influence of sea ice on the thermohaline circulation in the arctic north atlantic ocean a fully prognostic coupled ocean ice model is used to study the sensitivity of the overturning cell of the arctic north atlantic system to sea ice forcing the strength of the thermohaline cell will be shown to depend on the amount of sea ice transported from the arctic to the greenland sea and further to the subpolar gyre the model produces a 2 3 sv increase of the meridional circulation cell at 25n at the simulation year 15 corresponding to a decrease of 800 km in the sea ice export from the arctic previous modeling studies suggest that interannual and decadal variability in sea ice export of this magnitude is realistic implying that sea ice induced variability in the overturning cell can reach 5 6 sv from peak to peak

upper mantle reflector structure and origin beneath the scottish caledonides the mantle reflector pattern beneath the scottish and irish caledonides is perhaps the most widely studied individual structure in the uppermost continental mantle previous investigations interpreted the reflector as a thrust related to the caledonian orogeny silurian early devonian or as a normal fault or shear zone active during post caledonian e g devonian or permo triassic extension this study uses all available deep seismic reflection data to map mantle reflector structure along the caledonian orogen and to constrain better its geometrical and tectonic relation to regional geology the distribution of the mantle reflector shows that it is not spatially related to either caledonian compressional or subsequent basin extensional structures in a simple way a structural contour map shows two distinct discontinuous surfaces consisting of a steeply plunging antiform synform pair beneath the west orkney basin north of the scottish mainland and the faeroe shetland basin west of shetland respectively separated by an inferred zone of structural disruption a working hypothesis for this study is that these two surfaces may have once been part of a continuous more or less planar surface that has been offset and deformed by either or perhaps a combination of two processes 1 differential extension of crust that was at least partially coupled to the uppermost mantle beneath the west orkney and faeroe shetland basins 2 a broad approximately orthogonal i e east west trending zone of simple shear corresponding to the disrupted zone that was largely confined to the upper mantle but reactivated to deform the crust our results also suggest that the mantle reflector structure may be inherited from neoproterozoic events associated with rifting of the laurentia baltica supercontinent

cenomanian turonian carbon isotope events recorded in terrestrial organic matter from northern japan carbon isotopic fluctuations recorded in terrestrial organic matter from the upper cretaceous cenomanian turonian succession of hokkaido japan show a remarkably similar pattern to isotopic fluctuation in carbonate carbon reported from southern england and the italian apennines chronological correlation for the cenomanian turonian section of japan is based on planktonic foraminiferal biostratigraphy with some additional data from macrofossils allowing a detailed comparison of isotope stratigraphies for japan and europe three distinct features of the isotope profile namely a positive spike near the cenomanian turonian boundary a shoulder in the lower middle turonian and a level segment in the middle upper turonian are observed in japan these features are biostratigraphically comparable and correlative with isotope profiles reported from europe the single factor influencing isotopic composition of both terrestrial organic carbon and marine carbonate carbon is isotopic change in the global co2 reservoir of the ocean atmosphere system if these three carbon isotope features are synchronous they may be inferred as having been caused by global phenomena and as providing global high resolution chemo stratigraphic markers carbon isotope stratigraphy could be an important bridge between terrestrial inland sequences and marine sequences

interpentadal variability of temperature and salinity at intermediate depths of the north atlantic ocean 1970 1974 versus 1955 1959 we have composited historical hydrographic observations for the world ocean for two pentads 1955 1959 and 1970 1974 and have objectively analyzed these data for the purpose of studying the temporal variability of temperature and salinity in the north atlantic ocean the subtropical gyre 500 1300 m of the north atlantic was colder and fresher during 1970 1974 compared to 1955 1959 the relatively large changes in temperature and salinity on constant depth surfaces in the subtropical gyre were due to upward displacements of isopycnal surfaces at intermediate depths the eastern portion of the subarctic gyre was also colder and fresher during the 1970 1974 pentad in contrast the western portion of the subarctic gyre exhibited higher temperatures and salinities during 1970 1974 compared to 1955 1959 characteristic differences in temperature and salinity for both gyres were 0 5 c and 0 025 respectively analysis of changes in potential vorticity indicates that in the subtropical gyre potential vorticity increased in all density layers above the 26 5 surface suggesting that convection in this region may have been shallower in 1970 1974 compared to 1955 1959 below the 26 5 surface potential vorticity decreased through the 27 3 surface indicating that deeper than normal convection may have formed the water masses in these layers at 250 m depth relatively large changes in temperature and salinity occurred along the line of maximum climatological mixed layer depth that extends northeast to southwest across the north atlantic ocean

late cretaceous evolution of the judean mountains as indicated by ostracodes the judean mountains anticlinorium israel a part of the syrian arc fold system underwent several phases of compressional folding uplift and faulting in post turonian through quaternary times this study emphasizes the earliest tectonic phase of eariy late coniacian age ostracode biozonation clearly indicates the duration and extension of senonian sedimentation and timing of onlap over the evolving judean mountains structure

annual variations of sea surface elevation and currents over the scotian shelf and slope abstract topex poseidon t p altimeter data over the period 1992 98 have been analyzed to examine annual variability of sea surface elevation and currents over the scotian shelf and slope a modified orthogonal response analysis is used to derive the annual cycle while simultaneously removing the residual tides and other dynamical processes at the appropriate t p alias periods an evaluation of the m2 and k1 alias variations is carried out suggesting notable tidal correction errors off cape cod and over georges bank the along track sea surface slopes which represent surface geostrophic current components normal to the track are estimated on selected t p ascending and descending ground tracks the annual altimetric sea level harmonic is compared with steric height anomalies and wind driven setup the comparison indicates that the altimetric sea surface elevation variability is dominated by the baroclinic and associated barotropic component and supplemented by the wind driven and remotely forced comp

subtidal response of scotian shelf circulation to local and remote forcing part i observations abstract data collected during the canadian atlantic storms program casp suggest that two primary current regimes exist on the scotian shelf during winter moorings inside the 100 m isobath feature currents that are parallel to the general bathymetry and have small eastward mean velocities the time varying part of the flow is nearly rectilinear alongshelf at typical maximum velocities of 0 2 0 3 m s 1 and oscillates on 2 5 day periods in response to meteorological forcing the current at locations beyond the 100 m isobath exhibits a persistent westward flow of about 0 3 m s 1 denoting the dominance of the nova scotian current although smaller magnitude along and cross shelf fluctuations occur at synoptic frequencies flow in both regions is largely uniform with depth at this time of year the velocity response to local and remote sources of forcing was examined using a frequency dependent multiple regression model flow is dominated by nonlocal forcing at 0 2 cpd alongshelf wind stress is t

the relationship between u s east coast sea level and the atlantic meridional overturning circulation a review scientific and societal interest in the relationship between the atlantic meridional overturning circulation amoc and u s east coast sea level has intensified over the past decade largely due to 1 projected and potentially ongoing enhancement of sea level rise associated with amoc weakening and 2 the potential for observations of u s east coast sea level to inform reconstructions of north atlantic circulation and climate these implications have inspired a wealth of model and observation based analyses here we review this research finding consistent support in numerical models for an antiphase relationship between amoc strength and dynamic sea level however simulations exhibit substantial along coast and intermodel differences in the amplitude of amoc associated dynamic sea level variability observational analyses focusing on shorter generally less than decadal timescales show robust relationships between some components of the north atlantic large scale circulation and coastal sea level variability but the causal relationships between different observational metrics amoc and sea level are often unclear we highlight the importance of existing and future research seeking to understand relationships between amoc and its component currents the role of ageostrophic processes near the coast and the interplay of local and remote forcing such research will help reconcile the results of different numerical simulations with each other and with observations inform the physical origins of covariability and reveal the sensitivity of scaling relationships to forcing timescale and model representation this information will in turn provide a more complete characterization of uncertainty in relevant relationships leading to more robust reconstructions and projections

decadal shift of nao linked interannual sea level variability along the u s northeast coast abstractrecent studies have linked interannual sea level variability and extreme events along the u s northeast coast nec to the north atlantic oscillation nao a natural internal climate mode

