the salinity temperature and δ18o of the glacial deep ocean we use pore fluid measurements of the chloride concentration and the oxygen isotopic composition from ocean drilling program cores to reconstruct salinity and temperature of the deep ocean during the last glacial maximum lgm our data show that the temperatures of the deep pacific southern and atlantic oceans during the lgm were relatively homogeneous and within error of the freezing point of seawater at the ocean s surface our chloride data show that the glacial stratification was dominated by salinity variations in contrast with the modern ocean for which temperature plays a primary role during the lgm the southern ocean contained the saltiest water in the deep ocean this reversal of the modern salinity contrast between the north and south atlantic implies that the freshwater budget at the poles must have been quite different a strict conversion of mean salinity at the lgm to equivalent sea level change yields a value in excess of 140 meters however the storage of fresh water in ice shelves and or groundwater reserves implies that glacial salinity is a poor predictor of mean sea level

the post variscan thermal and denudational history of ireland the thermal and denudational history of ireland is evaluated using an extensive new apatite fission track aft dataset derived from surface samples modelled thermal histories are used to construct maps of denudation for a number of time slices from triassic time to 10 ma using a time dependent palaeogeotherm the maps illustrate the spatial variability of denudation and subsidence within each time slice the patterns of denudation are complex showing considerable variability at the length scale of 101 102 km with especially high denudation rates found over known igneous centres such as the mournes of county down based on the onshore aft data alone there is no definitive signature of an irish sea dome extending significantly across ireland in early tertiary time the cumulative amount of denudation during tertiary time varies depending on the aft annealing model used but is generally in the region between 1 and 2 km and without clear spatial trends high amounts of denudation have been mapped over the tertiary intrusions in county down reflecting their unroofing since emplacement in paleocene time the cumulative denudation from triassic time to 10 ma shows relatively low amounts of denudation 2 km in the irish midlands and the extreme ne of the island consistent with the observation that mesozoic tertiary sediments and igneous products are preserved in the ulster basin the western flank of ireland and the region between dublin and county down show high cumulative amounts of denudation 4 km the latter being consistent with the high amounts of denudation interpreted for the irish sea region this denudation pattern explains in part the outcrop of precambrian and lower palaeozoic rocks in these areas the spatial integration of the denudation over the entire landmass gives the average denudation rate and the sediment discharge from ireland as a function of time average denudation rates are moderately high in triassic time falling to low values in cretaceous time and increasing substantially in tertiary time however the total volumetric discharge of sediment in tertiary time is an order of magnitude smaller than the preserved solid volume of tertiary sediment in the basins offshore western ireland

reduced north atlantic deep water flux to the glacial southern ocean inferred from neodymium isotope ratios the global circulation of the oceans and the atmosphere transports heat around the earth broecker and denton1 suggested that changes in the global ocean circulation might have triggered or enhanced the glacial interglacial cycles but proxy data for past circulation taken from sediment cores in the south atlantic ocean have yielded conflicting interpretations of ocean circulation in glacial times 13c variations in benthic foraminifera2 3 4 5 6 support the idea of a glacial weakening or shutdown of north atlantic deep water production whereas other proxies such as cd ca ba ca and 231pa 230th ratios show little change from the last glacial maximum to the holocene epoch7 8 9 here we report neodymium isotope ratios from the dispersed fe mn oxide component of two southeast atlantic sediment cores both cores show variations that tend towards north atlantic signatures during the warm marine isotope stages 1 and 3 whereas for the full glacial stages 2 and 4 they are closer to pacific ocean signatures we conclude that the export of north atlantic deep water to the southern ocean has resembled present day conditions during the warm climate intervals but was reduced during the cold stages an increase in biological productivity may explain the various proxy data during the times of reduced north atlantic deep water export

the erris ridge a major geological feature in the nw irish offshore basins the erris ridge is a narrow structural high that separates the erris and rockall troughs it has a composite internal character and its orientation is thought to be controlled by a pre caledonian structural fabric which was frequently reactivated during caledonian to cenozoic time in the north it is fault bounded and probably contains rocks of palaeozoic and older age it formed a positive topographic feature which was progressively onlapped during permo triassic to cretaceous times fault reactivation occurred along its western boundary in tertiary times and it was submerged by approximately latest miocene times further south the ridge is more complex the palaeozoic and older core is flanked to the se by interpreted permo triassic to lower jurassic strata which constitute a fault controlled uplifted remnant of a half graben basin this composite structure was probably inverted during late jurassic times and remained as a topographic feature until cretaceous times it was progressively onlapped during cretaceous and tertiary times with a minor phase of fault reactivation during the early tertiary the ridge acted as a rigid block which facilitated the focusing of several phases of crustal extension in the erris trough and in the rockall trough

