhibited three intrathermocline eddies of mediterranean water meddies two of them being repeatedly sampled their hydrological and dynamical properties are quantified here by an isopycnic analysis for the three meddies intense temperature and salinity anomalies up to 4 c and 1 1 practical salinity units psu are observed extending vertically over up to 1000 m and centered around 1000 m horizontally these anomalies spread out to radii of 50 60 km while the maximum azimuthal velocities 30 cm s 1 as computed by geostrophy lie only at 35 40 km from the central axis these meddies followed curved trajectories with drift velocities up to 7 5 cm s 1 under the influence of the neighboring mesoscale features cyclonic vortices or azores current meanders the three dimensional structure of potential vorticity in and around these features evidences their complex interactions northwest of the domain a meddy was coupled to a subsurface anticyclone forming an aligned vortex it later interacted with the azores current creating a large amplitude northward meander by vertical alignment of vorticity in the southeastern part of the domain another meddy was vertically aligned with an anticyclonic meander of the azores current and horizontally coupled with a cyclone of large vertical extent these two features as well as a small warm and salty fragment in their vicinity seem to result from the southward crossing of the meddy under the azores current these observations illustrate previous theoretical studies of baroclinic vortex dynamics

meddies and decadal changes at the azores front from 1980 to 2000 twenty years of time series observations from the deep sea mooring kiel276 are used to obtain information on the frequency and propagation of meddies mediterranean water eddies on long term changes in flow properties and on a possible relation to the north atlantic oscillation the mooring was set at the nominal position 33 n 22 w at a water depth of more than 5200 m in the northern canary basin it is located near the southern boundary of the azores current ac which is part of the north atlantic subtropical gyre and also in the large scale mediterranean water mw tongue originating from the strait of gibraltar the amplitudes of time varying vertical quasi geostrophic modes and the correlation of current and temperature changes at levels in the mw and the north atlantic central water above are used to identify meddies a total of 10 meddies passed the mooring during the period 1980 2000 half of the events can be related to earlier observations directional changes in meddy related velocities are used to estimate speeds and directions of meddy propagation directions of propagation are very homogeneous with all the 10 meddies observed propagating with a southward velocity component within a sector of 90 and typical speeds are 2 3 cm s meddy occurrence was uneven in time with six meddies found during the first four years and only four meddies during the remaining 16 years decadal changes show the annual mean and the fluctuating kinetic energy levels at the site changing from lower values in the 1980s to high values in the 1990s this change appears to be correlated with variations in the north atlantic oscillation nao index with a delay in oceanic response of about 3 years a conceptual model of ac meanders is used to identify meander signals in the upper layer time series the ac axis appears to be closer to the site during the 1990s than during the preceding decade and indicates a southward or southwestward displacement of the ac with increasingly positive values of the nao index meddy frequency is lower when the ac gets closer from the north a reduction in meddy occurrence in the region just south of the ac is possibly caused by the shear induced blocking of some meddies crossing the front from the north

picoplankton and nanoplankton composition on and around a seamount affected by an eddy dipole south of madagascar abstract picoplankton and nanoplankton community abundances were sampled on and around a seamount located on the madagascar ridge in november 2016 prochlorococcus synechococcus picoeukaryote and nanoplankton community abundances both on the seamount and in the immediate vicinity approximately 100 km surrounding it were analysed using flow cytometry the original aim of the study was to estimate whether or not the seamount had an effect on the picoplankton and nanoplankton community distribution however coupled altimetry and in situ ship data indicated that a dipole eddy was also sampled during this time which had a substantial effect on the results results reveal that picoeukaryotes contributed the most to carbon biomass within the anticyclone showing higher abundances in the stations situated within the southern slopes of the seamount which also fell within the anticyclone the southern slope of the seamount contained higher synechococcus prochlorococcus and picoeukaryote abundances whereas nanoplankton dominated in the cyclonic eddy species composition and abundance was significantly different on versus off the seamount driven by nanoplankton biomass these results indicate significantly high abundance above the slopes of the seamount driven by picoeukaryotes which seem to be amplified by the dipole presence the resulting variability in microbial abundance both on the southern slopes of the seamount as well as within the dipole has far reaching implications with regard to larger organism proliferation and carbon export during such events in this region

large structures and temporal change in the azores front during the semaphore experiment the structure des echanges mer atmosphere proprietes des heterogeneites oceaniques recherche experimentale semaphore mesoscale experiment took place from july to november 1993 in the northern canary basin where the circulation is dominated by the eastward flowing azores current ac a large data set was acquired from three hydrographic arrays phases 1 2 3 current meter moorings surface drifters drogued at 150 m and 2000 m deep rafos floats the analysis confirmed the large scale observations previously made in this region but also provided new insights into fine scale dynamics of the ac the front was observed over the 6 month period it was narrow 100 km and mostly surface intensified velocities reaching 40 50 cm s 1 whereas at the beginning of the experiment phase 1 the ac was mainly zonal with weak oscillations large meridional meanders were observed from phase 2 until the end of the experiment they seem to be related to the arrival of two mediterranean eddies meddies which interacted with the ac kase and zenk 1996 tychensky and carton this issue the front had a deep dynamical signature down to 2000 m with a 16 18 sverdrup sv volume transport 0 2000 m depth integrated the southward recirculation branch of the ac near 22 degrees 23 degrees w klein and siedler 1989 corresponds to meridional transport of 5 6 sv then 4 5 sv of these waters are recirculating westward along 31 degrees 32 degrees n some interesting new oceanographic results were obtained by examining the rafos float trajectories over the abyssal plain the circulation is similar to that observed at the surface with mean velocities of about 1 3 cm s 1 and eddy kinetic energy 4 cm 2 s 2 in agreement with the analysis of current meter data this reveals a significant barotropic component in the azores madeira flow field of roughly 3 3 5 cm s 1