orbital time scale intra platform basin correlation carbon isotope stratigraphy and sea level history of the cenomanian turonian eastern levant platform jordan two cenomanian turonian boundary ctbe sections kb3 and gm3 of the karak silla intra platform basin of the eastern levant carbonate platform jordan are correlated based on high resolution calcimetry kb3 contains black shales with over 7 wt total organic carbon toc gm3 was deposited at shallower water depth and reveals four conspicuous gypsum beds used for sea level reconstruction spectral analysis of carbonate content and toc reveals forcing mainly by the 100 ka cycle of earth s orbit eccentricity whole rock stable carbon isotope data show a conspicuous positive d13c excursion representing the oceanic anoxic event 2 oae2 the carbon isotope records of kb3 and gm3 correspond well with the cycles in the dc record of the global stratotype gssp at pueblo usa the gssp orbital timescale thus can be applied to the jordan record furthermore all stable isotope events defined in the english chalk reference record are recognized in jordan our orbital model for the jordan sequence stratigraphical framework reveals approximately 1 2 0 2 ma duration of a third order sequence proposed to represent one cycle of the long obliquity 1 2 ma this longterm period is superimposed on three fourth order fluctuations of 400 ka length long eccentricity fourth order sea level fluctuations each of which comprises four carbonate cycles 100 ka eccentricity fifth order sea level fluctuations demise of the levant platform occurred during the phase of decreasing dc values after oae2 in the interval between the cenomanian turonian c t boundary and the end of the early turonian the levant carbonate platform deposits of central jordan represent a textbook like shallow marine platform setting subdivided into intra platform basins during cenomanian turonian c t times kuss et al 2003 the morphological structuring by these basins induced lithologically highly variable successions especially during black shale deposition that preferably occurred in deeper subbasins a correlation of these different successions is possible by means of high resolution calcimetry and stable carbon isotope stratigraphy in this paper we present such a correlation that enables the study of three research aspects a linking different palaeoenvironments over the c t boundary interval b refining the sequence stratigraphic model by constructing an orbital time scale c correlating the successions to the global record exemplified for the well dated c t boundary interval in order to eliminate ambiguities in the local stratigraphy furthermore our data support the global picture and estimates of duration of the c t boundary interval that includes the global oceanic anoxic event 2 oae2 the duration of oae2 has been the matter of many studies in recent years resulting in a range of values from 320 to 960 ka obradovitch 1993 sageman et al 2006 partly caused by considering different intervals an orbital timescale for the pueblo stratotype section was given by sageman et al 2006 providing a precise time measure for the period investigated in our study in addition a comprehensive study of stable carbon isotope records in europe was given by jarvis et al 2006 providing a detailed set of isotope events suitable for global correlation recently an orbital model was also presented for the wunstorf germany section voigt et al 2008 this record correlates well with the present results and can be used to support the new hypothesis put forward in the present paper regarding the orbital trigger of third order sequences

north atlantic sea level and circulation summary monthly sea levels from an extensive array of north atlantic tide gauges 26 50 n are examined the spatial scale of the sea level variations and the reasons for them are discussed one application of such a study is clearly in the design of a tide gauge network for monitoring eustatic changes of sea level the spatial scale of the sea level changes is large there is a coherent sealevel signal which can be traced along the eastern boundary of the north atlantic from newlyn 50 n to tenerife 28 n there are also two distinct groupings of tide gauges along the western boundary separated by cape hatteras the contribution of local air pressure and wind stress is quantified at each gauge through multiple regression techniques and the gains are then interpreted in terms of recent theoretical and numerical modelling studies for example the gains suggest that the wind forced boundary current along the nova scotian shelf is trapped to within about 16 km of the coast the influence of local meteorology cannot account for the large scale modes of variability the coherent signal along the eastern boundary is correlated with changes in the sverdrup transport of the north atlantic and hence the large scale wind field the two modes on the western boundary appear to be related to baroclinic boundary current variations the newlyn sea level record is finally corrected for some of the above effects to illustrate the utility of such a residual series in the identification of eustatic changes and vertical crustal movement

enhanced productivity led to increased organic carbon burial in the euxinic north atlantic basin during the late cenomanian oceanic anoxic event 1 three cenomanian turonian c t 93 5 ma black shale sections along a northeast southwest transect in the southern part of the proto north atlantic ocean were correlated by stable carbon isotope stratigraphy using the characteristic excursion in 13c values of both bulk organic matter om and molecular fossils of algal chlorophyll and steroids all three sites show an increase in marine organic carbon oc accumulation rates during the c t oceanic anoxic event oae the occurrence of molecular fossils of anoxygenic photosynthetic green sulfur bacteria lack of bioturbation and high abundance of redox sensitive trace metals indicate sulfidic conditions periodically reaching up into the photic zone before as well as during the c t oae during the c t oae there was a significant rise of the chemocline as indicated by the increase in concentrations of molecular fossils of green sulfur bacteria and mo al ratios the presence of molecular fossils of the green strain of green sulfur bacteria indicates that euxinic conditions periodically even occurred at very shallow water depths of 15 m or less during the c t oae however bottom water conditions did not dramatically change as indicated by more or less constant v al and zn al ratios at site 367 this suggests that the increase in oc burial rates resulted from enhanced primary productivity rather than increased anoxia which is supported by stable carbon isotopic evidence and a large increase in ba al ratios during the c t oae the occurrence of the productivity event during a period of globally enhanced organic carbon burial rates i e the c t oae points to a common cause possibly related to the formation of a deep water connection between north and south atlantic basins

integrated palynological organic geochemical and sequence stratigraphic analyses of the middle to upper cenomanian hydrocarbon reservoir source abu roash g member a depositional model in northwestern egypt abstract the current investigation provides further insight into the petroliferous characteristics of the abu roash g member which is regarded as an important rock unit for the egyptian oil industry forty seven samples covering the g member were selected from the bed 14 1 and bed 2 4 wells in the abu gharadig basin and from the abu tunis 1x well in the matruh basin both of which are located in the north western desert an independent dating of the g rocks of bed 2 4 by benthic foraminifera and ostracods in addition to palynological dating suggests a middle late cenomanian age and provides the biochronostratigraphic framework for the sequence stratigraphic analysis analysis of the vertical distribution of particulate organic matter defines three palynofacies types pf pf 1 represents the basal g where shales of the bed wells and calcareous shale of abu tunis 1x were deposited during a relative sea level rise in an outer middle shelf environment that experienced a notable high primary productivity prevailing reducing suboxic anoxic conditions supported preservation of very high amounts of amorphous organic matter aom in pf 1 pf 2 is equated to shales of the middle g of bed 14 1 and bed 2 4 and to calcareous shales and limestone of the upper g in abu tunis 1x pf 2 was deposited during a relative sea level fall in an inner middle shelf setting under better developed suboxic anoxic conditions pf 3 corresponds to the upper g of bed 14 1 and bed 2 4 and represents the shallowest setting where sandy and silty shales were deposited during a pronounced sea level fall in an inner shelf environment the same suboxic anoxic conditions were prevailing during deposition of pf 3 three bioevents were recorded which could be of palaeoecological and or biostratigraphic significance these are senegalinium aenigmaticum dinopterygium cladoides peak dinopterygium cladoides dinopterygium alatum peak and an acme of classopollis brasiliensis sequence stratigraphy of a transect of the four studied sections was carried out to understand the response of the particulate organic matter distribution and depositional system to the sea level changes three third order depositional genetic sequences were recognized and correlated with the global sea level curve kce 2 kce 3 and kce 4 the early highstand systems tract ehst of the genetically related kce 3 in all wells is characterized by relatively rich organic matter where combined remarkably low water circulation and insignificant dilution of organic matter with coarse terrigenous material probably supported good preservation of organic matter spatial distribution of the g rocks shows lateral facies changes this was inferred from sedimentation of an organic poor avg 0 8 toc wt coarse clastic sandy shales facies in the studied area in abu gharadig basin sedimentation changes laterally into a northeast and northwest organic rich finer clastic shale calcareous shales and argillaceous limestone facies in the western matruh basin the robust anoxic conditions and very low dilution of organic matter by terrigenous influx enhanced the organic richness avg 2 4 toc wt of these rocks which resulted in the formation of promising hydrocarbon source rocks thus for a successful hydrocarbon exploration in the north western desert the promising source section of the g member would be associated with shales calcareous shales and argillaceous limestone lithologies its depositional environment is mainly confined to outer middle and inner middle shelf settings that have widespread suboxic anoxic conditions and show ehst pattern in contrast the regressive intervals that are denoted by the lowstand systems tract lst and or the late hst lhst typify the relatively coarse clastics as good quality reservoir rocks that are characterized by poor organic richness due to dilution with terrigenous influx