timing of meltwater pulse 1a and climate responses to meltwater injections the temporal relationship between meltwater pulse 1a mwp 1a and the climate history of the last deglaciation remains a subject of debate by combining the greenland ice core project d18o ice core record on the new greenland ice core chronology 2005 timescale with the u th dated barbados coral record we conclusively derive that mwp 1a did not coincide with the sharp bolling warming but instead with the abrupt cooling of the older dryas to evaluate whether there is a relationship between meltwater injections north atlantic deep water nadw formation and climate change we present a high resolution record of nadw flow intensity from eirik drift through the last deglaciation it indicates only a relatively minor 200 year weakening of nadw flow coincident with mwp 1a our compilation of records also indicates that during heinrich event 1 and the younger dryas there were no discernible sea level rises and yet these periods were characterized by intense nadw slowdowns shutdowns clearly deepwater formation and climate are not simply controlled by the magnitude or rate of meltwater addition instead our results emphasize that the location of meltwater pulses may be more important with nadw formation being particularly sensitive to surface freshening in the arctic nordic seas

deep water mass source and dynamic associated with rapid climatic variations during the last glacial stage in the north atlantic a multiproxy investigation of the detrital fraction of deep sea sediments in order to investigate north atlantic deep water nadw dynamics and variability during the last glacial stage a very high resolution multiproxy analysis of the detrital fraction of sediments deposited during heinrich event 4 and dansgaard oeschger cycles 8 and 7 has been conducted on three deep sea cores these cores are distributed along the path of the north atlantic deep water from the faeroe shetland channel to the reykjanes ridge and the irminger basin the concentration in fine grained magnetites the ti content and the smectite percentage within the clay minerals show similar and coeval fluctuations at each site and are comparable from one site to the other this is the imprint of the detrital fraction originating from the northern basaltic provinces and transported to the studied sites the average grain size in the fine fraction indicates a transport by deep sea currents therefore the observed fluctuations illustrate changes in the vigor of the bottom currents associated with the nadw with weak currents during cold periods heinrich 4 and stadials and reactivation of the bottom circulation during interstadials

petrophysical and magnetic pore network anisotropy of some cretaceous sandstone from tushka basin egypt summary pore magnetic fabric is a well established technique for the determination of pore elongation and preferred directions for migration of the interstitial fluids this study further exemplify this technique on a set of the nubia sandstones through a comparison with the pore anisotropy obtained from measuring permeability in three orthogonal directions in a gaz permeameter the nubia sandstones are represented in tushka area south egypt by quartz arenite of large porosity 29 40 per cent which was measured on thin sections parallel and perpendicular to the bedding plane and petrophysically by helium pycnometry and ferrofluid injection at 1 bar pressure petrographically there is a detectable difference between the porosity values in the bedding plane and in the perpendicular direction indicating inhomogeneity in the pore space network distribution the petrophysical studies indicate large porosity and permeability values with some differences between the helium and ferrofluid porosity due to presence of micro pore spaces not accessible for the ferrofluid molecules having relatively high diameters and injected at low pressure an overall agreement is observed between the permeability anisotropy and the magnetic grain and pore fabrics magnetic anisotropy measured before and after ferrofluid injection the three fabrics are mainly dominated by a bedding parallel foliation in a few cases maximum permeability appears to be perpendicular to bedding within the bedding plane maximum pore elongation direction from ferrofluid injection is nnw for adindan and kesieba formations and nw for abu simbil formation the maximum pore elongation direction for abu ballas samples showed a direction fluctuating around the e w direction the main fault trends in tushka area the pore fabric of abu ballas formation seems therefore to be structurally controlled while it would be originated from palaeocurrent directions in the other formations

reservoir assessment and quality discrimination of kareem formation using integrated petrophysical data southern gulf of suez egypt abstract the middle miocene kareem formation represents one of the most important reservoirs in the gulf of suez egypt six boreholes locating throughout different structural trends in the southern province of the gulf of suez egypt were selected to study the reservoir properties of the kareem formation the study depends on integrated data of well logs and routine core analysis as well as seismic data the present study is an integrated study aims to study and discriminate the reservoir quality of the kareem sequence using various statistical techniques testerman statistical approach and stratigraphic modified lorenz sml plot were used in reservoir zonation principal component analysis pca and cluster analysis were used to identify the electrofacies distribution within the studied formation the well log data enabled characterizing the reservoir sequence into 6 electrofacies the available core analyses data and core description for the kareem formation 850 feet cored interval in morgan oil field enabled more accurate discrimination for the reservoir sequence into 13 hydraulic flow units 7 of them are potential flow units the studied sequence is differentiated into five lithologic petrophysical facies siltstone dolomitic siltstone dolomitic sandstone sandstone and friable sandstone the sandstone and friable sandstone facies are the best petrophysical facies the dolomite content is the main key factor for reducing the reservoir quality of the studied kareem sequence from the core data a total net pay thickness of 180 feet mostly composed of sandstone with some siltstone intercalations was assigned of fair quality he 14 7 kh 89 1 md so 28 8 reservoir quality index rqi 0 60 m flow zone indicator fzi 3 81 m reservoir potential index rpi 2 with few streaks of good to very good potential however the siltstone samples have less petrophysical potential than the sandstones

geomagnetic field intensity north atlantic deep water circulation and atmospheric δ14c during the last 50 kyr we present simulated records of past changes in the atmospheric 14c for the last 50 kyr due to changes in geomagnetic field intensity and in the strength of the north atlantic deep water nadw a new geomagnetic record was used largely based on the napis 75 record laj et al phil trans r soc london a 358 2000 1009 1025 which has been extended for the 0 20 kyr interval using archeomagnetic and volcanic data past changes of the nadw were derived from a mineral magnetic study of the cores used in the construction of napis 75 two box models of different complexity 4 and 17 boxes were used to simulate the carbon cycle calculated records of 14c are consistent with experimental determinations for the last 24 kyr for older ages the records calculated with variable oceanic circulation conditions reach values as high as 600 with an average of 500 between 20 and 40 kyr with maxima around 21 30 and 38 kyr gisp2 age model while low values are observed prior to 42 kyr although large inconsistencies in experimental data preclude precise comparison the average record simulated with the 17 box model is overall consistent with the icelandic sea record voelker et al radiocarbon 40 1998 517 534 42 2000 437 452 except for the extremely high peak observed in this record at 40 5 kyr on the other hand the results recently reported from a stalagmite recovered from a submerged cave in the bahamas beck et al science 292 2001 2453 2458 are inconsistent with all our model simulations in the 20 45 kyr interval the improved geomagnetic record combined with the new nadw profile allows us to give a modeled evaluation of the relative contribution of these factors to changes in atmospheric 14c the average simulation provides a first order modeled correction for conventional radiocarbon ages older than 25 kyr for which no calibration curve is available as yet

how does the pore throat size control the reservoir quality and oiliness of tight sandstones the case of the lower cretaceous quantou formation in the southern songliao basin china abstract pore throat size is a very crucial factor controlling the reservoir quality and oiliness of tight sandstones which primarily affects rock properties such as permeability and drainage capillary pressure however the wide range of size makes it difficult to understand their distribution characteristics as well as the specific controls on reservoir quality and oiliness in order to better understand about pore throat size distribution petrographic scanning electron microscopy sem pressure controlled mercury injection pmi rate controlled mercury injection rmi quantitative grain fluorescence qgf and environmental scanning electron microscopy esem investigations under laboratory pressure conditions were performed on a suite of tight reservoir from the fourth member of the lower cretaceous quantou formation k 1 q 4 in the southern songliao basin china the sandstones in this study showed different types of pore structures intergranular pores dissolution pores pores within clay aggregates and even some pores related to micro fractures the pore throat sizes vary from nano to micro scale the pmi technique views the pore throat size ranging from 0 001 m to 63 m and revealed that the pore throats with radius larger than 1 0 m are rare and the pore throat size distribution curves show evident fluctuations rmi measurements indicated that the pore size distribution characteristics of the samples with different porosity and permeability values look similar the throat size and pore throat radius ratio distribution curves had however significant differences the overall pore throat size distribution of the k 1 q 4 tight sandstones was obtained with the combination of the pmi and rmi methods the permeability is mainly contributed by a small part of larger pore throats less than 30 and the ratio of the smaller pore throats in the samples increases with decreasing permeability although smaller pore throats have negligible contribution on reservoir flow potential they are very significant for the reservoir storage capacity the pore throats with average radius larger than 1 0 m mainly exist in reservoirs with permeability higher than 0 1md when the permeability is lower than 0 1md the sandstones are mainly dominated by pore throats with average radius from 0 1 m to 1 0 m the ratio of different sized pore throats controls the permeability of the tight sandstone reservoirs in different ways we suggest that splitting or organizing key parameters defining permeability systematically into different classes or functions can enhance the ability of formulating predictive models about permeability in tight sandstone reservoirs the pmi combined with qgf analyses indicate that oil emplacement mainly occurred in the pore throats with radius larger than about 0 25 0 3 m this result is supported by the remnant oil micro occurrence evidence observed by sem and esem