satellite detection of an unusual intrusion of salty slope water into a marginal sea using smap to monitor gulf of maine inflows abstract satellite salinity from the soil moisture active passive smap mission and in situ observations are used to diagnose the source of a significant increase in warm and salty surface water entering the gulf of maine gom in the winter of 2017 2018 smap salinity anomaly data indicate that this event was related to a salty feature that moved along the northwestern atlantic shelf break from near the grand banks southwest towards the gom over eight months before entering the gulf in december 2017 to january 2018 satellite altimetry sea surface salinity and sea surface temperature data suggest that before entering the gom the salty feature interacted with gulf stream meanders and eddies several times helping to sustain the water mass it is likely that feature interactions with a warm gulf stream meander took place in the fall of 2017 helping to advect high salinity water onto the shelf and then into the gom as a surface trapped feature in late fall 2017 according to satellite salinity data this episode led to significant salinification about 1 psu in the northeastern gom interior gom buoy salinity data agree in showing four months of increased gom salinity of the upper 50 m starting in november 2017 buoy t s analyses characterize this surface inflow as modified warm atlantic slope water typically seen only below 100 m and previously unobserved at the surface in the 15 year buoy record this new salty water circulated cyclonically along the gom coastline and mixed into the deeper gulf through february 2018 its intrusion may have also enhanced the cyclonic winter circulation in the gulf gom surface salinity anomalies ended abruptly in early march 2018 coincident with the occurrence of a bomb cyclone and its associated strong upper ocean mixing

wind induced interannual variability of sea level slope along shelf flow and surface salinity on the northwest atlantic shelf in this study we examine the importance of regional wind forcing in modulating advective processes and hydrographic properties along the northwest atlantic shelf with a focus on the nova scotian shelf nss gulf of maine gom region long term observational data of alongshore wind stress sea level slope and along shelf flow are analyzed to quantify the relationship between wind forcing and hydrodynamic responses on interannual time scales additionally a simplified momentum balance model is used to examine the underlying mechanisms our results show significant correlation among the observed interannual variability of sea level slope along shelf flow and alongshore wind stress in the nss gom region a mechanism is suggested to elucidate the role of wind in modulating the sea level slope and along shelf flow stronger southwesterly northeastward winds tend to weaken the prevailing southwestward flow over the shelf building sea level in the upstream newfoundland shelf region whereas weaker southwesterly winds allow stronger southwestward flow to develop raising sea level in the gom region the wind induced flow variability can influence the transport of low salinity water from the gulf of st lawrence to the gom explaining interannual variations in surface salinity distributions within the region hence our results offer a viable mechanism besides the freshening of remote upstream sources to explain interannual patterns of freshening in the gom

the sea level budget along the northwest atlantic coast gia mass changes and large scale ocean dynamics sea level rise and decadal variability along the northwestern coast of the north atlantic ocean are studied in a self consistent framework that takes into account the effects of solid earth deformation and geoid changes due to large scale mass redistribution processes observations of sea and land level changes from tide gauges and gps are compared to the cumulative effect of gia present day mass redistribution and ocean dynamics over a 50 year period 1965 2014 gia explains the majority of the observed sea level and land motion trends as well as almost all interstation variability present day mass redistribution resulting from ice melt and land hydrology causes both land uplift and sea level rise in the region we find a strong correlation between decadal steric variability in the subpolar gyre and coastal sea level which is likely caused by variability in the labrador sea that is propagated southward the steric signal explains the majority of the observed decadal sea level variability and shows an upward trend and a significant acceleration which are also found along the coast the sum of all contributors explains the observed trends in both sea level rise and vertical land motion in the region as well as the decadal variability the sum of contributors also explains the observed acceleration within confidence intervals the sea level acceleration coincides with an accelerating density decrease at high latitudes

the dominant influence of the icelandic low on the position of the gulf stream northwall 1 the location where the gulf stream separates from the american coast and turns eastward is called its northwall the interannual fluctuations of the northwall are significantly correlated with the north atlantic oscillation with a lag of two years when the azores high and the icelandic low pressures are taken as independent variables the latter dominates the relationship with the northwall and the influence of the azores high pressure is insignificant this is consistent with the hypothesis that the major oceanic control of the northwall is in the southward flow of labrador sea water into the slope sea the alternative mechanism that the interaction of westward propagating rossby waves with the american coast is responsible for northwall fluctuations is considered less likely because its initiation requires perturbations of the eastward winds in the mid atlantic region and they are very likely dependent on the azores high the analysis suggests that the time lag between perturbations of the icelandic low and the northwall varies between one and three years

subtidal response of scotian shelf circulation to local and remote forcing part ii barotropic model abstract a linear barotropic numerical model that features realistic bathymetry of the scotian shelf provides solutions forced by steady and periodic wind stress that are generally incoherent on spatial scales of the shelf width closed circulation cells occur in association with and on the scales of major bathymetric features bathymetrically steered flow is prevalent and more evident at lower frequencies model transport forced by a coastally trapped wave propagating across the backward boundary is not sensitive to the model structure of the incident wave bathymetry rapidly modifies the wave form as it propagates in the free direction higher modes and reflected waves are probably dissipated over short distances by mattering and strong bottom stress patterns seen in the model solutions are consistent with results from more fundamental models and are readily explained by relatively simple vorticity balances model results generally reproduce the diverse local and nonlocal velocity responses observ

sr isotope data for the tertiary lavas of northern ireland evidence for open system petrogenesis the lavas of ne ireland represent the largest remnant of the british and irish tertiary igneous province in this paper we present new sr isotope data which by virtue of extreme variation provide evidence of extensive open system behaviour in the petrogenesis of these flood basalts to some extent the initial 87 sr 86 sr ratios 87 sr 86 sr 60ma 0 703 0 715 record the effects of late stage hydrothermal processes however leaching experiments allow primary magmatic signatures to be inferred with confidence coherent increases in initial 87 sr 86 sr ratio with differentiation indices and incompatible trace element ratios imply a role for crustal contamination very significant differences in the style of crustal interaction are recorded by discrete units within the basalt pile further there are also marked contrasts with tertiary basalts elsewhere in the united kingdom in both cases such variations appear to respond to changes in the basement geology reflecting the important control of crustal wall rocks on the geochemistry of these basalts

the cenomanian turonian boundary event ctbe in northern lebanon as compared to regional data another set of evidences supporting a short lived tectonic pulse coincidental with the event abstract constrained by both foraminifera and isotope data the zeitoun and nahr ibrahim sections in northern lebanon record a steady flooding of the cenomanian carbonate platform during the uppermost cenomanian lower turonian interval the flooding began just before the inception of the ctbe 13c positive shift it is marked by the deposition of finely bedded to laminated fine grained limestone overlying platformal carbonates this scenario is entirely different to what has been published in northern israel where repeated emergences are instead recorded during the event a survey of published data from nearby middle east countries to north africa suggests that the ctbe is accompanied on a larger scale especially along the syrian arc by tectonic disturbances responsible for sequence stratigraphic heterogeneity and palaeogeographic changes detailed analysis of available data makes it possible to extract from the sedimentary record four sequence stratigraphic scenarios implying two phases of heterogeneity bounding the event and responsible for the outphasing of relative sea level changes in some sensitive areas these disturb a stepped early cenomanian to early turonian overall transgressive trend recorded in some large stable areas often used to support the concept of mesozoic eustasy the discussion focuses on the global processes that are possibly involved the hypothesized tectonic pulse does not explain the ctbe it is just another set of data to be taken into account in the search for causes

paleobiogeography of late early cretaceous to early paleocene marine ostracoda in arabia and north to equatorial africa abstract about 1270 marine ostracod species of aptian to early paleocene age from central west north and east africa inclusive madagascar as well as the arabian peninsula and pakistan western india have been examined on their spatial and stratigraphical distribution their paleobiogeographical relations have been examined based on the jaccard index the results of these comparative studies are demonstrated on nine geographical maps for each stage aptian through early paleocene and four paleogeographical reconstructions including the assumed land sea distribution for cenomanian turonian maastrichtian and early paleocene times the major results are the recognition of an increasingly uniform pan south tethyan ostracod province north and northeast africa and the arabian peninsula from the aptian to the cenomanian due to the emergence of major parts of the arabian shield during the turonian this pan south tethyan bioprovince was split into a western protobuntonia numidica ostracod province north africa and western middle east and an eastern kaesleria ostracod province eastern arabia south iran somalia since the coniacian while the proliferation of the phylogenetic lines of the ostracod genera and species of the south tethyan ostracod province towards the protobuntonia numidica faunas into the turonian coniacian was continuous the newly developing genera and species of the protobuntonia numidica and the kaesleria provinces of the senonian early paleocene had almost nothing in common although most of northeast africa and the arabian shield underwent strong subsidence during the campanian maastrichtian combined with a widespread transgression these strictly separated bioprovinces did not reunite or show clear faunal interrelationships during these times the reasons for the described phenomena are probably largely to be sought in the paleoecological peculiarities of the regarded ostracod faunas i e a relatively cooler water fauna in the protobuntonia province probably partially influence by upwelling and a relatively warmer tropical fauna in the kaesleria province however the strict separation of these ostracod assemblages along a narrow n s directed borderline running from northeast saudi arabia across jordan into syria is thought to be highly unusual and to require further investigation which could probably stimulate new paleo oceanographical and paleogeographical considerations for the late cretaceous early paleocene of northeast africa the middle east and arabia