millennial scale fluctuations in north atlantic heat flux during the last 150 000 years abstract surface water and deep ocean palaeoclimate records obtained from north atlantic core su90 03 40 n 32 w exhibit pronounced fluctuations at sub orbital time scales surface temperature variability in the mid latitude atlantic over the last 150 kyr is dominated by forcing at precession 21 kyr and semi precession harmonics 11 kyr abrupt changes in sea surface temperatures show that the northward transport of heat by the north atlantic current was curtailed during ice rafting events sea surface temperatures were about 12 c colder than modern values during the most intense cooling episodes associated with major ice rafting events heinrich events 1 4 6 and 11 and 10 c below modern values during the later part of isotope stage 3 40 30 ka during these cold intervals the north atlantic current was displaced to south of 40 n as the cold meltwaters penetrated southwards into what is now the subtropical ocean these changes in surface ocean heat exchange were most probably allied to a latitudinal migration and increase in zonality of atmospheric circulation patterns concurrent shifts in ird concentration sea surface temperatures and benthic 13 c values provide evidence of coupling between sea surface processes and the deep water circulation and suggest that decreases in surface temperature and salinity during ice rafting events culminated in a significant reorganisation of north atlantic deep water production

radwany formation a new formation name for the early middle eocene carbonate sediments of the offshore october oil field gulf of suez contribution to the eocene sediments in egypt abstract the eocene sediments plays critical role in the evolution and development of the petroleum system in the gulf of suez region where it is representing a self source rock or self reservoir or combination in some areas within the basin microfacies analysis and paleontological studies have not been conducted on these eocene sediments in the area of the october oil field which is mandatory for the formation characteristics assessment therefore sidewall core and ditch cuttings samples that was obtained from october eocene carbonate sediments so far ascribed to the thebes formation was studied in terms of sedimentology paleontology and depositional environment a total of 64 thin sections were analyzed petrographically and three microfacies types recognized both calcareous nanoplankton and foraminifers were examined the study of the eocene carbonate facies in the october field revealed that the succession is composed of pelagic foraminiferal limestone of varied color containing abundant planktonic foraminifers and minor traces of chert three microfacies are distinguished including wackestone of smaller planktonic foraminifera 50 wackestone packstone of planktonic foraminifera 40 and packstone of planktonic foraminifera 10 nannoplankton and foraminifers indicate that the studied succession is of early eocene to middle eocene age microfacies and fossil assemblage of the studied section indicate a pelagic environment and deposition in deep basin at water depths of a few hundred meters finally the current results were compared with data from previous publications on eocene sediments in the region it is revealed that the studied succession provides new data and contribution for the evolution of carbonate platform in the ypresian lutetian age and differs from the typical thebes formation and other eocene formations concerning facies lithology fossil content age and depositional environment therefore we suggest to abandon the term thebes formation for this eocene carbonate succession in the october field and a new lithostratigraphic unit named radwany formation is formally introduced

phase relationships between millennial scale events 64 000 24 000 years ago a core recovered on the iberian margin off southern portugal can be correlated with greenland ice cores using oxygen isotope variability in planktonic foraminifera which closely matches the ice core records of temperature over greenland our age model identifies the base of every interstadial between 64 000 and 24 000 years ago and uses the greenland ice core project grip timescale the oxygen isotope signal in benthic foraminifera on this grip based timescale is quite different from the planktonic record and resembles the temperature record over antarctica when this is synchronized with greenland using the record of methane in the atmospheric air in the polar ice cores we interpret the benthic record as indicating significant fluctuations in ice volume during millennial events and we suggest that antarctic temperature changed as a function of ice volume

determination of electrofacies using wireline logs based on multivariate statistical analysis for the kareem formation gulf of suez egypt beyond the traditional use of well logs electrofacies were introduced to define a set of log responses that can be used to characterize a bed and permitted it to be distinguished from the other rock units classification of a formation into electrofacies can be used in reservoir characterization and discrimination due to the hydrocarbon potential of the kareem formation we used the conventional well logs of four boreholes and a traditional core analyses data from one of these wells to identify electrofacies of the kareem formation in the southern gulf of suez multivariate statistical analyses such as principal component analysis pca and cluster analysis were used for this purpose the multivariate statistical analyses were applied to the raw log data the normalized data and the standardized log data three pc components were obtained from the analyses and six distinctive electrofacies were extracted from the dendrogram plot these electrofacies showed good correlation with the lithofacies that were described from core analysis in addition applying the reservoir zonation of the studied formation using the stratigraphic modified lorenz sml plot and the sum of squared errors sse methods led to its discrimination into four hydraulic flow units the deduced flow units were validated against the available core data

deep ocean overturning then and now knowledge of how fast the deep ocean overturned during the last glacial period is important for understanding how earth s climate could enter such an extremely cold state radiocarbon ages from surface and deep dwelling foraminifera can indirectly measure the overturning rate in their perspective adkins and pasquero discuss new data from the glacial equatorial pacific see report by broecker et al that show that at the time of the last glacial maximum mid depth waters were about as old that is they had spent as much time below the surface as they are today coupled with other records from the deeper ocean the data might help to determine what drives the strength of the overturning circulation in the first place

acquisition of the neodymium isotopic composition of the north atlantic deep water the north atlantic deep water nadw neodymium isotopic composition nd ic is increasingly used in oceanography and paleoceanography to trace large scale circulation and weathering processes notably to investigate past variations of the global thermohaline circulation although the present day nadw nd ic is well characterized at nd 13 5 the acquisition of this isotopic signature in other words the causes of this value has so far been very sparsely documented such an understanding is however fundamental to the interpretation of paleo records nd ic and rare earth element concentrations were measured at 9 stations within the north atlantic subpolar gyre signature cruise summer 1999 the comparison of this data set with our understanding of water mass circulation provides a description of how the three layers constituting the nadw the labrador sea water lsw nd 13 9 0 4 north east atlantic deep water neadw nd 13 2 0 4 and north west atlantic bottom water nwabw nd 14 5 0 4 acquire their nd ic through distinct water mass mixings and lithogenic inputs these different mechanisms acting upon water masses from very diverse sources seem to bring the nd ic of the three nadw layers to values close together and similar to that of the nadw it is suggested that sediment seawater interactions significantly lower the neadw and nwabw nd ic along the south east greenland margin since these interactions do not significantly modify the nd content of these water masses sediment remobilizations leading to the nd ic variations are probably associated with nd removal fluxes from the water mass toward the sediment a process called boundary exchange on the other hand lsw seems to acquire its nd ic from the subpolar mode waters from which it is formed by deep convection and no other mechanism needs to be invoked its unradiogenic signature could ultimately be linked to fresh water runoff from the canadian shield these conclusions should allow more precise interpretations of paleoceanographic nd ic records taking into account the distinct histories of the three nadw layers including distinct water mass mixings and distinct lithogenic inputs