environmental constraints of foraminiferal assemblages distribution across a brackish tidal marsh caminha nw portugal abstract foraminiferal living assemblages from a brackish tidal marsh were studied across three sampling transects under spring and autumn conditions foraminiferal analysis was also extended to the dead assemblages of spring samples altimetric control of each sampling point was acquired through the connection to the national datum by gps differential positioning combined with a regional geoid model the influence of the geochemical characteristics on the assemblages including chemical composition of the estuarine and marsh surface sediments in addition to salinity ph and calcite saturation of estuarine and marsh interstitial waters was evaluated a high affinity was found between spring and autumn living assemblages probably related to the low number of representative species the affinity also found between living and dead assemblage was seen as a consequence of low ph and calcite undersaturation that prevent the accumulation effect of several generations of foraminifera salinity appears as a clear constraint to the foraminiferal assemblages composition that is enhanced by calcite undersaturation in brackish marshes interstitial waters and sediments generally abundant marsh species like trochammina inflata jadammina macrescens and the calcareous foraminifera are limited to an episodic presence foraminiferal assemblages distribution across brackish tidal marsh can be assumed as an elevation proxy the high marsh ib sub zone is dominated by haplophragmoides sp and haplophragmoides manilaensis low marsh zone ii is characterised by the dominance of miliammina fusca but can be subdivided in an iia upper part where is followed by pseudothurammina limnetis and in a iib lower part defined by a subsidiary presence of psammosphaera sp haplophragmoides manilaensis dominance between 1 55 m and 1 67 m at living as well as dead assemblages suggests this species as a potential sea level indicator for the brackish tidal marshes

the caledonian strike swing and associated lineaments in nw ireland and adjacent areas sedimentation deformation and igneous intrusion patterns part of the major swing in strike associated with the greenland labrador promontory of the north atlantic caledonides is exposed in considerable detail in the metasedimentary and meta igneous rocks of the neo proterozoic dalradian supergroup in northwest ireland we show that the strike swing controlled dalradian stratigraphy and sedimentation patterns and is therefore at least c 600 ma in age our interpretation of the stratigraphy allows a reconstruction of this promontory in the laurentian continental margin and shows that it separated a ne trending gently inclined and broad continental shelf in the north from an e trending more steeply inclined and narrower shelf to the south once established in the geometry of the dalradian sequence the strike swing and basement promontory had a major influence on caledonian deformation patterns it controlled the nucleation of major folds the geometry of the regionally developed primary cleavages the facing direction of the early folds and it also acted as a major buttress in perturbing and deflecting on a regional scale the orogenic transport vector accurate restoration of the sinistral displacement on a late caledonian fault system shows that the apices of the strike swing at different stratigraphic levels and their associated sedimentary facies changes define a line trending approximately n12oe this line is coincident with again after fault restoration six out of the eight devonian donegal granites the vast majority of the mantle related ultrabasic appinite suite with most of these bodies concentrated at the intersection of this line and the ne trending main donegal granite shear zone and the highest density of the neo proterozoic basic tholeiite suite thes e and other data are used to suggest that the donegal lineament is the expression of a major steeply inclined fault in the basement beneath the dalradian which is intimately related to the morphology of the promontory the fault which might be as old as 1800 ma probably reached down into the lithospheric mantle controlling igneous activity including the ascent emplacement site and perhaps sources of the magmas another complementary strike swing and parallel lineament is described from the dalradian rocks of the adjacent part of scotland it is suggested that these and other major lineaments i e old pre caledonian faults which have either nne ne or ese trends reflect not so much the location of the northern british isles at a 120o triple junction during iapetus rifting but rather the exploitation of these pre existing trends in the pre caledonian atlantic borderlands during iapetus opening

spatial and temporal structure of the barotropic response of the scotian shelf and gulf of maine to surface wind stress a model based study the barotropic current and pressure field responses of the scotian shelf and gulf of maine region to spatially uniform wind stress are examined using a three dimensional finite element numerical model the model is linear and harmonic with spatially varying eddy viscosity and bottom friction coefficients obtained from a nonlinear m2 tidal solution the solutions for low frequency 20 day period wind stress and upstream boundary forcing are generally consistent with previous depth averaged model results showing a substantially stronger response for along shelf compared to cross shelf stress and strong topographic shaping of the associated arrested topographic waves with their expanded domain and dimensionality the present solutions reveal important additional features of the responses such as the northeast channel being the primary conduit for cross shelf subsurface flow compensating the cross shelf ekman transport over the scotian shelf widespread areas of near bottom upwelling and downwelling along the coast and shelf break and leakage of the response across the shelf break model solutions for stress forcing with periods in the storm band 2 5 days show similar structures and elevation current gains to those in the low frequency solutions with the primary exception that the large northeast channel transport for along shelf stress excites a topographic wave over the continental slope south of georges bank the strength of bottom stress dependent on the magnitudes of both the bottom friction coefficient and near bottom viscosity in the model has a significant quantitative influence on the inner shelf response coastal elevation amplitudes and cross shelf decay scales in particular the implications of the model solutions for the interpretation of various observational features of the region s response to wind stress are discussed including coastal elevations offshore bottom pressures currents transports upwelling zones frequency dependences and seasonal and frictional influences

variability of the simulated meridional heat transport in the north atlantic for the period 1951 1993 a 43 year ocean model simulation for the period 1951 1993 is analyzed with a focus on the meridional heat transport mht as a proxy for the strength of meridional overturning cell moc at 25 n the surface heat flux forcing associated with the north atlantic oscillation nao pattern is related to the variability in mht both on interannual and longer timescales the manifestation of the interannual and decadal oceanic response to nao is nonlocal as evidenced by the concentrated heat content and sea level variability at the gulf stream and north atlantic current regions and shown by the comparison of the model sea level variability to the altimeter data between low mht years in mid 1980s and high mht years in early 1990s the same area is singled out by empirical orthogonal function analysis in the leading mode of the sea level mht and time series of the leading sea level mode are highly correlated which reflects the importance of the moc in determining the variability of the heat content of the whole basin also the model suggests that the mht moc has entered a very strong phase since the mid 1980s and this trend has continued up to the end of 1993 this behavior follows the general trend in the nao index

meltwater pathways from marine terminating glaciers of the greenland ice sheet the greenland ice sheet gris stores the largest amount of freshwater in the northern hemisphere and has been recently losing mass at an increasing rate an eddy permitting ocean general circulation model is forced with realistic estimates of freshwater flux from the gris two approaches are used to track the meltwater and its trajectory in the ocean we show that freshwater from western and eastern gris have markedly different fates on a decadal timescale freshwater from west greenland predominantly accumulates in baffin bay before being exported south down the labrador shelf meanwhile gris freshwater entering the interior of the labrador sea where deep convection occurs comes predominantly 80 from east greenland therefore hosing experiments which generally assume a uniform freshwater flux spatially will not capture the true hydrographic response and regional impacts in addition narrow boundary currents are important for freshwater transport and distribution requiring simulations with eddy resolving resolution

link between cyclic eustatic sea level change and continental weathering evidence for aquifer eustasy in the cretaceous abstract cyclic fluctuations in global sea level during epochs of warm greenhouse climate have remained enigmatic because absence or subordinate presence of polar ice during these periods precludes an explanation by glacio eustatic forcing an alternative concept suggests that the water bearing potential of groundwater aquifers is equal to that of ice caps and that changes in the dynamic balance of aquifer charge versus discharge as a function of the temperature related intensity of the hydrological cycle may have driven eustasy during warm climates however this idea has long been neglected for two reasons 1 the large storage potential of subsurface aquifers was confused with the much smaller capacity of rivers and lakes and 2 empirical data were missing that document past variations in the hydrological cycle in relation to eustasy in the present study we present the first empirical evidence for changes in precipitation continental weathering intensity and evaporation that correlate with astronomically long obliquity forced sea level cycles during the warmest period of the cretaceous cenomanian turonian we compare sequence stratigraphic data with changes in the terrigenous mineral assemblage in a low latitude marine sedimentary sequence from the equatorial humid belt at the south tethyan margin levant carbonate platform jordan thereby avoiding uncertainties from land ocean correlations our data indicate covariance between cycles in weathering and sea level predominantly chemical weathering under wet climate conditions is reflected by dominance of weathering products clays in deposits that represent sea level fall aquifer charge discharge conversely preservation of weathering sensitive minerals feldspars epidote and pyroxenes in transgressive sediments reflects decreased continental weathering due to dryer climate aquifer discharge charge based on our results we suggest that aquifer eustasy represents a viable alternative to glacio eustasy as a driver of cyclic 3rd order sea level fluctuations during the middle cretaceous greenhouse climate and it may have been a pervasive process throughout earth history