structural framework and tectono stratigraphic evolution of the porcupine seabight basin offshore western ireland abstract the porcupine seabight basin is an intra cratonic rift basin which evolved through recurrent episodes of lithospheric stretching structure contour and isopach maps presented here have been constructed following the interpretation of approx 10 000 km of seismic data together with all the available well data this integrated database has allowed the tectono stratigraphic history of the basin to be traced in detail from its earliest inception the basin was initially formed during the carboniferous when up to 3 7 km of autuno carboniferous sediments were deposited on a caledonian and hercynian structured basement late permian and early mesozoic sediments at least 1 km thick are preserved in contiguous grabens and their presence is also inferred within localized sub basins late liassic crustal doming heralded the onset of the final rifting episode and in the north promoted severe erosion and a rapid discharge of clastic sediments rapid subsidence block faulting and magmatism accompanied the deposition of up to 3 5 km of middle upper jurassic sediments in asymmetrical sub basins the transition from stretching to passive subsidence across the jurassic cretaceous boundary in combination with localized inversion abrupt eustatic and environmental changes generated a basin wide unconformity the rift drift transition in the adjacent proto atlantic rift system is recorded in the porcupine seabight basin by voluminous volcanism and a late lower cretaceous unconformity cretaceous sediments are strongly transgressive and up to 6 km thick these were superseded during the early palaeogene by several regressive transgressive cycles before the arrival of an upper slope fauna in the mid middle eocene cenozoic sediments are up to 4 km thick and record the interplay between 1 the location of the basin pn the pyrenean alpine foreland superimposed on the periphery of the icelandic plume and 2 its development as a marginal atlantic shelf region the former is thought to be responsible for eo oligocene faulting subsidence and igneous activity in the north east part of the basin and the latter for unconformities and a change in the style of sedimentation principally due to oceanic circulation changes

petroleum geology and potential hydrocarbon plays in the gulf of suez rift basin egypt the gulf of suez in egypt has a north northwest south southeast orientation and is located at the junction of the african and arabian plates where it separates the northeast african continent from the sinai peninsula it has excellent hydrocarbon potential with the prospective sedimentary basin area measuring approximately 19 000 km 2 and it is considered as the most prolific oil province rift basin in africa and the middle east this basin contains more than 80 oil fields with reserves ranging from 1350 to less than 1 million bbl in reservoirs of precambrian to quaternary age the lithostratigraphic units in the gulf of suez can be subdivided into three megasequences a prerift succession pre miocene or paleozoic eocene a synrift succession oligocene miocene and a postrift succession post miocene or pliocene holocene these units vary in lithology thickness areal distribution depositional environment and hydrocarbon importance geological and geophysical data show that the northern and central gulf of suez consist of several narrow elongated depositional troughs whereas the southern part is dominated by a tilt block terrane containing numerous offset linear highs major prerift and synrift source rocks have potential to yield oil and or gas and are mature enough in the deep kitchens to generate hydrocarbons geochemical parameters sterane distribution and biomarker correlations are consistent with oils generated from marine source rocks oils in the gulf of suez were sourced from potential source rock intervals in the prerift succession that are typically oil prone type i and in places oil and gas prone type ii or are composites of more than one type multiple types i ii or iii for oil prone oil and gas prone or gas prone respectively the reservoirs can be classified into prerift reservoirs such as the precambrian granitic rocks paleozoic cretaceous nubian sandstones upper cretaceous nezzazat sandstones and the fractured eocene thebes limestone and synrift reservoirs such the miocene sandstones and carbonates of the nukhul rudeis kareem and belayim formations and the sandstones of south gharib zeit and

the greenland ice sheet project 2 depth age scale methods and results the greenland ice sheet project 2 gisp2 depth age scale is presented based on a multiparameter continuous count approach to a depth of 2800 m using a systematic combination of parameters that have never been used to this extent before the ice at 2800 m is dated at 110 000 years b p with an estimated error ranging from 1 to 10 in the top 2500 m of the core and averaging 20 between 2500 and 2800 m parameters used to date the core include visual stratigraphy oxygen isotopic ratios of the ice electrical conductivity measurements laser light scattering from dust volcanic signals and major ion chemistry gisp2 ages for major climatic events agree with independent ages based on varve chronologies calibrated radiocarbon dates and other techniques within the combined uncertainties good agreement also is obtained with greenland ice core project ice core dates and with the specmap marine timescale after correlation through the 18 o of o 2 although the core is deformed below 2800 m and the continuity of the record is unclear we attempted to date this section of the core on the basis of the laser light scattering of dust in the ice

the petroleum geology of ireland s offshore basins introduction during the past few years a number of factors have combined to create renewed petroleum exploration interest in the late palaeozoic cenozoic sedimentary basins that virtually surround ireland these factors include recent discoveries in contiguous uk offshore basins the perceived attractiveness of the irish licensing terms the apparent stabilization of the international oil price and recent advances in drilling and deep water production technologies combined with the realization by many oil companies that the irish basins are only lightly explored

miocene biofacies development and geological history of the gulf of suez egypt abstract miocene sediments of the gulf of suez were deposited in a rapidly subsiding rift which became active during late oligocene and early pliocene tectonic episodes complex lithological variations associated with the variable submarine structure commonly preclude detailed correlation of drilled subsurface successions thick middle to late miocene evaporites and their geometry obscure seismic interpretation of prospective sub evaporitic early and middle miocene sequences the thick miocene sediments are believed to have significantly furnished the source as well as the reservoirs and seals for the oil discovered in the gulf of suez over four billion barrels of oil have been established as recoverable reserves in miocene reservoirs a new gulf wide detailed correlation scheme is established based upon a series of newly defined microfaunal assemblage zones these zones are based on holistic analysis of microfauna utilizing planktonic and benthonic foraminifera diatoms otoliths and pteropods dating by planktonic foraminifera and calcareous nannofossils indicates the zones are isochronous vertical and lateral variations in assemblage characteristics have been identified mapped and are concluded to be the results of vertical and lateral differences in salinity water depth water clarity lithological variation and oxygen availability the correlative applicability of this scheme within the gulf of suez provides potential for it to serve as a reference for drilled sequences in the red sea where thicker evaporite sequences make sub evaporitic stratigraphic correlation even more difficult owing to the greater seismic attenuation isochronous palaeoenvironmental variations are detected utilizing the zonation scheme both within the gulf of suez and the red sea region which will assist in the correlation and mapping of stratigraphic sequences of hydrocabon potential detection confirmation and the degree of displacement of faults is also improved by the application of the scheme

temporal stability of the neodymium isotope signature of the holocene to glacial north atlantic the neodymium isotopic composition of marine precipitates is increasingly recognized as a powerful tool for identifying changes in ocean circulation and mixing on million year to millennial timescales unlike nutrient proxies such as 13 c or cd ca nd isotopes are not thought to be altered in any significant way by biological processes and thus they can serve as a quasi conservative water mass tracer however the application of nd isotopes in understanding the role of thermohaline circulation in rapid climate change is currently hindered by the lack of direct constraints on the signature of the north atlantic end member through time here we present the first results of nd isotopes measured in u th dated deep sea corals from the new england seamounts in the northwest atlantic ocean our data are consistent with the conclusion that the nd isotopic composition of north atlantic deep and intermediate water has remained nearly constant through the last glacial cycle the results address long standing concerns that there may have been significant changes in the nd isotopic composition of the north atlantic end member during this interval and substantiate the applicability of this novel tracer on millennial timescales for paleoceanography research

comparative sequence stratigraphy and structural styles of the slyne trough and hebrides basin the slyne trough to the west of ireland is divided into three sections north central and south the south and central sub basins are separated by a seismic dead zone along the line of the clew bay disturbance the central and north sub basins are separated by a zone transferring the fault bounding the main basin from the western margin in the central sub basin to the eastern margin in the north sub basin five stratigraphic sequences from the slyne trough which span the rhaetian to middle jurassic are recognized in the 27 13 1 well and they are compared to the equivalent sequences in the hebrides basin the late jurassic hebridean sequences are expected in the deeper parts of the central slyne trough the slyne trough and hebrides basin sediments are mainly tectonically controlled although major eustatic events in the early toarcian and late bathonian are recognized

rapid changes in the mechanism of ocean convection during the last glacial period high amplitude rapid climate fluctuations are common features of glacial times the prominent changes in air temperature recorded in the greenland ice cores1 2 are coherent with shifts in the magnitude of the northward heat flux carried by the north atlantic surface ocean3 4 changes in the ocean s thermohaline circulation are a key component in many explanations of this climate flickering5 here we use stable isotope and other sedimentological data to reveal specific oceanic reorganizations during these rapid climate change events deep water was generated more or less continuously in the nordic seas during the latter part of the last glacial period 60 to 10 thousand years ago but by two different mechanisms the deep water formation occurred by convection in the open ocean during warmer periods interstadials but during colder phases stadials a freshening of the surface ocean reduced or stopped open ocean convection and deep water formation was instead driven by brine release during sea ice freezing these shifting magnitudes and modes nested within the overall continuity of deep water formation were probably important for the structuring and rapidity of the prevailing climate changes