the antrim galway line a resolution of the highland border fault enigma of the caledonides of britain and ireland the westward continuation of the highland border fault of scotland hbfz into ireland is problematic it is widely thought to follow a pronounced magnetic and gravity lineament the fair head clew bay line fcl the advantage of this interpretation is that it places all the ordovician ophiolitic complexes and associated sedimentary basins to the south of the fcl which would represent the contact between laurentia and the outboard terranes its main shortcomings are that both the deep structure and timing of strike slip are different on the hbfz and fcl in ireland the fcl is a north dipping feature that can be traced to the moho on birps profiles while the hbfz has no such signature terrane amalgamation in western ireland was completed by the late ordovician while in scotland the midland valley terrane did not finally dock until the early devonian these considerations suggest that in western ireland a branch of the hbfz exists which was active in post ordovician time and must lie south of connemara an examination of irish geological geophysical and image processed magnetic data shows that a profound lineament can be traced from antrim to galway bay the antrim galway line stitching plutons date movement on it as pre 405 ma we propose that the antrim galway line represents the continuation of the scottish hbfz while the fcl is a preserved ordovician splay of the hbfz system whose northdipping geometry is a product of ordovician collapse of the orogen in western ireland

water sources for georges bank abstract the origins of georges bank source waters can be quantified by the oxygen isotope salinity tracer regionally water is tagged by freshwater of different h 2 18 o h 2 16 o ratios and these waters can subsequently be identified after mixing downstream this conservative lagrangian tracer of source waters is useful for tracking passive plankton and larvae that may be important to sustain the georges bank ecosystem the origin of georges bank freshwater sources is primarily in the gulf of st lawrence consisting of labrador shelf water which enters via the strait of belle isle and st lawrence river water these two mix with the underlying slope water in the gulf of st lawrence and along the scotian shelf at the northeast channel the input to the gulf of maine there is a single freshwater endmember consisting of 5 6 st lawrence river water and 94 6 labrador shelf water by volume these proportions remained constant for the years 1995 1997 the water on central georges bank consists of a mixture of water entering the northeast channel with gulf of maine river outflow there is considerable interannual variation in the maine river water proportion ranging from 3 3 in 1982 to 0 23 by volume in 1996 during 1995 1998 there was no correlation between georges bank salinity which decreased monotonically and the proportion of maine river water on the bank the interannual fluctuations of salinity on georges bank are driven by variations in upstream scotian shelf sources and its mixing onto the bank and not by changes in local river outflow

freshening of the labrador sea surface waters in the 1990s another great salinity anomaly 1 the observed labrador sea surface salinities for 1951 2001 in region 55w 40w 45n 55n show freshening in the 1990s which may rival the great salinity anomaly gsa of the 1970s dickson et al 1988 the 1990s freshening is distinct in the lowest range of salinity values associated with the coastal waters the variability of the highest salinity values provided by the north atlantic current entering the labrador sea shows that the high salinity atlantic waters were not widely present in the 1970 s and 1990s this can be interpreted as weakened transport of saline waters to the area this explanation is consistent with an arctic north atlantic model results forced by ncep ncar reanalysis data for 1958 2001 which suggest that these periods are associated with a reduced meridional overturning the model also associates the coastal freshening with southward current anomalies which are well correlated with the number of icebergs crossing 48n

seasonal circulation on the western and central scotian shelf abstract a realistic representation of 3d seasonal circulation and hydrography on the western and central scotian shelf has been obtained from historical observations and a combination of diagnostic and prognostic numerical models with forcing by tides wind stress and baroclinic and barotropic pressure gradients the major current features the southwestward nova scotian and shelf edge currents and partial gyres around browns and sable island banks are found to persist year round but with significant seasonal changes comparison with current meter observations shows good agreement for the browns bank southwest nova scotia and inner shelf regions and poorer agreement in the sable island bank and shelf edge regions where current and density observations are sparser and tidal influences weaker there is significant spatial structure in the seasonal circulation and hydrography and in the underlying dynamical processes on the shelf scale there are substantial changes in stratification potential energy

on the relationship between the meridional overturning circulation alongshore wind stress and united states east coast sea level in the community earth system model large ensemble

annual sea level changes on the north american northeast coast influence of local winds and barotropic motions abstractunderstanding the relationship between coastal sea level and the variable ocean circulation is crucial for interpreting tide gauge records and projecting sea level rise in this study annual sea level records adjusted for the inverted barometer effect from tide gauges along the north american northeast coast over 1980 2010 are compared to a set of data assimilating ocean reanalysis products as well as a global barotropic model solution forced with wind stress and barometric pressure correspondence between models and data depends strongly on model and location at sites north of cape hatteras the barotropic model shows as much if not more skill than ocean reanalyses explaining about 50 of the variance in the adjusted annual tide gauge sea level records additional numerical experiments show that annual sea level changes along this coast from the barotropic model are driven by local wind stress over the continental shelf and slope this result is interpreted in the light of a simple dynamic

the cenomanian turonian oceanic anoxic event ii palaeoceanographic controls on organic matter production and preservation correlation of the 13c spike with the well dated occurrences of strata rich in organic carbon detailed in schlanger et al this volume indicates that a global episode of intense organic carbon orgc burial took place during the latest cenomanian earliest turonian oceanic anoxic event oae a plenus through i labiatus macrofossil zones and upper r cushmani trz through w archecretacea prz foraminiferal zones over a period of no more than 1 million years m y the shape of the 13c curve indicates that rates of orgc burial gradually increased in the early part of the late cenomanian increased more rapidly in the later cenomanian and levelled off at peak values in latest cenomanian early turonian time during the maximum rate of orgc burial the 13c values decreased nearly to pre late cenomanian levels in the early to middle turonian the decrease in 13c reflects decreasing rates of orgc burial following the cenomanian turonian oceanic anoxic event as well as the probable oxidation and return of significant amounts of orgc to the oceans following regression and re oxygenation of much of the deeper water masses in contact with the seafloor

rapid freshening of the deep north atlantic ocean over the past four decades the overflow and descent of cold dense water from the sills of the denmark strait and the faroe shetland channel into the north atlantic ocean is the principal means of ventilating the deep oceans and is therefore a key element of the global thermohaline circulation most computer simulations of the ocean system in a climate with increasing atmospheric greenhouse gas concentrations predict a weakening thermohaline circulation in the north atlantic as the subpolar seas become fresher and warmer1 2 3 and it is assumed that this signal will be transferred to the deep ocean by the two overflows from observations it has not been possible to detect whether the ocean s overturning circulation is changing but recent evidence suggests that the transport over the sills may be slackening4 here we show through the analysis of long hydrographic records that the system of overflow and entrainment that ventilates the deep atlantic has steadily changed over the past four decades we find that these changes have already led to sustained and widespread freshening of the deep ocean

decadal variability of hydrography in the upper northern north atlantic in 1948 1990 we investigate the variability of the north atlantic subarctic gyre in recent decades from time series of station temperature and salinity decadal variability stronger at the surface is identified which exhibits vertical coherence over a layer deeper than the late winter mixed layer in the northwestern atlantic it corresponds to the layer with a component of water from the arctic ocean or from the canadian arctic the spatial coherence of the signal is investigated an empirical orthogonal function decomposition of lagged time series indicates that a single pattern explains 70 of the variance in upper ocean salt content corresponding to a propagating signal from the west to the northeast in the subarctic gyre the most likely interpretation is that the salinity signal originates in the slope currents of the labrador sea and is diffused advected eastward of the grand banks over the near western atlantic in the northwestern atlantic temperature fluctuations are strongly correlated to salinity fluctuations and are aligned along the average t s characteristics this signal suggests large variations in the outflow of fresh cold water in the slope current and is strongly correlated with ice cover a basin scale atmospheric circulation of weakened westerlies at 55 n weaker northwesterlies west of greenland and weaker southerlies over the central and eastern north atlantic is associated with the high salinity and warm water phase of the first principal component this circulation pattern leads fluctuations in the northeast atlantic and lags those in the northwestern part of the basin the wind indices also suggest that the fluctuations of the fresh water outflow occur during intervals of anomalously northerly winds either east of greenland 1965 1968 1969 or off the canadian archipelago 1983 1984

great salinity anomalies in the north atlantic abstract we revisited the great salinity anomaly of the 1970s gsa 70s dickson et al 1988 and documented the newly identified great salinity anomaly of the 1980s hence termed gsa 80s both propagated around the north atlantic in a similar fashion the advective mechanism initially proposed to explain the observed sequence of low salinity low temperature events during the gsa 70s apparently holds also for the gsa 80s the latter was successively observed in the west greenland current 1982 the labrador current 1983 the flemish pass 1984 near the charlie gibbs fracture zone 1984 1985 in the rockall channel 1985 south of iceland 1985 1988 in the north sea 1986 1987 norwegian sea 1987 1988 barents sea 1988 1989 and iceland sea 1989 1990 the advection speed of the gsa 80s seems to be greater than the one of the gsa 70s the 1980s anomaly reached the barents sea 6 to 7 years after peaking in the west greenland current while the 1970s anomaly traveled the same route in 8 to 10 years these anomalies however seem to be of different origin the gsa 70s was apparently boosted remotely by a freshwater sea ice pulse from the arctic via fram strait consequently the gsa 70s was accompanied by a large sea ice extent anomaly in the greenland and iceland seas which propagated into the labrador sea in contrast the gsa 80s was likely formed locally in the labrador sea baffin bay mainly because of the extremely severe winters of the early 1980s but supplemented with a possible contribution of the arctic freshwater outflow via the canadian archipelago facilitated by strong northerly winds which would have enhanced stability and ice formation this anomaly was also associated with a positive sea ice extent anomaly in the labrador sea baffin bay which however had no upstream precursor in the greenland sea thus the gsas are not necessarily caused solely by an increased export of freshwater and sea ice from the arctic via fram strait these results are corroborated by the early 1990s data when a new fresh cold anomaly was formed in the labrador sea and accompanied by a large positive sea ice extent anomaly the harsh winters of the early 1990s were however confined to the labrador sea baffin bay area while the atmospheric and oceanic conditions in the greenland iceland and irminger seas were normal the labrador sea baffin bay area appears therefore to play a key role in formation of gsas as well as in propagation of the gsas formed upstream a likely contribution of the enhanced canadian archipelago freshwater outflow to the gsa formation also seems to be significant two major modes of the gsa origin are thus identified remote generated by an enhanced arctic ocean freshwater export via either fram strait or the canadian archipelago and local resulting from severe winters in the labrador sea baffin bay both modes should be taken into account to model decadal variability of the coupled ocean ice atmosphere system in the north atlantic arctic basin

on the longshelf structure and dynamics of subtidal currents on the eastern united states continental shelf abstract strong correlations were observed among subtidal longshelf currents from the middle atlantic bight mab to the georges bank region a distance spanning 615 km the longshelf current consisted predominantly of wind forced motions and freely propagating events which together accounted for 75 90 of the longshelf current energy much stronger longshelf currents were observed in the mab than on georges bank the mab georges bank energy ratio for wind forced currents on the 60 m isobath was 20 the ratio for freely propagating events was 3 the magnitudes of many of the terms in the vertically integrated wind driven momentum equations were estimated from observations of current pressure and surface stress and from calculations of bottom stress the cross shelf momentum balance was geostrophic surface and bottom stress the longshelf pressure gradient and the coriolis force on the cross shelf flow were important terms in the longshelf momentum balance an analytic model of wind forced current w

transgressions regressions and relative sea level changes on the cretaceous shelf of israel and adjacent countries a critical evaluation of cretaceous global sea level correlations cretaceous transgressive regressive cycles over the northern margins of the arabo nubian craton in the region of present day israel and the adjacent countries were reconstructed by tracing the position of the ancient tethyan shorelines many of these cycles suggest inverse relationships to the relative sea level changes deduced from litho and biofacies analyses transgressions are frequently associated with shallowing resulting in local exposure the following rapid relative sea level rise is associated with regressive oscillations caused by prograding sedimentation generally the relative sea level gradually rose throughout the cretaceous as reflected by the onlapping trend of the marine sediments with the exception of one greater relative sea level drop in the middle turonian probably tectonically induced all other relative sea level variations were short stillstands and very minor falls the dominant tectonic control on the relative sea level changes and transgressive regressive cycles during the late coniacian maastrichtian times and on the middle turonian and early late coniacian shallowing events recognised in israel render their previous attribution exclusively to eustasy erroneous the opposing relationship between relative bathymetric changes and transgressive regressive tendencies as well as the poor biostratigraphic control in many of the sea level curves compiled on the basis of these two criteria raise additional doubts as to their presumed significance for global correlations the present study supports jeletzky s 1977 1978 critical analysis and his call for similar critical re evaluation of previous studies throughout the world rather than the emendation of data to improve correlation to a given scheme

long term coordinated changes in the convective activity of the north atlantic the north atlantic is a peculiarly convective ocean the convective renewal of intermediate and deep waters in the labrador sea and greenland iceland sea both contribute significantly to the production and export of north atlantic deep water thus helping to drive the global thermohaline circulation while the formation and spreading of 18 degree water at shallow to intermediate depths off the us eastern seaboard is a major element in the circulation and hydrographic character of the west atlantic for as long as time series of adequate precision have been available to us it has been apparent that the intensity of convection at each of these sites and the hydrographic character of their products have been subject to major interannual change as shown by aagaard 1968 clarke et al 1990 and meincke et al 1992 for the greenland sea in the ows bravo record from the labrador sea eg lazier 1980 et seq and at the panulirus hydrostation s site in the northern sargasso off bermuda eg jenkins 1982 talley and raymer 1982 this paper reviews the recent history of these changes showing that the major convective centres of the greenland and labrador seas are currently at opposite convective extrema in our postwar record with vertical exchange at the former site limited to 1000 m or so but with labrador sea convection reaching deeper than previously observed to over 2300 m as a result greenland sea deep water has become progressively warmer and more saline since the early 70 s due to increased horizontal exchange with the arctic ocean through fram strait while the labrador sea water has become progressively colder and fresher over the same period through increased vertical exchange most recently convection has become deep enough there to reach into the more saline nadw which underlies it so that cooler but now saltier and denser lsw has resulted

the great salinity anomaly in the northern north atlantic 1968 1982 the widespread freshening of the upper 500 800m layer of the northern north atlantic which this paper describes represents one of the most persistent and extreme variations in global ocean climate yet observed in this century though a range of explanations have been advanced to explain this event including in situ changes in the surface moisture flux this paper describes the great salinity anomaly as largely though not entirely an advective event traceable around the atlantic subpolar gyre for over 14 years from its origins north of iceland in the mid to late 1960s until its return to the greenland sea in 1981 1982 the overall propagation speed around this subpolar gyre is estimated at about 3cm s 1 of the total salt deficit associated with the anomaly as it passed south along the labrador coast in 1971 1973 about 72 109 tonnes a deficit equivalent to about two thirds of this figure 47 109 tonnes ultimately passed through the faroe shetland channel to the barents sea arctic ocean and greenland sea during the mid 1970s possible effects on deep water formation and on the representativeness of historical section data are discussed