millennial scale iceberg discharges in the irminger basin during the last glacial period relationship with the heinrich events and environmental settings high resolution records of coarse lithic content and oxygen isotope have been obtained in a piston core from the irminger basin the last glacial period is characterized by numerous periods of increased iceberg discharges originating partly from iceland and corresponding to millennial scale instabilities of the coastal ice sheets and ice shelves in the nordic area a comparison with midlatitude sediment cores shows that ice rafted material corresponding to the heinrich events was deposited synchronously from 40 to 60 n there are thus two oscillating systems every 5 10 kyr massive iceberg armadas are released from large continental ice caps whereas more frequent instabilities of the coastal ice sheets in the high latitude regions occur every 1 2 3 8 kyr at the time of the heinrich events the synchroneity of the response from all the northern hemisphere ice sheets attests the existence of strong interactions between the two systems

millennial scale propagation of atlantic deep waters to the glacial southern ocean the compilation of changes in the magnetic properties at various sites distributed along the path of the deepwater mass in north atlantic shows large amplitude short term fluctuations reflecting changes in the strength of the north atlantic deep water nadw these changes which suggest a two mode deep glacial circulation dynamic are perfectly concurrent with air temperature changes over greenland they also share a similar pattern with those reported in the nd isotope ratios from the deep cape basin during the same time period greenland interstadials were accompanied by increased flow speed of nadw and relatively more nadw reaching the southern ocean while during greenland stadials and heinrich events both the north atlantic flow speed of nadw and its presence in the south atlantic were reduced it is demonstrated that both proxies are tracing the same water mass and their reliability for monitoring changes in the deepwater circulation is therefore clearly established after using the climatically independent geomagnetic assisted stratigraphy to put the northern and southern hemisphere records on the same age scale the south atlantic record appears to lag changes in north atlantic flow speeds by approximately 860 220 years during the most prominent and best defined cycles interstadials 12 and 8 although future work is needed this significant offset provides a first observation and tentative quantification of the time needed for glacial northern component water to mix downward and to flow from the north to the south atlantic

surface and deep ocean variability in the northern sargasso sea during marine isotope stage 3 new geochemical proxy data from bermuda rise piston cores reveal ocean and climate conditions in the northern sargasso sea during marine isotope stage 3 using 18o on the planktonic foraminifer globigerinoides ruber we can correlate explicitly with every stadial interstadial change in greenland ice between 32 and 58 ka these data suggest repetitive changes of 4 c in the annual average sea surface temperature sst with maximum cooling comparable to or greater than sst during glacial maximum conditions the extent of sst depression is about the same for typical stadial events and for heinrich events 4 and 5 which we have identified on the bermuda rise by traces of ice rafting benthic foraminiferal 13c decreases during every stadial event consistent with reduced production of the deepest component of north atlantic deep water and shoaling of its interface with antarctic bottom water this interpretation is supported by benthic cd ca data from the climate cycle associated with interstadial 8

changes in sea surface hydrology associated with heinrich event 4 in the north atlantic ocean between 40 and 60 n abstract the changes in distribution of sea surface temperature and salinity in the north atlantic between 40 and 60 n were reconstructed for the time interval between 40 and 30 kyr bp which includes the large iceberg discharge event associated with the deposition of heinrich layer 4 we found that the meltwater input during deposition of heinrich layer 4 resulted in a 1 2 kyr temperature decrease of about 2 c and a salinity decrease in the range of 1 5 3 5 between 40 and 50 n sites above 50 n did not experience significant salinity variations a much larger area was affected by the reduction in sea surface temperature the amplitude of the sea surface temperature shift was however much smaller than the atmospheric temperature changes over greenland at gisp and grip sites

late permian to early mesozoic rifting and sedimentation offshore nw ireland abstract a late permian triassic and early lias rift succession up to 1 km thick is revealed from offshore nw ireland sediments are preserved in deep narrow grabens from the donegal basin in the north southwestwards through the erris and slyne troughs to a series of newly defined basins collectively forming the north porcupine basin with a further structure the galway graben on the porcupine bank this line of basins superimposed on a caledonoid fractured basement underwent a complex structural evolution but since the late permian they developed primarily as a wrench modified rift system during the latest lias crustal doming west of britain may have produced a regional angular unconformity and created a source for thick middle jurassic alluvial clastics deposited in the main porcupine basin to the south early tertiary transpression of the north porcupine area caused late stage fragmentation of the basin the rift succession consists of continental red beds bounded by two dateable transgressive intervals these intervals provide valuable stratigraphic control for constraining the timing and scale of seaways propagating across the fracturing pangean supercontinent from the late permian to the early jurassic evidence is also presented for an episode of syn rift volcanism temporally unique to western britain and ireland