c isotope stratigraphy and paleoenvironmental changes across oae2 mid cretaceous from shallow water platform carbonates of southern mexico the stratigraphic and geochemical record of the mid cretaceous cenomanian turonian oceanic anoxic event 2 oae2 has been studied in numerous tethyan and proto atlantic hemi pelagic pelagic successions but little data comes from nearshore carbonate successions from the proto pacific region here we present the results of a combined stratigraphic and 13c study of c t platform carbonates from southern mexico which were deposited within the proto pacific two scales of sedimentary cyclicity are recognized high frequency peritidal and subtidal cycles 0 4 8 m display little evidence of cycle capping subaerial exposure and are not correlative between sections these relationships suggest that the amplitudes of high frequency sea level changes were minimal during the peak mid cretaceous greenhouse longer term transgressive regressive sequences 18 40 m are correlated between sections and using 13c trends can be correlated with sequences developed in northern europe and india the mexican successions were sampled at a high resolution 10 ky for stable isotopes inorganic organic carbon and oxygen total organic carbon insoluble residues and trace metals the 13ccarb curve matches global trends including 6 distinct isotopic stages permitting identification of oae2 despite the lack of characteristic anoxic facies using the 13ccarb trends we tie the previously identified ammonite planktonic foram and nannofossil biostratigraphy from england and the western interior seaway of colorado into the mexican sections the initiation of oae2 defined by an abrupt positive 3 4 13c shift coincides with a long term sea level rise though the sedimentary expression of the deepening is no greater than that observed for any of the other sea level events across the studied interval oae2 termination transition from gradually decreasing to background 13c values is not associated with a particular sea level trend stratigraphic changes in insoluble residues proxy for continental sediment discharge across oae2 are not correlative between sections and do not show consistent systematic relationships with 13c or sea level variations therefore do not support the hypothesis that oae2 was associated with increased continental derived nutrient influx two peaks in trace metal concentrations coincide with the abrupt increase in 13c ratios onset of oae2 and during the transition from elevated to decreasing 13c values near the c t stage boundary these trends are similar to those recorded in coeval deposits of the western interior seaway and are consistent with the hypothesis that oae2 development was related to the release of reduced metals during the short lived 1 my caribbean oceanic plateau basalt eruption in this scenario oxidation of the metals depleted the existing low dissolved o2 concentrations and thermally buoyant plumes of seawater enriched in biolimiting elements mixed with surface waters stimulated primary productivity and further reduced o2 concentrations leading to widespread anoxia and a large positive 13c shift

isotope signatures associated with early meteoric diagenesis the environments in which carbonate diagenesis proceeds have been documented in previous studies of holocene and late pleistocene sediments and limestones on barbados west indies variations in the carbon and oxygen isotopic composition of limestones produced during early freshwater diagenesis have been observed in this study to occur in specific patterns six potentially useful patterns emerge when one views stable isotope data within a stratigraphic framework 1 the subaerial exposure surface is characterized by strongly 12c enriched limestones 13c compositions of underlying limestones grow progressively heavier with increasing depth 2 the subaerial exposure surface may also be marked by slight 18o enrichment 3 an abrupt shift in 18o values may differentiate sediments above the exposure surface from those below 4 sediments altered in the marine meteoric mixing zone may be characterized by positive covariance between their 18o and 13c compositions 5 the vadose phreatic boundary may be marked by a sharp increase in 13c values in the seaward portions of a fresh groundwater system and 6 samples contemporaneously altered in a single fresh groundwater system within an areally restricted region should display a narrow range of 18o and a wide range of 13c compositions analysis of samples from five palaeozoic and mesozoic formations which contained petrographic evidence of early freshwater diagenesis showed that isotope patterns similar to those observed in barbados limestones have been preserved in rocks as old as mississippian these isotope patterns could prove to be useful for identifying diagenetically induced porosity trends in carbonate rocks they might be used to identify limestones diagenetically altered in meteoric environments to identify mixing zone cements and dolomites and to trace the regional and vertical distributions of early meteoric groundwater systems in ancient carbonate formations

molecular isotopic evidence of environmental and ecological changes across the cenomanian turonian boundary in the levant platform of central jordan abstract we evaluated the structure of planktonic communities and paleoenvironmental conditions throughout the cenomanian turonian oceanic anoxic event oae2 by studying bulk geochemical properties and the molecular isotopic composition of source specific hydrocarbons from organic rich sediments deposited in an intrashelf basin at the levant platform central jordan high concentrations of desmethyl and 4 methylsteranes as well as dinosteranes indicate that marine algae including dinoflagellates were the main primary producing organisms the presence of 2 methylhopanes and 13 c enriched hopanes in addition to isotopically enriched aryl isoprenoids evidenced the contribution of cyanobacteria and green sulfur bacteria respectively additionally variable but fairly low 15 n values during oae2 suggest the occurrence of diazotrophy as a likely important process fueling primary production during oae2 in this stratified anoxic continental platform variations in the relative contribution of biomarkers revealed changes in planktonic communities associated with sea level change and water column stratification oae2 was characterized by strong stratification anoxic bottom waters and a deep chemocline as evidenced by high gammacerane and homohopane indices and the absence of photic zone euxinia pze markers respectively however the presence of isorenieratane and its derivatives in post oae black shales points to a shoaling of the chemocline and to pze this interval was also characterized by an exceptionally high abundance of chlorophyll derived pristane and phytane up to 2 mg g 1 toc likely as a result of highly enhanced primary production and organic matter preservation remarkably this high productivity event co occurs with an exceptionally high abundance of calcispheres reported elsewhere to be part of a global bio event

the cenomanian turonian oceanic anoxic event i stratigraphy and distribution of organic carbon rich beds and the marine δ13c excursion marine strata deposited during late cenomanian and early turonian time display lithological faunal and geochemical characteristics which indicate that significant parts of the world ocean were periodically oxygen deficient at or very close to the cenomanian turonian boundary between 90 5 and 91 5ma ago oxygen deficiencies were particularly marked over a period of 1ma this short lived episode of oceanic oxygen deficiency has been termed the cenomanian turonian oceanic anoxic event oae the widespread distribution of anoxic sediments deposited synchronously during such a short lived event indicates that such sediments are not simply the product of coincidental local climatic or basinal water mass characteristics but are the result of a global expansion and intensification of the cenomanian turonian oxygen minimum zone related to feedback between sea level rise and regional palaeoceanography the palaeoceanography of the cenomanian turonian oae is discussed in detail in a companion paper by arthur et al 1987 from authors

lithospheric structure north of scothland i p wave modelling deep reflection profiles and gravity the w reflector and the flannan reflector are two enigmatic planar structures in the lithospheric mantle north of scotland mapped in three dimensions using deep reflection profiling the flannan reflector dips eastwards from the moho to a depth of 80 km at an angle of 30 whilst the w reflector is subhorizontal lying 10 20 km beneath the moho and terminating westwards against the flannan both reflectors have a strong impedance contrast and are laterally coherent over tens of kilometres wide angle seismic reflection and refraction data are used here to constrain the p wave velocity structure of the lithosphere in this region and to investigate the physical properties and geometry of these reflective structures we report the results from an integrated seismic survey in which a series of explosive shots fired at sea were recorded by ocean bottom seismographs land stations and a streamer towed by a second ship in an expanding spread configuration a well resolved p wave velocity structure for the lithosphere above the mantle reflectors is derived by inverting the seismic traveltimes to optimize the fit of the model to the data and by generating synthetic seismograms from the model to match the relative amplitudes of the observed seismic phases a high amplitude post critical reflection indicates the existence of a discrete reflecting interface dipping gently westwards between 40 and 50 km depth in the lithospheric mantle the p wave velocity model is converted to two way reflection time and correlated with normal incidence reflection data the moho structure agrees well and the reflecting interface defined by the wide angle data is coincident with the subhorizontal w reflector less distinct later arrivals observed in the data are consistent with modelled reflections from the flannan reflector in the mantle and from the extrapolated position of the outer isles fault in the lower crust modelling of the relative amplitudes and critical distances of the wide angle mantle reflection shows that the reflecting layer must be at least 3 km thick and that it has considerably higher velocity 8 5 km s 1 and density 3 5 g cm 3 than normal mantle further modelling tests the vertical structure within the layer and constrains the sharpness of the upper interface and whether the reflection amplitude could have been enhanced by internal layering gravity data measured over the region are consistent with the velocity model and with the high density layer in the mantle which is constrained by the gravity modelling to be less than 10 km thick published laboratory measurements of the physical properties of mantle rocks indicate that mafic eclogite with high velocity and density satisfies all the observations from the mantle layer our preferred hypothesis for the origin for such a layer is that it is a fragment of oceanic crust that has been subducted and metamorphosed to eclogite facies

cenomanian turonian carbonate platform deposits in west central jordan we studied upper albian to turonian shallow marine shelf deposits ajlun group of west central jordan along a nne ssw running transect the carbonate dominated succession includes few siliciclastic intercalations claystones and shales and can be subdivided into five formations the naur fuheis and hummar formations of upper albian to upper cenomanian age represent shallow subtidal to supratidal platform environments the uppermost cenomanian to middle turonian shueib formation includes deeper water deposits of the inner mid shelf and locally toc rich black shales shallow marine platform environments once again dominate the wadi as sir formation middle upper turonian a new multibiostratigraphic framework is based on ammonites mainly of the middle cenomanian rhotomagense zone to the middle turonian woollgari zone and calcareous nannofossils biozones cc 9 cc 11 supplemented by benthic and planktonic foraminifers and ostracods it forms the base of a sequence stratigraphic subdivision containing eight sedimentary sequences s1 s8 which are separated by four cenomanian sequence boundaries cejo1 cejo4 and three turonian sequence boundaries tujo1 tujo3 this scheme allows the correlation of the platform succession from distal to proximal shelf areas in contrast to previous correlations using lithologic units furthermore comparisons between the platform successions and sequence patterns of west central jordan and those from neighbouring areas allow to differentiate local regional and global controlling factors of platform development within the study area

temperature and salinity variability on the scotian shelf and in the gulf of maine 1945 1990 examination of temperature and salinity data from the scotian shelf gulf of maine gulf of st lawrence and the adjacent continental slope has shown that the dominant low frequency event over the last 45 years was a cooling and subsurface freshening of the water masses from 1952 to 1967 followed by a rapid reversal of these trends the largest temperature and salinity changes 1952 1967 were 4 6 c and 0 7 respectively and occurred at about 100 m over the slope exchanges with shelf waters and vertical mixing gave rise to the surface manifestation of this variability the westward transport of the labrador current was found to have similar variability increasing from about 1 106 m3 s 1 in the early 1950s to about 4 106 m3 s 1 in the mid 1960s a simple model that accounts for this variation of transport and has a constant entrainment of north atlantic water indicates that changes of the westward flow of the labrador current could contribute significantly to the t s fluctuations

the mean and seasonal circulation off southwest nova scotia abstract long term measurements off southwest nova scotia reveal the following features of the mean circulation a a westward longshore coastal current 4 10 cm s 1 b an anticyclonic gyre around brown bank 5 15 cm s 1 and c an upwelling circulation off cape sable 1 2 cm s 1 at bottom the gyre circulation appears permanent but the coastal current and upwelling exhibit annual variations of the same order as the means there is a distinct annual signal in the longshore transport at cape sable maximum westward in winter whereas the mean transport 0 14 106 m4 s 1 is consistent with both geostrophic estimates and budget requirements in the gulf of marine strong seasonal cycles are also found in the salinity and density fields at cape sable which appear to be controlled both by buoyancy input from the coastal current and local mixing effects a linear diagnostic model indicates that the primary dynamical balance for the circulation is between a longshore pressure gradient and longshore mean

secular variation in late cretaceous carbon isotopes a new δ13c carbonate reference curve for the cenomanian campanian 99 6 70 6 ma carbon stable isotope variation through the cenomanian santonian stages is characterized using data for 1769 bulk pelagic carbonate samples collected from seven chalk successions in england the sections show consistent stratigraphic trends and 13c values that provide a basis for highresolution correlation positive and negative 13cexcursions and inflection points on the isotope profiles are used to define 72 isotope events key markers are provided by positive 13c excursions of up to 2 the albian cenomanianboundary event mid cenomanian event i thecenomanian turonian boundary event the bridgewick hitch wood and navigation events of late turonian age and the santonian campanian boundary event isotope events are isochronous within a framework provided by macrofossil datum levels and bentonite horizons an age calibrated composite 13c reference curve and an isotope event stratigraphy are constructed using data from the english chalk the isotope stratigraphy is applied to successions in germany france spain and italy correlation with pelagic sections at gubbio central italy demonstrates general agreement between biostratigraphic and chemostratigraphic criteria in the cenomanian turonian stages confirming established relationships between tethyan planktonic foraminiferal and boreal macrofossil biozonations correlation of the coniacian santonian stages is less clear cut magnetostratigraphic evidence for placing the base of chron 33r near the base of the upper santonian is in good agreement with the carbon isotope correlation but generates significant anomalies regarding the placement of the santonian and campanian stage boundaries with respect to tethyan planktonic foraminiferal and nannofossil zones isotope stratigraphy offers a more reliable criterion for detailed correlation of cenomanian santonian strata than biostratigraphy with the addition of campanian 13c data from one of the english sections a composite cenomanian campanian age calibrated reference curve is presented that can be utilized in future chemostratigraphic studies the cenomanian campanian carbon isotope curve is remarkably similar in shape to supposedly eustatic sea level curves increasing 13c values accompanying sea level rise associated with transgression and falling 13c values characterizing sea level fall and regression the correlation between carbon isotopes and sea level is explained by variations in epicontinental sea area affecting organic matter burial fluxes increasing shallow sea floor area and increased accommodation space accompanying sea level rise allowedmore efficient burial ofmarine organic matter with the preferential removal of 12c from the marine carbon reservoir during sea level fall reduced seafloor area marine erosion of previously deposited sediments and exposure of basin margins led to reduced organiccarbon burial fluxes and oxidation of previously deposited organic matter causing falling 13c values additionally drowning of carbonate platforms during periods of rapid sea level rise may have reduced the global inorganic relative to the organic carbon flux further enhancing 13c values while renewed platform growth during late transgressions and highstands prompted increased carbonate deposition variations in nutrient supply changing rates of oceanic turnover and the sequestration or liberation of methane from gas hydrates may also have played a role in controlling carbon isotope ratios

linkage between mantle and crustal structures and its bearing on inherited structures in northwestern scotland deep seismic reflection profiles in scotland reveal mantle structures beneath a crust with a polyphase tectonic history that resulted in several generations of structures continuum mechanics suggests that coeval mantle and crustal structures must be kinematically linked inherited structures imply relative ages for the reflectors ages that can be placed into the context of the geological history of the near surface rocks of northern scotland thus some mantle reflectors are assigned triassic ages related to the opening of the west orkney and related marginal basins of the atlantic ocean other mantle reflectors are cut by late caledonian structures associated with the great glen fault zone and therefore older than c 400 ma many of these structures also track the late precambrian margin of laurentia and may be related to either the opening 900 600 ma or closing 500 600 ma of the iapetus ocean some reflective structures may also be attributed to 1800 1700 ma laxfordian deformation that was part of a global scale orogenic belt

sequence architecture and carbonate platform configuration late cenomanian santonian sinai egypt relative sea level changes on the mixed carbonate siliciclastic platform of sinai are manifested in shifts of distinct facies belts deep water facies highenergy subtidal shallow subtidal lagoon shallow shoreface siliciclastics supratidal and are interpreted in terms of sequence stratigraphy eight sedimentary sequences are recognized for the upper cenomanian to santonian their correlation along a north south transect reveals distinct changes in lithofacies and progradation retrogradation patterns within the individual systems tracts the number and stratigraphy of the sequence boundaries of sinai correlate well with those from adjacent areas patterns of increased subsidence are documented for the central sinai basin since the late cenomanian by increased thickness of the stratal packages post cesin 7 hst post tusin 1 lst and hst post tusin 2 lst and are balanced by varying accumulation rates based on new sedimentological and biostratigraphic data large scale palaeogeographic maps and cross sections show the 1 temporal and spatial evolution of the central sinai basin e g its latest cenomanian initial formation lower turonian deep water facies middle turonian to coniacian synsedimentary subsidence 2 drowning of the cenomanian platform coinciding with the latest cenomanian to early turonian relative sea level rise 3 re establishment of the platform in middle late turonian times and 4 a coniacian basin and swell morphology

orbital time scale and new c isotope record for cenomanian turonian boundary stratotype previous time scales for the cenomanian turonian boundary ctb interval containing oceanic anoxic event ii oae ii vary by a factor of three in this paper we present a new orbital time scale for the ctb stratotype established independently of radiometric biostratigraphic or geochemical data sets update revisions of ctb biostratigraphic zonation and provide a new detailed carbon isotopic record for the ctb study interval the orbital time scale allows an independent assessment of basal biozone ages relative to the new ctb date of 93 55 ma gts04 the d 13 corg data document the abrupt onset of oae ii significant variability in d 13 corg values and values enriched to almost 222 these new data underscore the difficulty in defining oae ii termination using the new isotope curve and time scale estimates of oae ii duration can be determined and exported to other sites based on integration of well established chemostratigraphic and biostratigraphic datums the new data will allow more accurate calculations of biogeochemical and paleobiologic rates across the ctb

biostratigraphy palaeoecology and palaeogeography of the middle cenomanian early turonian levant platform in central jordan based on ostracods

rhinns complex a missing link in the proterozoic basement of the north atlantic region paleoproterozoic basement occurs on the islands of islay and colonsay in western scotland and on inishtrahull off the north coast of ireland the basement is composed of a deformed alkalic igneous association collectively referred to as the rhinns complex isotopic data indicate that the complex represents new addition of mantle derived material to the crust at ca 1 8 ga the rhinns complex may link with rocks of similar age in north america greenland and scandinavia which formed part of the southern margin of the laurentia baltica supercontinent